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  • C07K16/28—Immunoglobulins [IG], e.g. monoclonal or polyclonal antibodies against material from animals or humans against receptors, cell surface antigens or cell surface determinants
  • C07K16/2851—Immunoglobulins [IG], e.g. monoclonal or polyclonal antibodies against material from animals or humans against receptors, cell surface antigens or cell surface determinants against the lectin superfamily, e.g. CD23, CD72
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  • C07K16/28—Immunoglobulins [IG], e.g. monoclonal or polyclonal antibodies against material from animals or humans against receptors, cell surface antigens or cell surface determinants
  • C07K16/2887—Immunoglobulins [IG], e.g. monoclonal or polyclonal antibodies against material from animals or humans against receptors, cell surface antigens or cell surface determinants against CD20
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  • A61K39/395—Antibodies; Immunoglobulins; Immune serum, e.g. antilymphocytic serum
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  • A61K39/39558—Antibodies; Immunoglobulins; Immune serum, e.g. antilymphocytic serum against materials from animals against tumor tissues, cells, antigens
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  • A61K40/4224—Molecules with a "CD" designation not provided for elsewhere
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  • C07K14/705—Receptors; Cell surface antigens; Cell surface determinants
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  • C07K14/705—Receptors; Cell surface antigens; Cell surface determinants
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  • C07K14/435—Peptides having more than 20 amino acids; Gastrins; Somatostatins; Melanotropins; Derivatives thereof from animals; from humans
  • C07K14/705—Receptors; Cell surface antigens; Cell surface determinants
  • C07K14/70546—Integrin superfamily
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  • C12N5/00—Undifferentiated human, animal or plant cells, e.g. cell lines; Tissues; Cultivation or maintenance thereof; Culture media therefor
  • C12N5/06—Animal cells or tissues; Human cells or tissues
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  • C12N5/0634—Cells from the blood or the immune system
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  • A61K2239/10—Indexing codes associated with cellular immunotherapy of group A61K40/00 characterized by the structure of the chimeric antigen receptor [CAR]
  • A61K2239/11—Antigen recognition domain
  • A61K2239/15—Non-antibody based
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  • A61K2239/38—Indexing codes associated with cellular immunotherapy of group A61K40/00 characterised by the dose, timing or administration schedule
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
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  • A61K2239/00—Indexing codes associated with cellular immunotherapy of group A61K40/00
  • A61K2239/39—Indexing codes associated with cellular immunotherapy of group A61K40/00 characterised by a specific adjuvant, e.g. cytokines or CpG
• • A—HUMAN NECESSITIES
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  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K2239/00—Indexing codes associated with cellular immunotherapy of group A61K40/00
  • A61K2239/46—Indexing codes associated with cellular immunotherapy of group A61K40/00 characterised by the cancer treated
  • A61K2239/48—Blood cells, e.g. leukemia or lymphoma
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  • C07K2317/00—Immunoglobulins specific features
  • C07K2317/60—Immunoglobulins specific features characterized by non-natural combinations of immunoglobulin fragments
  • C07K2317/62—Immunoglobulins specific features characterized by non-natural combinations of immunoglobulin fragments comprising only variable region components
  • C07K2317/622—Single chain antibody (scFv)
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  • C07K2317/00—Immunoglobulins specific features
  • C07K2317/70—Immunoglobulins specific features characterized by effect upon binding to a cell or to an antigen
  • C07K2317/73—Inducing cell death, e.g. apoptosis, necrosis or inhibition of cell proliferation
  • C07K2317/732—Antibody-dependent cellular cytotoxicity [ADCC]
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  • C07K2319/00—Fusion polypeptide
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  • C07K—PEPTIDES
  • C07K2319/00—Fusion polypeptide
  • C07K2319/01—Fusion polypeptide containing a localisation/targetting motif
  • C07K2319/03—Fusion polypeptide containing a localisation/targetting motif containing a transmembrane segment
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  • C07K2319/00—Fusion polypeptide
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  • C07K—PEPTIDES
  • C07K2319/00—Fusion polypeptide
  • C07K2319/70—Fusion polypeptide containing domain for protein-protein interaction
  • C07K2319/74—Fusion polypeptide containing domain for protein-protein interaction containing a fusion for binding to a cell surface receptor
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  • C12N2510/00—Genetically modified cells

Definitions

• the invention relates an A1-A2 domain of a non-natural NKG2D ligand that binds to non-natural NKG2D receptors and an antibody fusion protein comprising the domain.
• CARs chimeric antigen receptors
• the disclosure provides an antibody fusion protein comprising (i) heavy chains comprising variable region sequences comprising the amino acid sequence of SEQ ID NO: 1 and (ii) light chains comprising variable region sequences comprising the amino acid sequence of SEQ ID NO: 8, wherein the light chains are fused at the C-terminus to an A1-A2 domain comprising the amino acid sequence of SEQ ID NO: 11.
• the heavy chains comprise constant domains comprising the amino acid sequence of SEQ ID NO: 3.
• the A1-A2 domain is fused to the light chains via a linker comprising the amino acid sequence of SEQ ID NO: 10.
• the light chains in various aspects, comprise the amino acid sequence of SEQ ID NO: 13.
• the heavy chains comprising the amino acid sequence of SEQ ID NO: 7.
• the disclosure further provides a nucleic acid molecule comprising a nucleotide sequence encoding the light chain of the antibody fusion protein (e.g., a light chain comprising variable region sequence comprising the amino acid sequence of SEQ ID NO: 8, wherein the light chains are fused at the C-terminus to an A1-A2 domain comprising the amino acid sequence of SEQ ID NO: 11).
• a nucleotide sequence encoding the light chain of the antibody fusion protein e.g., a light chain comprising variable region sequence comprising the amino acid sequence of SEQ ID NO: 8, wherein the light chains are fused at the C-terminus to an A1-A2 domain comprising the amino acid sequence of SEQ ID NO: 11).
• the disclosure further provides a composition comprising the nucleic acid molecule encoding a light chain of the antibody fusion protein and a nucleic acid molecule comprising a nucleotide sequence encoding the heavy chain of the antibody fusion protein described herein (e.g., a heavy chain comprising a variable region sequence comprising the amino acid sequence of SEQ ID NO: 1).
• a composition comprising the nucleic acid molecule encoding a light chain of the antibody fusion protein and a nucleic acid molecule comprising a nucleotide sequence encoding the heavy chain of the antibody fusion protein described herein (e.g., a heavy chain comprising a variable region sequence comprising the amino acid sequence of SEQ ID NO: 1).
• an expression vector comprising the nucleic acid molecule encoding the light chain of the antibody fusion protein described herein, optionally further comprising a nucleic acid molecule comprising a nucleotide sequence encoding the heavy chain of the antibody fusion protein described herein
• the disclosure provides a host cell comprising a nucleic acid molecule comprising a nucleotide sequence encoding the light chain of the antibody fusion protein and a nucleic acid molecule comprising a nucleotide sequence encoding the heavy chain of the antibody fusion protein.
• a method of producing an antibody fusion protein is also provided, the method comprising culturing a host cell comprising a nucleic acid molecule comprising a nucleotide sequence encoding the light chain of the antibody fusion protein and a nucleic acid molecule comprising a nucleotide sequence encoding the heavy chain of the antibody fusion protein, and recovering the antibody fusion protein.
• kits comprising one or more containers comprising the antibody fusion protein described herein.
• the kit further comprises one or more containers comprising a mammalian cell (e.g., human lymphocyte or a human macrophage) comprising a chimeric antigen receptor comprising SEQ ID NO: 15.
• the chimeric antigen receptor further comprises SEQ ID NOs: 16-18.
• the disclosure further provides a method of treating a subject suffering from a CD20-positive cancer, the method comprising administering to the subject the antibody fusion protein described herein and a mammalian cell (e.g., human lymphocyte or a human macrophage) comprising a chimeric antigen receptor comprising SEQ ID NO: 15.
• a mammalian cell e.g., human lymphocyte or a human macrophage
• the chimeric antigen receptor further comprises SEQ ID NOs: 16-18.
• the disclosure also provides an A1-A2 domain peptide comprising an amino acid sequence having at least 95% identity to SEQ ID NO: 30, wherein the peptide comprises an alanine or glutamine one or more of positions 40, 54, and/or 84 of SEQ ID NO: 30.
• the peptide comprises glutamine residues at positions 40 and 54 of SEQ ID NO: 30.
• the peptide comprises a glutamine at position 84 of SEQ ID NO: 30 or an alanine at position 84 of SEQ ID NO: 30.
• Figure 1 is a chart providing various sequences described herein.
• FIG. 2A illustrates octet BLI kinetic binding data for His-tagged monomeric wild-type MIC ligand interaction with either wild-type NKG2D or iNKG2D.YA.
• Fc-wtNKG2D or Fc-iNKG2D.YA were captured with anti human IgG Fc capture (AHC) biosensor tips associated with a dilution series of each ligand (parenthetical value indicates highest concentration examined) after baseline establishment.
• ULBP4 could not be expressed and purified as a monomer so was not included in this assay. Note that all axes are to the same scale (Binding - 0 nm, 0.4 nm.
• FIG. 2B illustrates results from ELISA confirming inability of iNKG2D.YA to engage natural ligands.
• Ligand-Fc fusions R&D Biosystems
• a titration of biotinylated Fc- wtl ⁇ IKG2D (dashed lines) or Fc-iNKG2D.YA (solid lines) applied and detected by streptavidin-HRP.
• ELISA signal OD450
• nM Ligand Fc x-axis.
• Figures 3A-3D Orthogonal U2S3 ligand (A1-A2 domain) selective binding to NKG2D Y152A/199F (iNKG2D.AF) (an NKG2D ectodomain of the disclosure).
• Library design and phage panning performed was as described for iNKG2D.YA except that biotinylated double-mutant Fc-iNKG2D.AF was used during rounds of selection against increasing concentrations of Fc-wtNKG2D competitor.
• Data represents a single experiment (Figure 3A) Octet BLI binding data for interaction of monomeric ligands to either Fc-wtNKG2D or Fc-iNKG2D.AF. Data are representative of two experiments.
• Figure 3B Lead variants selected from the phage display library were cloned as fusions to the C-terminus of the Rituximab light chain and differential binding to Fc-wtNKG2D, Fc- iNKG2D.YA, and Fc-iNKG2D.AF and quantified by ELISA. Shown are four variants that selectively engage Fc- iNKG2D.YA and not the other two receptors. In the line graphs of Figure 3B, wtl ⁇ IKG2D is represented by diamonds, iNKG2D is represented by squares, and iNKG2D.AF is represented by triangles.
• FIG. 3C ELISA demonstrating exclusivity of U2S3 and U2R ligand binding to the receptor variant against which it was selected - Fc-iNKG2D.YA and Fc-iNKG2D.AF, respectively.
• U2S3 ligands are further described in, e.g., U.S. Patent Publication No. 2019/0300594, hereby incorporated by reference.
• Figure 3D Calcein release assay with Ramos target cells at an effector: target ratio (E:T) of 20:1 with either iNKG2D.YA-CAR or iNKG2D.AF-CAR expressing CD8+ T cells and a titration of Rituximab.LC-U2S3 or Rituximab. LC-U2R. Error bars represent ⁇ SD of technical replicates.
• Figure 4A Relative binding of selected phage to Fc-iNKG2D.YA and Fc-wtNKG2D after the third and fourth rounds of panning in the presence of increasing concentrations of wtNKG2D competitor. Phage clones in the portion of the graph outlined by the triangle were selected for further characterization.
• FIG. 4B Three phage variants - S1, S2, S3 - were expressed as fusions to the C-terminus of the anti-FGFR3 antibody clone R3Mab heavy chain as MicAbodies and, along with wild-type ULBP2 and R81W versions, were tested for the ability of the selective variants to retain preferential Fc-iNKG2D.YA binding (solid lines) over Fc-wtNKG2D (dashed lines). All purified MicAbodies retained binding to human FGFR3 (data not shown).
• Figure 4C Binding analysis of His-tagged monomeric wild-type ULBP2, ULBP2 R81 W, and the orthogonal U2S3 ligand binding to Fc-NKG2D and Fc-iNKG2D.YA.
• Fc-wtNKG2D or Fc-iNKG2D.YA were captured with anti-human IgG Fc capture (AHC) biosensor tips then associated with a dilution series of ligand. Data are from single experiments.
• FIG. 5 Octet BLI verification of U2S3 orthogonality when fused to the C-terminus of either the heavy or light chain of rituximab.
• Fc-wtNKG2D or Fc-iNKG2D.YA were captured with anti-human IgG Fc capture (AHC) biosensor tips then associated with a two-fold dilution series of MicAbody starting at 50 nM.
• the y-axes corresponding to binding responses were set to the same scale for all sensograms. Kd values could only be calculated for the two positive binding interactions are shown.
• Figure 6 Schematic of the iNKG2D.YA CAR receptor starting from the N-terminus of the polypeptide on the left and includes the signal sequence (SS) which is absent in the mature type I transmembrane protein.
• the underlined sequence corresponds to the signal sequence
• the italicized sequence corresponds to the iNKG2D domain (SEQ ID NO: 15)
• the plain sequence corresponds to the CD8a hinge/transmembrane domain (SEQ ID NO: 16)
• the underlined and italicized sequence corresponds to the 4-1 BB domain (SEQ ID NO: 17)
• the bolded sequence corresponds to the O ⁇ 3z domain (SEQ ID NO: 18)
• the double underlined sequence corresponds to the linker
• the dotted underlined sequence corresponds to the eGFP (green fluorescent protein) sequence.
• Figures 7A-7C Elements of the convertibleCAR system.
• Figure 7A Engineering overview to convert components of the NKG2D-MIC axis into the convertibleCAR system.
• iNKG2D.YA and U2S3 became the components of a second generation CAR receptor and bispecific adaptor molecule (MicAbody), respectively.
• TAA tumor-associated antigen.
• Figure 7B Representative example of high efficiency lentiviral transduction of the iNKG2D.YA-CAR into either CD4 or CD8 cells. Transduction efficiency varied between donors but >70% GFP+ yields were consistently achieved.
• the RITscFv-CAR is shown for comparison and has the same architecture as the iNKG2D-CAR except that a scFv based upon the VH/VL domains of Rituximab was used instead of iNKG2D.YA.
• Figure 7C Surface expression of iNKG2D.YA-CAR was determined in CD8+ T cells by incubating cells with Rituximab.
• Figures 8A-8C Ligand-dependent activation of iNKG2D-CAR expressing CD8+ T cells and MicAbody- dependent receptor internalization.
• Figure 8A CD8+ T cells were transduced with CAR constructs comprised of either wild-type NKG2D or iNKG2D.YA as the receptor domain. Wild-type His-tagged monomeric ligands or His- tagged monomeric U2S3 were coated onto the wells of a microtiter plate in a 1 :3 dilution series starting at 10 ug/mL.
• Figures 9A-9D In vitro characterization of convertibleCAR activity.
• Figure 9A Ramos (CD20+) target cells were exposed to convertibleCAR-CD8 cells at an E:T of 5:1 and co-cultured with increasing concentrations of Rituximab antibody (ADCC-deficient), Rituximab. LC-U2S3 MicAbody, or Trastuzumab.LC-U2S3 MicAbody. After 24 hours, supernatants were harvested and IL-2 (solid bars) or IFNy (hatched bars) quantified by ELISA.
• Rit-U2S3 were the only samples that demonstrated a cytokine release at 5000 pg/mL or more.
• Figures 10A-10C Comparison of heavy- vs. light-chain U2S3 fusions to Rituximab (ADCC-) antibody.
• Figure 10A Pharmacokinetics of serum Rituximab-U2S3 MicAbody levels after 100 ug IV administration in NSG mice in the absence of human T cells or tumor. All MicAbodies and antibody controls used were ADCC-deficient.
• the graph on the left is a comparison of parental antibody to the light-chain U2S3 fusion while the graph on the right is a comparison of parental antibody to the heavy-chain U2S3 fusion. All error bars are ⁇ SD of technical triplicates.
• FIG. 10B In vitro calcein release assay after two hours co-culture with iNKG2D-CAR CD8+ T cells and Ramos target cells at an E:T of 20:1 and titrations of Rituximab-MicAbodies. Error bars represent ⁇ SD for the experiment and data are representative of multiple experiments. The top line in the graph corresponds to Rituxumab.LC-U2S3, the middle line corresponds to Rituxumab.FIC-U2S3, and the bottom line corresponds to Rituximab.
• Figure 10C ELISA demonstrating binding of Rituximab. LC-U2S3 to mouse NKG2D. Shown are the A480 absorbance values. Trastuzumab.LC-Raelb, with a mouse wild-type Raelb ligand that binds naturally to mouse NKG2D, was included as a positive control.
• Figures 11 A-E Control of a disseminated Raji B cell lymphoma in NSG mice.
• Figures 12A-12C Control of subcutaneously implanted Raji tumors in NSG mice by convertibleCAR-T cells.
• Figure 12B Bar graph illustrating Serum Rit-S3 levels at 14, 21, and 45 days post-implant.
• Figures 13A-13F Targeted recruitment of complement factor C1q to iNKG2D.AF-CAR cells to direct their complement-mediated attrition.
• Figure 13A Structure of orthogonal ligand fusions to the Fc portion of human IgG expressed as either N- or C-terminal fusions. In addition to wild-type Fc, two sets of mutations in the CH2 domain that enhance C1q binding were independently explored - S267E/H268F/S324T/G236A/I332E (“EFTAE”) and K326A/E333A (“AA”).
• Figure 13B ELISA examining binding of human C1q to each purified fusion protein.
• Rank order of Kd's was EFTAE ⁇ AA ⁇ wt (0.12, 0.35, and 0.67 nM, respectively) regardless of orientation of fusions.
• Figures 13C and 13D Complement-dependent cytotoxicity (CDC) assays for C1q-binding enhance Fc-fusions.
• iNKG2D.AF-CAR or untransduced CD8+ T cells were incubated with a titration of each fusion molecule and 10% normal human serum complement for three hours before dead T cells were enumerated with SYTOX Red.
• Figures 14A-14E Targeted delivery of mutant-IL2 cytokine to iNKG2D-CAR CD8+ T cells.
• Figure 14A In vitro proliferation after three days of wtNKG2D-CAR (left bar) or iNKG2D.YA-CAR (right bar) treatment with 30 lUe/mL of cytokine or cytokine-U2S2 fusion. Darker shading is to highlight selectivity.
• FIG. 14B A low efficiency (45% GFP+) iNKG2D.YA-CAR transduction was cultured with 30 lUe/mL of non-selective (U2R81 W) or iNKG2D.YA-selective (U2S2) mutlL2 fusion and maintained for seven days. Cells were periodically examined by flow cytometry to quantify the %GFP+ cells in each population. Top lines correspond to U2S2-hFc-mutlL2 (square) and U2S2-mutlL2 (circles); bottom lines correspond to U2R80W-mutlL2 (circles) and U2R80W-hFc-mutlL2 (squares).
• iNKG2D-CAR CD8+ T cells were cultured with 30 lUe/mL of either wild-type IL-2 or U2S3-hFc-mutlL2 then co-cultured with Ramos cells at an E:T of 20:1 with increasing concentrations of Rituximab.LC-U2S3. Liberated calcein was quantified, and untransduced CD8+ cells were maintained in rhlL-2 served as a negative control.
• Figure 14D Untransduced (right bar) or iNKG2D-CAR CAR CD8+ T cells (left bar) were incubated with various cytokine molecules for three-days and proliferation quantified.
• Control molecules included a monomeric U2S3-hFc as well as Rit-S3 MicAbody. Parenthetical values are ILIe/mL concentrations tested. Data shown are an average of technical triplicates.
• Figures 15A-15B In vivo response of convertibleCAR-T cells to U2S3-hFc-mutlL2.
• FIG. 15B Plots for the expansion of CD8+ cells as well as the increase in proportion of GFP+ (CAR-expressing) cells upon U2S3-mutlL2 treatment.
• Upper cluster of lines corresponds to %GFP+ of CD8+ cells
• lower cluster of lines corresponds to %CD8+ in blood.
• Figure 16 Responsiveness of human PBMCs to U2S3-hFc-mutlL2. Fluman PBMCs from three donors were incubated with increasing concentrations of U2S3-hFc-mutlL2 or U2S3-hFc-wtlL2 for four days along with controls. Each of the labeled cell types was examined for the marker Ki-67 to quantify proliferative response under each condition.
• Eleven bars are shown for each of donor 1, 2, and 3; the bars represent, from left to right in each panel, untreated, anti-CD3 [2 ug/ml], IL-2 [300 lUe/ml], mutlL2 [30 lUe/ml], mutlL2 [300 lUe/ml], mutlL2 [3000 lUe/ml], mutlL2 [30000 lUe/ml], mutlL2 [30000 lUe/ml], wtlL2 [30 lUe/ml], wtlL2 [300 lUe/ml], wtlL2 [3000 lUe/ml], and wtlL2 [30000 lUe/ml], Error bars are ⁇ SD of triplicate measurements and data represents a single experiment.
• Figures 17A-17B illustrate a study evaluating MicAbodies having the A1-A2 domain attached at different locations and using different linkers.
• Figure 17A illustrates the constructs tested.
• Rit.FICd.S3 corresponds to Rituximab antibodies comprising a U2S3 A1-A2 domain, described in the Example fused to the heavy chains via a GGGS (SEQ ID NO: 14) linker.
• Rit.FICd.apts.S3 corresponds to Rituximab antibodies comprising a U2S3 A1-A2 domain fused to the heavy chains via a APTSSSGGGGS (SEQ ID NO: 10) linker.
• Rit.HCd.LC.S3 corresponds to Rituximab antibodies comprising a U2S3 A1-A2 domain fused to the light chains via a APTSSSGGGGS (SEQ ID NO: 10) linker.
• Rit.HCd.LC.gggs.S3 corresponds to Rituximab antibodies comprising a U2S3 A1-A2 domain fused to the light chains via a GGGS (SEQ ID NO: 14) linker.
• Figure 17B is a bar graph illustrating cytolysis (% max; y-axis) achieved using various concentrations of the MicAbodies in an in vitro calcein release assay after two hours co-culture with iNKG2D-CAR CD8+ T cells and Ramos target cells at an E:T of 20:1 and titrations of Rituximab-MicAbodies.
• % max of cytolysis is illustrated for 0 nM (first bar), 0.008 nM (second bar), 0.04 nM (third bar), 0.2 nM (fourth bar), 1 nM (fifth bar), and 5 nM (sixth bar) MicAbody.
• Rit.HCd.LC.S3 (comprising the A1-A2 domain on the light chains linked by the APTSSSGGGGS (SEQ ID NO: 10) linker) performed better than the version with the GGGS (SEQ ID NO: 14) linker and better than the constructs having the A1-A2 domain fused to the heavy chains, regardless of linker.
• Figure 18 is a line graph illustrating iNKG2D.YA capture using Rituximab fusion proteins comprising the A1-A2 domain of SEQ ID NO: 30 (U2S3) or SEQ ID NO: 11 (U2S3 (NQ)) fused to the light chain of the antibody.
• the A1-A2 domain with substitutions at positions 40 and 54 with respect to SEQ ID NO: 30 performed similarly to the A1-A2 domain of SEQ ID NO: 30.
• FIG 19 a line graph illustrating the reduced ability of Rituximab (“Rit”) fusion proteins comprising the A1-A2 domain of SEQ ID NO: 30 (U2S3) or SEQ ID NO: 11 (U2S3 (NQ)) fused to the light chain of the antibody to bind to wild-type NKG2D.
• Rituximab (“Rit”) fusion proteins comprising the A1-A2 domain of SEQ ID NO: 30 (U2S3) or SEQ ID NO: 11 (U2S3 (NQ)) fused to the light chain of the antibody to bind to wild-type NKG2D.
• it.P references Rituximab parental antibody, which was not fused to an A1-A2 domain.
• Rit.U2wt references Rituximab fused to wild-type ULBP2 domain, which is expected to bind wild-type NKG2D.
• Figure 20 is a bar graph illustrating cytolysis (% max; y-axis) achieved using various concentrations of MicAbodies in an in vitro calcein release assay after two hours co-culture with iNKG2D-CAR CD8+ T cells and Ramos target cells at an E:T of 20:1 and titrations of Rituximab-MicAbodies.
• % max of cytolysis is illustrated for 0 nM (first bar), 0.008 nM (second bar), 0.04 nM (third bar), 0.2 nM (fourth bar), 1 nM (fifth bar), and 5 nM (sixth bar) MicAbody.
• the instant disclosure provides a fusion protein comprising an antibody (or other antigen binding protein) and the A1-A2 domain of a non-natural NKG2D ligand.
• the non-natural NKG2D ligand selectively binds a non-natural NKG2D receptor.
• the fusion protein is used in connection with CAR-T cells displaying the non-natural NKG2D receptor to which the A1-A2 domain binds, thereby providing a powerful system for delivering a tailored CAR-T cell therapy which overcomes many of the disadvantages of current CAR-T cell based therapeutics.
• the fusion protein and system of the disclosure allows for flexible targeting to direct T cell activity to antigen of choice, multiplex capabilities to reduce the potential for antigen-loss related relapse, dose control for differential engagement of CAR-T cells, and selective delivery of modulatory agents to CAR-expressing cells.
• NKG2D is an activating receptor expressed as a type II homodimeric integral membrane protein on Natural Killer (NK) cells, some myeloid cells, and certain T cells.
• NK Natural Killer
• Fluman NKG2D has eight distinct natural MIC ligands (MICA, MICB, ULBP1 through ULBP6) that are upregulated on the surface of cells in response to a variety of stresses and their differential regulation provides the immune system a means of responding to a broad range of emergency cues with minimal collateral damage. Groh et al., Proc. Natl. Acad. Sci. U.S.A.
• the "A1-A2 domain” of the instant disclosure is not a naturally-occurring A1-A2 domain, but comprises an amino acid sequence which binds a mutated version of an NKG2D ectodomain and which does not bind wild-type NKG2D (wtNKG2D) (or at least does not bind wtl ⁇ IKG2D in such a manner to be biologically relevant in vivo).
• This orthogonal A1-A2 domain which is based on the U2S3 domain described in the Example (SEQ ID NO: 30) allows a unique glycosylation pattern with advantageous properties.
• the disclosure provides an A1-A2 domain peptide comprising an amino acid sequence having at least 95% identity to SEQ ID NO: 30 (e.g., at least 96% identity, at least 97% identity, at least 98% identity, at least 99% identity, or 100% identity to SEQ ID NO: 30), wherein the peptide comprises an alanine or glutamine one or more of positions 40, 54, and/or 84 of SEQ ID NO: 30.
• the A1-A2 domain may comprise a glutamine at position 40, an alanine at position 40, a glutamine at position 54, an alanine at position 54, an alanine at position 40 and a glutamine at position 54 (optionally with a glutamine or alanine at position 84), an alanine at position 40 and an alanine at position 54 (optionally with a glutamine or alanine at position 84), a glutamine at position 40 and an alanine at position 54 (optionally with a glutamine or alanine at position 84), a glutamine at position 40 and a glutamine at position 54 (optionally with a glutamine or alanine at position 84), an alanine at position 40 and a glutamine at position 84, an alanine at position 40 and an alanine at position 84, a glutamine at position 40 and an alanine at position 84, a glutamine at position 40 and an alanine at position 84, a
• the disclosure provides an A1-A2 domain peptide having at least 95% identity to SEQ ID NO: 30, wherein the peptide comprises glutamine residues at positions 40 and 54 with respect to the sequence of SEQ ID NO: 30.
• the A1-A2 domain comprises a glutamine at position 84 of SEQ ID NO: 30.
• the A1-A2 domain may, in various aspects, comprise an alanine at position 84 of SEQ ID NO: 30.
• the A1-A2 domain peptide comprises (or consists of) SEQ ID NO: 11, SEQ ID NO: 31, or SEQ ID NO: 32.
• any A1-A2 domain of the disclosure may be fused to a heavy chain or a light chain of an antibody (or other antigen binding protein) to generate, e.g., a bispecific fusion protein which binds both a target antigen and mutated NKG2D ectodomain.
• This format (antibodies fused to an A1-A2 domain) is also referred to as a "MicAbody.”
• the disclosure provides an antibody fusion protein comprising (i) heavy chains comprising variable region sequences of SEQ ID NO: 1 and (ii) light chains comprising variable region sequences of SEQ ID NO: 8.
• the light chains are fused at the C-terminus to an A1-A2 domain comprising the amino acid sequence of SEQ ID NO: 11.
• the heavy chain variable region and light chain variable region of the instant antibody fusion protein are those of Rituximab, a chimeric monoclonal antibody (lgG1 kappa immunoglobulin) that binds CD20, a surface antigen displayed on B cells.
• Rituximab is further described in, e.g., U.S. Patent Nos.
• B cells play a role in the pathogenesis of certain autoimmune diseases and cancers, and Rituximab is effective in targeting and killing B cells to achieve a beneficial effect in a variety of disorders.
• Rituximab has shown efficacy in treating cancers, such as leukemias (e.g., Hairy Cell Leukemia (HCL) and Chronic Lymphocytic Leukemia (CLL)) and lymphomas (e.g., Non-Hodgkins Lymphoma (NHL, such as Diffuse Large B-cell Lymphoma (DLBCL), Burkitt Lymphoma (BL), Mantel cell Lymphoma (MCL), and follicular lymphoma).
• HCL Hairy Cell Leukemia
• CLL Chronic Lymphocytic Leukemia
• NHL Non-Hodgkins Lymphoma
• DLBCL Diffuse Large B-cell Lymphoma
• BL Burkitt Lymphoma
• MCL Mantel cell Lymphoma
• Rituximab also demonstrated efficacy in treating autoimmune disorders, such as rheumatoid arthritis, multiple sclerosis, systemic lupus erythematosus (SLE), chronic inflammatory demyelinating polyneuropathy, and autoimmune-associated anemias.
• Rituximab also has been approved for the treatment of Granulomatosis with Polyangiitis (GPA) (Wegener's Granulomatosis) and Microscopic Polyangiitis (MPA).
• GPA Polyangiitis
• MPA Microscopic Polyangiitis
• the term "antibody” as used herein refers to immunoglobulins with full length heavy chains and light chains.
• the antibody of the disclosure is an IgG antibody, which includes four highly conserved subclasses (lgG1, lgG2, lgG3, and lgG4), which generally differ in their constant regions (e.g., in the hinge and/or CH2 domain).
• the antibody fusion protein of the disclosure comprises an lgG1 antibody, the constant region of which may be modified to reduce or inactivate the antibody's ability to trigger antibody-dependent cell cytolysis (ADCC) (e.g., by introducing D265A/D297A substitutions into the Fc domain).
• ADCC antibody-dependent cell cytolysis
• the heavy chains of the antibody fusion protein comprise constant domains comprising the amino acid sequence of SEQ ID NO: 3.
• the disclosure also contemplates antibody fusion proteins wherein the heavy chains comprise a constant region comprising the amino acid sequence of SEQ ID NO: 2.
• the disclosure also contemplates antibody fusion proteins wherein the heavy chains comprise an amino acid sequence at least 90% identical or at least 95% identical to SEQ ID NO: 3 but wherein the amino acids at positions 234, 235, and 329 within SEQ ID NO: 3 are alanine.
• the antibody fusion protein comprises heavy chains of SEQ ID NO: 7.
• the disclosure provides an antibody fusion protein comprising light chains of SEQ ID NO: 21 and heavy chains of SEQ ID NO: 7.
• the antibody fusion protein comprises heavy chains of SEQ ID NO: 6
• the disclosure contemplates an antibody fusion protein comprising light chains of SEQ ID NO: 21 and heavy chains of SEQ ID NO: 6.
• the light chains of the antibody comprise variable region sequences of SEQ ID NO: 8.
• the light chains comprise a constant region comprising the amino acid sequence of SEQ ID NO: 9 (or a sequence at least about 90% identical or 95% identical to SEQ ID NO: 9).
• the light chains of the antibody fusion protein of the disclosure comprise SEQ ID NO: 8 and SEQ ID NO: 9 (SEQ ID NO: 21).
• the light chains are optionally fused at the C-terminus to an NKG2D ligand A1-A2 domain comprising the amino acid sequence of SEQ ID NO: 11.
• A1-A2 domain comprising the amino acid sequence of SEQ ID NO: 11.
• fusion of the A1-A2 domain to the C terminus of the light chain amino acid sequence resulted in superior activity compared to fusion of the A1- A2 domain on the heavy chains of the antibody of the disclosure.
• the superior properties of the placement of the domain on the antibody fusion protein described herein could not have been predicted prior to the study described in the Example.
• the A1-A2 domain is fused to the C-terminus of a light chain via a linker, optionally a linker comprising (or consisting of) SEQ ID NO: 10.
• the linker of SEQ ID NO: 10 produced a MicAbody which unexpectedly outperformed other antibody fusion constructs in terms of B cell cytotoxicity.
• the antibody fusion protein of the disclosure comprises light chains comprising a variable region sequence of SEQ ID NO: 8 and the A1-A2 domain of SEQ ID NO: 11 fused to the C-terminus of the light chain via a linker sequence of SEQ ID NO: 10, optionally comprising the light chain constant region of SEQ ID NO: 9.
• the light chains of the antibody fusion protein comprise the amino acid sequence of SEQ ID NO: 13.
• the disclosure provides an antibody fusion protein comprising light chains of SEQ ID NO: 13 and heavy chains of SEQ ID NO: 7.
• the disclosure also provides an antibody fusion protein comprising light chains of SEQ ID NO: 13 and heavy chains of SEQ ID NO: 6.
• the disclosure also provides a kit comprising one or more containers comprising the antibody fusion protein described herein.
• the kit may further comprise instructions and written information on indications and usage of the antibody fusion protein.
• Syringes e.g., single use or pre-filled syringes, sterile sealed containers, e.g. vials, bottle, vessel, and/or kits or packages comprising the antibody fusion protein, optionally with suitable instructions for use, are also contemplated.
• the disclosure provides an article of manufacture, or unit dose form, comprising: (a) a composition of matter comprising the antibody fusion protein described herein; (b) a container containing said composition; and (c) a label affixed to said container, or a package insert included in said container referring to the use of said antibody fusion protein in the treatment of a disease or disorder (e.g., cancer).
• compositions comprising the antibody fusion protein (and, in various aspects, mammalian cells expressing a CAR as described herein) and a pharmaceutically acceptable carrier, excipient or diluent.
• the composition is a sterile composition.
• the disclosure further provides a system or kit comprising components of a cell therapy regimen targeting CD20-displaying cells.
• the first component is the antibody fusion protein described herein, i.e., a bispecific, antibody-based fusion protein that binds both CD20 and a CAR comprising an NKG2D ectodomain.
• the second component is a mammalian cell (e.g., human cell) that is genetically modified to express a chimeric antigen receptor (CAR) that is itself inert (i.e., unarmed CAR-T).
• CAR chimeric antigen receptor
• the mammalian cell is a lymphocyte or a macrophage, e.g., a human lymphocyte (such as human T cell) or a human macrophage.
• the second component is a human NK (natural killer) cell (e.g., an autologous human NK cell); disclosure herein with reference to T cells also applies to NK cells.
• the kit comprises one or more containers comprising mammalian cells expressing the CAR and one or more containers comprising the antibody fusion protein.
• a kit may further comprise instructions and written information on indications and usage of the components described herein.
• CAR Chimeric antigen receptor
• a CAR refers to an artificial immune cell receptor that is engineered to recognize and bind to an antigen expressed by a target cell, such as a tumor cell.
• a CAR is designed for a T cell and is a chimera of a signaling domain of the T cell receptor (TOR) complex and an antigen recognizing domain (e.g., a single chain fragment (scFv) of an antibody or other antibody fragment).
• TOR T cell receptor
• scFv single chain fragment
• T cells and NK-cells can be modified using gene transfer techniques to directly and stably express on their surface transmembrane signaling receptors that confer novel antigen specificities.
• “Third generation” CARs contain two costimulatory domains fused with the TCR CD3zeta chain.
• Third generation costimulatory domains may include, e.g., a combination of CD3zeta, CD27, CD28, 4-1 BB, ICOS, or 0X40.
• CARs so constructed can trigger, e.g., T cell activation upon binding the targeted antigen in a manner similar to an endogenous T cell receptor, but independent of the major histocompatibility complex (MHO).
• MHO major histocompatibility complex
• the chimeric antigen receptor of the disclosure comprises, as the "antigen binding domain” of the CAR, a mutated NKG2D ectodomain that is incapable of engaging natural ligands. Mutation of the NKG2D ectodomain is further described in, e.g., Culpepper et al., Mol. Immunol. 48, 516-523 (2011) and the Example.
• the mutated NKG2D is referred to herein as "iNKG2D.”
• the iNKG2D domain comprises the amino acid sequence of SEC ID NO: 15.
• the ectodomain is preferably associated with a transmembrane domain, an intracellular domain of a costimulatory molecule (e.g., 4-1 BB or CD28), and/or a T cell receptor intracellular signaling domain.
• a costimulatory molecule e.g., 4-1 BB or CD28
• a T cell receptor intracellular signaling domain e.g., 4-1 BB or CD28
• the iNKG2D ectodomain is fused to a CD8a hinge/transmembrane domain (e.g., comprising or consisting of the sequence of SEC ID NO: 16), a 4-1 BB domain (e.g., comprising or consisting of the sequence of SEC ID NO: 17), and/or a O ⁇ 3z domain (e.g., comprising or consisting of the sequence of SEC ID NO: 18).
• the CAR comprises all of these components (e.g., SEC ID NOs: 15-18 or SEC ID NO: 19
• the CAR is inert, the CAR can only form a productive immunologic synapse with a target cell displaying the antigen and activate cytolysis when it is "armed” with its cognate antibody fusion protein noncovalently bound to its receptor.
• the CAR-expressing cell is referred to herein as "convertibleCAR.”
• An example of the system is illustrated in Figure 7A.
• the antibody fusion protein described herein is capable of activating iNKG2D-CAR-expressing cells (e.g., T cells) only in the presence of cells expressing CD20.
• convertibleCAR-T cells When used with additional MicAbodies that target other antigens (i.e., antibody fusion proteins having different variable regions that bind different cell surface antigens), convertibleCAR-T cells can be targeted to different antigens simultaneously or sequentially to mediate cytolysis; this approach can help address, e.g., tumor resistance and escape as a result of target antigen loss without having to create, expand and infuse multiple different autologous CAR cells.
• This highly modular convertibleCAR system expands the potential of adoptive cell therapies and overcomes many of disadvantages of existing cell therapies, including severe systemic toxicity, antigen escape, and limited and uncontrolled persistence of current CAR-T and CAR-NK cell therapeutics.
• a CAR cellular therapy may be an immunotherapy utilizing a subject or a patient's own immune cells that are engineered to be able to produce a particular CAR(s) on their surface.
• cells e.g., T cells
• the cells are then genetically engineered to produce a particular chimeric antigen receptor on their surface.
• the CAR-expressing cells are expanded by growth in a laboratory and then administered to the subject or patient, or another subject or patient.
• the CAR-expressing cells will recognize and kill cells (e.g., cancer cells) that express the targeted antigen on their surface.
• the cells may be isolated from the subject which will be recipient of the therapy, or may be isolated from a donor subject that is not ultimate recipient of the therapy.
• the cells are autologous CD4+ and CD8+ T cells.
• the disclosure further provides a method of treating a subject for a disease or disorder associated with cells expressing CD20, such as cancer (CD20-positive cancers).
• the method comprises administering to the subject the CAR-expressing cell described herein (e.g., a T cell or NK cell expressing the iNKG2D-based CAR described herein) and administering to the subject the antibody fusion protein described herein.
• the CAR-expressing cell described herein e.g., a T cell or NK cell expressing the iNKG2D-based CAR described herein
• cancers include, but are not limited to, leukemias and lymphomas, such as Hairy Cell Leukemia, Chronic Lymphocytic Leukemia, and Non-Hodgkins Lymphoma (e.g., Diffuse Large B-cell Lymphoma, Burkitt Lymphoma, Mantel cell Lymphoma, and follicular lymphoma).
• leukemias and lymphomas such as Hairy Cell Leukemia, Chronic Lymphocytic Leukemia, and Non-Hodgkins Lymphoma (e.g., Diffuse Large B-cell Lymphoma, Burkitt Lymphoma, Mantel cell Lymphoma, and follicular lymphoma).
• the term "treat,” as well as words related thereto, do not necessarily imply 100% or complete treatment or remission. Rather, there are varying degrees of treatment of which one of ordinary skill in the art recognizes as having a potential benefit or therapeutic effect.
• the methods of treating a disease or disorder can provide any amount or any level of treatment.
• the treatment provided by the method may include treatment of one or more conditions or symptoms or signs of the disease being treated.
• the treatment method of the present disclosure may inhibit one or more symptoms of the disease.
• the treatment provided by the methods of the present disclosure may encompass slowing the progression of the disease.
• Treatment for cancer may be determined by any of a number of ways. Any improvement in the subject's wellbeing is contemplated (e.g., at least or about a 10% reduction, at least or about a 20% reduction, at least or about a 30% reduction, at least or about a 40% reduction, at least or about a 50% reduction, at least or about a 60% reduction, at least or about a 70% reduction, at least or about an 80% reduction, at least or about a 90% reduction, or at least or about a 95% reduction of any parameter described herein).
• Any improvement in the subject's wellbeing is contemplated (e.g., at least or about a 10% reduction, at least or about a 20% reduction, at least or about a 30% reduction, at least or about a 40% reduction, at least or about a 50% reduction, at least or about a 60% reduction, at least or about a 70% reduction, at least or about an 80% reduction, at least or about a 90% reduction, or at least or about a 95% reduction of any parameter described herein).
• a therapeutic response would refer to one or more of the following improvements in the disease: (1) a reduction in the number of neoplastic cells; (2) an increase in neoplastic cell death; (3) inhibition of neoplastic cell survival; (5) inhibition (i.e., slowing to some extent, preferably halting) of tumor growth or appearance of new lesions; (6) decrease in tumor size or burden; (7) absence of clinically detectable disease, (8) decrease in levels of cancer markers; (9) an increased patient survival rate; and/or (10) some relief from one or more symptoms associated with the disease or condition (e.g., pain).
• treatment efficacy also can be characterized in terms of responsiveness to other immunotherapy treatment or chemotherapy.
• the methods of the disclosure further comprise monitoring treatment in the subject.
• the subject is a mammal, including, but not limited to, mammals of the order Rodentia, such as mice and hamsters, and mammals of the order Logomorpha, such as rabbits, mammals from the order Carnivora, including Felines (cats) and Canines (dogs), mammals from the order Artiodactyla, including Bovines (cows) and Swines (pigs) or of the order Perssodactyla, including Equines (horses).
• the mammal is of the order Primate, Ceboid, or Simoid (monkey) or of the order Anthropoid (humans and apes).
• the mammal is a human.
• compositions may be delivered to a subject using any of a variety of routes, including parenteral, topical, oral, intrathecal or local administration. Indeed, a composition may be administered subcutaneously, intracutaneously, intradermally, intravenously, intraarterially, intratumorally, parenterally, intraperitoneally, intramuscularly, intraocularly, intraosteally, epidurally, intradurally, intratumorally and the like.
• the disclosure also provides (i) nucleic acid molecules (i.e., isolated nucleic acids) encoding the light chain of the antibody fusion protein described herein and (ii) nucleic acid molecules (i.e., isolated nucleic acids) encoding the heavy chain of the antibody fusion protein described herein, as well as compositions comprising (i) and/or (ii).
• the disclosure further provides nucleic acid molecules encoding any of the A1-A2 domain peptides disclosed herein.
• Nucleic acids of the disclosure include nucleic acids encoding any of the amino acid sequences disclosed herein, as well as nucleic acids comprising nucleotide sequences having at least 80%, more preferably at least about 90%, more preferably at least about 95%, and most preferably at least about 98% identity to nucleic acids of the disclosure (i.e., the nucleic acid sequences set forth in the sequence listing).
• Nucleic acids of the disclosure include nucleic acids encoding any of the amino acid sequences disclosed herein, as well as nucleic acids encoding amino acid sequences having at least 80%, more preferably at least about 90%, more preferably at least about 95%, and most preferably at least about 98% identity to the amino acid sequences of the disclosure (i.e., the amino sequences set forth in the sequence listing). Nucleic acids of the disclosure also include complementary nucleic acids. In some instances, the sequences will be fully complementary (no mismatches) when aligned. In other instances, there may be up to about a 20% mismatch in the sequences. The disclosure provides nucleic acid molecules comprising nucleic acid sequences encoding both a heavy chain and a light chain of an antibody fusion protein of the disclosure.
• Nucleic acids of the disclosure can be cloned into an expression vector, such as a plasmid, cosmid, bacmid, phage, artificial chromosome (BAC, YAC) or virus, into which another genetic sequence or element (either DNA or RNA) may be inserted so as to bring about the replication of the attached sequence or element.
• an expression vector such as a plasmid, cosmid, bacmid, phage, artificial chromosome (BAC, YAC) or virus, into which another genetic sequence or element (either DNA or RNA) may be inserted so as to bring about the replication of the attached sequence or element.
• the expression vector contains a constitutively active promoter segment (such as but not limited to CMV, SV40, Elongation Factor or LTR sequences) or an inducible promoter sequence such as the steroid inducible pIND vector (Invitrogen), where the expression of the nucleic acid can be regulated.
• Expression vectors of the disclosure may further comprise regulatory sequences, for example, an internal ribosomal entry site.
• a secretory signal peptide sequence can also, optionally, be encoded by the expression vector, operably linked to the coding sequence of interest, so that the expressed polypeptide can be secreted by the recombinant host cell, for more facile isolation of the polypeptide of interest from the cell.
• the expression vector can be introduced into a cell by transfection, for example.
• Recombinant host cells comprising the nucleic acid molecules (optionally contained in expression vectors) also are provided.
• the recombinant host cell may be a prokaryotic cell, for example an E. coli cell, or a eukaryotic cell, for example a mammalian cell or a yeast cell.
• Yeast cells include, e.g., Saccharomyces cerevisiae, Schizosaccharomyces pombe, and Pichia pastoris cells.
• Mammalian cells include, for example, VERO, HeLa, Chinese hamster Ovary (CHO), W138, baby hamster kidney (BHK), COS-7, MDCK, human embryonic kidney line 293, African green monkey kidney cells, and COS cells.
• Recombinant protein-producing cells of the disclosure also include any insect expression cell line known, such as for example, Spodoptera frugiperda cells.
• the cells are mammalian cells, such as CHO cells.
• a method of producing an antibody fusion protein further is provided by the disclosure.
• the method comprises culturing a host cell (an isolated host cell) comprising a nucleic acid molecule comprising a nucleotide sequence encoding the light chain of the antibody fusion protein and a nucleic acid molecule comprising a nucleotide sequence encoding the heavy chain of the antibody fusion protein.
• the method further comprises recovering the antibody fusion protein.
• the disclosure also provides a method of producing an A1-A2 domain peptide described herein.
• the method comprises culturing a host cell (an isolated host cell) comprising a nucleic acid molecule comprising a nucleotide sequence encoding the A1-A2 domain peptide.
• the method further comprises recovering the domain peptide (which is optionally fused to another peptide).
• Culture conditions and methods for generating recombinant proteins, such as antibody proteins, are known in the art.
• protein purification methods are known in the art and utilized herein for recovery of recombinant proteins from cell culture media.
• methods for protein and antibody purification include filtration, affinity column chromatography, cation exchange chromatography, anion exchange chromatography, and concentration.
• the method comprises formulating the antibody fusion protein or A1-A2 domain peptide.
• anti-CD20 antibodies as the fusion partner to an A1-A2 domain peptide
• the A1-A2 domain peptide of the disclosure may be fused to other peptides, including other antigen binding peptides, such as other antibodies.
• the disclosure above with respect to the structure of anti-CD20 antibodies also applies to other antigen binding proteins and antibodies (i.e., antibodies that bind other targets).
• the antibody may be a monoclonal antibody or multispecific antibody (e.g., bispecific antibody).
• the A1-A2 domain peptide may be fused to an antigen binding fragment of an antibody.
• antibody fragments include Fab, Fab', F(ab')2, and Fv fragments.
• Other antigen binding proteins include diabodies, linear antibodies, single-chain antibody molecules, and the like.
• the antigen binding protein may target any suitable antigen, such as antigens expressed on the surface of cancer cells.
• antigens include, but are not limited to CD19, BMCA, HER2, EGFR, EpCAM, CEA, BCMA, PSMA, CD19, CD20, CD22, CD33, CD37, CD38, CD123, CD276 (B7-H3), GPC2, GPC3, GPRC5D, WT-1, NY-ESO-1, CLDN4,
• the disclosure further provides a method of treating a subject for a disease or disorder (e.g., cancer).
• the method comprises administering to the subject the CAR-expressing cell described herein (e.g., a T cell or NK cell expressing the iNKG2D-based CAR described herein) and administering to the subject an antigen-binding fusion protein comprising the A1-A2 domain peptide described herein. Examples of cancers, etc., are discussed above and apply to this aspect of the disclosure.
• This Example describes exemplary methods of producing an antibody fusion protein of the disclosure and NKG2D ectodomain-comprising CAR-T cells.
• the Example further demonstrates the ability of an antibody fusion protein comprising the variable region sequences from Rituximab and comprising an A1-A2 domain fused to the C-terminus of the light chain to selectively bind a CAR-T cell comprising the amino acid sequences of SEQ ID NOs: 15-18, and the ability of the antibody fusion protein and CAR-T cell combination to kill CD20-bearing cancer cells in vivo.
• DNA constructs for Fc-NKG2D molecules were expressed in Expi293TM cells (Thermo Fisher Scientific) and dimeric secreted protein was purified by Protein A affinity chromatography (PierceTM #20334, Thermo Fisher). Eluted material was characterized and further purified by size-exclusion chromatography (SEC) on an AKTA Pure system using Superdex 200 columns (GE Life Sciences). Correctly assembled, size-appropriate monomeric material was fractionated into phosphate-buffered saline (PBS).
• PBS phosphate-buffered saline
• the A1-A2 domains of human MICA*001 (UniProtKB Q29983, residues 24-205), MICB (UniProtKB Q29980.1, 24-205), ULBP1 (UniProtKB Q9BZM6, 29-212), ULBP2 (UniProtKB Q9BZM5, 29-212), ULBP3 (UniProtKB Q9BZM4, 30-212), ULBP5 (NCBI accession NP_001001788.2, 29-212), and ULBP6 (UniProtKB, 29- 212) were cloned with a C-terminal 6x-His tag.
• Monomeric protein was purified from Expi293TM supernatants Ni-NTA resin (HisPurTM, Thermo Fisher) and eluted material exchanged into PBS with Sephadex G-25 in PD-10 Desalting Columns (GE Life Sciences).
• MIC ligands and orthogonal variants were cloned by ligation-independent assembly (HiFi DNA Assembly Master Mix, NEB #E2621) as fusions to the C-terminus of either the kappa light-chain or the heavy- chain of human lgG1 antibodies via either an APTSSSGGGGS or GGGS linker, respectively. Additionally, D265A/N297A (Kabat numbering) mutations were introduced into the CH2 domain of the heavy chain of all antibody and MicAbody clones to eliminate antibody-dependent cell cytotoxicity (ADCC) function.
• ADCC antibody-dependent cell cytotoxicity
• Heavy- and light-chain plasmid DNAs in the mammalian expression vector pD2610-V12 (ATUM)) for a given antibody clone were co-transfected into Expi293TM cells and purified by Protein A.
• the appropriate VL or VH domains were swapped into either the kappa light-chain or an ADCC- deficient lgG1 heavy-chain.
• ELISA enzyme-linked immunosorbent assay binding assays were performed with MICA-Fc, MICB-Fc, ULBP1- Fc, ULBP2-FC, ULBP3-Fc, or ULBP4-Fc (R&D Systems) coated onto microtiter plates, a titration of biotinylated Fc-wtNKG2D or Fc-iNKG2D.YA, detected with streptavidin-HRP (R&D Systems #DY998), and developed with 1- Step Ultra TMB ELISA (Thermo Fisher #34208).
• Phage display was employed to identify orthogonal ULBP2 A1-A2 variants that exhibited exclusive binding to either iNKG2D.YA or iNKG2D.AF.
• DNA libraries were generated targeting the codons of helix 2 (residues 74-78, numbering based upon mature protein) or helix 4 (residues 156-160) that in the bound state are positioned in close proximity to the Y152 positions on the natural NKG2D receptor45.
• A1-A2 phage libraries were captured with either biotinylated Fc-iNKG2D.YA or Fc-iNKG2D.AF protein (EZ-LinkTM NHS- Biotin Kit, Thermo Fisher #20217) and enriched by cycling through four rounds of selection with increasing concentrations of non-biotinylated Fc-wtNKG2D competitor.
• Phage variants were sequenced then cloned as human lgG1 monoclonal antibody fusions for additional validation.
• ELISA wells were coated with 1 mg/mL Fc-wtNKG2D, Fc-iNKG2D.YA, or Fc-iNKG2D.AF, and bound MicAbody was detected with an HRP-conjugated mouse-anti-human kappa chain antibody (Abeam #ab79115). Affinity of both monomeric and antibody-fused ULBP2 variants was also determined by Octet analysis as described above.
• the VH and VL domains of Rituximab separated by a (GGGGS)3 linker were substituted for the NKG2D module to generate the rituximab scFv-based CAR (RITscFv-CAR).
• GGGGS rituximab scFv-based CAR
• 6x10 6 Lenti-X 293T (Takara Bio #632180) cells were seeded in a 10 cm dish the day prior to transfection.
• a Fluman Peripheral Blood Leuko Pak (Stemcell Technologies #70500.1) from an anonymous donor was diluted with an equivalent volume of PBS +2% FBS, then centrifuged at 500 x g for 10 minutes at room temperature. Cells were resuspended at 5x10 7 cells/ml in PBS + 2% FBS and CD4+ or CD8+ cells enriched by negative selection (Stemcell EasySepTM Fluman CD4 T Cell Isolation Kit #17952 or EasySep Fluman CD8 T Cell Isolation Kit #17953) by addition of 50 mI of isolation cocktail per ml of cells and incubating for five minutes at room temperature.
• RapidSpheresTM were added per ml of cells and samples topped off (to each 21 mL cells, 14 mL of PBS). Cells were isolated for 10 minutes with an EasySEPTM magnet followed by removal of buffer while maintaining the magnetic field. Enriched cells were transferred into new tubes with fresh buffer and the magnet reapplied for a second round of enrichment after which cells were resuspended, counted, and cryopreserved at 10-15x10 6 cells/cryovial (RPMI-1640,
• Corning #15-040-CV 20% human AB serum, Valley Biomedical #HP1022; 10% DMSO, Alfa Aesar #42780).
• TCM T cell medium
• TexMACS medium Miltenyi 130-097-196; 5% human AB serum, Valley Biomedical #HP1022;
• lentiviral particles 50 mI_
• lentiviral particles 50 mI_
• TCM T25 flasks
• Dynabeads were removed (MagCellect magnet, R&D Systems MAG997), transduction efficiency assessed by flow cytometry for GFP, back-diluted to 5x10 5 cells/mL, and cell density monitored daily to ensure they did not exceed 4x10 6 cells/ml.
• iNKG2D When necessary, surface expression of iNKG2D was correlated with GFP expression using a MicAbody and detecting with PE-anti-human kappa chain (Abeam #ab79113) or by directly conjugating the Rituximab-MicAbody to Alexa Fluor 647 (Alexa Fluor Protein Labeling Kit #A20173, Thermo Fisher).
• Alexa Fluor 647 Alexa Fluor Protein Labeling Kit #A20173, Thermo Fisher.
• the amount of iNKG2D expression on the surface of convertible CAR-CD8 cells was quantified using Alexa Fluor 647 conjugated Rituximab-MicAbody, and median fluorescence intensity was correlated with QuantumTM MESF 647 beads (Bangs Laboratories #647). All flow cytometry was performed on either Bio-Rad S3e Cell Sorter or Miltenyi MACSQuant Analyzer 10 instruments.
• tumor cells were centrifuged and resuspend in 4 mM probenecid (MP Biomedicals #156370) +25 mM calcein-AM (Thermo Fisher #C1430) in T cell medium at 1-2x10 6 cells/ml for one hour at 37°C, washed once, and adjusted to 8x10 5 cells/ml.
• CD8+ CAR-T cells were pelleted and resuspended in 4 mM probenecid with 60 lUe/ml IL-2 in TCM at 4x10 6 cells/mL then adjusted according to the desired effectontarget ratio (unadjusted for transduction efficiency).
• 25 m ⁇ target cells were plated followed by 25 m ⁇ medium or diluted MicAbody. Then 100 m ⁇ medium (minimum lysis), medium +3% Triton-X 100 (maximum lysis), or CAR-T cells were added and plates incubated at 37°C for two hours. Cells were pelleted and 75 m ⁇ supernatant transferred to black clear-bottom plates and fluorescence (excitation 485 nm, emission cutoff 495 nm, emission 530 nm, 6 flashes per read) acquired on a Spectramax M2e plate reader (Molecular Devices).
• T cells were pre-incubated at 37°C with either saturating (5 nM) or a titration of MicAbody for 30 minutes before washing to remove unbound MicAbody and co-culturing with calcein-loaded target cells.
• miceAbody binding curve data were generated by ProMab Biotechnologies, Inc. (Richmond, CA).
• 3x10 5 convertibleCAR-CD8+ cells were plated in 96-wells V-bottom plates and incubated with labeled Alexa Fluor 647 labeled Rituximab.LC-U2S3 MicAbody for 30 minutes at room temperature in a final volume of 100 m ⁇ RPMI + 1% FBS with a titration curve starting at 200 nM. Cells were then rinsed and median fluorescence intensity determined for each titration point by flow cytometry.
• mice or control antibody was by the intraperitoneal (IP) route unless otherwise specified, and in vivo imaging for bioluminescence was performed with a Xenogen MS system (Perkin Elmer). Animals were bled regularly to monitor human T cell dynamics by flow cytometry, staining with APC Anti-Human CD3 (clone OKT3, #20-0037-T 100, Tonbo Biosciences), monitoring GFP, and examining cell-associated MicAbody levels with biotinylated Anti-Human F(ab')2 (#109-066-097, Jackson ImmunoResearch Laboratories Inc.) followed by Streptavidin-PE detection (BD #554061). Serum ELISAs to monitor MicAbody levels was performed as described above.
• Complement-mediated ablation ofiNKG2D.AF-CAR cells To generate Fc reagents with enhanced complement binding and targeted delivery to the T cells expressing iNKG2D.AF, the orthogonal ligand was cloned as a fusion to either the N- (U2R-Fc) or C-terminus (Fc-U2R) of human lgG1 Fc via a GGGS linker with the Fc including the hinge, CH2, and CH3 domains.
• Confirmatory ELISAs were performed by capturing with Fc-NKG2D.AF followed by binding U2R/Fc-variant fusions at 1 m9/h ⁇ concentration, titrating in human-C1q protein (Abeam #ab96363), then detecting with polyclonal sheep-anti-C1q-HRP antibody (Abeam #ab46191).
• Complement-dependent cytotoxicity (CDC) assays were performed by iQ Biosciences (Berkeley, CA).
• U2S3 was fused to the N-terminus of the Fc-hinge of one chain with K392D/K409D (Kabat numbering) mutations while the mutlL2 was fused to the C-terminus of the second Fc-chain which harbored E356K/D399K mutations. Additionally, D265A/N297A mutations were introduced in both Fc chains to render the Fc ADCC-deficient. Expression in Expi293T cells and purification was as described above. Appropriately assembled U2S3-hFc-mutlL2 material was fractionated by SEC and the presence of individual size-appropriate polypeptides was confirmed by denaturing SDS-PAGE.
• CAR-T cell proliferation in response to various cytokines or U2S3-cytokine fusions was quantified with the WST-1 Cell Proliferation Reagent (Millipore Sigma #5015944001). Briefly, CAR-T cells were pelleted and resuspended in T cell media without IL-2, dispensed into 96-well plates at 4x10 4 cells/well, and the appropriate amount of diluted U2S3-cytokine fusions was added to achieve 30 ILIe/mL or higher concentration as needed in a final assay volume of 100 m ⁇ per well. Recombinant-human IL2 and IL15 (Peprotech #200-02 and #200-15) were included as controls.
• bleCAR-CD8 T cells were fixed at 0, 30, 60, and 120 minutes after exposure to cytokines or U2S3-hFc-cytokine fusions then stained.
• Human PBMC stimulation and immune-phenotyping studies were performed. Briefly, normal PBMCs from three donors were seeded in 96-well plates at 1x10 5 cells/well and exposed to a 10-fold dilution series of either U2S3-hFc-mutlL2 or U2S3-hFc-wtlL2 (wild-type IL2) for four days at 37°C with 5% CO2.
• the ULBP2 A1 A2 domain was chosen for phage display-based selection of mutants with high affinity binding to each of the iNKG2D variants since it is not polymorphic. NNK libraries interrogating helix 2 and helix 4 returned only helix 4 variants and even then only in the context of a spontaneous R81 W mutation, which likely has a stabilizing role on the ULBP2 A1 A2 domain.
• iNKG2D. YA as a chimeric antigen receptor.
• Lentiviral transduction of iNKG2D.YA fused to 4-1 BB, O ⁇ 3z, and eGFP into primary human T cells efficiently generated convertibleCAR-T cells with robust transgene expression on par with a rituximab-scFv based CAR construct (RITscFv-CAR) with the same hinge, transmembrane, and intracellular architecture ( Figure 2b and Figure 6).
• bleCAR-CD8+ cells to microtiter plates coated with wild-type or U2S3 ligands resulted in activation and liberation of IL-2 and IFNy only with U2S3 while wtNKG2D-CAR bearing cells responded only to wild-type ligands confirming the selectivity of the orthogonal interaction in the context of T cells (Figure 8A).
• activation of convert! bleCAR-T cell function was dependent upon the presence of the appropriate cognate ULBP2 variant.
• the iNKG2D.YA expressing or iNKG2D.AF expressing T cells only lysed Ramos (CD20+) target cells when armed with a MicAbody bearing its respective orthogonal ligand, i.e.
• convertibleCAR-CD8+ cells were armed with Rituximab. LC-U2S3, Trastuzumb.LC-U2S3 (targeting Her2), or an equimolar mixture of the two MicAbodies and exposed to either Ramos cells or CT26- Her2.
• CAR cells armed with a single MicAbody directed lysis to only tumor cells expressing the cognate antigen
• dual-armed CARs targeted both tumor cell lines without any compromise in lytic potency (Figure 9D).
• the LC-U2S3 fusion i.e., the antibody fusion protein wherein an A1-A2 domain is fused to the light chain of the antibody
• the LC- U2S3 fusion also out-performed the HC fusion in an in vitro killing assay with Ramos target cells (Figure 10B), and appeared to be more efficacious at early time points in suppressing Raji B cell lymphoma expansion in NSG mice.
• the antibody fusion protein comprising an A1-A2 domain fused to the N-terminus of the light chains of the antibody surprisingly outperformed antibody constructs wherein an A1-A2 domain was fused to the heavy chain.
• Rituximab.LC-U2S3 (Rit-S3; the antibody fusion protein wherein the U2S3 A1-A2 domain is fused to the light chain of the antibody) was deployed in further experiments exploring dosing parameters for lymphoma control.
• An intermediate Rit-S3 dose of 20 mg was shown to be the most efficacious as high concentrations may result in over saturation of receptors on the CAR cells and antigens on the tumor cells, thereby interfering with productive engagement.
• a higher frequency of Rit-S3 administration of every two days versus every four days paired with a higher dose (10x10 6 ) of convertibleCAR-T cells resulted in the greatest suppression of tumor growth.
• Rit-S3 alone was ineffective at tumor control while a graft-vs-tumor effect was consistently observed in both untransduced and convertibleCAR only cohorts.
• Rit-S3 was detectable in the serum of mice throughout the course of the study with peak levels appearing earlier with more frequent dosing.
• a Raji disseminated lymphoma model with optimized convertibleCAR-T dosing was performed with 20 mg Rit-S3 dosing every two days comparing 5x10 6 (5M) to 15x10 6 (15M) convertibleCAR-T cells.
• RITscFv-CAR cells were also included which have in vitro Ramos killing potency comparable to convertibleCAR-T cells ( Figure 8B).
• Figure 8B At 5M total T cells, both RITscFv-CAR and convertibleCARs+Rit-S3 were effective at controlling tumor.
• conve tibleCAR-T cells inhibit subcutaneous lymphomas.
• Raji B-cells were implanted subcutaneously to assess the ability of the convertibleCAR system to suppress growth of a solid tumor mass.
• 7x10 6 (7M) or 35x10 6 (35M) convertibleCAR-Ts were administered after a single IV dose of 60 g Rit-S3.
• one cohort received 35M cells that were pre-armed with a saturating concentration of Rit-S3 prior to administration but no additional MicAbody introduced injections.
• Administration of 7M convertibleCAR-T cells along with Rit-S3 (7M+Rit-S3) resulted in reduced tumor size relative to convertibleCAR-T cells alone ( Figure 12A).
• the cohort receiving 35M+Rit-S3 maintained relatively high CD3+T cell numbers but were not well-armed with MicAbody while the 7M+Rit-S3 cohort did have cells that maintained surface-associated MicAbody. This suggested that, as MicAbody levels fell below detectable limits in the plasma, CAR arming could not be maintained at high CAR-T cell levels.
• An alternative possibility is that the higher CD3+cell numbers in the 35M+Rit-S3 cohort reflect expansion of a graft-vs-tumor subset of cells that do not express the CAR construct. Flowever, the elevated CD3+ cell numbers were not seen in the 35M pre-armed cohort suggesting that this is not the case.
• the U2R variant was fused to either the N- or C-terminus of the wild-type human lgG1 Fc-domain or to mutant Fc domains previously described as enhancing C1q binding - S267E/H268F/S324T/G236A/1332E (“EFTAE”) and K326A/E333A (“AA”) ( Figure 13A).
• FTAE enhancing C1q binding - S267E/H268F/S324T/G236A/1332E
• AA K326A/E333A
• Flow cytometry characterization of STAT3 and STAT5 phosphorylation revealed that exposure to wild- type IL-2 or IL-15 resulted in an increase of pSTAT3 and pSTAT5 in both untransduced as well as convert! bleCAR-CD8 cells.
• Treatment of untransduced cells with U2S3-hFc-mutlL2 resulted only in a minimal shift in pSTAT5 relative to the no cytokine control, consistent with mutlL2's retention of I ⁇ -2Rb/go binding.
• bleCAR-CD8 cells responded to both U2S3-hFc-mutlL2 and U2S3-hFc-mutlL15 with an increase in pSTAT5 levels via g-chain activation of JAK3.
• pSTAT3 signal was observed, indicating a reduction in JAK1 activation through I ⁇ -2Rb28 in both scenarios as a consequence of disruption of Roc binding, a hypothesis supported by IL-15Roc's role in increasing the affinity of IL-15 for I ⁇ -2Rb.
• the kinetics of responses U2S3-hFc-mutlL2 and U2S3-hFc-mutlL15 were nearly identical, indicating functional redundancy in their mutant forms.
• U2S3-hFc-mutlL2 was shown to have an in vivo PK half-life of a few days (Figure 14E).
• convertibleCAR-T cells administered to NSG mice in the absence of tumor underwent a homeostatic expansion, peaking at three days followed by contraction.
• Three injections of U2S3-hFc-mutlL2 staged one week apart resulted in a dramatic expansion of human T cells in the peripheral blood (Figure 15A) and T cell numbers contracted after cessation of U2S3-hFc-mutlL2 support with CD8+ T cells driving the bulk of the expansion.
• the proportion of GFP+ CD8+ T cells increased to 100% demonstrating selective expansion of iNKG2D-CAR expressing cells but not untransduced cells (Figure 15B).
• the CD4+ and CD8+ T cells responded robustly to both anti-CD3 and wild-type IL-2 positive controls as well as to the lowest dose of U2S3- hFc-wtlL2.
• Proliferative responses to U2S3-hFc-mutlL2 occurred in a dose-dependent manner with expansion observed across donors at levels above 300 lUe/mL but not achieving levels comparable to those of the IL-2 positive control until 30,000 lUe/mL.
• Treg responses were comparable to those of CD4+ and CD8+ cells with the exception of cells from one donor (who additionally had a muted response to anti-CD3 stimulation) that responded to U2S3-hFc-mutlL2 at a lower concentration than the other donors.
• Antibody fusion constructs comprising heavy chains comprising variable region sequences of SEC ID NO: 1 and light chains comprising variable region sequences of SEQ ID NO: 8, wherein the light chains were fused at the C- terminus to an A1-A2 domain, outperformed constructs wherein the A1-A2 domain was attached to heavy chains in killing tumor cells. Additionally, constructs wherein the A1-A2 domain were fused to the light chains via the APTSSSGGGGS linker (SEQ ID NO: 10) surprisingly outperformed all constructs tested at almost all concentrations (0.04 nM, 0.2 nM, 1 nM, and 5 nM).
• U2S3 (NQ) domain When the U2S3 (NQ) domain was expressed in CHO cells, N-glycosylation was observed, despite the fact that N-glycosylation appeared to be virtually absent when expression was performed in HEK 293 cells. Further substitution of the U2S3 (NQ) A1-A2 domain was performed to introduce an alanine (U2S3 (AYT)) or glutamine (U2S3 (QYT)) at position 84. An Octet binding experiment was performed with this additional mutation in the context of a Rituximab-MicAbody. Substitution at position 84 with an alanine or a glutamine did not change binding to iNKG2D.YA. Cytotoxicity also was confirmed. See Figure 20.
• Ramos target cells were loaded with calcein and co-cultured with iNKG2D-CAR CD8+T cells for two hours at a 20:1 E:T ratio in the presence of an increasing nM concentration of each tested MicAbody (Rituximab fused to U2S3, U2S3 (NQ), U2S3 (AYT), and U2S3 (QYT)). The amount of calcein released was quantified. All MicAbodies mediated comparable levels of cytotoxicity indicating that (a) CD20 engagement was not compromised and (b) iNKG2D engagement was not compromised by the substitutions described herein. Thus, the A1-A2 domains described herein demonstrated reduced glycosylation, mediated comparable levels of target cell binding and cytotoxicity using iNKG2D-CAR, and demonstrated further reduced binding to wild-type NKG2D.
• the disclosure describes the engineering of a privileged receptor-ligand (iNKG2D.YA and U2S3) pairing comprised of human components for a highly adaptable CAR, resulting in a versatile and broadly controllable platform.
• iNKG2D.YA-CAR receptor itself is held invariant on T cells with CAR function readily directed to potentially any antigen of interest by virtue of attaching the orthogonal ligand to the appropriate antigen-recognizing antibody.
• the same convertibleCAR-T cells can be retargeted as needed if, for example, the original tumor antigen becomes downregulated during the course of therapy.
• This targeting flexibility is not limited to sequential engagement of antigens, but can also be multiplexed to simultaneously direct T cells to more than one antigen in order to reduce the likelihood of tumor escape by antigen loss, address the issue of heterogeneity of intratumoral antigen expression, or even simultaneously target tumor and suppressive cellular components of the tumor microenvironment.
• Traditional scFv-CAR cells are generally committed to a fixed expression level of a receptor which reduces their ability to discriminate between antigen levels present on healthy versus aberrant cells.
• the use of switch/adaptor strategies like MicAbodies with convertibleCAR-T cells, may provide an opportunity to differentially engage CAR-Ts to achieve a therapeutic index that reduces the risk of severe adverse events.
• CAR therapies require a preconditioning lymphodepletion regimen to promote engraftment and expansion of CAR cells, one rationale being that it provides a more verdant immunological setting for CARs to expand.
• Robust and controllable convertibleCAR-T expansion in patients may supplant the need for lymphodepletion, allowing for retention of endogenous immune functions that are fully competent to support the initial convertibleCAR-mediated anti-tumor activity.
• Another clinical strategy might be to deliver cytokine-ligand fusions to bolster convertibleCAR-T function, possibly with a cycling regimen to reduce T cell exhaustion and promote the maintenance of memory T cells.
• each component of the convertibleCAR system - the iNKG2D-based CAR receptor and the MicAbody (which is ADCC-deficient) - are functionally inert on their own. This has advantages during manufacturing, particularly in the context of indications such as T cell malignancies where traditional scFv-based CARs encounter expansion hurdles due to fratricide. Additionally, it provides enhanced control of CAR function during treatment.
• the disclosure demonstrates that convertibleCAR-T cells can be armed with MicAbody prior to administration to provide an initial burst of anti-tumor activity on par with traditional scFv-CARs.
• the disclosure identifies high-affinity orthogonal MicA and ULBP3 variants to iNKG2D.YA that are non-redundant in their amino acid compositions through the helix 4 domain. Additionally, a completely independent iNKG2D.AF and U2R pairing is described. Having mutually exclusive receptor-ligand pairs enables, for example, their introduction into distinct cell populations (e.g., CD4 and CD8 T-cells) to differentially engage them as needed.
• distinct cell populations e.g., CD4 and CD8 T-cells
• the two iNKG2D variants could be expressed with split intracellular signaling domains to provide dual antigen-dependent activation to enhance on-tumor selectivity.
• the two iNKG2D variants could be differentially linked to either activating or immunosuppressive domains to enhance the discriminatory power of the T cells between tumors or healthy tissue, respectively.
• the system described herein has demonstrated capabilities to not only be readily targeted to different cell-surface antigens but can also be selectively engaged exogenously to drive cell expansion.
• the privileged receptor-ligand interaction that has been developed is agnostic to cell type and can be engineered into any cell of interest as long as the cell-appropriate signaling domains are provided.
• the adoptive cellular therapy field is aggressively pursuing the development of allogeneic cells to bring down the time, complexity, and cost of manufacturing to provide a more consistent, readily accessible product.
• a highly adaptable CAR system would be powerfully synergistic with allogenic efforts and once a truly universal allogeneic CAR system has been validated, the therapeutic field then becomes characterized by the relative ease of developing and implementing a library of adaptor molecules from which personalized selections can be made. This strategy also broadens the potential areas of application to any pathogenic cell with a targetable surface antigen.

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