EP4093751A1

EP4093751A1 - Chimeric polypeptides

Info

Publication number: EP4093751A1
Application number: EP21706431.0A
Authority: EP
Inventors: Marc Lajoie; Scott BOYKEN; Robert LANGAN; Howell MOFFETT
Original assignee: Outpace Bio Inc
Current assignee: Outpace Bio Inc
Priority date: 2020-01-22
Filing date: 2021-01-22
Publication date: 2022-11-30
Also published as: WO2021151001A1

Abstract

The preset disclosure provides chimeric polypeptide comprising a cage polypeptide comprising a degron, wherein the degron is sequestered or caged to the C-terminus of the latch region. Upon activation by a key polypeptide, the degron becomes active. The degron can be ubiquitinated and be marked for degradation, together with any biologically active molecule attached to the chimeric polypeptide. The chimeric polymeric of the present disclosure can be incorporated, for example, to chimeric antigen receptors (CAR). Accordingly, in response to the administration of a key polypeptide or endogenous expression of a key polypeptide mediated, for example, by an inducible promoter, the amount of CAR expressed on the surface of an immune cell can be modulated.

Description

CHIMERIC POLYPEPTIDES

SEQUENCE LISTING

[0001] The instant application contains a Sequence Listing which has been submitted electronically in ASCII format and is hereby incorporated by reference in its entirety. Said ASCII copy, created on January 21, 2021, is named 016-TNP019BPCT_SL.txt and is 136,365 bytes in size.

FIELD OF THE DISCLOSURE

[0002] The present disclosure is related to chimeric polypeptides comprising a sequestered degron, which can be used to modulate protein expression in cell and gene therapies, e.g. , the chimeric polypeptides comprising a sequestered degron could be used to regulate expression or activity of a CAR, cytokine receptor, costimulatory/coinhibitory receptor, or transcription factor on or in T-cells, and therefore be used in cancer immunotherapy.

BACKGROUND OF THE DISCLOSURE [0003] Cancer immunotherapy relies on getting T cells — the immune system’s primary killers of infected and diseased cells — to attack and kill tumor cells. However, there is an important stumbling block for immunotherapy: T cells’ ability to kill can fade, a phenomenon often referred to as exhaustion. Ex v/vo-expanded Tumor-Infiltrating Lymphocytes (TILs) therapy, chimeric antigen receptor (CAR) T cell therapy, and T cell receptor-engineered (TCR) T cell therapy are treatments that make use of functionally active T cells isolated from patients and require highly functional T cells in order to be effective. These T cells are engineered and expanded ex vivo to recognize specific antigens on target cancer cells. T cell therapies have not been effective at curing solid cancers because the T cells lose their ability to proliferate or kill over time. It may be possible to engineer T cells to maintain their ability to proliferate and kill by overcoming the mechanisms that cause T cells to fade. One mechanism that drives loss of T cell function is too much signaling through the CAR/TCR (Lynn, R.C., Weber, E.W., Sotillo, E. etal, Nature 576, 293-300 (2019) doi:10.1038/s41586-019-1805-z).

[0004] The clinical responses of these CAR T cell therapies in hematologic malignancies have been encouraging. Nonetheless, they have demonstrated substantial morbidity and occasionally mortality resulting from toxicity. The most commonly observed CAR T-cell- associated toxicity is cytokine release syndrome. CRS typically occurs within the first week following CAR T-cell infusion. Peak CAR T-cell levels and serum interleukin-6 (IL-6) levels in patients have strongly correlated with the severity of CRS after CAR T-cell therapy. In some instances, the CRS can be very severe. Therefore, especially for cell and gene therapies, there is also a need to develop off switches capable of down-regulating or ablating unwanted signaling.

BRIEF SUMMARY

[0005] The present disclosure provides a polynucleotide encoding a chimeric polypeptide which comprises a cage polypeptide comprising: (i) a structural region comprising an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 13 (Cage 13); SEQ ID NO: 14 (Cage 14); SEQ ID NO: 15 (Cage 15); SEQ ID NO: 16 (Cage 16); SEQ ID NO: 17 (Cage 17); SEQ ID NO: 18 (Cage 18); SEQ ID NO: 1 (Cage 1); SEQ ID NO: 2 (Cage 2); SEQ ID NO: 3 (Cage 3); SEQ ID NO: 4 (Cage 4); SEQ ID NO: 5 (Cage 5); SEQ ID NO: 6 (Cage 6); SEQ ID NO: 7 (Cage 7); SEQ ID NO: 8 (Cage 8); SEQ ID NO: 9 (Cage 9); SEQ ID NO: 10 (Cage 10); SEQ ID NO: 11 (Cage 11); or SEQ ID NO: 12 (Cage 12), and (ii) a latch region comprising a degron peptide comprising the amino acid sequence of CGL, wherein the latch region is capable of binding to the structural region.

[0006] In some aspects, the degron peptide comprises YCGL (SEQ ID NO: 136), TYCGL (SEQ ID NO: 137), VTYCGL (SEQ ID NO: 138), RVTYCGL (SEQ ID NO: 139), IRVTYCGL (SEQ ID NO: 140), LIR VTYCGL (SEQ ID NO: 141), or VLIR VTYCGL (SEQ ID NO: 142). In some aspects, the degron peptide comprises an amino acid sequence at least about 70%, at least about 80%, at least about 90%, or about 100% identical to VLIR VTYCGL (SEQ ID NO: 142).

[0007] In some aspects, the structural region comprises any one of the amino acid sequences as set forth in SEQ ID NO: 13 (Cage 13); SEQ ID NO: 14 (Cage 14); SEQ ID NO: 15 (Cage 15); SEQ ID NO: 16 (Cage 16); SEQ ID NO: 17 (Cage 17); SEQ ID NO: 18 (Cage 18); SEQ ID NO: 1 (Cage 1); SEQ ID NO: 2 (Cage 2); SEQ ID NO: 3 (Cage 3); SEQ ID NO: 4 (Cage 4); SEQ ID NO: 5 (Cage 5); SEQ ID NO: 6 (Cage 6); SEQ ID NO: 7 (Cage 7); SEQ ID NO: 8 (Cage 8); SEQ ID NO: 9 (Cage 9); SEQ ID NO: 10 (Cage 10); SEQ ID NO: 11 (Cage 11); or SEQ ID NO: 12 (Cage 12). [0008] In some aspects, the degron peptide is linked to the C-terminus of the latch region of the cage polypeptide. In some aspects, the degron peptide is linked to the C-terminus of the amino acid sequence set forth in SEQ ID NO: 13 (Cage 13). In some aspects, the degron peptide is linked to the C-terminus of the amino acid sequence set forth in SEQ ID NO: 14 (Cage 14). In some aspects, the degron peptide is linked to the C-terminus of the amino acid sequence set forth in SEQ ID NO: 15 (Cage 15). In some aspects, the degron peptide is linked to the C- terminus of the amino acid sequence set forth in SEQ ID NO: 16 (Cage 16). In some aspects, the degron peptide is linked to the C-terminus of the amino acid sequence set forth in SEQ ID NO: 17 (Cage 17). In some aspects, the degron peptide is linked to the C-terminus of the amino acid sequence set forth in SEQ ID NO: 18 (Cage 18). In some aspects, the degron peptide is linked to the C-terminus of the amino acid sequence set forth in SEQ ID NO: 1 (Cage 1). In some aspects, the degron peptide is linked to the C-terminus of the amino acid sequence set forth in SEQ ID NO: 2 (Cage 2). In some aspects, the degron peptide is linked to the C-terminus of the amino acid sequence set forth in SEQ ID NO: 3 (Cage 3). In some aspects, the degron peptide is linked to the C-terminus of the amino acid sequence set forth in SEQ ID NO: 4 (Cage 4). In some aspects, the degron peptide is linked to the C-terminus of the amino acid sequence set forth in SEQ ID NO: 5 (Cage 5). In some aspects, the degron peptide is linked to the C- terminus of the amino acid sequence set forth in SEQ ID NO: 6 (Cage 6). In some aspects, the degron peptide is linked to the C-terminus of the amino acid sequence set forth in SEQ ID NO: 7 (Cage 7). In some aspects, the degron peptide is linked to the C-terminus of the amino acid sequence set forth in SEQ ID NO: 8 (Cage 8). In some aspects, the degron peptide is linked to the C-terminus of the amino acid sequence set forth in SEQ ID NO: 9 (Cage 9). In some aspects, the degron peptide is linked to the C-terminus of the amino acid sequence set forth in SEQ ID NO: 10 (Cage 10). In some aspects, the degron peptide is linked to the C-terminus of the amino acid sequence set forth in SEQ ID NO: 11 (Cage 11). In some aspects, the degron peptide is linked to the C-terminus of the amino acid sequence set forth in SEQ ID NO: 12 (Cage 12).

[0009] In some aspects, the chimeric polypeptide comprises an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 13 (Cage 13). In some aspects, the chimeric polypeptide comprises an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 14 (Cage 14). In some aspects, the chimeric polypeptide comprises an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 15 (Cage 15). In some aspects, the chimeric polypeptide comprises an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 15 (Cage 17). In some aspects, the chimeric polypeptide comprises an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 16 (Cage 16). In some aspects, the chimeric polypeptide comprises an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 18 (Cage 18). In some aspects, the chimeric polypeptide comprises an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 1 (Cage 1). In some aspects, the chimeric polypeptide comprises an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 2 (Cage 2). In some aspects, the chimeric polypeptide comprises an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 3 (Cage 3). In some aspects, the chimeric polypeptide comprises an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 4 (Cage 4). In some aspects, the chimeric polypeptide comprises an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 5 (Cage 5). In some aspects, the chimeric polypeptide comprises an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 6 (Cage 6). In some aspects, the chimeric polypeptide comprises an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 7 (Cage 7). In some aspects, the chimeric polypeptide comprises an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 8 (Cage 8). In some aspects, the chimeric polypeptide comprises an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 9 (Cage 9). In some aspects, the chimeric polypeptide comprises an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 10 (Cage 10). In some aspects, the chimeric polypeptide comprises an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 11 (Cage 11). In some aspects, the chimeric polypeptide comprises an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 12 (Cage 12).

[0010] In some aspects, the chimeric polypeptide further comprises a signaling domain. In certain aspects, the signaling domain comprises a domain derived from CD3zeta, FcR gamma, FcR beta, CD3 gamma, CD3 delta, CD3 epsilon, CD5, CD22, CD79a, CD79b, or CD66d.

[0011] In some aspects, the chimeric polypeptide further comprises a co-stimulatory domain. In certain aspects, the co-stimulatory domain comprises a domain derived from 2B4, HVEM, ICOS, LAG3, DAP 10, DAP 12, CD27, CD28, 4-1BB (CD137), 0X40 (CD134), CD30, CD40, ICOS (CD278), glucocorticoid-induced tumor necrosis factor receptor (GITR), lymphocyte function-associated antigen- 1 (LFA-1), CD2, CD7, LIGHT, NKG2C, or B7-H3.

[0012] In some aspects, the chimeric polypeptide further comprises an antigen binding domain. In some aspects, the antigen-binding domain comprises an antibody or an antigen binding fragment thereof that specifically binds to an epitope on a tumor antigen. In some aspects, the antigen binding domain is an Ig NAR, a Fab, a Fab’, a F(ab)’2, a F(ab)’3, an Fv, a single chain variable fragment (scFv), a bis-scFv, a (scFv)2, a minibody, a diabody, a triabody, a tetrabody, an intrabody, a disulfide stabilized Fv protein (dsFv), a unibody, or a nanobody. In some aspects, the antigen binding domain specifically binds to CD 19, TRAC, TCRP, BCMA, CLL-1, CS1, CD38, CD19, TSHR, CD123, CD22, CD30, CD70, CD171, CD33, EGFRvIII, GD2, GD3, Tn Ag, PSMA, ROR1, ROR2, GPC1, GPC2, FLT3, FAP, TAG72, CD44v6, CEA, EPCAM, B7H3, KIT, IL- 13Ra2, Mesothelin, IL-l lRa, PSCA, PRSS21, VEGFR2, LewisY, CD24, PDGFR-beta, SSEA-4, CD20, Folate receptor alpha, ERBB2 (Her2/neu), MUC1, MUC16, EGFR, NCAM, Prostase, PAP, ELF2M, Ephrin B2, IGF-I receptor, CAIX, LMP2, gplOO, bcr-abl, tyrosinase, EphA2, Fucosyl GM1, sLe, GM3, TGS5, HMWMAA, o-acetyl-GD2, Folate receptor beta, TEM1/CD248, TEM7R, CLDN6, GPRC5D, CXORF61, CD97, CD 179a, ALK, Poly sialic acid, PLAC1, GloboH, NY-BR-1, UPK2, HAVCR1, ADRB3, PANX3, GPR20, LY6K, OR51E2, TARP, WT1, NY-ESO-1, L AGE-1 a, MAGE-A1, legumain, HPV E6,E7, MAGE Al, ETV6-AML, sperm protein 17, XAGE1, Tie 2, MAD-CT-1, MAD-CT- 2, Fos-related antigen 1, p53, p53 mutant, prostein, survivin and telomerase, PCTA-l/Galectin 8, MelanA/MARTl, Ras mutant, hTERT, sarcoma translocation breakpoints, ML-IAP, ERG (TMPRSS2 ETS fusion gene), NA17, PAX3, Androgen receptor, CyclinBl, MYCN, RhoC, TRP-2, CYP1B1, BORIS, SART3, PAX5, OY-TES1, LCK, AKAP- 4, SSX2, RAGE-1, human telomerase reverse transcriptase, RU1, RU2, intestinal carboxyl esterase, mut hsp70-2, CD79a, CD79b, CD72, LAIR1, FCAR, LILRA2, CD300LF, CLEC12A, BST2, EMR2, LY75, GPC3, FCRL5, IGLL1, or any combinations thereof.

[0013] In some aspects, the chimeric polypeptide comprises a chimeric antigen receptor (CAR). In some aspects, the CAR is designed as a standard CAR, a split CAR, an off-switch CAR, an on-switch CAR, a first-generation CAR, a second-generation CAR, a third-generation CAR, or a fourth-generation CAR.

[0014] In some aspects, the chimeric polypeptide further comprises a transmembrane domain.

[0015] In some aspects, the polynucleotide disclosed herein encodes a chimeric antigen receptor comprising: (i) the chimeric polypeptide of the present disclosure; (ii) an antigen binding domain that binds to an epitope on a tumor antigen expressed on a target cell; and (iii) a transmembrane done.

[0016] In some aspects, the CAR disclosed herein further comprises a CAR spacer between the antigen binding domain and the transmembrane domain.

[0017] In some aspects, the chimeric polypeptide comprises a T cell receptor. In some aspects, the chimeric polypeptide induces an IFNy and/or IL-2 expression in a cell. In some aspects, the chimeric polypeptide is capable of being degraded through a ubiquitin dependent pathway. In some aspects, the chimeric polypeptide is capable of being degraded when in contact with a key polypeptide. [0018] In some aspects, a polynucleotide disclosed herein is a DNA molecule, a RNA molecule, or any combination thereof.

[0019] Also disclosed herein is a polynucleotide set comprising the polynucleotide disclosed herein and a second polynucleotide. In some aspects, the second polynucleotide encode a key polypeptide that is capable of inhibiting binding of the latch region to the structural region of the chimeric polypeptide when the key polypeptide comes in contact with the chimeric polypeptide.

[0020] In some aspects, the key polypeptide comprises an amino acid sequence having at least about 70%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, or about 100% sequence identity to the sequence as set forth in SEQ ID NO: 19 (Key 1), SEQ ID NO: 20 (Key 2), SEQ ID NO: 21 (Key 3), SEQ ID NO: 22 (Key 4), SEQ ID NO: 23 (Key 5), SEQ ID NO: 24 (Key 6), SEQ ID NO: 25 (Key 7), SEQ ID NO: 26 (Key 8), SEQ ID NO: 27 (Key 9), SEQ ID NO: 28 (Key 10), SEQ ID NO: 29 (Key 11), SEQ ID NO: 30 (Key 12), SEQ ID NO: 31 (Key 13 or Key 14), SEQ ID NO: 32 (Key 15), SEQ ID NO: 33 (Key 16), SEQ ID NO: 34 (Key 17), or SEQ ID NO: 35 (Key 18), wherein the key polypeptide is capable of binding to the structural region of the chimeric polypeptide.

[0021] In some aspects, the chimeric polypeptide comprises an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 1 (Cage 1), and the key polypeptide comprises an amino acid sequence having at least about 70%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, or about 100% sequence identity to the sequence as set forth in SEQ ID NO: 19 (Key 1).

[0022] In some aspects, the chimeric polypeptide comprises an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 2 (Cage 2), and the key polypeptide comprises an amino acid sequence having at least about 70%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, or about 100% sequence identity to the sequence as set forth in SEQ ID NO: 20 (Key 2).

[0023] In some aspects, the chimeric polypeptide comprises an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 3 (Cage 3), and the key polypeptide comprises an amino acid sequence having at least about 70%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, or about 100% sequence identity to the sequence as set forth in SEQ ID NO: 21 (Key 3).

[0024] In some aspects, the chimeric polypeptide comprises an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 4 (Cage 4), and the key polypeptide comprises an amino acid sequence having at least about 70%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, or about 100% sequence identity to the sequence as set forth in SEQ ID NO: 22 (Key 4).

[0025] In some aspects, the chimeric polypeptide comprises an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 5 (Cage 5), and the key polypeptide comprises an amino acid sequence having at least about 70%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, or about 100% sequence identity to the sequence as set forth in SEQ ID NO: 23 (Key 5).

[0026] In some aspects, the chimeric polypeptide comprises an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 6 (Cage 6), and the key polypeptide comprises an amino acid sequence having at least about 70%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, or about 100% sequence identity to the sequence as set forth in SEQ ID NO: 24 (Key 6).

[0027] In some aspects, the chimeric polypeptide comprises an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 7 (Cage 7), and the key polypeptide comprises an amino acid sequence having at least about 70%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, or about 100% sequence identity to the sequence as set forth in SEQ ID NO: 25 (Key 7).

[0028] In some aspects, the chimeric polypeptide comprises an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 8 (Cage 8), and the key polypeptide comprises an amino acid sequence having at least about 70%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, or about 100% sequence identity to the sequence as set forth in SEQ ID NO: 26 (Key 8).

[0029] In some aspects, the chimeric polypeptide comprises an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 9 (Cage 9), and the key polypeptide comprises an amino acid sequence having at least about 70%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, or about 100% sequence identity to the sequence as set forth in SEQ ID NO: 27 (Key 9).

[0030] In some aspects, the chimeric polypeptide comprises an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 10 (Cage 10), and the key polypeptide comprises an amino acid sequence having at least about 70%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, or about 100% sequence identity to the sequence as set forth in SEQ ID NO: 28 (Key 10).

[0031] In some aspects, the chimeric polypeptide comprises an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 11 (Cage 11), and the key polypeptide comprises an amino acid sequence having at least about 70%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, or about 100% sequence identity to the sequence as set forth in SEQ ID NO: 29 (Key 11).

[0032] In some aspects, the chimeric polypeptide comprises an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 12 (Cage 12), and the key polypeptide comprises an amino acid sequence having at least about 70%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, or about 100% sequence identity to the sequence as set forth in SEQ ID NO: 30 (Key 12).

[0033] In some aspects, the chimeric polypeptide comprises an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 13 (Cage 13) or SEQ ID NO: 14 (Cage 14), and the key polypeptide comprises an amino acid sequence having at least about 70%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, or about 100% sequence identity to the sequence as set forth in SEQ ID NO: 31 (Key 13 or Key 14).

[0034] In some aspects, the chimeric polypeptide comprises an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 15 (Cage 15), and the key polypeptide comprises an amino acid sequence having at least about 70%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, or about 100% sequence identity to the sequence as set forth in SEQ ID NO: 32 (Key 15).

[0035] In some aspects, the chimeric polypeptide comprises an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 16 (Cage 16), and the key polypeptide comprises an amino acid sequence having at least about 70%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, or about 100% sequence identity to the sequence as set forth in SEQ ID NO: 33 (Key 16).

[0036] In some aspects, the chimeric polypeptide comprises an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 17 (Cage 17), and the key polypeptide comprises an amino acid sequence having at least about 70%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, or about 100% sequence identity to the sequence as set forth in SEQ ID NO: 34 (Key 17).

[0037] In some aspects, the chimeric polypeptide comprises an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 18 (Cage 18), and the key polypeptide comprises an amino acid sequence having at least about 70%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, or about 100% sequence identity to the sequence as set forth in SEQ ID NO: 35 (Key 18).

[0038] Present disclosure provides a vector comprising any of the polynucleotides, polynucleotide sets disclosed herein operably linked to one or more regulatory elements. In some aspects, the vector is a viral vector, a mammalian vector, or a bacterial vector. In certain aspects, the vector is a retroviral vector. In some aspects, the vector is selected from the group consisting of an adenoviral vector, a lentivirus, a Sendai virus vector, a baculoviral vector, an Epstein Barr viral vector, a papovaviral vector, a vaccinia viral vector, a herpes simplex viral vector, a hybrid vector, and an adeno associated virus (AAV) vector. In some aspects, the vector is a lentivirus.

[0039] In some aspects, the polynucleotide encoding the chimeric polypeptide and the second polynucleotide encoding the key polypeptide are on the same vector. In some aspects, the polynucleotide encoding the chimeric polypeptide and the second polynucleotide encoding the key polypeptide are on different vectors. In some aspects, wherein the second polynucleotide encoding the key polypeptide is operably linked to an inducible promoter.

[0040] Also disclosed herein is a chimeric polypeptide encoded by a polynucleotide or a vector disclosed herein.

[0041] Provided herein is a chimeric polypeptide comprising a cage polypeptide comprising: (i) a structural region which comprises an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO 13 (Cage 13), SEQ ID NO: 14 (Cage 14), SEQ ID NO: 15 (Cage 15), SEQ ID NO: 16 (Cage 16), SEQ ID NO: 17 (Cage 17), SEQ ID NO: 18 (Cage 18), SEQ ID NO: 1 (Cage 1), SEQ ID NO: 2 (Cage 2), SEQ ID NO: 3 (Cage 3), SEQ ID NO: 4 (Cage 4), SEQ ID NO: 5 (Cage 5), SEQ ID NO: 6 (Cage 6), SEQ ID NO: 7 (Cage 7), SEQ ID NO: 8 (Cage 8), SEQ ID NO: 9 (Cage 9), SEQ ID NO: 10 (Cage 10), SEQ ID NO: 11 (Cage 11), or SEQ ID NO: 12 (Cage 12), and (ii) a latch region comprising a degron peptide comprising the amino acid sequence of CGL, wherein the latch region is capable of binding to a structural region.

[0042] In some aspects, the structural region comprises any one of the amino acid sequences as set forth in SEQ ID NO: 13 (Cage 13); SEQ ID NO: 14 (Cage 14); SEQ ID NO: 15 (Cage 15); SEQ ID NO: 16 (Cage 16); SEQ ID NO: 17 (Cage 17); SEQ ID NO: 18 (Cage 18); SEQ ID NO: 1 (Cage 1); SEQ ID NO: 2 (Cage 2); SEQ ID NO: 3 (Cage 3); SEQ ID NO: 4 (Cage 4); SEQ ID NO: 5 (Cage 5); SEQ ID NO: 6 (Cage 6); SEQ ID NO: 7 (Cage 7); SEQ ID NO: 8 (Cage 8); SEQ ID NO: 9 (Cage 9); SEQ ID NO: 10 (Cage 10); SEQ ID NO: 11 (Cage 11); or SEQ ID NO: 12 (Cage 12). In some aspects, the degron peptide comprises YCGL (SEQ ID NO: 136), TYCGL (SEQ ID NO: 137), VTYCGL (SEQ ID NO: 138), RVTYCGL (SEQ ID NO: 139), IR VTYCGL (SEQ ID NO: 140), LIR VTYCGL (SEQ ID NO: 141), or VLIRVTYCGL (SEQ ID NO: 142). In certain aspects, the degron peptide is linked to the C- terminus of the latch region of the cage polypeptide.

[0043] Disclosed herein is a chimeric polypeptide comprising an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 1 (Cage 1). Disclosed herein is a chimeric polypeptide comprising an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 2 (Cage 2). Disclosed herein is a chimeric polypeptide comprising an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 3 (Cage 3). Disclosed herein is a chimeric polypeptide comprising an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 4 (Cage 4). Disclosed herein is a chimeric polypeptide comprising an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 5 (Cage 5). Disclosed herein is a chimeric polypeptide comprising an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 6 (Cage 6). Disclosed herein is a chimeric polypeptide comprising an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 7 (Cage 7). Disclosed herein is a chimeric polypeptide comprising an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 8 (Cage 8). Disclosed herein is a chimeric polypeptide comprising an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 9 (Cage 9). Disclosed herein is a chimeric polypeptide comprising an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 10 (Cage 10). Disclosed herein is a chimeric polypeptide comprising an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 11 (Cage 11). Disclosed herein is a chimeric polypeptide comprising an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 12 (Cage 12). Disclosed herein is a chimeric polypeptide comprising an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 13 (Cage 13). Disclosed herein is a chimeric polypeptide comprising an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 14 (Cage 14). Disclosed herein is a chimeric polypeptide comprising an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 15 (Cage 15). Disclosed herein is a chimeric polypeptide comprising an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 16 (Cage 16). Disclosed herein is a chimeric polypeptide comprising an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 17 (Cage 17). Disclosed herein is a chimeric polypeptide comprising an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 18 (Cage 18).

[0044] In some aspects, the chimeric polypeptide comprises a chimeric antigen receptor.

[0045] Present disclosure further provides a cell comprising a polynucleotide, polynucleotide set, vector, or chimeric polypeptide of the present disclosure. Also provided herein is a cell genetically modified to express a CAR, comprising the polynucleotide, polynucleotide set, vector, or chimeric polypeptide disclosed herein. In some aspects, the cell is a T cell, a natural killer (NK) cell, a natural killer T (NKT) cell, or an ILC cell. [0046] Present disclosure provides a composition comprising a polynucleotide, polynucleotide set, vector, or chimeric polypeptide, or the cell of the present disclosure. In certain aspects, the composition is for treating a subject in need of a CAR therapy.

[0047] Provided herein is a kit comprising a polynucleotide, polynucleotide set, vector, or chimeric polypeptide, or the cell of the present disclosure.

[0048] Also provided herein is a method of making an engineered cell comprising transfecting the polynucleotide, polynucleotide set, vector disclosed herein in a cell. In certain aspects, the chimeric polypeptide is expressed in the cell. In some aspects, the method further comprises administering the cell to a subject in need thereof. In some aspects, the method further comprises administering a key polypeptide or an inducer that is capable of expressing a key polypeptide.

[0049] Provided herein is a method of controlling a T cell-mediated immune response in a subject in need thereof comprising administering an effective amount of the cell disclosed herein.

[0050] Provided herein is a method of stimulating a T cell-mediated immune response to a target cell population or tissue in a subject, comprising administering an effective amount of the cell disclosed herein to the subject.

[0051 ] Provided herein is a method of providing an anti -tumor immunity in a subj ect in need thereof, the method comprising administering an effective amount of the cell disclosed herein to the subject.

[0052] Provided herein is a method of treating cancer in a subject in need thereof comprising administering an effective amount of the cell of the present disclosure to the subject. In some aspects, the cell is a T cell. In some aspects, the cell is an autologous T cell. In certain aspects, the method further comprises administering a key polypeptide. In some aspects, the method further comprises administering an inducer of a key polypeptide.

[0053] Disclosed herein is a use of the polynucleotide, polynucleotide set, vector, chimeric polypeptide, cell, composition, kit disclosed herein for the manufacture of a medicament for treating cancer in a subject in need thereof. BRIEF DESCRIPTION OF THE DRAWINGS/FIGURES [0054] FIG. 1 is a schematic representation of a cell-intrinsic feedback control system to mitigate exhaustion, e.g ., via degron-induced reduction of CAR surface expression as disclosed in the present application.

[0055] FIG. 2 is a schematic representation of ubiquitin-dependent and ubiquitin- independent membrane protein regulation. Stability of most membrane proteins is determined by regulated trafficking of proteins to endocytic vesicles, followed by fusion with lysosomal bodies and protein degradation. Mono or poly-Ubiquitination is one driver of this process. Recruitment of trafficking proteins can also lead to membrane protein internalization and degradation. Degradation would result in a reduction of membrane protein surface expression.

[0056] FIG. 3A is a schematic representation of two cage polypeptides. The 3plusl cage polypeptide is a four helix bundle comprising three structural region helices and a latch helix. The 2plusl cage polypeptide is a three helix bundle comprising two structural region helices and a latch helix.

[0057] FIG. 3B is a schematic representation of an exemplary cage polypeptide with a CGL degron motif. As shown, the cage polypeptide (i.e., 3plusl configuration) is made up of three alpha-helices (“SR”) and a C-terminal latch helix (“L”), with the CGL degron motif (“D”) positioned at the C-terminal end of the latch region.

[0058] FIG. 3C is a schematic representation of the mechanism of action of a chimeric polypeptide of the present disclosure. As described herein, the degron motif (“D”) is attached to the C-terminal end of the latch region (“L”). In the absence of a key polypeptide, the latch region remains bound to the structural region and thereby, sequestering the degron in the cage polypeptide (see diagram I). Upon binding of a key polypeptide (“K”) to the cage polypeptide (see diagram II), the latch region is displaced and the degron becomes activated, resulting in protein degradation (e.g., via recruitment of ubiquitin ligases and subsequent ubiquitination of cage amino acids) (see diagram III).

[0059] FIG. 4 is a schematic representation of an exemplary chimeric antigen receptor complex comprising a chimeric peptide of the present disclosure at the C-terminus.

[0060] FIG. 5A provides a comparison of the ability of different degron motifs to downmodulate ROR1 CAR expression on primary T cells. The degron motifs tested included the following: (i) GG, (ii) RHWRGQEG (SEQ ID NO: 160), (iii) RWGRRG (SEQ ID NO: 161), (iv) TMAAGRAPGK (SEQ ID NO: 162), (v) VLIRVTYCGL (SEQ ID NO: 142), and (vi) EIAGLLGG (SEQ ID NO: 163). As shown in FIG. 4, each of the degron motifs were incorporated at the C-terminus of the CAR construct. CAR expression on the T cells is shown as mean fluorescence intensity of bound recombinant RORl-Fc in transduced cells measured using flow cytometry. Transduced cells were identified by the expression of the truncated CD 19 marker, expression of which was linked to CAR expression via a 2a cleavable peptide. Expression is shown relative to cells transduced with a matching CAR construct lacking a regulatory motif as a positive control, and to untransduced cells negative for truncated CD 19 as a negative control.

[0061 ] FIG. 5B provides representative flow cytometry plots showing the surface expression of ROR1 CARs (x-axis) versus truncated CD 19 marker (y-axis) on (i) untransduced primary T cells (i.e., negative control) (“untransduced”), (ii) primary T cells transduced with a matching CAR construct lacking a regulatory motif (i.e., positive control) (“tCD19-p2a-CAR”), and (iii) primary T cells transduced with the ROR1 CARs comprising VLIRVTYCGL (SEQ ID NO: 142) at the C-terminal end of the latch region (“tCD19-p2a-CAR-CGL”).

[0062] FIG. 5C shows ineffective membrane protein degradation by C-terminal fusion of the mouse ornithine decarboxylase enzyme (cODC) to the truncated epidermal growth factor receptor (EGFRt). Shown are representative histogram plots of EGFRt surface expression on (i) untransduced SupTl cells (dashed line), (ii) SupTl cells transduced with ROR1 CAR p2a linked to the truncated EGFR membrane protein, (solid line, gated on ROR1 CAR+ cells), or (iii) SupTl cells transduced with ROR1 CAR p2a-linked to a truncated EGFR membrane protein with a flexible glycine-serine linker followed by the cODC (CAR-p2a-EGFRt- G4S_cODC; filled gray histogram, gated on ROR1 CAR + cells) (full sequence = SGGGGSGGGGSLPMSCAQESGMDRHPAACASARINV; SEQ ID NO: 164).

[0063] FIG. 6 shows the ability of LockR proteins to cage the bioactive CGL motif and prevent CGL-mediated reductions in surface expression of a linked CAR construct. The different chimeric polypeptides tested had the CGL degron motif attached to the C-terminus of the latch region of the following LockR proteins (i.e., cage polypeptides): (i) Cage 14 (SEQ ID NO: 14), (ii) Cage 16 (SEQ ID NO: 16), (iii) Cage 4 (SEQ ID NO: 4), and (iv) Cage 12 (SEQ ID NO: 12). CAR expression on the T cells is shown as mean fluorescence intensity of bound recombinant RORl-Fc in lentivirally transduced cells measured using flow cytometry. Transduced cells were identified by the expression of the truncated CD 19 marker, expression of which was linked to CAR expression via a 2a cleavable peptide. Expression is shown relative to cells transduced with a matching CAR construct lacking a regulatory motif as a positive control, and to untransduced cells as a negative control.

[0064] FIG. 7 shows that C-terminal fusion of lockR designs containing the CGL degron motif does not affect antigen recognition by the CAR construct in the SupTl transformed T cell line. SupTl cells were transduced with Rorl -specific CAR construct (“CAR”) or Rorl- specific CAR constructs linked at the C-terminus to the following 3 independent lockR designs containing the CGL degron motif (“CAR-lockR-CGL”): Cage 14 (SEQ ID NO: 14), Cage 16 (SEQ ID NO: 16), and Cage 12 (SEQ ID NO: 12). Expression of the chimeric antigen receptor (as measured by the mean fluorescence intensity of bound recombinant RORl-Fc protein; y- axis) and the activation marker CD69 (as measured by the mean fluorescence intensity of expression; x-axis) on transduced Suptl cells were determined by flow cytometry.

[0065] FIG. 8 shows that C-terminal fusion of lockR designs containing the CGL degron motif does not affect antigen recognition by the CAR construct in primary human T cells. The primary human T cells were transduced with the Rorl -specific CAR construct (“CAR”) or Rorl -specific CAR constructs linked at the C terminus to 3 independent lockR designs containing the CGL degron motif (i.e., those described in FIG. 7). “+ Target Cells” corresponds to transduced T cells stimulated with the Rorl -specific target cells. “Unstimulated” corresponds to transduced T cells that were not stimulated with the target cells. Expression of the activation marker CD69 (left graph; shown as the mean fluorescence intensity of expression) and the activation/exhaustion marker PD1 (right graph; shown as the mean fluorescence intensity of expression) on transduced primary T cells were determined by flow cytometry.

[0066] FIGs. 9A and 9B show the functional activity of primary human T cells transduced with ROR1 CAR constructs comprising C-terminal fusion of lockR designs containing the CGL degron motif. The primary human T cells were transduced with ROR1 CAR constructs linked at the C-terminal end to one of the following lockR designs containing the CGL degron motif: (i) Cage 9 (SEQ ID NO: 9), (ii) Cage 10 (SEQ ID NO: 10), (iii) Cage 2 (SEQ ID NO: 2), and (iv) Cage 18 (SEQ ID NO: 18). Primary human T cells transduced with ROR1 CAR construct without a degron motif (“CAR”) were used as control. FIG. 9A shows the cytolytic activity (as % killing) of the transduced primary T cells on the y-axis, and mean fluorescence intensity of ROR1 CAR expression on the transduced T cells. FIG. 9B shows IFN-g (black bars) and IL-2 (white bars) production by the transduced primary T cells in response to target antigen stimulation.

DETAILED DESCRIPTION

[0067] The present disclosure is directed to chimeric polypeptides that can be used to control CAR expression, e.g. , to mitigate CAR T-cell exhaustion by reducing CAR surface expression. See FIG. 1. Regulation of CAR expression could also serve to match CAR expression to tumor burden, minimizing immune activation mediated toxicity under high tumor burden, while maximizing effective recognition of low-expressing escape mutations or small amounts of residual disease. Reduction of CAR surface expression can be accomplished, for example, by increasing CAR degradation via ubiquitin-dependent membrane protein internalization and degradation. See FIG. 2.

[0068] The chimeric polypeptides disclosed herein comprise a cage polypeptide that includes a sequestered degron, which can be activated with a key polypeptide. The cage polypeptide and the key polypeptide can be two separate polypeptide chains.

[0069] The cage polypeptide is a helix bundle and comprises a structural region and a latch region (see FIG. 3). The latch region of the cage polypeptide comprises the “sequestered” (i.e., caged) degron (e.g., linked to the C-terminus of the latch). The key polypeptide displaces the latch polypeptide through competitive intermolecular binding that induces a conformational change, exposing the degron and thereby, activating the system. In turn, the exposed degron can be ubiquitinated by an ubiquitin ligase, leading to the degradation of the chimeric polypeptide, including any bioactive molecule fused to the chimeric polypeptide, e.g, a chimeric antigen receptor (CAR) or a T cell receptor (TCR) fused or conjugated to the cage polypeptide.

[0070] Accordingly, in some aspects, the chimeric polypeptides disclosed herein can be incorporated into CARs, TCRs, or other engineered receptors and thereby, modulate the expression of CARs, TCRs, or other engineered receptors on immune cells. In some aspects, by modulating the expression of CARs, TCRs, or other engineered receptors on immune cells, it is possible to prevent, mitigate, modulate, or reverse immune cell exhaustion in immune therapy. Such effect can be accomplished, for example, via the administration of the key polypeptide ( e.g ., in a format capable of being transported through cell membranes) or via endogenous expression of the key polypeptide in response to an inducing agent.

[0071] Before the present disclosure is described in greater detail, it is to be understood that this disclosure is not limited to the particular compositions or process steps described, as such can, of course, vary. As will be apparent to those of skill in the art upon reading this disclosure, each of the individual aspects described and illustrated herein has discrete components and features which can be readily separated from or combined with the features of any of the other several aspects without departing from the scope or spirit of the present disclosure. Any recited method can be carried out in the order of events recited or in any other order which is logically possible.

[0072] The headings provided herein are not limitations of the various aspects of the disclosure, which can be defined by reference to the specification as a whole. It is also to be understood that the terminology used herein is for the purpose of describing particular aspects only, and is not intended to be limiting, since the scope of the present disclosure will be limited only by the appended claims.

I. Terms

[0073] In order that the present disclosure can be more readily understood, certain terms are first defined. As used in this application, except as otherwise expressly provided herein, each of the following terms shall have the meaning set forth below. Additional definitions are set forth throughout the application.

[0074] Throughout this disclosure, the term “a” or “an” entity refers to one or more of that entity; for example, “a chimeric polypeptide,” is understood to represent one or more chimeric polypeptides. As such, the terms “a” (or “an”), “one or more,” and “at least one” can be used interchangeably herein.

[0075] Furthermore, “and/or” where used herein is to be taken as specific disclosure of each of the two specified features or components with or without the other. Thus, the term “and/or” as used in a phrase such as “A and/or B” herein is intended to include “A and B,” “A or B,” “A” (alone), and “B” (alone). Likewise, the term “and/or” as used in a phrase such as “A, B, and/or C” is intended to encompass each of the following aspects: A, B, and C; A, B, or C; A or C; A or B; B or C; A and C; A and B; B and C; A (alone); B (alone); and C (alone).

[0076] It is understood that wherever aspects are described herein with the language “comprising,” otherwise analogous aspects described in terms of “consisting of’ and/or “consisting essentially of’ are also provided.

[0077] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure is related. For example, the Concise Dictionary of Biomedicine and Molecular Biology, Juo, Pei- Show, 2nd ed., 2002, CRC Press; The Dictionary of Cell and Molecular Biology, 3rd ed., 1999, Academic Press; and the Oxford Dictionary of Biochemistry and Molecular Biology, Revised, 2000, Oxford University Press, provide one of skill with a general dictionary of many of the terms used in this disclosure.

[0078] Units, prefixes, and symbols are denoted in their Systeme International de Unites (SI) accepted form. Numeric ranges are inclusive of the numbers defining the range.

[0079] Abbreviations used herein are defined throughout the present disclosure. Various aspects of the disclosure are described in further detail in the following subsections.

[0080] The terms “about” or “comprising essentially of’ refer to a value or composition that is within an acceptable error range for the particular value or composition as determined by one of ordinary skill in the art, which will depend in part on how the value or composition is measured or determined, i.e., the limitations of the measurement system. For example, “about” or “comprising essentially of’ can mean within 1 or more than 1 standard deviation per the practice in the art. Alternatively, “about” or “comprising essentially of’ can mean a range of up to 10%. Furthermore, particularly with respect to biological systems or processes, the terms can mean up to an order of magnitude or up to 5-fold of a value. When particular values or compositions are provided in the application and claims, unless otherwise stated, the meaning of “about” or “comprising essentially of’ should be assumed to be within an acceptable error range for that particular value or composition.

[0081 ] As used herein, the term “approximately,” as applied to one or more values of interest, refers to a value that is similar to a stated reference value. In certain aspects, the term “approximately” refers to a range of values that fall within 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, or less in either direction (greater than or less than) of the stated reference value unless otherwise stated or otherwise evident from the context (except where such number would exceed 100% of a possible value).

[0082] As described herein, any concentration range, percentage range, ratio range or integer range is to be understood to include the value of any integer within the recited range and, when appropriate, fractions thereof (such as one tenth and one hundredth of an integer), unless otherwise indicated.

[0083] As used herein, “administering” refers to the physical introduction of a therapeutic agent or a composition comprising a therapeutic agent to a subject, using any of the various methods and delivery systems known to those skilled in the art. The different routes of administration for a therapeutic agent described herein ( e.g ., a CAR comprising a chimeric polypeptide disclosed herein) include intravenous, intraperitoneal, intramuscular, subcutaneous, spinal or other parenteral routes of administration, for example by injection or infusion.

[0084] The phrase “parenteral administration” as used herein means modes of administration other than enteral and topical administration, usually by injection, and includes, without limitation, intravenous, intraperitoneal, intramuscular, intraarterial, intrathecal, intralymphatic, intralesional, intracapsular, intraorbital, intracardiac, intradermal, transtracheal, intratracheal, pulmonary, subcutaneous, subcuticular, intraarticular, subcapsular, subarachnoid, intraventricle, intravitreal, epidural, and intrastemal injection and infusion, as well as in vivo electroporation.

[0085] Alternatively, a therapeutic agent described herein (e.g., a CAR comprising a chimeric polypeptide disclosed herein) can be administered via a non-parenteral route, such as a topical, epidermal, or mucosal route of administration, for example, intranasally, orally, vaginally, rectally, sublingually, or topically. Administering can also be performed, for example, once, a plurality of times, and/or over one or more extended periods.

[0086] As used herein, the term “antigen” refers to any natural or synthetic immunogenic substance, such as a protein, peptide, or hapten. As used herein, the term “cognate antigen” refers to an antigen which an immune cell (e.g, T cell) recognizes and thereby, induces the activation of the immune cell ( e.g ., triggering intracellular signals that induce effector functions, such as cytokine production, and/or for proliferation of the cell).

[0087] Nucleotides are referred to by their commonly accepted single-letter codes. Unless otherwise indicated, nucleic acids are written left to right in 5' to 3' orientation. Nucleotides are referred to herein by their commonly known one-letter symbols recommended by the IUPAC-IUB Biochemical Nomenclature Commission. Accordingly, A represents adenine, C represents cytosine, G represents guanine, T represents thymine, U represents uracil.

[0088] It is to be understood that in the disclosed sequences T and U are interchangeable depending on whether the sequence is a DNA or an RNA. For example, gRNA spacer sequences are presented as DNAs (A/T/C/G) in the present disclosure, whereas the gRNA chimeric frames are presented as RNAs (A/U/C/G).

[0089] Amino acids are referred to herein by either their commonly known three letter symbols or by the one-letter symbols recommended by the IUPAC-IUB Biochemical Nomenclature Commission. Unless otherwise indicated, amino acid sequences are written left to right in amino to carboxy orientation.

[0090] A “polypeptide” refers to a chain comprising at least two consecutively linked amino acid residues, with no upper limit on the length of the chain. One or more amino acid residues in the protein can contain a modification such as, but not limited to, glycosylation, phosphorylation or disulfide bond formation. A “protein” can comprise one or more polypeptides. Unless otherwise specified, the terms “protein” and “polypeptide” can be used interchangeably.

[0091] The term “nucleic acid,” as used herein, is intended to include DNA molecules and RNA molecules. A nucleic acid molecule can be single- stranded or double- stranded, and can be cDNA.

[0092] The term “polynucleotide” as used herein refer to polymers of nucleotides of any length, including ribonucleotides, deoxyribonucleotides, analogs thereof, or mixtures thereof. This term refers to the primary structure of the molecule. Thus, the term includes triple-, double- and single-stranded deoxyribonucleic acid (“DNA”), as well as triple-, double- and single-stranded ribonucleic acid (“RNA”). It also includes modified, for example by alkylation, and/or by capping, and unmodified forms of the polynucleotide. More particularly, the term “polynucleotide” includes polydeoxyribonucleotides (containing 2-deoxy-D-ribose), polyribonucleotides (containing D-ribose), including mRNAs and gRNAs, whether spliced or unspliced, any other type of polynucleotide which is an N- or C-glycoside of a purine or pyrimidine base, and other polymers containing normucleotidic backbones, for example, polyamide ( e.g ., peptide nucleic acids “PNAs”) and polymorpholino polymers, and other synthetic sequence-specific nucleic acid polymers providing that the polymers contain nucleobases in a configuration which allows for base pairing and base stacking, such as is found in DNA and RNA.

[0093] The term “vector,” as used herein, is intended to refer to a nucleic acid molecule capable of transporting another nucleic acid to which it has been linked. One type of vector is a “plasmid,” which refers to a circular double stranded DNA loop into which additional DNA segments can be ligated. Another type of vector is a viral vector, wherein additional DNA segments can be ligated into the viral genome. Certain vectors are capable of autonomous replication in a host cell into which they are introduced (e.g., bacterial vectors having a bacterial origin of replication and episomal mammalian vectors). Other vectors (e.g, non- episomal mammalian vectors) can be integrated into the genome of a host cell upon introduction into the host cell, and thereby are replicated along with the host genome. Moreover, certain vectors are capable of directing the expression of genes to which they are operatively linked. Such vectors are referred to herein as “recombinant expression vectors” (or simply, “expression vectors”).

[0094] Expression vectors of utility in recombinant DNA techniques are often in the form of plasmids. In the present specification, “plasmid” and “vector” can be used interchangeably as the plasmid is the most commonly used form of vector. However, also included are other forms of expression vectors, such as viral vectors (e.g, replication defective retroviruses, adenoviruses and adeno-associated viruses), which may serve equivalent functions.

[0095] A “cancer” refers a broad group of various diseases characterized by the uncontrolled growth of abnormal cells in the body. Unregulated cell division and growth results in the formation of malignant tumors that invade neighboring tissues and can also metastasize to distant parts of the body through the lymphatic system or bloodstream. “Cancer” as used herein may, for example, include primary, metastatic and recurrent cancers. [0096] As used herein, the term “immune response” refers to a biological response within a vertebrate against foreign agents, which response protects the organism against these agents and diseases caused by them. An immune response is mediated by the action of a cell of the immune system ( e.g ., a T lymphocyte, B lymphocyte, natural killer (NK) cell, macrophage, eosinophil, mast cell, dendritic cell or neutrophil) and soluble macromolecules produced by any of these cells or the liver (including antibodies, cytokines, and complement) that results in selective targeting, binding to, damage to, destruction of, and/or elimination from the vertebrate’s body of invading pathogens, cells or tissues infected with pathogens, cancerous or other abnormal cells, or, in cases of autoimmunity or pathological inflammation, normal human cells or tissues. An immune reaction includes, e.g., activation or inhibition of a T cell, e.g, an effector T cell or a Th cell, such as a CD4⁺ or CD8⁺ T cell, or the inhibition of a Treg cell. As used herein, the term “T cell” and “T lymphocytes” are interchangeable and refer to any lymphocytes produced or processed by the thymus gland. In some aspects, a T cell is a CD4+ T cell. In some aspects, a T cell is a CD 8+ T cell. In some aspects, a T cell is a NKT cell.

[0097] As used herein, the term “anti-tumor immune response” refers to an immune response against a tumor antigen.

[0098] An increased ability to stimulate an immune response or the immune system, can result from an enhanced agonist activity of T cell costimulatory receptors and/or an enhanced antagonist activity of inhibitory receptors. An increased ability to stimulate an immune response or the immune system can be reflected by a fold increase of the EC50 or maximal level of activity in an assay that measures an immune response, e.g, an assay that measures changes in cytokine or chemokine release, cytolytic activity (determined directly on target cells or indirectly via detecting CD 107a or granzymes) and proliferation. In some aspects, the ability to stimulate an immune response or the immune system activity can be enhanced, e.g, by at least about 10%, at least about 15%, at least about 20%, at least about 25%, at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, or at least about 100%. In some aspects, the ability to stimulate an immune response or the immune system activity can be enhanced, e.g, at least about 1.2 fold, at least about 1.4 fold, at least about 1.6 fold, at least about 1.8 fold, at least about 2 fold, at least about 3 fold, at least about 4 fold, at least about 5 fold, at least about 6 fold, at least about 7 fold, at least about 8 fold, at least about 9 fold, at least about 10 fold, or more.

[0099] A “subject” includes any human or nonhuman animal. The term “nonhuman animal” includes, but is not limited to, vertebrates such as nonhuman primates, sheep, dogs, and rodents such as mice, rats and guinea pigs. In some aspects, the subject is a human. The terms “subject” and “patient” are used interchangeably herein. As used herein, the phrase “subject in need thereof’ includes subjects, such as mammalian subjects, that would benefit, e.g ., from administration of a composition comprising a chimeric polypeptide of the present disclosure such as a CAR or a TCR, e.g, to control tumor growth.

[0100] The term “therapeutically effective amount” or “therapeutically effective dosage” refers to an amount of an agent (e.g, a polynucleotide encoding a CAR or TCR comprising a chimeric polypeptide disclosed herein) that provides the desired biological, therapeutic, and/or prophylactic result. That result can be reduction, amelioration, palliation, lessening, delaying, and/or alleviation of one or more of the signs, symptoms, or causes of a disease, or any other desired alteration of a biological system. In reference to solid tumors, an effective amount comprises an amount sufficient to cause a tumor to shrink and/or to decrease the growth rate of the tumor (such as to suppress tumor growth) or to prevent or delay other unwanted cell proliferation. In some aspects, an effective amount is an amount sufficient to delay tumor development. In some aspects, an effective amount is an amount sufficient to prevent or delay tumor recurrence. An effective amount can be administered in one or more administrations.

[0101] The effective amount of the composition (e.g, a CAR or TCR comprising a chimeric polypeptide disclosed herein or a cell comprising such a CAR or TCR) can, for example, (i) reduce the number of cancer cells; (ii) reduce tumor size; (iii) inhibit, retard, slow to some extent and can stop cancer cell infiltration into peripheral organs; (iv) inhibit (i.e., slow to some extent and can stop tumor metastasis; (v) inhibit tumor growth; (vi) prevent or delay occurrence and/or recurrence of tumor; and/or (vii) relieve to some extent one or more of the symptoms associated with the cancer.

[0102] In some aspects, a “therapeutically effective amount” is the amount of a composition disclosed herein (e.g, a CAR or TCR comprising a chimeric polypeptide of the present disclosure or a cell comprising such a CAR or TCR), which is clinically proven to effect a significant decrease in cancer or slowing of progression (regression) of cancer, such as an advanced solid tumor. The ability of a therapeutic agent of the present disclosure ( e.g ., a CAR or TCR comprising a chimeric polypeptide disclosed herein or a cell comprising such a CAR or TCR) to promote disease regression can be evaluated using a variety of methods known to the skilled practitioner, such as in human subjects during clinical trials, in animal model systems predictive of efficacy in humans, or by assaying the activity of the agent in in vitro assays.

[0103] As used herein, the term “standard of care” refers to a treatment that is accepted by medical experts as a proper treatment for a certain type of disease and that is widely used by healthcare professionals. The term can be used interchangeable with any of the following terms: “best practice,” “standard medical care,” and “standard therapy.”

[0104] By way of example, an “anti-cancer agent” promotes cancer regression in a subject or prevents further tumor growth. In certain aspects, a therapeutically effective amount of the anti-cancer agent (e.g., a CAR or TCR comprising a chimeric polypeptide disclosed herein or a cell comprising such a CAR or TCR) promotes cancer regression to the point of eliminating the cancer.

[0105] “Promoting cancer regression” means that administering an effective amount of a composition disclosed herein (e.g, a CAR or TCR comprising a chimeric polypeptide disclosed herein or a cell comprising such a CAR or TCR), alone or in combination with an anti-neoplastic agent (e.g, a small molecule chemotherapeutic agent), results in a reduction in tumor growth or size, necrosis of the tumor, a decrease in severity of at least one disease symptom, an increase in frequency and duration of disease symptom-free periods, or a prevention of impairment or disability due to the disease affliction.

[0106] The terms “effective” and “effectiveness” with regard to a treatment includes both pharmacological effectiveness and physiological safety. Pharmacological effectiveness refers to the ability of a composition disclosed herein (e.g, a CAR or TCR comprising a chimeric polypeptide disclosed herein or a cell comprising such a CAR or TCR) to promote cancer regression in the patient. Physiological safety refers to the level of toxicity, or other adverse physiological effects at the cellular, organ and/or organism level (adverse effects) resulting from administration of the anti-cancer agent.

[0107] As used herein, the term “immune checkpoint inhibitor” refers to molecules that totally or partially reduce, inhibit, interfere with or modulate one or more checkpoint proteins. Checkpoint proteins regulate T-cell activation or function. Numerous checkpoint proteins are known, such as CTLA-4 and its ligands CD80 and CD86; and PD-1 with its ligands PD-L1 and PD-L2. Pardoll, D.M., Nat Rev Cancer 12(4):252-64 (2012). These proteins are responsible for co-stimulatory or inhibitory interactions of T-cell responses. Immune checkpoint proteins regulate and maintain self-tolerance and the duration and amplitude of physiological immune responses. Immune checkpoint inhibitors include antibodies or are derived from antibodies.

[0108] As used herein, the terms “elevated concentrations” or “elevated levels” and grammatical variants thereof refer to above-normal levels of a substance compared to appropriate controls ( e.g ., healthy tissue or cells).

[0109] The terms “chimeric antigen receptor” and “CAR,” as used herein, refer to a recombinant fusion protein that has an antigen-specific extracellular domain coupled to an intracellular domain that directs the cell to perform a specialized function upon binding of an antigen to the extracellular domain. In some aspects, a chimeric antigen receptor disclosed herein comprise a chimeric polypeptide of the present disclosure (e.g., at the C-terminus of the chimeric antigen receptor).

[0110] The terms “artificial T cell receptor,” “chimeric T-cell receptor,” and “chimeric immunoreceptor” can each be used interchangeably herein with the term “chimeric antigen receptor.” Chimeric antigen receptors are distinguished from other antigen binding agents by their ability to both bind MHC -independent antigen and transduce activation signals via their intracellular domain.

[0111] The antigen-specific extracellular domain of a chimeric antigen receptor recognizes and specifically binds an antigen, typically a surface-expressed antigen of a malignancy. An antigen-specific extracellular domain specifically binds an antigen when, for example, it binds the antigen with an affinity constant or affinity of interaction (K_D) between about 0.1 pM to about 10 mM, for example, about 0.1 pM to about 1 mM or about 0.1 pM to about 100 nM. Methods for determining the affinity of interaction are known in the art. An antigen-specific extracellular domain suitable for use in a CAR of the present disclosure can be any antigen binding polypeptide, a wide variety of which are known in the art. In some aspects, the antigen binding domain is a single chain Fv (scFv). Other antibody-based recognition domains (cAb VHH (camelid antibody variable domains) and humanized versions thereof, IgNAR VH (shark antibody variable domains) and humanized versions thereof, sdAb VH (single domain antibody variable domains) and “camelized” antibody variable domains are suitable for use. In some aspects, T cell receptor (TCR) based recognition domains, such as single chain TCR (scTv, single chain two-domain TCR containing V. alpha. V.beta.) are also suitable for use.

[0112] A chimeric antigen receptor disclosed herein ( e.g ., comprising a chimeric polypeptide) can also include an intracellular domain that provides an intracellular signal to the cell (expressing the CAR) upon antigen binding to the antigen-specific extracellular domain. In some aspects, the intracellular signaling domain of a CAR is responsible for activation of at least one of the effector functions of the T cell in which the chimeric receptor is expressed.

[0113] The term “intracellular domain” refers to the portion of a CAR that transduces the effector function signal upon binding of an antigen to the extracellular domain and directs the T cell to perform a specialized function. Non-limiting examples of suitable intracellular domains include the zeta chain of the T-cell receptor or any of its homologs (e.g., eta, delta, gamma, or epsilon), MB 1 chain, 829, Fc RIII, Fc RI, and combinations of signaling molecules, such as CD3.zeta. and CD28, CD27, 4-1BB, DAP-10, 0X40, and combinations thereof, as well as other similar molecules and fragments. Intracellular signaling portions of other members of the families of activating proteins can be used, such as FcyRIII and FceRI. While usually the entire intracellular domain will be employed, in many cases it will not be necessary to use the entire intracellular polypeptide. To the extent that a truncated portion of the intracellular signaling domain can find use, such truncated portion can be used in place of the intact chain as long as it still transduces the effector function signal. The term intracellular domain is thus meant to include any truncated portion of the intracellular domain sufficient to transduce the effector function signal. Typically, the antigen-specific extracellular domain is linked to the intracellular domain of the chimeric antigen receptor by a transmembrane domain. A transmembrane domain traverses the cell membrane, anchors the CAR to the T cell surface, and connects the extracellular domain to the intracellular signaling domain, thus impacting expression of the CAR on the T cell surface. Chimeric antigen receptors can also further comprise one or more costimulatory domain and/or one or more spacer. A costimulatory domain is derived from the intracellular signaling domains of costimulatory proteins that enhance cytokine production, proliferation, cytotoxicity, and/or persistence in vivo. [0114] A “peptide hinge” or “spacer” connects the antigen-specific extracellular domain to the transmembrane domain. The transmembrane domain is fused to the costimulatory domain, optionally a costimulatory domain is fused to a second costimulatory domain, and the costimulatory domain is fused to a signaling domain, not limited to Oϋ3z. For example, inclusion of a spacer domain between the antigen-specific extracellular domain and the transmembrane domain, and between multiple scFvs in the case of tandem CAR, can affect flexibility of the antigen-binding domain(s) and thereby CAR function. Suitable transmembrane domains, costimulatory domains, and spacers are known in the art.

[0115] As used herein, the terms “ug” and “uM” are used interchangeably with “pg” and “mM,” respectively.

[0116] “Coding sequence” or “encoding nucleic acid” as used herein means the nucleic acids (RNA or DNA molecule) that comprise a nucleotide sequence which encodes a protein, e.g., CAR or TCR comprising a chimeric polypeptide disclosed herein, or a key polypeptide. The coding sequence can further include initiation and termination signals operably linked to regulatory elements including a promoter and polyadenylation signal capable of directing expression in the cells of an individual or mammal to which the nucleic acid is administered. The coding sequence may be codon optimized.

[0117] “Complement” or “complementary” as used herein refers to Watson-Crick (e.g, A- T/U and C-G) or Hoogsteen base pairing between nucleotides or nucleotide analogs of nucleic acid molecules. “Complementarity” refers to a property shared between two nucleic acid sequences, such that when they are aligned antiparallel to each other, the nucleotide bases at each position will be complementary.

[0118] The term “amino acid substitution” refers to replacing an amino acid residue present in a parent or reference sequence (e.g, a wild type sequence) with another amino acid residue. An amino acid can be substituted in a parent or reference sequence (e.g, a wild type polypeptide sequence), for example, via chemical peptide synthesis or through recombinant methods known in the art. Accordingly, a reference to a “substitution at position X” refers to the substitution of an amino acid present at position X with an alternative amino acid residue. In some aspects, substitution patterns can be described according to the schema AnY, wherein A is the single letter code corresponding to the amino acid naturally or originally present at position n, and Y is the substituting amino acid residue. In other aspects, substitution patterns can be described according to the schema An(YZ), wherein A is the single letter code corresponding to the amino acid residue substituting the amino acid naturally or originally present at position n, and Y and Z are alternative substituting amino acid residues that can replace A.

[0119] As used herein, the term “conserved” refers to nucleotides or amino acid residues of a polynucleotide sequence or polypeptide sequence, respectively, that are those that occur unaltered in the same position of two or more sequences being compared. Nucleotides or amino acids that are relatively conserved are those that are conserved amongst more related sequences than nucleotides or amino acids appearing elsewhere in the sequences.

[0120] In some aspects, two or more sequences are said to be “completely conserved” or “identical” if they are 100% identical to one another. In some aspects, two or more sequences are said to be “highly conserved” if they are at least about 70% identical, at least about 75% identical, at least about 80% identical, at least about 85% identical, at least about 90% identical, or at least about 95% identical to one another. In some aspects, two or more sequences are said to be “highly conserved” if they are about 70% identical, about 75% identical, about 80% identical, about 85% identical, about 90% identical, about 95% identical, about 98% identical, or about 99% identical to one another. In some aspects, two or more sequences are said to be “conserved” if they are at least about 30% identical, at least about 35% identical, at least about 40% identical, at least about 45% identical, at least about 50% identical, at least about 55%, at least about 60% identical, at least about 65% identical, at least about 70% identical, at least about 75% identical, at least about 80% identical, at least about 85% identical, at least about 90% identical, or at least about 95% identical to one another. In some aspects, two or more sequences are said to be “conserved” if they are about 30% identical, about 35% identical, about 40% identical, about 45% identical, about 50% identical, about 55% identical, about 60% identical, about 65% identical, about 70% identical, about 75% identical, about 80% identical, about 85% identical, about 90% identical, about 95% identical, about 98% identical, or about 99% identical to one another. Conservation of sequence may apply to the entire length of an polynucleotide or polypeptide or may apply to a portion, region or feature thereof.

[0121] A “conservative amino acid substitution” is one in which the amino acid residue is replaced with an amino acid residue having a similar side chain. Families of amino acid residues having similar side chains have been defined in the art, including basic side chains ( e.g ., lysine, arginine, histidine), acidic side chains (e.g, aspartic acid, glutamic acid), uncharged polar side chains ( e.g ., glycine, asparagine, glutamine, serine, threonine, tyrosine, cysteine), nonpolar side chains (e.g., alanine, valine, leucine, isoleucine, proline, phenylalanine, methionine, tryptophan), beta-branched side chains (e.g, threonine, valine, isoleucine) and aromatic side chains (e.g, tyrosine, phenylalanine, tryptophan, histidine). Thus, if an amino acid in a polypeptide is replaced with another amino acid from the same side chain family, the substitution is considered to be conservative. In another aspect, a string of amino acids can be conservatively replaced with a structurally similar string that differs in order and/or composition of side chain family members.

[0122] Non-conservative amino acid substitutions include those in which (i) a residue having an electropositive side chain (e.g, Arg, His or Lys) is substituted for, or by, an electronegative residue (e.g, Glu or Asp), (ii) a hydrophilic residue (e.g, Ser or Thr) is substituted for, or by, a hydrophobic residue (e.g, Ala, Leu, lie, Phe or Val), (iii) a cysteine or proline is substituted for, or by, any other residue, or (iv) a residue having a bulky hydrophobic or aromatic side chain (e.g, Val, His, lie or Trp) is substituted for, or by, one having a smaller side chain (e.g, Ala or Ser) or no side chain (e.g, Gly).

[0123] Other amino acid substitutions can also be used. For example, for the amino acid alanine, a substitution can be taken from any one of D-alanine, glycine, beta-alanine, L- cysteine and D-cysteine. For lysine, a replacement can be any one of D-lysine, arginine, D- arginine, homo-arginine, methionine, D-methionine, ornithine, or D- ornithine. Generally, substitutions in functionally important regions that can be expected to induce changes in the properties of isolated polypeptides are those in which (i) a polar residue, e.g, serine or threonine, is substituted for (or by) a hydrophobic residue, e.g, leucine, isoleucine, phenylalanine, or alanine; (ii) a cysteine residue is substituted for (or by) any other residue; (iii) a residue having an electropositive side chain, e.g, lysine, arginine or histidine, is substituted for (or by) a residue having an electronegative side chain, e.g, glutamic acid or aspartic acid; or (iv) a residue having a bulky side chain, e.g, phenylalanine, is substituted for (or by) one not having such a side chain, e.g, glycine. The likelihood that one of the foregoing non-conservative substitutions can alter functional properties of the protein is also correlated to the position of the substitution with respect to functionally important regions of the protein: some non-conservative substitutions can accordingly have little or no effect on biological properties. [0124] As used herein, the term “identity” refers to the overall monomer conservation between polymeric molecules, e.g ., between polypeptide molecules or polynucleotide molecules (e.g. DNA molecules and/or RNA molecules). The term “identical” without any additional qualifiers, e.g, protein A is identical to protein B, implies the sequences are 100% identical (100% sequence identity). Describing two sequences as, e.g, “70% identical,” is equivalent to describing them as having, e.g, “70% sequence identity.”

[0125] Calculation of the percent identity of two polypeptide sequences, for example, can be performed by aligning the two sequences for optimal comparison purposes (e.g, gaps can be introduced in one or both of a first and a second polypeptide sequences for optimal alignment and non-identical sequences can be disregarded for comparison purposes). In certain aspects, the length of a sequence aligned for comparison purposes is at least 30%, at least 40%, at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, at least 95%, or 100% of the length of the reference sequence. The amino acids at corresponding amino acid positions are then compared.

[0126] When a position in the first sequence is occupied by the same amino acid as the corresponding position in the second sequence, then the molecules are identical at that position. The percent identity between the two sequences is a function of the number of identical positions shared by the sequences, taking into account the number of gaps, and the length of each gap, which needs to be introduced for optimal alignment of the two sequences. The comparison of sequences and determination of percent identity between two sequences can be accomplished using a mathematical algorithm. Sequence alignments can be conducted using methods known in the art such as BLAST, MAFFT, Clustal (ClustalW, Clustal X or Clustal Omega), MUSCLE, Needle, Stretcher, etc.

[0127] Different regions within a single polynucleotide or polypeptide target sequence that aligns with a polynucleotide or polypeptide reference sequence can each have their own percent sequence identity. It is noted that the percent sequence identity value is rounded to the nearest tenth. For example, 80.11, 80.12, 80.13, and 80.14 are rounded down to 80.1, while 80.15, 80.16, 80.17, 80.18, and 80.19 are rounded up to 80.2. It also is noted that the length value will always be an integer.

[0128] In certain aspects, the percentage identity (%ID) or of a first amino acid sequence (or nucleic acid sequence) to a second amino acid sequence (or nucleic acid sequence) is calculated as %ID = 100 x (Y/Z), where Y is the number of amino acid residues (or nucleobases) scored as identical matches in the alignment of the first and second sequences (as aligned by visual inspection or a particular sequence alignment program) and Z is the total number of residues in the second sequence. If the length of a first sequence is longer than the second sequence, the percent identity of the first sequence to the second sequence will be higher than the percent identity of the second sequence to the first sequence.

[0129] One skilled in the art will appreciate that the generation of a sequence alignment for the calculation of a percent sequence identity is not limited to binary sequence-sequence comparisons exclusively driven by primary sequence data. It will also be appreciated that sequence alignments can be generated by integrating sequence data with data from heterogeneous sources such as structural data (e.g., crystallographic protein structures), functional data (e.g., location of mutations), or phylogenetic data. A suitable program that integrates heterogeneous data to generate a multiple sequence alignment is T-Coffee, available at www.tcoffee.org, and alternatively available, e.g, from the EBI. It will also be appreciated that the final alignment used to calculate percent sequence identity can be curated either automatically or manually.

[0130] The terms “covalently linked,” “fused,” and grammatical variants thereof are used interchangeably and refer to a first moiety, e.g, a first amino acid sequence or nucleotide sequence, covalently or non-covalently joined to a second moiety, e.g, a second amino acid sequence or nucleotide sequence, respectively. The first moiety can be directly joined or juxtaposed to the second moiety or alternatively an intervening moiety can covalently join the first moiety to the second moiety. The term “linked” means not only a fusion of a first moiety to a second moiety at the C-terminus or the N-terminus, but also includes insertion of the whole first moiety (or the second moiety) into any two points, e.g, amino acids, in the second moiety (or the first moiety, respectively). In some aspects, the first moiety is linked to a second moiety by a peptide bond or a linker. The first moiety can be linked to a second moiety by a phosphodiester bond or a linker. The linker can be a peptide or a polypeptide (for polypeptide chains) or a nucleotide or a nucleotide chain (for nucleotide chains) or any chemical moiety (for polypeptide or polynucleotide chains or any chemical molecules).

[0131] The term “domain,” as used herein, refers to a portion of a polypeptide that retains one or more particular functions. The functional polypeptide domains can be synthetic or naturally occurring, and can comprise a full protein or a domain of a protein that possesses a specific function.

[0132] As used herein, the terms “preferential binding”, “preferentially binds,” or any grammatically similar terms, indicate that a higher number of the key polypeptide binds to the structural region of the cage polypeptide than the latch region to the structural region at equal concentration of the latch region and the key polypeptide in a solution, e.g ., in vivo , and/or the key polypeptide binds to the structural region of the cage polypeptide with a higher binding affinity than the latch region when both the latch region and the key polypeptide are present at equal concentration in a solution, e.g. , in vivo. Preferential binding of the key polypeptide to the structural region means the latch region will unbind the structural region and expose a sequestered degron, which can now function per normal biological function.

[0133] Various aspects described herein are described in further detail in the following subsections.

II Chimeric polypeptides

[0134] The present disclosure provides a chimeric polypeptide comprising a degron, wherein the degron is sequestered or caged at the C-terminal end of the chimeric polypeptide. As used herein, the term “chimeric polypeptide” refers to a molecular system comprising a cage polypeptide that contains a sequestered degron, wherein the degron can be activated via an interaction between the cage polypeptide and a key polypeptide. The chimeric polypeptide, in some aspects, does not contain a key polypeptide, but instead, the key polypeptide can be added when necessary. In some aspects, the chimeric polypeptide further comprises a key polypeptide as a chimeric protein complex formed by the cage polypeptide and the key polypeptide. In certain aspects, the cage polypeptide and the key polypeptide are part of a single polypeptide chain, wherein the cage polypeptide and the key polypeptide are separated by a linker. In some aspects, the linker is a cleavable linker (e.g, comprises a p2a self-cleaving peptide sequence). The cage polypeptide is a helix bundle comprising the sequestered or caged degron in a region of the cage polypeptide denoted as the latch region (i.e., linked to the C-terminus of the latch region), which can be displaced from the cage by a key polypeptide through competitive intermolecular binding. As described herein, when the degron is “linked to the C-terminus of the latch region,” it means that the degron is attached or inserted at the C-terminal end of the latch region. As described further below, in some aspects, the C-terminal end of the latch region can be modified prior to linking the degron to the C-terminus of the latch region. For instance, in certain aspects, one or more amino acid residues of the C-terminal end of a latch region can be removed prior to attaching the degron to the C-terminus of the latch region. After the displacement of the latch region by the key polypeptide, the degron is exposed and accessible, e.g ., to ubiquitin ligases.

[0135] The exposed degron can, for example, be ubiquitinated by a ubiquitin ligase, leading to the degradation of the degron and any bioactive molecules fused or conjugated to the chimeric polypeptide. Any functional polypeptide of interest (e.g, a CAR or a TCR) can be expressed as a fusion protein with a chimeric polypeptide disclosed herein (e.g, chimeric polypeptide of SEQ ID NOs: 1 to 18) such that the functional polypeptide of interest can be conditionally degraded in a titratable manner via endogenous expression (e.g, inducible expression) or the key polypeptide or via administration of the key polypeptide.

[0136] Activation of a chimeric polypeptide integrated in a chimeric antigen receptor (CAR) or a T cell receptor (TCR) by its key polypeptide can lead to internalization and degradation of the CAR or TCR, and subsequent decrease of the amount of CAR or TCR expressed on the cell surface. Accordingly, the chimeric polypeptides disclosed herein can be used to modulate the level of active CAR or TCR present in the cell membrane. The modulation of CAR or TCR activity levels can in turn be used to control the number of engineered immune cells in vivo and/or to prevent, mitigate, or reverse immune cell exhaustion in immune therapy.

[0137] In some aspects, a chimeric polypeptide of the present disclosure comprises a cage polypeptide which comprises a structural region disclosed herein and a latch region that is capable of binding to the structural region, wherein the latch region comprises a degron peptide attached to the C-terminus of the latch region. In certain aspects, the degron peptide comprises, consists, or consists essentially of the amino acid sequence of CGL, YCGL (SEQ ID NO: 136), TYCGL (SEQ ID NO: 137), VTYCGL (SEQ ID NO: 138), RVTYCGL (SEQ ID NO: 139), IRVTYCGL (SEQ ID NO: 140), LIR VTYCGL (SEQ ID NO: 141), or VLIR VTYCGL (SEQ ID NO: 142). In certain aspects, the degron peptide useful for the chimeric polypeptide comprises, consists, or consists essentially of an amino acid sequence that is at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 80%, at least about 90%, or about 100% identical to VLIR VTYCGL (SEQ ID NO: 142). Additional disclosure regarding degron peptides that can be used are provided elsewhere in the present disclosure.

[0138] In some aspects, a chimeric polypeptide disclosed herein comprises a cage polypeptide, which comprises:

(i) a structural region comprising an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence of the structural region of SEQ ID NO: 13 (Cage 13), SEQ ID NO: 14 (Cage 14), SEQ ID NO: 15 (Cage 15), SEQ ID NO: 16 (Cage 16), SEQ ID NO: 17 (Cage 17), SEQ ID NO: 18 (Cage 18), SEQ ID NO: 1 (Cage 1), SEQ ID NO: 2 (Cage 2), SEQ ID NO: 3 (Cage 3), SEQ ID NO: 4 (Cage 4), SEQ ID NO: 5 (Cage 5), SEQ ID NO: 6 (Cage 6), SEQ ID NO: 7 (Cage 7), SEQ ID NO: 8 (Cage 8), SEQ ID NO: 9 (Cage 9), SEQ ID NO: 10 (Cage 10), SEQ ID NO: 11 (Cage 11), or SEQ ID NO: 12 (Cage 12); and

(ii) a latch region comprising a degron peptide which comprises the amino acid sequence of CGL, wherein the latch region is capable of binding to a structural region. In some aspects, the structural polypeptide of the cage polypeptide is capable of preferentially binding to the corresponding key polypeptide when exposed to the key polypeptide.

[0139] In some aspects, the chimeric polypeptide comprises a cage polypeptide, which comprises:

(i) a structural region comprising an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence of the structural region of the cage polypeptide set forth in SEQ ID NO: 13 (Cage 13), SEQ ID NO: 14 (Cage 14), SEQ ID NO: 15 (Cage 15), SEQ ID NO: 16 (Cage 16), SEQ ID NO: 17 (Cage 17), SEQ ID NO: 18 (Cage 18), SEQ ID NO: 1 (Cage 1), SEQ ID NO: 2 (Cage 2), SEQ ID NO: 3 (Cage 3), SEQ ID NO: 4 (Cage 4), SEQ ID NO: 5 (Cage 5), SEQ ID NO: 6 (Cage 6), SEQ ID NO: 7 (Cage 7), SEQ ID NO: 8 (Cage 8), SEQ ID NO: 9 (Cage 9), SEQ ID NO: 10 (Cage 10), SEQ ID NO: 11 (Cage 11), or SEQ ID NO: 12 (Cage 12); and

(ii) a latch region comprising a degron peptide which consists or consists essentially of the amino acid sequence of CGL, wherein the latch region is capable of binding to a structural region. In some aspects, the structural polypeptide of the cage polypeptide is capable of preferentially binding to the corresponding key polypeptide when exposed to the key polypeptide.

[0140] In some aspects, a chimeric polypeptide of the present disclosure comprises a cage polypeptide comprising a structural region and a latch region, wherein the structural region comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to a structural region of SEQ ID NO: 13 (Cage 13), and the latch region is capable of binding to the structural region and comprises a degron peptide selected from CGL, YCGL (SEQ ID NO: 136), TYCGL (SEQ ID NO: 137), VTYCGL (SEQ ID NO: 138), RVTYCGL (SEQ ID NO: 139), IRVTYCGL (SEQ ID NO: 140), LIR VTYCGL (SEQ ID NO: 141), or VLIRVTYCGL (SEQ ID NO: 142). In certain aspects, a chimeric polypeptide of the present disclosure comprises a cage polypeptide comprising a structural region and a latch region, wherein the structural region comprises the structural region of SEQ ID NO: 13 (Cage 13), and the latch region is capable of binding to the structural region and comprises a degron peptide selected from CGL, YCGL (SEQ ID NO: 136), TYCGL (SEQ ID NO: 137), VTYCGL (SEQ ID NO: 138), RVTYCGL (SEQ ID NO: 139), IRVTYCGL (SEQ ID NO: 140), LIR VTYCGL (SEQ ID NO: 141), or VLIRVTYCGL (SEQ ID NO: 142).

[0141] In some aspects, a chimeric polypeptide of the present disclosure comprises a cage polypeptide comprising a structural region and a latch region, wherein the structural region comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to a structural region of SEQ ID NO: 14 (Cage 14), and the latch region is capable of binding to the structural region and comprises a degron peptide selected from CGL, YCGL (SEQ ID NO: 136), TYCGL (SEQ ID NO: 137), VTYCGL (SEQ ID NO: 138), RVTYCGL (SEQ ID NO: 139), IRVTYCGL (SEQ ID NO: 140), LIR VTYCGL (SEQ ID NO: 141), or VLIRVTYCGL (SEQ ID NO: 142). In certain aspects, a chimeric polypeptide of the present disclosure comprises a cage polypeptide comprising a structural region and a latch region, wherein the structural region comprises the structural region of SEQ ID NO: 14 (Cage 14), and the latch region is capable of binding to the structural region and comprises a degron peptide selected from CGL, YCGL (SEQ ID NO: 136), TYCGL (SEQ ID NO: 137), VTYCGL (SEQ ID NO: 138), RVTYCGL (SEQ ID NO: 139), IRVTYCGL (SEQ ID NO: 140), LIR VTYCGL (SEQ ID NO: 141), or VLIRVTYCGL (SEQ ID NO: 142).

[0142] In some aspects, a chimeric polypeptide of the present disclosure comprises a cage polypeptide comprising a structural region and a latch region, wherein the structural region comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to a structural region of SEQ ID NO: 15 (Cage 15), and the latch region is capable of binding to the structural region and comprises a degron peptide selected from CGL, YCGL (SEQ ID NO: 136), TYCGL (SEQ ID NO: 137), VTYCGL (SEQ ID NO: 138), RVTYCGL (SEQ ID NO: 139), IRVTYCGL (SEQ ID NO: 140), LIR VTYCGL (SEQ ID NO: 141), or VLIRVTYCGL (SEQ ID NO: 142) In certain aspects, a chimeric polypeptide of the present disclosure comprises a cage polypeptide comprising a structural region and a latch region, wherein the structural region comprises the structural region of SEQ ID NO: 15 (Cage 15), and the latch region is capable of binding to the structural region and comprises a degron peptide selected from CGL, YCGL (SEQ ID NO: 136), TYCGL (SEQ ID NO: 137), VTYCGL (SEQ ID NO: 138), RVTYCGL (SEQ ID NO: 139), IRVTYCGL (SEQ ID NO: 140), LIR VTYCGL (SEQ ID NO: 141), or VLIRVTYCGL (SEQ ID NO: 142). [0143] In some aspects, a chimeric polypeptide of the present disclosure comprises a cage polypeptide comprising a structural region and a latch region, wherein the structural region comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to a structural region of SEQ ID NO: 16 (Cage 16), and the latch region is capable of binding to the structural region and comprises a degron peptide selected from CGL, YCGL (SEQ ID NO: 136), TYCGL (SEQ ID NO: 137), VTYCGL (SEQ ID NO: 138), RVTYCGL (SEQ ID NO: 139), IRVTYCGL (SEQ ID NO: 140), LIR VTYCGL (SEQ ID NO: 141), or VLIRVTYCGL (SEQ ID NO: 142). In certain aspects, a chimeric polypeptide of the present disclosure comprises a cage polypeptide comprising a structural region and a latch region, wherein the structural region comprises the structural region of SEQ ID NO: 16 (Cage 16), and the latch region is capable of binding to the structural region and comprises a degron peptide selected from CGL, YCGL (SEQ ID NO: 136), TYCGL (SEQ ID NO: 137), VTYCGL (SEQ ID NO: 138), RVTYCGL (SEQ ID NO: 139), IRVTYCGL (SEQ ID NO: 140), LIR VTYCGL (SEQ ID NO: 141), or VLIRVTYCGL (SEQ ID NO: 142).

[0144] In some aspects, a chimeric polypeptide of the present disclosure comprises a cage polypeptide comprising a structural region and a latch region, wherein the structural region comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to a structural region of SEQ ID NO: 17 (Cage 17), and the latch region is capable of binding to the structural region and comprises a degron peptide selected from CGL, YCGL (SEQ ID NO: 136), TYCGL (SEQ ID NO: 137), VTYCGL (SEQ ID NO: 138), RVTYCGL (SEQ ID NO: 139), IRVTYCGL (SEQ ID NO: 140), LIR VTYCGL (SEQ ID NO: 141), or VLIRVTYCGL (SEQ ID NO: 142). In certain aspects, a chimeric polypeptide of the present disclosure comprises a cage polypeptide comprising a structural region and a latch region, wherein the structural region comprises the structural region of SEQ ID NO: 17 (Cage 17), and the latch region is capable of binding to the structural region and comprises a degron peptide selected from CGL, YCGL (SEQ ID NO: 136), TYCGL (SEQ ID NO: 137), VTYCGL (SEQ ID NO: 138), RVTYCGL (SEQ ID NO: 139), IRVTYCGL (SEQ ID NO: 140), LIRVTYCGL (SEQ ID NO: 141), or VLIRVTYCGL (SEQ ID NO: 142).

[0145] In some aspects, a chimeric polypeptide of the present disclosure comprises a cage polypeptide comprising a structural region and a latch region, wherein the structural region comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to a structural region of SEQ ID NO: 18 (Cage 18), and the latch region is capable of binding to the structural region and comprises a degron peptide selected from CGL, YCGL (SEQ ID NO: 136), TYCGL (SEQ ID NO: 137), VTYCGL (SEQ ID NO: 138), RVTYCGL (SEQ ID NO: 139), IRVTYCGL (SEQ ID NO: 140), LIRVTYCGL (SEQ ID NO: 141), or VLIRVTYCGL (SEQ ID NO: 142). In certain aspects, a chimeric polypeptide of the present disclosure comprises a cage polypeptide comprising a structural region and a latch region, wherein the structural region comprises the structural region of SEQ ID NO: 18 (Cage 18), and the latch region is capable of binding to the structural region and comprises a degron peptide selected from CGL, YCGL (SEQ ID NO: 136), TYCGL (SEQ ID NO: 137), VTYCGL (SEQ ID NO: 138), RVTYCGL (SEQ ID NO: 139), IRVTYCGL (SEQ ID NO: 140), LIRVTYCGL (SEQ ID NO: 141), or VLIRVTYCGL (SEQ ID NO: 142).

[0146] In some aspects, a chimeric polypeptide of the present disclosure comprises a cage polypeptide comprising a structural region and a latch region, wherein the structural region comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to a structural region of SEQ ID NO: 1 (Cage 1), and the latch region is capable of binding to the structural region and comprises a degron peptide selected from CGL, YCGL (SEQ ID NO: 136), TYCGL (SEQ ID NO: 137), VTYCGL (SEQ ID NO: 138), RVTYCGL (SEQ ID NO: 139), IRVTYCGL (SEQ ID NO: 140), LIRVTYCGL (SEQ ID NO: 141), or VLIRVTYCGL (SEQ ID NO: 142). In certain aspects, a chimeric polypeptide of the present disclosure comprises a cage polypeptide comprising a structural region and a latch region, wherein the structural region comprises the structural region of SEQ ID NO: 1 (Cage 1), and the latch region is capable of binding to the structural region and comprises a degron peptide selected from CGL, YCGL (SEQ ID NO: 136), TYCGL (SEQ ID NO: 137), VTYCGL (SEQ ID NO: 138), RVTYCGL (SEQ ID NO: 139), IR VTYCGL (SEQ ID NO: 140), LIR VTYCGL (SEQ ID NO: 141), or VLIR VTYCGL (SEQ ID NO: 142).

[0147] In some aspects, a chimeric polypeptide of the present disclosure comprises a cage polypeptide comprising a structural region and a latch region, wherein the structural region comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to a structural region of SEQ ID NO: 2 (Cage 2), and the latch region is capable of binding to the structural region and comprises a degron peptide selected from CGL, YCGL (SEQ ID NO: 136), TYCGL (SEQ ID NO: 137), VTYCGL (SEQ ID NO: 138), RVTYCGL (SEQ ID NO: 139), IR VTYCGL (SEQ ID NO: 140), LIR VTYCGL (SEQ ID NO: 141), or VLIR VTYCGL (SEQ ID NO: 142). In certain aspects, a chimeric polypeptide of the present disclosure comprises a cage polypeptide comprising a structural region and a latch region, wherein the structural region comprises the structural region of SEQ ID NO: 2 (Cage 2), and the latch region is capable of binding to the structural region and comprises a degron peptide selected from CGL, YCGL (SEQ ID NO: 136), TYCGL (SEQ ID NO: 137), VTYCGL (SEQ ID NO: 138), RVTYCGL (SEQ ID NO: 139), IR VTYCGL (SEQ ID NO: 140), LIR VTYCGL (SEQ ID NO: 141), or VLIR VTYCGL (SEQ ID NO: 142).

[0148] In some aspects, a chimeric polypeptide of the present disclosure comprises a cage polypeptide comprising a structural region and a latch region, wherein the structural region comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to a structural region of SEQ ID NO: 3 (Cage 3), and the latch region is capable of binding to the structural region and comprises a degron peptide selected from CGL, YCGL (SEQ ID NO: 136), TYCGL (SEQ ID NO: 137), VTYCGL (SEQ ID NO: 138), RVTYCGL (SEQ ID NO: 139), IR VTYCGL (SEQ ID NO: 140), LIR VTYCGL (SEQ ID NO: 141), or VLIR VTYCGL (SEQ ID NO: 142). In certain aspects, a chimeric polypeptide of the present disclosure comprises a cage polypeptide comprising a structural region and a latch region, wherein the structural region comprises the structural region of SEQ ID NO: 3 (Cage 3), and the latch region is capable of binding to the structural region and comprises a degron peptide selected from CGL, YCGL (SEQ ID NO: 136), TYCGL (SEQ ID NO: 137), VTYCGL (SEQ ID NO: 138), RVTYCGL (SEQ ID NO: 139), IR VTYCGL (SEQ ID NO: 140), LIR VTYCGL (SEQ ID NO: 141), or VLIR VTYCGL (SEQ ID NO: 142).

[0149] In some aspects, a chimeric polypeptide of the present disclosure comprises a cage polypeptide comprising a structural region and a latch region, wherein the structural region comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to a structural region of SEQ ID NO: 4 (Cage 4), and the latch region is capable of binding to the structural region and comprises a degron peptide selected from CGL, YCGL (SEQ ID NO: 136), TYCGL (SEQ ID NO: 137), VTYCGL (SEQ ID NO: 138), RVTYCGL (SEQ ID NO: 139), IR VTYCGL (SEQ ID NO: 140), LIR VTYCGL (SEQ ID NO: 141), or VLIR VTYCGL (SEQ ID NO: 142). In certain aspects, a chimeric polypeptide of the present disclosure comprises a cage polypeptide comprising a structural region and a latch region, wherein the structural region comprises the structural region of SEQ ID NO: 4 (Cage 4), and the latch region is capable of binding to the structural region and comprises a degron peptide selected from CGL, YCGL (SEQ ID NO: 136), TYCGL (SEQ ID NO: 137), VTYCGL (SEQ ID NO: 138), RVTYCGL (SEQ ID NO: 139), IR VTYCGL (SEQ ID NO: 140), LIR VTYCGL (SEQ ID NO: 141), or VLIR VTYCGL (SEQ ID NO: 142).

[0150] In some aspects, a chimeric polypeptide of the present disclosure comprises a cage polypeptide comprising a structural region and a latch region, wherein the structural region comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to a structural region of SEQ ID NO: 5 (Cage 5), and the latch region is capable of binding to the structural region and comprises a degron peptide selected from CGL, YCGL (SEQ ID NO: 136), TYCGL (SEQ ID NO: 137), VTYCGL (SEQ ID NO: 138), RVTYCGL (SEQ ID NO: 139), IR VTYCGL (SEQ ID NO: 140), LIRVTYCGL (SEQ ID NO: 141), or VLIRVTYCGL (SEQ ID NO: 142). In certain aspects, a chimeric polypeptide of the present disclosure comprises a cage polypeptide comprising a structural region and a latch region, wherein the structural region comprises the structural region of SEQ ID NO: 5 (Cage 5), and the latch region is capable of binding to the structural region and comprises a degron peptide selected from CGL, YCGL (SEQ ID NO: 136), TYCGL (SEQ ID NO: 137), VTYCGL (SEQ ID NO: 138), RVTYCGL (SEQ ID NO: 139), IR VTYCGL (SEQ ID NO: 140), LIRVTYCGL (SEQ ID NO: 141), or VLIRVTYCGL (SEQ ID NO: 142).

[0151] In some aspects, a chimeric polypeptide of the present disclosure comprises a cage polypeptide comprising a structural region and a latch region, wherein the structural region comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to a structural region of SEQ ID NO: 6 (Cage 6), and the latch region is capable of binding to the structural region and comprises a degron peptide selected from CGL, YCGL (SEQ ID NO: 136), TYCGL (SEQ ID NO: 137), VTYCGL (SEQ ID NO: 138), RVTYCGL (SEQ ID NO: 139), IR VTYCGL (SEQ ID NO: 140), LIRVTYCGL (SEQ ID NO: 141), or VLIRVTYCGL (SEQ ID NO: 142). In certain aspects, a chimeric polypeptide of the present disclosure comprises a cage polypeptide comprising a structural region and a latch region, wherein the structural region comprises the structural region of SEQ ID NO: 6 (Cage 6), and the latch region is capable of binding to the structural region and comprises a degron peptide selected from CGL, YCGL (SEQ ID NO: 136), TYCGL (SEQ ID NO: 137), VTYCGL (SEQ ID NO: 138), RVTYCGL (SEQ ID NO: 139), IR VTYCGL (SEQ ID NO: 140), LIRVTYCGL (SEQ ID NO: 141), or VLIRVTYCGL (SEQ ID NO: 142).

[0152] In some aspects, a chimeric polypeptide of the present disclosure comprises a cage polypeptide comprising a structural region and a latch region, wherein the structural region comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to a structural region of SEQ ID NO: 7 (Cage 7), and the latch region is capable of binding to the structural region and comprises a degron peptide selected from CGL, YCGL (SEQ ID NO: 136), TYCGL (SEQ ID NO: 137), VTYCGL (SEQ ID NO: 138), RVTYCGL (SEQ ID NO: 139), IRVTYCGL (SEQ ID NO: 140), LIR VTYCGL (SEQ ID NO: 141), or VLIR VTYCGL (SEQ ID NO: 142). In certain aspects, a chimeric polypeptide of the present disclosure comprises a cage polypeptide comprising a structural region and a latch region, wherein the structural region comprises the structural region of SEQ ID NO: 7 (Cage 7), and the latch region is capable of binding to the structural region and comprises a degron peptide selected from CGL, YCGL (SEQ ID NO: 136), TYCGL (SEQ ID NO: 137), VTYCGL (SEQ ID NO: 138), RVTYCGL (SEQ ID NO: 139), IRVTYCGL (SEQ ID NO: 140), LIR VTYCGL (SEQ ID NO: 141), or VLIR VTYCGL (SEQ ID NO: 142).

[0153] In some aspects, a chimeric polypeptide of the present disclosure comprises a cage polypeptide comprising a structural region and a latch region, wherein the structural region comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to a structural region of SEQ ID NO: 8 (Cage 8), and the latch region is capable of binding to the structural region and comprises a degron peptide selected from CGL, YCGL (SEQ ID NO: 136), TYCGL (SEQ ID NO: 137), VTYCGL (SEQ ID NO: 138), RVTYCGL (SEQ ID NO: 139), IRVTYCGL (SEQ ID NO: 140), LIR VTYCGL (SEQ ID NO: 141), or VLIR VTYCGL (SEQ ID NO: 142). In certain aspects, a chimeric polypeptide of the present disclosure comprises a cage polypeptide comprising a structural region and a latch region, wherein the structural region comprises the structural region of SEQ ID NO: 8 (Cage 8), and the latch region is capable of binding to the structural region and comprises a degron peptide selected from CGL, YCGL (SEQ ID NO: 136), TYCGL (SEQ ID NO: 137), VTYCGL (SEQ ID NO: 138), RVTYCGL (SEQ ID NO: 139), IRVTYCGL (SEQ ID NO: 140), LIR VTYCGL (SEQ ID NO: 141), or VLIR VTYCGL (SEQ ID NO: 142).

[0154] In some aspects, a chimeric polypeptide of the present disclosure comprises a cage polypeptide comprising a structural region and a latch region, wherein the structural region comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to a structural region of SEQ ID NO: 9 (Cage 9), and the latch region is capable of binding to the structural region and comprises a degron peptide selected from CGL, YCGL (SEQ ID NO: 136), TYCGL (SEQ ID NO: 137), VTYCGL (SEQ ID NO: 138), RVTYCGL (SEQ ID NO: 139), IRVTYCGL (SEQ ID NO: 140), LIR VTYCGL (SEQ ID NO: 141), or VLIR VTYCGL (SEQ ID NO: 142). In certain aspects, a chimeric polypeptide of the present disclosure comprises a cage polypeptide comprising a structural region and a latch region, wherein the structural region comprises the structural region of SEQ ID NO: 9 (Cage 9), and the latch region is capable of binding to the structural region and comprises a degron peptide selected from CGL, YCGL (SEQ ID NO: 136), TYCGL (SEQ ID NO: 137), VTYCGL (SEQ ID NO: 138), RVTYCGL (SEQ ID NO: 139), IRVTYCGL (SEQ ID NO: 140), LIR VTYCGL (SEQ ID NO: 141), or VLIR VTYCGL (SEQ ID NO: 142).

[0155] In some aspects, a chimeric polypeptide of the present disclosure comprises a cage polypeptide comprising a structural region and a latch region, wherein the structural region comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to a structural region of SEQ ID NO: 10 (Cage 10), and the latch region is capable of binding to the structural region and comprises a degron peptide selected from CGL, YCGL (SEQ ID NO: 136), TYCGL (SEQ ID NO: 137), VTYCGL (SEQ ID NO: 138), RVTYCGL (SEQ ID NO: 139), IRVTYCGL (SEQ ID NO: 140), LIR VTYCGL (SEQ ID NO: 141), or VLIRVTYCGL (SEQ ID NO: 142). In certain aspects, a chimeric polypeptide of the present disclosure comprises a cage polypeptide comprising a structural region and a latch region, wherein the structural region comprises the structural region of SEQ ID NO: 10 (Cage 10), and the latch region is capable of binding to the structural region and comprises a degron peptide selected from CGL, YCGL (SEQ ID NO: 136), TYCGL (SEQ ID NO: 137), VTYCGL (SEQ ID NO: 138), RVTYCGL (SEQ ID NO: 139), IRVTYCGL (SEQ ID NO: 140), LIR VTYCGL (SEQ ID NO: 141), or VLIRVTYCGL (SEQ ID NO: 142).

[0156] In some aspects, a chimeric polypeptide of the present disclosure comprises a cage polypeptide comprising a structural region and a latch region, wherein the structural region comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to a structural region of SEQ ID NO: 11 (Cage 11), and the latch region is capable of binding to the structural region and comprises a degron peptide selected from CGL, YCGL (SEQ ID NO: 136), TYCGL (SEQ ID NO: 137), VTYCGL (SEQ ID NO: 138), RVTYCGL (SEQ ID NO: 139), IRVTYCGL (SEQ ID NO: 140), LIR VTYCGL (SEQ ID NO: 141), or VLIRVTYCGL (SEQ ID NO: 142). In certain aspects, a chimeric polypeptide of the present disclosure comprises a cage polypeptide comprising a structural region and a latch region, wherein the structural region comprises the structural region of SEQ ID NO: 11 (Cage 11), and the latch region is capable of binding to the structural region and comprises a degron peptide selected from CGL, YCGL (SEQ ID NO: 136), TYCGL (SEQ ID NO: 137), VTYCGL (SEQ ID NO: 138), RVTYCGL (SEQ ID NO: 139), IRVTYCGL (SEQ ID NO: 140), LIR VTYCGL (SEQ ID NO: 141), or VLIRVTYCGL (SEQ ID NO: 142).

[0157] In some aspects, a chimeric polypeptide of the present disclosure comprises a cage polypeptide comprising a structural region and a latch region, wherein the structural region comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to a structural region of SEQ ID NO: 12 (Cage 12), and the latch region is capable of binding to the structural region and comprises a degron peptide selected from CGL, YCGL (SEQ ID NO: 136), TYCGL (SEQ ID NO: 137), VTYCGL (SEQ ID NO: 138), RVTYCGL (SEQ ID NO: 139), IRVTYCGL (SEQ ID NO: 140), LIR VTYCGL (SEQ ID NO: 141), or VLIRVTYCGL (SEQ ID NO: 142). In certain aspects, a chimeric polypeptide of the present disclosure comprises a cage polypeptide comprising a structural region and a latch region, wherein the structural region comprises the structural region of SEQ ID NO: 12 (Cage 12), and the latch region is capable of binding to the structural region and comprises a degron peptide selected from CGL, YCGL (SEQ ID NO: 136), TYCGL (SEQ ID NO: 137), VTYCGL (SEQ ID NO: 138), RVTYCGL (SEQ ID NO: 139), IRVTYCGL (SEQ ID NO: 140), LIR VTYCGL (SEQ ID NO: 141), or VLIRVTYCGL (SEQ ID NO: 142). [0158] In some aspects, a given amino acid in a chimeric polypeptide disclosed herein can be replaced by a residue having similar physiochemical characteristics, e.g ., substituting one aliphatic residue for another (such as lie, Val, Leu, or Ala for one another), or substitution of one polar residue for another (such as between Lys and Arg; Glu and Asp; or Gin and Asn). Other such conservative substitutions, e.g. , substitutions of entire regions having similar hydrophobicity characteristics, are known. Polypeptides comprising conservative amino acid substitutions can be tested in any one of the assays described herein to confirm that the desired activity is retained. Amino acids can be grouped according to similarities in the properties of their side chains: (1) non-polar: Ala (A), Val (V), Leu (L), lie (I), Pro (P), Phe (F), Trp (W), Met (M); (2) uncharged polar: Gly (G), Ser (S), Thr (T), Cys (C), Tyr (Y), Asn (N), Gin (Q); (3) acidic: Asp (D), Glu (E); (4) basic: Lys (K), Arg (R), His (H). Alternatively, naturally occurring residues can be divided into groups based on common side-chain properties: (1) hydrophobic: Norleucine, Met, Ala, Val, Leu, He; (2) neutral hydrophilic: Cys, Ser, Thr, Asn, Gin; (3) acidic: Asp, Glu; (4) basic: His, Lys, Arg; (5) residues that influence chain orientation: Gly, Pro; (6) aromatic: Trp, Tyr, Phe. Particular conservative substitutions include, for example; Ala into Gly or into Ser; Arg into Lys; Asn into Gin or into H is; Asp into Glu; Cys into Ser; Gin into Asn; Glu into Asp; Gly into Ala or into Pro; His into Asn or into Gin; He into Leu or into Val; Leu into He or into Val; Lys into Arg, into Gin or into Glu; Met into Leu, into Tyr or into He; Phe into Met, into Leu or into Tyr; Ser into Thr; Thr into Ser; Trp into Tyr; Tyr into Trp; and/or Phe into Val, into He or into Leu.

[0159] In some aspects, the chimeric polypeptide of the present disclosure can include additional amino acid residues at the N-terminus, C-terminus, internal to the polypeptide, or a combination thereof. Such amino acid residues can be, e.g. , detectable moieties such as fluorescent proteins, antibody epitope tags, etc. Additional moieties that can be included in a chimeric polypeptide described herein are provided elsewhere in the present disclosure.

II. a. Cage Polypeptide

[0160] In some aspects, a cage polypeptide of a chimeric polypeptide disclosed herein comprises a helical bundle, comprising between 2 and 7 alpha helices, wherein the helical bundle comprises: (i) a structural region; and (ii) a latch region, wherein the latch region is capable of binding to the structural region. Latch regions can be present near either terminus of a cage polypeptide of a chimeric polypeptide. In some aspects, the latch region can comprise a part or all of a single alpha helix at the N-terminal or C-terminal portion of the cage polypeptide. In some aspects, the latch region can comprise a part or all of a first, second, third, fourth, fifth, sixth, or seventh alpha helix in the cage polypeptide. In further aspects, the latch region can comprise all or part of two or more different alpha helices in the cage polypeptide; for example, a C-terminal part of one alpha helix and an N-terminal portion of the next alpha helix, or all of two consecutive alpha helices.

[0161] In some aspects, the cage polypeptide of the present disclosure comprises at least three, at least four, at least five, at least six, or at least seven alpha helices, wherein the N- terminal alpha helix or the C-terminal alpha helix is a latch region and the other alpha helices are a structural region. In some aspects, the cage polypeptide of the disclosure comprises at least three or alpha helices, wherein at least three of the alpha helices are capable of forming hydrogen bond networks and hydrophobic interaction. In some aspects, the cage polypeptide of the disclosure comprises at least three or more alpha helices, wherein each of the alpha helices including the latch region is the same, i.e., the same sequence. In some aspects, the sequence of the latch region is similar to the alpha helices, but is not identical. In some aspects, the sequence of the latch region has at least one amino acid, at least two amino acids, at least three amino acids, at least four amino acids, at least five amino acids, at least six amino acids, at least seven amino acids, at least eight amino acids, at least nine amino acids, at least ten amino acids, at least 15 amino acids, at least 20 amino acids, at least 25 amino acids, at least 30 amino acids, at least 35 amino acids, or at least 40 amino acids, at least 45 amino acids different from the sequence of the other alpha helices in the cage polypeptide. The difference in sequence can include amino acid mutation, deletion, or insertion. In some aspects, the sequence of the latch region has at least one amino acid, at least two amino acids, at least three amino acids, at least four amino acids, at least five amino acids, at least six amino acids, at least seven amino acids, at least eight amino acids, at least nine amino acids, at least ten amino acids, at least 15 amino acids, at least 20 amino acids, at least 25 amino acids, at least 30 amino acids, at least 35 amino acids, or at least 40 amino acids, or at least 45 amino acids shorter than the sequence of the other alpha helices in the cage polypeptide.

[0162] In some aspects, the cage polypeptide comprises three alpha helices, wherein two alpha helices form a structural region and one alpha helix forms a latch region. In some aspects, the cage polypeptide comprises four alpha helices, wherein three alpha helices form a structural region and one alpha helix forms a latch region. [0163] In some aspects, the latch region of a cage polypeptide of the present disclosure is placed at the C-terminal helix so as to position the degron for maximum burial of the functional residues that need to be sequestered to maintain the bioactive peptide in an inactive state while simultaneously burying hydrophobic residues and promoting solvent exposure/compensatory hydrogen bonds of polar residues. In some aspects, the alpha helices of the structural region and the latch region can interact with each other via a combination of hydrophobic contacts and hydrogen bond networks formed between helical interfaces.

[0164] In some aspects, the latch region can comprise a single alpha helix that interacts with the alpha helices of the structural region in the absence of a key polypeptide. In such aspects, the structural region can comprise five alpha helices and the interaction with the latch region results in a six helix bundle cage polypeptide (“5plusl” design). In further aspects, the structural region can comprise three alpha helices and the interaction with the latch region results in a four helix bundle cage polypeptide (“3plusl” design). In still further aspects, the structural region can comprise two alpha helices and the interaction with the latch region results in a three helix bundle cage polypeptide (“2plusl” design). In some aspects, the alpha helices of the structural region and the latch region can interact with each other via a combination of hydrophobic contacts and hydrogen bond networks formed between helical interfaces. Table 1 (below) illustrates the different alpha helices of the protein scaffolds used to construct the chimeric polypeptides disclosed herein.

Table 1. Alpha Helices of 2plusl Design Constructs

Table 2. Alpha Helices of 3plusl Design Constructs

[0165] In some aspects, a cage polypeptide disclosed herein comprises 3-7, 4-7, 5-7, 6-7, 2- 6, 3-6, 4-6, 5-6, 2-5, 3-5, 4-5, 2-4, 3-4, or 2-3 alpha helices. In some aspects, a cage polypeptide comprises 3, 4, 5, 6, or 7 alpha helices. In certain aspects, a cage polypeptide comprises 6 alpha helices ( e.g ., 5 alpha helices that make up the structural region and 1 alpha helix that make up the latch region; “5plusl” design). In further aspects, a cage polypeptide comprises 4 alpha helices (e.g., 3 alpha helices that make up the structural region and 1 alpha helix that make up the latch region; “3plusl” design). In still further aspects, a cage polypeptide comprises 3 alpha helices (e.g, 2 alpha helices that make up the structural region and 1 alpha helix that make up the latch region; “2plusl” design).

[0166] Design of the helical bundle cage polypeptides of the disclosure can be carried out by any suitable means. In certain aspects, a BUNDLEGRID SAMPLER™ in the ROSETTA™ program can be used to generate backbone geometry based on the Crick expression for a coiled- coil and allows efficient, parallel sampling of a regular grid of coiled-coil expression parameter values, which correspond to a continuum of peptide backbone conformations. This can be supplemented by design for hydrogen bond networks using any suitable means, including but not limited to, as described in Boyken et. al, (Science 352, 680-687 (2016)), followed by ROSETTA™ sidechain design. In further aspects, best scoring designs, based on total score, number of unsatisfied hydrogen bonds, and lack of voids in the core of the protein can be selected for helical bundle cage polypeptide design.

[0167] Each alpha helix of a cage polypeptide disclosed herein can be of any suitable length and/or amino acid composition as appropriate for an intended use ( e.g ., to effectively sequester a degron of the present disclosure, e.g., a degron comprising, consisting of, or consisting essentially of the amino acid CGL). In some aspects, each helix is independently 38 to 58 amino acids in length. In certain aspects, each helix is independently between 18-60, 18-55, 18-50, 18-45, 22-60, 22-55, 22-50, 22-45, 25-60, 25-55, 25-50, 25-45, 28-60, 28-55, 28-50, 28-45, 32-60, 32-55, 32-50, 32-45, 35-60, 35-55, 35-50, 35-45, 38-60, 38-55, 38-50, 38-45, 40-60, 40-58, 40-55, 40-50, or 40-45 amino acids in length. In some aspects, one or more helices in the cage polypeptide comprises 38 to 45 amino acids, e.g, 38, 39, 40, 41, 42, 43, 44, or 45. In some aspects, one or more helices in the cage polypeptide comprises 45 to 52 amino acids, e.g, 45, 46, 47, 48, 49, 50, 51, or 52. In some aspects, one or more helices in the cage polypeptide comprises 52 to 58 amino acids, 52, 53, 54, 55, 56, 57, or 58.

[0168] In some aspects, a chimeric polypeptide disclosed herein comprises a cage polypeptide comprising:

(i) a structural region comprising an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in (i) helix 1 and/or helix 2 of SEQ ID NO: 13 or 14 (Cage 13 or Cage 14) (i.e., SEQ ID NOs: 40 and 41, respectively), (ii) helix 1 and/or helix 2 of SEQ ID NO: 15 (Cage 15) (i.e., SEQ ID NOs: 43 and 44, respectively), (iii) helix 1 and/or helix 2 of SEQ ID NO: 16 (Cage 16) (i.e., SEQ ID NOs: 46 and 47, respectively), (iv) helix 1 and/or helix 2 of SEQ ID NO: 17 (Cage 17) (i.e., SEQ ID NOs: 49 and 50, respectively), (v) helix 1 and/or helix 2 of SEQ ID NO: 18 (Cage 18) (i.e., SEQ ID NOs: 52 and 53, respectively), (vi) helix 1, helix 2, and/or helix 3 of SEQ ID NO: 1 (Cage 1) (i.e., SEQ ID NOs: 55-57, respectively), (vii) helix 1, helix 2, and/or helix 3 of SEQ ID NO: 2 (Cage 2) (i.e., SEQ ID NOs: 59-61, respectively), (viii) helix 1, helix 2, and/or helix 3 of SEQ ID NO: 3 (Cage 3) (i.e., SEQ ID NOs: 63-65, respectively), (ix) helix 1, helix 2, and/or helix 3 of SEQ ID NO: 4 (Cage 4) (i.e., SEQ ID NOs: 71-73, respectively), (x) helix 1, helix 2, and/or helix 3 of SEQ ID NO: 5 (Cage 5) (i.e., SEQ ID NOs: 79-81, respectively), (xi) helix 1, helix 2, and/or helix 3 of SEQ ID NO: 6 (Cage 6) (i.e., SEQ ID NOs: 83-85, respectively), (xii) helix 1, helix 2, and/or helix 3 of SEQ ID NO: 7 (Cage 7) (i.e., SEQ ID NOs: 87-89, respectively), (xiii) helix 1, helix 2, and/or helix 3 of SEQ ID NO: 8 (Cage 8) (i.e., SEQ ID NOs: 91-93, respectively), (xiv) helix 1, helix 2, and/or helix 3 of SEQ ID NO: 9 (Cage 9) (i.e., SEQ ID NOs: 95-97, respectively), (xv) helix 1, helix 2, and/or helix 3 of SEQ ID NO: 10 (Cage 10) (i.e., SEQ ID NOs: 99-101, respectively), (xvi) helix 1, helix 2, and/or helix 3 of SEQ ID NO: 11 (Cage 11) (i.e., SEQ ID NOs: 103-105, respectively), (xvii) helix 1, helix 2, and/or helix 3 of SEQ ID NO: 12 (Cage 12) (i.e., SEQ ID NOs: 111-113, respectively), and

(ii) a latch region comprising a degron peptide which comprises the amino acid sequence of CGL,

[0169] wherein the latch region is capable of binding to a structural region. In some aspects, the structural polypeptide of the cage polypeptide is capable of preferentially binding to the corresponding key polypeptide when exposed to the key polypeptide. SEQ ID NOs for the different helices are also provided in Tables 1 and 2.

[0170] In some aspects, a chimeric polypeptide disclosed herein comprises a cage polypeptide comprising:

(i) a structural region comprising an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in (i) helix 1 and/or helix 2 of SEQ ID NO: 13 or 14 (Cage 13 or Cage 14) (i.e., SEQ ID NOs: 40 and 41, respectively), (ii) helix 1 and/or helix 2 of SEQ ID NO: 15 (Cage 15) {i.e., SEQ ID NOs: 43 and 44, respectively), (iii) helix 1 and/or helix 2 of SEQ ID NO: 16 (Cage 16) {i.e., SEQ ID NOs: 46 and 47, respectively), (iv) helix 1 and/or helix 2 of SEQ ID NO: 17 (Cage 17) {i.e., SEQ ID NOs: 49 and 50, respectively), (v) helix 1 and/or helix 2 of SEQ ID NO: 18 (Cage 18) ( i.e ., SEQ ID NOs: 52 and 53, respectively), (vi) helix 1, helix 2, and/or helix 3 of SEQ ID NO: 1 (Cage 1) {i.e., SEQ ID NOs: 55-57, respectively), (vii) helix 1, helix 2, and/or helix 3 of SEQ ID NO: 2 (Cage 2) {i.e., SEQ ID NOs: 59-61, respectively), (viii) helix 1, helix 2, and/or helix 3 of SEQ ID NO: 3 (Cage 3) {i.e., SEQ ID NOs: 63-65, respectively), (ix) helix 1, helix 2, and/or helix 3 of SEQ ID NO: 4 (Cage 4) {i.e., SEQ ID NOs: 71-73, respectively), (x) helix 1, helix 2, and/or helix 3 of SEQ ID NO: 5 (Cage 5) {i.e., SEQ ID NOs: 79-81, respectively), (xi) helix 1, helix 2, and/or helix 3 of SEQ ID NO: 6 (Cage 6) {i.e., SEQ ID NOs: 83-85, respectively), (xii) helix 1, helix 2, and/or helix 3 of SEQ ID NO: 7 (Cage 7) {i.e., SEQ ID NOs: 87-89, respectively), (xiii) helix 1, helix 2, and/or helix 3 of SEQ ID NO: 8 (Cage 8) {i.e., SEQ ID NOs: 91-93, respectively), (xiv) helix 1, helix 2, and/or helix 3 of SEQ ID NO: 9 (Cage 9) {i.e., SEQ ID NOs: 95-97, respectively), (xv) helix 1, helix 2, and/or helix 3 of SEQ ID NO: 10 (Cage 10) {i.e., SEQ ID NOs: 99-101, respectively), (xvi) helix 1, helix 2, and/or helix 3 of SEQ ID NO: 11 (Cage 11) {i.e., SEQ ID NOs: 103-105, respectively), (xvii) helix 1, helix 2, and/or helix 3 of SEQ ID NO: 12 (Cage 12) {i.e., SEQ ID NOs: 111-113, respectively), and

(ii) a latch region comprising a degron peptide which consists or consists essentially of the amino acid sequence of CGL, wherein the latch region is capable of binding to a structural region. In some aspects, the structural polypeptide of the cage polypeptide is capable of preferentially binding to the corresponding key polypeptide when exposed to the key polypeptide. SEQ ID NOs for the different helices are also provided in Tables 1 and 2.

[0171] In some aspects, the structural region of a cage polypeptide comprises one or more of at least about 10, at least about 15, at least about 20, at least about 25, at least about 30, at least about 35, at least about 40, at least about 45, or at least about 50 consecutive amino acids of (i) helix 1 and/or helix 2 of SEQ ID NO: 13 or 14 (Cage 13 or Cage 14) {i.e., SEQ ID NOs: 40 and 41, respectively), (ii) helix 1 and/or helix 2 of SEQ ID NO: 15 (Cage 15) {i.e., SEQ ID NOs: 43 and 44, respectively), (iii) helix 1 and/or helix 2 of SEQ ID NO: 16 (Cage 16) {i.e., SEQ ID NOs: 46 and 47, respectively), (iv) helix 1 and/or helix 2 of SEQ ID NO: 17 (Cage 17) {i.e., SEQ ID NOs: 49 and 50, respectively), (v) helix 1 and/or helix 2 of SEQ ID NO: 18 (Cage 18) (i.e., SEQ ID NOs: 52 and 53, respectively), (vi) helix 1, helix 2, and/or helix 3 of SEQ ID NO: 1 (Cage 1) (i.e., SEQ ID NOs: 55-57, respectively), (vii) helix 1, helix 2, and/or helix 3 of SEQ ID NO: 2 (Cage 2) ( i.e ., SEQ ID NOs: 59-61, respectively), (viii) helix 1, helix 2, and/or helix 3 of SEQ ID NO: 3 (Cage 3) (i.e., SEQ ID NOs: 63-65, respectively), (ix) helix 1, helix 2, and/or helix 3 of SEQ ID NO: 4 (Cage 4) {i.e., SEQ ID NOs: 71-73, respectively), (x) helix 1, helix 2, and/or helix 3 of SEQ ID NO: 5 (Cage 5) (i.e., SEQ ID NOs: 79-81, respectively), (xi) helix 1, helix 2, and/or helix 3 of SEQ ID NO: 6 (Cage 6) (i.e., SEQ ID NOs: 83-85, respectively), (xii) helix 1, helix 2, and/or helix 3 of SEQ ID NO: 7 (Cage 7) (i.e., SEQ ID NOs: 87-89, respectively), (xiii) helix 1, helix 2, and/or helix 3 of SEQ ID NO: 8 (Cage 8) (i.e., SEQ ID NOs: 91-93, respectively), (xiv) helix 1, helix 2, and/or helix 3 of SEQ ID NO: 9 (Cage 9) (i.e., SEQ ID NOs: 95-97, respectively), (xv) helix 1, helix 2, and/or helix 3 of SEQ ID NO: 10 (Cage 10) (i.e., SEQ ID NOs: 99-101, respectively), (xvi) helix 1, helix 2, and/or helix 3 of SEQ ID NO: 11 (Cage 11) (i.e., SEQ ID NOs: 103-105, respectively), (xvii) helix 1, helix 2, and/or helix 3 of SEQ ID NO: 12 (Cage 12 ) (i.e., SEQ ID NOs: 111-113, respectively). SEQ ID NOs for the different helices are also provided in Tables 1 and 2.

[0172] In some aspects, the latch region of a cage polypeptide disclosed herein comprises an amino acid sequence having at least about 50%, at least about 60%, at least about 70%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99% or about 100% sequence identity to the amino acid sequence set forth in (i) helix 3 of SEQ ID NO: 13 (Cage 13) (i.e., SEQ ID NO: 115); (ii) helix 3 of SEQ ID NO: 14 (Cage 14) (i.e., SEQ ID NO: 116); (iii) helix 3 of SEQ ID NO: 15 (Cage 15) (i.e., SEQ ID NO: 117); (iv) helix 3 of SEQ ID NO: 16 (Cage 16) (i.e., SEQ ID NO: 118); (v) helix 3 of SEQ ID NO: 17 (Cage 17) (i.e., SEQ ID NO: 119); (vi) helix 3 of SEQ ID NO: 18 (Cage 18) (i.e., SEQ ID NO: 120); (vii) helix 4 of SEQ ID NO: 1 (Cage 1) (i.e., SEQ ID NO: 121); (viii) helix 4 of SEQ ID NO: 2 (Cage 2) (i.e., SEQ ID NO: 122); (ix) helix 4 of SEQ ID NO: 3 (Cage 3) (i.e., SEQ ID NO: 124); (x) helix 4 of SEQ ID NO: 4 (Cage 4) (i.e., SEQ ID NO: 125); (xi) helix 4 of SEQ ID NO: 5 (Cage 5) (i.e., SEQ ID NO: 127); (xii) helix 4 of SEQ ID NO: 6 (Cage 6) (i.e., SEQ ID NO: 128); (xiv) helix 4 of SEQ ID NO: 7 (Cage 7) (i.e., SEQ ID NO: 129); (xv) helix 4 of SEQ ID NO: 8 (Cage 8) (i.e., SEQ ID NO: 130); (xvi) helix 4 of SEQ ID NO: 9 (Cage 9) (i.e., SEQ ID NO: 131); (xvii) helix 4 of SEQ ID NO: 10 (Cage 10) (i.e., SEQ ID NO: 132); (xviii) helix 4 of SEQ ID NO: 11 (Cage 11) (i.e., SEQ ID NO: 133); (xix) helix 4 of SEQ ID NO: 12 (Cage 12 ) (i.e., SEQ ID NO: 135). SEQ ID NOs for the different helices are also provided in Tables 1 and 2. [0173] In some aspects, the latch region comprises at least 5, at least 10, at least 15, at least 20, at least 25, at least 30, at least 35, at least 40, at least 45, at least 50, at least 55, or at least 60 consecutive amino acids from helix 3 of the amino acid sequence set forth in SEQ ID NO: 13 (Cage 13) {i.e., SEQ ID NO: 115), SEQ ID NO: 14 (Cage 14) {i.e., SEQ ID NO: 116), SEQ ID NO: 15 (Cage 15) {i.e., SEQ ID NO: 117), SEQ ID NO: 16 (Cage 16) {i.e., SEQ ID NO: 118), SEQ ID NO: 17 (Cage 17) {i.e., SEQ ID NO: 119), SEQ ID NO: 18 (Cage 18) {i.e., SEQ ID NO: 120); or helix 4 of the amino acid sequence set forth in SEQ ID NO: 1 (Cage 1) {i.e., SEQ ID NO: 121), SEQ ID NO: 2 (Cage 2) {i.e., SEQ ID NO: 122), SEQ ID NO: 3 (Cage 3) {i.e., SEQ ID NO: 124), SEQ ID NO: 4 (Cage 4) {i.e., SEQ ID NO: 125), SEQ ID NO: 5 (Cage 5) {i.e., SEQ ID NO: 127), SEQ ID NO: 6 (Cage 6) {i.e., SEQ ID NO: 128), SEQ ID NO: 7 (Cage 7) {i.e., SEQ ID NO: 129), SEQ ID NO: 8 (Cage 8) {i.e., SEQ ID NO: 130), SEQ ID NO: 9 (Cage 9) {i.e., SEQ ID NO: 131), SEQ ID NO: 10 (Cage 10) {i.e., SEQ ID NO: 132), SEQ ID NO: 11 (Cage 11) {i.e., SEQ ID NO: 133), SEQ ID NO: 12 (Cage 12) {i.e., SEQ ID NO: 135). SEQ ID NOs for the different helices are also provided in Tables 1 and 2.

[0174] In some aspects, a chimeric polypeptide of the present disclosure comprises an amino acid sequence having at least about 50%, at least about 60%, at least about 70%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to helix 1 and/or helix 2 of SEQ ID NO: 13 (Cage 13) {i.e., SEQ ID NOs: 40 and 41, respectively). In some aspects, the latch region of a chimeric polypeptide disclosed herein comprises an amino acid sequence having at least about 50%, at least about 60%, at least about 70%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to helix 3 of SEQ ID NO: 13 (Cage 13 ) {i.e., SEQ ID NO: 115).

[0175] some aspects, a chimeric polypeptide of the present disclosure comprises an amino acid sequence having at least about 50%, at least about 60%, at least about 70%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to helix 1 and/or helix 2 of SEQ ID NO: 14 (Cage 14) {i.e., SEQ ID NOs: 40 and 41, respectively). In some aspects, the latch region of a chimeric polypeptide disclosed herein comprises an amino acid sequence having at least about 50%, at least about 60%, at least about 70%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to helix 3 of SEQ ID NO: 14 (Cage 14) (i.e., SEQ ID NO: 116).

[0176] In some aspects, a chimeric polypeptide of the present disclosure comprises an amino acid sequence having at least about 50%, at least about 60%, at least about 70%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to helix 1 and/or helix 2 of SEQ ID NO: 15 (Cage 15) (i.e., SEQ ID NOs: 43 and 44, respectively). In some aspects, the latch region of a chimeric polypeptide disclosed herein comprises an amino acid sequence having at least about 50%, at least about 60%, at least about 70%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to helix 3 of SEQ ID NO: 15 (Cage 15) (i.e., SEQ ID NO: 117).

[0177] In some aspects, a chimeric polypeptide of the present disclosure comprises an amino acid sequence having at least about 50%, at least about 60%, at least about 70%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to helix 1 and/or helix 2 of SEQ ID NO: 16 (Cage 16) (i.e., SEQ ID NOs: 46 and 47, respectively). In some aspects, the latch region of a chimeric polypeptide disclosed herein comprises an amino acid sequence having at least about 50%, at least about 60%, at least about 70%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to helix 3 of SEQ ID NO: 16 (Cage 16) (i.e., SEQ ID NO: 118).

[0178] In some aspects, a chimeric polypeptide of the present disclosure comprises an amino acid sequence having at least about 50%, at least about 60%, at least about 70%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to helix 1 and/or helix 2 of SEQ ID NO: 17 (Cage 17) (i.e., SEQ ID NOs: 49 and 50, respectively). In some aspects, the latch region of a chimeric polypeptide disclosed herein comprises an amino acid sequence having at least about 50%, at least about 60%, at least about 70%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to helix 3 of SEQ ID NO: 17 (Cage 17) (i.e., SEQ ID NO: 119). [0179] In some aspects, a chimeric polypeptide of the present disclosure comprises an amino acid sequence having at least about 50%, at least about 60%, at least about 70%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to helix 1 and/or helix 2 of SEQ ID NO: 18 (Cage 18) ( i.e ., SEQ ID NOs: 52 and 53, respectively). In some aspects, the latch region of a chimeric polypeptide disclosed herein comprises an amino acid sequence having at least about 50%, at least about 60%, at least about 70%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to helix 3 of SEQ ID NO: 18 (Cage 18) (i.e., SEQ ID NO: 120).

[0180] In some aspects, a chimeric polypeptide of the present disclosure comprises an amino acid sequence having at least about 50%, at least about 60%, at least about 70%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to helix 1, helix 2, and/or helix 3 of SEQ ID NO: 1 (Cage 1) (i.e., SEQ ID NOs: 55-57, respectively). In some aspects, the latch region of a chimeric polypeptide disclosed herein comprises an amino acid sequence having at least about 50%, at least about 60%, at least about 70%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to helix 4 of SEQ ID NO: 1 (Cage 1) (i.e., SEQ ID NO: 121).

[0181] In some aspects, a chimeric polypeptide of the present disclosure comprises an amino acid sequence having at least about 50%, at least about 60%, at least about 70%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to helix 1, helix 2, and/or helix 3 of SEQ ID NO: 2 (Cage 2) (i.e., SEQ ID NOs: 59-61, respectively). In some aspects, the latch region of a chimeric polypeptide disclosed herein comprises an amino acid sequence having at least about 50%, at least about 60%, at least about 70%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to helix 4 of SEQ ID NO: 2 (Cage 2) (i.e., SEQ ID NO: 122).

[0182] In some aspects, a chimeric polypeptide of the present disclosure comprises an amino acid sequence having at least about 50%, at least about 60%, at least about 70%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to helix 1, helix 2, and/or helix 3 of SEQ ID NO: 3 (Cage 3) ( i.e ., SEQ ID NOs: 63-65, respectively). In some aspects, the latch region of a chimeric polypeptide disclosed herein comprises an amino acid sequence having at least about 50%, at least about 60%, at least about 70%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to helix 4 of SEQ ID NO: 3 (Cage 3) (i.e., SEQ ID NO: 124).

[0183] In some aspects, a chimeric polypeptide of the present disclosure comprises an amino acid sequence having at least about 50%, at least about 60%, at least about 70%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to helix 1, helix 2, and/or helix 3 of SEQ ID NO: 4 (Cage 4) (i.e., SEQ ID NOs: 71-73, respectively). In some aspects, the latch region of a chimeric polypeptide disclosed herein comprises an amino acid sequence having at least about 50%, at least about 60%, at least about 70%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to helix 4 of SEQ ID NO: 4 (Cage 4) (i.e., SEQ ID NO: 125).

[0184] In some aspects, a chimeric polypeptide of the present disclosure comprises an amino acid sequence having at least about 50%, at least about 60%, at least about 70%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to helix 1, helix 2, and/or helix 3 of SEQ ID NO: 5 (Cage 5) (i.e., SEQ ID NOs: 79-81, respectively). In some aspects, the latch region of a chimeric polypeptide disclosed herein comprises an amino acid sequence having at least about 50%, at least about 60%, at least about 70%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to helix 4 of SEQ ID NO: 5 (Cage 5) (i.e., SEQ ID NO: 127).

[0185] In some aspects, a chimeric polypeptide of the present disclosure comprises an amino acid sequence having at least about 50%, at least about 60%, at least about 70%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to helix 1, helix 2, and/or helix 3 of SEQ ID NO: 6 (Cage 6) (i.e., SEQ ID NOs: 83-85, respectively). In some aspects, the latch region of a chimeric polypeptide disclosed herein comprises an amino acid sequence having at least about 50%, at least about 60%, at least about 70%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to helix 4 of SEQ ID NO: 6 (Cage 6) (i.e., SEQ ID NO: 128).

[0186] In some aspects, a chimeric polypeptide of the present disclosure comprises an amino acid sequence having at least about 50%, at least about 60%, at least about 70%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to helix 1, helix 2, and/or helix 3 of SEQ ID NO: 7 (Cage 7) (i.e., SEQ ID NOs: 87-89, respectively). In some aspects, the latch region of a chimeric polypeptide disclosed herein comprises an amino acid sequence having at least about 50%, at least about 60%, at least about 70%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to helix 4 of SEQ ID NO: 7 (Cage 7) (i.e., SEQ ID NO: 129).

[0187] In some aspects, a chimeric polypeptide of the present disclosure comprises an amino acid sequence having at least about 50%, at least about 60%, at least about 70%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to helix 1, helix 2, and/or helix 3 of SEQ ID NO: 8 (Cage 8) (i.e., SEQ ID NOs: 91-93, respectively). In some aspects, the latch region of a chimeric polypeptide disclosed herein comprises an amino acid sequence having at least about 50%, at least about 60%, at least about 70%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to helix 4 of SEQ ID NO: 8 (Cage 8) (i.e., SEQ ID NO: 130).

[0188] In some aspects, a chimeric polypeptide of the present disclosure comprises an amino acid sequence having at least about 50%, at least about 60%, at least about 70%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to helix 1, helix 2, and/or helix 3 of SEQ ID NO: 9 (Cage 9) (i.e., SEQ ID NOs: 95-97, respectively). In some aspects, the latch region of a chimeric polypeptide disclosed herein comprises an amino acid sequence having at least about 50%, at least about 60%, at least about 70%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to helix 4 of SEQ ID NO: 9 (Cage 9) (i.e., SEQ ID NO: 131).

[0189] In some aspects, a chimeric polypeptide of the present disclosure comprises an amino acid sequence having at least about 50%, at least about 60%, at least about 70%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to helix 1, helix 2, and/or helix 3 of SEQ ID NO: 10 (Cage 10) (i.e., SEQ ID NOs: 99-101, respectively). In some aspects, the latch region of a chimeric polypeptide disclosed herein comprises an amino acid sequence having at least about 50%, at least about 60%, at least about 70%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to helix 4 of SEQ ID NO: 10 (Cage 10) (i.e., SEQ ID NO: 132).

[0190] In some aspects, a chimeric polypeptide of the present disclosure comprises an amino acid sequence having at least about 50%, at least about 60%, at least about 70%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to helix 1, helix 2, and/or helix 3 of SEQ ID NO: 11 (Cage l l) (z.e., SEQ ID NOs: 103-105, respectively). In some aspects, the latch region of a chimeric polypeptide disclosed herein comprises an amino acid sequence having at least about 50%, at least about 60%, at least about 70%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to helix 4 of SEQ ID NO: 11 (Cage 11) (i.e., SEQ ID NO: 133).

[0191] In some aspects, a chimeric polypeptide of the present disclosure comprises an amino acid sequence having at least about 50%, at least about 60%, at least about 70%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to helix 1, helix 2, and/or helix 3 of SEQ ID NO: 12 (Cage 12) (i.e., SEQ ID NOs: 111-113, respectively). In some aspects, the latch region of a chimeric polypeptide disclosed herein comprises an amino acid sequence having at least about 50%, at least about 60%, at least about 70%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to helix 4 of SEQ ID NO: 12 (Cage 12) (i.e., SEQ ID NO: 135).

[0192] As described above, the cage polypeptide of a chimeric polypeptide disclosed herein can be used to sequester a degron ( e.g ., a degron comprising, consisting of, or consisting essentially of the amino acid CGL) in the cage polypeptide, holding the degron in an inactive (“off’) state, until combined with an activation component (the “key” polypeptide). Due to the binding of the key polypeptide to the cage polypeptide, the degron can be exposed and now be active (“on”).

[0193] In some aspects, the alpha helices of a cage polypeptide are joined by one or more linkers. The amino acid linkers connecting each alpha helix can be of any suitable length and/or amino acid composition as appropriate for an intended use (e.g., to effectively sequester a degron of the present disclosure, e.g, a degron comprising, consisting of, or consisting essentially of the amino acid CGL). In some aspects, each amino acid linker is independently between 2 and 10 amino acids in length, not including any further functional sequences that can be fused to the linker. In some aspects, each amino acid linker is independently 3-10, 4-10, 5-10, 6-10, 7-10, 8-10, 9-10, 2-9, 3-9, 4-9, 5-9, 6-9, 7-9, 8-9, 2-8, 3-8, 4-8, 5-8, 6-8, 7-8, 2-7, 3-7, 4-7, 5-7, 6-7, 2-6, 3-6, 4-6, 5-6, 2-5, 3-5, 4-5, 2-4, 3-4, 2-3. In some aspects, the cage polypeptide comprises one linker, two linkers, three linkers, four linkers, five linkers, or six linkers. In some aspects, one or more linkers in the cage polypeptide is 2, 3, 4, 5, 6, 7, 8, 9, or 10 amino acids in length.

[0194] In some aspects, the linkers can be structured or flexible (e.g, poly-GS). In certain aspects, these linkers can encode further functional sequences, including but not limited to protease cleavage sites or one half of a split intein system. As described herein, in some aspects, linkers can further comprise one or more functional polypeptide domains — in such aspects, the linkers can be of any size suitable to include the one or more functional polypeptide domains, while maintaining the ability of the structural region and the latch region to interact.

[0195] Suitable linkers can be readily selected and can be of any of a number of suitable lengths, such as from 1 amino acid (e.g, Gly) to 20 amino acids, from 2 amino acids to 15 amino acids, from 3 amino acids to 12 amino acids, including 4 amino acids to 10 amino acids, 5 amino acids to 9 amino acids, 6 amino acids to 8 amino acids, or 7 amino acids to 8 amino acids, and can be 1, 2, 3, 4, 5, 6, or 7 amino acids. [0196] Exemplary linkers include glycine polymers (G)n, glycine-serine polymers (including, for example, (GS)n, (GSGGS)n (SEQ ID NO: 143) and (GGGS)n (SEQ ID NO: 144), where n is an integer of at least one), glycine-alanine polymers, alanine-serine polymers, and other flexible linkers known in the art. Glycine and glycine-serine polymers can be used; both Gly and Ser are relatively unstructured, and therefore can serve as a neutral tether between components. Glycine polymers can be used; glycine accesses significantly more phi-psi space than even alanine, and is much less restricted than residues with longer side chains (see Scheraga, Rev. Computational Chem. 11173-142 (1992)). Exemplary linkers can comprise amino acid sequences including, but not limited to, GGSG (SEQ ID NO: 145), GGSGG (SEQ ID NO: 146), GSGSG (SEQ ID NO: 147), GSGGG (SEQ ID NO: 148), GGGSG (SEQ ID NO: 149), GSSSG (SEQ ID NO: 150), and the like.

[0197] While the above linkers are described in the context of joining two or more alpha helices of a cage polypeptide, it will be apparent to those skilled in the art the such linkers can be used to link any two or more polypeptides present in a chimeric polypeptide of the present disclosure.

[0198] In some aspects, a cage polypeptide of a chimeric polypeptide disclosed herein comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 13 (Cage 13); SEQ ID NO: 14 (Cage 14); SEQ ID NO: 15 (Cage 15); SEQ ID NO: 16 (Cage 16); SEQ ID NO: 17 (Cage 17); SEQ ID NO: 18 (Cage 18); SEQ ID NO: 1 (Cage 1); SEQ ID NO: 2 (Cage 2); SEQ ID NO: 3 (Cage 3); SEQ ID NO: 4 (Cage 4); SEQ ID NO: 5 (Cage 5); SEQ ID NO: 6 (Cage 6); SEQ ID NO: 7 (Cage 7); SEQ ID NO: 8 (Cage 8); SEQ ID NO: 9 (Cage 9); SEQ ID NO: 10 (Cage 10); SEQ ID NO: 11 (Cage 11); or SEQ ID NO: 12 (Cage 12).

[0199] In some aspects, a cage polypeptide disclosed herein comprises the amino acid sequence set forth in SEQ ID NO: 13 (Cage 13). In some aspects, a cage polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 14 (Cage 14). In some aspects, a cage polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 15 (Cage 15). In some aspects, a cage polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 16 (Cage 16). In some aspects, a cage polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 17 (Cage 17). In some aspects, a cage polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 18 (Cage 18). In some aspects, a cage polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 1 (Cage 1). In some aspects, a cage polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 2 (Cage 2). In some aspects, a cage polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 3 (Cage 3). In some aspects, a cage polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 4 (Cage 4). In some aspects, a cage polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 5 (Cage 5). In some aspects, a cage polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 6 (Cage 6). In some aspects, a cage polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 7 (Cage 7). In some aspects, a cage polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 8 (Cage 8). In some aspects, a cage polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 9 (Cage 9). In some aspects, a cage polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 10 (Cage 10). In some aspects, a cage polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 11 (Cage 11). In some aspects, a cage polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 12 (Cage 12).

[0200] In some aspects, a cage polypeptide disclosed herein comprises the amino acid sequence set forth in SEQ ID NO: 13 (Cage 13) or an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% sequence identity to SEQ ID NO: 13, wherein the amino acid sequence is capable of preferentially binding to a key polypeptide comprising the amino acid sequence consisting of SEQ ID NO: 31 (Key 13).

[0201] In some aspects, a cage polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 14 (Cage 14) or an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% sequence identity to SEQ ID NO: 14, wherein the amino acid sequence is capable of preferentially binding to a key polypeptide comprising the amino acid sequence consisting of SEQ ID NO: 31 (Key 14).

[0202] In some aspects, a cage polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 15 (Cage 15) or an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% sequence identity to SEQ ID NO:

15, wherein the amino acid sequence is capable of preferentially binding to a key polypeptide comprising the amino acid sequence consisting of SEQ ID NO: 32 (Key 15).

[0203] In some aspects, a cage polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 16 (Cage 16)or an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% sequence identity to SEQ ID NO:

16, wherein the amino acid sequence is capable of preferentially binding to a key polypeptide comprising the amino acid sequence consisting of SEQ ID NO: 33 (Key 16).

[0204] In some aspects, a cage polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 17 (Cage 17) or an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% sequence identity to SEQ ID NO:

17, wherein the amino acid sequence is capable of preferentially binding to a key polypeptide comprising the amino acid sequence consisting of SEQ ID NO: 34 (Key 17).

[0205] In some aspects, a cage polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 18 (Cage 18) or an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% sequence identity to SEQ ID NO:

18, wherein the amino acid sequence is capable of preferentially binding to a key polypeptide comprising the amino acid sequence consisting of SEQ ID NO: 35 (Key 18). [0206] In some aspects, a cage polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 1 (Cage 1) or an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% sequence identity to SEQ ID NO: 1, wherein the amino acid sequence is capable of preferentially binding to a key polypeptide comprising the amino acid sequence consisting of SEQ ID NO: 19 (Key 1).

[0207] In some aspects, a cage polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 2 (Cage 2) or an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% sequence identity to SEQ ID NO: 2, wherein the amino acid sequence is capable of preferentially binding to a key polypeptide comprising the amino acid sequence consisting of SEQ ID NO: 20 (Key 2).

[0208] In some aspects, a cage polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 3 (Cage 3) or an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% sequence identity to SEQ ID NO: 3, wherein the amino acid sequence is capable of preferentially binding to a key polypeptide comprising the amino acid sequence consisting of SEQ ID NO: 21 (Key 3).

[0209] In some aspects, a cage polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 4 (Cage 4) or an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% sequence identity to SEQ ID NO: 4, wherein the amino acid sequence is capable of preferentially binding to a key polypeptide comprising the amino acid sequence consisting of SEQ ID NO: 22 (Key 4).

[0210] In some aspects, a cage polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 5 (Cage 5) or an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% sequence identity to SEQ ID NO: 5, wherein the amino acid sequence is capable of preferentially binding to a key polypeptide comprising the amino acid sequence consisting of SEQ ID NO: 23 (Key 5).

[0211] In some aspects, a cage polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 6 (Cage 6) or an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% sequence identity to SEQ ID NO: 6, wherein the amino acid sequence is capable of preferentially binding to a key polypeptide comprising the amino acid sequence consisting of SEQ ID NO: 24 (Key 6).

[0212] In some aspects, a cage polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 7 (Cage 7) or an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% sequence identity to SEQ ID NO: 7, wherein the amino acid sequence is capable of preferentially binding to a key polypeptide comprising the amino acid sequence consisting of SEQ ID NO: 25 (Key 7).

[0213] In some aspects, a cage polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 8 (Cage 8) or an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% sequence identity to SEQ ID NO: 8, wherein the amino acid sequence is capable of preferentially binding to a key polypeptide comprising the amino acid sequence consisting of SEQ ID NO: 26 (Key 8).

[0214] In some aspects, a cage polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 9 (Cage 9) or an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% sequence identity to SEQ ID NO: 9, wherein the amino acid sequence is capable of preferentially binding to a key polypeptide comprising the amino acid sequence consisting of SEQ ID NO: 27 (Key 9).

[0215] In some aspects, a cage polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 10 (Cage 10) or an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% sequence identity to SEQ ID NO:

10, wherein the amino acid sequence is capable of preferentially binding to a key polypeptide comprising the amino acid sequence consisting of SEQ ID NO: 28 (Key 10).

[0216] In some aspects, a cage polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 11 (Cage 11) or an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% sequence identity to SEQ ID NO:

11, wherein the amino acid sequence is capable of preferentially binding to a key polypeptide comprising the amino acid sequence consisting of SEQ ID NO: 29 (Key 11).

[0217] In some aspects, a polynucleotide encodes a cage polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 12 (Cage 12) or an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% sequence identity to SEQ ID NO: 12, wherein the amino acid sequence is capable of preferentially binding to a key polypeptide comprising the amino acid sequence consisting of SEQ ID NO: 30 (Key 12).

II. b. Degron Peptide

[0218] As described herein, a chimeric polypeptide of the present disclosure comprises a degron peptide, wherein the degron peptide is inserted immediately after the C-terminal residue of the latch region (/. ., linked or attached to the C-terminus) of the cage polypeptide. In some aspects, the C-terminal end of the latch region is modified prior to the insertion of the degron motif, such that the degron motif is properly displayed in the chimeric polypeptide. In certain aspects, modifying the C-terminal end of the latch region comprises the removal of one or more amino acids naturally present at the C-terminal end of the latch region. Unless indicated otherwise, the term “latch region,” as used herein, can refer to both a modified latch region (i.e., one or more amino acids at the C-terminal end of the latch region has been removed) and a non-modified latch region. As used herein, a “degron” is a peptide capable of targeting the cage polypeptide and any functional polypeptide domain fused to the cage polypeptide for degradation. In some aspects, the degron is a ubiquitin-dependent degron, i.e., a polypeptide recognized by an ubiquitin ligase which enzymatically attaches a ubiquitin protein to the degron, which marks the degron and any polypeptide ( e.g ., a CAR or TCR) attached to the degron for degradation/targeting to the proteasome.

[0219] Cytosolic proteins are predominantly regulated through proteasomal degradation, including direct recruitment to the proteasome by degradation motifs such as found in mouse ornithine decarboxylase. Bhattacharyya S, Yu H, Mim C, Matouschek A. 2014. Nat Rev Mol Cell Biol 15:122-133; Takeuchi J, Chen H, Hoyt MA, Coffino P. 2008. Biochem J. 2008 Mar l;410(2):401-7, each of which is incorporated herein by reference in its entirety. In contrast, membrane proteins are predominantly degraded through endo-lysosomal mechanisms or via autophagy. Luzio JP, Pryor PR, Bright NA. 2007. Lysosomes: Fusion and function. Nat Rev Mol Cell Biol 8:622-632, which is incorporated herein by reference in its entirety. The present disclosure shows that when a CGL degron peptide is linked to a Cage polypeptide of the present disclosure and is then activated, the CGL degron peptide is capable of degrading membrane proteins. However, a C-terminal degron of mouse ornithine decarboxylase (cODC) is not capable of degrading membrane proteins (e.g., CARs expressed on T cells) (see, e.g, Example 2; FIG. 5C). Accordingly, compared to motifs such as cODC, the degron peptides disclosed herein (e.g, CGL) allow for one or more improved properties when integrated into a chimeric polypeptide of the present disclosure. For example, in some aspects, integrating the CGL degron peptides disclosed herein at the C-terminal end of a CAR or TCR results in greater downregulation of CAR or TCR expression. In certain aspects, downregulation of the expression of a CAR or TCR comprising a CGL degron peptide is greater than about 0.5-fold, greater than about 1-fold, greater than about 2-fold, greater than about 3 -fold, greater than about 4-fold, greater than about 5-fold, greater than about 10-fold, greater than about 20-fold, greater than about 25-fold, greater than about 30-fold, greater than about 35-fold, greater than about 40-fold, greater than about 45-fold, greater than about 50-fold, greater than about 75- fold, or greater than about 100-fold or more, compared to the expression of a corresponding CAR or TCR comprising a cODC. [0220] As described herein, the ability to decrease CAR or TCR expression can improve one or more aspects of an immune response. For example the greater downregulation of CAR or TCR on an immune cells ( e.g ., T cells) can reduce the exhaustion of the immune cell. Accordingly, in certain aspects, immune cells (e.g., T cells) expressing CARs or TCRs comprising the CGL degron peptide of the present disclosure are less exhausted compared to reference immune cells expressing CARs or TCRs that do not comprise the CGL degron peptide (e.g, comprises cODC). In some aspects, exhaustion of the immune cells is reduced by at least about 5%, at least about 10%, at least about 20%, at least about 30%, at least about 40%, at least about 50%, at least about 60%, at least about 70%, at least about 80%, at least about 90%, or about 100% compared to the reference immune cells.

[0221] In some aspects, a chimeric polypeptide disclosed herein comprises a single degron peptide linked to the C-terminus of the latch region. In further aspects, a chimeric polypeptide disclosed herein can comprise two or more degron peptides, wherein at least one of the degron peptides is linked to the C-terminus of the latch region. In certain aspects, the additional degron peptides are within the latch region of the cage polypeptide, which is C-terminal to the structural region of the cage polypeptide.

[0222] When a key polypeptide is expressed or administered and activates the cage polypeptide by interacting with the structural region, the degron targets the cage polypeptide, and any functional polypeptide domains and/or additional bioactive domain fused to the cage polypeptide, for degradation. In this way, a functional polypeptide domain of interest (e.g, a CAR or TCR) fused to a cage polypeptide having a degron (e.g, a degron comprising, consisting, or consisting essentially of the amino acid CGL) can be conditionally degraded in a titratable manner via expression of the key.

[0223] In some aspects, a degron peptide comprises, consists, or consists essentially of the amino acid sequence of CGL, YCGL (SEQ ID NO: 136), TYCGL (SEQ ID NO: 137), VTYCGL (SEQ ID NO: 138), RVTYCGL (SEQ ID NO: 139), IRVTYCGL (SEQ ID NO: 140), LIR VTYCGL (SEQ ID NO: 141), or VLIR VTYCGL (SEQ ID NO: 142). In certain aspects, the degron peptide useful for the chimeric polypeptide comprises, consists, or consists essentially of an amino acid sequence that is at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 80%, at least about 90%, or about 100% identical to VLIR VTYCGL (SEQ ID NO: 142). [0224] In some aspects, the degron peptide comprises the amino acid sequence of CGL. In some aspects, the degron peptide comprises the amino acid sequence of YCGL (SEQ ID NO: 136). In some aspects, the degron peptide comprises the amino acid sequence of TYCGL (SEQ ID NO: 137). In some aspects, the degron peptide comprises the amino acid sequence of VTYCGL (SEQ ID NO: 138). In some aspects, the degron peptide comprises the amino acid sequence of RVTYCGL (SEQ ID NO: 139). In some aspects, the degron peptide comprises the amino acid sequence of IRVTYCGL (SEQ ID NO: 140). In some aspects, the degron peptide comprises the amino acid sequence of LIR VTYCGL (SEQ ID NO: 141). In some aspects, the degron peptide comprises the amino acid sequence of VLIR VTYCGL (SEQ ID NO: 142).

[0225] In some aspects, the degron peptide consists or consists essentially of the amino acid sequence of CGL. In some aspects, the degron peptide consists or consists essentially of the amino acid sequence of YCGL (SEQ ID NO: 136). In some aspects, the degron peptide consists or consists essentially of the amino acid sequence of TYCGL (SEQ ID NO: 137). In some aspects, the degron peptide consists or consists essentially of the amino acid sequence of VTYCGL (SEQ ID NO: 138). In some aspects, the degron peptide consists or consists essentially of the amino acid sequence of RVTYCGL (SEQ ID NO: 139). In some aspects, the degron peptide consists or consists essentially of the amino acid sequence of IRVTYCGL (SEQ ID NO: 140). In some aspects, the degron peptide consists or consists essentially of the amino acid sequence of LIRVTYCGL (SEQ ID NO: 141). In some aspects, the degron peptide consists or consists essentially of the amino acid sequence of VLIR VTYCGL (SEQ ID NO: 142).

[0226] In some aspects, the degron peptide useful for the chimeric polypeptide of the present disclosure comprises, consists, or consists essentially of an amino acid sequence that is at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 71%, at least about 72%, at least about 73%, at least about 74%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% identical to SEQ ID NO: 142 (VLIRVTYCGL). [0227] As described herein, in some aspects, the latch region is modified prior to inserting the degron peptide at the C-terminus of the latch region. In certain aspects, one or more amino acid residues at the C-terminal end of the latch region is removed prior to inserting the degron peptide at the C-terminus of the latch region. In some aspects, at least one, at least two, at least three, at least four, at least five, at least six, at least seven, at least eight, at least nine, at least ten, at least eleven, or at least twelve amino acid residues are removed from the C-terminal end of a latch region prior to inserting the degron peptide at the C-terminus of the latch region.

[0228] In some aspects, the latch region comprises the amino acid sequence set forth in SEQ ID NO: 42 (z.e., helix 3 of scaffold 13 or 14) and wherein, at least one or more amino acids of the sequence RDVDKKARDRKK (SEQ ID NO: 151) are removed prior to inserting the degron peptide at the C-terminus of the latch region. In certain aspects, the amino acid “K” at the C-terminal end of SEQ ID NO: 42 is removed prior to inserting the degron peptide at the C-terminus of the latch region. In some aspects, the amino acid sequence “KK” at the C- terminal end of SEQ ID NO: 42 is removed prior to inserting the degron peptide at the C- terminus of the latch region. In some aspects, the amino acid sequence “RKK” at the C-terminal end of SEQ ID NO: 42 is removed prior to inserting the degron peptide at the C-terminus of the latch region. In some aspects, the amino acid sequence “DRKK” (SEQ ID NO: 152) at the C-terminal end of SEQ ID NO: 42 is removed prior to inserting the degron peptide at the C- terminus of the latch region. In some aspects, the amino acid sequence “RDRKK” (SEQ ID NO: 153) at the C-terminal end of SEQ ID NO: 42 is removed prior to inserting the degron peptide at the C-terminus of the latch region. In some aspects, the amino acid sequence “ARDRKK” (SEQ ID NO: 154) at the C-terminal end of SEQ ID NO: 42 is removed prior to inserting the degron peptide at the C-terminus of the latch region. In some aspects, the amino acid sequence “KARDRKK” (SEQ ID NO: 155) at the C-terminal end of SEQ ID NO: 42 is removed prior to inserting the degron peptide at the C-terminus of the latch region. In some aspects, the amino acid sequence “KKARDRKK” (SEQ ID NO: 156) at the C-terminal end of SEQ ID NO: 42 is removed prior to inserting the degron peptide at the C-terminus of the latch region. In some aspects, the amino acid sequence “DKKARDRKK” (SEQ ID NO: 157) at the C-terminal end of SEQ ID NO: 42 is removed prior to inserting the degron peptide at the C- terminus of the latch region. In some aspects, the amino acid sequence “VDKKARDRKK” (SEQ ID NO: 158) at the C-terminal end of SEQ ID NO: 42 is removed prior to inserting the degron peptide at the C-terminus of the latch region. In some aspects, the amino acid sequence “DVDKK ARDRKK” (SEQ ID NO: 159) at the C-terminal end of SEQ ID NO: 42 is removed prior to inserting the degron peptide at the C-terminus of the latch region. In some aspects, the amino acid sequence “RDVDKKARDRKK” (SEQ ID NO: 151) at the C-terminal end of SEQ ID NO: 42 is removed prior to inserting the degron peptide at the C-terminus of the latch region.

[0229] In some aspects, a degron peptide of a chimeric polypeptide disclosed herein is linked to the C-terminus of helix 3 of Cage 13 as set forth in SEQ ID NO: 115. In some aspects, the degron peptide is linked to the C-terminus of helix 3 of Cage 14 as set forth in SEQ ID NO: 116. In some aspects, the degron peptide is linked to the C-terminus of helix 3 of Cage 15 as set forth in SEQ ID NO: 117. In some aspects, the degron peptide is linked to the C-terminus of helix 3 of Cage 16 as set forth in SEQ ID NO: 118. In some aspects, the degron peptide is linked to the C-terminus of helix 3 of Cage 17 as set forth in SEQ ID NO: 119. In some aspects, the degron peptide is linked to the C-terminus of helix 3 of Cage 18 as set forth in SEQ ID NO: 120. In some aspects, the degron peptide is linked to the C-terminus of helix 4 of Cage 1 as set forth in SEQ ID NO: 121. In some aspects, the degron peptide is linked to the C-terminus of helix 4 of Cage 2 as set forth in SEQ ID NO: 122. In some aspects, the degron peptide is linked to the C-terminus of helix 4 of Cage 3 as set forth in SEQ ID NO: 124. In some aspects, the degron peptide is linked to the C-terminus helix 4 of Cage 4 as set forth in SEQ ID NO: 125. In some aspects, the degron peptide is linked to the C-terminus of helix 4 of Cage 5 as set forth in SEQ ID NO: 127. In some aspects, the degron peptide is linked to the C-terminus of helix 4 of Cage 6 as set forth in SEQ ID NO: 128. In some aspects, the degron peptide is linked to the C-terminus of helix 4 of Cage 7 as set forth in SEQ ID NO: 129. In some aspects, the degron peptide is linked to the C-terminus of helix 4 of Cage 8 as set forth in SEQ ID NO: 130. In some aspects, the degron peptide is linked to the C-terminus of helix 4 of Cage 9 as set forth in SEQ ID NO: 131. In some aspects, the degron peptide is linked to the C-terminus of helix 4 of Cage 10 as set forth in SEQ ID NO: 132. In some aspects, the degron peptide is linked to the C-terminus of helix 4 of Cage 11 as set forth in SEQ ID NO: 133. In some aspects, the degron peptide is linked to the C-terminus of helix 4 of Cage 12 as set forth SEQ ID NO: 135. In some aspects, the degron peptide is linked to the C-terminus of helix 4 of Cage 19 as set forth in SEQ ID NO: 123. In some aspects, the degron peptide is linked to the C-terminus of helix 4 of Cage 20 as set forth in SEQ ID NO: 126. In some aspects, the degron peptide is linked to the C-terminus of helix 4 of Cage 21 as set forth in SEQ ID NO: 134.

[0230] In some aspects, a chimeric polypeptide of the present disclosure comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 1 (Cage 1), wherein the chimeric polypeptide is capable of preferentially binding to the key polypeptide consisting of SEQ ID NO: 19 (Key 1), and upon binding to the key polypeptide, is capable of being degraded by a ubiquitin dependent pathway. In certain aspects, the chimeric polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 1 (Cage 1).

[0231] In some aspects, a chimeric polypeptide of the present disclosure consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 1 (Cage 1), wherein the chimeric polypeptide is capable of preferentially binding to the key polypeptide consisting of SEQ ID NO: 19 (Key 1), and upon binding to the key polypeptide, is capable of being degraded by a ubiquitin dependent pathway. In certain aspects, chimeric polypeptide consists or consists essentially of the amino acid sequence set forth in SEQ ID NO: 1 (Cage 1).

[0232] In some aspects, a chimeric polypeptide of the present disclosure comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 2 (Cage 2), wherein the chimeric polypeptide is capable of preferentially binding to the key polypeptide consisting of SEQ ID NO: 20 (Key 2), and upon binding to the key polypeptide, is capable of being degraded by a ubiquitin dependent pathway. In certain aspects, chimeric polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 2 (Cage 2).

[0233] In some aspects, a chimeric polypeptide of the present disclosure consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 2 (Cage 2), wherein the chimeric polypeptide is capable of preferentially binding to the key polypeptide consisting of SEQ ID NO: 20 (Key 2), and upon binding to the key polypeptide, is capable of being degraded by a ubiquitin dependent pathway. In certain aspects, chimeric polypeptide consists or consists essentially of the amino acid sequence set forth in SEQ ID NO: 2 (Cage 2).

[0234] In some aspects, a chimeric polypeptide of the present disclosure comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 3 (Cage 3), wherein the chimeric polypeptide is capable of preferentially binding to the key polypeptide consisting of SEQ ID NO: 21 (Key 3), and upon binding to the key polypeptide, is capable of being degraded by a ubiquitin dependent pathway. In certain aspects, the chimeric polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 3 (Cage 3). [0235] In some aspects, a chimeric polypeptide of the present disclosure consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 3 (Cage 3), wherein the chimeric polypeptide is capable of preferentially binding to the key polypeptide consisting of SEQ ID NO: 21 (Key 3), and upon binding to the key polypeptide, is capable of being degraded by a ubiquitin dependent pathway. In certain aspects, chimeric polypeptide consists or consists essentially of the amino acid sequence set forth in SEQ ID NO: 3 (Cage 3).

[0236] In some aspects, a chimeric polypeptide of the present disclosure comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 4 (Cage 4), wherein the chimeric polypeptide is capable of preferentially binding to the key polypeptide consisting of SEQ ID NO: 22 (Key 4), and upon binding to the key polypeptide, is capable of being degraded by a ubiquitin dependent pathway. In certain aspects, chimeric polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 4 (Cage 4).

[0237] In some aspects, a chimeric polypeptide of the present disclosure consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 4 (Cage 4), wherein the chimeric polypeptide is capable of preferentially binding to the key polypeptide consisting of SEQ ID NO: 22 (Key 4), and upon binding to the key polypeptide, is capable of being degraded by a ubiquitin dependent pathway. In certain aspects, chimeric polypeptide consists or consists essentially of the amino acid sequence set forth in SEQ ID NO: 4 (Cage 4).

[0238] In some aspects, a chimeric polypeptide of the present disclosure comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 5 (Cage 5), wherein the chimeric polypeptide is capable of preferentially binding to the key polypeptide consisting of SEQ ID NO: 23 (Key 5), and upon binding to the key polypeptide, is capable of being degraded by a ubiquitin dependent pathway. In certain aspects, chimeric polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 5 (Cage 5).

[0239] In some aspects, a chimeric polypeptide of the present disclosure consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 5 (Cage 5), wherein the chimeric polypeptide is capable of preferentially binding to the key polypeptide consisting of SEQ ID NO: 23 (Key 5), and upon binding to the key polypeptide, is capable of being degraded by a ubiquitin dependent pathway. In certain aspects, chimeric polypeptide consists or consists essentially of the amino acid sequence set forth in SEQ ID NO: 5 (Cage 5).

[0240] In some aspects, a chimeric polypeptide of the present disclosure comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 6 (Cage 6), wherein the chimeric polypeptide is capable of preferentially binding to the key polypeptide consisting of SEQ ID NO: 24 (Key 6), and upon binding to the key polypeptide, is capable of being degraded by a ubiquitin dependent pathway. In certain aspects, chimeric polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 6 (Cage 6).

[0241] In some aspects, a chimeric polypeptide of the present disclosure consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 6 (Cage 6), wherein the chimeric polypeptide is capable of preferentially binding to the key polypeptide consisting of SEQ ID NO: 24 (Key 6), and upon binding to the key polypeptide, is capable of being degraded by a ubiquitin dependent pathway. In certain aspects, chimeric polypeptide consists or consists essentially of the amino acid sequence set forth in SEQ ID NO: 6 (Cage 6).

[0242] In some aspects, a chimeric polypeptide of the present disclosure comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 7 (Cage 7), wherein the chimeric polypeptide is capable of preferentially binding to the key polypeptide consisting of SEQ ID NO: 25 (Key 7), and upon binding to the key polypeptide, is capable of being degraded by a ubiquitin dependent pathway. In certain aspects, chimeric polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 7 (Cage 7).

[0243] In some aspects, a chimeric polypeptide of the present disclosure consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 7 (Cage 7), wherein the chimeric polypeptide is capable of preferentially binding to the key polypeptide consisting of SEQ ID NO: 25 (Key 7), and upon binding to the key polypeptide, is capable of being degraded by a ubiquitin dependent pathway. In certain aspects, chimeric polypeptide consists or consists essentially of the amino acid sequence set forth in SEQ ID NO: 7 (Cage 7).

[0244] In some aspects, a chimeric polypeptide of the present disclosure comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 8 (Cage 8), wherein the chimeric polypeptide is capable of preferentially binding to the key polypeptide consisting of SEQ ID NO: 26 (Key 8), and upon binding to the key polypeptide, is capable of being degraded by a ubiquitin dependent pathway. In certain aspects, chimeric polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 8 (Cage 8).

[0245] In some aspects, a chimeric polypeptide of the present disclosure consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 8 (Cage 8), wherein the chimeric polypeptide is capable of preferentially binding to the key polypeptide consisting of SEQ ID NO: 26 (Key 8), and upon binding to the key polypeptide, is capable of being degraded by a ubiquitin dependent pathway. In certain aspects, chimeric polypeptide consists or consists essentially of the amino acid sequence set forth in SEQ ID NO: 8 (Cage 8).

[0246] In some aspects, a chimeric polypeptide of the present disclosure comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 9 (Cage 9), wherein the chimeric polypeptide is capable of preferentially binding to the key polypeptide consisting of SEQ ID NO: 27 (Key 9), and upon binding to the key polypeptide, is capable of being degraded by a ubiquitin dependent pathway. In certain aspects, chimeric polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 9 (Cage 9).

[0247] In some aspects, a chimeric polypeptide of the present disclosure consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 9 (Cage 9), wherein the chimeric polypeptide is capable of preferentially binding to the key polypeptide consisting of SEQ ID NO: 27 (Key 9), and upon binding to the key polypeptide, is capable of being degraded by a ubiquitin dependent pathway. In certain aspects, chimeric polypeptide consists or consists essentially of the amino acid sequence set forth in SEQ ID NO: 9 (Cage 9).

[0248] In some aspects, a chimeric polypeptide of the present disclosure comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 10 (Cage 10), wherein the chimeric polypeptide is capable of preferentially binding to the key polypeptide consisting of SEQ ID NO: 28 (Key 10), and upon binding to the key polypeptide, is capable of being degraded by a ubiquitin dependent pathway. In certain aspects, chimeric polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 10 (Cage 10).

[0249] In some aspects, a chimeric polypeptide of the present disclosure consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 10 (Cage 10), wherein the chimeric polypeptide is capable of preferentially binding to the key polypeptide consisting of SEQ ID NO: 28 (Key 10), and upon binding to the key polypeptide, is capable of being degraded by a ubiquitin dependent pathway. In certain aspects, chimeric polypeptide consists or consists essentially of the amino acid sequence set forth in SEQ ID NO: 10 (Cage 10).

[0250] In some aspects, a chimeric polypeptide of the present disclosure comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 11 (Cage 11), wherein the chimeric polypeptide is capable of preferentially binding to the key polypeptide consisting of SEQ ID NO: 29 (Key 11), and upon binding to the key polypeptide, is capable of being degraded by a ubiquitin dependent pathway. In certain aspects, chimeric polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 11 (Cage 11).

[0251] In some aspects, a chimeric polypeptide of the present disclosure consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 11 (Cage 11), wherein the chimeric polypeptide is capable of preferentially binding to the key polypeptide consisting of SEQ ID NO: 29 (Key 11), and upon binding to the key polypeptide, is capable of being degraded by a ubiquitin dependent pathway. In certain aspects, chimeric polypeptide consists or consists essentially of the amino acid sequence set forth in SEQ ID NO: 11 (Cage 11).

[0252] In some aspects, a chimeric polypeptide of the present disclosure comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 12 (Cage 12), wherein the chimeric polypeptide is capable of preferentially binding to the key polypeptide consisting of SEQ ID NO: 30 (Key 12), and upon binding to the key polypeptide, is capable of being degraded by a ubiquitin dependent pathway. In certain aspects, chimeric polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 12 (Cage 12).

[0253] In some aspects, a chimeric polypeptide of the present disclosure consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 12 (Cage 12), wherein the chimeric polypeptide is capable of preferentially binding to the key polypeptide consisting of SEQ ID NO: 30 (Key 12), and upon binding to the key polypeptide, is capable of being degraded by a ubiquitin dependent pathway. In certain aspects, chimeric polypeptide consists or consists essentially of the amino acid sequence set forth in SEQ ID NO: 12 (Cage 12).

[0254] In some aspects, a chimeric polypeptide of the present disclosure comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 13 (Cage 13), wherein the chimeric polypeptide is capable of preferentially binding to the key polypeptide consisting of SEQ ID NO: 31 (Key

13), and upon binding to the key polypeptide, is capable of being degraded by a ubiquitin dependent pathway. In certain aspects, chimeric polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 13 (Cage 13).

[0255] In some aspects, a chimeric polypeptide of the present disclosure consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 13 (Cage 13), wherein the chimeric polypeptide is capable of preferentially binding to the key polypeptide consisting of SEQ ID NO: 31 (Key 13), and upon binding to the key polypeptide, is capable of being degraded by a ubiquitin dependent pathway. In certain aspects, chimeric polypeptide consists or consists essentially of the amino acid sequence set forth in SEQ ID NO: 13 (Cage 13).

[0256] In some aspects, a chimeric polypeptide of the present disclosure comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 14 (Cage 14), wherein the chimeric polypeptide is capable of preferentially binding to the key polypeptide consisting of SEQ ID NO: 31 (Key

14), and upon binding to the key polypeptide, is capable of being degraded by a ubiquitin dependent pathway. In certain aspects, chimeric polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 14 (Cage 14). [0257] In some aspects, a chimeric polypeptide of the present disclosure consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 14 (Cage 14), wherein the chimeric polypeptide is capable of preferentially binding to the key polypeptide consisting of SEQ ID NO: 31 (Key 14), and upon binding to the key polypeptide, is capable of being degraded by a ubiquitin dependent pathway. In certain aspects, chimeric polypeptide consists or consists essentially of the amino acid sequence set forth in SEQ ID NO: 14 (Cage 14).

[0258] In some aspects, a chimeric polypeptide of the present disclosure comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 15 (Cage 15), wherein the chimeric polypeptide is capable of preferentially binding to the key polypeptide consisting of SEQ ID NO: 32 (Key 15), and upon binding to the key polypeptide, is capable of being degraded by a ubiquitin dependent pathway. In certain aspects, chimeric polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 15 (Cage 15).

[0259] In some aspects, a chimeric polypeptide of the present disclosure consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 15 (Cage 15), wherein the chimeric polypeptide is capable of preferentially binding to the key polypeptide consisting of SEQ ID NO: 32 (Key 15), and upon binding to the key polypeptide, is capable of being degraded by a ubiquitin dependent pathway. In certain aspects, chimeric polypeptide consists or consists essentially of the amino acid sequence set forth in SEQ ID NO: 15 (Cage 15).

[0260] In some aspects, a chimeric polypeptide of the present disclosure comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 16 (Cage 16), wherein the chimeric polypeptide is capable of preferentially binding to the key polypeptide consisting of SEQ ID NO: 33 (Key 16), and upon binding to the key polypeptide, is capable of being degraded by a ubiquitin dependent pathway. In certain aspects, chimeric polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 16 (Cage 16).

[0261] In some aspects, a chimeric polypeptide of the present disclosure consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 16 (Cage 16), wherein the chimeric polypeptide is capable of preferentially binding to the key polypeptide consisting of SEQ ID NO: 33 (Key 16), and upon binding to the key polypeptide, is capable of being degraded by a ubiquitin dependent pathway. In certain aspects, chimeric polypeptide consists or consists essentially of the amino acid sequence set forth in SEQ ID NO: 16 (Cage 16).

[0262] In some aspects, a chimeric polypeptide of the present disclosure comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 17 (Cage 17), wherein the chimeric polypeptide is capable of preferentially binding to the key polypeptide consisting of SEQ ID NO: 34 (Key 17), and upon binding to the key polypeptide, is capable of being degraded by a ubiquitin dependent pathway. In certain aspects, chimeric polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 17 (Cage 17).

[0263] In some aspects, a chimeric polypeptide of the present disclosure consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 17 (Cage 17), wherein the chimeric polypeptide is capable of preferentially binding to the key polypeptide consisting of SEQ ID NO: 34 (Key 17), and upon binding to the key polypeptide, is capable of being degraded by a ubiquitin dependent pathway. In certain aspects, chimeric polypeptide consists or consists essentially of the amino acid sequence set forth in SEQ ID NO: 17 (Cage 17).

[0264] In some aspects, a chimeric polypeptide of the present disclosure comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 18 (Cage 18), wherein the chimeric polypeptide is capable of preferentially binding to the key polypeptide consisting of SEQ ID NO: 35 (Key 18), and upon binding to the key polypeptide, is capable of being degraded by a ubiquitin dependent pathway. In certain aspects, chimeric polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 18 (Cage 18).

[0265] In some aspects, a chimeric polypeptide of the present disclosure consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 18 (Cage 18), wherein the chimeric polypeptide is capable of preferentially binding to the key polypeptide consisting of SEQ ID NO: 35 (Key 18), and upon binding to the key polypeptide, is capable of being degraded by a ubiquitin dependent pathway. In certain aspects, chimeric polypeptide consists or consists essentially of the amino acid sequence set forth in SEQ ID NO: 18 (Cage 18).

[0266] In some aspects, a chimeric polypeptide of the present disclosure comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in helix 1, helix 2, and/or helix 3 of SEQ ID NO: 13 (Cage 13) (z.e., SEQ ID NOs: 40, 41, and 115, respectively), wherein the chimeric polypeptide is capable of preferentially binding to the key polypeptide consisting of SEQ ID NO: 31 (Key 13), and upon binding to the key polypeptide, is capable of being degraded by a ubiquitin dependent pathway. In certain aspects, chimeric polypeptide comprises the amino acid sequence set forth in helix 1, helix 2, and/or helix 3 of SEQ ID NO: 13 (Cage 13) (i.e., SEQ ID NOs: 40, 41, and 115, respectively).

[0267] In some aspects, a chimeric polypeptide of the present disclosure consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in helix 1, helix 2, and/or helix 3 of SEQ ID NO: 13 (Cage 13) (i.e., SEQ ID NOs: 40, 41, and 115, respectively), wherein the chimeric polypeptide is capable of preferentially binding to the key polypeptide consisting of SEQ ID NO: 31 (Key 13), and upon binding to the key polypeptide, is capable of being degraded by a ubiquitin dependent pathway. In certain aspects, chimeric polypeptide comprises the amino acid sequence set forth in helix 1, helix 2, and/or helix 3 of SEQ ID NO: 13 (Cage 13) (i.e., SEQ ID NOs: 40, 41, and 115, respectively).

[0268] In some aspects, a chimeric polypeptide of the present disclosure comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in helix 1, helix 2, and/or helix 3 of SEQ ID NO: 14 (Cage 14) (i.e., SEQ ID NOs: 40, 41, and 116, respectively), wherein the chimeric polypeptide is capable of preferentially binding to the key polypeptide consisting of SEQ ID NO: 31 (Key 14), and upon binding to the key polypeptide, is capable of being degraded by a ubiquitin dependent pathway. In certain aspects, chimeric polypeptide comprises the amino acid sequence set forth in helix 1, helix 2, and/or helix 3 of SEQ ID NO: 14 (Cage 14) (i.e., SEQ ID NOs: 40, 41, and 116, respectively).

[0269] In some aspects, a chimeric polypeptide of the present disclosure consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in helix 1, helix 2, and/or helix 3 of SEQ ID NO: 14 (Cage 14) (i.e., SEQ ID NOs: 40, 41, and 116, respectively), wherein the chimeric polypeptide is capable of preferentially binding to the key polypeptide consisting of SEQ ID NO: 31 (Key 14), and upon binding to the key polypeptide, is capable of being degraded by a ubiquitin dependent pathway. In certain aspects, chimeric polypeptide comprises the amino acid sequence set forth in helix 1, helix 2, and/or helix 3 of SEQ ID NO: 14 (Cage 14) (i.e., SEQ ID NOs: 40, 41, and 116, respectively).

[0270] In some aspects, a chimeric polypeptide of the present disclosure comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in helix 1, helix 2, and/or helix 3 of SEQ ID NO: 15 (Cage 15) (i.e., SEQ ID NOs: 43, 44, and 117, respectively), wherein the chimeric polypeptide is capable of preferentially binding to the key polypeptide consisting of SEQ ID NO: 32 (key 15), and upon binding to the key polypeptide, is capable of being degraded by a ubiquitin dependent pathway. In certain aspects, chimeric polypeptide comprises the amino acid sequence set forth in helix 1, helix 2, and/or helix 3 of SEQ ID NO: 15 (Cage 15) (i.e., SEQ ID NOs: 43, 44, and

117, respectively).

[0271] In some aspects, a chimeric polypeptide of the present disclosure consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in helix 1, helix 2, and/or helix 3 of SEQ ID NO: 15 (Cage 15) (i.e., SEQ ID NOs: 43, 44, and 117, respectively), wherein the chimeric polypeptide is capable of preferentially binding to the key polypeptide consisting of SEQ ID NO: 32 (Key 15), and upon binding to the key polypeptide, is capable of being degraded by a ubiquitin dependent pathway. In certain aspects, chimeric polypeptide comprises the amino acid sequence set forth in helix 1, helix 2, and/or helix 3 of SEQ ID NO: 15 (Cage 15) (i.e., SEQ ID NOs: 43, 44, and 117, respectively).

[0272] In some aspects, a chimeric polypeptide of the present disclosure comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in helix 1, helix 2, and/or helix 3 of SEQ ID NO: 16 (Cage 16) (i.e., SEQ ID NOs: 46, 47, and 118, respectively), wherein the chimeric polypeptide is capable of preferentially binding to the key polypeptide consisting of SEQ ID NO: 33 (Key 16), and upon binding to the key polypeptide, is capable of being degraded by a ubiquitin dependent pathway. In certain aspects, chimeric polypeptide comprises the amino acid sequence set forth in helix 1, helix 2, and/or helix 3 of SEQ ID NO: 16 (Cage 16) (i.e., SEQ ID NOs: 46, 47, and

118, respectively). [0273] In some aspects, a chimeric polypeptide of the present disclosure consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in helix 1, helix 2, and/or helix 3 of SEQ ID NO: 16 (Cage 16) (z.e., SEQ ID NOs: 46, 47, and 118, respectively), wherein the chimeric polypeptide is capable of preferentially binding to the key polypeptide consisting of SEQ ID NO: 33 (Key 16), and upon binding to the key polypeptide, is capable of being degraded by a ubiquitin dependent pathway. In certain aspects, chimeric polypeptide comprises the amino acid sequence set forth in helix 1, helix 2, and/or helix 3 of SEQ ID NO: 16 (Cage 16) (z.e., SEQ ID NOs: 46, 47, and 118, respectively).

[0274] In some aspects, a chimeric polypeptide of the present disclosure comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in helix 1, helix 2, and/or helix 3 of SEQ ID NO: 17 (Cage 17) (i.e., SEQ ID NOs: 49, 50, and 119, respectively), wherein the chimeric polypeptide is capable of preferentially binding to the key polypeptide consisting of SEQ ID NO: 34 (Key 17), and upon binding to the key polypeptide, is capable of being degraded by a ubiquitin dependent pathway. In certain aspects, chimeric polypeptide comprises the amino acid sequence set forth in helix 1, helix 2, and/or helix 3 of SEQ ID NO: 17 (Cage 17) (i.e., SEQ ID NOs: 49, 50, and 119, respectively).

[0275] In some aspects, a chimeric polypeptide of the present disclosure consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in helix 1, helix 2, and/or helix 3 of SEQ ID NO: 17 (Cage 17) ( i.e ., SEQ ID NOs: 49, 50, and 119, respectively), wherein the chimeric polypeptide is capable of preferentially binding to the key polypeptide consisting of SEQ ID NO: 34 (Key 17), and upon binding to the key polypeptide, is capable of being degraded by a ubiquitin dependent pathway. In certain aspects, chimeric polypeptide comprises the amino acid sequence set forth in helix 1, helix 2, and/or helix 3 of SEQ ID NO: 17 (Cage 17) {i.e., SEQ ID NOs: 49, 50, and 119, respectively).

[0276] In some aspects, a chimeric polypeptide of the present disclosure comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in helix 1, helix 2, and/or helix 3 of SEQ ID NO: 18 (Cage 18) {i.e., SEQ ID NOs: 52, 53, and 120, respectively), wherein the chimeric polypeptide is capable of preferentially binding to the key polypeptide consisting of SEQ ID NO: 35 (Key 18), and upon binding to the key polypeptide, is capable of being degraded by a ubiquitin dependent pathway. In certain aspects, chimeric polypeptide comprises the amino acid sequence set forth in helix 1, helix 2, and/or helix 3 of SEQ ID NO: 18 (Cage 18) {i.e., SEQ ID NOs: 52, 53, and 120, respectively).

[0277] In some aspects, a chimeric polypeptide of the present disclosure consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in helix 1, helix 2, and/or helix 3 of SEQ ID NO: 18 (Cage 18) ( i.e ., SEQ ID NOs: 52, 53, and 120, respectively), wherein the chimeric polypeptide is capable of preferentially binding to the key polypeptide consisting of SEQ ID NO: 35 (Key 18), and upon binding to the key polypeptide, is capable of being degraded by a ubiquitin dependent pathway. In certain aspects, chimeric polypeptide comprises the amino acid sequence set forth in helix 1, helix 2, and/or helix 3 of SEQ ID NO: 18 (Cage 18) {i.e., SEQ ID NOs: 52, 53, and 120, respectively).

[0278] In some aspects, a chimeric polypeptide of the present disclosure comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in helix 1, helix 2, helix 3, and/or helix 4 of SEQ ID NO: 1 (Cage 1) {i.e., SEQ ID NOs: 55, 56, 57, and 121, respectively), wherein the chimeric polypeptide is capable of preferentially binding to the key polypeptide consisting of SEQ ID NO: 19 (Key 1), and upon binding to the key polypeptide, is capable of being degraded by a ubiquitin dependent pathway. In certain aspects, chimeric polypeptide comprises the amino acid sequence set forth in helix 1, helix 2, helix 3, and/or helix 4 of SEQ ID NO: 1 (Cage 1) {i.e., SEQ ID NOs: 55, 56, 57, and 121, respectively).

[0279] In some aspects, a chimeric polypeptide of the present disclosure consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in helix 1, helix 2, helix 3, and/or helix 4 of SEQ ID NO: 1 (Cage 1) (z.e., SEQ ID NOs: 55, 56, 57, and 121, respectively), wherein the chimeric polypeptide is capable of preferentially binding to the key polypeptide consisting of SEQ ID NO: 19 (Key 1), and upon binding to the key polypeptide, is capable of being degraded by a ubiquitin dependent pathway. In certain aspects, chimeric polypeptide comprises the amino acid sequence set forth in helix 1, helix 2, helix 3, and/or helix 4 of SEQ ID NO: 1 (Cage 1) (z.e., SEQ ID NOs: 55, 56, 57, and 121, respectively).

[0280] In some aspects, a chimeric polypeptide of the present disclosure comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in helix 1, helix 2, helix 3, and/or helix 4 of SEQ ID NO: 2 (Cage 2) (z.e., SEQ ID NOs: 59, 60, 61, and 122, respectively), wherein the chimeric polypeptide is capable of preferentially binding to the key polypeptide consisting of SEQ ID NO: 20 (Key 2), and upon binding to the key polypeptide, is capable of being degraded by a ubiquitin dependent pathway. In certain aspects, chimeric polypeptide comprises the amino acid sequence set forth in helix 1, helix 2, helix 3, and/or helix 4 of SEQ ID NO: 2 (Cage 2) (i.e., SEQ ID NOs: 59, 60, 61, and 122, respectively).

[0281] In some aspects, a chimeric polypeptide of the present disclosure consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in helix 1, helix 2, helix 3, and/or helix 4 of SEQ ID NO: 2 (Cage 2) ( i.e ., SEQ ID NOs: 59, 60, 61, and 122, respectively), wherein the chimeric polypeptide is capable of preferentially binding to the key polypeptide consisting of SEQ ID NO: 20 (Key 2), and upon binding to the key polypeptide, is capable of being degraded by a ubiquitin dependent pathway. In certain aspects, chimeric polypeptide comprises the amino acid sequence set forth in helix 1, helix 2, helix 3, and/or helix 4 of SEQ ID NO: 2 (Cage 2) ( i.e ., SEQ ID NOs: 59, 60, 61, and 122, respectively).

[0282] In some aspects, a chimeric polypeptide of the present disclosure comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in helix 1, helix 2, helix 3, and/or helix 4 of SEQ ID NO: 3 (Cage 3) {i.e., SEQ ID NOs: 67, 68, 69, and 124, respectively), wherein the chimeric polypeptide is capable of preferentially binding to the key polypeptide consisting of SEQ ID NO: 21 (Key 3), and upon binding to the key polypeptide, is capable of being degraded by a ubiquitin dependent pathway. In certain aspects, chimeric polypeptide comprises the amino acid sequence set forth in helix 1, helix 2, helix 3, and/or helix 4 of SEQ ID NO: 3 (Cage 3) {i.e., SEQ ID NOs: 67, 68, 69, and 124, respectively).

[0283] In some aspects, a chimeric polypeptide of the present disclosure consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in helix 1, helix 2, helix 3, and/or helix 4 of SEQ ID NO: 3 (Cage 3) {i.e., SEQ ID NOs: 67, 68, 69, and 124, respectively), wherein the chimeric polypeptide is capable of preferentially binding to the key polypeptide consisting of SEQ ID NO: 21 (Key 3), and upon binding to the key polypeptide, is capable of being degraded by a ubiquitin dependent pathway. In certain aspects, chimeric polypeptide comprises the amino acid sequence set forth in helix 1, helix 2, helix 3, and/or helix 4 of SEQ ID NO: 3 (Cage 3) ( i.e ., SEQ ID NOs: 67, 68, 69, and 124, respectively).

[0284] In some aspects, a chimeric polypeptide of the present disclosure comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in helix 1, helix 2, helix 3, and/or helix 4 of SEQ ID NO: 4 (Cage 4) {i.e., SEQ ID NOs: 71, 72, 73, and 125, respectively), wherein the chimeric polypeptide is capable of preferentially binding to the key polypeptide consisting of SEQ ID NO: 22 (Key 4), and upon binding to the key polypeptide, is capable of being degraded by a ubiquitin dependent pathway. In certain aspects, chimeric polypeptide comprises the amino acid sequence set forth in helix 1, helix 2, helix 3, and/or helix 4 of SEQ ID NO: 4 (Cage 4) {i.e., SEQ ID NOs: 71, 72, 73, and 125, respectively).

[0285] In some aspects, a chimeric polypeptide of the present disclosure consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in helix 1, helix 2, helix 3, and/or helix 4 of SEQ ID NO: 4 (Cage 4) {i.e., SEQ ID NOs: 71, 72, 73, and 125, respectively), wherein the chimeric polypeptide is capable of preferentially binding to the key polypeptide consisting of SEQ ID NO: 22 (Key 4), and upon binding to the key polypeptide, is capable of being degraded by a ubiquitin dependent pathway. In certain aspects, chimeric polypeptide comprises the amino acid sequence set forth in helix 1, helix 2, helix 3, and/or helix 4 of SEQ ID NO: 4 (Cage 4) ( i.e ., SEQ ID NOs: 71, 72, 73, and 125, respectively).

[0286] In some aspects, a chimeric polypeptide of the present disclosure comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in helix 1, helix 2, helix 3, and/or helix 4 of SEQ ID NO: 5 (Cage 5) {i.e., SEQ ID NOs: 79, 80, 81, and 127, respectively), wherein the chimeric polypeptide is capable of preferentially binding to the key polypeptide consisting of SEQ ID NO: 23 (Key 5), and upon binding to the key polypeptide, is capable of being degraded by a ubiquitin dependent pathway. In certain aspects, chimeric polypeptide comprises the amino acid sequence set forth in helix 1, helix 2, helix 3, and/or helix 4 of SEQ ID NO: 5 (Cage 5) {i.e., SEQ ID NOs: 79, 80, 81, and 127, respectively).

[0287] In some aspects, a chimeric polypeptide of the present disclosure consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in helix 1, helix 2, helix 3, and/or helix 4 of SEQ ID NO: 5 (Cage 5) {i.e., SEQ ID NOs: 79, 80, 81, and 127, respectively), wherein the chimeric polypeptide is capable of preferentially binding to the key polypeptide consisting of SEQ ID NO: 23 (Key 5), and upon binding to the key polypeptide, is capable of being degraded by a ubiquitin dependent pathway. In certain aspects, chimeric polypeptide comprises the amino acid sequence set forth in helix 1, helix 2, helix 3, and/or helix 4 of SEQ ID NO: 5 (Cage 5) ( i.e ., SEQ ID NOs: 79, 80, 81, and 127, respectively).

[0288] In some aspects, a chimeric polypeptide of the present disclosure comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in helix 1, helix 2, helix 3, and/or helix 4 of SEQ ID NO: 6 (Cage 6) (; i.e ., SEQ ID NOs: 83, 84, 85, and 128, respectively), wherein the chimeric polypeptide is capable of preferentially binding to the key polypeptide consisting of SEQ ID NO: 24 (Key 6), and upon binding to the key polypeptide, is capable of being degraded by a ubiquitin dependent pathway. In certain aspects, chimeric polypeptide comprises the amino acid sequence set forth in helix 1, helix 2, helix 3, and/or helix 4 of SEQ ID NO: 6 (Cage 6) (i.e., SEQ ID NOs: 83, 84, 85, and 128, respectively).

[0289] In some aspects, a chimeric polypeptide of the present disclosure consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in helix 1, helix 2, helix 3, and/or helix 4 of SEQ ID NO: 6 (Cage 6) (i.e., SEQ ID NOs: 83, 84, 85, and 128, respectively), wherein the chimeric polypeptide is capable of preferentially binding to the key polypeptide consisting of SEQ ID NO: 24 (Key 6), and upon binding to the key polypeptide, is capable of being degraded by a ubiquitin dependent pathway. In certain aspects, chimeric polypeptide comprises the amino acid sequence set forth in helix 1, helix 2, helix 3, and/or helix 4 of SEQ ID NO: 6 (Cage 6) (i.e., SEQ ID NOs: 83, 84, 85, and 128, respectively). [0290] In some aspects, a chimeric polypeptide of the present disclosure comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in helix 1, helix 2, helix 3, and/or helix 4 of SEQ ID NO: 7 (Cage 7) (i.e., SEQ ID NOs: 87, 88, 89, and 129, respectively), wherein the chimeric polypeptide is capable of preferentially binding to the key polypeptide consisting of SEQ ID NO: 25 (Key 7), and upon binding to the key polypeptide, is capable of being degraded by a ubiquitin dependent pathway. In certain aspects, chimeric polypeptide comprises the amino acid sequence set forth in helix 1, helix 2, helix 3, and/or helix 4 of SEQ ID NO: 7 (Cage 7) (i.e., SEQ ID NOs: 87, 88, 89, and 129, respectively).

[0291] In some aspects, a chimeric polypeptide of the present disclosure consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in helix 1, helix 2, helix 3, and/or helix 4 of SEQ ID NO: 7 (Cage 7) (i.e., SEQ ID NOs: 87, 88, 89, and 129, respectively), wherein the chimeric polypeptide is capable of preferentially binding to the key polypeptide consisting of SEQ ID NO: 25 (Key 7), and upon binding to the key polypeptide, is capable of being degraded by a ubiquitin dependent pathway. In certain aspects, chimeric polypeptide comprises the amino acid sequence set forth in helix 1, helix 2, helix 3, and/or helix 4 of SEQ ID NO: 7 (Cage 7) (i.e., SEQ ID NOs: 87, 88, 89, and 129, respectively).

[0292] In some aspects, a chimeric polypeptide of the present disclosure comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in helix 1, helix 2, helix 3, and/or helix 4 of SEQ ID NO: 8 (Cage 8) (i.e., SEQ ID NOs: 91, 92, 93, and 130, respectively), wherein the chimeric polypeptide is capable of preferentially binding to the key polypeptide consisting of SEQ ID NO: 26 (Key 8), and upon binding to the key polypeptide, is capable of being degraded by a ubiquitin dependent pathway. In certain aspects, chimeric polypeptide comprises the amino acid sequence set forth in helix 1, helix 2, helix 3, and/or helix 4 of SEQ ID NO: 8 (Cage 8) (i.e., SEQ ID NOs: 91, 92, 93, and 130, respectively).

[0293] In some aspects, a chimeric polypeptide of the present disclosure consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in helix 1, helix 2, helix 3, and/or helix 4 of SEQ ID NO: 8 (Cage 8) (i.e., SEQ ID NOs: 91, 92, 93, and 130, respectively), wherein the chimeric polypeptide is capable of preferentially binding to the key polypeptide consisting of SEQ ID NO: 26 (Key 8), and upon binding to the key polypeptide, is capable of being degraded by a ubiquitin dependent pathway. In certain aspects, chimeric polypeptide comprises the amino acid sequence set forth in helix 1, helix 2, helix 3, and/or helix 4 of SEQ ID NO: 8 (Cage 8) (i.e., SEQ ID NOs: 91, 92, 93, and 130, respectively).

[0294] In some aspects, a chimeric polypeptide of the present disclosure comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in helix 1, helix 2, helix 3, and/or helix 4 of SEQ ID NO: 9 (Cage 9) (i.e., SEQ ID NOs: 95, 96, 97, and 131, respectively), wherein the chimeric polypeptide is capable of preferentially binding to the key polypeptide consisting of SEQ ID NO: 27 (Key 9), and upon binding to the key polypeptide, is capable of being degraded by a ubiquitin dependent pathway. In certain aspects, chimeric polypeptide comprises the amino acid sequence set forth in helix 1, helix 2, helix 3, and/or helix 4 of SEQ ID NO: 9 (Cage 9) (i.e., SEQ ID NOs: 95, 96, 97, and 131, respectively).

[0295] In some aspects, a chimeric polypeptide of the present disclosure consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in helix 1, helix 2, helix 3, and/or helix 4 of SEQ ID NO: 9 (Cage 9) (i.e., SEQ ID NOs: 95, 96, 97, and 131, respectively), wherein the chimeric polypeptide is capable of preferentially binding to the key polypeptide consisting of SEQ ID NO: 27 (Key 9), and upon binding to the key polypeptide, is capable of being degraded by a ubiquitin dependent pathway. In certain aspects, chimeric polypeptide comprises the amino acid sequence set forth in helix 1, helix 2, helix 3, and/or helix 4 of SEQ ID NO: 9 (Cage 9) (i.e., SEQ ID NOs: 95, 96, 97, and 131, respectively).

[0296] In some aspects, a chimeric polypeptide of the present disclosure comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in helix 1, helix 2, helix 3, and/or helix 4 of SEQ ID NO: 10 (Cage 10) ( i.e ., SEQ ID NOs: 99, 100, 101, and 132, respectively), wherein the chimeric polypeptide is capable of preferentially binding to the key polypeptide consisting of SEQ ID NO: 28 (Key 10), and upon binding to the key polypeptide, is capable of being degraded by a ubiquitin dependent pathway. In certain aspects, chimeric polypeptide comprises the amino acid sequence set forth in helix 1, helix 2, helix 3, and/or helix 4 of SEQ ID NO: 10 (Cage 10) ( i.e ., SEQ ID NOs: 99, 100, 101, and 132, respectively).

[0297] In some aspects, a chimeric polypeptide of the present disclosure consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in helix 1, helix 2, helix 3, and/or helix 4 of SEQ ID NO: 10 (Cage 10) {i.e., SEQ ID NOs: 99, 100, 101, and 132, respectively), wherein the chimeric polypeptide is capable of preferentially binding to the key polypeptide consisting of SEQ ID NO: 28 (Key 10), and upon binding to the key polypeptide, is capable of being degraded by a ubiquitin dependent pathway. In certain aspects, chimeric polypeptide comprises the amino acid sequence set forth in helix 1, helix 2, helix 3, and/or helix 4 of SEQ ID NO: 10 (Cage 10) {i.e., SEQ ID NOs: 99, 100, 101, and 132, respectively).

[0298] In some aspects, a chimeric polypeptide of the present disclosure comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in helix 1, helix 2, helix 3, and/or helix 4 of SEQ ID NO: 11 (Cage 11) (i.e., SEQ ID NOs: 103, 104, 105, and 128, respectively), wherein the chimeric polypeptide is capable of preferentially binding to the key polypeptide consisting of SEQ ID NO: 29 (Key 11), and upon binding to the key polypeptide, is capable of being degraded by a ubiquitin dependent pathway. In certain aspects, chimeric polypeptide comprises the amino acid sequence set forth in helix 1, helix 2, helix 3, and/or helix 4 of SEQ ID NO: 11 (Cage 11) (i.e., SEQ ID NOs: 103, 104, 105, and 128, respectively).

[0299] In some aspects, a chimeric polypeptide of the present disclosure consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in helix 1, helix 2, helix 3, and/or helix 4 of SEQ ID NO: 11 (Cage 11) (i.e., SEQ ID NOs: 103, 104, 105, and 128, respectively), wherein the chimeric polypeptide is capable of preferentially binding to the key polypeptide consisting of SEQ ID NO: 29 (Key 11), and upon binding to the key polypeptide, is capable of being degraded by a ubiquitin dependent pathway. In certain aspects, chimeric polypeptide comprises the amino acid sequence set forth in helix 1, helix 2, helix 3, and/or helix 4 of SEQ ID NO: 11 (Cage 11) (i.e., SEQ ID NOs: 103, 104, 105, and 128, respectively).

[0300] In some aspects, a chimeric polypeptide of the present disclosure comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in helix 1, helix 2, helix 3, and/or helix 4 of SEQ ID NO: 12 (Cage 12) (i.e., SEQ ID NOs: 111, 112, 112, and 135, respectively), wherein the chimeric polypeptide is capable of preferentially binding to the key polypeptide consisting of SEQ ID NO: 30 (Key 12), and upon binding to the key polypeptide, is capable of being degraded by a ubiquitin dependent pathway. In certain aspects, chimeric polypeptide comprises the amino acid sequence set forth in helix 1, helix 2, helix 3, and/or helix 4 of SEQ ID NO: 12 (Cage 12) (, i.e ., SEQ ID NOs: 111, 112, 112, and 135, respectively).

[0301] In some aspects, a chimeric polypeptide of the present disclosure consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in helix 1, helix 2, helix 3, and/or helix 4 of SEQ ID NO: 12 (Cage 12) {i.e., SEQ ID NOs: 111, 112, 112, and 135, respectively), wherein the chimeric polypeptide is capable of preferentially binding to the key polypeptide consisting of SEQ ID NO: 30 (Key 12), and upon binding to the key polypeptide, is capable of being degraded by a ubiquitin dependent pathway. In certain aspects, chimeric polypeptide comprises the amino acid sequence set forth in helix 1, helix 2, helix 3, and/or helix 4 of SEQ ID NO: 12 (Cage 12) {i.e., SEQ ID NOs: 111, 112, 112, and 135, respectively).

Table 3. Alpha Helices of 2plusl Design Chimeric Polypeptides

Table 4. Alpha Helices of 3plusl Design Chimeric Polypeptides

II. c. Key Polypeptide

[0302] As described herein, a key polypeptide plays an essential role in the activation of the caged degron in a chimeric polypeptide of the present disclosure. In some aspects, the dynamic range of activation by key polypeptides can be tuned by truncating the latch region length to be shorter than the alpha-helices in the structural region, simultaneously weakening the cage polypeptide-latch region interaction and opening an exposed region on the cage polypeptide that the key polypeptide can bind to. Therefore, in some aspects, a key polypeptide is longer ( e.g ., at least 2, 3, 4, 5, 6, 7, 8, 9, 10 amino acids) in length than the latch region of the cage polypeptide. Similarly, the dynamic range of activation by key polypeptides can also be tuned in a similar manner by designing mutations into the latch region that weaken the cage polypeptide-latch region interaction, and thereby, facilitating the displacement of the latch region by a key polypeptide and activation of the degron. Therefore, in some aspects, a key polypeptide and the latch region of the cage polypeptide are not identical. In some aspects, the key polypeptide and the latch region of the cage polypeptide are at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 75%, at least about 80%, at least about 86%, at least about 90%, or at least about 95% identical to each other. In some aspects, the key polypeptide and the latch region of the cage polypeptide are identical except 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12 amino acids. In some aspects, the key polypeptide and the latch region of the cage polypeptides comprise similar amino acid sequences, e.g ., at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 75% sequence identity, except that the latch region binds to the structural region of the cage polypeptide with a lower affinity, e.g. , less hydrophobic interaction, than the key polypeptide does. In other words, the key polypeptide can bind to the structural region with a higher affinity that the latch region does, e.g. , higher hydrophobic interaction.

[0303] In some aspects, a key polypeptide that can be used with a chimeric polypeptide of the present disclosure comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65% least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence as set forth in SEQ ID NO: 19 (Key 1), SEQ ID NO: 20 (Key 2), SEQ ID NO: 21 (Key 3), SEQ ID NO: 22 (Key 4), SEQ ID NO: 23 (Key 5), SEQ ID NO: 24 (Key 6), SEQ ID NO: 25 (Key 7), SEQ ID NO: 26 (Key 8), SEQ ID NO: 27 (Key 9), SEQ ID NO: 28 (Key 10), SEQ ID NO: 29 (Key 11), SEQ ID NO: 30 (Key 12), SEQ ID NO: 31 (Key 13), SEQ ID NO: 32 (Key 15), SEQ ID NO: 33 (Key 16), SEQ ID NO: 34 (Key 17), or SEQ ID NO: 35 (Key 18), wherein the key polypeptide is capable of binding to the structural region of the cage polypeptide of a chimeric polypeptide disclosed herein.

[0304] In some aspects, a key polypeptide that can be used with a chimeric polypeptide of the present disclosure consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65% least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence as set forth in SEQ ID NO: 19 (Key 1), SEQ ID NO: 20 (Key 2), SEQ ID NO: 21 (Key 3), SEQ ID NO: 22 (Key 4), SEQ ID NO: 23 (Key 5), SEQ ID NO: 24 (Key 6), SEQ ID NO: 25 (Key 7), SEQ ID NO: 26 (Key 8), SEQ ID NO: 27 (Key 9), SEQ ID NO: 28 (Key 10), SEQ ID NO: 29 (Key 11), SEQ ID NO: 30 (Key 12), SEQ ID NO: 31 (Key 13), SEQ ID NO: 32 (Key 15), SEQ ID NO: 33 (Key 16), SEQ ID NO: 34 (Key 17), or SEQ ID NO: 35 (Key 18), wherein the key polypeptide is capable of binding to the structural region of the cage polypeptide of a chimeric polypeptide disclosed herein.

[0305] In some aspects, (i) a key polypeptide comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 19 (Key 1), and (ii) the chimeric polypeptide to which the key polypeptide can bind comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 1 (Cage 1). In certain aspects, the key polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 19 (Key 1), and the chimeric polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 1 (Cage 1).

[0306] In some aspects, (i) a key polypeptide consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 19 (Key 1), and (ii) the chimeric polypeptide to which the key polypeptide can bind consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 1 (Cage 1). In certain aspects, the key polypeptide consists or consists essentially of the amino acid sequence set forth in SEQ ID NO: 19 (Key 1), and the chimeric polypeptide consists or consists essentially of the amino acid sequence set forth in SEQ ID NO: 1 (Cage 1).

[0307] In some aspects, (i) a key polypeptide comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 20 (Key 2), and (ii) the chimeric polypeptide to which the key polypeptide can bind comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 2 (Cage 2). In certain aspects, the key polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 20 (Key 2), and the chimeric polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 2 (Cage 2).

[0308] In some aspects, (i) a key polypeptide consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 20 (Key 2), and (ii) the chimeric polypeptide to which the key polypeptide can bind consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 2 (Cage 2). In certain aspects, the key polypeptide consists or consists essentially of the amino acid sequence set forth in SEQ ID NO: 20 (Key 2), and the chimeric polypeptide consists or consists essentially of the amino acid sequence set forth in SEQ ID NO: 2 (Cage 2).

[0309] In some aspects, (i) a key polypeptide comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 21 (Key 3), and (ii) the chimeric polypeptide to which the key polypeptide can bind comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 3 (Cage 3). In certain aspects, the key polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 21 (Key 3), and the chimeric polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 3 (Cage 3).

[0310] In some aspects, (i) a key polypeptide consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 21 (Key 3), and (ii) the chimeric polypeptide to which the key polypeptide can bind consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 3 (Cage 3). In certain aspects, the key polypeptide consists or consists essentially of the amino acid sequence set forth in SEQ ID NO: 21 (key 3), and the chimeric polypeptide consists or consists essentially of the amino acid sequence set forth in SEQ ID NO: 3 (Cage 3).

[0311] In some aspects, (i) a key polypeptide comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 22 (Key 4), and (ii) the chimeric polypeptide to which the key polypeptide can bind comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 4 (Cage 4). In certain aspects, the key polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 22 (Key 4), and the chimeric polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 4 (Cage 4).

[0312] In some aspects, (i) a key polypeptide consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 22 (Key 4), and (ii) the chimeric polypeptide to which the key polypeptide can bind consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 4 (Cage 4). In certain aspects, the key polypeptide consists or consists essentially of the amino acid sequence set forth in SEQ ID NO: 22 (key 4), and the chimeric polypeptide consists or consists essentially of the amino acid sequence set forth in SEQ ID NO: 4 (Cage 4).

[0313] In some aspects, (i) a key polypeptide comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 23 (Key 5), and (ii) the chimeric polypeptide to which the key polypeptide can bind comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 5 (Cage 5). In certain aspects, the key polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 23 (Key 5), and the chimeric polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 5 (Cage 5).

[0314] In some aspects, (i) a key polypeptide consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 23 (Key 5), and (ii) the chimeric polypeptide to which the key polypeptide can bind consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 5 (Cage 5). In certain aspects, the key polypeptide consists or consists essentially of the amino acid sequence set forth in SEQ ID NO: 23 (key 5), and the chimeric polypeptide consists or consists essentially of the amino acid sequence set forth in SEQ ID NO: 5 (Cage 5).

[0315] In some aspects, (i) a key polypeptide comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 24 (Key 6), and (ii) the chimeric polypeptide to which the key polypeptide can bind comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 6 (Cage 6). In certain aspects, the key polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 24 (Key 6), and the chimeric polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 6 (Cage 6).

[0316] In some aspects, (i) a key polypeptide consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 24 (Key 6), and (ii) the chimeric polypeptide to which the key polypeptide can bind consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 6 (Cage 6). In certain aspects, the key polypeptide consists or consists essentially of the amino acid sequence set forth in SEQ ID NO: 24 (Key 6), and the chimeric polypeptide consists or consists essentially of the amino acid sequence set forth in SEQ ID NO: 6 (Cage 6).

[0317] In some aspects, (i) a key polypeptide comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 25 (Key 7), and (ii) the chimeric polypeptide to which the key polypeptide can bind comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 7 (Cage 7). In certain aspects, the key polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 25 (key 7), and the chimeric polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 7 (Cage 7).

[0318] In some aspects, (i) a key polypeptide consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 25 (Key 7), and (ii) the chimeric polypeptide to which the key polypeptide can bind consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 7 (Cage 7). In certain aspects, the key polypeptide consists or consists essentially of the amino acid sequence set forth in SEQ ID NO: 25 (key 7), and the chimeric polypeptide consists or consists essentially of the amino acid sequence set forth in SEQ ID NO: 7 (Cage 7).

[0319] In some aspects, (i) a key polypeptide comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 26 (Key 8), and (ii) the chimeric polypeptide to which the key polypeptide can bind comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 8 (Cage 8). In certain aspects, the key polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 26 (Key 8), and the chimeric polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 8 (Cage 8).

[0320] In some aspects, (i) a key polypeptide consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 26 (Key 8), and (ii) the chimeric polypeptide to which the key polypeptide can bind consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 8 (Cage 8). In certain aspects, the key polypeptide consists or consists essentially of the amino acid sequence set forth in SEQ ID NO: 26 (Key 8), and the chimeric polypeptide consists or consists essentially of the amino acid sequence set forth in SEQ ID NO: 8 (Cage 8).

[0321] In some aspects, (i) a key polypeptide comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 27 (Key 9), and (ii) the chimeric polypeptide to which the key polypeptide can bind comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 9 (Cage 9). In certain aspects, the key polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 27 (Key 9), and the chimeric polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 9 (Cage 9).

[0322] In some aspects, (i) a key polypeptide consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 27 (Key 9), and (ii) the chimeric polypeptide to which the key polypeptide can bind consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 9 (Cage 9). In certain aspects, the key polypeptide consists or consists essentially of the amino acid sequence set forth in SEQ ID NO: 27 (Key 9), and the chimeric polypeptide consists or consists essentially of the amino acid sequence set forth in SEQ ID NO: 9 (Cage 9).

[0323] In some aspects, (i) a key polypeptide comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 28 (Key 10), and (ii) the chimeric polypeptide to which the key polypeptide can bind comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 10 (Cage 10). In certain aspects, the key polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 28 (Key 10), and the chimeric polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 10 (Cage 10).

[0324] In some aspects, (i) a key polypeptide consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 28 (Key 10), and (ii) the chimeric polypeptide to which the key polypeptide can bind consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 10 (Cage 10). In certain aspects, the key polypeptide consists or consists essentially of the amino acid sequence set forth in SEQ ID NO: 28 (Key 10), and the chimeric polypeptide consists or consists essentially of the amino acid sequence set forth in SEQ ID NO: 10 (Cage 10).

[0325] In some aspects, (i) a key polypeptide comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 29 (Key 11), and (ii) the chimeric polypeptide to which the key polypeptide can bind comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 11 (Cage 11). In certain aspects, the key polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 29 (Key 11), and the chimeric polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 11 (Cage 11).

[0326] In some aspects, (i) a key polypeptide consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 29 (Key 11), and (ii) the chimeric polypeptide to which the key polypeptide can bind consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 11 (Cage 11). In certain aspects, the key polypeptide consists or consists essentially of the amino acid sequence set forth in SEQ ID NO: 29 (Key 11), and the chimeric polypeptide consists or consists essentially of the amino acid sequence set forth in SEQ ID NO: 11 (Cage 11).

[0327] In some aspects, (i) a key polypeptide comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 30 (Key 12), and (ii) the chimeric polypeptide to which the key polypeptide can bind comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 12 (Cage 12). In certain aspects, the key polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 30 (Key 12), and the chimeric polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 12 (Cage 12).

[0328] In some aspects, (i) a key polypeptide consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 30 (Key 12), and (ii) the chimeric polypeptide to which the key polypeptide can bind consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 12 (Cage 12). In certain aspects, the key polypeptide consists or consists essentially of the amino acid sequence set forth in SEQ ID NO: 30 (Key 12), and the chimeric polypeptide consists or consists essentially of the amino acid sequence set forth in SEQ ID NO: 12 (Cage 12).

[0329] In some aspects, (i) a key polypeptide comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 31 (Key 13), and (ii) the chimeric polypeptide to which the key polypeptide can bind comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 13 (Cage 13). In certain aspects, the key polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 31 (Key 13), and the chimeric polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 13 (Cage 13).

[0330] In some aspects, (i) a key polypeptide consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 31 (Key 13), and (ii) the chimeric polypeptide to which the key polypeptide can bind consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 13 (Cage 13). In certain aspects, the key polypeptide consists or consists essentially of the amino acid sequence set forth in SEQ ID NO: 31 (Key 13), and the chimeric polypeptide consists or consists essentially of the amino acid sequence set forth in SEQ ID NO: 13 (Cage 13). [0331] In some aspects, (i) a key polypeptide comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 31 (Key 14), and (ii) the chimeric polypeptide to which the key polypeptide can bind comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 14 (Cage 14). In certain aspects, the key polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 31 (key 14), and the chimeric polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 14 (Cage 14).

[0332] In some aspects, (i) a key polypeptide consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 31 (key 14), and (ii) the chimeric polypeptide to which the key polypeptide can bind consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 14 (Cage 14). In certain aspects, the key polypeptide consists or consists essentially of the amino acid sequence set forth in SEQ ID NO: 31 (key 14), and the chimeric polypeptide consists or consists essentially of the amino acid sequence set forth in SEQ ID NO: 14 (Cage

14).

[0333] In some aspects, (i) a key polypeptide comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 32 (Key 15), and (ii) the chimeric polypeptide to which the key polypeptide can bind comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 15 (Cage 15). In certain aspects, the key polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 32 (Key 15), and the chimeric polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 15 (Cage

15).

[0334] In some aspects, (i) a key polypeptide consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 32 (Key 15), and (ii) the chimeric polypeptide to which the key polypeptide can bind consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 15 (Cage 15). In certain aspects, the key polypeptide consists or consists essentially of the amino acid sequence set forth in SEQ ID NO: 32 (Key 15), and the chimeric polypeptide consists or consists essentially of the amino acid sequence set forth in SEQ ID NO: 15 (Cage 15).

[0335] In some aspects, (i) a key polypeptide comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 33 (Key 16), and (ii) the chimeric polypeptide to which the key polypeptide can bind comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 16 (Cage 16). In certain aspects, the key polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 33 (key 16), and the chimeric polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 16 (Cage 16).

[0336] In some aspects, (i) a key polypeptide consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 33 (Key 16), and (ii) the chimeric polypeptide to which the key polypeptide can bind consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 16 (Cage 16). In certain aspects, the key polypeptide consists or consists essentially of the amino acid sequence set forth in SEQ ID NO: 33 (key 16), and the chimeric polypeptide consists or consists essentially of the amino acid sequence set forth in SEQ ID NO: 16 (Cage 16).

[0337] In some aspects, (i) a key polypeptide comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 34 (Key 17), and (ii) the chimeric polypeptide to which the key polypeptide can bind comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 17 (Cage 17). In certain aspects, the key polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 34 (Key 17), and the chimeric polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 17 (Cage 17).

[0338] In some aspects, (i) a key polypeptide consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 34 (Key 17), and (ii) the chimeric polypeptide to which the key polypeptide can bind consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 17 (Cage 17). In certain aspects, the key polypeptide consists or consists essentially of the amino acid sequence set forth in SEQ ID NO: 34 (Key 17), and the chimeric polypeptide consists or consists essentially of the amino acid sequence set forth in SEQ ID NO: 17 (Cage

17).

[0339] In some aspects, (i) a key polypeptide comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 35 (Key 18), and (ii) the chimeric polypeptide to which the key polypeptide can bind comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 18 (Cage 18). In certain aspects, the key polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 35 (Key 18), and the chimeric polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 18 (Cage

18).

[0340] In some aspects, (i) a key polypeptide consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 35 (Key 18), and (ii) the chimeric polypeptide to which the key polypeptide can bind consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 18 (Cage 18). In certain aspects, the key polypeptide consists or consists essentially of the amino acid sequence set forth in SEQ ID NO: 35 (Key 18), and the chimeric polypeptide consists or consists essentially of the amino acid sequence set forth in SEQ ID NO: 18 (Cage 18).

II L Other Moieties

[0341] In some aspects, a chimeric polypeptide of the present disclosure can be used in combination with one or more additional moieties. For instance, as described herein, a chimeric polypeptide disclosed herein can be used in combination with a CAR or a TCR, where the chimeric polypeptide is incorporated in the intracellular portion of the CAR or TCR. In certain aspects, the chimeric polypeptide of the present disclosure is attached ( e.g ., fused) to the C- terminus of the CAR or TCR.

[0342] In some aspects, the chimeric polypeptide is inserted between two functional domains in the intracellular portion of the CAR or TCR. The transmembrane domain of a CAR is fused to the costimulatory domain, optionally a costimulatory domain is fused to a second costimulatory domain, and the costimulatory domain is fused to a signaling domain, not limited to CD3z. Accordingly, in some aspects, the chimeric polypeptide is inserted between the transmembrane domain and a costimulatory domain (e.g., a first costimulatory domain). In some aspects, the chimeric polypeptide is inserted between a first costimulatory domain and a second costimulatory domain. In some aspects, the chimeric polypeptide is inserted between a costimulatory domain and a signaling domain.

[0343] In some aspects, a chimeric polypeptide disclosed herein further comprises a signaling domain. In some aspects, the signaling domain comprises a domain derived from CD3zeta, FcR gamma, FcR beta, CD3 gamma, CD3 delta, CD3 epsilon, CD5, CD22, CD79a, CD79b, CD66d, or combinations thereof. [0344] In some aspects, a chimeric polypeptide disclosed herein further comprises a co stimulatory domain. In some aspects, the co-stimulatory domain comprises a domain derived from 2B4, HVEM, ICOS, LAG3, DAP10, DAP 12, CD27, CD28, 4-1BB (CD137), 0X40 (CD134), CD30, CD40, ICOS (CD278), glucocorticoid-induced tumor necrosis factor receptor (GITR), lymphocyte function-associated antigen- 1 (LFA-1), CD2, CD7, LIGHT, NKG2C, B7-H3, or combinations thereof.

[0345] In some aspects, a chimeric polypeptide disclosed herein further comprises an antigen-binding domain. In some aspects, the antigen-binding domain comprises an antibody or an antigen-binding fragment thereof that specifically binds to an epitope on a tumor antigen. In some aspects, the antigen binding domain is an IgNAR, a Fab, a Fab’, a F(ab)’2, a F(ab)’3, an Fv, a single chain variable fragment (scFv), a bis-scFv, a (scFv)2, a minibody, a diabody, a triabody, a tetrabody, an intrabody, a disulfide stabilized Fv protein (dsFv), a unibody, a nanobody, or combinations thereof. Non-limiting examples of antigens that the antigen binding domain can bind to includes CD19, TRAC, TCRP, BCMA, CLL-1, CS1, CD38, TSHR, CD123, CD22, CD30, CD70, CD171, CD33, EGFRvIII, GD2, GD3, Tn Ag, PSMA, ROR1, ROR2, GPC1, GPC2, FLT3, FAP, TAG72, CD44v6, CEA, EPCAM, B7H3, KIT, IL- 13Ra2, mesothelin, IL- IRa, PSCA, PRSS21, VEGFR2, LewisY, CD24, PDGFR-beta, SSEA- 4, CD20, folate receptor alpha, ERBB2 (Her2/neu), MUC1, MUC16, EGFR, NCAM, prostase, PAP, ELF2M, Ephrin B2, IGF-I receptor, CAIX, LMP2, gplOO, bcr-abl, tyrosinase, EphA2, fucosyl GM1, sLe, GM3, TGS5, HMWMAA, o-acetyl-GD2, folate receptor beta, TEM1/CD248, TEM7R, CLDN6, GPRC5D, CXORF61, CD97, CD 179a, ALK, Polysialic acid, PLAC1, GloboH, NY-BR-1, UPK2, HAVCR1, ADRB3, PANX3, GPR20, LY6K, OR51E2, TARP, WT1, NY-ESO-1, L AGE-1 a, MAGE-A1, legumain, HPV E6,E7, MAGE Al, ETV6-AML, sperm protein 17, XAGE1, Tie 2, MAD-CT-1, MAD-CT-2, Fos-related antigen 1, p53, p53 mutant, prostein, surviving, telomerase, PCTA- 1/Galectin 8, MelanA/MARTl, Ras mutant, hTERT, sarcoma translocation breakpoints, ML-IAP, ERG (TMPRSS2 ETS fusion gene), NA17, PAX3, androgen receptor, cyclin Bl, MYCN, RhoC, TRP-2, CYP1B1, BORIS, SART3, PAX5, OY-TES1, LCK, AKAP-4, SSX2, RAGE-1, human telomerase reverse transcriptase, RU1, RU2, intestinal carboxyl esterase, mut hsp70-2, CD79a, CD79b, CD72, LAIR1, FCAR, LILRA2, CD300LF, CLEC12A, BST2, EMR2, LY75, GPC3, FCRL5, IGLL1, CD2, CD3e, CD4, CD5, CD7, the extracellular portion of the APRIL protein, and any combinations thereof. [0346] In some aspects, a chimeric polypeptide disclosed herein further comprises transmembrane domain.

[0347] In some aspects, a chimeric polypeptide disclosed herein further comprises a chimeric antigen receptor (CAR), e.g. , a standard CAR, a split CAR, an off-C AR, an on-C AR, a first- generation CAR, a second-generation CAR, a third-generation CAR, or a fourth-generation CAR.

[0348] In some aspects, a chimeric polypeptide disclosed herein comprises a CAR comprising:

(i) a chimeric polypeptide disclosed herein;

(ii) an antigen-binding domain that binds to an epitope on a tumor antigen expressed on a target cell; and,

(iii) a transmembrane domain.

[0349] In some aspects, the CAR further comprises a CAR spacer between the antigen binding domain and the transmembrane domain. In some aspects, the chimeric polypeptide is distally linked to the cytoplasmic region of the CAR. In some aspects, the chimeric polypeptide is interposed between two domains in the cytoplasmic region of the CAR. In some aspects, the chimeric polypeptide is attached to the CAR via a linker or spacer. In some aspects, the CAR can comprise more than one chimeric polypeptide, which can be activated by the same key polypeptide or by different key polypeptides.

[0350] In some aspects, a chimeric polypeptide disclosed herein further comprises a T cell receptor (TCR).

[0351] In some aspects, a chimeric polypeptide disclosed herein, e.g. , a CAR or a TCR, can induce IFNy and/or IL-2 expression in a cell (e.g, a T cell).

[0352] In some aspects, the CAR that can be linked to the chimeric polypeptide of the present disclosure comprises a standard CAR, a split CAR, an off-switch CAR, an on-switch CAR, a first-generation CAR, a second-generation CAR, a third-generation CAR, or a fourth- generation CAR. [0353] In some aspects, a polypeptide of the present disclosure ( e.g ., a polypeptide comprising a chimeric polypeptide disclosed herein) is a CAR as set forth in ROR1 CAR + Cage 16 (SEQ ID NO: 36). In other aspects, a polypeptide of the present disclosure (e.g., a polypeptide comprising a chimeric polypeptide disclosed herein) is a CAR as set forth in ROR1 + Cage 11 (SEQ ID NO: 38).

[0354] In some aspects, the present disclosure also include a chimeric protein complex comprising the cage polypeptide of the present disclosure and the key polypeptide of the present disclosure, wherein the cage and key polypeptides are bound to each other. Once the key polypeptide is bound to the cage polypeptide, the degron peptide linked to the latch region can activate a ubiquitin dependent degradation pathway and the complex can be degraded by a ubiquitin system.

III. Polynucleotides

[0355] In some aspects, the present disclosure provides a polynucleotide encoding one or more components of a chimeric polypeptide of the present disclosure (i.e., comprising a degron linked to the C-terminus of the latch region).

[0356] In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide which comprises a cage polypeptide comprising:

(i) a structural region comprising an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 13 (Cage 13); SEQ ID NO: 14 (Cage 14); SEQ ID NO: 15 (Cage 15); SEQ ID NO: 16 (Cage 16); SEQ ID NO: 17 (Cage 17); SEQ ID NO: 18 (Cage 18); SEQ ID NO: 1 (Cage 1); SEQ ID NO: 2 (Cage 2); SEQ ID NO: 3 (Cage 3); SEQ ID NO: 4 (Cage 4); SEQ ID NO: 5 (Cage 5); SEQ ID NO: 6 (Cage 6); SEQ ID NO: 7 (Cage 7); SEQ ID NO: 8 (Cage 8); SEQ ID NO: 9 (Cage 9); SEQ ID NO: 10 (Cage 10); SEQ ID NO: 11 (Cage 11); or SEQ ID NO: 12 (Cage 12); and (ii) a latch region comprising a degron peptide comprising the amino acid sequence CGL, wherein the latch region is capable of binding to the structural region.

[0357] In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide which comprises a cage polypeptide comprising:

(i) a structural region comprising an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 13 (Cage 13); SEQ ID NO: 14 (Cage 14); SEQ ID NO: 15 (Cage 15); SEQ ID NO: 16 (Cage 16); SEQ ID NO: 17 (Cage 17); SEQ ID NO: 18 (Cage 18); SEQ ID NO: 1 (Cage 1); SEQ ID NO: 2 (Cage 2); SEQ ID NO: 3 (Cage 3); SEQ ID NO: 4 (Cage 4); SEQ ID NO: 5 (Cage 5); SEQ ID NO: 6 (Cage 6); SEQ ID NO: 7 (Cage 7); SEQ ID NO: 8 (Cage 8); SEQ ID NO: 9 (Cage 9); SEQ ID NO: 10 (Cage 10); SEQ ID NO: 11 (Cage 11); or SEQ ID NO: 12 (Cage 12); and

(ii) a latch region comprising a degron peptide consisting or consisting essentially of the amino acid sequence CGL, wherein the latch region is capable of binding to the structural region.

[0358] In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide which comprises a cage polypeptide comprising a structural region and a latch region, wherein the structural region comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to a structural region of SEQ ID NO: 13 (Cage 13), and the latch region is capable of binding to the structural region and comprises a degron peptide selected from CGL, YCGL (SEQ ID NO: 136), TYCGL (SEQ ID NO: 137), VTYCGL (SEQ ID NO: 138), RVTYCGL (SEQ ID NO: 139), IR VTYCGL (SEQ ID NO: 140), LIR VTYCGL (SEQ ID NO: 141), or VLIR VTYCGL (SEQ ID NO: 142). In certain aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide which comprises a cage polypeptide comprising a structural region and a latch region, wherein the structural region comprises the structural region of SEQ ID NO: 13 (Cage

13), and the latch region is capable of binding to the structural region and comprises a degron peptide selected from CGL, YCGL (SEQ ID NO: 136), TYCGL (SEQ ID NO: 137), VTYCGL (SEQ ID NO: 138), R VTYCGL (SEQ ID NO: 139), IR VTYCGL (SEQ ID NO: 140), LIR VTYCGL (SEQ ID NO: 141), or VLIR VTYCGL (SEQ ID NO: 142).

[0359] In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide which comprises a cage polypeptide comprising a structural region and a latch region, wherein the structural region comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to a structural region of SEQ ID NO: 14 (Cage 14), and the latch region is capable of binding to the structural region and comprises a degron peptide selected from CGL, YCGL (SEQ ID NO: 136), TYCGL (SEQ ID NO: 137), VTYCGL (SEQ ID NO: 138), RVTYCGL (SEQ ID NO: 139), IR VTYCGL (SEQ ID NO: 140), LIR VTYCGL (SEQ ID NO: 141), or VLIR VTYCGL (SEQ ID NO: 142). In certain aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide which comprises a cage polypeptide comprising a structural region and a latch region, wherein the structural region comprises the structural region of SEQ ID NO: 14 (Cage

14), and the latch region is capable of binding to the structural region and comprises a degron peptide selected from CGL, YCGL (SEQ ID NO: 136), TYCGL (SEQ ID NO: 137), VTYCGL (SEQ ID NO: 138), RVTYCGL (SEQ ID NO: 139), IR VTYCGL (SEQ ID NO: 140), LIR VTYCGL (SEQ ID NO: 141), or VLIR VTYCGL (SEQ ID NO: 142).

[0360] In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide which comprises a cage polypeptide comprising a structural region and a latch region, wherein the structural region comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to a structural region of SEQ ID NO: 15 (Cage 15), and the latch region is capable of binding to the structural region and comprises a degron peptide selected from CGL, YCGL (SEQ ID NO: 136), TYCGL (SEQ ID NO: 137), VTYCGL (SEQ ID NO: 138), RVTYCGL (SEQ ID NO: 139), IR VTYCGL (SEQ ID NO: 140), LIR VTYCGL (SEQ ID NO: 141), or VLIR VTYCGL (SEQ ID NO: 142). In certain aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide which comprises a cage polypeptide comprising a structural region and a latch region, wherein the structural region comprises the structural region of SEQ ID NO: 15 (Cage

15), and the latch region is capable of binding to the structural region and comprises a degron peptide selected from CGL, YCGL (SEQ ID NO: 136), TYCGL (SEQ ID NO: 137), VTYCGL (SEQ ID NO: 138), RVTYCGL (SEQ ID NO: 139), IR VTYCGL (SEQ ID NO: 140), LIR VTYCGL (SEQ ID NO: 141), or VLIR VTYCGL (SEQ ID NO: 142).

[0361] In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide which comprises a cage polypeptide comprising a structural region and a latch region, wherein the structural region comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to a structural region of SEQ ID NO: 16 (Cage 16), and the latch region is capable of binding to the structural region and comprises a degron peptide selected from CGL, YCGL (SEQ ID NO: 136), TYCGL (SEQ ID NO: 137), VTYCGL (SEQ ID NO: 138), RVTYCGL (SEQ ID NO: 139), IR VTYCGL (SEQ ID NO: 140), LIR VTYCGL (SEQ ID NO: 141), or VLIR VTYCGL (SEQ ID NO: 142). In certain aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide which comprises a cage polypeptide comprising a structural region and a latch region, wherein the structural region comprises the structural region of SEQ ID NO: 16 (Cage

16), and the latch region is capable of binding to the structural region and comprises a degron peptide selected from CGL, YCGL (SEQ ID NO: 136), TYCGL (SEQ ID NO: 137), VTYCGL (SEQ ID NO: 138), RVTYCGL (SEQ ID NO: 139), IR VTYCGL (SEQ ID NO: 140), LIR VTYCGL (SEQ ID NO: 141), or VLIR VTYCGL (SEQ ID NO: 142).

[0362] In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide which comprises a cage polypeptide comprising a structural region and a latch region, wherein the structural region comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to a structural region of SEQ ID NO: 17 (Cage 17), and the latch region is capable of binding to the structural region and comprises a degron peptide selected from CGL, YCGL (SEQ ID NO: 136), TYCGL (SEQ ID NO: 137), VTYCGL (SEQ ID NO: 138), RVTYCGL (SEQ ID NO: 139), IR VTYCGL (SEQ ID NO: 140), LIR VTYCGL (SEQ ID NO: 141), or VLIR VTYCGL (SEQ ID NO: 142). In certain aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide which comprises a cage polypeptide comprising a structural region and a latch region, wherein the structural region comprises the structural region of SEQ ID NO: 17 (Cage

17), and the latch region is capable of binding to the structural region and comprises a degron peptide selected from CGL, YCGL (SEQ ID NO: 136), TYCGL (SEQ ID NO: 137), VTYCGL (SEQ ID NO: 138), RVTYCGL (SEQ ID NO: 139), IR VTYCGL (SEQ ID NO: 140), LIR VTYCGL (SEQ ID NO: 141), or VLIR VTYCGL (SEQ ID NO: 142).

[0363] In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide which comprises a cage polypeptide comprising a structural region and a latch region, wherein the structural region comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to a structural region of SEQ ID NO: 18 (Cage 18), and the latch region is capable of binding to the structural region and comprises a degron peptide selected from CGL, YCGL (SEQ ID NO: 136), TYCGL (SEQ ID NO: 137), VTYCGL (SEQ ID NO: 138), RVTYCGL (SEQ ID NO: 139), IR VTYCGL (SEQ ID NO: 140), LIR VTYCGL (SEQ ID NO: 141), or VLIR VTYCGL (SEQ ID NO: 142). In certain aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide which comprises a cage polypeptide comprising a structural region and a latch region, wherein the structural region comprises the structural region of SEQ ID NO: 18 (Cage

18), and the latch region is capable of binding to the structural region and comprises a degron peptide selected from CGL, YCGL (SEQ ID NO: 136), TYCGL (SEQ ID NO: 137), VTYCGL (SEQ ID NO: 138), RVTYCGL (SEQ ID NO: 139), IR VTYCGL (SEQ ID NO: 140), LIR VTYCGL (SEQ ID NO: 141), or VLIR VTYCGL (SEQ ID NO: 142).

[0364] In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide of the present disclosure comprises a cage polypeptide comprising a structural region and a latch region, wherein the structural region comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to a structural region of SEQ ID NO: 1 (Cage 1), and the latch region is capable of binding to the structural region and comprises a degron peptide selected from CGL, YCGL (SEQ ID NO: 136), TYCGL (SEQ ID NO: 137), VTYCGL (SEQ ID NO: 138), RVTYCGL (SEQ ID NO: 139), IR VTYCGL (SEQ ID NO: 140), LIRVTYCGL (SEQ ID NO: 141), or VLIRVTYCGL (SEQ ID NO: 142). In certain aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide of the present disclosure comprises a cage polypeptide comprising a structural region and a latch region, wherein the structural region comprises the structural region of SEQ ID NO: 1 (Cage 1), and the latch region is capable of binding to the structural region and comprises a degron peptide selected from CGL, YCGL (SEQ ID NO: 136), TYCGL (SEQ ID NO: 137), VTYCGL (SEQ ID NO: 138), RVTYCGL (SEQ ID NO: 139), IR VTYCGL (SEQ ID NO: 140), LIRVTYCGL (SEQ ID NO: 141), or VLIRVTYCGL (SEQ ID NO: 142).

[0365] In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide of the present disclosure comprises a cage polypeptide comprising a structural region and a latch region, wherein the structural region comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to a structural region of SEQ ID NO: 2 (Cage 2), and the latch region is capable of binding to the structural region and comprises a degron peptide selected from CGL, YCGL (SEQ ID NO: 136), TYCGL (SEQ ID NO: 137), VTYCGL (SEQ ID NO: 138), RVTYCGL (SEQ ID NO: 139), IR VTYCGL (SEQ ID NO: 140), LIRVTYCGL (SEQ ID NO: 141), or VLIRVTYCGL (SEQ ID NO: 142). In certain aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide of the present disclosure comprises a cage polypeptide comprising a structural region and a latch region, wherein the structural region comprises the structural region of SEQ ID NO: 2 (Cage 2), and the latch region is capable of binding to the structural region and comprises a degron peptide selected from CGL, YCGL (SEQ ID NO: 136), TYCGL (SEQ ID NO: 137), VTYCGL (SEQ ID NO: 138), RVTYCGL (SEQ ID NO: 139), IR VTYCGL (SEQ ID NO: 140), LIRVTYCGL (SEQ ID NO: 141), or VLIRVTYCGL (SEQ ID NO: 142). [0366] In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide which comprises a cage polypeptide comprising a structural region and a latch region, wherein the structural region comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to a structural region of SEQ ID NO: 3 (Cage 3), and the latch region is capable of binding to the structural region and comprises a degron peptide selected from CGL, YCGL (SEQ ID NO: 136), TYCGL (SEQ ID NO: 137), VTYCGL (SEQ ID NO: 138), RVTYCGL (SEQ ID NO: 139), IR VTYCGL (SEQ ID NO: 140), LIR VTYCGL (SEQ ID NO: 141), or VLIR VTYCGL (SEQ ID NO: 142). In certain aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide which comprises a cage polypeptide comprising a structural region and a latch region, wherein the structural region comprises the structural region of SEQ ID NO: 3 (Cage 3), and the latch region is capable of binding to the structural region and comprises a degron peptide selected from CGL, YCGL (SEQ ID NO: 136), TYCGL (SEQ ID NO: 137), VTYCGL (SEQ ID NO: 138), RVTYCGL (SEQ ID NO: 139), IR VTYCGL (SEQ ID NO: 140), LIR VTYCGL (SEQ ID NO: 141), or VLIR VTYCGL (SEQ ID NO: 142).

[0367] In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide of the present disclosure comprises a cage polypeptide comprising a structural region and a latch region, wherein the structural region comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to a structural region of SEQ ID NO: 4 (Cage 4), and the latch region is capable of binding to the structural region and comprises a degron peptide selected from CGL, YCGL (SEQ ID NO: 136), TYCGL (SEQ ID NO: 137), VTYCGL (SEQ ID NO: 138), RVTYCGL (SEQ ID NO: 139), IR VTYCGL (SEQ ID NO: 140), LIRVTYCGL (SEQ ID NO: 141), or VLIRVTYCGL (SEQ ID NO: 142). In certain aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide of the present disclosure comprises a cage polypeptide comprising a structural region and a latch region, wherein the structural region comprises the structural region of SEQ ID NO: 4 (Cage 4), and the latch region is capable of binding to the structural region and comprises a degron peptide selected from CGL, YCGL (SEQ ID NO: 136), TYCGL (SEQ ID NO: 137), VTYCGL (SEQ ID NO: 138), RVTYCGL (SEQ ID NO: 139), IRVTYCGL (SEQ ID NO: 140), LIRVTYCGL (SEQ ID NO: 141), or VLIRVTYCGL (SEQ ID NO: 142).

[0368] In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide of the present disclosure comprises a cage polypeptide comprising a structural region and a latch region, wherein the structural region comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to a structural region of SEQ ID NO: 5 (Cage 5), and the latch region is capable of binding to the structural region and comprises a degron peptide selected from CGL, YCGL (SEQ ID NO: 136), TYCGL (SEQ ID NO: 137), VTYCGL (SEQ ID NO: 138), RVTYCGL (SEQ ID NO: 139), IRVTYCGL (SEQ ID NO: 140), LIRVTYCGL (SEQ ID NO: 141), or VLIRVTYCGL (SEQ ID NO: 142). In certain aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide of the present disclosure comprises a cage polypeptide comprising a structural region and a latch region, wherein the structural region comprises the structural region of SEQ ID NO: 5 (Cage 5), and the latch region is capable of binding to the structural region and comprises a degron peptide selected from CGL, YCGL (SEQ ID NO: 136), TYCGL (SEQ ID NO: 137), VTYCGL (SEQ ID NO: 138), RVTYCGL (SEQ ID NO: 139), IRVTYCGL (SEQ ID NO: 140), LIRVTYCGL (SEQ ID NO: 141), or VLIRVTYCGL (SEQ ID NO: 142).

[0369] In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide which comprises a cage polypeptide comprising a structural region and a latch region, wherein the structural region comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to a structural region of SEQ ID NO: 6 (Cage 6), and the latch region is capable of binding to the structural region and comprises a degron peptide selected from CGL, YCGL (SEQ ID NO: 136), TYCGL (SEQ ID NO: 137), VTYCGL (SEQ ID NO: 138), RVTYCGL (SEQ ID NO: 139), IRVTYCGL (SEQ ID NO: 140), LIRVTYCGL (SEQ ID NO: 141), or VLIRVTYCGL (SEQ ID NO: 142). In certain aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide which comprises a cage polypeptide comprising a structural region and a latch region, wherein the structural region comprises the structural region of SEQ ID NO: 6 (Cage

6), and the latch region is capable of binding to the structural region and comprises a degron peptide selected from CGL, YCGL (SEQ ID NO: 136), TYCGL (SEQ ID NO: 137), VTYCGL (SEQ ID NO: 138), R VTYCGL (SEQ ID NO: 139), IR VTYCGL (SEQ ID NO: 140), LIR VTYCGL (SEQ ID NO: 141), or VLIR VTYCGL (SEQ ID NO: 142).

[0370] In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide which comprises a cage polypeptide comprising a structural region and a latch region, wherein the structural region comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to a structural region of SEQ ID NO: 7 (Cage 7), and the latch region is capable of binding to the structural region and comprises a degron peptide selected from CGL, YCGL (SEQ ID NO: 136), TYCGL (SEQ ID NO: 137), VTYCGL (SEQ ID NO: 138), RVTYCGL (SEQ ID NO: 139), IR VTYCGL (SEQ ID NO: 140), LIR VTYCGL (SEQ ID NO: 141), or VLIR VTYCGL (SEQ ID NO: 142). . In certain aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide which comprises a cage polypeptide comprising a structural region and a latch region, wherein the structural region comprises the structural region of SEQ ID NO: 7 (Cage

7), and the latch region is capable of binding to the structural region and comprises a degron peptide selected from CGL, YCGL (SEQ ID NO: 136), TYCGL (SEQ ID NO: 137), VTYCGL (SEQ ID NO: 138), RVTYCGL (SEQ ID NO: 139), IR VTYCGL (SEQ ID NO: 140), LIR VTYCGL (SEQ ID NO: 141), or VLIR VTYCGL (SEQ ID NO: 142).

[0371] In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide which comprises a cage polypeptide comprising a structural region and a latch region, wherein the structural region comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to a structural region of SEQ ID NO: 8 (Cage 8), and the latch region is capable of binding to the structural region and comprises a degron peptide selected from CGL, YCGL (SEQ ID NO: 136), TYCGL (SEQ ID NO: 137), VTYCGL (SEQ ID NO: 138), RVTYCGL (SEQ ID NO: 139), IR VTYCGL (SEQ ID NO: 140), LIR VTYCGL (SEQ ID NO: 141), or VLIR VTYCGL (SEQ ID NO: 142). In certain aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide which comprises a cage polypeptide comprising a structural region and a latch region, wherein the structural region comprises the structural region of SEQ ID NO: 8 (Cage

8), and the latch region is capable of binding to the structural region and comprises a degron peptide selected from CGL, YCGL (SEQ ID NO: 136), TYCGL (SEQ ID NO: 137), VTYCGL (SEQ ID NO: 138), R VTYCGL (SEQ ID NO: 139), IR VTYCGL (SEQ ID NO: 140), LIR VTYCGL (SEQ ID NO: 141), or VLIR VTYCGL (SEQ ID NO: 142).

[0372] In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide which comprises a cage polypeptide comprising a structural region and a latch region, wherein the structural region comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to a structural region of SEQ ID NO: 9 (Cage 9), and the latch region is capable of binding to the structural region and comprises a degron peptide selected from CGL, YCGL (SEQ ID NO: 136), TYCGL (SEQ ID NO: 137), VTYCGL (SEQ ID NO: 138), RVTYCGL (SEQ ID NO: 139), IR VTYCGL (SEQ ID NO: 140), LIR VTYCGL (SEQ ID NO: 141), or VLIR VTYCGL (SEQ ID NO: 142). In certain aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide which comprises a cage polypeptide comprising a structural region and a latch region, wherein the structural region comprises the structural region of SEQ ID NO: 9 (Cage

9), and the latch region is capable of binding to the structural region and comprises a degron peptide selected from CGL, YCGL (SEQ ID NO: 136), TYCGL (SEQ ID NO: 137), VTYCGL (SEQ ID NO: 138), RVTYCGL (SEQ ID NO: 139), IR VTYCGL (SEQ ID NO: 140), LIR VTYCGL (SEQ ID NO: 141), or VLIR VTYCGL (SEQ ID NO: 142).

[0373] In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide which comprises a cage polypeptide comprising a structural region and a latch region, wherein the structural region comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to a structural region of SEQ ID NO: 10 (Cage 10), and the latch region is capable of binding to the structural region and comprises a degron peptide selected from CGL, YCGL (SEQ ID NO: 136), TYCGL (SEQ ID NO: 137), VTYCGL (SEQ ID NO: 138), RVTYCGL (SEQ ID NO: 139), IR VTYCGL (SEQ ID NO: 140), LIR VTYCGL (SEQ ID NO: 141), or VLIR VTYCGL (SEQ ID NO: 142). In certain aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide which comprises a cage polypeptide comprising a structural region and a latch region, wherein the structural region comprises the structural region of SEQ ID NO: 10 (Cage

10), and the latch region is capable of binding to the structural region and comprises a degron peptide selected from CGL, YCGL (SEQ ID NO: 136), TYCGL (SEQ ID NO: 137), VTYCGL (SEQ ID NO: 138), RVTYCGL (SEQ ID NO: 139), IR VTYCGL (SEQ ID NO: 140), LIR VTYCGL (SEQ ID NO: 141), or VLIR VTYCGL (SEQ ID NO: 142).

[0374] In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide which comprises a cage polypeptide comprising a structural region and a latch region, wherein the structural region comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to a structural region of SEQ ID NO: 11 (Cage 11), and the latch region is capable of binding to the structural region and comprises a degron peptide selected from CGL, YCGL (SEQ ID NO: 136), TYCGL (SEQ ID NO: 137), VTYCGL (SEQ ID NO: 138), RVTYCGL (SEQ ID NO: 139), IR VTYCGL (SEQ ID NO: 140), LIR VTYCGL (SEQ ID NO: 141), or VLIR VTYCGL (SEQ ID NO: 142). In certain aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide which comprises a cage polypeptide comprising a structural region and a latch region, wherein the structural region comprises the structural region of SEQ ID NO: 11 (Cage

11), and the latch region is capable of binding to the structural region and comprises a degron peptide selected from CGL, YCGL (SEQ ID NO: 136), TYCGL (SEQ ID NO: 137), VTYCGL (SEQ ID NO: 138), RVTYCGL (SEQ ID NO: 139), IR VTYCGL (SEQ ID NO: 140), LIR VTYCGL (SEQ ID NO: 141), or VLIR VTYCGL (SEQ ID NO: 142).

[0375] In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide which comprises a cage polypeptide comprising a structural region and a latch region, wherein the structural region comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to a structural region of SEQ ID NO: 12 (Cage 12), and the latch region is capable of binding to the structural region and comprises a degron peptide selected from CGL, YCGL (SEQ ID NO: 136), TYCGL (SEQ ID NO: 137), VTYCGL (SEQ ID NO: 138), RVTYCGL (SEQ ID NO: 139), IR VTYCGL (SEQ ID NO: 140), LIR VTYCGL (SEQ ID NO: 141), or VLIR VTYCGL (SEQ ID NO: 142). In certain aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide which comprises a cage polypeptide comprising a structural region and a latch region, wherein the structural region comprises the structural region of SEQ ID NO: 12 (Cage 12), and the latch region is capable of binding to the structural region and comprises a degron peptide selected from CGL, YCGL (SEQ ID NO: 136), TYCGL (SEQ ID NO: 137), VTYCGL (SEQ ID NO: 138), RVTYCGL (SEQ ID NO: 139), IR VTYCGL (SEQ ID NO: 140), LIR VTYCGL (SEQ ID NO: 141), or VLIR VTYCGL (SEQ ID NO: 142).

[0376] In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide comprising a cage polypeptide, wherein the cage polypeptide comprises any one of the amino acid sequences set forth in SEQ ID NO: 13 (Cage 13); SEQ ID NO: 14 (Cage 14); SEQ ID NO: 15 (Cage 15); SEQ ID NO: 16 (Cage 16); SEQ ID NO: 17 (Cage 17); SEQ ID NO: 18 (Cage 18); SEQ ID NO: 1 (Cage 1); SEQ ID NO: 2 (Cage 2); SEQ ID NO: 3 (Cage 3); SEQ ID NO: 4 (Cage 4); SEQ ID NO: 5 (Cage 5); SEQ ID NO: 6 (Cage 6); SEQ ID NO: 7 (Cage 7); SEQ ID NO: 8 (Cage 8); SEQ ID NO: 9 (Cage 9); SEQ ID NO: 10 (Cage 10); SEQ ID NO: 11 (Cage 11); or SEQ ID NO: 12 (Cage 12).

[0377] In some aspects, a polynucleotide encodes a chimeric polypeptide comprising a cage polypeptide, wherein the cage polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 13 (Cage 13). In some aspects, a polynucleotide encodes a chimeric polypeptide comprising a cage polypeptide, wherein the cage polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 14 (Cage 14). In some aspects, a polynucleotide encodes a chimeric polypeptide comprising a cage polypeptide, wherein the cage polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 15 (Cage 15). In some aspects, a polynucleotide encodes a chimeric polypeptide comprising a cage polypeptide, wherein the cage polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 16 (Cage 16). In some aspects, a polynucleotide encodes a chimeric polypeptide comprising a cage polypeptide, wherein the cage polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 17 (Cage 17). In some aspects, a polynucleotide encodes a chimeric polypeptide comprising a cage polypeptide, wherein the cage polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 18 (Cage 18). In some aspects, a polynucleotide encodes a chimeric polypeptide comprising a cage polypeptide, wherein the cage polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 1 (Cage 1). In some aspects, a polynucleotide encodes a chimeric polypeptide comprising a cage polypeptide, wherein the cage polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 2 (Cage 2). In some aspects, a polynucleotide encodes a chimeric polypeptide comprising a cage polypeptide, wherein the cage polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 3 (Cage 3). In some aspects, a polynucleotide encodes a chimeric polypeptide comprising a cage polypeptide, wherein the cage polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 4 (Cage 4). In some aspects, a polynucleotide encodes a chimeric polypeptide comprising a cage polypeptide, wherein the cage polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 5 (Cage 5). In some aspects, a polynucleotide encodes a chimeric polypeptide comprising a cage polypeptide, wherein the cage polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 6 (Cage 6). In some aspects, a polynucleotide encodes a chimeric polypeptide comprising a cage polypeptide, wherein the cage polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 7 (Cage 7). In some aspects, a polynucleotide encodes a chimeric polypeptide comprising a cage polypeptide, wherein the cage polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 8 (Cage 8). In some aspects, a polynucleotide encodes a chimeric polypeptide comprising a cage polypeptide, wherein the cage polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 9 (Cage 9). In some aspects, a polynucleotide encodes a chimeric polypeptide comprising a cage polypeptide, wherein the cage polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 10 (Cage 10). In some aspects, a polynucleotide encodes a chimeric polypeptide comprising a cage polypeptide, wherein the cage polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 11 (Cage 11). In some aspects, a polynucleotide encodes a chimeric polypeptide comprising a cage polypeptide, wherein the cage polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 12 (Cage 12).

[0378] In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, wherein the degron peptide is linked to the C-terminus of the amino acid sequence set forth in SEQ ID NO: 13 (Cage 13). In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, wherein the degron peptide is linked to the C-terminus of the amino acid sequence set forth in SEQ ID NO: 14 (Cage 14). In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, wherein the degron peptide is linked to the C-terminus of the amino acid sequence set forth in SEQ ID NO: 15 (Cage 15). In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, wherein the degron peptide is linked to the C-terminus of the amino acid sequence set forth in SEQ ID NO: 16 (Cage 16). In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, wherein the degron peptide is linked to the C-terminus of the amino acid sequence set forth in SEQ ID NO: 17 (Cage 17). In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, wherein the degron peptide is linked to the C-terminus of the amino acid sequence set forth in SEQ ID NO: 18 (Cage 18). In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide wherein the degron peptide is linked to the C-terminus of the amino acid sequence set forth in SEQ ID NO: 1 (Cage 1). In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, wherein the degron peptide is linked to the C-terminus of the amino acid sequence set forth in SEQ ID NO: 2 (Cage 2). In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, wherein the degron peptide is linked to the C-terminus of the amino acid sequence set forth in SEQ ID NO: 3 (Cage 3). In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, wherein the degron peptide is linked to the C-terminus of the amino acid sequence set forth in SEQ ID NO: 4 (Cage 4). In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, wherein the degron peptide is linked to the C-terminus of the amino acid sequence set forth in SEQ ID NO: 5 (Cage 5). In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, wherein the degron peptide is linked to the C-terminus of the amino acid sequence set forth in SEQ ID NO: 6 (Cage 6). In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, wherein the degron peptide is linked to the C-terminus of the amino acid sequence set forth in SEQ ID NO: 7 (Cage 7). In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, wherein the degron peptide is linked to the C-terminus of the amino acid sequence set forth in SEQ ID NO: 8 (Cage 8). In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, wherein the degron peptide is linked to the C-terminus of the amino acid sequence set forth in SEQ ID NO: 9 (Cage 9). In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, wherein the degron peptide is linked to the C-terminus of the amino acid sequence set forth in SEQ ID NO: 10 (Cage 10). In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, wherein the degron peptide is linked to the C-terminus of the amino acid sequence set forth in SEQ ID NO: 11 (Cage 11). In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, wherein the degron peptide is linked to the C-terminus of the amino acid sequence set forth in SEQ ID NO: 12 (Cage 12). [0379] As disclosed herein, in some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, wherein the degron peptide comprises, consists, or consists essentially of the amino acid sequence of CGL, YCGL (SEQ ID NO: 136), TYCGL (SEQ ID NO: 137), VTYCGL (SEQ ID NO: 138), RVTYCGL (SEQ ID NO: 139), IRVTYCGL (SEQ ID NO: 140), LIR VTYCGL (SEQ ID NO: 141), or VLIR VTYCGL (SEQ ID NO: 142). In certain aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, wherein the degron peptide comprises an amino acid sequence that is at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 80%, at least about 90%, or about 100% identical to VLIR VTYCGL (SEQ ID NO: 142).

[0380] In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, wherein the degron peptide comprises the amino acid sequence of CGL. In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, wherein the degron peptide comprises the amino acid sequence of YCGL (SEQ ID NO: 136). In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, wherein the degron peptide comprises the amino acid sequence of TYCGL (SEQ ID NO: 137). In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, wherein the degron peptide comprises the amino acid sequence of VTYCGL (SEQ ID NO: 138). In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, wherein the degron peptide comprises the amino acid sequence of RVTYCGL (SEQ ID NO: 139). In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, wherein the degron peptide comprises the amino acid sequence of IRVTYCGL (SEQ ID NO: 140). In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, wherein the degron peptide comprises the amino acid sequence of LIRVTYCGL (SEQ ID NO: 141). In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, wherein the degron peptide comprises the amino acid sequence of VLIR VTYCGL (SEQ ID NO: 142).

[0381] In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, wherein the degron peptide consists or consists essentially of the amino acid sequence of CGL. In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, wherein the degron peptide consists or consists essentially of the amino acid sequence of YCGL (SEQ ID NO: 136). In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, wherein the degron peptide consists or consists essentially of the amino acid sequence of TYCGL (SEQ ID NO: 137). In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, wherein the degron peptide consists or consists essentially of the amino acid sequence of VTYCGL (SEQ ID NO: 138). In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, wherein the degron peptide consists or consists essentially of the amino acid sequence of RVTYCGL (SEQ ID NO: 139). In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, wherein the degron peptide consists or consists essentially of the amino acid sequence of IRVTYCGL (SEQ ID NO: 140). In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, wherein the degron peptide consists or consists essentially of the amino acid sequence of LIR VTYCGL (SEQ ID NO: 141). In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, wherein the degron peptide consists or consists essentially of the amino acid sequence of VLIR VTYCGL (SEQ ID NO: 142).

[0382] In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, which comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 71%, at least about 72%, at least about 73%, at least about 74%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 1 (Cage 1). In certain aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, which comprises the amino acid sequence set forth in SEQ ID NO: 1 (Cage 1).

[0383] In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, which consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 71%, at least about 72%, at least about 73%, at least about 74%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 1 (Cage 1). In certain aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, which consists or consists essentially of the amino acid sequence set forth in SEQ ID NO: 1 (Cage 1).

[0384] In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, which comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 71%, at least about 72%, at least about 73%, at least about 74%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 2 (Cage 2). In certain aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, which comprises the amino acid sequence set forth in SEQ ID NO: 2 (Cage 2).

[0385] In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, which consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 71%, at least about 72%, at least about 73%, at least about 74%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 2 (Cage 2). In certain aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, which consists or consists essentially of the amino acid sequence set forth in SEQ ID NO: 2 (Cage 2).

[0386] In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, which comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 71%, at least about 72%, at least about 73%, at least about 74%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 3 (Cage 3). In certain aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, which comprises the amino acid sequence set forth in SEQ ID NO: 3 (Cage 3).

[0387] In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, which consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 71%, at least about 72%, at least about 73%, at least about 74%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 3 (Cage 3). In certain aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, which consists or consists essentially of the amino acid sequence set forth in SEQ ID NO: 3 (Cage 3).

[0388] In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, which comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 71%, at least about 72%, at least about 73%, at least about 74%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 4 (Cage 4). In certain aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, which comprises the amino acid sequence set forth in SEQ ID NO: 4 (Cage 4). [0389] In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, which consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 71%, at least about 72%, at least about 73%, at least about 74%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 4 (Cage 4). In certain aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, which consists or consists essentially of the amino acid sequence set forth in SEQ ID NO: 4 (Cage 4).

[0390] In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, which comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 71%, at least about 72%, at least about 73%, at least about 74%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 5 (Cage 5). In certain aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, which comprises the amino acid sequence set forth in SEQ ID NO: 5 (Cage 5).

[0391] In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, which consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 71%, at least about 72%, at least about 73%, at least about 74%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 5 (Cage 5). In certain aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, which consists or consists essentially of the amino acid sequence set forth in SEQ ID NO: 5 (Cage 5).

[0392] In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, which comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 71%, at least about 72%, at least about 73%, at least about 74%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 6 (Cage 6). In certain aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, which comprises the amino acid sequence set forth in SEQ ID NO: 6 (Cage 6).

[0393] In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, which consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 71%, at least about 72%, at least about 73%, at least about 74%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 6 (Cage 6). In certain aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, which consists or consists essentially of the amino acid sequence set forth in SEQ ID NO: 6 (Cage 6).

[0394] In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, which comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 71%, at least about 72%, at least about 73%, at least about 74%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 7 (Cage 7). In certain aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, which comprises the amino acid sequence set forth in SEQ ID NO: 7 (Cage 7).

[0395] In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, which consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 71%, at least about 72%, at least about 73%, at least about 74%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 7 (Cage 7). In certain aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, which consists or consists essentially of the amino acid sequence set forth in SEQ ID NO: 7 (Cage 7).

[0396] In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, which comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 71%, at least about 72%, at least about 73%, at least about 74%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 8 (Cage 8). In certain aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, which comprises the amino acid sequence set forth in SEQ ID NO: 8 (Cage 8). [0397] In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, which consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 71%, at least about 72%, at least about 73%, at least about 74%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 8 (Cage 8). In certain aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, which consists or consists essentially of the amino acid sequence set forth in SEQ ID NO: 8 (Cage 8).

[0398] In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, which comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 71%, at least about 72%, at least about 73%, at least about 74%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 9 (Cage 9). In certain aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, which comprises the amino acid sequence set forth in SEQ ID NO: 9 (Cage 9).

[0399] In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, which consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 71%, at least about 72%, at least about 73%, at least about 74%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 9 (Cage 9). In certain aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, which consists or consists essentially of the amino acid sequence set forth in SEQ ID NO: 9 (Cage 9).

[0400] In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, which comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 71%, at least about 72%, at least about 73%, at least about 74%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 10 (Cage 10). In certain aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, which comprises the amino acid sequence set forth in SEQ ID NO: 10 (Cage 10).

[0401] In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, which consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 71%, at least about 72%, at least about 73%, at least about 74%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 10 (Cage 10). In certain aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, which consists or consists essentially of the amino acid sequence set forth in SEQ ID NO: 10 (Cage 10).

[0402] In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, which comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 71%, at least about 72%, at least about 73%, at least about 74%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 11 (Cage 11). In certain aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, which comprises the amino acid sequence set forth in SEQ ID NO: 11 (Cage 11).

[0403] In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, which consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 71%, at least about 72%, at least about 73%, at least about 74%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 11 (Cage 11). In certain aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, which consists or consists essentially of the amino acid sequence set forth in SEQ ID NO: 11 (Cage 11).

[0404] In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, which comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 71%, at least about 72%, at least about 73%, at least about 74%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 12 (Cage 12). In certain aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, which comprises the amino acid sequence set forth in SEQ ID NO: 12 (Cage 12).

[0405] In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, which consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 71%, at least about 72%, at least about 73%, at least about 74%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 12 (Cage 12). In certain aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, which consists or consists essentially of the amino acid sequence set forth in SEQ ID NO: 12 (Cage 12).

[0406] In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, which comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 71%, at least about 72%, at least about 73%, at least about 74%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 13 (Cage 13). In certain aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, which comprises the amino acid sequence set forth in SEQ ID NO: 13 (Cage 13).

[0407] In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, which consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 71%, at least about 72%, at least about 73%, at least about 74%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 13 (Cage 13). In certain aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, which consists or consists essentially of the amino acid sequence set forth in SEQ ID NO: 13 (Cage 13).

[0408] In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, which comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 71%, at least about 72%, at least about 73%, at least about 74%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 14 (Cage 14). In certain aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, which comprises the amino acid sequence set forth in SEQ ID NO: 14 (Cage 14).

[0409] In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, which consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 71%, at least about 72%, at least about 73%, at least about 74%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 14 (Cage 14). In certain aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, which consists or consists essentially of the amino acid sequence set forth in SEQ ID NO: 14 (Cage

14).

[0410] In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, which comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 71%, at least about 72%, at least about 73%, at least about 74%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 15 (Cage 15). In certain aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, which comprises the amino acid sequence set forth in SEQ ID NO: 15 (Cage 15).

[0411] In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, which consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 71%, at least about 72%, at least about 73%, at least about 74%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 15 (Cage 15). In certain aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, which consists or consists essentially of the amino acid sequence set forth in SEQ ID NO: 15 (Cage

15).

[0412] In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, which comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 71%, at least about 72%, at least about 73%, at least about 74%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 16 (Cage 16). In certain aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, which comprises the amino acid sequence set forth in SEQ ID NO: 16 (Cage 16).

[0413] In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, which consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 71%, at least about 72%, at least about 73%, at least about 74%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 16 (Cage 16). In certain aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, which consists or consists essentially of the amino acid sequence set forth in SEQ ID NO: 16 (Cage 16).

[0414] In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, which comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 71%, at least about 72%, at least about 73%, at least about 74%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 17 (Cage 17). In certain aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, which comprises the amino acid sequence set forth in SEQ ID NO: 17 (Cage 17). [0415] In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, which consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 71%, at least about 72%, at least about 73%, at least about 74%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 17 (Cage 17). In certain aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, which consists or consists essentially of the amino acid sequence set forth in SEQ ID NO: 17 (Cage 17).

[0416] In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, which comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 71%, at least about 72%, at least about 73%, at least about 74%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 18 (Cage 18). In certain aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, which comprises the amino acid sequence set forth in SEQ ID NO: 18 (Cage 18).

[0417] In some aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, which consists or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 71%, at least about 72%, at least about 73%, at least about 74%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 18 (Cage 18). In certain aspects, a polynucleotide disclosed herein encodes a chimeric polypeptide, which consists or consists essentially of the amino acid sequence set forth in SEQ ID NO: 18 (Cage 18).

[0418] In some aspects, a polynucleotide encoding a chimeric polypeptide disclosed herein further comprises a nucleic acid sequence encoding a signaling domain. In some aspects, the signaling domain comprises a domain derived from CD3zeta, FcR gamma, FcR beta, CD3 gamma, CD3 delta, CD3 epsilon, CD5, CD22, CD79a, CD79b, CD66d, or combinations thereof.

[0419] In some aspects, a polynucleotide encoding a chimeric polypeptide disclosed herein further comprises a nucleic acid sequence encoding a co-stimulatory domain. In some aspects, the co-stimulatory domain comprises a domain derived from 2B4, HVEM, ICOS, LAG3, DAP10, DAP 12, CD27, CD28, 4-1BB (CD137), 0X40 (CD134), CD30, CD40, ICOS (CD278), glucocorticoid-induced tumor necrosis factor receptor (GITR), lymphocyte function- associated antigen- 1 (LFA-1), CD2, CD7, LIGHT, NKG2C, B7-H3, or combinations thereof.

[0420] In some aspects, a polynucleotide encoding a chimeric polypeptide disclosed herein further comprises a nucleic acid sequence encoding an antigen-binding domain. In some aspects, the antigen-binding domain comprises an antibody or an antigen-binding fragment thereof that specifically binds to an epitope on a tumor antigen. In some aspects, the antigen binding domain is an IgNAR, a Fab, a Fab’, a F(ab)’2, a F(ab)’3, an Fv, a single chain variable fragment (scFv), a bis-scFv, a (scFv)2, a minibody, a diabody, a triabody, a tetrabody, an intrabody, a disulfide stabilized Fv protein (dsFv), a unibody, a nanobody, or combinations thereof. Non-limiting examples of antigens that the antigen-binding domain can bind to includes CD19, TRAC, TCRp, BCMA, CLL-1, CS1, CD38, TSHR, CD123, CD22, CD30, CD70, CD171, CD33, EGFRvIII, GD2, GD3, Tn Ag, PSMA, ROR1, ROR2, GPC1, GPC2, FLT3, FAP, TAG72, CD44v6, CEA, EPCAM, B7H3, KIT, IL-13Ra2, mesothelin, IL-IRa, PSCA, PRSS21, VEGFR2, LewisY, CD24, PDGFR-beta, SSEA-4, CD20, folate receptor alpha, ERBB2 (Her2/neu), MUC1, MUC16, EGFR, NCAM, prostase, PAP, ELF2M, Ephrin B2, IGF-I receptor, CAIX, LMP2, gplOO, bcr-abl, tyrosinase, EphA2, fucosyl GM1, sLe, GM3, TGS5, HMWMAA, o-acetyl-GD2, folate receptor beta, TEM1/CD248, TEM7R, CLDN6, GPRC5D, CXORF61, CD97, CD 179a, ALK, Poly sialic acid, PLAC1, GloboH, NY-BR-1, UPK2, HAVCR1, ADRB3, PANX3, GPR20, LY6K, OR51E2, TARP, WT1, NY-ESO-1, LAGE4a, MAGE-A1, legumain, HPV E6,E7, MAGE Al, ETV6-AML, sperm protein 17, XAGE1, Tie 2, MAD-CT-1, MAD-CT- 2, Fos-related antigen 1, p53, p53 mutant, prostein, surviving, telomerase, PCTA- 1/Galectin 8, MelanA/MARTl, Ras mutant, hTERT, sarcoma translocation breakpoints, ML-IAP, ERG (TMPRSS2 ETS fusion gene), NA17, PAX3, androgen receptor, cyclin Bl, MYCN, RhoC, TRP-2, CYPIBI, BORIS, SART3, PAX5, OY- TES1, LCK, AKAP-4, SSX2, RAGE-1, human telomerase reverse transcriptase, RU1, RU2, intestinal carboxyl esterase, mut hsp70-2, CD79a, CD79b, CD72, LAIR1, FCAR, LILRA2, CD300LF, CLEC12A, BST2, EMR2, LY75, GPC3, FCRL5, IGLL1, CD2, CD3e, CD4, CD5, CD7, the extracellular portion of the APRIL protein, and any combinations thereof.

[0421] In some aspects, a polynucleotide encoding a chimeric polypeptide disclosed herein further comprises a nucleic acid sequence encoding a transmembrane domain.

[0422] In some aspects, a polynucleotide encoding a chimeric polypeptide disclosed herein further comprises a nucleic acid encoding a chimeric antigen receptor (CAR), e.g ., a standard CAR, a split CAR, an off-CAR, an on-CAR, a first-generation CAR, a second-generation CAR, a third-generation CAR, or a fourth-generation CAR.

[0423] In some aspects, a polynucleotide encoding a chimeric polypeptide disclosed herein encodes a CAR comprising:

(i) a chimeric polypeptide disclosed herein;

(iii) a transmembrane domain.

[0424] In some aspects, a polynucleotide encoding a chimeric polypeptide disclosed herein further comprises a nucleic acid sequence encoding a T cell receptor (TCR).

[0425] In some aspects, a polynucleotide encoding a chimeric polypeptide disclosed herein, e.g. , a CAR or a TCR comprising a chimeric polypeptide, can induce IFNy and/or IL-2 expression in a cell (e.g, a T cell). [0426] In some aspects, a polynucleotide comprising a nucleic acid sequence encoding a chimeric polypeptide disclosed herein can further comprise a nucleic acid sequence encoding a key polypeptide, e.g ., an inducible key polypeptide. In some aspects, the nucleic acid sequence encoding the chimeric polypeptide and the nucleic acid sequence encoding the key polypeptide can be on the same sequence. In some aspects, the nucleic acid sequence encoding the chimeric polypeptide and the nucleic acid sequence encoding the key polypeptide can be on different sequences. As described herein, the key polypeptide is capable of inhibiting binding of the latch region to the structural region of the chimeric polypeptide when the key polypeptide comes in contact with the chimeric polypeptide. In other words, the presence of a key polypeptide that preferentially binds to the structural region of the cage displaces the latch, and therefore the degron sequence contained in the latch becomes physiologically active.

[0427] In some aspects, the present disclosure also provides a polynucleotide set comprising a first polynucleotide and a second polynucleotide, wherein the first polynucleotide comprises a nucleic acid sequence encoding a chimeric polypeptide (e.g, those described above), and the second polynucleotide comprises a nucleic acid sequence encoding a key polypeptide.

[0428] In some aspects, the second polynucleotide of a polynucleotide set disclosed herein encodes a key polypeptide, which comprises, consists, or consists essentially of an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65% least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence as set forth in SEQ ID NO: 19 (Key 1), SEQ ID NO: 20 (Key 2), SEQ ID NO: 21 (Key 3), SEQ ID NO: 22 (Key 4), SEQ ID NO: 23 (Key 5), SEQ ID NO: 24 (Key 6), SEQ ID NO: 25 (Key 7), SEQ ID NO: 26 (Key 8), SEQ ID NO: 27 (Key 9), SEQ ID NO: 28 (Key 10), SEQ ID NO: 29 (Key 11), SEQ ID NO: 30 (Key 12), SEQ ID NO: 31 (Key 13), SEQ ID NO: 32 (Key 15), SEQ ID NO: 33 (Key 16), SEQ ID NO: 34 (Key 17), or SEQ ID NO: 35 (Key 18), wherein the key polypeptide is capable of binding to the structural region of the chimeric polypeptide.

[0429] In some aspects, the present disclosure provides

(a) a polynucleotide that comprises a nucleic acid sequence encoding a chimeric polypeptide disclosed herein and further comprises a nucleic acid sequence encoding a key polypeptide, e.g, an inducible key polypeptide; or, (b) a polynucleotide set, wherein a first polynucleotide comprises a nucleic acid sequence encoding a chimeric polypeptide, and a second polypeptide comprises a nucleic acid sequence encoding a key polypeptide, wherein

(i) the chimeric polypeptide comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 71%, at least about 72%, at least about 73%, at least about 74%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 1 (Cage 1), and

(ii) the key polypeptide comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 71%, at least about 72%, at least about 73%, at least about 74%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 19 (Key 1). In certain aspects, (i) the chimeric polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 1 (Cage 1), and (ii) the key polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 19 (Key 1).

[0430] In some aspects, the present disclosure provides

(a) a polynucleotide that comprises a nucleic acid sequence encoding a chimeric polypeptide disclosed herein and further comprises a nucleic acid sequence encoding a key polypeptide, e.g ., an inducible key polypeptide; or, (b) a polynucleotide set, wherein a first polynucleotide comprises a nucleic acid sequence encoding a chimeric polypeptide, and a second polypeptide comprises a nucleic acid sequence encoding a key polypeptide; wherein

(i) the chimeric polypeptide comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 71%, at least about 72%, at least about 73%, at least about 74%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 2 (Cage 2), and

(ii) the key polypeptide comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 71%, at least about 72%, at least about 73%, at least about 74%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 20 (Key 2). In certain aspects, (i) the chimeric polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 2 (Cage 2), and (ii) the key polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 20 (Key 2).

[0431] In some aspects, the present disclosure provides

(i) the chimeric polypeptide comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 71%, at least about 72%, at least about 73%, at least about 74%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 3 (Cage 3), and

(ii) the key polypeptide comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 71%, at least about 72%, at least about 73%, at least about 74%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 21 (Key 3). In certain aspects, (i) the chimeric polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 3 (Cage 3), and (ii) the key polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 21 (Key 3).

[0432] In some aspects, the present disclosure provides

(a) a polynucleotide that comprises a nucleic acid sequence encoding a chimeric polypeptide disclosed herein and further comprises a nucleic acid sequence encoding a key polypeptide, e.g ., an inducible key polypeptide; or, (b) a polynucleotide set, wherein a first polynucleotide comprises a nucleic acid sequence encoding a chimeric polypeptide, and a second polypeptide comprises a nucleic acid sequence encoding a key polypeptide, wherein

(i) the chimeric polypeptide comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 71%, at least about 72%, at least about 73%, at least about 74%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 4 (Cage 4), and

(ii) the key polypeptide comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 71%, at least about 72%, at least about 73%, at least about 74%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 22 (Key 4). In certain aspects, (i) the chimeric polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 4 (Cage 4), and (ii) the key polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 22 (Key 4).

[0433] In some aspects, the present disclosure provides

(i) the chimeric polypeptide comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 71%, at least about 72%, at least about 73%, at least about 74%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 5 (Cage 5), and

(ii) the key polypeptide comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 71%, at least about 72%, at least about 73%, at least about 74%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 23 (Key 5). In certain aspects, (i) the chimeric polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 5 (Cage 5), and (ii) the key polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 23 (Key 5).

[0434] In some aspects, the present disclosure provides

(i) the chimeric polypeptide comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 71%, at least about 72%, at least about 73%, at least about 74%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 6 (Cage 6), and

(ii) the key polypeptide comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 71%, at least about 72%, at least about 73%, at least about 74%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 24 (Key 6). In certain aspects, (i) the chimeric polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 6 (Cage 6), and (ii) the key polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 24 (Key 6).

[0435] In some aspects, the present disclosure provides

(i) the chimeric polypeptide comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 71%, at least about 72%, at least about 73%, at least about 74%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 7 (Cage 7), and

(ii) the key polypeptide comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 71%, at least about 72%, at least about 73%, at least about 74%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 25 (Key 7). In certain aspects, (i) the chimeric polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 7 (Cage 7), and (ii) the key polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 25 (Key 7).

[0436] In some aspects, the present disclosure provides

(i) the chimeric polypeptide comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 71%, at least about 72%, at least about 73%, at least about 74%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 8 (Cage 8), and

(ii) the key polypeptide comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 71%, at least about 72%, at least about 73%, at least about 74%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 26 (Key 8). In certain aspects, (i) the chimeric polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 8 (Cage 8), and (ii) the key polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 26 (Key 8).

[0437] In some aspects, the present disclosure provides

(i) the chimeric polypeptide comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 71%, at least about 72%, at least about 73%, at least about 74%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 9 (Cage 9), and

(ii) the key polypeptide comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 71%, at least about 72%, at least about 73%, at least about 74%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 27 (Key 9). In certain aspects, (i) the chimeric polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 9 (Cage 9), and (ii) the key polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 27 (Key 9).

[0438] In some aspects, the present disclosure provides

(i) the chimeric polypeptide comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 71%, at least about 72%, at least about 73%, at least about 74%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 10 (Cage 10), and

(ii) the key polypeptide comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 71%, at least about 72%, at least about 73%, at least about 74%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 28 (Key 10). In certain aspects, (i) the chimeric polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 10 (Cage 10), and (ii) the key polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 28 (Key 10).

[0439] In some aspects, the present disclosure provides

(i) the chimeric polypeptide comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 71%, at least about 72%, at least about 73%, at least about 74%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 11 (Cage 11), and

(ii) the key polypeptide comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 71%, at least about 72%, at least about 73%, at least about 74%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 29 (Key 11). In certain aspects, (i) the chimeric polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 11 (Cage 11), and (ii) the key polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 29 (Key 11).

[0440] In some aspects, the present disclosure provides

(i) the chimeric polypeptide comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 71%, at least about 72%, at least about 73%, at least about 74%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 12 (Cage 12), and

(ii) the key polypeptide comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 71%, at least about 72%, at least about 73%, at least about 74%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 30 (Key 12). In certain aspects, (i) the chimeric polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 12 (Cage 12), and (ii) the key polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 30 (Key 12).

[0441] In some aspects, the present disclosure provides

(i) the chimeric polypeptide comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 71%, at least about 72%, at least about 73%, at least about 74%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 13 (Cage 13), and

(ii) the key polypeptide comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 71%, at least about 72%, at least about 73%, at least about 74%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 31 (Key 13). In certain aspects, (i) the chimeric polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 13 (Cage 13), and (ii) the key polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 31 (Key 13).

[0442] In some aspects, the present disclosure provides

(i) the chimeric polypeptide comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 71%, at least about 72%, at least about 73%, at least about 74%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 14 (Cage 14), and

(ii) the key polypeptide comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 71%, at least about 72%, at least about 73%, at least about 74%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 31 (Key 14). In certain aspects, (i) the chimeric polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 14 (Cage 14), and (ii) the key polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 31 (Key 14).

[0443] In some aspects, the present disclosure provides

(i) the chimeric polypeptide comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 71%, at least about 72%, at least about 73%, at least about 74%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 15 (Cage 15), and

(ii) the key polypeptide comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 71%, at least about 72%, at least about 73%, at least about 74%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 32 (Key 15). In certain aspects, (i) the chimeric polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 15 (Cage 15), and (ii) the key polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 32 (Key 15).

[0444] In some aspects, the present disclosure provides

(i) the chimeric polypeptide comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 71%, at least about 72%, at least about 73%, at least about 74%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 16 (Cage 16), and

(ii) the key polypeptide comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 71%, at least about 72%, at least about 73%, at least about 74%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 33 (Key 16). In certain aspects, (i) the chimeric polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 16 (Cage 16), and (ii) the key polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 33 (Key 16).

[0445] In some aspects, the present disclosure provides

(i) the chimeric polypeptide comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 71%, at least about 72%, at least about 73%, at least about 74%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 17 (Cage 17), and

(ii) the key polypeptide comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 71%, at least about 72%, at least about 73%, at least about 74%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 34 (Key 17). In certain aspects, (i) the chimeric polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 17 (Cage 17), and (ii) the key polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 34 (Key 17).

[0446] In some aspects, the present disclosure provides

(i) the chimeric polypeptide comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 71%, at least about 72%, at least about 73%, at least about 74%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 18 (Cage 18), and

(ii) the key polypeptide comprises an amino acid sequence having at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 71%, at least about 72%, at least about 73%, at least about 74%, at least about 75%, at least about 76%, at least about 77%, at least about 78%, at least about 79%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 35 (Key 18). In certain aspects, (i) the chimeric polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 18 (Cage 18), and (ii) the key polypeptide comprises the amino acid sequence set forth in SEQ ID NO: 35 (Key 18).

IV. Vectors

[0447] In some aspects, the present disclosure provides a vector comprising an isolated nucleic acid molecule that encodes a chimeric polypeptide disclosed herein, a key polypeptide (or a plurality thereof), or a combination thereof. A nucleic acid is “isolated” or “rendered substantially pure” when purified away from other cellular components or other contaminants, e.g, other cellular nucleic acids (e.g, other chromosomal DNA, e.g, the chromosomal DNA that is linked to the isolated DNA in nature) or proteins, by standard techniques, including alkaline/SDS treatment, CsCl banding, column chromatography, restriction enzymes, agarose gel electrophoresis and others well known in the art. See, F. Ausubel, etal ., ed. (1987) Current Protocols in Molecular Biology, Greene Publishing and Wiley Interscience, New York. A nucleic acid described herein can be, for example, DNA or RNA and can or cannot contain intronic sequences. In certain aspects, the nucleic acid is a cDNA molecule. Nucleic acids described herein can be obtained using standard molecular biology techniques known in the art.

[0448] In some aspects, the disclosure provides a vector comprising (a) a polynucleotide encoding a chimeric polypeptide disclosed herein, and (b) a polynucleotide encoding one or more key polypeptides capable of binding to the structural region of the cage polypeptide of the chimeric polypeptide.

[0449] In some aspects, the present disclosure provides a vector comprising (a) one or more polynucleotides encoding a chimeric polypeptide disclosed herein, operatively linked to a first promoter; and (b) one or more polynucleotides encoding one or more key polypeptides capable of binding to the structural region of the cage polypeptide of the chimeric polypeptide, wherein the one or more polynucleotides encoding the one or more key polypeptides are operatively linked to a second promoter.

[0450] In some aspects, multiple open reading frames encoding a key polypeptide are operatively linked to a single promoter (e.g, an inducible promoter). In some aspects, each polynucleotide encoding a key polypeptide is operatively linked to a different promoter, i.e., the expression of each key polypeptide is independently controlled by its own promoter (e.g, an inducible promoter). When multiple inducible promoters are present, they can the induced by the same inducer molecule or a different inducer.

[0451] In some aspects, a nucleic acid molecule encoding a chimeric polypeptide disclosed herein, a key, or a combination thereof can be operably linked to one or more regulatory elements. Regulatory elements could include, e.g, promoters/enhancers (such as exhaustion- responsive promoters, activation-responsive promoters, cytokine-responsive promoters, calcium-responsive promoters, and the like), localization sequences (such as membrane- localization sequences, nuclear localization sequences, nuclear exclusion sequences, proteasomal targeting sequences, and the like), post-translational modification sequences (such as ubiquitination, phosphorylation, dephosphorylation, and the like).

[0452] Suitable vectors for the disclosure include expression vectors, viral vectors, and plasmid vectors. In some aspects, the vector is a viral vector, a mammalian vector, or a bacterial vector. In some aspects, the vector is a viral vector. As used herein, the terms “vector” and “expression vector” refers to any nucleic acid construct which contains the necessary elements for the transcription and translation of an inserted coding sequence, or in the case of an RNA viral vector, the necessary elements for replication and translation, when introduced into an appropriate host cell. Expression vectors can include plasmids, phagemids, viruses, and derivatives thereof.

[0453] One can readily employ any vectors well-known in the art. Certain viral vectors are based on non-cytopathic eukaryotic viruses in which non-essential genes have been replaced with the gene of interest. Non-cytopathic viruses include retroviruses, the life cycle of which involves reverse transcription of genomic viral RNA into DNA with subsequent proviral integration into host cellular DNA.

[0454] In some aspects, the vector is a retroviral vector. As used herein, viral vectors include, but are not limited to, selected from the group consisting of an adenoviral vector, a lentivirus, a Sendai virus vector, a baculoviral vector, an Epstein Barr viral vector, a papovaviral vector, a vaccinia viral vector, a herpes simplex viral vector, a hybrid vector, and an adeno associated virus (AAV) vector. In some specific aspects, the vector is a lentivirus. Examples of lentiviral vectors are disclosed in W09931251, W09712622, W09817815, W09817816, and W098 18934, each which is incorporated herein by reference in its entirety.

[0455] Other vectors include plasmid vectors. Plasmid vectors have been extensively described in the art and are well-known to those of skill in the art. See , e.g ., Sambrook et al ., Molecular Cloning: A Laboratory Manual, Second Edition, Cold Spring Harbor Laboratory Press, 1989. In the last few years, plasmid vectors have been found to be particularly advantageous for delivering genes to cells in vivo because of their inability to replicate within and integrate into a host genome. These plasmids, however, having a promoter compatible with the host cell, can express a peptide from a gene operably encoded within the plasmid. Some commonly used plasmids available from commercial suppliers include pBR322, pUC18, pUC19, various pcDNA plasmids, pRC/CMV, various pCMV plasmids, pSV40, and pBlueScript. Additional examples of specific plasmids include pcDNA3.1, catalog number V79020; pcDNA3.1/hygro, catalog number V87020; pcDNA4/myc-His, catalog number V86320; and pBudCE4.1, catalog number V53220, all from Invitrogen (Carlsbad, CA.). Other plasmids are well-known to those of ordinary skill in the art. Additionally, plasmids can be custom designed using standard molecular biology techniques to remove and/or add specific fragments of DNA.

[0456] In some aspects, the vector comprises a polynucleotide encoding a chimeric polypeptide of the and the second polynucleotide encoding a key polypeptide (or a plurality thereof). Thus, in some aspects, the polynucleotide encoding the chimeric polypeptide and the polypeptide encoding the key polypeptide are on the same vector. In other aspects, the polynucleotide encoding the chimeric polypeptide and the second polynucleotide encoding the key polypeptide are on different vectors.

[0457] A polynucleotide encoding a key polypeptide can be operably linked to a promoter, e.g ., an inducible promoter. Thus, the expression of the key polypeptide can be triggered or modulated by the administration of a ligand that, upon activation of the inducible promoter, results in the expression of the key polypeptide. Inducing expression of the key polypeptide can allow tunable control of the chimeric polypeptide by modulated the population of cage polypeptides that become activated. Tunable control of the cage polypeptide activation therefore allows tunable control of the endocytotic processing of a membrane protein, e.g. , a CAR or TCR, comprising the chimeric polypeptide. In turn, tunable control of endocytotic processing and protein degradation allows tunable control of surface expression levels of the membrane protein, e.g. , a CAR or TCR. Accordingly, the tunable control of the surface expression levels of the membrane protein, e.g. , a CAR or TCR, would allow modulating, preventing, or reverting immune cell exhaustion.

[0458] In some aspects, the polynucleotides disclosed herein are integrated into the genome of a host cell (e.g, a nucleic acid encoding a CAR or TCR comprising a chimeric polypeptide of the present disclosure can be integrated into the genome of an immune cell, e.g, a T-cell).

[0459] In some specific aspects, a polynucleotide of the present disclosure (e.g, a polynucleotide encoding a chimeric polypeptide disclosed herein) is a polynucleotide encoding a CAR as set forth in ROR1 CAR + Cage 16 (SEQ ID NO: 37). In other specific aspects, a polynucleotide of the present disclosure (e.g, a polynucleotide encoding a chimeric polypeptide disclosed herein) is a polynucleotide encoding a CAR as set forth in ROR1 + Cage 11 (SEQ ID NO: 39).

[0460] In some aspects, the polynucleotides disclosed herein are DNA ( e.g . , a DNA molecule or a combination thereof), RNA (e.g., a RNA molecule or a combination thereof), or any combination thereof. The polynucleotides disclosed herein comprise nucleic acid sequences comprising single stranded or double stranded RNA or DNA in genomic or cDNA form, or DNA-RNA hybrids, each of which may include chemically or biochemically modified, non natural, or derivatized nucleotide bases. Such nucleic acid sequences may comprise additional sequences useful for promoting expression and/or purification of the encoded polypeptide, including but not limited to polyA sequences, modified Kozak sequences, and sequences encoding epitope tags, export signals, and secretory signals, nuclear localization signals, and plasma membrane localization signals. It will be apparent to those of skill in the art, based on the teachings herein, what nucleic acid sequences will encode the polypeptides of the disclosure. The disclosure further provides expression vectors comprising the polynucleotides of the disclosure operatively linked to a promoter, e.g, an inducible promoter. The disclosure further provides cells comprising the expression vectors comprising polynucleotides of the present disclosure operatively linked to a promoter.

[0461] The vectors disclosed herein can comprises a nucleic acid coding region (e.g, a nucleic acid encoding a chimeric polypeptide disclosed herein, a nucleic acid encoding a CAR or TCR comprising a chimeric polypeptide disclosed herein, a nucleic acid encoding a key polypeptide, or any combination thereof) operatively linked to any control sequences capable of effecting expression of the gene product (e.g, a chimeric polypeptide, a protein comprising a chimeric polypeptide, a CAR or TCR comprising a chimeric polypeptide, a key polypeptide, or a combination thereof). “Control sequences” operably linked to the nucleic acid sequences of the disclosure (e.g, a nucleic acid encoding a chimeric polypeptide disclosed herein, a nucleic acid encoding a CAR or TCR comprising a chimeric polypeptide disclosed herein, a nucleic acid encoding a key polypeptide, or any combination thereof) are nucleic acid sequences capable of effecting the expression of the nucleic acid molecules. The control sequences need not be contiguous with the nucleic acid sequences of the disclosure, so long as they function to direct the expression thereof. Thus, for example, intervening untranslated yet transcribed sequences can be present between a promoter sequence and the nucleic acid sequences and the promoter sequence can still be considered “operably linked” to the coding sequence. Other such control sequences include, but are not limited to, polyadenylation signals, termination signals, and ribosome binding sites. The control sequence used to drive expression of the disclosed nucleic acid sequences in a mammalian system may be constitutive (driven by any of a variety of promoters, including but not limited to, CMV, SV40, RSV, actin, EF) or inducible (driven by any of a number of inducible promoters including, but not limited to, tetracycline, ecdysone, steroid-responsive). The expression vector must be replicable in the host organisms either as an episome or by integration into host chromosomal DNA. In various aspects, the expression vector may comprise a plasmid, viral-based vector, or any other suitable expression vector as discussed above

V Nucleic acid Modifications

[0462] The polynucleotides of the present disclosure ( e.g ., a polynucleotide encoding a chimeric polypeptide disclosed herein) can comprise nucleic acids with one or more modifications. Accordingly, in some aspects, a polynucleotide sequence disclosed herein can comprise at least one nucleotide analogue. In some aspects, at least one nucleotide analogue introduced by using in vitro translation (IVT) or chemical synthesis is selected from the group consisting of a 2’-0-rnethoxyethyl-RNA (2’-MOE-RNA) monomer, a 2’-fluoro-DNA monomer, a 2’-0-alkyl-RNA monomer, a 2’-amino-DNA monomer, a locked nucleic acid (LNA) monomer, a cEt monomer, a cMOE monomer, a 5’-Me-LNA monomer, a 2’-(3- hydroxy)propyl-RNA monomer, an arabino nucleic acid (ANA) monomer, a 2’-fluoro-ANA monomer, an anhydrohexitol nucleic acid (HNA) monomer, an intercalating nucleic acid (INA) monomer, and a combination of two or more of said nucleotide analogues. In some aspects, the modified nucleic acid molecule comprises at least one backbone modification, for example, a phosphorothioate intemucleotide linkage.

[0463] In some aspects, nucleic acids disclosed herein can be chemically modified at terminal locations, for example by introducing M (2'-0-methyl), MS (2'-0-methyl 3' phosphorothioate), or MSP (2'-0-methyl 3’thioPACE, phosphonoacetate) modifications, or combinations thereof at positions 1, 2, 3 respect to the 5’ and/or 3’ termini.

[0464] In some aspects, the nucleic acids provided herein are synthetic, e.g., modified DNA molecules encoding RNA (e.g, an mRNA encoding a CAR or a TCR) and/or modified RNA encoding polypeptides (e.g, encoding a polypeptide key), where the synthetic, modified DNA or RNA molecules comprise one or more modifications. [0465] The modified ( e.g ., synthetic) polynucleotides disclosed herein, e.g., a nucleic acid encoding a chimeric polypeptide of the present disclosure, or a polynucleotide or set of polynucleotides encoding a CAR or a TCR, include modifications to prevent rapid degradation by endo- and exo-nucleases.

[0466] Modifications include, but are not limited to, for example, (a) end modifications, e.g, 5’ end modifications (phosphorylation dephosphorylation, conjugation, inverted linkages, etc.), 3’ end modifications (conjugation, DNA nucleotides, inverted linkages, etc.), (b) base modifications, e.g, replacement with modified bases, stabilizing bases, destabilizing bases, or bases that base pair with an expanded repertoire of partners, or conjugated bases, (c) sugar modifications (e.g, at the T position or 4’ position) or replacement of the sugar, as well as (d) internucleoside linkage modifications, including modification or replacement of the phosphodiester linkages.

[0467] Specific examples of modified (e.g, synthetic) polynucleotides disclosed herein, e.g, a nucleic acid encoding a chimeric polypeptide of the present disclosure, or a polynucleotide or set of polynucleotides encoding a CAR or a TCR, useful with the methods described herein include, are not limited to, modified nucleic acids containing modified or non-natural internucleoside linkages.

[0468] Modified (e.g, synthetic) polynucleotides disclosed herein, e.g, a nucleic acid encoding a chimeric polypeptide of the present disclosure, or a polynucleotide or set of polynucleotides encoding a CAR or a TCR, having modified intemucleoside linkages include, among others, those that do not have a phosphorus atom in the intemucleoside linkage.

[0469] In other aspect, a modified (e.g, synthetic) polynucleotide disclosed herein, e.g, a nucleic acid encoding a chimeric polypeptide of the present disclosure, or a polynucleotide or set of polynucleotides encoding a CAR or a TCR, has a phosphorus atom in its intemucleoside linkage(s).

[0470] Non-limiting examples of modified intemucleoside linkages include phosphorothioates, chiral phosphorothioates, phosphorodithioates, phosphotriesters, aminoalkylphosphotriesters, methyl and other alkyl phosphonates including 3’-alkylene phosphonates and chiral phosphonates, phosphinates, phosphoramidates including 3’ -amino phosphoramidate and aminoalkylphosphoramidates, thionophosphoramidates, thionoalkylphosphonates, thionoalkylphosphotriesters, and boranophosphates having normal 3’ -5’ linkages, T-5’ linked analogs of these, and those) having inverted polarity wherein the adjacent pairs of nucleoside units are linked 3’-5’ to 5’-3’ or T-5’ to 5’-T. Various salts, mixed salts and free acid forms are also included.

[0471] As non-limiting examples, modified (e.g, synthetic) polynucleotides disclosed herein, e.g, a nucleic acid encoding a chimeric polypeptide of the present disclosure, or a polynucleotide or set of polynucleotides encoding a CAR or a TCR, can include at least one modified nucleoside including a T -O-methyl modified nucleoside, a nucleoside comprising a 5’ phosphorothioate group, a 2’-amino- modified nucleoside, 2’ -alkyl-modified nucleoside, morpholino nucleoside, a phosphoramidate or a non-natural base comprising nucleoside, or any combination thereof.

[0472] Standard methods can be applied to synthesize an isolated polynucleotide sequence encoding an isolated polypeptide of interest. For example, a single DNA or RNA oligomer containing a codon-optimized nucleotide sequence coding for the particular isolated polypeptide can be synthesized. In other aspects, several small oligonucleotides coding for portions of the desired polypeptide can be synthesized and then ligated. In some aspects, the individual oligonucleotides typically contain 5’ or 3’ overhangs for complementary assembly.

[0473] A polynucleotide disclosed herein (e.g, a polynucleotide encoding a chimeric polypeptide, a polynucleotide encoding a key, or a polynucleotide or set of polynucleotides encoding a CAR or a TCR disclosed herein) can be chemically synthesized using chemical synthesis methods and potential nucleobase substitutions known in the art. See, for example, International Publication Nos. WO2014093924, WO2013052523; WO2013039857,

WO2012135805, WO2013151671; U.S. Publ. No. US20130115272; or U.S. Pat. Nos. US8999380, US8710200, all of which are herein incorporated by reference in their entireties.

VI. Cells and Methods of Making Engineered Cells

[0474] The present disclosure provides methods of generating or preparing cells expressing a chimeric polypeptide disclosed herein. The present disclosure provides methods of making an engineered cell, e.g, an engineered immune cell, comprising transfecting (i) a polynucleotide encoding a chimeric polypeptide disclosed herein, (ii) a polynucleotide encoding a chimeric polypeptide disclosed herein and a corresponding key polypeptide, (iii) a polynucleotide set comprising a first polynucleotide encoding a chimeric polypeptide and a second polynucleotide encoding a corresponding key polypeptide, (iv) a polynucleotide encoding a CAR or a TCR comprising a chimeric polypeptide disclosed herein, or (v) a vector or set of vectors comprising (i), (ii), (iii) or (iv), in a cell, e.g ., an immune cell.

[0475] The expression of a chimeric polypeptide of the present disclosure as part of a CAR or a TCR can modulate the levels of CAR or TCR in response to activation of the chimeric polypeptide by a key polypeptide. In some aspects, the chimeric polypeptide (e.g, as part of a CAR or a TCR) is expressed in the cell following transfection. In some aspects, the transfected cell can be administered to a subject in need thereof. In some aspect, the administration of the transfected cell to the subject can be followed by the administration of a key polypeptide (or a plurality thereof), or the administration of an inducer capable of inducing the endogenous expression of a key polypeptide (or a plurality thereof).

[0476] The present disclosure also provides cells prepared as disclosed above. Accordingly, the present disclosure provides cells comprising a polynucleotide disclosed herein, a vector disclosed herein, or a chimeric polypeptide disclosed herein.

[0477] The present disclosure also provides a cell genetically modified to express a CAR or a TCR, wherein the cell comprises a polynucleotide disclosed herein, a vector disclosed herein, or a chimeric polypeptide disclosed herein. In some aspects, the cell is a T cell, a natural killer (NK) cell, an natural killer T (NKT) cell, or an ILC cell.

[0478] In some aspects, the disclosure provides a cell comprising (a) a polynucleotide encoding a chimeric polypeptide disclosed herein, and (b) a polynucleotide encoding one or more key polypeptides capable of binding to the structural region of the cage polypeptide of the chimeric polypeptide.

[0479] In some aspects, the present disclosure provides cells (e.g, recombinant host cells or immune cells) comprising (a) one or more polynucleotides encoding a chimeric polypeptide disclosed herein, operatively linked to a first promoter; and (b) one or more polynucleotides encoding one or more key polypeptides capable of binding to the structural region of the cage polypeptide of the chimeric polypeptide, wherein the one or more polynucleotides encoding the one or more key polypeptides are operatively linked to a second promoter.

[0480] In some aspects, the present disclosure provides cells (e.g, recombinant host cells or immune cells) that comprise the expression vectors disclosed herein, wherein cells host cells can be either prokaryotic or eukaryotic. The cells can be transiently or stably engineered to incorporate the expression vector of the disclosure, using techniques including but not limited to bacterial transformations, calcium phosphate co-precipitation, electroporation, or liposome mediated-, DEAE dextran mediated-, polycationic mediated-, or viral mediated transfection.

[0481] A method of producing a chimeric polypeptide disclosed herein using cells disclosed herein is an additional part of the disclosure. In one aspect, the method comprises the steps of (a) culturing a cell ( e.g ., a host cell) under conditions conducive to the expression of the polypeptide (e.g., a CAR or TCR comprising chimeric polypeptide of the present disclosure, a key polypeptide, or a combination thereof), and (b) optionally, recovering the expressed polypeptide or polypeptides. The expressed polypeptide or polypeptides can be recovered from the cell free extract or recovered from the culture medium. In another aspect, the method comprises chemically synthesizing the polypeptides, e.g, using solid phase peptide synthesis

VII. Methods of Reducing Exhaustion/Dysfunction

[0482] The present disclosure also provides methods of reducing, ameliorating, or inhibiting exhaustion or dysfunction of a cell (e.g, an immune cell) comprising modifying the cell to express a CAR or a TCR comprising a chimeric polypeptide that can modulate the levels of CAR or TCR in response to activation of the chimeric polypeptide by a key polypeptide.

[0483] One of the various ways that tumor cells can evade a host immune response is by causing tumor-specific immune cells, e.g, T cells, to become exhausted. As used herein, the term “exhaustion,” or more specifically, “T cell exhaustion,” refers to the loss of T cell function, which can occur as a result of an infection or a disease (e.g, cancer). T cell exhaustion can be used interchangeably with “T cell dysfunction” or “T cell anergy” in the present disclosure. In some aspects, T cell exhaustion is associated with increased expression of various immune checkpoint inhibitory molecules (e.g, PD-1, TIM-3, and LAG-3), apoptosis, and reduced effector function (e.g, cytokine production and expression of cytotoxic molecules, such as perforin and granzymes). Accordingly, the terms “reduce T cell exhaustion,” “ameliorate T cell exhaustion,” “inhibit T cell exhaustion,” and the like, refers to a condition of restored functionality of T cells characterized by one or more of the following: (i) decreased expression of one or more immune checkpoint inhibitory molecules (e.g, PD-1, TIM-3, and LAG-3), (ii) increased memory formation and/or maintenance of memory markers (e.g, CD45RO, CD62L, and/or CCR7), (iii) prevention of apoptosis, (iv) increased cytokine production (e.g, IL-2, IFN-g, and/or TNF-a), (v) enhanced killing capacity, (vi) increased recognition of tumor targets with low surface antigen, (vii) enhanced proliferation in response to antigen, and (viii) any combination thereof.

[0484] In some aspects, modifying a CAR or a TCR by incorporating a chimeric polypeptide disclosed herein results in a cell, e.g., T cell, with increased resistance or tolerance to exhaustion. Accordingly, in certain aspects, the present disclosure relates to methods of reducing exhaustion in an immune cell, e.g, T cell (e.g, tumor-specific T cell) by modifying a CAR or TCR by incorporating a chimeric polypeptide disclosed herein. In certain aspects, reducing immune cell, e.g, T cell, exhaustion comprises reversing the dysfunction that has already occurred in the immune cell, e.g, T cell, (i.e., making exhausted T cells become less exhausted). In further aspects, reducing immune cell, e.g, T cell, exhaustion comprises preventing a newly activated immune cell, e.g, T cell, from becoming exhausted.

[0485] In some aspects, reducing immune cell, e.g, T cell, exhaustion comprises both reversing and preventing exhaustion in an immune cell, e.g, a T cell.

[0486] The exhaustion state of an immune cell, e.g, a T cell, can be determined by various methods known in the art. In some aspects, the exhaustion state of an immune cell, e.g, a T cell, can be measured by evaluating the resistance of the immune cell, e.g, a T cell, to apoptosis. In certain aspects, increased resistance to apoptosis can promote the long-term persistence or survival of the T cell.

[0487] In some aspects, the exhaustion state of an immune cell, e.g, a T cell, can be measured by evaluating the resistance of the immune cell, e.g, a T cell, to immune checkpoint molecules. Examples of immune checkpoint molecules are known in the art and include, but are not limited to, PD-1, TIM-3, LAG-3, BTLA, SIGLEC7, CD200R, TIGIT, VISTA, and any combination thereof.

[0488] In some aspects, the exhaustion state of an immune cell, e.g, a T cell, can be measured by evaluating the ability of the immune cell, e.g, a T cell, to produce cytokines upon stimulation, e.g, T-cell receptor (TCR) stimulation. Non-limiting examples of cytokines include IFN-g, IL-2, TNF-a, GM-CSF, IL-6, IL-10, IL-4, IL-5, IL-8, IL-9, IL-13, IL-17, IL- 22, CCL2, CCL3, and any combination thereof.

[0489] In some aspects, the exhaustion state of an immune cell, e.g, a T cell, can be measured by evaluating the ability of the immune cell, e.g, a T cell, to kill tumor cells after repeated tumor challenge. In certain aspects, killing tumor cells comprises preventing the outgrowth of tumor cells.

VIII. Pharmaceutical Compositions

[0490] The present disclosure also provides a composition comprising a polynucleotide encoding a chimeric polypeptide, a polynucleotide encoding a CAR or TCR comprising a chimeric polypeptide, a vector comprising a polynucleotide encoding a chimeric polypeptide, a vector comprising a polynucleotide encoding a CAR or TCR comprising a chimeric polypeptide, a polynucleotide encoding a key polypeptide, a vector comprising a polynucleotide encoding a key polypeptide, or a cell expressing a polypeptide comprising a chimeric polypeptide disclosed herein ( e.g ., a cell expressing a CAR or TCR comprising a chimeric polypeptide of the present disclosure). In some aspects, the composition is used for treating a subject in need of a CAR therapy.

[0491] In some aspects, the composition is a pharmaceutical composition. Accordingly, the present disclosure provides, e.g., pharmaceutical compositions comprising (i) a cell which has been modified to express a chimeric polypeptide disclosed herein, (ii) a key disclosed herein, or (iii) a combination thereof, and a pharmaceutically acceptable carrier, excipient, or stabilizer. As described herein, such pharmaceutical compositions can be used to prevent and/or treat a cancer. In some aspects, an immune cell of the present disclosure (i.e., a cell expressing a CAR or TCR comprising a chimeric polypeptide disclosed herein), present in a pharmaceutical composition disclosed herein is a T cell (e.g, a CAR or TCR-expressing T cell) or an NK cells (e.g, a CAR or TCR-expressing NK cell).

[0492] As used herein, the term “pharmaceutical composition” refers to one or more of the compounds described herein, such as, e.g, a CAR of the present disclosure (e.g, a polynucleotide encoding the CAR, a vector comprising a polynucleotide encoding the CAR, or a CAR polypeptide) or a cell expressing a CAR of the present disclosure, mixed or intermingled with, or suspended in one or more other chemical components, such as pharmaceutically-acceptable carriers and excipients. One purpose of a pharmaceutical composition is to facilitate administration of preparations of, e.g, cell expressing a CAR of the present disclosure to a subject. [0493] The terms “excipient” and “carrier” are used interchangeably and refer to an inert substance added to a pharmaceutical composition to further facilitate administration of a compound, e.g. , a CAR of the present disclosure.

[0494] The terms “pharmaceutically-acceptable carrier,” “pharmaceutically-acceptable excipient,” and grammatical variations thereof, encompass any of the agents approved by a regulatory agency of the U.S. Federal government or listed in the U.S. Pharmacopeia for use in animals, including humans, as well as any carrier or diluent that does not cause the production of undesirable physiological effects to a degree that prohibits administration of the composition to a subject and does not abrogate the biological activity and properties of the administered compound. Included are excipients and carriers that are useful in preparing a pharmaceutical composition and are generally safe, non-toxic, and desirable.

[0495] Acceptable carriers, excipients, or stabilizers are nontoxic to recipients at the dosages and concentrations employed, and include buffers such as phosphate, citrate, and other organic acids; antioxidants including ascorbic acid and methionine; preservatives (such as octadecyldimethylbenzyl ammonium chloride; hexamethonium chloride; benzalkonium chloride, benzethonium chloride; phenol, butyl or benzyl alcohol; alkyl parabens such as methyl or propyl paraben; catechol; resorcinol; cyclohexanol; 3-pentanol; and m-cresol); low molecular weight (less than about 10 residues) polypeptides; proteins, such as serum albumin, gelatin, or immunoglobulins; hydrophilic polymers such as polyvinylpyrrolidone; amino acids such as glycine, glutamine, asparagine, histidine, arginine, or lysine; monosaccharides, disaccharides, and other carbohydrates including glucose, mannose, or dextrins; chelating agents such as EDTA; sugars such as sucrose, mannitol, trehalose or sorbitol; salt-forming counter-ions such as sodium; metal complexes (e.g., Zn-protein complexes); and/or non-ionic surfactants such as TWEEN^®, PLURONICS^® or polyethylene glycol (PEG).

[0496] A pharmaceutical composition can be formulated for any route of administration to a subject. Specific examples of routes of administration include intramuscularly, subcutaneously, ophthalmic, intravenously, intraperitoneally, intradermally, intraorbitally, intracerebrally, intracranially, intraspinally, intraventricular, intrathecally, intracistemally, intracapsularly, or intratum orally. Parenteral administration, characterized by either subcutaneous, intramuscular or intravenous injection, is also contemplated herein. Injectables can be prepared in conventional forms, either as liquid solutions or suspensions, solid forms suitable for solution or suspension in liquid prior to injection, or as emulsions. The injectables, solutions and emulsions also contain one or more excipients. Suitable excipients are, for example, water, saline, dextrose, glycerol or ethanol. In addition, if desired, the pharmaceutical compositions to be administered can also contain minor amounts of non-toxic auxiliary substances such as wetting or emulsifying agents, pH buffering agents, stabilizers, solubility enhancers, and other such agents, such as for example, sodium acetate, sorbitan monolaurate, triethanolamine oleate and cyclodextrins.

[0497] Pharmaceutically acceptable carriers used in parenteral preparations include aqueous vehicles, nonaqueous vehicles, antimicrobial agents, isotonic agents, buffers, antioxidants, local anesthetics, suspending and dispersing agents, emulsifying agents, sequestering or chelating agents and other pharmaceutically acceptable substances. Examples of aqueous vehicles include Sodium Chloride Injection, Ringers Injection, Isotonic Dextrose Injection, Sterile Water Injection, Dextrose and Lactated Ringers Injection. Nonaqueous parenteral vehicles include fixed oils of vegetable origin, cottonseed oil, corn oil, sesame oil and peanut oil. Antimicrobial agents in bacteriostatic or fungistatic concentrations can be added to parenteral preparations packaged in multiple-dose containers which include phenols or cresols, mercurials, benzyl alcohol, chlorobutanol, methyl and propyl p-hydroxybenzoic acid esters, thimerosal, benzalkonium chloride and benzethonium chloride. Isotonic agents include sodium chloride and dextrose. Buffers include phosphate and citrate. Antioxidants include sodium bisulfate. Local anesthetics include procaine hydrochloride. Suspending and dispersing agents include sodium carboxymethylcelluose, hydroxypropyl methylcellulose and polyvinylpyrrolidone. Emulsifying agents include Polysorbate 80 (TWEEN^® 80). A sequestering or chelating agent of metal ions includes EDTA. Pharmaceutical carriers also include ethyl alcohol, polyethylene glycol and propylene glycol for water miscible vehicles; and sodium hydroxide, hydrochloric acid, citric acid or lactic acid for pH adjustment.

[0498] Preparations for parenteral administration include sterile solutions ready for inj ection, sterile dry soluble products, such as lyophilized powders, ready to be combined with a solvent just prior to use, including hypodermic tablets, sterile suspensions ready for injection, sterile dry insoluble products ready to be combined with a vehicle just prior to use and sterile emulsions. The solutions can be either aqueous or nonaqueous.

[0499] If administered intravenously, suitable carriers include physiological saline or phosphate buffered saline (PBS), and solutions containing thickening and solubilizing agents, such as glucose, polyethylene glycol, and polypropylene glycol and mixtures thereof. [0500] Pharmaceutical compositions provided herein can also be formulated to be targeted to a particular tissue, receptor, or other area of the body of the subject to be treated. Many such targeting methods are well known to those of skill in the art. All such targeting methods are contemplated herein for use in the instant compositions. For non-limiting examples of targeting methods, see, e.g, U S. Patent Nos. 6,316,652, 6,274,552, 6,271,359, 6,253,872, 6,139,865,

6,131,570, 6,120,751, 6,071,495, 6,060,082, 6,048,736, 6,039,975, 6,004,534, 5,985,307, 5,972,366, 5,900,252, 5,840,674, 5,759,542 and 5,709,874, each of which is herein incorporated by reference in its entirety.

[0501] The compositions to be used for in vivo administration can be sterile. This is readily accomplished by filtration through, e.g ., sterile filtration membranes.

[0502] The present disclosure also provides a cell composition comprising a nucleic acid encoding a chimeric polypeptide disclosed herein. In some aspects, the present disclosure provides a cell composition comprising a means for reducing, ameliorating, or inhibiting exhaustion and/or dysfunction in a population of immune cells, e.g, immune cells expressing a CAR or a TCR. In some aspects, the means comprises modifying a nucleic acid encoding a CAR or a TCR by inserting a sequence encoding a chimeric polypeptide disclosed herein in the CAR or TCR encoding sequence, wherein the nucleic acid expresses a CAR or TCR comprising the chimeric polypeptide. In some aspects, the means comprises modifying a CAR or a TCR as described above in the population of immune cells.

IX Methods of Treatment

[0503] Provided herein are methods for treating a cancer, e.g. , a tumor, in a subject in need thereof, comprising administering to the subject an effective amount of a cell composition of the disclosure, e.g, a cell expressing a chimeric polypeptide disclosed herein. In some aspects, the method for treating cancer further comprises administering a key polypeptide. In some aspects, the method for treating cancer further comprises administering an inducer of a key polypeptide (e.g, a compound or physicochemical change than induces endogenous expression of the key polypeptide).

[0504] The incorporation of a chimeric polypeptide disclosed herein into a CAR or TCR allows the modulation of the function of the CAR or TCR. The cage portion of the sequesters a degron until a key is provided (e.g, an inducible key endogenously expressed in the cell or a polypeptide key administered to the cell). The key activates the cage polypeptide, releasing the degron, and the degron targets the cage and any functional peptide fused to it (i.e., the CAR or TCR) for degradation. Accordingly, the present disclosure provides a method of controlling a T-cell mediated immune response in a subject in need thereof comprising administering an effective amount of a cell comprising a chimeric polypeptide disclosed herein ( e.g ., as part of a CAR or TCR) to the subject.

[0505] The present disclosure also provides a method of stimulating a T cell-mediated immune response to a target cell population or tissue in a subject, comprising administering an effective amount of a cell composition of the disclosure, e.g., a cell expressing a chimeric polypeptide disclosed herein to the subject. In some aspects, the method of stimulating a T cell- mediated immune response further comprises administering a key polypeptide. In some aspects, the method of stimulating a T cell-mediated immune response further comprises administering an inducer of a key polypeptide (e.g, a compound or physicochemical change than induces endogenous expression of the key polypeptide).

[0506] The present disclosure also provides a method of providing an anti-tumor immunity in a subject in need thereof, the method comprising administering a cell composition of the disclosure, e.g, a cell expressing a chimeric polypeptide disclosed herein, to the subject. In some aspects, the method of providing an anti-tumor immunity further comprises administering a key polypeptide. In some aspects, the method of providing an anti-tumor immunity further comprises administering an inducer of a key polypeptide (e.g, a compound or physicochemical change than induces endogenous expression of the key polypeptide).

[0507] In some aspects, the cell administered in the cell composition of the disclosure (e.g, a cell expressing a CAR comprising a chimeric polypeptide disclosed herein) is a T cell. In some aspects, the cell is an autologous T cell.

[0508] In some aspects, administering the cell composition of the disclosure (e.g. , an immune cell such as a T cell expressing a CAR comprising a chimeric polypeptide disclosed herein) reduces a tumor volume in the subject compared to a reference tumor volume. In some aspects, the reference tumor volume is the tumor volume in the subject prior to the administration of the modified cell. In further aspects, the reference tumor volume is the tumor volume in a corresponding subject that did not receive the administration. In some aspects, the tumor volume in the subject is reduced by at least about 5%, at least about 10%, at least about 15%, at least about 30%, at least about 40%, at least about 50%, at least about 60%, at least about 70%, at least about 80%, at least about 90%, or at least about 100% after the administration compared to the reference tumor volume.

[0509] In some aspects, treating a tumor comprises reducing a tumor weight in the subject. In certain aspects, administering the cell composition of the disclosure ( e.g ., an immune cell such as a T cell expressing a CAR comprising a chimeric polypeptide disclosed herein) can reduce the tumor weight in a subject when administered to the subject. In some aspects, the tumor weight is reduced by at least about 5%, at least about 10%, at least about 15%, at least about 30%, at least about 40%, at least about 50%, at least about 60%, at least about 70%, at least about 80%, at least about 90%, or at least about 100% after the administration compared to a reference tumor weight. In some aspects, the reference tumor weight is the tumor weight in the subject prior to the administration of the cell composition of the disclosure. In further aspects, the reference tumor weight is the tumor weight in a corresponding subject that did not receive the administration.

[0510] In some aspects, administering the cell composition of the disclosure (e.g., an immune cell such as a T cell expressing a CAR comprising a chimeric polypeptide disclosed herein) to a subj ect, e.g. , suffering from a tumor, can increase the number and/or percentage of TILs (e.g. , CD4⁺ or CD8⁺) in a tumor and/or TME of the subject. In certain aspects, the number and/or percentage of TILs in a tumor and/or TME is increased by at least about 5%, at least about 10%, at least about 15%, at least about 20%, at least about 25%, at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 100%, at least about 110%, at least about 120%, at least about 130%, at least about 140%, at least about 150%, at least about 160%, at least about 170%, at least about 180%, at least about 190%, at least about 200%, at least about 210%, at least 220%, at least about 230%, at least about 240%, at least about 250%, at least about 260%, at least about 270%, at least about 280%, at least about 290%, or at least about 300% or more compared to a reference (e.g, corresponding value in a subject that did not receive the cell composition of the present disclosure or the same subject prior to the administration of the cell composition of the present disclosure).

[0511] In addition to the above, administering the cell composition of the disclosure (e.g. , an immune cell such as a T cell expressing a CAR comprising a chimeric polypeptide disclosed herein) can have other effects which are conducive for the treatment of a tumor. [0512] As described herein, the cell composition of the disclosure ( e.g ., a cell expressing a CAR or TCR comprising a chimeric polypeptide of the present disclosure) can be used to treat variety of cancer types, e.g., a tumor derived from a cancer comprising a breast cancer, head and neck cancer, uterine cancer, brain cancer, skin cancer, renal cancer, lung cancer, colorectal cancer, prostate cancer, liver cancer, bladder cancer, kidney cancer, pancreatic cancer, thyroid cancer, esophageal cancer, eye cancer, stomach (gastric) cancer, gastrointestinal cancer, ovarian cancer, carcinoma, sarcoma, leukemia, lymphoma, myeloma, or a combination thereof.

[0513] In some aspects, the cell composition of the disclosure (e.g, an immune cell such as a T cell expressing a CAR comprising a chimeric polypeptide disclosed herein) can be used in combination with other therapeutic agents (e.g, anti-cancer agents and/or immunomodulating agents). Accordingly, in certain aspects, a method of treating a tumor disclosed herein comprises administering the cell composition of the disclosure in combination with one or more additional therapeutic agents. In some aspects, the cell composition of the disclosure (e.g, an immune cell such as a T cell expressing a CAR comprising a chimeric polypeptide disclosed herein) can be used in combination with one or more anti-cancer agents, such that multiple elements of the immune pathway can be targeted. In some aspects, an anti-cancer agent comprises an immune checkpoint inhibitor (i.e., blocks signaling through the particular immune checkpoint pathway). Non-limiting examples of immune checkpoint inhibitors that can be used in the present methods comprise a CTLA-4 antagonist (e.g, anti-CTLA-4 antibody), PD-1 antagonist (e.g., anti -PD- 1 antibody, anti-PD-Ll antibody), TIM-3 antagonist (e.g, anti-TIM-3 antibody), or combinations thereof. A comprehensive and non-limiting list of combination treatment is disclosed in detail in the Combination Treatments section of this application.

[0514] In some aspects, the cell composition of the disclosure (e.g, an immune cell such as a T cell expressing a CAR comprising a chimeric polypeptide disclosed herein) is administered to the subject prior to or after the administration of the additional therapeutic agent. In other aspects, the cell composition of the disclosure is administered to the subject concurrently with the additional therapeutic agent. In certain aspects, the cell composition of the disclosure (e.g, an immune cell such as a T cell expressing a CAR comprising a chimeric polypeptide disclosed herein) and the additional therapeutic agent can be administered concurrently as a single composition in a pharmaceutically acceptable carrier. In other aspects, the cell composition of the disclosure (e.g, an immune cell such as a T cell expressing a CAR comprising a chimeric polypeptide disclosed herein) and the additional therapeutic agent are administered concurrently as separate compositions.

[0515] In some aspects, a subject that can be treated with the composition and methods of the present disclosure is a nonhuman animal such as a rat or a mouse. In some aspects, the subject that can be treated is a human.

[0516] In some aspects, an immune cell disclosed herein ( e.g ., a cell expressing a CAR or TCR comprising a chimeric polypeptide of the present disclosure) can be used in combination with other therapeutic agents (e.g., anti-cancer agents and/or immunomodulating agents). Accordingly, in certain aspects, a method of treating a tumor disclosed herein comprises administering an immune cell of the present disclosure (e.g, a cell expressing a CAR or TCR comprising a chimeric polypeptide of the present disclosure) in combination with one or more additional therapeutic agents to a subject. Such agents can include, for example, chemotherapeutic drug, targeted anti-cancer therapy, oncolytic drug, cytotoxic agent, immune- based therapy, cytokine, surgical procedure, radiation procedure, activator of a costimulatory molecule, immune checkpoint inhibitor, a vaccine, a cellular immunotherapy, or any combination thereof.

[0517] In some aspects, an immune cell disclosed herein (e.g, a cell expressing a CAR or TCR comprising a chimeric polypeptide of the present disclosure) can be used in combination with a standard of care treatment (e.g, surgery, radiation, and chemotherapy). Methods described herein can also be used as a maintenance therapy, e.g, a therapy that is intended to prevent the occurrence or recurrence of tumors.

[0518] In some aspects, an immune cell of the present disclosure (e.g, a cell expressing a CAR or TCR comprising a chimeric polypeptide of the present disclosure) can be used in combination with one or more anti-cancer agents, such that multiple elements of the immune pathway can be targeted. Non-limiting of such combinations include: a therapy that enhances tumor antigen presentation (e.g, dendritic cell vaccine, GM-CSF secreting cellular vaccines, CpG oligonucleotides, imiquimod); a therapy that inhibits negative immune regulation e.g, by inhibiting CTLA-4 and/or PD1/PD-L1/PD-L2 pathway and/or depleting or blocking Tregs or other immune suppressing cells (e.g, myeloid-derived suppressor cells); a therapy that stimulates positive immune regulation, e.g, with agonists that stimulate the CD-137, OX-40, and/or CD40 or GITR pathway and/or stimulate T cell effector function; a therapy that increases systemically the frequency of anti-tumor T cells; a therapy that depletes or inhibits Tregs, such as Tregs in the tumor, e.g., using an antagonist of CD25 (e.g, daclizumab) or by ex vivo anti-CD25 bead depletion; a therapy that impacts the function of suppressor myeloid cells in the tumor; a therapy that enhances immunogenicity of tumor cells (e.g, anthracyclines); adoptive T cell or NK cell transfer including genetically modified cells, e.g, cells modified by chimeric antigen receptors (CAR-T therapy); a therapy that inhibits a metabolic enzyme such as indoleamine dioxigenase (IDO), dioxigenase, arginase, or nitric oxide synthetase; a therapy that reverses/prevents T cell anergy or exhaustion; a therapy that triggers an innate immune activation and/or inflammation at a tumor site; administration of immune stimulatory cytokines; blocking of immuno repressive cytokines; or any combination thereof.

[0519] In some aspects, an anti-cancer agent comprises an immune checkpoint inhibitor (i.e., blocks signaling through the particular immune checkpoint pathway). Non-limiting examples of immune checkpoint inhibitors that can be used in the present methods comprise a CTLA-4 antagonist (e.g, anti-CTLA-4 antibody), PD-1 antagonist (e.g, anti -PD- 1 antibody, anti-PD- L1 antibody), TIM-3 antagonist (e.g, anti-TIM-3 antibody), or combinations thereof. Non limiting examples of such immune checkpoint inhibitors include the following: anti -PD 1 antibody (e.g., nivolumab (OPDIVO^®), pembrolizumab (KEYTRUDA^®; MK-3475), pidilizumab (CT-011), PDR001, MEDI0680 (AMP-514), TSR-042, REGN2810, JS001, AMP- 224 (GSK-2661380), PF-06801591, BGB-A317, BI 754091, SHR-1210, and combinations thereof); anti-PD-Ll antibody (e.g, atezolizumab (TECENTRIQ^®; RG7446; MPDL3280A; R05541267), durvalumab (MEDI4736, IMFINZI^®), BMS-936559, avelumab (BAVENCIO^®), LY3300054, CX-072 (Proclaim-CX-072), FAZ053, KN035, MDX-1105, and combinations thereof); and anti-CTLA-4 antibody (e.g, ipilimumab (YERVOY^®), tremelimumab (ticilimumab; CP-675,206), AGEN-1884, ATOR-1015, and combinations thereof).

[0520] In some aspects, an anti-cancer agent comprises an immune checkpoint activator (i.e., promotes signaling through the particular immune checkpoint pathway). In certain aspects, immune checkpoint activator comprises 0X40 agonist (e.g, anti-OX40 antibody), LAG-3 agonist (e.g. anti-LAG-3 antibody), 4-1BB (CD137) agonist (e.g, anti-CD137 antibody), GITR agonist (e.g, anti-GITR antibody), TIM3 agonist (e.g, anti-TIM3 antibody), or combinations thereof.

[0521] In some aspects, an immune cell disclosed herein (e.g, a cell expressing a CAR or TCR comprising a chimeric polypeptide of the present disclosure) can be administered to the subject prior to or after the administration of the additional therapeutic agent. In other aspects, the immune cell is administered to the subject concurrently with the additional therapeutic agent. In certain aspects, the immune cell ( e.g ., a T cell) and the additional therapeutic agent can be administered concurrently as a single composition in a pharmaceutically acceptable carrier. In other aspects, the immune cell (e.g., a T cell) and the additional therapeutic agent are administered concurrently as separate compositions. In some aspects, the additional therapeutic agent and the immune cell are administered sequentially.

[0522] The present disclosure also provides the use of any polypeptides, polynucleotides, vectors, cells, compositions, or kits disclosed herein for the manufacture of a medicament for treating cancer in a subject in need thereof.

X Kits

[0523] The present disclosure also provides kits for practicing any of the methods of the present disclosure. The present disclosure provides kits comprising any of the polypeptides (e.g, chimeric polypeptides of the present disclosure), polynucleotides, vectors, or cells disclosed herein, or combinations thereof.

[0524] In some aspects, the kit comprises (a) a polynucleotide encoding a chimeric polypeptide disclosed herein, and (b) a polynucleotide encoding one or more key polypeptides capable of binding to the structural region of the cage polypeptide of the chimeric polypeptide.

[0525] In some aspects, the kit comprises

(a) one or more expression vectors comprising one or more polynucleotides encoding a chimeric polypeptide disclosed herein, operatively linked to a promoter; and,

(b) one or more expression vectors comprising one or more polynucleotides encoding one or more key polypeptides capable of binding to the structural region of the cage polypeptide of a chimeric polypeptide disclosed herein, wherein the one or more polynucleotides encoding the one or more key polypeptides are operatively linked to at least one promoter (e.g, an inducible promoter).

[0526] In some aspects, the disclosure provides a kit comprising (i) a polynucleotide (e.g, a vector) comprising a nucleic acid encoding a chimeric polypeptide of the present disclosure, a key polypeptide, or a combination thereof, (ii) a chimeric antigen receptor (CAR) or a T cell receptor (TCR), or (iii) a combination thereof, and optionally instructions for treating a tumor according to any of the methods disclosed herein.

[0527] Also provided is a kit comprising (i) a polynucleotide ( e.g ., a vector) comprising a nucleic acid encoding a chimeric polypeptide of the present disclosure, a key polypeptide, or a combination thereof, (ii) a vector comprising a chimeric antigen receptor (CAR) or a T cell receptor (TCR), or (iii) a combination thereof, and optionally instructions for preparing a cell composition according to the methods disclosed herein.

[0528] In some aspects, the present disclosure provides kits comprising the compositions disclosed herein, for example, (i) a cell, e.g. an immune cell, that expresses a CAR or TCR comprising a chimeric polypeptide of the present disclosure, (ii) a polynucleotide comprising a nucleic acid encoding a chimeric polypeptide of the present disclosure, (iii) a polynucleotide comprising a nucleic acid encoding a key polypeptide disclosed herein, (iv) a polypeptide comprising a key polypeptide disclosed herein (e.g, a key polypeptide conjugated or fused to a membrane permeating peptide), (v) a key polypeptide disclosed herein, (vi) a single vector comprising a nucleic acid encoding at least one chimeric polypeptide and at least one key polypeptide, (vii) a single vector comprising a nucleic acid encoding at least one chimeric polypeptide, (viii) a single vector comprising a nucleic acid encoding at least one key polypeptide, (ix) a set of vectors wherein a vector comprises a nucleic acid encoding at least one chimeric polypeptide and another vector comprises a nucleic acid encoding at least one key polypeptide, a single vector comprising a nucleic acid encoding at least one chimeric polypeptide and at least one key polypeptide, (x) a vector or set of vector encoding a CAR or a TCR, or (xi) a combination thereof. In some aspects, the kits further comprise instructions for their use.

[0529] The present disclosure provides kits for the treatment of cancer comprising an immune cell disclosed herein, wherein the cell expresses a CAR or TCR comprising a chimeric polypeptide disclosed herein. The present disclosure also provides kits for the treatment of cancer comprising an immune cell disclosed herein, wherein the cell expresses a CAR or TCR comprising a chimeric polypeptide disclosed herein, and at least one key polypeptide.

SEQUENCES

Examples

Example 1

Material and Methods

[0530] Unless indicated otherwise, the Examples described below used one or more of the following materials and methods.

Cell Culture and Lentiviral Transduction [0531] Jurkat, SupTl, and Jekol cell lines were obtained from American Type Culture Collection (Manassas VA). SupTl and Jekol cells were maintained in RPMI 1640 media with GLUTAMAX™ (Gibco) containing 10% fetal calf serum (Gibco). For lentiviral transduction, SupTl and Jurkat cells were fed with fresh media 4-16 hours before transduction, then incubated with lentivirus in complete media supplemented with LENTIBOOST™ at the manufacturers recommended concentration (Sirion Biotech). 18 hours after transfection, lentivirus and LENTIBOOST™ were diluted by addition of 1 volume fresh media.

[0532] Pre-selected, cryopreserved primary human CD4 and CD8 T cells from normal donors were obtained from Bloodworks (Seattle, WA). Human T cells were cultured in OPTMIZER™ medium (Thermo Fisher) supplemented with Immune Cell Serum Replacement (Thermo Fisher), 2mM L-glutamine (Gibco), 2mM GLUTAMAX™ (Gibco), 200IU/ml IL-2 (R&D systems), 120 IU/ml IL-7 (R&D systems), and 20 IU/ml IL-15 (R&D systems).

[0533] For lentiviral transduction, T cells were stimulated with a 1:100 dilution of T cell TRANSACT™ (Miltenyi) for 30 hours. Virus was then added to T cells for 18-24 hours. Stimulation and viral infection were then terminated by addition of 7 volumes of fresh media without TRANSACT™, and cells were cultured for 3-7 additional days before analysis.

Flow Cytometry

[0534] Flow cytometry was performed on a Ze5 cytometer (Biorad). To determine expression of surface markers, between lxlO⁵ and 2xl0⁵ total cells were transferred to a V bottom 96-well culture dish (Corning). Cells were washed twice with flow cytometry staining buffer (eBioscience), then stained with the relevant reagents in a total volume of 50 ul flow cytometry staining buffer for 30 minutes on ice. After staining, cells were washed twice with flow cytometry staining buffer, fixed in FLUOROFIX™ Buffer (Biolegend) and kept at 4°C in the dark until analysis. Table 5 (below) provides the antibodies used.

Table 5. Antibodies for Flow Cytometry [0535] Purified recombinant Rorl linked to human Ig Fc was conjugated to ALEXA FLUOR 647^® dye for detection. EFLUOR 780^® Fixable Viability dye (eBioscience) was included during primary antibody stain at a 1:800 dilution. Flow cytometry data were analyzed using FLOWJO™ 10 (Tree Star).

Jeko Co-Culture Experiments

[0536] For co-culture of Jeko target cells with CAR transduced SupTl or primary T cells, cells were stained with VIASTAIN™ AOPI solution (Nexcelom Bioscience) to identify viable cells, and counted on a CELLOMETER^® automated cell counting system (Nexcelom Bioscience). An appropriate number of target and effector cells were collected by centrifugation at 300xg for 5 minutes, and resuspended in complete media without cytokines at a final concentration of lxlOVml at the indicated effectontarget ratios. Cells were co cultured for 24 or 48 hours, followed by harvest of supernatant for cytokine secretion (primary T cells) or analysis of surface marker expression by flow cytometry (primary T cells and SupTl).

T Cell Killing Assay

[0537] To assess T cell cytotoxicity, CAR T cells were seeded at a 1:1 or 1:5 effector to target ratio (E:T) ratio with NUCLIGHT™ Red (NLR) -ROR1+ target or NLR RorlKO Jekol target cells in a 48 well plate (Coming). Tumor cell killing was determined via flow cytometry by measurement of the fraction of viable NLR+ cells remaining at the indicated time point relative to tumor cells alone.

Cytokine Secretion Assay

[0538] Cytokine secretion was measured with a custom V-PLEX^® human proinflammatory kit (human IFN-g, IL-2, TNF-a) (Meso Scale Discovery). Supernatant was collected from T cells cultured under the indicated conditions. Supernatant was centrifuged for 5 minutes at 300xg to remove cells and debris, then frozen at -80°C. For detection, supernatant was diluted 1:5 or 1:10 with MSD calibrator diluent, and analyzed according to manufacturer’s instructions. Example 2

Analysis of the Ability of Degron Peptides to Downmodulate CAR Expression

[0539] To assess the ability of the degron peptides disclosed herein to downmodulate chimeric antigen receptor (CAR) expression, ROR1 CARs with a degron peptide inserted at the C-terminus of the CAR were constructed. FIG. 4 provides a schematic of an exemplary CAR construct with a degron peptide at the C-terminus. The CARs included one of the following degron peptides: (i) GG, (ii) RHWRGQEG (SEQ ID NO: 160), (iii) RWGRRG (SEQ ID NO: 161), (iv) TMAAGRAPGK (SEQ ID NO: 162), (v) VLIRVTYCGL (SEQ ID NO: 142), or (vi) EIAGLLGG (SEQ ID NO: 163). A truncated CD19 marker was additionally linked to the CAR constructs via a 2a cleavable peptide, which was used as a marker for successful transduction.

[0540] Pre-selected, cryopreserved primary human CD4+ and CD8 T+ cells from normal donors were obtained from Bloodworks (Seattle WA). Human T cells were cultured in OpTmizer medium (Thermo Fisher) supplemented with Immune Cell Serum Replacement (Thermo Fisher), 2 mM L-glutamine (Gibco), 2 mM Glutamax (Gibco), 200 IU/ml IL-2 (R&D systems), 120 IU/ml IL-7 (R&D systems), and 20 IU/ml IL-15 (R&D systems). Primary T cells were transduced with the CAR constructs.

[0541] To transduce the T cells, the ROR1 constructs described above were expressed in a lentivirus vector, and then the T cells were stimulated with a 1 : 100 dilution of T cell TransAct (Miltenyi) for 30 hours. And, then, the lentivirus was added to the T cells for 18-24 hours. Stimulation and viral infection were then terminated by addition of 7 volumes of fresh media without TransAct, and cells were cultured for 3-7 additional days before analysis. As noted above, transduction efficiency was assessed by staining for CD 19 expression on the T cells using flow cytometry. The transduced cells were then treated with recombinant RORl-Fc fusion protein, which was conjugated to Alexa647 dye. CAR expression on the T cells was measured by analyzing the mean fluorescence intensity of the bound RORl-Fc protein using flow cytometry.

[0542] As shown in FIG. 5A, the insertion of degron peptides GG and RHWRGQEG (SEQ ID NO: 160) at the C-terminus of a CAR construct had minimal effect on downmodulating CAR expression on the T cells. In contrast, degron peptides RWGRRG (SEQ ID NO: 161) and VLIRVTYCGL (SEQ ID NO: 161) were highly effective in reducing CAR expression when inserted at the C-terminus of the CAR constructs ( see FIGs. 5A and 5B). The strong activity of degron peptides RWGRRG (SEQ ID NO: 161) and VLIRVTYCGL (SEQ ID NO: 142) on cell- surface membrane protein expression stands in contrast to the well characterized C-terminal degron derived from mouse ornithine decarboxylase (cODC), which does not downregulate cell-surface membrane protein expression (FIG. 5C). These results demonstrate that the insertion of certain degron peptides ( e.g ., those comprising the sequence CGL) at the C- terminus of a CAR can effectively downmodulate CAR expression in primary T cells.

Example 3

Analysis of the Ability of LockR Proteins to Cage the Bioactive CGL Peptide

[0543] As described herein, the degron peptides of the present disclosure are caged or sequestered within the latch region of a cage polypeptide, such that in the absence of the corresponding key polypeptide, the degron peptide remains in an inactive state (i.e., does not lead to ubiqutination and degradation of the molecule expressing the degron peptide). To assess whether the degron peptides disclosed herein can be successfully caged (i.e., inactive form) when incorporated into CARs, LockR proteins (i.e., cage polypeptides) were used. Briefly, the degron peptide CGL was attached to the C-terminus of the following LockR proteins: (i) Cage 13 (SEQ ID NO: 13), (ii) Cage 16 (SEQ ID NO: 16), (iii) Cage 4 (SEQ ID NO: 4), and (iv) Cage 12 (SEQ ID NO: 12). Then, the chimeric polypeptides comprising the LockR protein and degron peptide were inserted at the C-terminus of an ROR1 construct as described in Example 1

[0544] Primary T cells were transduced with the CAR constructs and subsequently, treated with recombinant RORl-Fc fusion protein, as described in Example 1. CAR expression on the T cells was measured by analyzing the mean fluorescence intensity of the bound RORl-Fc protein using flow cytometry.

[0545] As shown in FIG. 6, each of the LockR proteins tested was able to cage or sequester the CGL degron peptide, such that there was no detectable reduction in CGL-mediated reduction in CAR expression, as compared to the control cells (i.e., cells transduced with CAR construct without the LockR protein + CGL degron peptide regulatory element). This result demonstrates that the degron peptides disclosed herein can be effectively caged or sequestered in an inactive state when attached to the C-terminus of the latch region of a LockR protein.

Example 5 Analysis of Antigen Recognition of CARs Expressing a LockR Protein Containing a

Degron Motif

[0546] To assess whether the expression of a chimeric polypeptide disclosed herein ( i.e ., cage polypeptide with a degron motif attached to the C-terminus of the latch region) can affect the ability of a CAR to recognize cognate antigen, SupTl cells (American Type Culture Collection (Manassas, VA)) were transduced with ROR1 -specific CAR construct (CAR) (i.e., control construct) or ROR1 -specific CAR constructs linked at the C-terminus to 3 independent lockR designs containing the CGL degron motif (CAR-lockR-CGL) (i.e., those used in Example 2 -’’Cage 14” (SEQ ID NO: 14), “Cage 16” (SEQ ID NO: 16), and “Cage 12” (SEQ ID NO: 12). To transduce the SupTl cells, the cells were fed with fresh media 4-16 hours before transduction, then incubated with lentivirus in complete media + LentiBOOST at the manufacturers recommended concentration (Sirion Biotech). 18 hours after transfection, lentivirus expressing the ROR1 constructs and LentiBOOST were diluted by addition of 1 volume fresh media. The transduced SupTl cells were then cultured in the absence (unstimulated) or presence of ROR1 -expressing Jekol target cells (+ Target cells) for 24 hours. CAR expression and the activation marker CD69 on transduced Suptl cells were determined by flow cytometry.

[0547] As shown in FIG. 7, for each of the CARs tested (both the control construct and CAR constructs linked at the C-terminus to a LockR protein containing a CGL degron peptide), stimulating the transduced SupTl cells with the ROR1 -expressing target cells resulted in similar increase in CD69 expression with a corresponding reduction in CAR expression.

[0548] As further confirmation, the control construct or the CAR construct linked at the C- terminus to a LockR protein containing a CGL degron peptide was transduced into primary human T cells and tested for their ability to recognize antigen. Briefly, a 1 : 1 mixture of CD4+ and CD8+ T cells were stimulated and transduced with the ROR1 -specific CAR constructs (as described in Example 1). 4 days later, T cells were left unstimulated, or challenged with ROR1- expressing Jekol target cells (+Target Cells). Prior to the challenge, the cells were stained with Viastain AOPI solution (Nexcelom Bioscience) to identify viable cells and counted on a Cellometer (Nexcelom Bioscience). An appropriate number of target and effector cells were collected by centrifugation at 300xg for 5 minutes, and resuspended in complete media without cytokines at a final concentration of lxlOVml. 24 hours after challenge, expression of the activation marker CD69 and the activation/exhaustion marker PD1 on transduced primary T cells were determined by flow cytometry. The functional activity of the transduced primary T cells was assessed using the T cell killing assay and the cytokine secretion assay as described in Example 1.

[0549] In agreement with the above results using SupTl cells, both CD69 and PD1 expression was similar in primary T cells transduced with either the control CAR construct or the CAR constructs expressing at the C-terminus a LockR protein containing a CGL degron peptide (see FIG. 8). Similarly, the functional activities (i.e., cytolytic killing, and IFN-g and IL-2 production) of the primary T cells transduced with the ROR1 CAR constructs comprising the C-terminal fusion of lockR designs containing the CGL degron motif were comparable to the control cells (i.e., primary T cells transduced with ROR1 construct lacking the degron motif) (see FIGs. 9A and 9B).

[0550] Collectively, the above results demonstrate that the chimeric polypeptides of the present disclosure (i.e., cage polypeptide comprising a degron peptide linked to the C-terminus of the latch region) can be used to modulate the expression of various protein (e.g., chimeric antigen receptor) on immune cells (e.g, T cells).

[0551] It is to be appreciated that the Detailed Description section, and not the Summary and Abstract sections, is intended to be used to interpret the claims. The Summary and Abstract sections may set forth one or more but not all exemplary embodiments of the present disclosure as contemplated by the inventor(s), and thus, are not intended to limit the present disclosure and the appended claims in any way.

[0552] The present disclosure has been described above with the aid of functional building blocks illustrating the implementation of specified functions and relationships thereof. The boundaries of these functional building blocks have been arbitrarily defined herein for the convenience of the description. Alternate boundaries can be defined so long as the specified functions and relationships thereof are appropriately performed.

[0553] The foregoing description of the specific embodiments will so fully reveal the general nature of the disclosure that others can, by applying knowledge within the skill of the art, readily modify and/or adapt for various applications such specific embodiments, without undue experimentation, without departing from the general concept of the present disclosure. Therefore, such adaptations and modifications are intended to be within the meaning and range of equivalents of the disclosed embodiments, based on the teaching and guidance presented herein. It is to be understood that the phraseology or terminology herein is for the purpose of description and not of limitation, such that the terminology or phraseology of the present specification is to be interpreted by the skilled artisan in light of the teachings and guidance.

[0554] The breadth and scope of the present disclosure should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.

[0555] The contents of all cited references (including literature references, U.S. or foreign patents or patent applications, and websites) that are cited throughout this application are hereby expressly incorporated by reference as if written herein in their entireties for any purpose, as are the references cited therein. Where any inconsistencies arise, material literally disclosed herein controls.

Claims

WHAT IS CLAIMED IS:

1. A polynucleotide encoding a chimeric polypeptide which comprises a cage polypeptide comprising:

(i) a structural region comprising an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 13 (Cage 13); SEQ ID NO: 14 (Cage 14); SEQ ID NO: 15 (Cage 15); SEQ ID NO: 16 (Cage 16); SEQ ID NO: 17 (Cage 17); SEQ ID NO: 18 (Cage 18); SEQ ID NO: 1 (Cage 1); SEQ ID NO: 2 (Cage 2); SEQ ID NO: 3 (Cage 3); SEQ ID NO: 4 (Cage 4); SEQ ID NO: 5 (Cage 5); SEQ ID NO: 6 (Cage 6); SEQ ID NO: 7 (Cage 7); SEQ ID NO: 8 (Cage 8); SEQ ID NO: 9 (Cage 9); SEQ ID NO: 10 (Cage 10); SEQ ID NO: 11 (Cage 11); or SEQ ID NO: 12 (Cage 12), and

(ii) a latch region comprising a degron peptide comprising the amino acid sequence of CGL, wherein the latch region is capable of binding to the structural region.

2. The polynucleotide of claim 1, wherein the degron peptide comprises YCGL (SEQ ID NO: 136), TYCGL (SEQ ID NO: 137), VTYCGL (SEQ ID NO: 138), RVTYCGL (SEQ ID NO: 139), IR VTYCGL (SEQ ID NO: 140), LIRVTYCGL (SEQ ID NO: 141), or VLIR VTYCGL (SEQ ID NO: 142).

3. The polynucleotide of claim 1, wherein the degron peptide comprises an amino acid sequence at least about 70%, at least about 80%, at least about 90%, or about 100% identical to VLIR VTYCGL (SEQ ID NO: 142).

4. The polynucleotide of claim 1, wherein the structural region comprises any one of the amino acid sequences as set forth in SEQ ID NO: 13 (Cage 13); SEQ ID NO: 14 (Cage 14); SEQ ID NO: 15 (Cage 15); SEQ ID NO: 16 (Cage 16); SEQ ID NO: 17 (Cage 17); SEQ ID NO: 18 (Cage 18); SEQ ID NO: 1 (Cage 1); SEQ ID NO: 2 (Cage 2); SEQ ID NO: 3 (Cage 3); SEQ ID NO: 4 (Cage 4); SEQ ID NO: 5 (Cage 5); SEQ ID NO: 6 (Cage 6); SEQ ID NO: 7 (Cage 7); SEQ ID NO: 8 (Cage 8); SEQ ID NO: 9 (Cage 9); SEQ ID NO: 10 (Cage 10); SEQ ID NO: 11 (Cage 11); or SEQ ID NO: 12 (Cage 12).

5. The polynucleotide of any one of claims 1 to 4, wherein the degron peptide is linked to the C-terminus of the latch region of the cage polypeptide.

6. The polynucleotide of claim 5, wherein the degron peptide is linked to the C-terminus of the amino acid sequence set forth in SEQ ID NO: 13 (Cage 13).

7. The polynucleotide of claim 5, wherein the degron peptide is linked to the C-terminus of the amino acid sequence set forth in SEQ ID NO: 14 (Cage 14).

8. The polynucleotide of claim 5, wherein the degron peptide is linked to the C-terminus of the amino acid sequence set forth in SEQ ID NO: 15 (Cage 15).

9. The polynucleotide of claim 5, wherein the degron peptide is linked to the C-terminus of the amino acid sequence set forth in SEQ ID NO: 16 (Cage 16).

10. The polynucleotide of claim 5, wherein the degron peptide is linked to the C-terminus of the amino acid sequence set forth in SEQ ID NO: 17 (Cage 17).

11. The polynucleotide of claim 5, wherein the degron peptide is linked to the C-terminus of the amino acid sequence set forth in SEQ ID NO: 18 (Cage 18).

12. The polynucleotide of claim 5, wherein the degron peptide is linked to the C-terminus of the amino acid sequence set forth in SEQ ID NO: 1 (Cage 1).

13. The polynucleotide of claim 5, wherein the degron peptide is linked to the C-terminus of the amino acid sequence set forth in SEQ ID NO: 2 (Cage 2).

14. The polynucleotide of claim 5, wherein the degron peptide is linked to the C-terminus of the amino acid sequence set forth in SEQ ID NO: 3 (Cage 3).

15. The polynucleotide of claim 5, wherein the degron peptide is linked to the C-terminus of the amino acid sequence set forth in SEQ ID NO: 4 (Cage 4).

16. The polynucleotide of claim 5, wherein the degron peptide is linked to the C-terminus of the amino acid sequence set forth in SEQ ID NO: 5 (Cage 5).

17. The polynucleotide of claim 5, wherein the degron peptide is linked to the C-terminus of the amino acid sequence set forth in SEQ ID NO: 6 (Cage 6).

18. The polynucleotide of claim 5, wherein the degron peptide is linked to the C-terminus of the amino acid sequence set forth in SEQ ID NO: 7 (Cage 7).

19. The polynucleotide of claim 5, wherein the degron peptide is linked to the C-terminus of the amino acid sequence set forth in SEQ ID NO: 8 (Cage 8).

20. The polynucleotide of claim 5, wherein the degron peptide is linked to the C-terminus of the amino acid sequence set forth in SEQ ID NO: 9 (Cage 9).

21. The polynucleotide of claim 5, wherein the degron peptide is linked to the C-terminus of the amino acid sequence set forth in SEQ ID NO: 10 (Cage 10).

22. The polynucleotide of claim 5, wherein the degron peptide is linked to the C-terminus of the amino acid sequence set forth in SEQ ID NO: 11 (Cage 11).

23. The polynucleotide of claim 5, wherein the degron peptide is linked to the C-terminus of the amino acid sequence set forth in SEQ ID NO: 12 (Cage 12).

24. The polynucleotide of any one of claims 1 to 6, wherein the chimeric polypeptide comprises an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 13 (Cage 13).

25. The polynucleotide of any one of claims 1 to 5 and 7, wherein the chimeric polypeptide comprises an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 14 (Cage 14).

26. The polynucleotide of any one of claims 1 to 5 and 8, wherein the chimeric polypeptide comprises an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 15 (Cage 15).

27. The polynucleotide of any one of claims 1 to 5 and 9, wherein the chimeric polypeptide comprises an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 17 (Cage 17).

28. The polynucleotide of any one of claims 1 to 5 and 10, wherein the chimeric polypeptide comprises an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 16 (Cage 16).

29. The polynucleotide of any one of claims 1 to 5 and 11, wherein the chimeric polypeptide comprises an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 18 (Cage 18).

30. The polynucleotide of any one of claims 1 to 5 and 12, wherein the chimeric polypeptide comprises an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 1 (Cage 1).

31. The polynucleotide of any one of claims 1 to 5 and 13, wherein the chimeric polypeptide comprises an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 2 (Cage 2).

32. The polynucleotide of any one of claims 1 to 5 and 14, wherein the chimeric polypeptide comprises an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 3 (Cage 3).

33. The polynucleotide of any one of claims 1 to 5 and 15, wherein the chimeric polypeptide comprises an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 4 (Cage 4).

34. The polynucleotide of any one of claims 1 to 5 and 16, wherein the chimeric polypeptide comprises an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 5 (Cage 5).

35. The polynucleotide of any one of claims 1 to 5 and 17, wherein the chimeric polypeptide comprises an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 6 (Cage 6).

36. The polynucleotide of any one of claims 1 to 5 and 18, wherein the chimeric polypeptide comprises an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 7 (Cage 7).

37. The polynucleotide of any one of claims 1 to 5 and 19, wherein the chimeric polypeptide comprises an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 8 (Cage 8).

38. The polynucleotide of any one of claims 1 to 5 and 20, wherein the chimeric polypeptide comprises an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 9 (Cage 9).

39. The polynucleotide of any one of claims 1 to 5 and 21, wherein the chimeric polypeptide comprises an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 10 (Cage 10).

40. The polynucleotide of any one of claims 1 to 5 and 22, wherein the chimeric polypeptide comprises an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 11 (Cage 11).

41. The polynucleotide of any one of claims 1 to 5 and 23, wherein the chimeric polypeptide comprises an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 12 (Cage 12).

42. The polynucleotide of any one of claims 1 to 41, wherein the chimeric polypeptide further comprises a signaling domain.

43. The polynucleotide of claim 42, wherein the signaling domain comprises a domain derived from CD3zeta, FcR gamma, FcR beta, CD3 gamma, CD3 delta, CD3 epsilon, CD5, CD22, CD79a, CD79b, or CD66d.

44. The polynucleotide of any one of claims 1 to 43, wherein the chimeric polypeptide further comprises a co-stimulatory domain.

45. The polynucleotide of claim 44, wherein the co-stimulatory domain comprises a domain derived from 2B4, HVEM, ICOS, LAG3, DAP 10, DAP 12, CD27, CD28, 4- 1BB (CD 137), 0X40 (CD134), CD30, CD40, ICOS (CD278), glucocorticoid-induced tumor necrosis factor receptor (GITR), lymphocyte function-associated antigen- 1 (LFA-1), CD2, CD7, LIGHT, NKG2C, or B7-H3.

46. The polynucleotide of any one of claims 1 to 45, wherein the chimeric polypeptide further comprises an antigen binding domain.

47. The polynucleotide of claim 46, wherein the antigen-binding domain comprises an antibody or an antigen binding fragment thereof that specifically binds to an epitope on a tumor antigen.

48. The polynucleotide of claim 46 or 47, wherein the antigen binding domain is an Ig NAR, a Fab, a Fab’, aF(ab)’2, aF(ab)’3, anFv, a single chain variable fragment (scFv), a bis-scFv, a (scFv)2, a minibody, a diabody, a triabody, a tetrabody, an intrabody, a disulfide stabilized Fv protein (dsFv), a unibody, or a nanobody.

49. The polynucleotide of any one of claims 46 to 48, wherein the antigen binding domain specifically binds to CD 19, TRAC, TCRp, BCMA, CLL-1, CS1, CD38, CD 19, TSHR, CD123, CD22, CD30, CD70, CD171, CD33, EGFRvIII, GD2, GD3, Tn Ag, PSMA, ROR1, ROR2, GPC1, GPC2, FLT3, FAP, TAG72, CD44v6, CEA, EPCAM, B7H3, KIT, IL-13Ra2, Mesothelin, IL-llRa, PSCA, PRSS21, VEGFR2, LewisY, CD24, PDGFR-beta, S SEA-4, CD20, Folate receptor alpha, ERBB2 (Her2/neu), MUC1, MUC16, EGFR, NCAM, Prostase, PAP, ELF2M, Ephrin B2, IGF-I receptor, CAIX, LMP2, gplOO, bcr-abl, tyrosinase, EphA2, Fucosyl GM1, sLe, GM3, TGS5, HMWMAA, o-acetyl-GD2, Folate receptor beta, TEM1/CD248, TEM7R, CLDN6, GPRC5D, CXORF61, CD97, CD 179a, ALK, Poly sialic acid, PLAC1, GloboH, NY- BR-1, UPK2, HAVCR1, ADRB3, PANX3, GPR20, LY6K, OR51E2, TARP, WT1, NY-ESO-1, L AGE-1 a, MAGE-A1, legumain, HPV E6,E7, MAGE Al, ETV6-AML, sperm protein 17, XAGE1, Tie 2, MAD-CT-1, MAD-CT- 2, Fos-related antigen 1, p53, p53 mutant, prostein, survivin and telomerase, PCTA-l/Galectin 8, MelanA/MARTl, Ras mutant, hTERT, sarcoma translocation breakpoints, ML-IAP, ERG (TMPRSS2 ETS fusion gene), NA17, PAX3, Androgen receptor, Cyclin Bl, MYCN, RhoC, TRP- 2, CYPIBI, BORIS, SART3, PAX5, OY-TES1, LCK, AKAP-4, SSX2, RAGE-1, human telomerase reverse transcriptase, RU1, RU2, intestinal carboxyl esterase, mut hsp70-2, CD79a, CD79b, CD72, LAIR1, FCAR, LILRA2, CD300LF, CLEC12A, BST2, EMR2, LY75, GPC3, FCRL5, IGLL1, or any combinations thereof.

50. The polynucleotide of any one of claims 1 to 49, wherein the chimeric polypeptide comprises a chimeric antigen receptor (CAR).

51. The polynucleotide of claim 50, wherein the CAR is designed as a standard CAR, a split CAR, an off-switch CAR, an on-switch CAR, a first-generation CAR, a second- generation CAR, a third-generation CAR, or a fourth-generation CAR.

52. The polynucleotide of claims 46 to 51, wherein the chimeric polypeptide further comprises a transmembrane domain.

53. The polynucleotide of any one of claims 46 to 52, which encodes a chimeric antigen receptor comprising:

(i) the chimeric polypeptide of any one of claims 1 to 51;

(ii) an antigen-binding domain that binds to an epitope on a tumor antigen expressed on a target cell; and

(iii) a transmembrane domain.

54. The polynucleotide of claim 52 or 53, wherein the CAR further comprises a CAR spacer between the antigen binding domain and the transmembrane domain.

55. The polynucleotide of any one of claims 1 to 49, wherein the chimeric polypeptide comprises a T cell receptor.

56. The polynucleotide of any one of claims 1 to 55, wherein the chimeric polypeptide induces an IFNy and/or IL-2 expression in a cell.

57. The polynucleotide of any one of claims 1 to 56, wherein the chimeric polypeptide is capable of being degraded through a ubiquitin dependent pathway.

58. The polynucleotide of any one of claims 1 to 57, wherein the chimeric polypeptide is capable of being degraded when in contact with a key polypeptide.

59. The polynucleotide of any one of claims 1 to 58, wherein the polynucleotide is a DNA molecule, a RNA molecule, or any combination thereof.

60. A polynucleotide set comprising the polynucleotide of any one of claims 1 to 59 and a second polynucleotide.

61. The polynucleotide set of claim 60, wherein the second polynucleotide encode a key polypeptide that is capable of inhibiting binding of the latch region to the structural region of the chimeric polypeptide when the key polypeptide comes in contact with the chimeric polypeptide.

62. The polynucleotide set of claim 61, wherein the key polypeptide comprises an amino acid sequence having at least about 70%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, or about 100% sequence identity to the sequence as set forth in SEQ ID NO: 19 (Key 1), SEQ ID NO: 20 (Key 2), SEQ ID NO: 21 (Key 3), SEQ ID NO: 22 (Key 4), SEQ ID NO: 23 (Key 5), SEQ ID NO: 24 (Key 6), SEQ ID NO: 25 (Key 7), SEQ ID NO: 26 (Key 8), SEQ ID NO: 27 (Key 9), SEQ ID NO: 28 (Key 10), SEQ ID NO: 29 (Key 11), SEQ ID NO: 30 (Key 12), SEQ ID NO: 31 (Key 13), SEQ ID NO: 32 (Key 15), SEQ ID NO: 33 (Key 16), SEQ ID NO: 34 (Key 17), or SEQ ID NO: 35 (Key 18), wherein the key polypeptide is capable of binding to the structural region of the chimeric polypeptide.

63. The polynucleotide set of claim 61 or 62, wherein the chimeric polypeptide comprises an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 1 (Cage 1), and the key polypeptide comprises an amino acid sequence having at least about 70%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, or about 100% sequence identity to the sequence as set forth in SEQ ID NO: 19 (Key 1).

64. The polynucleotide set of claim 61 or 62, wherein the chimeric polypeptide comprises an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 2 (Cage 2), and the key polypeptide comprises an amino acid sequence having at least about 70%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, or about 100% sequence identity to the sequence as set forth in SEQ ID NO: 20 (Key 2).

65. The polynucleotide set of claim 61 or 62, wherein the chimeric polypeptide comprises an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 3 (Cage 3), and the key polypeptide comprises an amino acid sequence having at least about 70%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, or about 100% sequence identity to the sequence as set forth in SEQ ID NO: 21 (Key 3).

66. The polynucleotide set of claim 61 or 62, wherein the chimeric polypeptide comprises an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 4 (Cage 4), and the key polypeptide comprises an amino acid sequence having at least about 70%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, or about 100% sequence identity to the sequence as set forth in SEQ ID NO: 22 (Key 4).

67. The polynucleotide set of claim 61 or 62, wherein the chimeric polypeptide comprises an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 5 (Cage 5), and the key polypeptide comprises an amino acid sequence having at least about 70%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, or about 100% sequence identity to the sequence as set forth in SEQ ID NO: 23 (Key 5).

68. The polynucleotide set of claim 61 or 62, wherein the chimeric polypeptide comprises an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 6 (Cage 6), and the key polypeptide comprises an amino acid sequence having at least about 70%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, or about 100% sequence identity to the sequence as set forth in SEQ ID NO: 24 (Key 6).

69. The polynucleotide set of claim 49 or 50, wherein the chimeric polypeptide comprises an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 7 (Cage 7), and the key polypeptide comprises an amino acid sequence having at least about 70%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, or about 100% sequence identity to the sequence as set forth in SEQ ID NO: 25 (Key 7).

70. The polynucleotide set of claim 49 or 50, wherein the chimeric polypeptide comprises an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 8 (Cage 8), and the key polypeptide comprises an amino acid sequence having at least about 70%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, or about 100% sequence identity to the sequence as set forth in SEQ ID NO: 26 (Key 8).

71. The polynucleotide set of claim 49 or 50, wherein the chimeric polypeptide comprises an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 9 (Cage 9), and the key polypeptide comprises an amino acid sequence having at least about 70%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, or about 100% sequence identity to the sequence as set forth in SEQ ID NO: 27 (Key 9).

72. The polynucleotide set of claim 49 or 50, wherein the chimeric polypeptide comprises an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 10 (Cage 10), and the key polypeptide comprises an amino acid sequence having at least about 70%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, or about 100% sequence identity to the sequence as set forth in SEQ ID NO: 28 (Key 10).

73. The polynucleotide set of claim 49 or 50, wherein the chimeric polypeptide comprises an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 11 (Cage 11), and the key polypeptide comprises an amino acid sequence having at least about 70%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, or about 100% sequence identity to the sequence as set forth in SEQ ID NO: 29 (Key 11).

74. The polynucleotide set of claim 49 or 50, wherein the chimeric polypeptide comprises an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 12 (Cage 12), and the key polypeptide comprises an amino acid sequence having at least about 70%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, or about 100% sequence identity to the sequence as set forth in SEQ ID NO: 30 (Key 12).

75. The polynucleotide set of claim 61 or 62, wherein the chimeric polypeptide comprises an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 13 (Cage 13) or SEQ ID NO: 14 (Cage 14), and the key polypeptide comprises an amino acid sequence having at least about 70%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, or about 100% sequence identity to the sequence as set forth in SEQ ID NO: 31 (Key 13 or 14).

76. The polynucleotide set of claim 61 or 62, wherein the chimeric polypeptide comprises an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 15 (Cage 15), and the key polypeptide comprises an amino acid sequence having at least about 70%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, or about 100% sequence identity to the sequence as set forth in SEQ ID NO: 32 (Key 15).

77. The polynucleotide set of claim 61 or 62, wherein the chimeric polypeptide comprises an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 16 (Cage 16), and the key polypeptide comprises an amino acid sequence having at least about 70%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, or about 100% sequence identity to the sequence as set forth in SEQ ID NO: 33 (Key 16).

78. The polynucleotide set of claim 61 or 62, wherein the chimeric polypeptide comprises an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 17 (Cage 17), and the key polypeptide comprises an amino acid sequence having at least about 70%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, or about 100% sequence identity to the sequence as set forth in SEQ ID NO: 34 (Key 17).

79. The polynucleotide set of claim 61 or 62, wherein the chimeric polypeptide comprises an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the sequence set forth in SEQ ID NO: 18 (Cage 18), and the key polypeptide comprises an amino acid sequence having at least about 70%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, or about 100% sequence identity to the sequence as set forth in SEQ ID NO: 35 (Key 18).

80. A vector comprising the polynucleotide of any of claims 1 to 59 and/or the polynucleotide set of any one of claims 60 to 79 operably linked to one or more regulatory elements.

81. The vector of claim 80, which is a viral vector, a mammalian vector, or a bacterial vector.

82. The vector of claims 80 or 81, which is a retroviral vector.

83. The vector of any one of claim 80 to 82, which is selected from the group consisting of an adenoviral vector, a lentivirus, a Sendai virus vector, a baculoviral vector, an Epstein Barr viral vector, a papovaviral vector, a vaccinia viral vector, a herpes simplex viral vector, a hybrid vector, and an adeno associated virus (AAV) vector.

84. The vector of claim 82 or 83, which is a lentivirus.

85. The vector of any one of claims 80 to 84, wherein the polynucleotide encoding the chimeric polypeptide and the second polynucleotide encoding the key polypeptide are on the same vector.

86. The vector of any one of claims 80 to 84, wherein the polynucleotide encoding the chimeric polypeptide and the second polynucleotide encoding the key polypeptide are on different vectors.

87. The vector of any one of claims 80 to 86, wherein the second polynucleotide encoding the key polypeptide is operably linked to an inducible promoter.

88. A chimeric polypeptide encoded by a polynucleotide of any one of claims 1 to 59 or the vector of any one of claims 80 to 87.

89. A chimeric polypeptide encoded by the polynucleotide set of any one of claims 60 to 79 or the vector of any one of claims 80 to 87.

90. A chimeric polypeptide comprising a cage polypeptide comprising:

(i) a structural region which comprises an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 13 (Cage 13), SEQ ID NO: 14 (Cage 14), SEQ ID NO: 15 (Cage 15), SEQ ID NO: 16 (Cage 16), SEQ ID NO: 17 (Cage 17), SEQ ID NO: 18 (Cage 18), SEQ ID NO: 1 (Cage 1), SEQ ID NO: 2 (Cage 2), SEQ ID NO: 3 (Cage 3), SEQ ID NO: 4 (Cage 4), SEQ ID NO: 5 (Cage 5), SEQ ID NO: 6 (Cage 6), SEQ ID NO: 7 (Cage 7), SEQ ID NO: 8 (Cage 8), SEQ ID NO: 9 (Cage 9), SEQ ID NO: 10 (Cage 10), SEQ ID NO: 11 (Cage 11), or SEQ ID NO: 12 (Cage 12), and

(ii) a latch region comprising a degron peptide comprising the amino acid sequence of CGL, wherein the latch region is capable of binding to a structural region.

91. The chimeric polypeptide of claim 90, wherein the structural region comprises any one of the amino acid sequences as set forth in SEQ ID NO: 13 (Cage 13); SEQ ID NO: 14 (Cage 14); SEQ ID NO: 15 (Cage 15); SEQ ID NO: 16 (Cage 16); SEQ ID NO: 17 (Cage 17); SEQ ID NO: 18 (Cage 18); SEQ ID NO: 1 (Cage 1); SEQ ID NO: 2 (Cage 2); SEQ ID NO: 3 (Cage 3); SEQ ID NO: 4 (Cage 4); SEQ ID NO: 5 (Cage 5); SEQ ID NO: 6 (Cage 6); SEQ ID NO: 7 (Cage 7); SEQ ID NO: 8 (Cage 8); SEQ ID NO: 9 (Cage 9); SEQ ID NO: 10 (Cage 10); SEQ ID NO: 11 (Cage 11); or SEQ ID NO: 12 (Cage 12).

92. The chimeric polypeptide of claim 90 or 91, wherein the degron peptide comprises YCGL (SEQ ID NO: 136), TYCGL (SEQ ID NO: 137), VTYCGL (SEQ ID NO: 138), RVTYCGL (SEQ ID NO: 139), IR VTYCGL (SEQ ID NO: 140), LIR VTYCGL (SEQ ID NO: 141), or VLIR VTYCGL (SEQ ID NO: 142).

93. The chimeric polypeptide of claim 90 or 91, wherein the degron peptide is linked to the C-terminus of the latch region of the cage polypeptide.

94. A chimeric polypeptide comprising an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 1 (Cage 1)^.

95. A chimeric polypeptide comprising an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 2 (Cage 2)·

96. A chimeric polypeptide comprising an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 3 (Cage

3)·

97. A chimeric polypeptide comprising an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 4 (Cage

4)·

98. A chimeric polypeptide comprising an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 5 (Cage

5)·

99. A chimeric polypeptide comprising an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 6 (Cage

6)·

100. A chimeric polypeptide comprising an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 7 (Cage 7).

101. A chimeric polypeptide comprising an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 8 (Cage 8).

102. A chimeric polypeptide comprising an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 9 (Cage 9).

103. A chimeric polypeptide comprising an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 10 (Cage 10).

104. A chimeric polypeptide comprising an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 11 (Cage 11).

105. A chimeric polypeptide comprising an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 12 (Cage 12).

106. A chimeric polypeptide comprising an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 13 (Cage 13).

107. A chimeric polypeptide comprising an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 14 (Cage 14).

108. A chimeric polypeptide comprising an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 15 (Cage 15).

109. A chimeric polypeptide comprising an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 16 (Cage 16).

110. A chimeric polypeptide comprising an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 17 (Cage 17).

111. A chimeric polypeptide comprising an amino acid sequence having at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or about 100% sequence identity to the amino acid sequence set forth in SEQ ID NO: 18 (Cage 18).

112. The chimeric polypeptide of any one of claims 88 to 111, which comprises a chimeric antigen receptor.

113. A cell comprising the polynucleotide of any one of claims 1 to 59, the polynucleotide set of any one of claims 60 to 79, the vector of any one of claims 80 to 87, or the chimeric polypeptide of any one of claims 88 to 112.

114. A cell genetically modified to express a CAR, comprising the polynucleotide of any one of claims 1 to 59, the polynucleotide set of any one of claims 60 to 79, the vector of any one of claims 80 to 87, or the chimeric polypeptide of any one of claims 88 to 112.

115. The cell of claim 113 or 114, wherein the cell is a T cell, a natural killer (NK) cell, a natural killer T (NKT) cell, or an ILC cell.

116. A composition comprising the polynucleotide of any one of claims 1 to 59, the polynucleotide set of any one of claims 60 to 79, the vector of any one of claims 80 to 87, the chimeric polypeptide of any one of claims 88 to 112, or the cell of any one of claims 113 to 115.

117. The composition of claim 116 for treating a subject in need of a CAR therapy.

118. A kit comprising the polynucleotide of any one of claims 1 to 59, the polynucleotide set of any one of claims 60 to 79, the vector of any one of claims 80 to 87, the chimeric polypeptide of any one of claims 88 to 112, or the cell of any one of claims 113 to 115.

119. A method of making an engineered cell comprising transfecting the polynucleotide of any one of claims 1 to 59, the polynucleotide set of any one of claims 60 to 79, or the vector of any one of claims 80 to 87 in a cell.

120. The method of claim 119, wherein the chimeric polypeptide is expressed in the cell.

121. The method of claim 120, further comprising administering the cell in a subject in need thereof.

122. The method of claim 121, further comprising administering a key polypeptide or an inducer that is capable of expressing a key polypeptide.

123. A method of controlling a T cell-mediated immune response in a subject in need thereof comprising administering an effective amount of the cell of any one of claims 113 to 115.

124. A method of stimulating a T cell-mediated immune response to a target cell population or tissue in a subject, comprising administering an effective amount of the cell of any one of claims 113 to 115 to the subject.

125. A method of providing an anti -tumor immunity in a subject in need thereof, the method comprising administering an effective amount of the cell of any one of claims 113 to 115 to the subject.

126. A method of treating cancer in a subject in need thereof comprising administering an effective amount of the cell of any one of claims 113 to 115 to the subject.

127. The method of claim 125 or 126, wherein the cell is a T cell.

128. The method of claim 127, wherein the cell is an autologous T cell.

129. The method of any one of claims 123 to 128, further comprising administering a key polypeptide.

130. The method of any one of claims 123 to 128, further comprising administering an inducer of a key polypeptide

131. Use of the polynucleotide of the polynucleotide of any one of claims 1 to 59, the polynucleotide set of any one of claims 60 to 79, the vector of any one of claims 80 to 87, the chimeric polypeptide of any one of claims 88 to 112, the cell of any one of claims 113 to 115, the composition of claim 116 or 117, or the kit of claim 118 for the manufacture of a medicament for treating cancer in a subject in need thereof.