WO2023150724A2 - Antigen binding proteins that bind b7-h3 - Google Patents

Abstract

The present disclosure provides B7-H3 binding proteins, particularly anti-B7-H3 antibodies, or antigen-binding portions thereof, that specifically bind B7-H3 and uses thereof. Various aspects of the anti-B7-H3 antibodies relate to antibody fragments, single-chain antibodies, pharmaceutical compositions, nucleic acids, recombinant expression vectors, host cells, and methods for preparing and using such anti-B7-H3 antibodies. Methods for using the anti-B7-H3 antibodies include in vitro and in vivo methods for binding B7-H3 and treating diseases associated with B7-H3 expression.

Description

ANTIGEN BINDING PROTEINS THAT BIND B7-H3

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority of US Provisional Patent Application No. 63/306,938, filed February 4, 2022, which is incorporated herein by reference in its entirety for all purposes.

[0002] Throughout this application various publications, patents, and/or patent applications are referenced. The disclosures of the publications, patents and/or patent applications are hereby incorporated by reference in their entireties into this application in order to more fully describe the state of the art to which this disclosure pertains.

TECHNICAL FIELD

[0003] The present disclosure provides antigen binding proteins that bind specifically to B7-H3 and nucleic acids that encode the antigen binding proteins, vectors comprising the nucleic acids, host cells harboring the vectors, and method of use thereof.

BACKGROUND

[0004] B7 family checkpoint molecules have come to the front of cancer research with the concept that tumor cells exploit them to escape immune surveillance. The B7 family molecules are capable of controlling and suppressing immune responses of T cells as well as NK cells. The growing B7 family now comprises 10 members, which are CD80 (also known as B7.1), CD86 (also known as B7.2), B7-H1 (also known as PD-L1 or CD274), B7-DC (also known as PD-L2 or CD273), B7-H2 (also known as ICOSL), B7-H3 (also known as CD276), B7-H4 (also known as B7S1, B7x, or Vtcnl), B7-H5 (also known as VISTA, GI24, Diesl or PD-1H), B7-H6 (also known as NCR3LG1), and B7-H7 (also known as HHLA2).

Compelling evidence indicates that B7 molecules not only provide crucial positive signals to stimulate and support T-cell action, but also offer negative signals that control and suppress T-cell responses.

[0005] The B7 homology 3 protein (B7-H3) (also known as CD276 and B7RP-2, and referred to herein as “B7-H3”) is a type I transmembrane glycoprotein of the immunoglobulin superfamily. Human B7-H3 contains a signal peptide at the N-terminus, an extracellular immunoglobulin-like variable region (Ig-like V-type 1) and constant region (Ig-like C2-type 1), a transmembrane region, and a cytoplasmic tail region having 45 amino acids (Zhou Y.H. et al., 2007, Tissue Antigens. 70 (2): 96-104). B7-H3 has three splicing variants, B7-H3OC and B7-H3P- The extracellular domain of B7-H3OC consists of two immunoglobulin domains of Ig-like Vtype-Ig-like C-type (also known as 2IgB7-H3), while the extracellular domain of B7-H3P consists of four immunoglobulin domains of Ig-like V-type -Ig-like C-type-Ig-like V-type-Ig-like C-type (also known as 4IgB7-H3). The predominant B7-H3 isoform in human tissues and cell lines is the 4IgB7-H3 isoform (Steinberger et al., 2004, J. Immunol. 172(4): 2352-9).

[0006] B7-H3 has been reported as having both co- stimulatory and co-inhibitory signaling functions (see, e.g., Chapoval et al., 2001, Nat. Immunol. 2: 269-74; Suh et al., 2003, Nat. Immunol. 4: 899-906; Prasad et al., 2004, J. Immunol. 173: 2500-6; and Wang et al., 2005, Eur. J. Immunol. 35: 428-38; Yang, S. et al., 2020, Int. J. Biol. Sci. 16(11): 1767- 1773). For example, in vitro studies have shown B7-H3's co-stimulatory function, since B7-H3 was shown to induce proliferation of cytotoxic T-lymphocytes (CTLs) and upregulate interferon gamma (IFN-y) production in the presence of stimulatory anti-CD3 antibody to mimic the T cell receptor signal (Chapoval et al., 2001, Nat. Immunol. 2: 269-74). Moreover, in vivo studies using cardiac allografts in B7-h3 knockout/deficient -I- mice showed decreased production of key cytokine, chemokine and chemokine receptor mRNA transcripts (e.g., IL- 2, IFN-y, monocyte chemoattractant protein (MCP-1) and IFN-inducible protein (IP)-10) as compared to wild-type littermate control (Wang et al., 2005, Eur. J. Immunol. 35: 428-38). In contrast, B7-H3 co-inhibitory function has been observed, for example, in mice where B7-h3 protein inhibited T-cell activation and effector cytokine production (Suh et al., 2003, Nat. Immunol. 4: 899-906). Although no ligands have been identified for human B7-H3, murine B7-h3 has been found to bind to the triggering receptor expressed on myeloid cells (TREM) like transcript 2 (TLT-2), a modulator of adaptive an innate immunity cellular response.

Binding of murine B7-h3 to TLT-2 on CD8⁺ T-cells induces T-cell effector functions such as proliferation, cytotoxicity and cytokine production (Hashiguchi et al., 2008, Proc. Nat'l. Acad. Sci. U.S.A. 105(30): 10495-500).

[0007] Enoblituzumab (MGA271), a humanized mAb targeting B7-H3, mediates potent antibody-dependent cellular cytotoxicity (ADCC) by recruiting NK cells against a broad range of tumor types. For example, it was investigated in treating refractory B7-H3- expressing tumors such as melanoma, and B7-H3-expressing neoplasms including osteosarcoma and Ewing's sarcoma. Furthermore, MGA271 exhibited potent antitumor activity in xenograft models of B7-H3-expressing renal cell and bladder carcinoma. And in cynomolgus monkeys, no significant safety findings were discovered in toxicology studies (Loo, D. et al., 2012, Clin. Cancer Res. 18:3834-45). [0008] B7-H3 protein is not expressed or is poorly expressed in normal tissues and cells, but highly expressed in various tumors (solid tumors as well as hematological malignancies) and is closely correlated with tumor progression, patient survival and disease prognosis. It has been clinically reported that B7-H3 is over-expressed in many types of cancers, including prostate cancer, clear cell renal cell carcinoma, glioma, melanoma, lung cancer, non-small cell lung cancer (NSCLC), small cell lung cancer, pancreatic cancer, gastric cancer, acute myeloid leukemia (AML), non-Hodgkin's lymphoma (NHL), ovarian cancer, colorectal cancer, colon cancer, renal cancer, hepatocellular carcinoma, kidney cancer, head and neck cancer, hypopharyngeal squamous cell carcinoma, glioblastoma, neuroblastoma, breast cancer, urothelial cancer, and urothelial cell carcinoma. Although the role of B7-H3 in cancer cells is unclear, its expression may orchestrate signaling events (and/or mediate cell-to-cell engagement) that may protect cancer cells from innate and adaptive immune responses. For example, B7-H3 is overexpressed in high-grade prostatic intraepithelial neoplasia and adenocarcinomas of the prostate, and high expression levels of B7-H3 in these cancerous cells is associated with an increased risk of cancer progression after surgery (Roth et al., 2007, Cancer Res. 67(16): 7893-900). Further, tumor B7-H3 expression in NSCLC inversely correlated with the number of tumor-infiltrating lymphocytes and significantly correlated with lymph node metastasis (Sun et al., 2006, Lung Cancer 53(2): 143-51). The level of circulating soluble B7-H3 (sB7-H3) polypeptide in NSCLC patients has also been associated with more advanced tumor stage, increased/increasing tumor size, lymph node metastasis, and distant metastasis indicative of aggressive disease progression (Yamato et al., 2009, Br. J. Cancer 101(10): 1709- 16).

[0009] Although, B7-H3 has a coinhibitory function and a costimulating function on T cells, the expression on either tumor cells or diffuse tumor vasculature is significantly associated with an increased risk of death and fatal outcome. Targeting B7-H3 not only enhances antitumor immunity but also inhibits tumor angiogenesis, presumably by engaging with B7-H3 expressed by vasculature associated macrophages that are known to favor tumor angiogenesis through cytokine secretion.

[0010] There are reports that B7-H3 molecules are associated with autoimmune diseases. In rheumatism and other autoimmune diseases, reports that B7-H3 is important for the interaction between fibroblast-like synoviocytes and activated T cells (Yih-Wen, C. et al., 2008, Current Cancer Drug Targets 8: 404 - 413) and B7-H3 activated macrophages has been reported to be a co- stimulatory factor in the release of cytokines from septicemia and to be involved in the development of sepsis (Harlow, E. and Lane, D.: “Antibodies: A Laboratory Manual”, 1988, Cold Spring Harbor Laboratory). In addition, administration of anti-B7- H3 antibody in the induction phase to the mouse asthma model suppressed Th2 cell-induced cytokine production in the regional lymph nodes, and asthma improved. (Leitner, J. et al., 2009, European Journal of Immunology 39: 1754 - 1764).

[0011] Thus, B7-H3 is an attractive antigen for targeting with antibodies. The present disclosure provides B7-H3 binding proteins, particularly anti-B7-H3 antibodies or antigenbinding portions thereof, that specifically bind B7-H3, and uses thereof.

SUMMARY

[0012] In one aspect, provided herein is an anti-B7-H3 antigen-binding protein or fully human anti-B7-H3 antibody, or an antigen-binding fragment thereof, comprising a heavy chain variable region and a light chain variable region, wherein the heavy chain variable region comprises a heavy chain complementarity determining region 1 (CDR1) a heavy chain CDR2 and a heavy chain CDR3, and the light chain variable region comprises a light chain CDR1, a light chain CDR2, and a light chain CDR3; and the heavy chain CDR1 has the amino acid sequence of SEQ ID NO: 12, the heavy chain CDR2 has the amino acid sequence of SEQ ID NO: 13, the heavy chain CDR3 has the amino acid sequence of SEQ ID NO: 14, the light chain CDR1 has the amino acid sequence of SEQ ID NO: 15, the light chain CDR2 has the amino acid sequence of SEQ ID NO: 16, and the light chain CDR3 has the amino acid sequence of SEQ ID NO: 17. In embodiments, the heavy chain variable region has at least 95% sequence identity to the amino acid sequence of SEQ ID NO: 10, and the light chain variable region has at least 95% sequence identity to the amino acid sequence of SEQ ID NO:11.

[0013] In an aspect, provided herein is an antigen-binding protein or fully human anti-B7- H3 antibody, or an antigen-binding fragment thereof, comprising a heavy chain variable region and a light chain variable region, the heavy chain variable region having at least 95% sequence identity to the amino acid sequence of SEQ ID NO: 10, and the light chain variable region having at least 95% sequence identity to the amino acid sequence of SEQ ID NO: 11. [0014] In an aspect, provided herein is an antigen-binding protein or fully human anti-B7- H3 antibody, or an antigen-binding fragment thereof, comprising a heavy chain variable region and a light chain variable region, wherein the heavy chain variable region and the light chain variable region comprise the amino acid sequences of SEQ ID NOS: 10 and 11, respectively (e.g., herein called VA).

[0015] In embodiments, the antigen binding fragment includes a Fab fragment. In embodiments, the antigen binding fragment includes a single chain antibody, wherein the heavy chain variable domain and the light chain variable domain are joined together with a peptide linker. In embodiments, any one of the disclosed antigen-binding protein, antibody or antigen-binding fragment thereof, include an IgG antibody, such as an IgGl, IgG2, IgG3 or IgG4 class antibody. In embodiments, the IgG antibody is an is an IgGl or IgG4 class antibody. In embodiments, the IgGl antibody comprises a mutant Fc region. In embodiments, the mutant Fc region comprises one or more mutations selected from L234A and L235A. In embodiments, the mutant Fc region comprises the mutations L234A and L235A (LALA). In embodiments, any one of the disclosed antigen-binding protein, antibody or antigen-binding fragment thereof, binds human anti-B7-H3 protein with a KD of 10’⁷ M or less.

[0016] In an aspect, provided herein is a pharmaceutical composition, including any one of the disclosed antigen-binding protein, antibody or antigen-binding fragment and a pharmaceutically acceptable excipient.

[0017] In an aspect, provided herein is a kit including any one of the disclosed antigenbinding protein, antibody or antigen-binding fragments and a pharmaceutically acceptable excipient.

[0018] In an aspect, provided herein is a nucleic acid that encodes a polypeptide comprising the heavy chain variable region of any one of the disclosed antigen-binding protein, antibody or antigen-binding fragment.

[0019] In an aspect, provided herein is a nucleic acid that encodes a polypeptide comprising the light chain variable region of any one of the disclosed antigen-binding protein, antibody or antigen-binding fragment.

[0020] In an aspect, provided herein is a nucleic acid that encodes (i) a first polypeptide comprising the heavy chain variable region of any one of the disclosed antigen-binding protein, antibody or antigen-binding fragment, and (ii) a second polypeptide comprising the light chain variable region of any one of the disclosed antigen-binding protein, antibody or antigen-binding fragment.

[0021] In an aspect, provided herein is a vector including any one of the disclosed nucleic acids.

[0022] In an aspect, provided herein is a host cell harboring any of the disclosed vectors. In embodiments, the disclosed vector includes an expression vector, and the host cell expresses a polypeptide comprising the heavy chain variable region. In embodiments, the disclosed vector includes an expression vector, and the host cell expresses a polypeptide comprising the light chain variable region. [0023] In an aspect, provided herein is a host cell harboring a first vector and a second vector. In embodiments the first vector comprises a first expression vector, the second vector comprises a second expression vector, and the host cell expresses first and second polypeptides comprising the heavy and the light chain variable regions, respectively.

[0024] In an aspect, provided herein is a method for preparing a polypeptide comprising a heavy chain variable region of an antigen-binding protein, antibody or antigen-binding fragment, the method comprising: culturing a population of the host cell under conditions suitable for expressing the polypeptide comprising the heavy chain variable region of the antigen-binding protein, antibody or antigen-binding fragment. In embodiments, the method further includes recovering from the host cells the expressed polypeptide comprising the heavy chain variable region of the antigen-binding protein, antibody or antigen-binding fragment.

[0025] In an aspect, provided herein is a method for preparing a polypeptide comprising a light chain variable region of an antigen-binding protein, antibody or antigen-binding fragment, the method comprising: culturing a population of the host cell under conditions suitable for expressing the polypeptide comprising the light chain variable region of the antigen-binding protein, antibody or antigen-binding fragment. In embodiments, the method further includes recovering from the host cells the expressed polypeptide comprising the light chain variable region of the antigen-binding protein, antibody or antigen-binding fragment. [0026] In an aspect, provided herein is a method for preparing (i) a first polypeptide comprising a heavy chain variable region of an antigen-binding protein, antibody or antigenbinding fragment, and (ii) a second polypeptide comprising a light chain variable region of an antigen-binding protein, antibody or antigen-binding fragment, the method comprising: culturing a population of the host cell under conditions suitable for expressing (i) the first polypeptide, and (ii) the second polypeptide. In embodiments, the method further includes recovering from the host cells (i) the expressed first polypeptide, and (ii) the expressed second polypeptide.

[0027] In an aspect, provided herein is a method for inhibiting growth or proliferation of B7-H3 -expressing cells, comprising: contacting a population of effector cells with a population of target cells which express B7-H3, in the presence of any one of the disclosed antigen-binding proteins, antibodies or antigen-binding fragments, under conditions that are suitable for inhibiting growth or proliferation of the B7-H3-expressing cells. In embodiments, the population of effector cells comprises PBMCs or NK cells. In embodiments, the population of target cells comprise B7-H3 expressing human cancer cells or transgenic cells expressing B7-H3. In embodiments, the ratio of the effector-to-target cells is 1-5:1, such as 1:1, 2:1, 3:1, 4:1 or 5:1. In embodiments, the ratio of the effector-to-target cells is 5-10:1, 10- 20:1, or 20-30:1. In some embodiments, the method is an in vitro method. In some embodiments, the target cells are in a subject and the antigen-binding protein, antibody, or antigen-binding fragment is administered to the subject. The effector cells may also be in the subject.

[0028] In an aspect, provided herein is a method for killing B7-H3-expressing cells, comprising: contacting a population of effector cells with a population of target cells which express B7-H3 in the presence of any one of the disclosed antigen-binding proteins, antibodies or antigen-binding fragments, under conditions that are suitable for killing the B7- H3-expressing cells. In embodiments, the population of effector cells comprises PBMCs or NK cells. In embodiments, the population of target cells comprise B7-H3 expressing human cancer cells or transgenic cells expressing B7-H3. In embodiments, the ratio of the effector- to-target cells is 1-5:1, such as 1:1, 2:1, 3:1, 4: 1 or 5:1. In embodiments, the ratio of the effector-to-target cells is 5-10:1, 10-20:1, or 20-30:1. In embodiments, provided herein is a method of restoring the function of B7-H3 -expressing immune cell subsets. In some embodiments, the method is an in vitro method. In some embodiments, the target cells are in a subject and the antigen-binding protein, antibody, or antigen-binding fragment is administered to the subject. The effector cells may also be in the subject.

[0029] In an aspect, provided herein is a method for treating a subject having a disease associated with B7-H3 expression, the method comprising: administering to the subject an effective amount of a pharmaceutical composition comprising the any one of the disclosed antigen-binding proteins, antibodies or antigen-binding fragments. In embodiments, the disease associated with B7-H3 expression is cancer. In embodiments, the cancer is carcinoma of the ovary, colon, prostate, skin, pancreas, kidney, urothelial, or lung cancer. In embodiments, the cancer is acute myeloid lymphoma (AML), non-Hodgkin lymphoma (NHL), non-small cell lung cancer (NSCLC), small cell lung cancer, urothelial cell carcinoma, esophageal cancer, hepatocellular carcinoma, glioma, neuroblastoma, glioblastoma multiforme, blastoma, sarcoma, leukemia, lymphoid malignancies, pancreatic cancer, head and neck cancer, ovarian cancer, oral cancer, breast cancer, triple negative breast cancer (TNBC), lymphoma, renal cell carcinoma, clear cell renal cell carcinoma, colon cancer, colorectal cancer, melanoma, stomach cancer, lung cancer, liver cancer, bladder cancer, prostate cancer, anal cancer, endometrial cancer, vulvar cancer, squamous cell tumors, hypopharyngeal squamous cell carcinoma, and squamous cell carcinoma (e.g., squamous cell lung cancer or squamous cell head and neck cancer). In embodiments, the cancer, such as any one of the cancers listed above, is a metastatic cancer, refractory cancer, or recurrent cancer.

DESCRIPTION OF THE DRAWINGS

[0030] FIG. 1A shows an SPR sensorgram of binding kinetics of B7-H3-VA (anti-B7-H3 antibody clone VA).

[0031] FIG. IB shows an SPR sensorgram of binding kinetics of enoblituzumab (commercial anti-B7-H3 antibody developed by MacroGenics).

[0032] FIGS. 2A-B show the results of binding of anti-B7-H3 antibody by human proteins B7-H1, B7-H2, B7-H3, B7-H4, B7-H5, B7-H6, B7-H7, B7.1 and B7.2 as assessed by ELISA assay. FIG. 2A shows the results of binding of anti-B7-H3-VA antibody. FIG. 2B shows the results of binding of anti-B7-H3-VA LALA antibody.

[0033] FIG. 3 shows the results of binding of anti-B7-H3 antibody (clone VA) and Enoblituzumab (humanized B7-H3 antibody, MacroGenics) by human, mouse, cynomolgus, canine, rat, and rabbit B7-H3 protein, as assessed by ELISA assay.

[0034] FIG. 4 shows the thermostability of anti-B7-H3 antibody (clone VA).

[0035] FIG. 5 shows immuno- stained tissue biopsies analyzed by confocal laser scanning microscopy. The tissue biopsies show elevated binding of B7-H3 (clone VA) in malignant patient tissue, but no binding in normal tissue or tissue adjacent to cancer tissue.

[0036] FIG. 6A shows results of direct cell binding using flow cytometry, comparing anti- B7-H3 antibody (VA clone) to enoblituzumab (anti-B7-H3 antibody, MacroGenics) binding against B7-H3 overexpressed osteosarcoma cells (U2OS). An anti-RSV antibody was used as negative control.

[0037] FIG. 6B shows results of direct cell binding using flow cytometry, comparing anti- B7-H3 antibody (VA clone) to enoblituzumab (anti-B7-H3 antibody, MacroGenics) binding against B7-H3 overexpressed neuroblastoma cells SK-N-BE(2)). An anti-RSV antibody was used as negative control.

[0038] FIGS. 7A-C show results of antibody dependent cell-mediated cytotoxicity (ADCC) assay of anti-B7-H3 antibody (VA clone) and enoblituzumab (anti-B7-H3 antibody, MacroGenics) in human osteosarcoma (U2OS) cells. FIG. 7A shows results of ADCC prediction assay of anti-B7-H3 antibody (VA clone) and enoblituzumab (anti-B7-H3 antibody, MacroGenics) where the effector cells were engineered Jurkat cells. FIG. 7B shows results of ADCC assay of anti-B7-H3 antibody (VA clone) and enoblituzumab (anti-B7-H3 antibody, MacroGenics) where the effector cells were NK cells. FIG. 7C shows results of ADCC assay of anti-B7-H3 antibody (VA clone) and anti-RSV antibody where the effector cells were NK cells.

[0039] FIGS. 8A-B show results of antibody dependent cell-mediated cytotoxicity (ADCC) assay of anti-B7-H3 antibody (VA clone) and enoblituzumab (anti-B7-H3 antibody, MacroGenics) in human lung cancer cells A549 wildtype (WT) or B7-H3-knockout (KO) (target cells), and where the effector cells were engineered Jurkat cells. FIG. 8A shows results of ADCC assay of anti-B7-H3 antibody (VA clone) where target cells were A549 WT. FIG. 8B shows results of ADCC assay of anti-B7-H3 antibody (VA clone) where target cells were A549 KO.

[0040] FIG. 9 shows B7-H3 surface expression by A549 and A549 B7-H3 KO cells assessed by flow cytometric analysis. Gating is focused on B7-H3 expressing cells, expressed as [%] of population. ISO is an anti-RSV antibody used as isotype control.

[0041] FIG. 10 shows the effects of anti-B7-H3 antibody (VA clone), anti-RSV antibody (isotype control), and HBSS buffer (vehicle control) on SK-N-BE(2) human neuroblastoma tumor model when administered at high dosing frequency. **P<0.01; ***P<0.001 conducted between vehicle group and anti-B7-H3 antibody (VA clone) groups.

[0042] FIG. 11 shows the effects of anti-B7-H3 antibody (VA clone), anti-RSV antibody (isotype control), and HBSS buffer (vehicle control) on SK-N-BE(2) human neuroblastoma tumor model when administered at low dosing frequency. **P<0.01; ***P<0.001 conducted between vehicle group and anti-B7-H3 antibody (VA clone) groups.

[0043] FIG. 12A shows a schematic of a hemagglutination reaction. FIGS. 12B-C show images of hemagglutination assays comparing activity of anti-B7-H3 antibodies STI-B7-H3- VA and MG-B7-H3 (enoblituzumab from Macrogenics), and a positive and a negative control (anti-CD47 antibody Hu5F9 and Isotype, respectively). FIG. 12B shows images of hemagglutination assays comparing activity of anti-B7-H3 antibodies STI-B7-H3-VA and MG-B7-H3 (enoblituzumab from Macrogenics), and a positive and a negative control (anti- CD47 antibody Hu5F9 and Isotype, respectively). FIG. 12C shows images of hemagglutination assays comparing activity of anti-B7-H3 antibodies STI-B7-H3-VA LALA and MG-B7-H3 (enoblituzumab from Macrogenics), and a positive and a negative control (anti-CD47 antibody Hu5F9 and Isotype, respectively).

[0044] FIG. 13 shows the binding of anti-B7-H3 antibodies B7-H3-VA and Macrogenics (MG-B7-H3, enoblituzumab) to human melanoma A375 cells, human lung carcinoma A549 cells, and human pancreatic carcinoma Panc-1 cells as a function of antibody concentration. [0045] FIG. 14 provides graphs comparing the receptor engagement of anti-B7-H3 antibodies B7-H3-VA and Macrogenics (enoblituzumab, MG-B7-H3) in human melanoma A375 cells, human lung carcinoma A549 cells, and human pancreatic carcinoma Panc-1 cells as a function of antibody concentration. Additionally, provided is a table of binding parameters.

[0046] FIG. 15 provides a graph comparing the receptor engagement of anti-B7-H3 antibodies Macrogenics (enoblituzumab, MG-B7-H3) and B7-H3-VA (with LALA mutation in the Fc region) in human melanoma A375 cells, human lung carcinoma A549 cells, and human pancreatic carcinoma Panc-1 cells as a function of antibody concentration. Additionally, provided is a table of binding parameters.

[0047] FIG. 16 shows CFSE fluorescence of CD4+ T cells on day 0 and after 72 hours (panels 1 and 2, respectively). Panel 3 shows CFSE fluorescence of CD4+ T cells after addition of anti-CD3 antibody. Panel 4 shows CFSE fluorescence of CD4+ T cells after addition of sB7-H3 polypeptide (following addition of anti-CD3 antibody). Panel 5 shows CD4+ T cells after addition of anti-B7-H3-VA antibody (following the addition of sB7-H3). Panel 6 shows CD4+ T cells after addition of anti-RSV antibody (following the addition of sB7-H3). Additionally, provided is a table of division, proliferation, expansion, and replication indices.

[0048] FIG. 17 shows results of antibody dependent cell-mediated cytotoxicity (ADCC) assay of anti-B7-H3 antibodies B7-H3-VA, B7-H3-VA LALA (with LALA mutation in the Fc region), and Macrogenetics (enoblituzumab, MG-B7-H3) in human lung cancer cells A549. R1 and R2 are two independent trials.

[0049] FIG. 18 shows antibodies binding to human RBCs. Top panels show binding of B7- H3-VA, MG-B7-H3 (enoblituzumab), anti-RSV antibody (isotype control), and anti-CD47 antibody Hu5F9 to human RBCs. Bottom panels show binding of B7-H3-VA LALA, MG- B7-H3, anti-RSV antibody (isotype control), and anti-CD47 antibody Hu5F9 to human RBCs.

[0050] FIG. 19 shows SPR sensorgrams of binding kinetics of B7-H3 antibodies (B3-A6, B3-4A1, B3-4F7, B3-D1, B3-2D1, B3-2H1, B3-2E3, and B3-5A6).

[0051] FIG. 20 shows results of a cell binding assay using flow cytometry, comparing anti- B7-H3 antibodies (B3-5A6, B3-2E3, B3-2D1, B3-D1, B3-2G11, and B3-4A1) to MSKCC- B7-H3 antibody (anti-B7-H3 antibody, Memorial Sloan Kettering Cancer Center) binding against dendritic cells.

[0052] DESCRIPTION [0053] Definitions:

[0054] Unless defined otherwise, technical and scientific terms used herein have meanings that are commonly understood by those of ordinary skill in the art unless defined otherwise. Generally, terminologies pertaining to techniques of cell and tissue culture, molecular biology, immunology, microbiology, genetics, transgenic cell production, protein chemistry and nucleic acid chemistry and hybridization described herein are well known and commonly used in the art. The methods and techniques provided herein are generally performed according to conventional procedures well known in the art and as described in various general and more specific references that are cited and discussed herein unless otherwise indicated. See, e.g., Sambrook et al. Molecular Cloning: A Laboratory Manual, 2d ed., Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y. (1989) and Ausubel et al., Current Protocols in Molecular Biology, Greene Publishing Associates (1992). A number of basic texts describe standard antibody production processes, including, Borrebaeck (ed) Antibody Engineering, 2nd Edition Freeman and Company, NY, 1995; McCafferty et al. Antibody Engineering, A Practical Approach IRL at Oxford Press, Oxford, England, 1996; and Paul (1995) Antibody Engineering Protocols Humana Press, Towata, N.J., 1995; Paul (ed.), Fundamental Immunology, Raven Press, N.Y, 1993; Coligan (1991) Current Protocols in Immunology Wiley /Greene, NY; Harlow and Lane (1989) Antibodies: A Laboratory Manual Cold Spring Harbor Press, NY; Stites et al. (eds.) Basic and Clinical Immunology (4th ed.) Lange Medical Publications, Los Altos, Calif., and references cited therein; Coding Monoclonal Antibodies: Principles and Practice (2nd ed.) Academic Press, New York, N.Y., 1986, and Kohler and Milstein Nature 256: 495-497, 1975. All of the references cited herein are incorporated herein by reference in their entireties. Enzymatic reactions and enrichment/purification techniques are also well known and are performed according to manufacturer's specifications, as commonly accomplished in the art or as described herein. The terminology used in connection with, and the laboratory procedures and techniques of, analytical chemistry, synthetic organic chemistry, and medicinal and pharmaceutical chemistry described herein are well known and commonly used in the art. Standard techniques can be used for chemical syntheses, chemical analyses, pharmaceutical preparation, formulation, and delivery, and treatment of patients.

[0055] The headings provided herein are not limitations of the various aspects of the disclosure, which aspects can be understood by reference to the specification as a whole. To the extent that any content incorporated by reference is inconsistent with the express content of this disclosure, the express content controls. [0056] Unless otherwise required by context herein, singular terms shall include pluralities and plural terms shall include the singular. Singular forms “a”, “an” and “the”, and singular use of any word, include plural referents unless expressly and unequivocally limited on one referent.

[0057] It is understood the use of the alternative (e.g., “or”) herein is taken to mean either one or both or any combination thereof of the alternatives.

[0058] The term “and/or” used herein is to be taken mean specific disclosure of each of the specified features or components with or without the other. For example, 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).

[0059] As used herein, terms “comprising”, “including”, “having” and “containing”, and their grammatical variants, as used herein are intended to be non-limiting so that one item or multiple items in a list do not exclude other items that can be substituted or added to the listed items. 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.

[0060] As used herein, the term “about” refers 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 one or more than one standard deviation per the practice in the art. Alternatively, “about” or “comprising essentially of’ can mean a range of up to 10% (i.e., ±10%) or more depending on the limitations of the measurement system. For example, about 5 mg can include any number between 4.5 mg and 5.5 mg. 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 instant disclosure, 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. [0061] Numerical ranges include the endpoints of the range. For example, “between 4.5 mg and 5.5 mg” includes 4.5 mg, 5.5 mg, and all values greater than 4.5 mg and less than 5.5 mg.

[0062] The terms “peptide”, “polypeptide” and “protein” and other related terms used herein are used interchangeably and refer to a polymer of amino acids and are not limited to any particular length. Polypeptides may comprise natural and non-natural amino acids. Polypeptides include recombinant or chemically-synthesized forms. Polypeptides also include precursor molecules and mature molecule. Precursor molecules include those that have not yet been subjected to cleavage, for example cleavage by a secretory signal peptide or by non-enzymatic cleavage at certain amino acid residue. Polypeptides include mature molecules that have undergone cleavage. These terms encompass native and artificial proteins, protein fragments and polypeptide analogs (such as muteins, variants, chimeric proteins and fusion proteins) of a protein sequence as well as post-translationally, or otherwise covalently or non-covalently, modified proteins. Two or more polypeptides (e.g., 3 polypeptide chains) can associate with each other, via covalent and/or non-covalent association, to form a multimeric polypeptide complex (e.g., multi- specific antigen binding protein complex). Association of the polypeptide chains can also include peptide folding. Thus, a polypeptide complex can be dimeric, trimeric, tetrameric, or higher order complexes depending on the number of polypeptide chains that form the complex. Polypeptides comprising amino acid sequences of binding proteins that bind B7-H3 (e.g., anti-B7-H3 antibodies or antigen-binding portions thereof) prepared using recombinant procedures are described herein.

[0063] The terms “nucleic acid”, “polynucleotide” and “oligonucleotide” and other related terms used herein are used interchangeably and refer to polymers of nucleotides and are not limited to any particular length. Nucleic acids include recombinant and chemically- synthesized forms. Nucleic acids include DNA molecules (cDNA or genomic DNA), RNA molecules (e.g., mRNA), analogs of the DNA or RNA generated using nucleotide analogs (e.g., peptide nucleic acids and non-naturally occurring nucleotide analogs), and hybrids thereof. Nucleic acid molecule can be single- stranded or double- stranded. In embodiments, the nucleic acid molecules of the disclosure comprise a contiguous open reading frame encoding an antibody, or a fragment or scFv, derivative, mutein, or variant thereof. In one embodiment, nucleic acids comprise a one type of polynucleotides or a mixture of two or more different types of polynucleotides. Nucleic acids encoding anti-B7-H3 antibodies or antigen-binding portions thereof, are described herein. [0064] The term “recover” or “recovery” or “recovering”, and other related terms, refers to obtaining a protein (e.g., an antibody or an antigen binding portion thereof), from host cell culture medium or from host cell lysate or from the host cell membrane. In one embodiment, the protein is expressed by the host cell as a recombinant protein fused to a secretion signal peptide sequence which mediates secretion of the expressed protein. The secreted protein can be recovered from the host cell medium. In embodiments, the protein is expressed by the host cell as a recombinant protein that lacks a secretion signal peptide sequence which can be recovered from the host cell lysate. In one embodiment, the protein is expressed by the host cell as a membrane-bound protein which can be recovered using a detergent to release the expressed protein from the host cell membrane. In one embodiment, irrespective of the method used to recover the protein, the protein can be subjected to procedures that remove cellular debris from the recovered protein. For example, the recovered protein can be subjected to chromatography, gel electrophoresis and/or dialysis. In embodiments, the chromatography comprises any one or any combination or two or more procedures including affinity chromatography, hydroxyapatite chromatography, ion-exchange chromatography, reverse phase chromatography and/or chromatography on silica. In embodiments, affinity chromatography comprises protein A or G (cell wall components from Staphylococcus aureus).

[0065] The term “isolated” refers to a protein (e.g., an antibody or an antigen binding portion thereof) or polynucleotide that is substantially free of other cellular material. A protein may be rendered substantially free of naturally associated components (or components associated with a cellular expression system or chemical synthesis methods used to produce the antibody) by isolation, using protein purification techniques well known in the art. The term isolated also refers in some embodiments to protein or polynucleotides that are substantially free of other molecules of the same species, for example other protein or polynucleotides having different amino acid or nucleotide sequences, respectively. The purity of homogeneity of the desired molecule can be assayed using techniques well known in the art, including low resolution methods such as gel electrophoresis and high resolution methods such as HPLC or mass spectrophotometry. In one embodiment, the multi- specific antigen binding protein complexes, or antigen binding portions thereof, of the present disclosure are isolated. In one embodiment, any of the anti-B7-H3 antibodies or antigen binding protein thereof are isolated.

[0066] An “antigen binding protein” and related terms used herein refers to a protein comprising a portion that binds to an antigen and, optionally, a scaffold or framework portion that allows the antigen binding portion to adopt a conformation that promotes binding of the antigen binding protein to the antigen. Examples of antigen binding proteins include antibodies, antibody fragments (e.g., an antigen binding portion of an antibody), antibody derivatives, and antibody analogs. The antigen binding protein can comprise, for example, an alternative protein scaffold or artificial scaffold with grafted CDRs or CDR derivatives. Such scaffolds include, but are not limited to, antibody-derived scaffolds comprising mutations introduced to, for example, stabilize the three-dimensional structure of the antigen binding protein as well as wholly synthetic scaffolds comprising, for example, a biocompatible polymer. See, for example, Komdorfer et al., 2003, Proteins: Structure, Function, and Bioinformatics, 53(1): 121-129; Roque et al., 2004, Biotechnol. Prog. 20:639-654. In addition, peptide antibody mimetics (“PAMs”) can be used, as well as scaffolds based on antibody mimetics utilizing fibronection components as a scaffold. Antigen binding proteins that bind B7-H3 are described herein.

[0067] An antigen binding protein can have, for example, the structure of an immunoglobulin. In one embodiment, an “immunoglobulin” refers to a tetrameric molecule composed of two identical pairs of polypeptide chains, each pair having one “light” (about 25 kDa) and one “heavy” chain (about 50-70 kDa). The amino-terminal portion of each chain includes a variable region of about 100 to 110 or more amino acids primarily responsible for antigen recognition. The carboxy-terminal portion of each chain defines a constant region primarily responsible for effector function. Human light chains are classified as kappa or lambda light chains. Heavy chains are classified as mu, delta, gamma, alpha, or epsilon, and define the antibody's isotype as IgM, IgD, IgG, IgA, and IgE, respectively. Within light and heavy chains, the variable and constant regions are joined by a “J” region of about 12 or more amino acids, with the heavy chain also including a “D” region of about 10 more amino acids. See generally, Fundamental Immunology Ch. 7 (Paul, W., ed., 2nd ed. Raven Press, N.Y. (1989)) (incorporated by reference in its entirety for all purposes). The variable regions of each light/heavy chain pair form the antibody binding site such that an intact immunoglobulin has two antigen binding sites. In embodiments, an antigen binding protein can be a synthetic molecule having a structure that differs from a tetrameric immunoglobulin molecule but still binds a target antigen or binds two or more target antigens. For example, a synthetic antigen binding protein can comprise antibody fragments, 1-6 or more polypeptide chains, asymmetrical assemblies of polypeptides, or other synthetic molecules. Antigen binding proteins having immunoglobulin-like properties that bind specifically to B7-H3 are described herein. [0068] The variable regions of immunoglobulin chains exhibit the same general structure of relatively conserved framework regions (FR) joined by three hypervariable regions, also called complementarity determining regions or CDRs. From N-terminus to C-terminus, both light and heavy chains comprise the domains FR1, CDR1, FR2, CDR2, FR3, CDR3 and FR4. [0069] One or more CDRs may be incorporated into a molecule either covalently or noncovalently to make it an antigen binding protein. An antigen binding protein may incorporate the CDR(s) as part of a larger polypeptide chain, may covalently link the CDR(s) to another polypeptide chain, or may incorporate the CDR(s) noncovalently. The CDRs permit the antigen binding protein to specifically bind to a particular antigen of interest. [0070] The assignment of amino acids to each domain is in accordance with the definitions of Kabat et al. in Sequences of Proteins of Immunological Interest, 5^th Ed., US Dept, of Health and Human Services, PHS, NIH, NIH Publication no. 91-3242, 1991. Other numbering systems for the amino acids in immunoglobulin chains include IMGT.RTM. (international ImMunoGeneTics information system; Lefranc et al, 2005, Dev. Comp. Immunol. 29:185-203;) and Aho (Honegger and Pluckthun, 2001, J. Mol. Biol. 309(3):657- 670); Chothia (Al-Lazikani et al., 1997 Journal of Molecular Biology 273:927-948); and Contact (Maccallum et al., 1996 Journal of Molecular Biology 262:732-745).

[0071] An “antibody” and “antibodies” and related terms used herein refers to an intact immunoglobulin or to an antigen binding portion thereof (or an antigen binding fragment thereof) that binds specifically to an antigen. Antigen binding portions (or the antigen binding fragment) may be produced by recombinant DNA techniques or by enzymatic or chemical cleavage of intact antibodies. Antigen binding portions (or antigen binding fragments) include, inter alia, Fab, Fab', F(ab')2, Fv, domain antibodies (dAbs), and complementarity determining region (CDR) fragments, single-chain antibodies (scFv), chimeric antibodies, diabodies, triabodies, tetrabodies, and polypeptides that contain at least a portion of an immunoglobulin that is sufficient to confer specific antigen binding to the polypeptide.

[0072] Antibodies include recombinantly produced antibodies and antigen binding portions. Antibodies include non-human, chimeric, humanized and fully human antibodies. Antibodies include monospecific, multispecific (e.g., bispecific, trispecific and higher order specificities). Antibodies include tetrameric antibodies, light chain monomers, heavy chain monomers, light chain dimers, heavy chain dimers. Antibodies include F(ab’)2 fragments, Fab’ fragments and Fab fragments. Antibodies include single domain antibodies, monovalent antibodies, single chain antibodies, single chain variable fragment (scFv), camelid antibodies, affibodies, disulfide-linked Fvs (sdFv), anti-idiotypic antibodies (anti-Id), minibodies.

Antibodies include monoclonal and polyclonal populations. Anti-B7-H3 antibodies are described herein.

[0073] An “antigen binding domain,” “antigen binding region,” or “antigen binding site” and other related terms used herein refer to a portion of an antigen binding protein that contains amino acid residues (or other moieties) that interact with an antigen and contribute to the antigen binding protein's specificity and affinity for the antigen. For an antibody that specifically binds to its antigen, this will include at least part of at least one of its CDR domains. Antigen binding domains from anti-B7-H3 antibodies are described herein. In some embodiments, an antigen binding domain is formed from a VH domain and a VL domain.

[0074] The terms “specific binding”, “specifically binds” or “specifically binding” and other related terms, as used herein in the context of an antibody or antigen binding protein (e.g., multi- specific antigen binding protein complex) or antibody fragment, refer to non- covalent or covalent preferential binding to an antigen relative to other molecules or moieties (e.g., an antibody specifically binds to a particular antigen relative to other available antigens). In embodiments, an antibody specifically binds to a target antigen if it binds to the antigen with a dissociation constant KD of 10’⁵ M or less, or 10’⁶ M or less, or 10’⁷ M or less, or 10’⁸ M or less, or 10’⁹ M or less, or IO ¹⁰ M or less. Anti-B7-H3 antibodies that specifically bind B7-H3 are described herein.

[0075] In one embodiment, a dissociation constant (KD) can be measured using a BIACORE surface plasmon resonance (SPR) assay. Surface plasmon resonance refers to an optical phenomenon that allows for the analysis of real-time interactions by detection of alterations in protein concentrations within a biosensor matrix, for example using the BIACORE system (Biacore Life Sciences division of GE Healthcare, Piscataway, NJ).

[0076] An “epitope” and related terms as used herein refers to a portion of an antigen that is bound by an antigen binding protein (e.g., by an antibody or an antigen binding portion thereof). An epitope can comprise portions of two or more antigens that are bound by an antigen binding protein. An epitope can comprise non-contiguous portions of an antigen or of two or more antigens (e.g., amino acid residues that are not contiguous in an antigen’s primary sequence but that, in the context of the antigen’s tertiary and quaternary structure, are near enough to each other to be bound by an antigen binding protein). Generally, the variable regions, particularly the CDRs, of an antibody interact with the epitope. Anti-B7-H3 antibodies, and antigen binding proteins thereof, that bind an epitope of a B7-H3 polypeptide are described herein.

[0077] With respect to antibodies, the term “antagonist” and “antagonistic” refers to a blocking antibody that binds its cognate target antigen and inhibits or reduces the biological activity of the bound antigen. The term “agonist” or “agonistic” refers to an antibody that binds its cognate target antigen in a manner that mimics the binding of the physiological ligand which causes antibody-mediated downstream signaling.

[0078] An “antibody fragment”, “antibody portion”, “antigen-binding fragment of an antibody”, or “antigen-binding portion of an antibody” and other related terms used herein refer to a molecule other than an intact antibody that comprises a portion of an intact antibody that binds the antigen to which the intact antibody binds. Examples of antibody fragments include, but are not limited to, Fv, Fab, Fab', Fab'-SH, F(ab')2; Fd; and Fv fragments, as well as dAb; diabodies; linear antibodies; single-chain antibody molecules (e.g. scFv); polypeptides that contain at least a portion of an antibody that is sufficient to confer specific antigen binding to the polypeptide. Antigen binding portions of an antibody may be produced by recombinant DNA techniques or by enzymatic or chemical cleavage of intact antibodies. Antigen binding portions include, inter alia, Fab, Fab', F(ab')2, Fv, domain antibodies (dAbs), and complementarity determining region (CDR) fragments, chimeric antibodies, diabodies, triabodies, tetrabodies, and polypeptides that contain at least a portion of an immunoglobulin that is sufficient to confer antigen binding properties to the antibody fragment. Antigenbinding fragments of anti-B7-H3 antibodies are described herein.

[0079] The terms “Fab”, “Fab fragment” and other related terms refers to a monovalent fragment comprising a variable light chain region (VL), constant light chain region (CL), variable heavy chain region (VH), and first constant region (CHI). A Fab is capable of binding an antigen. An F(ab')2 fragment is a bivalent fragment comprising two Fab fragments linked by a disulfide bridge at the hinge region. A F(Ab’)2 has antigen binding capability. An Fd fragment comprises VH and CHI regions. An Fv fragment comprises VL and VH regions. An Fv can bind an antigen. A dAb fragment has a VH domain, a VL domain, or an antigen-binding fragment of a VH or VE domain (U.S. Patents 6,846,634 and 6,696,245; U.S. published Application Nos. 2002/02512, 2004/0202995, 2004/0038291, 2004/0009507, 2003/0039958; and Ward et al., 1989, Nature 341:544-546). Fab fragments comprising antigen binding portions from anti-B7-H3 antibodies are described herein.

[0080] A single-chain antibody (scFv) is an antibody in which a VL and a VH region are joined via a linker (e.g., a synthetic sequence of amino acid residues) to form a continuous protein chain. Preferably the linker is long enough to allow the protein chain to fold back on itself and form a monovalent antigen binding site (see, e.g., Bird et al., 1988, Science 242:423-26 and Huston et al., 1988, Proc. Natl. Acad. Sci. USA 85:5879-83). Single chain antibodies comprising antigen binding portions from anti-B7-H3 antibodies are described herein.

[0081] Diabodies are bivalent antibodies comprising two polypeptide chains, wherein each polypeptide chain comprises VH and VL domains joined by a linker that is too short to allow for pairing between two domains on the same chain, thus allowing each domain to pair with a complementary domain on another polypeptide chain (see, e.g., Holliger et al., 1993, Proc. Natl. Acad. Sci. USA 90:6444-48, and Poljak et al., 1994, Structure 2:1121-23). If the two polypeptide chains of a diabody are identical, then a diabody resulting from their pairing will have two identical antigen binding sites. Polypeptide chains having different sequences can be used to make a diabody with two different antigen binding sites. Similarly, tribodies and tetrabodies are antibodies comprising three and four polypeptide chains, respectively, and forming three and four antigen binding sites, respectively, which can be the same or different. Diabody, tribody and tetrabody constructs can be prepared using antigen binding portions from any of the anti-B7-H3 antibodies described herein.

[0082] The term “human antibody” refers to antibodies that have one or more variable and constant regions derived from human immunoglobulin sequences. In one embodiment, all of the variable and constant domains are derived from human immunoglobulin sequences (e.g., a fully human antibody). These antibodies may be prepared in a variety of ways, examples of which are described below, including through recombinant methodologies or through immunization with an antigen of interest of a mouse that is genetically modified to express antibodies derived from human heavy and/or light chain-encoding genes. Fully human anti-B7-H3 antibodies and antigen binding proteins thereof are described herein.

[0083] A “humanized” antibody refers to an antibody having a sequence that differs from the sequence of an antibody derived from a non-human species by one or more amino acid substitutions, deletions, and/or additions, such that the humanized antibody is less likely to induce an immune response, and/or induces a less severe immune response, as compared to the non-human species antibody, when it is administered to a human subject. In one embodiment, certain amino acids in the framework and constant domains of the heavy and/or light chains of the non-human species antibody are mutated to produce the humanized antibody. In another embodiment, the constant domain(s) from a human antibody are fused to the variable domain(s) of a non-human species. In another embodiment, one or more amino acid residues in one or more CDR sequences of a non-human antibody are changed to reduce the likely immunogenicity of the non-human antibody when it is administered to a human subject, wherein the changed amino acid residues either are not critical for immuno specific binding of the antibody to its antigen, or the changes to the amino acid sequence that are made are conservative changes, such that the binding of the humanized antibody to the antigen is not significantly worse than the binding of the non-human antibody to the antigen. Examples of how to make humanized antibodies may be found in U.S. Pat. Nos. 6,054,297, 5,886,152 and 5,877,293.

[0084] The term “chimeric antibody” and related terms used herein refers to an antibody that contains one or more regions from a first antibody and one or more regions from one or more other antibodies. In embodiments, one or more of the CDRs are derived from a human antibody. In another embodiment, all of the CDRs are derived from a human antibody. In another embodiment, the CDRs from more than one human antibody are mixed and matched in a chimeric antibody. For instance, a chimeric antibody may comprise a CDR1 from the light chain of a first human antibody, a CDR2 and a CDR3 from the light chain of a second human antibody, and the CDRs from the heavy chain from a third antibody. In another example, the CDRs originate from different species such as human and mouse, or human and rabbit, or human and goat. One skilled in the art will appreciate that other combinations are possible.

[0085] Further, the framework regions may be derived from one of the same antibodies, from one or more different antibodies, such as a human antibody, or from a humanized antibody. In one example of a chimeric antibody, a portion of the heavy and/or light chain is identical with, homologous to, or derived from an antibody from a particular species or belonging to a particular antibody class or subclass, while the remainder of the chain(s) is/are identical with, homologous to, or derived from an antibody (-ies) from another species or belonging to another antibody class or subclass. Also included are fragments of such antibodies that exhibit the desired biological activity (i.e., the ability to specifically bind a target antigen). Chimeric antibodies can be prepared from portions of any of the anti-B7-H3 antibodies described herein.

[0086] As used herein, the term “variant” polypeptides and “variants” of polypeptides refers to a polypeptide comprising an amino acid sequence with one or more amino acid residues inserted into, deleted from and/or substituted into the amino acid sequence relative to a reference polypeptide sequence. Polypeptide variants include fusion proteins. In the same manner, a variant polynucleotide comprises a nucleotide sequence with one or more nucleotides inserted into, deleted from and/or substituted into the nucleotide sequence relative to another polynucleotide sequence. Polynucleotide variants include fusion polynucleotides. [0087] As used herein, the term “derivative” of a polypeptide is a polypeptide (e.g., an antibody) that has been chemically modified, e.g., via conjugation to another chemical moiety such as, for example, polyethylene glycol, albumin (e.g., human serum albumin), phosphorylation, and glycosylation. Unless otherwise indicated, the term “antibody” includes, in addition to antibodies comprising two full-length heavy chains and two full- length light chains, derivatives, variants, fragments, and muteins thereof, examples of which are described below.

[0088] The term “hinge” refers to an amino acid segment that is generally found between two domains of a protein and may allow for flexibility of the overall construct and movement of one or both of the domains relative to one another. Structurally, a hinge region comprises from about 10 to about 100 amino acids, e.g., from about 15 to about 75 amino acids, from about 20 to about 50 amino acids, or from about 30 to about 60 amino acids. In embodiments, the hinge region is 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or 100 amino acids in length. The hinge region can be derived from a hinge region of a naturally-occurring protein, such as a CD8 hinge region or a fragment thereof, a CD8a hinge region, or a fragment thereof, a hinge region of an antibody (e.g., IgG, IgA, IgM, IgE, or IgD antibodies), or a hinge region that joins the constant domains CHI and CH2 of an antibody. The hinge region can be derived from an antibody and may or may not comprise one or more constant regions of the antibody, or the hinge region comprises the hinge region of an antibody and the CH3 constant region of the antibody, or the hinge region comprises the hinge region of an antibody and the CH2 and CH3 constant regions of the antibody, or the hinge region is a non-naturally occurring peptide, or the hinge region is disposed between the C-terminus of the scFv and the N-terminus of the transmembrane domain. In one embodiment, the hinge region comprises any one or any combination of two or more regions comprising an upper, core or lower hinge sequences from an IgGl, IgG2, IgG3 or IgG4 immunoglobulin molecule. In embodiments, the hinge region comprises an IgGl upper hinge sequence EPKSCDKTHT (SEQ ID

NO: 108). In embodiments, the hinge region comprises an IgGl core hinge sequence CPXCP, wherein X is P, R or S (SEQ ID NO: 109). In one embodiment, the hinge region comprises a lower hinge sequence APELLGGP (SEQ ID NO: 110). In embodiments, the hinge is joined to an Fc region (CH2) having the amino acid sequence SVFLFPPKPKDT (SEQ ID NO: 111). In one embodiment, the hinge region includes the amino acid sequence of an upper, core and lower hinge and comprises EPKSCDKTHTCPPCPAPELLGGP (SEQ ID NO: 112). In embodiments, the hinge region comprises one, two, three or more cysteines that can form at least one, two, three or more interchain disulfide bonds.

[0089] The term “Fc” or “Fc region” as used herein refers to the portion of an antibody heavy chain constant region beginning in or after the hinge region and ending at the C- terminus of the heavy chain. The Fc region comprises at least a portion of the CH2 and CH3 regions and may, or may not, include a portion of the hinge region. Two polypeptide chains each carrying a half Fc region can dimerize to form a full Fc region. In some embodiments, an Fc region can bind Fc cell surface receptors and some proteins of the immune complement system. An Fc region can bind a complement component Clq. An Fc domain can exhibit effector function, including any one or any combination of two or more activities including complement-dependent cytotoxicity (CDC), antibody-dependent cell-mediated cytotoxicity (ADCC), antibody-dependent phagocytosis (ADP), opsonization and/or cell binding. An Fc domain can bind an Fc receptor, including FcyRI (e.g., CD64), FcyRII (e.g, CD32) and/or FcyRIII (e.g., CD16a). In embodiments, the Fc region can include a mutation that increases or decreases any one or any combination of these functions (e.g., an effector-negative Fc region).

[0090] The term “labeled antibody” or related terms as used herein refers to antibodies and their antigen binding portions thereof that are labeled or joined to a detectable label or moiety for detection, wherein the detectable label or moiety is radioactive, colorimetric, antigenic, enzymatic, a detectable bead (such as a magnetic or electrodense (e.g., gold) bead), biotin, streptavidin or protein A. A variety of labels can be employed, including, but not limited to, radionuclides, fluorescers, enzymes, enzyme substrates, enzyme cofactors, enzyme inhibitors and ligands (e.g., biotin, haptens). Any of the anti-B7-H3 antibodies, antigenbinding proteins, and antibody fragments described herein can be unlabeled or can be joined to a detectable label or moiety.

[0091] The “percent identity” or “percent homology” and related terms used herein refers to a quantitative measurement of the similarity between two polypeptide or between two polynucleotide sequences. The percent identity between two polypeptide sequences is a function of the number of identical amino acids at aligned positions that are shared between the two polypeptide sequences, taking into account the number of gaps, and the length of each gap, which may need to be introduced to optimize alignment of the two polypeptide sequences. In a similar manner, the percent identity between two polynucleotide sequences is a function of the number of identical nucleotides at aligned positions that are shared between the two polynucleotide sequences, taking into account the number of gaps, and the length of each gap, which may need to be introduced to optimize alignment of the two polynucleotide sequences. A comparison of the sequences and determination of the percent identity between two polypeptide sequences, or between two polynucleotide sequences, may be accomplished using a mathematical algorithm. For example, the “percent identity” or “percent homology” of two polypeptide or two polynucleotide sequences may be determined by comparing the sequences using the GAP computer program (a part of the GCG Wisconsin Package, version 10.3 (Accelrys, San Diego, Calif.)) using its default parameters. Expressions such as “comprises a sequence with at least X% identity to Y” with respect to a test sequence mean that, when aligned to sequence Y as described above, the test sequence comprises residues identical to at least X% of the residues of Y.

[0092] In embodiments, the amino acid sequence of a test antibody may be similar but not necessarily identical to any of the amino acid sequences of the polypeptides that make up any of the anti-B7-H3 antibodies, or antigen binding protein thereof, described herein. The similarities between the test antibody and the polypeptides can be at least 95%, or at or at least 96% identical, or at least 97% identical, or at least 98% identical, or at least 99% identical, to any of the polypeptides that make up any of the anti-B7-H3 antibodies, or antigen binding protein thereof, described herein. In one embodiment, similar polypeptides can contain amino acid substitutions within a heavy and/or light chain. In one embodiment, the amino acid substitutions comprise one or more conservative amino acid substitutions. A “conservative amino acid substitution” is one in which an amino acid residue is substituted by another amino acid residue having a side chain (R group) with similar chemical properties (e.g., charge or hydrophobicity). In general, a conservative amino acid substitution will not substantially change the functional properties of a protein. In cases where two or more amino acid sequences differ from each other by conservative substitutions, the percent sequence identity or degree of similarity may be adjusted upwards to correct for the conservative nature of the substitution. Means for making this adjustment are well-known to those of skill in the art. See, e.g., Pearson (1994) Methods Mol. Biol. 24: 307-331, herein incorporated by reference in its entirety. Examples of groups of amino acids that have side chains with similar chemical properties include (1) aliphatic side chains: glycine, alanine, valine, leucine and isoleucine; (2) aliphatic -hydroxyl side chains: serine and threonine; (3) amide-containing side chains: asparagine and glutamine; (4) aromatic side chains: phenylalanine, tyrosine, and tryptophan; (5) basic side chains: lysine, arginine, and histidine; (6) acidic side chains: aspartate and glutamate, and (7) sulfur-containing side chains are cysteine and methionine. [0093] Antibodies can be obtained from sources such as serum or plasma that contain immunoglobulins having varied antigenic specificity. If such antibodies are subjected to affinity purification, they can be enriched for a particular antigenic specificity. Such enriched preparations of antibodies usually are made of less than about 10% antibody having specific binding activity for the particular antigen. Subjecting these preparations to several rounds of affinity purification can increase the proportion of antibody having specific binding activity for the antigen. Antibodies prepared in this manner are often referred to as “monospecific.” Monospecfic antibody preparations can be made up of about 10%, 20%, 30%, 40%, 50%, 60%, 70%, 75%, 80%, 85%, 90%, 95%, 97%, 99%, or 99.9% antibody having specific binding activity for the particular antigen. Antibodies can be produced using recombinant nucleic acid technology as described below.

[0094] A “vector” and related terms used herein refers to a nucleic acid molecule (e.g., DNA or RNA) which can be operably linked to foreign genetic material (e.g., nucleic acid transgene). Vectors can be used as a vehicle to introduce foreign genetic material into a cell (e.g., host cell). Vectors can include at least one restriction endonuclease recognition sequence for insertion of the transgene into the vector. Vectors can include at least one gene sequence that confers antibiotic resistance or a selectable characteristic to aid in selection of host cells that harbor a vector-transgene construct. Vectors can be single-stranded or doublestranded nucleic acid molecules. Vectors can be linear or circular nucleic acid molecules. A donor nucleic acid used for gene editing methods employing zinc finger nuclease, TALEN or CRISPR/Cas can be a type of a vector. One type of vector is a “plasmid,” which refers to a linear or circular double stranded extrachromosomal DNA molecule which can be linked to a transgene, and is capable of replicating in a host cell, and transcribing and/or translating the transgene. A viral vector typically contains viral RNA or DNA backbone sequences which can be linked to the transgene. The viral backbone sequences can be modified to disable infection but retain insertion of the viral backbone and the co-linked transgene into a host cell genome. Examples of viral vectors include retroviral, lentiviral, adenoviral, adeno-associated, baculoviral, papovaviral, vaccinia viral, herpes simplex viral and Epstein Barr viral vectors. Certain vectors are capable of autonomous replication in a host cell into which they are introduced (e.g., bacterial vectors comprising a bacterial origin of replication and episomal mammalian vectors). Other vectors (e.g., non-episomal mammalian vectors) are integrated into the genome of a host cell upon introduction into the host cell, and thereby are replicated along with the host genome. [0095] An “expression vector” is a type of vector that can contain one or more regulatory sequences, such as inducible and/or constitutive promoters and enhancers. Expression vectors can include ribosomal binding sites and/or polyadenylation sites. Regulatory sequences direct transcription, or transcription and translation, of a transgene linked to the expression vector which is transduced into a host cell. The regulatory sequence(s) can control the level, timing and/or location of expression of the transgene. The regulatory sequence can, for example, exert its effects directly on the transgene, or through the action of one or more other molecules (e.g., polypeptides that bind to the regulatory sequence and/or the nucleic acid). Regulatory sequences can be part of a vector. Further examples of regulatory sequences are described in, for example, Goeddel, 1990, Gene Expression Technology: Methods in Enzymology 185, Academic Press, San Diego, Calif, and Baron et al., 1995, Nucleic Acids Res. 23:3605-3606. An expression vector can comprise nucleic acids that encode at least a portion of any of the anti-B7-H3 antibodies described herein. [0096] A transgene is “operably linked” to a vector when there is linkage between the transgene and the vector to permit functioning or expression of the transgene sequences contained in the vector. In one embodiment, a transgene is “operably linked” to a regulatory sequence when the regulatory sequence affects the expression (e.g., the level, timing, or location of expression) of the transgene.

[0097] The terms “transfected” or “transformed” or “transduced” or other related terms used herein refer to a process by which exogenous nucleic acid (e.g., transgene) is transferred or introduced into a host cell. A “transfected” or “transformed” or “transduced” host cell is one which has been transfected, transformed or transduced with exogenous nucleic acid

(transgene). The host cell includes the primary subject cell and its progeny. Exogenous nucleic acids encoding at least a portion of any of the anti-B7-H3 antibodies described herein can be introduced into a host cell. Expression vectors comprising at least a portion of any of the anti- B7-H3 antibodies described herein can be introduced into a host cell, and the host cell can express polypeptides comprising at least a portion of the anti-B7-H3 antibody.

[0098] The terms “host cell” or “or a population of host cells” or related terms as used herein refer to a cell (or a population thereof) into which foreign (exogenous or transgene) nucleic acids have been introduced. The foreign nucleic acids can include an expression vector operably linked to a transgene, and the host cell can be used to express the nucleic acid and/or polypeptide encoded by the foreign nucleic acid (transgene). A host cell (or a population thereof) can be a cultured cell or can be extracted from a subject. The host cell (or a population thereof) includes the primary subject cell and its progeny without any regard for the number of passages. Progeny cells may or may not harbor identical genetic material compared to the parent cell. Host cells encompass progeny cells. In embodiments, a host cell describes any cell (including its progeny) that has been modified, transfected, transduced, transformed, and/or manipulated in any way to express an antibody, as disclosed herein. In one example, the host cell (or population thereof) can be introduced with an expression vector operably linked to a nucleic acid encoding the desired antibody, or an antigen binding portion thereof, described herein. Host cells and populations thereof can harbor an expression vector that is stably integrated into the host’s genome or can harbor an extrachromosomal expression vector. In embodiments, host cells and populations thereof can harbor an extrachromosomal vector that is present after several cell divisions or is present transiently and is lost after several cell divisions.

[0099] Transgenic host cells can be prepared using non-viral methods, including well- known designer nucleases including zinc finger nucleases, TALENS or CRISPR/Cas. A transgene can be introduced into a host cell’s genome using genome editing technologies such as zinc finger nuclease. A zinc finger nuclease includes a pair of chimeric proteins each containing a non-specific endonuclease domain of a restriction endonuclease (e.g., FokI ) fused to a DNA-binding domain from an engineered zinc finger motif. The DNA-binding domain can be engineered to bind a specific sequence in the host’s genome and the endonuclease domain makes a double-stranded cut. The donor DNA carries the transgene, for example any of the nucleic acids encoding a CAR or DAR construct described herein, and flanking sequences that are homologous to the regions on either side of the intended insertion site in the host cell’s genome. The host cell’s DNA repair machinery enables precise insertion of the transgene by homologous DNA repair. Transgenic mammalian host cells have been prepared using zinc finger nucleases (U.S. patent Nos. 9,597,357, 9,616,090, 9,816,074 and 8,945,868). A transgenic host cell can be prepared using TALEN (Transcription Activator-Like Effector Nucleases) which are similar to zinc finger nucleases in that they include a non-specific endonuclease domain fused to a DNA-binding domain which can deliver precise transgene insertion. Like zinc finger nucleases, TALEN also introduce a double-strand cut into the host’s DNA. Transgenic host cells can be prepared using CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats). CRISPR employs a Cas endonuclease coupled to a guide RNA for target specific donor DNA integration. The guide RNA includes a conserved multi-nucleotide containing protospacer adjacent motif (PAM) sequence upstream of the gRNA-binding region in the target DNA and hybridizes to the host cell target site where the Cas endonuclease cleaves the double- stranded target DNA. The guide RNA can be designed to hybridize to a specific target site. Similar to zinc finger nuclease and TALEN, the CRISPR/Cas system can be used to introduce site specific insertion of donor DNA having flanking sequences that have homology to the insertion site. Examples of CRISPR/Cas systems used to modify genomes are described for example in U.S. Pat. Nos. 8,697,359, 10,000,772, 9,790,490, and U. S. Patent Application Publication No. US 2018/0346927. In one embodiment, transgenic host cells can be prepared using zinc finger nuclease, TALEN or CRISPR/Cas system, and the host target site can be a TRAC gene (T Cell Receptor Alpha Constant). The donor DNA can include for example any of the nucleic acids encoding a CAR or DAR construct described herein. Electroporation, nucleofection or lipofection can be used to co-deliver into the host cell the donor DNA with the zinc finger nuclease, TALEN or CRISPR/Cas system.

[00100] A host cell can be a prokaryote, for example, E. coli, or it can be a eukaryote, for example, a single-celled eukaryote (e.g., a yeast or other fungus), a plant cell (e.g., a tobacco or tomato plant cell), a mammalian cell (e.g., a human cell, a monkey cell, a hamster cell, a rat cell, a mouse cell, or an insect cell) or a hybridoma. In one embodiment, a host cell can be introduced with an expression vector operably linked to a nucleic acid encoding a desired antibody thereby generating a transfected/transformed host cell which is cultured under conditions suitable for expression of the antibody by the transfected/transformed host cell, and optionally recovering the antibody from the transfected/transformed host cells (e.g., recovery from host cell lysate) or recovery from the culture medium. In one embodiment, host cells comprise non-human cells including CHO, BHK, NS0, SP2/0, and YB2/0. In embodiments, host cells comprise human cells including HEK293, HT-1080, Huh-7 and PER.C6. Examples of host cells include the COS-7 line of monkey kidney cells (ATCC CRL 1651) (see Gluzman et al., 1981, Cell 23: 175), L cells, C127 cells, 3T3 cells (ATCC CCL 163), Chinese hamster ovary (CHO) cells or their derivatives such as Veggie CHO and related cell lines which grow in serum- free media (see Rasmussen et al., 1998, Cytotechnology 28:31) or CHO strain DX-B 11, which is deficient in DHFR (see Urlaub et al., 1980, Proc. Natl. Acad. Sci. USA 77:4216-20), HeLa cells, BHK (ATCC CRL 10) cell lines, the CV 1/EBNA cell line derived from the African green monkey kidney cell line CV 1 (ATCC CCL 70) (see McMahan et al., 1991, EMBO J. 10:2821), human embryonic kidney cells such as 293, 293 EBNA or MSR 293, human epidermal A431 cells, human Colo 205 cells, other transformed primate cell lines, normal diploid cells, cell strains derived from in vitro culture of primary tissue, primary explants, HL-60, U937, HaK or Jurkat cells. In one embodiment, host cells include lymphoid cells such as Y0, NS0 or Sp20. In embodiments, a host cell is a mammalian host cell, but is not a human host cell. Typically, a host cell is a cultured cell that can be transformed or transfected with a polypeptide-encoding nucleic acid, which can then be expressed in the host cell. The phrase “transgenic host cell” or “recombinant host cell” can be used to denote a host cell that has been transformed or transfected with a nucleic acid to be expressed. A host cell also can be a cell that comprises the nucleic acid but does not express it at a desired level unless a regulatory sequence is introduced into the host cell such that it becomes operably linked with the nucleic acid. It is understood that the term host cell refers not only to the particular subject cell but also to the progeny or potential progeny of such a cell. Because certain modifications may occur in succeeding generations due to, e.g., mutation or environmental influence, such progeny may not, in fact, be identical to the parent cell, but are still included within the scope of the term as used herein.

[00101] Polypeptides of the present disclosure (e.g., antibodies and antigen binding proteins) can be produced using any methods known in the art. In one example, the polypeptides are produced by recombinant nucleic acid methods by inserting a nucleic acid sequence (e.g., DNA) encoding the polypeptide into a recombinant expression vector which is introduced into a host cell and expressed by the host cell under conditions promoting expression.

[00102] General techniques for recombinant nucleic acid manipulations are described for example in Sambrook et al., in Molecular Cloning: A Laboratory Manual, Vols. 1-3, Cold Spring Harbor Laboratory Press, 2 ed., 1989, or F. Ausubel et al., in Current Protocols in Molecular Biology (Green Publishing and Wiley-Interscience: New York, 1987) and periodic updates, herein incorporated by reference in their entireties. The nucleic acid (e.g., DNA) encoding the polypeptide is operably linked to an expression vector carrying one or more suitable transcriptional or translational regulatory elements derived from mammalian, viral, or insect genes. Such regulatory elements include a transcriptional promoter, an optional operator sequence to control transcription, a sequence encoding suitable mRNA ribosomal binding sites, and sequences that control the termination of transcription and translation. The expression vector can include an origin or replication that confers replication capabilities in the host cell. The expression vector can include a gene that confers selection to facilitate recognition of transgenic host cells (e.g., transformants).

[00103] The recombinant DNA can also encode any type of protein tag sequence that may be useful for purifying the protein. Examples of protein tags include but are not limited to a histidine tag, a FLAG tag, a myc tag, an HA tag, or a GST tag. Appropriate cloning and expression vectors for use with bacterial, fungal, yeast, and mammalian cellular hosts can be found in Cloning Vectors: A Laboratory Manual, (Elsevier, N.Y., 1985).

[00104] The expression vector construct can be introduced into the host cell using a method appropriate for the host cell. A variety of methods for introducing nucleic acids into host cells are known in the art, including, but not limited to, electroporation; transfection employing calcium chloride, rubidium chloride, calcium phosphate, DEAE-dextran, or other substances; viral transfection; non-viral transfection; microprojectile bombardment; lipofection; and infection (e.g., where the vector is an infectious agent). Suitable host cells include prokaryotes, yeast, mammalian cells, or bacterial cells.

[00105] Suitable bacteria include gram negative or gram positive organisms, for example, E. coli or Bacillus spp. Yeast, preferably from the Saccharomyces species, such as S. cerevisiae, may also be used for production of polypeptides. Various mammalian or insect cell culture systems can also be employed to express recombinant proteins.

Baculovirus systems for production of heterologous proteins in insect cells are reviewed by Luckow and Summers, (Bio/Technology, 6:47, 1988). Examples of suitable mammalian host cell lines include endothelial cells, COS-7 monkey kidney cells, CV-1, L cells, C127, 3T3, Chinese hamster ovary (CHO), human embryonic kidney cells, HeLa, 293, 293T, and BHK cell lines. Purified polypeptides are prepared by culturing suitable host/vector systems to express the recombinant proteins. For many applications, the small size of many of the polypeptides disclosed herein would make expression in E. coli as the preferred method for expression. The protein is then purified from culture media or cell extracts. Any of the anti- B7-H3 antibodies, antigen binding proteins, or antigen binding portions thereof, can be expressed by transgenic host cells.

[00106] Antibodies and antigen binding proteins disclosed herein can also be produced using cell-translation systems. For such purposes the nucleic acids encoding the polypeptide must be modified to allow in vitro transcription to produce mRNA and to allow cell-free translation of the mRNA in the particular cell-free system being utilized (eukaryotic such as a mammalian or yeast cell-free translation system or prokaryotic such as a bacterial cell-free translation system.

[00107] Nucleic acids encoding any of the various polypeptides disclosed herein may be synthesized chemically. Codon usage may be selected so as to improve expression in a cell. Such codon usage will depend on the cell type selected. Specialized codon usage patterns have been developed for E. coli and other bacteria, as well as mammalian cells, plant cells, yeast cells and insect cells. See for example: Mayfield et al., 2003, Proc. Natl. Acad. Sci. USA. 100(2):438-42; Sinclair et al., 2002, Protein Expr. Purif. ( 1):96- 105; Connell N D., 2001, Curr. Opin. Biotechnol. 12(5):446-9; Makrides et al., 1996, Microbiol.

Rev. 60(3):512-38; and Sharp et al., 1991, Yeast. 7(7):657-78.

[00108] Antibodies and antigen binding proteins described herein can also be produced by chemical synthesis (e.g., by the methods described in Solid Phase Peptide Synthesis, 2nd ed., 1984, The Pierce Chemical Co., Rockford, Ill.). Modifications to the protein can also be produced by chemical synthesis.

[00109] Antibodies and antigen binding proteins described herein can be purified by isolation/purification methods for proteins generally known in the field of protein chemistry. Non-limiting examples include extraction, recrystallization, salting out (e.g., with ammonium sulfate or sodium sulfate), centrifugation, dialysis, ultrafiltration, adsorption chromatography, ion exchange chromatography, hydrophobic chromatography, normal phase chromatography, reversed-phase chromatography, gel filtration, gel permeation chromatography, affinity chromatography, electrophoresis, countercurrent distribution or any combinations of these. After purification, polypeptides may be exchanged into different buffers and/or concentrated by any of a variety of methods known to the art, including, but not limited to, filtration and dialysis.

[00110] The purified antibodies and antigen binding proteins described herein are preferably at least 65% pure, at least 75% pure, at least 85% pure, more preferably at least 95% pure, and most preferably at least 98% pure. Regardless of the exact numerical value of the purity, the polypeptide is sufficiently pure for use as a pharmaceutical product. Any of the anti-B7-H3 antibodies, or antigen binding protein thereof, described herein can be expressed by transgenic host cells and then purified to about 65-98% purity or high level of purity using any art-known method.

[00111] In certain embodiments, the antibodies and antigen binding proteins herein can further comprise post-translational modifications. Exemplary post-translational protein modifications include phosphorylation, acetylation, methylation, ADP-ribosylation, ubiquitination, glycosylation, carbonylation, sumoylation, biotinylation or addition of a polypeptide side chain or of a hydrophobic group. As a result, the modified polypeptides may contain non-amino acid elements, such as lipids, poly- or mono-saccharide, and phosphates. A preferred form of glycosylation is sialylation, which conjugates one or more sialic acid moieties to the polypeptide. Sialic acid moieties improve solubility and serum half-life while also reducing the possible immunogenicity of the protein. See Raju et al., 2001, Biochemistry. 31; 40(30):8868-76. [00112] In embodiments, the antibodies and antigen binding proteins described herein can be modified to increase solubility, e.g., by linking the antibodies and antigen binding proteins to non-proteinaceous polymers. In one embodiment, the non-proteinaceous polymer comprises polyethylene glycol (“PEG”), polypropylene glycol, or polyoxyalkylenes, in the manner as set forth in U.S. Pat. Nos. 4,640,835; 4,496,689; 4,301,144; 4,670,417; 4,791,192 or 4,179,337.

[00113] PEG is a water soluble polymer that is commercially available or can be prepared by ring-opening polymerization of ethylene glycol according to methods well known in the art (Sandler and Karo, Polymer Synthesis, Academic Press, New York, Vol. 3, pages 138- 161). The term “PEG” is used broadly to encompass any polyethylene glycol molecule, without regard to size or to modification at an end of the PEG, and can be represented by the formula: X— O(CH₂CH₂O)_n— CH2CH2OH (1), where n is 20 to 2300 and X is H or a terminal modification, e.g., a C1-4 alkyl. In embodiments, the PEG terminates on one end with hydroxy or methoxy, i.e., X is H or CH3 (“methoxy PEG”). A PEG can contain further chemical groups which are necessary for binding reactions; which results from the chemical synthesis of the molecule; or which is a spacer for optimal distance of parts of the molecule. In addition, such a PEG can consist of one or more PEG side-chains which are linked together. PEGs with more than one PEG chain are called multiarmed or branched PEGs. Branched PEGs can be prepared, for example, by the addition of polyethylene oxide to various polyols, including glycerol, pentaery thriol, and sorbitol. For example, a four-armed branched PEG can be prepared from pentaerythriol and ethylene oxide. Branched PEG are described in, for example, EP-A 0 473 084 and U.S. Pat. No. 5,932,462. One form of PEGs includes two PEG side-chains (PEG2) linked via the primary amino groups of a lysine (Monfardini et al., 1995, Bioconjugate Chem. 6: 62-69).

[00114] The serum clearance rate of PEG-modified polypeptide may be modulated (e.g., increased or decreased) by about 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, or even 90%, relative to the clearance rate of the unmodified antibodies and antigen binding proteins binding polypeptides. The PEG-modified antibodies and antigen binding proteins may have a half-life (ti/2) which is enhanced relative to the half-life of the unmodified polypeptide. The half-life of PEG-modified polypeptide may be enhanced by at least 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%, 125%, 150%, 175%, 200%, 250%, 300%, 400% or 500%, or even by 1000% relative to the half-life of the unmodified antibodies and antigen binding proteins. In some embodiments, the protein half-life is determined in vitro, such as in a buffered saline solution or in serum. In other embodiments, the protein half-life is an in vivo half-life, such as the half-life of the protein in the serum or other bodily fluid of an animal. [00115] The present disclosure provides pharmaceutical compositions comprising any of the anti-B7-H3 antibodies, or antigen binding protein thereof, described herein in an admixture with a pharmaceutically-acceptable excipient. An excipient encompasses carriers, stabilizers and excipients. Excipients or pharmaceutically acceptable excipients includes for example inert diluents or fillers (e.g., sucrose and sorbitol), lubricating agents, glidants, and anti-adhesives (e.g., magnesium stearate, zinc stearate, stearic acid, silicas, hydrogenated vegetable oils, or talc). Additional examples include buffering agents, stabilizing agents, preservatives, non-ionic detergents, anti-oxidants and isotonifiers.

[00116] Pharmaceutical compositions and methods for preparing them are well known in the art and are found, for example, in “Remington: The Science and Practice of Pharmacy” (20th ed., ed. A. R. Gennaro A R., 2000, Lippincott Williams & Wilkins, Philadelphia, Pa.). Pharmaceutical compositions can be formulated for parenteral administration may, and can for example, contain excipients, sterile water, saline, polyalkylene glycols such as polyethylene glycol, oils of vegetable origin, or hydrogenated napthalenes. Biocompatible, biodegradable lactide polymer, lactide/glycolide copolymer, or polyoxyethylenepolyoxypropylene copolymers may be used to control the release of the antibody (or antigen binding protein thereof) described herein. Nanoparticulate formulations (e.g., biodegradable nanoparticles, solid lipid nanoparticles, liposomes) may be used to control the biodistribution of the antibody (or antigen binding protein thereof). Other potentially useful parenteral delivery systems include ethylene-vinyl acetate copolymer particles, osmotic pumps, implantable infusion systems, and liposomes. The concentration of the antibody (or antigen binding protein thereof) in the formulation varies depending upon a number of factors, including the dosage of the drug to be administered, and the route of administration.

[00117] Any of the anti-B7-H3 antibodies (or antigen binding portions thereof) may be administered as a pharmaceutically acceptable salt, such as non-toxic acid addition salts or metal complexes that are commonly used in the pharmaceutical industry. Examples of acid addition salts include organic acids such as acetic, lactic, pamoic, maleic, citric, malic, ascorbic, succinic, benzoic, palmitic, suberic, salicylic, tartaric, methanesulfonic, toluenesulfonic, or trifluoroacetic acids or the like; polymeric acids such as tannic acid, carboxymethyl cellulose, or the like; and inorganic acid such as hydrochloric acid, hydrobromic acid, sulfuric acid phosphoric acid, or the like. Metal complexes include zinc, iron, and the like. In one example, the antibody (or antigen binding portions thereof) is formulated in the presence of sodium acetate to increase thermal stability.

[00118] Any of the anti-B7-H3 antibodies (or antigen binding portions thereof) may be administered as a pharmaceutically acceptable salt, such as non-toxic acid addition salts or metal complexes that are commonly used in the pharmaceutical industry. Examples of acid addition salts include organic acids such as acetic, lactic, pamoic, maleic, citric, malic, ascorbic, succinic, benzoic, palmitic, suberic, salicylic, tartaric, methanesulfonic, toluenesulfonic, or trifluoroacetic acids or the like; polymeric acids such as tannic acid, carboxymethyl cellulose, or the like; and inorganic acid such as hydrochloric acid, hydrobromic acid, sulfuric acid phosphoric acid, or the like. Metal complexes include zinc, iron, and the like. In one example, the antibody (or antigen binding portions thereof) is formulated in the presence of sodium acetate to increase thermal stability.

[00119] Any of the anti-B7-H3 antibodies (or antigen binding portions thereof) may be formulated for oral use include tablets containing the active ingredient(s) in a mixture with non-toxic pharmaceutically acceptable excipients. Formulations for oral use may also be provided as chewable tablets, or as hard gelatin capsules wherein the active ingredient is mixed with an inert solid diluent, or as soft gelatin capsules wherein the active ingredient is mixed with water or an oil medium.

[00120] The term “subject” as used herein refers to human and non-human animals, including vertebrates, mammals and non-mammals. In one embodiment, the subject can be human. In other embodiments, the subject can be a non-human primate, simian, ape, murine (e.g., mice and rats), bovine, porcine, equine, canine, feline, caprine, lupine, ranine or piscine. [00121] The term “administering”, “administered” and grammatical variants refers to the physical introduction of an agent to a subject, using any of the various methods and delivery systems known to those skilled in the art. Exemplary routes of administration for the formulations disclosed herein include intravenous, intramuscular, subcutaneous, intraperitoneal, spinal or other parenteral routes of administration, for example by injection or infusion. 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, intramuscular, intraarterial, intrathecal, intralymphatic, intralesional, intracapsular, intraorbital, intracardiac, intradermal, intraperitoneal, transtracheal, subcutaneous, subcuticular, intraarticular, subcapsular, subarachnoid, intraspinal, epidural and intrasternal injection and infusion, as well as in vivo electroporation. In some embodiments, the formulation is administered via a non-parenteral route, e.g., orally. Other non-parenteral routes include a topical, epidermal or mucosal route of administration, for example, intranasally, 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. Any of the anti-B7-H3 antibodies described herein (or antigen binding protein thereof) can be administered to a subject using art-known methods and delivery routes.

[00122] The terms “effective amount”, “therapeutically effective amount” or “effective dose” or related terms may be used interchangeably and refer to an amount of antibody or an antigen binding protein (e.g., any of the anti-B7-H3 antibodies described herein or antigen binding protein thereof) that when administered to a subject, is sufficient to effect a measurable improvement or prevention of a disease or disorder associated with tumor or cancer antigen expression. Therapeutically effective amounts of antibodies provided herein, when used alone or in combination, will vary depending upon the relative activity of the antibodies and combinations (e.g. , in inhibiting cell growth) and depending upon the subject and disease condition being treated, the weight and age and sex of the subject, the severity of the disease condition in the subject, the manner of administration and the like, which can readily be determined by one of ordinary skill in the art.

[00123] In embodiments, a therapeutically effective amount will depend on certain aspects of the subject to be treated and the disorder to be treated and may be ascertained by one skilled in the art using known techniques. In general, the polypeptide is administered at about 0.01 g/kg to about 50 mg/kg per day, preferably 0.01 mg/kg to about 30 mg/kg per day, most preferably 0.1 mg/kg to about 20 mg/kg per day. The polypeptide may be administered daily (e.g., once, twice, three times, or four times daily) or preferably less frequently (e.g., weekly, every two weeks, every three weeks, monthly, or quarterly). In addition, as is known in the art, adjustments for age as well as the body weight, general health, sex, diet, time of administration, drug interaction, and the severity of the disease may be necessary.

[00124] The term “B7-H3 expressing tumor,” as used herein, refers to a tumor which expresses B7-H3 protein. In embodiments, B7-H3 expression in a tumor is determined using immunohistochemical staining of tumor cell membranes, where any immunohistochemical staining above background level in a tumor sample indicates that the tumor is a B7-H3 expressing tumor. Methods for detecting expression of B7-H3 in a tumor are known in the art and include immunohistochemical assays. In any of the disclosed embodiments relating to medical use of a disclosed antibody or antigen binding protein for treatment of a condition involving a tumor, the tumor can be a B7-H3 expressing tumor. [00125] The terms “overexpress,” “overexpression,” or “overexpressed” interchangeably refer to a gene that is transcribed or translated at a detectably greater level, usually in a cancer cell, in comparison to a normal cell. Overexpression therefore refers to both overexpression of protein and RNA (due to increased transcription, post transcriptional processing, translation, post translational processing, altered stability, and altered protein degradation), as well as local overexpression due to altered protein traffic patterns (increased nuclear localization), and augmented functional activity, e.g., as in an increased enzyme hydrolysis of substrate. Thus, overexpression refers to either protein or RNA levels. Overexpression can also be by 50%, 60%, 70%, 80%, 90% or more in comparison to a normal cell or comparison cell. In certain embodiments, the anti-B7-H3 antibodies are used to treat solid tumors likely to overexpress B7-H3.

[00126] The term “combination therapy” or “combination” in the context of a therapeutic method (e.g., a treatment method), as used herein, refers to the administration of two or more therapeutic substances, e.g., an anti-B7-H3 antibody and an additional therapeutic agent. The additional therapeutic agent may be administered concomitant with, prior to, or following the administration of the anti-B7-H3 antibody.

[00127] The present disclosure provides methods for treating a subject having a disease associated with expression or over-expression of B7-H3. In embodiments, the disease is an autoimmune disease. In embodiments, the disease is HIV. In embodiments, the disease is an inflammatory disease. In embodiments, the disease is an infectious disease. In embodiments the disease comprises cancer or tumor cells expressing the tumor-associated antigens. In embodiments, the cancer or tumor includes cancer of the breast, prostate, colon, liver, ovary, bladder, pancreas, lung (including non-small cell lung and small cell lung), esophagus, stomach, skin, and kidney.

[00128] In embodiments, the cancer is non-small cell lung cancer, small cell lung cancer, renal cancer, urothelial cancer, colon cancer, prostate cancer, glioblastoma multiforme, ovarian cancer, pancreatic cancer (Johnson, K.A. et al, 2007, Analytical Biochemistry, 360:75 - 83; Winter, G. et al., 1994, Annu. Rev. Immunol., 12:433 - 455; Ashraf, S.Q. et al., 2009, British Journal Of Cancer 101(10): 1758 - 1768; Barbara, B. M. and Stanley, M. S., 1980, “Selected Methods in Cellular Immunology”; W. H. Freeman and company; Yamato, I. et al., 2009, British Journal Of Cancer 101(10): 1709 - 1716; Sun, J. et al., 2010, Cancer Immunology, Immunotherapy 59: 1163 - 1171; Roth, T.J. et al., 2007, Cancer Research 67: 7893 - 7900; Carmen, S. et al., 2002, Briefings In Functional Genomics and Proteomics 1(2): 189 - 203). In prostate cancer, it is reported that B7-H3 expression intensity is positively correlated with clinicopathological malignancy such as tumor volume, extrapro static invasion, and Grimson score, and with cancer progression. (Yamato, I. et ah, 2009, British Journal of Cancer 101(10): 1709 - 1716). Similarly, B7-H3 expression and recurrence-free survival rate are negatively correlated in glioblastoma multiforme (Sun, J. et ah, 2010, Cancer Immunology, Immunotherapy 59: 1163 - 1171). In pancreatic cancer, B7-H3 expression, lymph node metastasis and pathological progression Correlation. (Carmen, S. et ah, 2002, Briefings in Functional Genomics and Proteomics 1(2): 189 - 203). In ovarian cancer, B7-H3 expression is correlated with lymph node metastasis and pathological progression.

[00129] In embodiments, the cancers include, but are not limited to, carcinoma, lymphoma, blastoma, sarcoma, and leukemia or lymphoid malignancies. In embodiments, the cancers include glioblastoma, glioma, neuroblastoma, melanoma, hepatocellular carcinoma, clear cell renal cell carcinoma, acute myeloid leukemia (AML), non- Hodgkin's lymphoma (NHL), colorectal cancer, oral cancer, head and neck cancer, breast cancer (e.g., triple negative breast cancer), squamous cell tumors, hypopharyngeal squamous cell carcinoma, squamous cell carcinoma (e.g., squamous cell lung cancer or squamous cell head and neck cancer), urothelial cell carcinoma, gastric cancer, anal cancer, endometrial cancer, and vulvar cancer. In embodiments, the cancer is a metastatic cancer, refractory cancer, or recurrent cancer.

[00130] The present disclosure provides B7-H3 binding proteins, particularly anti-B7-H3 antibodies, or antigen binding portions thereof, that specifically bind B7-H3 and uses thereof. In embodiments, the B7-H3 binding proteins bind an epitope of B7-H3. B7-H3 is a type I transmembrane protein encoded by chromosome 9 in mice and 15 in humans (e.g., UniProt Q5ZPR3-1). The extracellular domain is composed of a single pair of immunoglobulin variable domain and immunoglobulin constant domain in mice (2IgB7-H3 isoform) and two identical pairs in human (4IgB7-H3 isoform) due to exon duplication. The intracellular tail of B7-H3 is short and has no known signaling motif.

[00131] Various aspects of the anti-B7-H3 antibodies relate to antibody fragments, singlechain antibodies, pharmaceutical compositions, nucleic acids, recombinant expression vectors, host cells, and methods for preparing and using such anti-B7-H3 antibodies. Methods for using the anti-B7-H3 antibodies include in vitro and in vivo methods for binding B7-H3, detecting B7-H3 and treating diseases associated with B7-H3 expression.

[00132] The present disclosure provides antigen binding proteins that bind specifically to a B7-H3 polypeptide (e.g., antigen target) or fragment of the B7-H3 polypeptide. In embodiments, the B7-H3 target antigen comprises a naturally-occurring polypeptide (e.g., UniProt accession No. Q5ZPR3-1) having a wild-type or polymorphic or mutant amino acid sequence. The B7-H3 target antigen can be prepared by recombinant methods or can be chemically synthesized. The B7-H3 target antigen can be in soluble form or membranebound form (e.g., expressed by a cell or phage).

[00133] In embodiments, the B7-H3 target antigen is expressed by a cell, for example a cancer or non-cancer cell line that naturally expresses B7-H3 or is engineered to express B7- H3, such as A549, U-2197, ASC TERT1, CACO-2, or HHSteC. Cell lines that do not express B7-H3 are not expected to bind an anti-B7-H3 antibody, such as for example Jurkat, Daudi, or K562 cell lines, or B7-H3 KO cell lines. The B7-H3 target antigen can be a fusion protein or conjugated for example with a detectable moiety such as a fluorophore. The B7-H3 target antigen can be a fusion protein or conjugated with an affinity tag, such as for example a His-tag. In embodiments, human B7-H3 target antigen comprises the amino acid sequence of SEQ ID NO:1 (e.g., UniProt accession No. Q5ZPR3-1) or SEQ ID NO:2 (e.g., recombinant his-tagged human B7-H3 from Sino Biologicals Cat. No. 11188-H08H-50).

[00134] In embodiments, the antigen-binding protein is an IgG, IgA, IgD, IgE, or IgM antibody having one or more mutations in the Fc region, for example one or more mutations that decreases antibody dependent enhancement (ADE) and/or one or more mutations that increases antibody half-life. Mutations that reduce or eliminate interaction of the Fc region of antibody with its receptor (e.g., FcyRs) on such cells can reduce or eliminate ADE. For example, an antigen-binding protein as provided herein can be an IgGl or IgG4 antibody having an ADE-reducing mutation, such as the LALA mutation, in the Fc region, or can be single chain antibody (ScFv) that optionally includes an Fc region that can optionally include an ADE-reducing mutation, such as the LALA mutation. In further embodiments, an antigenbinding protein as provided herein can be a Fab, Fab’, or F(ab’)2 antibody fragment.

[00135] The present disclosure provides a fully human antibody of an IgG class that binds to a B7-H3 polypeptide. In embodiments, the anti-B7-H3 antibody comprises a heavy chain variable region having at least 95% sequence identity, or at least 96% sequence identity, or at least 97% sequence identity, or at least 98% sequence identity, or at least 99% sequence identity to the amino acid sequence of SEQ ID NO: 10, SEQ ID NO:20, SEQ ID NO:30, SEQ ID NO:40, SEQ ID NO:50, SEQ ID NO:60, SEQ ID NO:70, SEQ ID NO:80, SEQ ID NO:90, or SEQ ID NO: 100, or combinations thereof; and/or the anti-B7-H3 antibody comprises a light chain variable region having 95% sequence identity, or at least 96% sequence identity, or at least 97% sequence identity, or at least 98% sequence identity, or at least 99% sequence identity to the amino acid sequence of SEQ ID NO: 11, SEQ ID NO:21, SEQ ID N0:31, SEQ ID N0:41, SEQ ID N0:51, SEQ ID N0:61, SEQ ID N0:71, SEQ ID N0:81, SEQ ID N0:91, or SEQ ID NO:101, or combinations thereof. In embodiments, the anti-B7-H3 antibody comprises an IgGl, IgG2, IgG3 or IgG4 class antibody. In one embodiment, the anti-B7-H3 antibody comprises an IgGl or IgG4 class antibody. In embodiments, the anti-B7-H3 antibody comprises an IgGl class antibody. In embodiments, the anti-B7-H3 antibody comprises an IgG4 class antibody. In embodiments, the IgGl class antibody can have a mutation in the Fc region selected from L234A or L235A. In embodiments, the mutation in the Fc region can include the mutations L234A and L235A (LALA). In embodiments, the mutation in the Fc region is a LA mutation or two LALA mutations. In embodiments the LALA mutations in the Fc region reduce the effector function of the anti-TIGIT antibody relative to anti-TIGIT antibody without LALA mutations in the Fc region.

[00136] In embodiments, the anti-B7-H3 antibody, or fragment thereof, comprises an antigen binding portion that binds an epitope of a B7-H3 target antigen (polypeptide) with a binding affinity (KD) of 10’⁶ M or less, 10’⁷ M or less, 10’⁸ M or less, 10’⁹ M or less, or IO’¹⁰ M or less (see FIG. 1A and Table 2). In embodiments, the anti-B7-H3 antibody, or fragment thereof, described herein, comprises an antigen binding portion that binds an epitope of a B7- H3 target antigen with a similar binding affinity whether or not the antibody includes the mutations L234A and L235A in the Fc region (see FIGS. 14 and 15). In embodiments, the binding affinity of the anti-B7-H3 antibody, or fragment thereof, described herein, to a B7- H3 target antigen is essentially the same for the wild type and the mutated antibody, wherein the mutation is L234A and L235A in the Fc region.

[00137] In embodiments, the B7-H3 antigen comprises a cell surface B7-H3 antigen or a soluble B7-H3 antigen. In embodiments, the B7-H3 antigen comprises an extracellular portion of a cell surface B7-H3 antigen. In embodiments, the B7-H3 antigen comprises a human or non-human B7-H3 antigen. In embodiments, the B7-H3 antigen is expressed by a human or non-human cell. In embodiments, the anti-B7-H3 antibody binds a human B7-H3 expressed by an antigen-presenting cell (APC), macrophage, or expressed by a human tumor cell (such as clear cell renal carcinoma and colorectal carcinoma). In embodiments, binding between the anti-B7-H3 antibody, or fragment thereof, can be detected and measured using surface plasmon resonance, flow cytometry and/or ELISA.

[00138] The term “cross-reacts,” as used herein, refers to the ability of an antibody described herein to bind to B7-H3 from a different species. The present disclosure provides an anti-B7-H3 antibody which binds an epitope of B7-H3 from a human, or can bind (e.g., cross-reactivity) with an epitope of B7-H3 (e.g., homologous antigen) from any one or any combination of non-human animals such as mouse, rat, goat, rabbit, hamster and/or monkey (e.g., cynomolgus).

[00139] In embodiments, the anti-B7-H3 antibody or antigen-binding fragment binds mouse B7-H3 with a binding affinity KD of 10’⁵ M or less, or 10’⁶ M or less, or 10’⁷ M or less, or 10’⁸ M or less, or 10’⁹ M or less, or IO ¹⁰ M or less. In embodiments, the anti-B7-H3 antibody or antigen-binding fragment binds cynomolgus B7-H3 with a binding affinity KD of IO ⁵ M or less, or 10’⁶ M or less, or 10’⁷ M or less, or 10’⁸ M or less, or 10’⁹ M or less, or 10' ¹⁰ M or less.

[00140] In embodiments, cynomolgus B7-H3 is commercially-available from Sino Biologicals (catalog # 90806-C08H-20). In embodiments, mouse B7-H3 is commercially- available from Sino Biologicals (catalog # 50973-M08H-50). In embodiments, human B7-H3 is commercially-available from Sino Biologicals (catalog # 11188-H08H-50).

[00141] In embodiments, the anti-B7-H3 antibody has enhanced thermostability. In embodiments, the anti-B7-H3 antibody has T_m of at least 30°C, or at least 35°C, or at least 40°C, or at least 45°C, or at least 50°C, or at least 55°C, or at least 60°C, or at least 65°C, or at least 70°C, or at least 75°C, or at least 80°C, or at least 85°C, or at least 90°C (for example, see FIG. 4).

Detailed Description of Certain Embodiments

[00142] The present disclosure provides an anti-B7-H3 antigen-binding protein or fully human anti-B7-H3 antibody, or an antigen-binding fragment thereof, comprising a heavy chain variable region having a heavy chain complementarity determining region 1 (CDR1) having the amino acid sequence of SEQ ID NO: 12, a heavy chain CDR2 having the amino acid sequence of SEQ ID NO: 13, and a heavy chain CDR3 having the amino acid sequence of SEQ ID NO: 14, and a light chain CDR1 having the amino acid sequence of SEQ ID NO: 15, a light chain CDR2 having the amino acid sequence of SEQ ID NO: 16, and a light chain CDR3 having the amino acid sequence of SEQ ID NO: 17 (herein called VA).

[00143] The present disclosure provides an anti-B7-H3 antigen-binding protein or fully human anti-B7-H3 antibody, or an antigen-binding fragment thereof, comprising a heavy chain CDR1 having the amino acid sequence of SEQ ID NO:22, a heavy chain CDR2 having the amino acid sequence of SEQ ID NO:23, and a heavy chain CDR3 having the amino acid sequence of SEQ ID NO:24, and a light chain CDR1 having the amino acid sequence of SEQ ID NO:25, a light chain CDR2 having the amino acid sequence of SEQ ID NO:26, and a light chain CDR3 having the amino acid sequence of SEQ ID NO:27 (herein called B3-A6). [00144] The present disclosure provides an anti-B7-H3 antigen-binding protein or fully human anti-B7-H3 antibody, or an antigen-binding fragment thereof, comprising a heavy chain CDR1 having the amino acid sequence of SEQ ID NO:32, a heavy chain CDR2 having the amino acid sequence of SEQ ID NO:33, and a heavy chain CDR3 having the amino acid sequence of SEQ ID NO:34, and a light chain CDR1 having the amino acid sequence of SEQ ID NO:35, a light chain CDR2 having the amino acid sequence of SEQ ID NO:36, and a light chain CDR3 having the amino acid sequence of SEQ ID NO:37 (herein called B3-D1).

[00145] The present disclosure provides an anti-B7-H3 antigen-binding protein or fully human anti-B7-H3 antibody, or an antigen-binding fragment thereof, comprising a heavy chain CDR1 having the amino acid sequence of SEQ ID NO:42, a heavy chain CDR2 having the amino acid sequence of SEQ ID NO:43, and a heavy chain CDR3 having the amino acid sequence of SEQ ID NO:44, and a light chain CDR1 having the amino acid sequence of SEQ ID NO:45, a light chain CDR2 having the amino acid sequence of SEQ ID NO:46, and a light chain CDR3 having the amino acid sequence of SEQ ID NO:47 (herein called B3-2D1).

[00146] The present disclosure provides an anti-B7-H3 antigen-binding protein or fully human anti-B7-H3 antibody, or an antigen-binding fragment thereof, comprising a heavy chain CDR1 having the amino acid sequence of SEQ ID NO:52, a heavy chain CDR2 having the amino acid sequence of SEQ ID NO:53, and a heavy chain CDR3 having the amino acid sequence of SEQ ID NO:54, and a light chain CDR1 having the amino acid sequence of SEQ ID NO:55, a light chain CDR2 having the amino acid sequence of SEQ ID NO:56, and a light chain CDR3 having the amino acid sequence of SEQ ID NO:57 (herein called B3-2E3).

[00147] The present disclosure provides an anti-B7-H3 antigen-binding protein or fully human anti-B7-H3 antibody, or an antigen-binding fragment thereof, comprising a heavy chain CDR1 having the amino acid sequence of SEQ ID NO:62, a heavy chain CDR2 having the amino acid sequence of SEQ ID NO:63, and a heavy chain CDR3 having the amino acid sequence of SEQ ID NO:64, and a light chain CDR1 having the amino acid sequence of SEQ ID NO:65, a light chain CDR2 having the amino acid sequence of SEQ ID NO:66, and a light chain CDR3 having the amino acid sequence of SEQ ID NO:67 (herein called B3-2G11). [00148] The present disclosure provides an anti-B7-H3 antigen-binding protein or fully human anti-B7-H3 antibody, or an antigen-binding fragment thereof, comprising a heavy chain CDR1 having the amino acid sequence of SEQ ID NO:72, a heavy chain CDR2 having the amino acid sequence of SEQ ID NO:73, and a heavy chain CDR3 having the amino acid sequence of SEQ ID NO:74, and a light chain CDR1 having the amino acid sequence of SEQ ID NO: 75, a light chain CDR2 having the amino acid sequence of SEQ ID NO:76, and a light chain CDR3 having the amino acid sequence of SEQ ID NO:77 (herein called B3-2H1). [00149] The present disclosure provides an anti-B7-H3 antigen-binding protein or fully human anti-B7-H3 antibody, or an antigen-binding fragment thereof, comprising a heavy chain CDR1 having the amino acid sequence of SEQ ID NO:82, a heavy chain CDR2 having the amino acid sequence of SEQ ID NO:83, and a heavy chain CDR3 having the amino acid sequence of SEQ ID NO:84, and a light chain CDR1 having the amino acid sequence of SEQ ID NO:85, a light chain CDR2 having the amino acid sequence of SEQ ID NO:86, and a light chain CDR3 having the amino acid sequence of SEQ ID NO:87 (herein called B3-4A1). [00150] The present disclosure provides an anti-B7-H3 antigen-binding protein or fully human anti-B7-H3 antibody, or an antigen-binding fragment thereof, comprising a heavy chain CDR1 having the amino acid sequence of SEQ ID NO:92, a heavy chain CDR2 having the amino acid sequence of SEQ ID NO:93, and a heavy chain CDR3 having the amino acid sequence of SEQ ID NO:94, and a light chain CDR1 having the amino acid sequence of SEQ ID NO:95, a light chain CDR2 having the amino acid sequence of SEQ ID NO:96, and a light chain CDR3 having the amino acid sequence of SEQ ID NO:97 (herein called B3-4F7). [00151] The present disclosure provides an anti-B7-H3 antigen-binding protein or fully human anti-B7-H3 antibody, or an antigen-binding fragment thereof, comprising a heavy chain CDR1 having the amino acid sequence of SEQ ID NO: 102, a heavy chain CDR2 having the amino acid sequence of SEQ ID NO: 103, and a heavy chain CDR3 having the amino acid sequence of SEQ ID NO: 104, and a light chain CDR1 having the amino acid sequence of SEQ ID NO: 105, a light chain CDR2 having the amino acid sequence of SEQ ID NO: 106, and a light chain CDR3 having the amino acid sequence of SEQ ID NO: 107 (herein called B3-5A6).

[00152] The present disclosure provides a fully human antibody that binds B7-H3 wherein the antibody comprises both heavy and light chains, wherein the heavy/light chain variable region amino acid sequences have at least 95% sequence identity, or at least 96% sequence identity, or at least 97% sequence identity, or at least 98% sequence identity, or at least 99% sequence identity to any of the following amino acid sequence sets: SEQ ID NOS: 10 and 11 (herein called VA), SEQ ID NOS:20 and 21 (herein called B3-A6), SEQ ID NOS:30 and 31 (herein called B3-D1), SEQ ID NOS:40 and 41 (herein called B3-2D1), SEQ ID NOS:50 and 51 (herein called B3-2E3), SEQ ID NOS:60 and 61 (herein called B3-2G11), SEQ ID NOS:70 and 71 (herein called B3-2H1), SEQ ID NOS:80 and 81 (herein called B3-4A1), SEQ ID NOS:90 and 91 (herein called B3-4F7), or SEQ ID NOS: 100 and 101 (herein called B3-5A6). In embodiments, the VA antibody includes the mutations L234A and L235A in the Fc region (VA-LALA). In embodiments, the B3-A6 antibody includes the mutations L234A and L235A in the Fc region (B3-A6-LALA). In embodiments, the B3-D1 antibody includes the mutations L234A and L235A in the Fc region (B3-D1-LALA). In embodiments, the B3- 2D1 antibody includes the mutations L234A and L235A in the Fc region (B3-2D1-LALA). In embodiments, the B3-2E3 antibody includes the mutations L234A and L235A in the Fc region (B3-2E3-LALA). In embodiments, the B3-2G11 antibody includes the mutations L234A and L235A in the Fc region (B3-2G11-LALA). In embodiments, the B3-2H1 antibody includes the mutations L234A and L235A in the Fc region (B3-2H1-LALA). In embodiments, the B3-4A1 antibody includes the mutations L234A and L235A in the Fc region (B3-4A1-LALA). In embodiments, the B3-4F7 antibody includes the mutations L234A and L235A in the Fc region (B3-4F7-LALA). In embodiments, the B3-5A6 antibody includes the mutations L234A and L235A in the Fc region (B3-5A6-LALA).

[00153] The present disclosure provides a Fab fully human antibody fragment, comprising a heavy variable region from a heavy chain and a variable region from a light chain, wherein the sequence of the variable region from the heavy chain is at least 95% identical, or at least 96% identical, or at least 97% identical, or at least 98% identical, or at least 99% identical to the amino acid sequence of SEQ ID NO: 10, SEQ ID NO:20, SEQ ID NO:30, SEQ ID NO:40, SEQ ID NO:50, SEQ ID NO:60, SEQ ID NO:70, SEQ ID NO:80, SEQ ID NO:90, or SEQ ID NO: 100, or combinations thereof. The sequence of the variable region from the light chain is at least 95% identical, or at least 96% identical, or at least 97% identical, or at least 98% identical, or at least 99% identical to the amino acid sequence of SEQ ID NO: 11, SEQ ID NO:21, SEQ ID NO:31, SEQ ID NO:41, SEQ ID NO:51, SEQ ID NO:61, SEQ ID NO:71, SEQ ID NO:81, SEQ ID NO:91, or SEQ ID NO:101, or combinations thereof.

[00154] The present disclosure provides a Fab fully human antibody fragment, comprising a heavy chain variable region and a light chain variable region, wherein the heavy/light chain variable region amino acid sequences are at least 95% identical, or at least 96% identical, or at least 97% identical, or at least 98% identical, or at least 99% identical to any of the following amino acid sequence sets: SEQ ID NOS: 10 and 11 (herein called VA), SEQ ID NOS:20 and 21 (herein called B3-A6), SEQ ID NOS:30 and 31 (herein called B3-D1), SEQ ID NOS:40 and 41 (herein called B3-2D1), SEQ ID NOS:50 and 51 (herein called B3-2E3), SEQ ID NOS:60 and 61 (herein called B3-2G11), SEQ ID NOS:70 and 71 (herein called B3- 2H1), SEQ ID NOS:80 and 81 (herein called B3-4A1), SEQ ID NOS:90 and 91 (herein called B3-4F7), or SEQ ID NOS: 100 and 101 (herein called B3-5A6). In embodiments, the VA antibody includes the mutations L234A and L235A in the Fc region (VA-LALA). In embodiments, the B3-A6 antibody includes the mutations L234A and L235A in the Fc region (B3-A6-LALA). In embodiments, the B3-D1 antibody includes the mutations L234A and L235A in the Fc region (B3-D1-LALA). In embodiments, the B3-2D1 antibody includes the mutations L234A and L235A in the Fc region (B3-2D1-LALA). In embodiments, the B3-2E3 antibody includes the mutations L234A and L235A in the Fc region (B3-2E3-LALA). In embodiments, the B3-2G11 antibody includes the mutations L234A and L235A in the Fc region (B3-2G11-LALA). In embodiments, the B3-2H1 antibody includes the mutations L234A and L235A in the Fc region (B3-2H1-LALA). In embodiments, the B3-4A1 antibody includes the mutations L234A and L235A in the Fc region (B3-4A1-LALA). In embodiments, the B3-4F7 antibody includes the mutations L234A and L235A in the Fc region (B3-4F7-LALA). In embodiments, the B3-5A6 antibody includes the mutations L234A and L235A in the Fc region (B3-5A6-LALA).

[00155] The present disclosure provides a single chain fully human antibody comprising a polypeptide chain having a variable region from a fully human heavy chain and a variable region from a fully human light chain, and optionally a linker joining the variable heavy and variable light chain regions, wherein the variable heavy region comprises at least 95% sequence identity, or at least 96% sequence identity, or at least 97% sequence identity, or at least 98% sequence identity, or at least 99% sequence identity to the amino acid sequence of SEQ ID NO: 10, SEQ ID NO:20, SEQ ID NO:30, SEQ ID NO:40, SEQ ID NO:50, SEQ ID NO:60, SEQ ID NO:70, SEQ ID NO:80, SEQ ID NO:90, or SEQ ID NO: 100, or combinations thereof. The variable light region comprises at least 95% sequence identity, or at least 96% sequence identity, or at least 97% sequence identity, or at least 98% sequence identity, or at least 99% sequence identity to the amino acid sequence of SEQ ID NO: 11, SEQ ID NO:21, SEQ ID NO:31, SEQ ID NO:41, SEQ ID NO:51, SEQ ID NO:61, SEQ ID NO:71, SEQ ID NO:81, SEQ ID NO:91, or SEQ ID NO:101, or combinations thereof.

[00156] The present disclosure provides a single chain fully human antibody comprising a polypeptide chain having heavy chain variable region and a light chain variable region, wherein the heavy/light chain variable region amino acid sequence sets are at least 95% identical, or at least 96% identical, or at least 97% identical, or at least 98% identical, or at least 99% identical to any of the following amino acid sequence sets: SEQ ID NOS: 10 and 11 (herein called VA), SEQ ID NOS:20 and 21 (herein called B3-A6), SEQ ID NOS:30 and 31 (herein called B3-D1), SEQ ID NOS:40 and 41 (herein called B3-2D1), SEQ ID NOS:50 and 51 (herein called B3-2E3), SEQ ID NOS:60 and 61 (herein called B3-2G11), SEQ ID NOS:70 and 71 (herein called B3-2H1), SEQ ID NOS:80 and 81 (herein called B3-4A1), SEQ ID NOS:90 and 91 (herein called B3-4F7), or SEQ ID NOS: 100 and 101 (herein called B3-5A6). In embodiments, the VA antibody includes the mutations L234A and L235A in the Fc region (VA-LALA). In embodiments, the B3-A6 antibody includes the mutations L234A and L235A in the Fc region (B3-A6-LALA). In embodiments, the B3-D1 antibody includes the mutations L234A and L235A in the Fc region (B3-D1-EAEA). In embodiments, the B3- 2D1 antibody includes the mutations E234A and E235A in the Fc region (B3-2D1-EAEA). In embodiments, the B3-2E3 antibody includes the mutations E234A and E235A in the Fc region (B3-2E3-EAEA). In embodiments, the B3-2G11 antibody includes the mutations E234A and E235A in the Fc region (B3-2G11-EAEA). In embodiments, the B3-2H1 antibody includes the mutations E234A and E235A in the Fc region (B3-2H1-EAEA). In embodiments, the B3-4A1 antibody includes the mutations E234A and E235A in the Fc region (B3-4A1-EAEA). In embodiments, the B3-4F7 antibody includes the mutations E234A and E235A in the Fc region (B3-4F7-EAEA). In embodiments, the B3-5A6 antibody includes the mutations E234A and E235A in the Fc region (B3-5A6-EAEA).

[00157] The present disclosure provides pharmaceutical compositions comprising any of the anti-B7-H3 antibodies described herein, or antigen binding protein thereof, in an admixture with a pharmaceutically-acceptable excipient. An excipient encompasses carriers and stabilizers. In one embodiment, the pharmaceutical compositions comprise an anti-B7- H3 antibody, or antigen binding fragment thereof, comprising a heavy chain variable region and a light chain variable region, wherein the heavy/light chain variable region amino acid sequences are at least 95% identical, or at least 96% identical, or at least 97% identical, or at least 98% identical, or at least 99% identical to any of the following amino acid sequence sets: SEQ ID NOS: 10 and 11 (herein called VA), SEQ ID NOS:20 and 21 (herein called B3- A6), SEQ ID NOS:30 and 31 (herein called B3-D1), SEQ ID NOS:40 and 41 (herein called B3-2D1), SEQ ID NOS:50 and 51 (herein called B3-2E3), SEQ ID NOS:60 and 61 (herein called B3-2G11), SEQ ID NOS:70 and 71 (herein called B3-2H1), SEQ ID NOS:80 and 81 (herein called B3-4A1), SEQ ID NOS:90 and 91 (herein called B3-4F7), or SEQ ID NOS: 100 and 101 (herein called B3-5A6). In embodiments, the VA antibody includes the mutations L234A and L235A in the Fc region (VA-LALA). In embodiments, the B3-A6 antibody includes the mutations L234A and L235A in the Fc region (B3-A6-LALA). In embodiments, the B3-D1 antibody includes the mutations L234A and L235A in the Fc region (B3-D1- LALA). In embodiments, the B3-2D1 antibody includes the mutations L234A and L235A in the Fc region (B 3 -2D 1 -LAL A). In embodiments, the B3-2E3 antibody includes the mutations L234A and L235A in the Fc region (B3-2E3-LALA). In embodiments, the B3-2G11 antibody includes the mutations L234A and L235A in the Fc region (B3-2G11-LALA). In embodiments, the B3-2H1 antibody includes the mutations L234A and L235A in the Fc region (B3-2H1-LALA). In embodiments, the B3-4A1 antibody includes the mutations L234A and L235A in the Fc region (B3-4A1-LALA). In embodiments, the B3-4F7 antibody includes the mutations L234A and L235A in the Fc region (B3-4F7-LALA). In embodiments, the B3-5A6 antibody includes the mutations L234A and L235A in the Fc region (B3-5A6- LALA).

[00158] The present disclosure provides a kit comprising any one or any combination of two or more of the anti-B7-H3 antibodies, or antigen binding fragments thereof, described herein. In embodiments, the kit comprises any one or any combination of two or more anti- B7-H3 antibodies, or antigen binding fragments thereof, comprising a heavy chain variable region and a light chain variable region, wherein the heavy/light chain variable region amino acid sequences are at least 95% identical, or at least 96% identical, or at least 97% identical, or at least 98% identical, or at least 99% identical to the following amino acid sequence set: SEQ ID NOS: 10 and 11 (herein called VA), SEQ ID NOS:20 and 21 (herein called B3-A6), SEQ ID NOS:30 and 31 (herein called B3-D1), SEQ ID NOS:40 and 41 (herein called B3- 2D1), SEQ ID NOS:50 and 51 (herein called B3-2E3), SEQ ID NOS:60 and 61 (herein called B3-2G11), SEQ ID NOS:70 and 71 (herein called B3-2H1), SEQ ID NOS:80 and 81 (herein called B3-4A1), SEQ ID NOS:90 and 91 (herein called B3-4F7), or SEQ ID NOS: 100 and 101 (herein called B3-5A6). In embodiments, the VA antibody includes the mutations L234A and L235A in the Fc region (VA-LALA). In embodiments, the B3-A6 antibody includes the mutations L234A and L235A in the Fc region (B3-A6-LALA). In embodiments, the B3-D1 antibody includes the mutations L234A and L235A in the Fc region (B3-D1-LALA). In embodiments, the B3-2D1 antibody includes the mutations L234A and L235A in the Fc region (B3-2D1-LALA). In embodiments, the B3-2E3 antibody includes the mutations L234A and L235A in the Fc region (B3-2E3-LALA). In embodiments, the B3-2G11 antibody includes the mutations L234A and L235A in the Fc region (B3-2G11-LALA). In embodiments, the B3-2H1 antibody includes the mutations L234A and L235A in the Fc region (B3-2H1-LALA). In embodiments, the B3-4A1 antibody includes the mutations L234A and L235A in the Fc region (B3-4A1-LALA). In embodiments, the B3-4F7 antibody includes the mutations L234A and L235A in the Fc region (B3-4F7-LALA). In embodiments, the B3-5A6 antibody includes the mutations L234A and L235A in the Fc region (B3-5A6- LALA). [00159] The kit can be used to detect the presence or absence of a B7-H3 antigen for example in a biological sample. The kit can be used for conducting an in vitro reaction such as antigen binding assays in the form of ELISA, flow cytometry or surface plasmon resonance; in vitro cell activation assays; luciferase-reporter assays; Western blotting and detection; and other such in vitro assays. The kit can be used for treating a subject having a B7-H3-associated disease or condition, such as, for example, sarcoma, osteosarcoma, pancreatic adenocarcinoma, head and neck cancer, or neuroblastoma.

[00160] The present disclosure provides a first nucleic acid encoding a first polypeptide comprising the anti-B7-H3 antibody heavy chain variable region having at least 95% sequence identity, or at least 96% sequence identity, or at least 97% sequence identity, or at least 98% sequence identity, or at least 99% sequence identity with SEQ ID NO: 10, SEQ ID NO:20, SEQ ID NO:30, SEQ ID NO:40, SEQ ID NO:50, SEQ ID NO:60, SEQ ID NO:70, SEQ ID NO:80, SEQ ID NO:90, or SEQ ID NO: 100, or combinations thereof.

[00161] The present disclosure provides a first nucleic acid encoding a first polypeptide comprising the anti-B7-H3 antibody (e.g., VA) heavy chain variable region having a heavy chain complementarity determining region 1 (CDR1) having the amino acid sequence of SEQ ID NO: 12, a heavy chain CDR2 region having the amino acid sequence of SEQ ID NO: 13, and a heavy chain CDR3 region having the amino acid sequence of SEQ ID NO: 14.

[00162] The present disclosure provides a first nucleic acid encoding a first polypeptide comprising the anti-B7-H3 antibody (e.g., B3-A6) heavy chain variable region having a heavy chain complementarity determining region 1 (CDR1) having the amino acid sequence of SEQ ID NO:22, a heavy chain CDR2 region having the amino acid sequence of SEQ ID NO:23, and a heavy chain CDR3 region having the amino acid sequence of SEQ ID NO:24. [00163] The present disclosure provides a first nucleic acid encoding a first polypeptide comprising the anti-B7-H3 antibody (e.g., B3-D1) heavy chain variable region having a heavy chain complementarity determining region 1 (CDR1) having the amino acid sequence of SEQ ID NO:32, a heavy chain CDR2 region having the amino acid sequence of SEQ ID NO:33, and a heavy chain CDR3 region having the amino acid sequence of SEQ ID NO:34. [00164] The present disclosure provides a first nucleic acid encoding a first polypeptide comprising the anti-B7-H3 antibody (e.g., B3-2D1) heavy chain variable region having a heavy chain complementarity determining region 1 (CDR1) having the amino acid sequence of SEQ ID NO:42, a heavy chain CDR2 region having the amino acid sequence of SEQ ID NO:43, and a heavy chain CDR3 region having the amino acid sequence of SEQ ID NO:44. [00165] The present disclosure provides a first nucleic acid encoding a first polypeptide comprising the anti-B7-H3 antibody (e.g., B3-2E3) heavy chain variable region having a heavy chain complementarity determining region 1 (CDR1) having the amino acid sequence of SEQ ID NO:52, a heavy chain CDR2 region having the amino acid sequence of SEQ ID NO:53, and a heavy chain CDR3 region having the amino acid sequence of SEQ ID NO:54. [00166] The present disclosure provides a first nucleic acid encoding a first polypeptide comprising the anti-B7-H3 antibody (e.g., B3-2G11) heavy chain variable region having a heavy chain complementarity determining region 1 (CDR1) having the amino acid sequence of SEQ ID NO:62, a heavy chain CDR2 region having the amino acid sequence of SEQ ID NO:63, and a heavy chain CDR3 region having the amino acid sequence of SEQ ID NO:64. [00167] The present disclosure provides a first nucleic acid encoding a first polypeptide comprising the anti-B7-H3 antibody (e.g., B3-2H1) heavy chain variable region having a heavy chain complementarity determining region 1 (CDR1) having the amino acid sequence of SEQ ID NO:72, a heavy chain CDR2 region having the amino acid sequence of SEQ ID NO:73, and a heavy chain CDR3 region having the amino acid sequence of SEQ ID NO:74. [00168] The present disclosure provides a first nucleic acid encoding a first polypeptide comprising the anti-B7-H3 antibody (e.g., B3-4A1) heavy chain variable region having a heavy chain complementarity determining region 1 (CDR1) having the amino acid sequence of SEQ ID NO:82, a heavy chain CDR2 region having the amino acid sequence of SEQ ID NO:83, and a heavy chain CDR3 region having the amino acid sequence of SEQ ID NO:84. [00169] The present disclosure provides a first nucleic acid encoding a first polypeptide comprising the anti-B7-H3 antibody (e.g., B3-4F7) heavy chain variable region having a heavy chain complementarity determining region 1 (CDR1) having the amino acid sequence of SEQ ID NO:92, a heavy chain CDR2 region having the amino acid sequence of SEQ ID NO:93, and a heavy chain CDR3 region having the amino acid sequence of SEQ ID NO:94. [00170] The present disclosure provides a first nucleic acid encoding a first polypeptide comprising the anti-B7-H3 antibody (e.g., B3-5A6) heavy chain variable region having a heavy chain complementarity determining region 1 (CDR1) having the amino acid sequence of SEQ ID NO: 102, a heavy chain CDR2 region having the amino acid sequence of SEQ ID NO: 103, and a heavy chain CDR3 region having the amino acid sequence of SEQ ID NO: 104.

[00171] The present disclosure provides a first vector operably linked to a first nucleic acid encoding a first polypeptide comprising the anti-B7-H3 antibody heavy chain variable region having at least 95% sequence identity, or at least 96% sequence identity, or at least 97% sequence identity, or at least 98% sequence identity, or at least 99% sequence identity with SEQ ID NO: 10, SEQ ID NO:20, SEQ ID NO:30, SEQ ID NO:40, SEQ ID NO:50, SEQ ID NO:60, SEQ ID NO:70, SEQ ID NO:80, SEQ ID NO:90, or SEQ ID NO: 100. In one embodiment, the first vector comprises an expression vector. In one embodiment, the first vector comprises at least one promoter which is operably linked to the first nucleic acid. [00172] The present disclosure provides a first vector (e.g., a first expression vector) operably linked to a first nucleic acid encoding a first polypeptide comprising the anti-B7-H3 antibody heavy chain variable region having at least 95% sequence identity with SEQ ID NO: 10, SEQ ID NO:20, SEQ ID NO:30, SEQ ID NO:40, SEQ ID NO:50, SEQ ID NO:60, SEQ ID NO:70, SEQ ID NO:80, SEQ ID NO:90, or SEQ ID NO: 100. In one embodiment, the first vector comprises an expression vector. In one embodiment, the first vector comprises at least one promoter which is operably linked to the first nucleic acid.

[00173] The present disclosure provides a first vector operably linked to a first nucleic acid encoding a first polypeptide comprising the anti-B7-H3 antibody (e.g., VA) heavy chain variable region having a heavy chain complementarity determining region 1 (CDR1) having the amino acid sequence of SEQ ID NO: 12, a heavy chain CDR2 region having the amino acid sequence of SEQ ID NO: 13, and a heavy chain CDR3 region having the amino acid sequence of SEQ ID NO: 14. In one embodiment, the first vector comprises a first expression vector. In one embodiment, the first vector comprises at least one promoter which is operably linked to the first nucleic acid.

[00174] The present disclosure provides a first vector operably linked to a first nucleic acid encoding a first polypeptide comprising the anti-B7-H3 antibody (e.g., B3-A6) heavy chain variable region having a heavy chain complementarity determining region 1 (CDR1) having the amino acid sequence of SEQ ID NO:22, a heavy chain CDR2 region having the amino acid sequence of SEQ ID NO:23, and a heavy chain CDR3 region having the amino acid sequence of SEQ ID NO:24. In one embodiment, the first vector comprises a first expression vector. In one embodiment, the first vector comprises at least one promoter which is operably linked to the first nucleic acid.

[00175] The present disclosure provides a first vector operably linked to a first nucleic acid encoding a first polypeptide comprising the anti-B7-H3 antibody (e.g., B3-D1) heavy chain variable region having a heavy chain complementarity determining region 1 (CDR1) having the amino acid sequence of SEQ ID NO:32, a heavy chain CDR2 region having the amino acid sequence of SEQ ID NO:33, and a heavy chain CDR3 region having the amino acid sequence of SEQ ID NO:34. In one embodiment, the first vector comprises a first expression vector. In one embodiment, the first vector comprises at least one promoter which is operably linked to the first nucleic acid.

[00176] The present disclosure provides a first vector operably linked to a first nucleic acid encoding a first polypeptide comprising the anti-B7-H3 antibody (e.g., B3-2D1) heavy chain variable region having a heavy chain complementarity determining region 1 (CDR1) having the amino acid sequence of SEQ ID NO:42, a heavy chain CDR2 region having the amino acid sequence of SEQ ID NO:43, and a heavy chain CDR3 region having the amino acid sequence of SEQ ID NO:44. In one embodiment, the first vector comprises a first expression vector. In one embodiment, the first vector comprises at least one promoter which is operably linked to the first nucleic acid.

[00177] The present disclosure provides a first vector operably linked to a first nucleic acid encoding a first polypeptide comprising the anti-B7-H3 antibody (e.g., B3-2E3) heavy chain variable region having a heavy chain complementarity determining region 1 (CDR1) having the amino acid sequence of SEQ ID NO:52, a heavy chain CDR2 region having the amino acid sequence of SEQ ID NO: 53, and a heavy chain CDR3 region having the amino acid sequence of SEQ ID NO:54. In one embodiment, the first vector comprises a first expression vector. In one embodiment, the first vector comprises at least one promoter which is operably linked to the first nucleic acid.

[00178] The present disclosure provides a first vector operably linked to a first nucleic acid encoding a first polypeptide comprising the anti-B7-H3 antibody (e.g., B3-2G11) heavy chain variable region having a heavy chain complementarity determining region 1 (CDR1) having the amino acid sequence of SEQ ID NO:62, a heavy chain CDR2 region having the amino acid sequence of SEQ ID NO: 63, and a heavy chain CDR3 region having the amino acid sequence of SEQ ID NO:64. In one embodiment, the first vector comprises a first expression vector. In one embodiment, the first vector comprises at least one promoter which is operably linked to the first nucleic acid.

[00179] The present disclosure provides a first vector operably linked to a first nucleic acid encoding a first polypeptide comprising the anti-B7-H3 antibody (e.g., B3-2H1) heavy chain variable region having a heavy chain complementarity determining region 1 (CDR1) having the amino acid sequence of SEQ ID NO:72, a heavy chain CDR2 region having the amino acid sequence of SEQ ID NO:73, and a heavy chain CDR3 region having the amino acid sequence of SEQ ID NO:74. In one embodiment, the first vector comprises a first expression vector. In one embodiment, the first vector comprises at least one promoter which is operably linked to the first nucleic acid. [00180] The present disclosure provides a first vector operably linked to a first nucleic acid encoding a first polypeptide comprising the anti-B7-H3 antibody (e.g., B3-4A1) heavy chain variable region having a heavy chain complementarity determining region 1 (CDR1) having the amino acid sequence of SEQ ID NO:82, a heavy chain CDR2 region having the amino acid sequence of SEQ ID NO:83, and a heavy chain CDR3 region having the amino acid sequence of SEQ ID NO:84. In one embodiment, the first vector comprises a first expression vector. In one embodiment, the first vector comprises at least one promoter which is operably linked to the first nucleic acid.

[00181] The present disclosure provides a first vector operably linked to a first nucleic acid encoding a first polypeptide comprising the anti-B7-H3 antibody (e.g., B3-4F7) heavy chain variable region having a heavy chain complementarity determining region 1 (CDR1) having the amino acid sequence of SEQ ID NO:92, a heavy chain CDR2 region having the amino acid sequence of SEQ ID NO: 93, and a heavy chain CDR3 region having the amino acid sequence of SEQ ID NO:94. In one embodiment, the first vector comprises a first expression vector. In one embodiment, the first vector comprises at least one promoter which is operably linked to the first nucleic acid.

[00182] The present disclosure provides a first vector operably linked to a first nucleic acid encoding a first polypeptide comprising the anti-B7-H3 antibody (e.g., B3-5A6) heavy chain variable region having a heavy chain complementarity determining region 1 (CDR1) having the amino acid sequence of SEQ ID NO: 102, a heavy chain CDR2 region having the amino acid sequence of SEQ ID NO: 103, and a heavy chain CDR3 region having the amino acid sequence of SEQ ID NO: 104. In one embodiment, the first vector comprises a first expression vector. In one embodiment, the first vector comprises at least one promoter which is operably linked to the first nucleic acid.

[00183] The present disclosure provides a first host cell harboring the first vector operably linked to the first nucleic acid which encodes the first polypeptide comprising the anti-B7-H3 antibody heavy chain variable region having at least 95% sequence identity, or at least 96% sequence identity, or at least 97% sequence identity, or at least 98% sequence identity, or at least 99% sequence identity with SEQ ID NO: 10, SEQ ID NO:20, SEQ ID NO:30, SEQ ID NO:40, SEQ ID NO:50, SEQ ID NO:60, SEQ ID NO:70, SEQ ID NO:80, SEQ ID NO:90, or SEQ ID NO: 100.

[00184] In one embodiment, the first vector comprises a first expression vector. In one embodiment, the first host cell expresses the first polypeptide comprising the antibody heavy chain variable region having at least 95% sequence identity to the amino acid sequence of SEQ ID NO: 10, SEQ ID NO:20, SEQ ID NO:30, SEQ ID NO:40, SEQ ID NO:50, SEQ ID NO:60, SEQ ID NO:70, SEQ ID NO:80, SEQ ID NO:90, or SEQ ID NO: 100.

[00185] The present disclosure provides a method for preparing a first polypeptide comprising an antibody heavy chain variable region, the method comprising: culturing a population of the first host cells (e.g., a plurality of the first host cell) harboring the first expression vector under conditions suitable for expressing the first polypeptide comprising the antibody heavy chain variable region having at least 95% sequence identity to the amino acid sequence of SEQ ID NO: 10, SEQ ID NO:20, SEQ ID NO:30, SEQ ID NO:40, SEQ ID NO:50, SEQ ID NO:60, SEQ ID NO:70, SEQ ID NO:80, SEQ ID NO:90, or SEQ ID NO: 100.

[00186] In one embodiment, the method further comprises: recovering from the population of the first host cells the expressed first polypeptide comprising the antibody heavy chain variable region having at least 95% sequence identity to the amino acid sequence of SEQ ID NO: 10, SEQ ID NO:20, SEQ ID NO:30, SEQ ID NO:40, SEQ ID NO:50, SEQ ID NO:60, SEQ ID NO:70, SEQ ID NO:80, SEQ ID NO:90, or SEQ ID NO: 100.

[00187] The present disclosure provides a second nucleic acid encoding a second polypeptide comprising the anti-B7-H3 antibody light chain variable region having at least 95% sequence identity, or at least 96% sequence identity, or at least 97% sequence identity, or at least 98% sequence identity, or at least 99% sequence identity with SEQ ID NO: 11, SEQ ID NO:21, SEQ ID NO:31, SEQ ID NO:41, SEQ ID NO:51, SEQ ID NO:61, SEQ ID NO:71, SEQ ID NO:81, SEQ ID NO:91, or SEQ ID NO:101, or combinations thereof. [00188] The present disclosure provides a second nucleic acid encoding a second polypeptide comprising the anti-B7-H3 antibody (e.g., VA) light chain variable region having a light chain complementarity determining region 1 (CDR1) having the amino acid sequence of SEQ ID NO: 15, a light chain CDR2 region having the amino acid sequence of SEQ ID NO: 16, and a light chain CDR3 region having the amino acid sequence of SEQ ID NO: 17.

[00189] The present disclosure provides a second nucleic acid encoding a second polypeptide comprising the anti-B7-H3 antibody (e.g., B3-A6) light chain variable region having a light chain complementarity determining region 1 (CDR1) having the amino acid sequence of SEQ ID NO:25, a light chain CDR2 region having the amino acid sequence of SEQ ID NO:26, and a light chain CDR3 region having the amino acid sequence of SEQ ID NO:27.

[00190] The present disclosure provides a second nucleic acid encoding a second polypeptide comprising the anti-B7-H3 antibody (e.g., B3-D1) light chain variable region having a light chain complementarity determining region 1 (CDR1) having the amino acid sequence of SEQ ID NO:35, a light chain CDR2 region having the amino acid sequence of SEQ ID NO:36, and a light chain CDR3 region having the amino acid sequence of SEQ ID NO:37.

[00191] The present disclosure provides a second nucleic acid encoding a second polypeptide comprising the anti-B7-H3 antibody (e.g., B3-2D1) light chain variable region having a light chain complementarity determining region 1 (CDR1) having the amino acid sequence of SEQ ID NO:45, a light chain CDR2 region having the amino acid sequence of SEQ ID NO:46, and a light chain CDR3 region having the amino acid sequence of SEQ ID NO:47.

[00192] The present disclosure provides a second nucleic acid encoding a second polypeptide comprising the anti-B7-H3 antibody (e.g., B3-2E3) light chain variable region having a light chain complementarity determining region 1 (CDR1) having the amino acid sequence of SEQ ID NO:55, a light chain CDR2 region having the amino acid sequence of SEQ ID NO:56, and a light chain CDR3 region having the amino acid sequence of SEQ ID NO:57.

[00193] The present disclosure provides a second nucleic acid encoding a second polypeptide comprising the anti-B7-H3 antibody (e.g., B3-2G11) light chain variable region having a light chain complementarity determining region 1 (CDR1) having the amino acid sequence of SEQ ID NO:65, a light chain CDR2 region having the amino acid sequence of SEQ ID NO:66, and a light chain CDR3 region having the amino acid sequence of SEQ ID NO:67.

[00194] The present disclosure provides a second nucleic acid encoding a second polypeptide comprising the anti-B7-H3 antibody (e.g., B3-2H1) light chain variable region having a light chain complementarity determining region 1 (CDR1) having the amino acid sequence of SEQ ID NO:75, a light chain CDR2 region having the amino acid sequence of SEQ ID NO:76, and a light chain CDR3 region having the amino acid sequence of SEQ ID NO:77.

[00195] The present disclosure provides a second nucleic acid encoding a second polypeptide comprising the anti-B7-H3 antibody (e.g., B3-4A1) light chain variable region having a light chain complementarity determining region 1 (CDR1) having the amino acid sequence of SEQ ID NO:85, a light chain CDR2 region having the amino acid sequence of SEQ ID NO:86, and a light chain CDR3 region having the amino acid sequence of SEQ ID NO:87. [00196] The present disclosure provides a second nucleic acid encoding a second polypeptide comprising the anti-B7-H3 antibody (e.g., B3-4F7) light chain variable region having a light chain complementarity determining region 1 (CDR1) having the amino acid sequence of SEQ ID NO:95, a light chain CDR2 region having the amino acid sequence of SEQ ID NO:96, and a light chain CDR3 region having the amino acid sequence of SEQ ID NO:97.

[00197] The present disclosure provides a second nucleic acid encoding a second polypeptide comprising the anti-B7-H3 antibody (e.g., B3-5A6) light chain variable region having a light chain complementarity determining region 1 (CDR1) having the amino acid sequence of SEQ ID NO: 105, a light chain CDR2 region having the amino acid sequence of SEQ ID NO: 106, and a light chain CDR3 region having the amino acid sequence of SEQ ID NO: 107.

[00198] The present disclosure provides a second vector operably linked to a second nucleic acid encoding a second polypeptide comprising the anti-B7-H3 antibody light chain variable region having at least 95% sequence identity, or at least 96% sequence identity, or at least 97% sequence identity, or at least 98% sequence identity, or at least 99% sequence identity with SEQ ID NO: 11, SEQ ID NO:21, SEQ ID NO:31, SEQ ID NO:41, SEQ ID NO:51, SEQ ID NO:61, SEQ ID NO:71, SEQ ID NO:81, SEQ ID NO:91, or SEQ ID NO: 101. In one embodiment, the second vector comprises a second expression vector. In one embodiment, the second vector comprises at least one promoter which is operably linked to the second nucleic acid.

[00199] The present disclosure provides a second vector (e.g., a second expression vector) operably linked to a second nucleic acid encoding a second polypeptide comprising the anti- B7-H3 antibody light chain variable region having at least 95% sequence identity with SEQ ID NO: 11, SEQ ID NO:21, SEQ ID NO:31, SEQ ID NO:41, SEQ ID NO:51, SEQ ID NO:61, SEQ ID NO:71, SEQ ID NO:81, SEQ ID NO:91, or SEQ ID NO:101. In one embodiment, the second vector comprises an expression vector. In one embodiment, the second vector comprises at least one promoter which is operably linked to the second nucleic acid.

[00200] The present disclosure provides a second vector operably linked to a second nucleic acid encoding a second polypeptide comprising the anti-B7-H3 antibody (e.g., VA) light chain variable region having a light chain complementarity determining region 1 (CDR1) having the amino acid sequence of SEQ ID NO: 15, a light chain CDR2 region having the amino acid sequence of SEQ ID NO: 16, and a light chain CDR3 region having the amino acid sequence of SEQ ID NO: 17. In one embodiment, the second vector comprises a second expression vector. In one embodiment, the second vector comprises at least one promoter which is operably linked to the second nucleic acid.

[00201] The present disclosure provides a second vector operably linked to a second nucleic acid encoding a second polypeptide comprising the anti-B7-H3 antibody (e.g., B3- A6) light chain variable region having a light chain complementarity determining region 1 (CDR1) having the amino acid sequence of SEQ ID NO:25, a light chain CDR2 region having the amino acid sequence of SEQ ID NO:26, and a light chain CDR3 region having the amino acid sequence of SEQ ID NO:27. In one embodiment, the second vector comprises a second expression vector. In one embodiment, the second vector comprises at least one promoter which is operably linked to the second nucleic acid.

[00202] The present disclosure provides a second vector operably linked to a second nucleic acid encoding a second polypeptide comprising the anti-B7-H3 antibody (e.g., B3- Dl) light chain variable region having a light chain complementarity determining region 1 (CDR1) having the amino acid sequence of SEQ ID NO:35, a light chain CDR2 region having the amino acid sequence of SEQ ID NO:36, and a light chain CDR3 region having the amino acid sequence of SEQ ID NO:37. In one embodiment, the second vector comprises a second expression vector. In one embodiment, the second vector comprises at least one promoter which is operably linked to the second nucleic acid.

[00203] The present disclosure provides a second vector operably linked to a second nucleic acid encoding a second polypeptide comprising the anti-B7-H3 antibody (e.g., B3- 2D1) light chain variable region having a light chain complementarity determining region 1 (CDR1) having the amino acid sequence of SEQ ID NO:45, a light chain CDR2 region having the amino acid sequence of SEQ ID NO:46, and a light chain CDR3 region having the amino acid sequence of SEQ ID NO:47. In one embodiment, the second vector comprises a second expression vector. In one embodiment, the second vector comprises at least one promoter which is operably linked to the second nucleic acid.

[00204] The present disclosure provides a second vector operably linked to a second nucleic acid encoding a second polypeptide comprising the anti-B7-H3 antibody (e.g., B3- 2E3) light chain variable region having a light chain complementarity determining region 1 (CDR1) having the amino acid sequence of SEQ ID NO:55, a light chain CDR2 region having the amino acid sequence of SEQ ID NO:56, and a light chain CDR3 region having the amino acid sequence of SEQ ID NO:57. In one embodiment, the second vector comprises a second expression vector. In one embodiment, the second vector comprises at least one promoter which is operably linked to the second nucleic acid.

[00205] The present disclosure provides a second vector operably linked to a second nucleic acid encoding a second polypeptide comprising the anti-B7-H3 antibody (e.g., B3- 2G11) light chain variable region having a light chain complementarity determining region 1 (CDR1) having the amino acid sequence of SEQ ID NO:65, a light chain CDR2 region having the amino acid sequence of SEQ ID NO:66, and a light chain CDR3 region having the amino acid sequence of SEQ ID NO: 67. In one embodiment, the second vector comprises a second expression vector. In one embodiment, the second vector comprises at least one promoter which is operably linked to the second nucleic acid.

[00206] The present disclosure provides a second vector operably linked to a second nucleic acid encoding a second polypeptide comprising the anti-B7-H3 antibody (e.g., B3- 2H1) light chain variable region having a light chain complementarity determining region 1 (CDR1) having the amino acid sequence of SEQ ID NO:75, a light chain CDR2 region having the amino acid sequence of SEQ ID NO:76, and a light chain CDR3 region having the amino acid sequence of SEQ ID NO:77. In one embodiment, the second vector comprises a second expression vector. In one embodiment, the second vector comprises at least one promoter which is operably linked to the second nucleic acid.

[00207] The present disclosure provides a second vector operably linked to a second nucleic acid encoding a second polypeptide comprising the anti-B7-H3 antibody (e.g., B3- 4A1) light chain variable region having a light chain complementarity determining region 1 (CDR1) having the amino acid sequence of SEQ ID NO:85, a light chain CDR2 region having the amino acid sequence of SEQ ID NO:86, and a light chain CDR3 region having the amino acid sequence of SEQ ID NO: 87. In one embodiment, the second vector comprises a second expression vector. In one embodiment, the second vector comprises at least one promoter which is operably linked to the second nucleic acid.

[00208] The present disclosure provides a second vector operably linked to a second nucleic acid encoding a second polypeptide comprising the anti-B7-H3 antibody (e.g., B3- 4F7) light chain variable region having a light chain complementarity determining region 1 (CDR1) having the amino acid sequence of SEQ ID NO:95, a light chain CDR2 region having the amino acid sequence of SEQ ID NO:96, and a light chain CDR3 region having the amino acid sequence of SEQ ID NO: 97. In one embodiment, the second vector comprises a second expression vector. In one embodiment, the second vector comprises at least one promoter which is operably linked to the second nucleic acid. [00209] The present disclosure provides a second vector operably linked to a second nucleic acid encoding a second polypeptide comprising the anti-B7-H3 antibody (e.g., B3- 5A6) light chain variable region having a light chain complementarity determining region 1 (CDR1) having the amino acid sequence of SEQ ID NO: 105, a light chain CDR2 region having the amino acid sequence of SEQ ID NO: 106, and a light chain CDR3 region having the amino acid sequence of SEQ ID NO: 107. In one embodiment, the second vector comprises a second expression vector. In one embodiment, the second vector comprises at least one promoter which is operably linked to the second nucleic acid.

[00210] The present disclosure provides a second host cell harboring the second vector operably linked to the second nucleic acid which encodes the second polypeptide comprising the anti-B7-H3 antibody light chain variable region having at least 95% sequence identity, or at least 96% sequence identity, or at least 97% sequence identity, or at least 98% sequence identity, or at least 99% sequence identity with SEQ ID NO: 11, SEQ ID NO:21, SEQ ID NO:31, SEQ ID NO:41, SEQ ID NO:51, SEQ ID NO:61, SEQ ID NO:71, SEQ ID NO:81, SEQ ID NO:91, or SEQ ID NO:101. In one embodiment, the second vector comprises a second expression vector. In one embodiment, the second host cell expresses the second polypeptide comprising the antibody light chain variable region having at least 95% sequence identity to the amino acid sequence of SEQ ID NO: 11, SEQ ID NO:21, SEQ ID NO:31, SEQ ID NO:41, SEQ ID NO:51, SEQ ID NO:61, SEQ ID NO:71, SEQ ID NO:81, SEQ ID NO:91, or SEQ ID NO:101.

[00211] The present disclosure provides a method for preparing a second polypeptide comprising an antibody light chain variable region, the method comprising: culturing a population of the second host cells (e.g., a plurality of the second host cell) harboring the second expression vector under conditions suitable for expressing the second polypeptide comprising the antibody light chain variable region having at least 95% sequence identity to the amino acid sequence of SEQ ID NO: 11, SEQ ID NO:21, SEQ ID NO:31, SEQ ID NO:41, SEQ ID NO:51, SEQ ID NO:61, SEQ ID NO:71, SEQ ID NO:81, SEQ ID NO:91, or SEQ ID NO: 101. In one embodiment, the method further comprises: recovering from the population of the second host cells the expressed second polypeptide comprising the antibody light chain variable region having at least 95% sequence identity to the amino acid sequence of SEQ ID NO: 11, SEQ ID NO:21, SEQ ID NO:31, SEQ ID NO:41, SEQ ID NO:51, SEQ ID NO:61, SEQ ID NO:71, SEQ ID NO:81, SEQ ID NO:91, or SEQ ID NO:101.

[00212] The present disclosure provides a first and second nucleic acid, wherein (a) the first nucleic acid encodes a first polypeptide comprising the anti-B7-H3 antibody heavy chain variable region having at least 95% sequence identity, or at least 96% sequence identity, or at least 97% sequence identity, or at least 98% sequence identity, or at least 99% sequence identity with SEQ ID NO: 10, SEQ ID NO:20, SEQ ID NO:30, SEQ ID NO:40, SEQ ID NO:50, SEQ ID NO:60, SEQ ID NO:70, SEQ ID NO:80, SEQ ID NO:90, or SEQ ID NO: 100, and (b) the second polypeptide comprising the anti-B7-H3 antibody light chain variable region having at least 95% sequence identity, or at least 96% sequence identity, or at least 97% sequence identity, or at least 98% sequence identity, or at least 99% sequence identity with SEQ ID NO: 11, SEQ ID NO:21, SEQ ID NO:31, SEQ ID NO:41, SEQ ID NO:51, SEQ ID NO:61, SEQ ID NO:71, SEQ ID NO:81, SEQ ID NO:91, or SEQ ID NO:101.

[00213] The present disclosure provides a vector operably linked to a first and a second nucleic acid, wherein (a) the first nucleic acid encodes a first polypeptide comprising the anti- B7-H3 antibody heavy chain variable region having at least 95% sequence identity, or at least 96% sequence identity, or at least 97% sequence identity, or at least 98% sequence identity, or at least 99% sequence identity with SEQ ID NO: 10, SEQ ID NO:20, SEQ ID NO:30, SEQ ID NO:40, SEQ ID NO:50, SEQ ID NO:60, SEQ ID NO:70, SEQ ID NO:80, SEQ ID NO:90, or SEQ ID NO: 100, and (b) the second polypeptide comprising the anti-B7H3 antibody light chain variable region having at least 95% sequence identity, or at least 96% sequence identity, or at least 97% sequence identity, or at least 98% sequence identity, or at least 99% sequence identity with SEQ ID NO: 11, SEQ ID NO:21, SEQ ID NO:31, SEQ ID NO:41, SEQ ID NO:51, SEQ ID NO:61, SEQ ID NO:71, SEQ ID NO:81, SEQ ID NO:91, or SEQ ID NO: 101. In one embodiment, the vector comprises an expression vector. In one embodiment, the vector comprises at least a first promoter which is operably linked to the first nucleic acid. In one embodiment, the vector comprises at least a second promoter which is operably linked to the second nucleic acid.

[00214] The present disclosure provides a host cell harboring a vector operably linked to a first and second nucleic acid, wherein (a) the first nucleic acid encodes a first polypeptide comprising the anti-B7-H3 antibody heavy chain variable region having at least 95% sequence identity, or at least 96% sequence identity, or at least 97% sequence identity, or at least 98% sequence identity, or at least 99% sequence identity with SEQ ID NO: 10, SEQ ID NO:20, SEQ ID NO:30, SEQ ID NO:40, SEQ ID NO:50, SEQ ID NO:60, SEQ ID NO:70, SEQ ID NO:80, SEQ ID NO:90, or SEQ ID NO: 100, and (b) the second nucleic acid encodes a second polypeptide comprising the anti-B7-H3 antibody light chain variable region having at least 95% sequence identity, or at least 96% sequence identity, or at least 97% sequence identity, or at least 98% sequence identity, or at least 99% sequence identity with SEQ ID NO: 11, SEQ ID NO:21, SEQ ID NO:31, SEQ ID NO:41, SEQ ID NO:51, SEQ ID NO:61, SEQ ID NO:71, SEQ ID NO:81, SEQ ID NO:91, or SEQ ID NO:101. In one embodiment, the vector comprises an expression vector. In one embodiment, the host cell expresses (a) the first polypeptide comprising the antibody heavy chain variable region having at least 95% sequence identity to the amino acid sequence of SEQ ID NO: 10, SEQ ID NO:20, SEQ ID NO:30, SEQ ID NO:40, SEQ ID NO:50, SEQ ID NO:60, SEQ ID NO:70, SEQ ID NO:80, SEQ ID NO:90, or SEQ ID NO: 100, and (b) the second polypeptide comprising the antibody light chain variable region having at least 95% sequence identity to the amino acid sequence of SEQ ID NO: 11, SEQ ID NO:21, SEQ ID NO:31, SEQ ID NO:41, SEQ ID NO:51, SEQ ID NO:61, SEQ ID NO:71, SEQ ID NO:81, SEQ ID NO:91, or SEQ ID NO:101.

[00215] The present disclosure provides a method for preparing a first polypeptide having an antibody heavy chain variable region and a second polypeptide having an antibody light chain variable region, the method comprising: culturing a population of the host cells (e.g., a plurality of the host cell) harboring an expression vector which is operably linked to a first and a second nucleic acid encoding the first and second polypeptides, respectively. In one embodiment, the culturing is conducted under conditions suitable for expressing (a) the first polypeptide having the antibody heavy chain variable region having at least 95% sequence identity to the amino acid sequence of SEQ ID NO: 10, SEQ ID NO:20, SEQ ID NO:30, SEQ ID NO:40, SEQ ID NO:50, SEQ ID NO:60, SEQ ID NO:70, SEQ ID NO:80, SEQ ID NO:90, or SEQ ID NO: 100, and (b) the second polypeptide having the antibody light chain variable region having at least 95% sequence identity to the amino acid sequence of SEQ ID NO: 11, SEQ ID NO:21, SEQ ID NO:31, SEQ ID NO:41, SEQ ID NO:51, SEQ ID NO:61, SEQ ID NO:71, SEQ ID NO:81, SEQ ID NO:91, or SEQ ID NO:101. In one embodiment, the method further comprises: recovering from the population of the host cells the expressed first polypeptide having the antibody heavy chain variable region having at least 95% sequence identity to the amino acid sequence of SEQ ID NO: 10, SEQ ID NO:20, SEQ ID NO:30, SEQ ID NO:40, SEQ ID NO:50, SEQ ID NO:60, SEQ ID NO:70, SEQ ID NO:80, SEQ ID NO:90, or SEQ ID NO: 100 and the expressed second polypeptide having at least 95% sequence identity to the amino acid sequence of SEQ ID NO: 11, SEQ ID NO:21, SEQ ID NO:31, SEQ ID NO:41, SEQ ID NO:51, SEQ ID NO:61, SEQ ID NO:71, SEQ ID NO:81, SEQ ID NO:91, or SEQ ID NO:101.

[00216] In embodiments, the host cell, or population of host cells, harbor one or more expression vectors that can direct transient introduction of the transgene into the host cells or stable insertion of the transgene into the host cells’ genome, where the transgene comprises nucleic acids encoding any of the first and/or second polypeptides described herein. The expression vector(s) can direct transcription and/or translation of the transgene in the host cell. The expression vectors can include one or more regulatory sequences, such as inducible and/or constitutive promoters and enhancers. The expression vectors can include ribosomal binding sites and/or polyadenylation sites. In one embodiment, the expression vector, which is operably linked to the nucleic acid encoding the first and/or second polypeptide, can direct production of the first and/or second polypeptide which can be displayed on the surface of the transgenic host cell, or the first and/or second polypeptide can be secreted into the cell culture medium.

[00217] The present disclosure provides methods for inhibiting growth or proliferation of target cells, or methods for killing target cells, the method comprising: contacting a population of effector cells with a population of target cells (e.g., target cells expressing B7- H3) in the presence of an anti-B7-H3 antibody (or antibody fragment thereof) under conditions that are suitable for inhibiting growth or proliferation of target cells or killing the target cells. In embodiments, the population of effector cells comprises peripheral blood mononuclear cells (PBMCs) or natural killer (NK) cells. The PBMCs can include lymphocytes, including T cells, B cells and/or NK cells. In embodiments, the population of target cells comprise cells that naturally express B7-H3, including T cells, NK cells, antigen- presenting cells (APCs), including dendritic cells and macrophages. B7-H3 is found on fibroblasts, fibroblast-like synoviocytes, and epithelial cells and may potentially play a diverse role in the regulation of growth and differentiation of non-hematopoietic tissues. In embodiments, the population of target cells comprise cells that naturally express B7-H3, including, for example, prostate cancer cells, non- small-cell lung cancer cells, gastric carcinoma cells, and ovarian cancer cells from a subject having a disease associated with B7- H3-expression. In embodiments, the population of target cells are any type of transgenic cells that are engineered to express B7-H3. In embodiments, the ratio of effector to target cells can be about 1:1, or about 2:1, or about 3:1, or about 4:1, or about 5:1, or about 5-10:1, or about 10-20:1, or about 20-30:1.

[00218] The present disclosure provides in vitro methods for blocking interaction (e.g., binding) between B7-H3 and its receptor.

[00219] In embodiments, the methods for blocking interaction between B7-H3 polypeptide and its receptor comprise: contacting any of the anti-B7-H3 antibodies (or antibody fragment thereof) described herein (e.g., VA, B3-A6, B3-D1, B3-2D1, B3-2E3, B3-2G11, B3-2H1, B3-4A1, B3-4F7, or B3-5A6) with a B7-H3 polypeptide and a B7-H3 receptor, under conditions suitable for binding between the anti-B7-H3 antibody (or antibody fragment thereof) and the B7-H3 receptor and for blocking between the B7-H3 polypeptide and the B7- H3 receptor. In embodiments, the anti-B7-H3 antibody (or antibody fragment thereof) can be contacted with the B7-H3 polypeptide and the B7-H3 receptor at the same time (essentially simultaneously) or sequentially in any order. In embodiments, the blocking method can be conducted in vitro or in vivo.

[00220] In embodiments, the methods for blocking interaction between a B7-H3- expressing cell and a cell expressing the receptor of B7-H3 comprise: contacting any of the anti-B7-H3 antibodies (or antibody fragment thereof) described herein (e.g., VA, B3-A6, B3- Dl, B3-2D1, B3-2E3, B3-2G11, B3-2H1, B3-4A1, B3-4F7, or B3-5A6) with a B7-H3- expressing cell and a cell expressing the receptor of B7-H3, under conditions suitable for binding between the anti-B7-H3 antibody (or antibody fragment thereof) and cells expressing the B7-H3 receptor and for blocking between the B7-H3-expressing cell and the cell expressing the B7-H3 receptor. In embodiments, the anti-B7-H3 antibody (or antibody fragment thereof) can be contacted with the B7-H3-expressing cell and the cell expressing the B7-H3 receptor at the same time (essentially simultaneously) or sequentially in any order. In embodiments, the blocking method can be conducted in vitro or in vivo. In embodiments, the B7-H3-expressing cell comprises a T cell. In embodiments, the B7-H3-expressing cell comprises an NK cell. In embodiments, the B7-H3 -expressing cell comprises a tumor cell. In embodiments, the cell expressing the B7-H3 receptor comprises an NK cell. In embodiments, the cell expressing the B7-H3 receptor comprises a T cell. In embodiments, the VA antibody includes the mutations L234A and L235A in the Fc region (VA-EAEA). In embodiments, the B3-A6 antibody includes the mutations L234A and L235A in the Fc region (B3-A6-LALA). In embodiments, the B3-D1 antibody includes the mutations L234A and L235A in the Fc region (B3-D1-LALA). In embodiments, the B3-2D1 antibody includes the mutations L234A and L235A in the Fc region (B3-2D1-LALA). In embodiments, the B3-2E3 antibody includes the mutations L234A and L235A in the Fc region (B3-2E3-LALA). In embodiments, the B3-2G11 antibody includes the mutations L234A and L235A in the Fc region (B3-2G11-LALA). In embodiments, the B3-2H1 antibody includes the mutations L234A and L235A in the Fc region (B3-2H1-LALA). In embodiments, the B3-4A1 antibody includes the mutations L234A and L235A in the Fc region (B3-4A1-LALA). In embodiments, the B3-4F7 antibody includes the mutations L234A and L235A in the Fc region (B3-4F7-LALA). In embodiments, the B3-5A6 antibody includes the mutations L234A and L235A in the Fc region (B3-5A6-LALA).

[00221] The present disclosure provides methods for treating a subject having a disease associated with B7-H3 expression, the method comprising: administering to the subject an effective amount of a pharmaceutical composition comprising an anti-B7-H3 antibody or antigen binding fragment thereof, which is selected from a group consisting of any of the fully human anti-B7-H3 antibodies described herein, any of the Fab fully human anti-B7-H3 antibodies described herein, and any of the single chain human anti-B7-H3 antibodies described herein. The present disclosure provides methods for treating a subject having a disease associated with expression or over-expression of B7-H3. In embodiments, the disease associated with B7-H3 expression is an autoimmune disease. In embodiments, the disease associated with B7-H3 expression is HIV. In embodiments, the disease associated with B7-H3 expression is an inflammatory disease. In embodiments, the disease associated with B7-H3 expression is an infectious disease. In embodiments, the disease associated with B7-H3 expression comprises: carcinoma of the ovary, colon, prostate, skin, pancreas, kidney, urothelial, or lung cancer. In embodiments, the disease associated with B7-H3 expression comprises: cancer of the breast, prostate, colon, liver, ovary, bladder, pancreas, lung (e.g., non-small cell lung or small cell lung), esophagus, stomach, skin, or kidney. In embodiments, the disease associated with B7-H3 expression is selected from a group consisting of acute myeloid lymphoma (AML), non-Hodgkin lymphoma (NHL), non-small cell lung cancer (NSCLC), small cell lung cancer, urothelial cell carcinoma, esophageal cancer, hepatocellular carcinoma, glioma, neuroblastoma, glioblastoma multiforme, blastoma, sarcoma, leukemia, lymphoid malignancies, pancreatic cancer, head and neck cancer, ovarian cancer, oral cancer, breast cancer, triple negative breast cancer (TNBC), lymphoma, renal cell carcinoma, clear cell renal cell carcinoma, colon cancer, colorectal cancer, melanoma, stomach cancer, lung cancer, liver cancer, bladder cancer, prostate cancer, anal cancer, endometrial cancer, vulvar cancer, squamous cell tumors, hypopharyngeal squamous cell carcinoma, and squamous cell carcinoma (e.g., squamous cell lung cancer or squamous cell head and neck cancer).

[00222] In embodiments, the cancer is a metastatic cancer, refractory cancer, or recurrent cancer.

[00223] An anti-B7-H3 antibody can be used alone to inhibit the growth of cancerous tumors. In embodiments, an anti-B7-H3 antibody can be used in conjunction with another agent, e.g., other immunogenic agents, standard cancer treatments, or other antibodies, for treatment of a disease associated with B7-H3 expression (or elevated B7-H3 expression). [00224] In embodiments, the disease associated with B7-H3 expression is cancer. In embodiments, the method for treating a subject having a B7-H3-expressing cancer, the method comprising: administering to the subject an effective amount of a pharmaceutical composition comprising an anti-B7-H3 antibody or antigen binding fragment thereof, which is selected from a group consisting of any of the fully human anti-B7-H3 antibodies described herein, any of the Fab fully human anti-B7-H3 antibodies described herein, and any of the single chain human anti-B7-H3 antibodies described herein. The method further comprising co-administration of a cytotoxic, cystostatic, or antiangiogenic agent suitable for treating the cancer.

[00225] In embodiments, treatment of a subject with a disease associated with B7-H3 expression (e.g., cancer) with a B7-H3 antibody as provided herein (e.g., VA clone), or an antibody having a heavy chain variable region having at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% identity to SEQ ID NO: 10 and a light chain variable region having at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% identity to SEQ ID NO: 11 can result in less toxicity to the subject, including, without limitation, less anemia, hemagglutination of peripheral blood cells, or reduction of immune cells, than treatment of a patient with the same tumor targeting antibody and a different anti-B7-H3 antibody.

[00226] In embodiments, B7-H3 (VA clone) exhibits reduced hemagglutination when contacted with human red blood cells, compared to Macrogenics anti-B7-H3 antibody (MG- B7-H3).

LIST OF SEQUENCES:

[00227] Human B7-H3 protein (UniProt Q5ZPR3-1) SEQ ID NO:1:

MLRRRGSPGMGVHVGAALGALWFCLTGALEVQVPEDPVVALVGTDATLCCSFSPEP GFSLAQLNLIWQLTDTKQLVHSFAEGQDQGSAYANRTALFPDLLAQGNASLRLQRV RVADEGSFTCFVSIRDFGSAAVSLQVAAPYSKPSMTLEPNKDLRPGDTVTITCSSYQG YPEAEVFWQDGQGVPLTGNVTTSQMANEQGLFDVHSILRVVLGANGTYSCLVRNP VLQQDAHSSVTITPQRSPTGAVEVQVPEDPVVALVGTDATLRCSFSPEPGFSLAQLNL IWQLTDTKQLVHSFTEGRDQGSAYANRTALFPDLLAQGNASLRLQRVRVADEGSFT CFVSIRDFGSAAVSLQVAAPYSKPSMTLEPNKDLRPGDTVTITCSSYRGYPEAEVFW QDGQGVPLTGNVTTSQMANEQGLFDVHSVLRVVLGANGTYSCLVRNPVLQQDAHG SVTITGQPMTFPPEALWVTVGLSVCLIALLVALAFVCWRKIKQSCEEENAGAEDQDG EGEGSKTALQPLKHSDSKEDDGQEIA. [00228] Recombinant truncated human his-tag B7-H3 protein (amino acids 1-461 of SEQ

ID NO:1 with a carboxy terminal polyhistidine tag) SEQ ID NO:2:

MLRRRGSPGMGVHVGAALGALWFCLTGALEVQVPEDPVVALVGTDATLCCSFSPEP

GFSLAQLNLIWQLTDTKQLVHSFAEGQDQGSAYANRTALFPDLLAQGNASLRLQRV

RVADEGSFTCFVSIRDFGSAAVSLQVAAPYSKPSMTLEPNKDLRPGDTVTITCSSYQG

YPEAEVFWQDGQGVPLTGNVTTSQMANEQGLFDVHSILRVVLGANGTYSCLVRNP

VLQQDAHSSVTITPQRSPTGAVEVQVPEDPVVALVGTDATLRCSFSPEPGFSLAQLNL

IWQLTDTKQLVHSFTEGRDQGSAYANRTALFPDLLAQGNASLRLQRVRVADEGSFT

CFVSIRDFGSAAVSLQVAAPYSKPSMTLEPNKDLRPGDTVTITCSSYRGYPEAEVFW

QDGQGVPLTGNVTTSQMANEQGLFDVHSVLRVVLGANGTYSCLVRNPVLQQDAHG

SVTITGQPMTHHHHHH.

[00229] Enoblituzumab (B7-H3 Macrogenics; MGA271 ; MG-B7-H3)

SEQ ID NOG:

Heavy Chain:

EVQLVESGGGLVQPGGSLRLSCAASGFTFSSFGMHWVRQAPGKGLEW

VAYISSDSSAIYYADTVKGRFTISRDNAKNSLYLQMNSLRDEDTAVYYCGRGR

ENIYY

GSRLDYWGQGTTVTVSSASTKGPSVFPLAPSSKSTSGGTAALGCLVKDYFPEPVTVS

W

NSGALTSGVHTFPAVLQSSGLYSLSSVVTVPSSSLGTQTYICNVNHKPSNTKVDKRVE

PK SCDKTHTCPPCPAPELVGGPSVFLLPP

KPKDTLMISRTPEVTCVVVDVSHEDPEVKFNW

YVDGVEVHNAKTKPPEEQYNSTLRVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIE KT

ISKAKGQPREPQVYTLPPSREEMTKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYK

TTPLVLDSDGSFFLYSKLTVDKSRWQQGNVFSCSVMHEALHNHYTQKSLSLSPGK.

SEQ ID NO:4:

Light Chain:

DIQLTQSPSFLSASVGDRVTITCKASQNVDTNVAWYQQKPGKAPKALIYS

ASYRYSGVPSRFSGSGSGTDFTLTISSLQPEDFATYYCQQYNNYPFTFGQGTKLEIKR

TVAAPSVFIFPPSDEQLKSGTASVVCLLNNFYPREAKVQWKVDNALQSGNSQESVTE QDSK DSTYSLSSTLTLSKADYEKHKVYACEVTHQGLSSPVTKSFNRGEC.

[00230] B7-H3 Memorial Sloan Kettering Cancer Center (MKSCC B7-H3, Hu8H9)

SEQ ID NOG:

Heavy Chain:

QVQLVQSGAEVVKPGASVKLSCKTSGYTFTNYDINWVRQRPGQGLEWIG

WIFPGDDSTQYNEKFKGKATLTTDTSTSTAYMELSSLRSEDTAVYFCARQTTGTWFA W GQGTLVTVSS.

SEQ ID NOG:

Light Chain:

EIVMTQSPATLSVSPGERVTLSCRASQSISDYLYWYQQKSHESPRLLIKYA SQSISGIPARFSGSGSGSEFTLTINSVEPEDVGVYYCQNGHSFPLTFGQGTKLELK.

[00231] Table 1:

[00232] EXAMPLES

[00233] The following examples are meant to be illustrative and can be used to further understand embodiments of the present disclosure and should not be construed as limiting the scope of the present teachings in any way.

[00234] Example 1: Measuring binding affinities using surface plasmon resonance.

[00235] Binding kinetics of anti-B7-H3 antibodies with his-tagged B7-H3 protein were measured using surface plasmon resonance (SPR). The anti-B7-H3 antibodies tested included an anti-B7-H3 antibody according to this disclosure (VA clone, the heavy chain variable region and the light chain variable region of which comprise the amino acid sequences of SEQ ID NOS: 10 and 11, respectively) and commercial B7-H3 antibody Enoblituzumab (MacroGenics). Anti-human fragment crystallizable region (Fc region) antibody, diluted in pH 5.0 acetate buffer, was immobilized on a CM5 sensor chip to approximately 8,000 RU using standard N-hydroxysuccinimide/l-Ethyl-3-(3- dimethylaminopropyl) carbodiimide hydrochloride (NHS/EDC) coupling methodology as automated by Biacore Model T200 (described in Biacore Concentration Analysis Handbook). [00236] Anti-B7-H3 antibody (VA clone) or Enoblituzumab (2 pg/mL) was captured for 60 seconds at a flow rate of 10 pL/minute. Recombinant human his-tagged B7-H3 protein included amino acid 1 to amino acid 461 of SEQ ID NO:1 (i.e., SEQ ID NO:2) (Sino Biologicals; Cat. No. 11188-H08H-50). This polypeptide was serially diluted 1:1 in a running buffer HBS-EP+ (Cytiva; Cat. No. BR100669) starting at 100 nM. All measurements were conducted in HBS-EP+ buffer with a flow rate of 30 pL/minute as automated by Biacore Model T200. Surfaces were regenerated with 3M MgCh for 60 sec. A 1:1 (Langmuir) binding model was used to fit the data. All BIACORE assays were performed at room temperature using Biacore Model T200 (GE Healthcare).

[00237] The SPR sensorgrams of anti-B7-H3 antibodies B7-H3 (VA clone) and Enoblituzumab are shown in FIGS. 1A-1B, respectively, and their corresponding binding kinetics are listed in Table 2 below. Both B7-H3 antibodies B7-H3 (VA clone) and Enoblituzumab showed an affinity in the nM range against their cognate antigen.

[00238] Table 2:

[00239] Example 2: Measuring antigen binding specificity by ELISA.

[00240] Anti-B7-H3 antibodies (VA clone and VA LALA clone) were analyzed for antigen binding specificity by ELISA assay focusing on human antigens B7-H1, B7-H2, B7- H3, B7-H4, B7-H5, B7-H6, B7-H7, B7.1, and B7.2 (Sino Biologicals). Each antigen protein was dissolved in PBS buffer (50 ng/well) and coated on a plate at 50|ll per well, overnight at 4°C. The plate was then washed three times with 150 pL/well KPL buffer (Sera Care; Cat. No. 5150-0008). Subsequently, the plate was blocked with 50 pL/well superblock buffer (Scytek; Cat. No. AAA500) for 1 hour at RT, gently shaken. The plates were washed 3 times with 150 pL/well of KPL buffer, after blocking. Anti-B7-H3 (VA clone or VA LALA clone) was serially diluted in another plate at 50 pL/well (mind triplicate) in superblock buffer. Diluted antibody was added (50 pL/well) into the coated plate and incubated for 1 hour at RT, gently shaken. The plate was washed three times with 150 pL/well of KPL buffer. 50 pL/well of HRP-conjugated detection antibody (Jackson Immuno Research; Cat. No. 109- 036-097) diluted 1:10,000 in KPL buffer was added, and incubated for 1 hour at RT, gently shaken. Subsequently, the plate was washed three times with 150 pL/well of KPL buffer and binding revealed by applying 50 pL/well of KPL SureBlue substrate (Sera Care; Cat. No. 5120-0075). The development of signal was stopped at the desired saturation point by using IN HC1 stop solution and read on a plate reader at 450 nm.

[00241] FIG. 2A shows that anti-B7-H3 antibody (VA clone) specifically binds to human B7-H3 antigen, and does not engage with human B7-H1, B7-H2, B7-H4, B7-H5, B7-H6, B7- H7, B7.1, or B7.2. FIG. 2B shows that anti-B7-H3 antibody (VA LALA clone) specifically binds to human B7-H3 antigen, and does not engage with human B7-H1, B7-H2, B7-H4, B7- H5, B7-H6, B7-H7, B7.1, or B7.2.

[00242] Example 3: ELISA cross-reactivity.

[00243] Cross -reactivity of the anti-human B7-H3 antibodies (B7-H3 VA and MG-B7-H3) with his-tagged B7-H3 recombinant protein from human, mouse, cynomolgus, canine, rat, and rabbit were analyzed using ELISA assay. Mouse antigen protein (Sino Biologicals; Cat. No. 50973-M08H-50), cynomolgus antigen protein (Sino Biologicals; Cat. No. 90806-C08H- 20), rat antigen protein (Sino Biologicals; Cat. No. 80380-R02H-20), rabbit antigen protein, canine antigen protein, or human antigen protein (Sino Biologicals; Cat. No. 11188-HO8H- 50), were dissolved in PBS buffer (50 ng/well) and coated on a plate at 50|ll per well, overnight at 4°C. The plate was then washed three times with 150 pL/well KPL buffer (Sera Care; Cat. No. 5150-0008). Subsequently, the plate was blocked with 50 pL/well superblock buffer (Scytek; Cat. No. AAA500) for 1 hour at RT, gently shaken. The plates were washed 3 times with 150 pL/well of KPL buffer, after blocking. Anti-B7-H3 (VA clone) or Enoblituzumab (MacroGenics MG-B7-H3) were serially diluted in another plate at 50 pL/well (mind triplicate) in superblock buffer. Diluted antibody was added (50 pL/well) into the coated plate and incubated for 1 hour at RT, gently shaken. The plate was washed three times with 150 pL/well of KPL buffer. 50 pL/well of HRP-conjugated detection antibody (Jackson Immuno Research; Cat. No. 109-036-097) diluted 1:10,000 in KPL buffer was added, and incubated for 1 hour at RT, gently shaken. Subsequently, the plate was washed three times with 150 pL/well of KPL buffer and binding revealed by applying 50 pL/well of KPL SureBlue substrate (Sera Care; Cat. No. 5120-0075). The signal was stopped at the desired saturation point by using IN HC1 stop solution and read on a plate reader at 450 nm. [00244] FIG. 3 shows that anti-B7-H3 antibody (VA clone) binds to canine, rat, rabbit, and cynomolgus B7-H3 antigen comparably to Macrogenics’ B7-H3.

[00245] Example 4: Thermostability of anti-B7-H3 antibody (VA clone).

[00246] The IgG protein thermostability was assessed by determining the melting temperature T_m of anti-B7-H3 antibody (VA clone). The antibody was diluted with PBS buffer to Img/ml and 9 pL of the antibody solution was loaded into UNI sample cartridge. The heating range was set from 30°C to 90°C, at a heating rate of 1°C per minute. The fluorescence was detected in the range of 250-720 nm. Curve calculation and fitting by barycentric mean fluorescence (BCM) was performed to assess the melting temperature of the antibody.

[00247] FIG. 4 shows improved antibody thermostability T_m>70°C, which contributes to antibody stability, promotes extended serum half-life and facilitates manufacturing.

[00248] Example 5: Anti-B7-H3 antibody (clone VA) antigen recognition in patient biopsies.

[00249] Anti-B7-H3 antibody (clone VA) antigen/target recognition capacity was tested in solid tumors, such as sarcoma, head & neck cancer, and pancreatic adenocarcinoma. Slides were baked at 60°C for 30 minutes up to 120 minutes on a heating block to prevent tissue detachment during antigen retrieval and to facilitate deparaffination. Subsequently, the slides were placed in a coupling jar (Fisher Scientific; 19-4) and further deparaffinized/rehydrated 3 times with Xylene for 5 minutes at RT. The slides were then bathed 2 times in 100% ethanol for 10 minutes at RT, followed by 2 times in 95% ethanol for 10 minutes at RT, 2 times in 70% ethanol for 10 minutes at RT, 2 times in 50% ethanol for 10 minutes at RT, and finally 2 times in DI water for 5 minutes at RT. Slide rack was submerged in antigen retrieval solution (Vector Laboratories: Cat. No. H3300-250), and then autoclaved at solid phase for 10 minutes. Subsequently, the slides were rinsed under cold tap water for 5 minutes. Pancreas cancer tissue (Biomax.US; Cat. No. HPan-Ade060CS-01), Sarcoma tissue (Biomax. US; Cat. No. SO809a), and head and neck cancer tissue (Biomax.US; Cat. No. T342) were fixed with 2% paraformaldehyde diluted in PBS for 15 minutes at RT. The slides were washed 3 times with PBS for 5 minutes at RT. The tissue slides were precipitated/permeabilized with ice cold methanol for 15 minutes at RT, and gently shaken. Subsequently, the slides were washed 3 times with PBS for 5 minutes at RT. Wax circles surrounding tissue biopsies were applied using ImmEdge Pen. Blocking buffer containing 1% mouse serum and 2.5% goat serum diluted in PBS was applied for 1 hour at RT. Then the tissue biopsies were washed in PBS and all remaining liquid was removed.

[00250] Antibody staining solution was prepared as follows: 1% mouse serum and 2.5% goat serum diluted in PBS and 1 pg/ml of anti-B7-H3 antibody (VA clone). Tissue biopsies were covered with primary antibody staining solution, placed in a wet chamber, and incubated overnight at 4°C. Then the tissue biopsies were washed in PBS and all remaining liquid was removed. Antibody staining solution was prepared as follows: 1% mouse serum and 2.5% goat serum diluted in PBS and fluorescently labeled secondary antibody diluted in the range 1:1000-1:25. Tissue biopsies were covered with secondary antibody staining solution, placed in a wet chamber, and incubated for 4 hours at RT. Then the tissue biopsies were washed in PBS and all remaining liquid was removed. Up to 25 |1L of Mowiol mounting solution (Sigma; Cat. No. 81381-250G) was applied (depending on the size of tissue biopsy) and covered with Microscope Cover Glass. Mowiol mounted biopsies were allowed to dry for 24 hours at RT (protected from light). Fluorescent emission was analyzed using confocal laser scanning microscope.

[00251] FIG. 5 shows human cancer tissue arrays (sarcoma, head and neck cancer and pancreatic adenocarcinoma) immune- stained with anti-B7-H3 antibody (VA clone) (greenish- gray) to assess antigen recognition in malignant patient tissue compared to adjacent normal tissue (bluish-gray). Anti-B7-H3 antibody (VA clone) shows elevated binding in malignant patient tissue biopsy, but no binding in adjacent normal tissue.

[00252] Example 6: Cell binding assay by flow cytometry.

[00253] Flow cytometry was used to test the binding capacity of anti-B7-H3 antibody (VA clone) to human osteosarcoma cells (U2OS) and human neuroblastoma cells (SK-N-BE(2)). Human U2OS (ATCC; Cat. No. HTB-96) and SK-N-BE(2) (ATCC; Cat. No. CRL-2271) cells were subcultured in McCoy’s 5a media (Thermo Fisher Scientific; Cat. No. 16600082) or EMEM:F12 1:1 media (ATCC; Cat. No. 30-2003: Thermo Scientific; Cat. No. 31765035) supplemented with 1% antibiotic s/antimycotics (Fisher Scientific; Cat. No. 15240062) and 10% FBS (Genesee Scientific; Cat. No. 25550). Cells were harvested using trypsin/EDTA (Thermo Fisher Scientific; Cat. No. 25300120), sedimented by centrifugation at 1500 rpm for 5 minutes and washed once with PBS (CellGro; Cat. No. 21-031-CM). Cells were stained with anti-RSV (control IgG), Enoblituzumab (Macrogenics), or anti-B7-H3 antibody (VA clone) diluted in staining buffer (PBS/1% BSA) or left unstained for 30 minutes at RT. Cells were washed once with PBS followed by centrifugation at 100 rpm for 5 minutes. For cells stained with anti-RSV, Enoblituzumab, or anti-B7-H3 antibody (VA clone), secondary antibody staining was performed using anti-human IgG 488 (Invitrogen; Cat. No. Al 1036) diluted at 1:200 in staining buffer for 30 minutes at RT. Cells were washed with PBS, sedimented at 1500 rpm for 5 minutes, resuspended in 300 pL staining buffer, followed by flow cytometry analysis using BD Accuri C6 plus cytometer. Data were collected and analyzed using FlowJo software.

[00254] FIG. 6A shows results of immuno staining of human osteosarcoma (U2OS) cells with anti-RSV (control IgG), Enoblituzumab or anti-B7-H3 antibody (VA clone), and the cells left unstained (control). FIG. 6A shows that anti-B7-H3 antibody (VA clone) exhibits stronger binding than Enoblituzumab at all concentrations. It also shows that anti-B7-H3 antibody (VA clone) distinctly binds U2OS cells even at concentrations as low as 0.01 pg/ml. [00255] FIG. 6B shows results of immuno staining of human neuroblastoma (SK-N-BE(2)) cells with anti-RSV (control IgG), Enoblituzumab or anti-B7-H3 antibody (VA clone), and the cells left unstained (control). FIG. 6B shows that anti-B7-H3 antibody (VA clone) exhibits stronger binding than Enoblituzumab at all concentrations. It also shows that anti B7-H3 antibody (VA clone) distinctly binds SK-N-BE(2) cells even at concentrations as low as 0.01 pg/ml.

[00256] Example 7: Antibody-dependent cell-mediated cytotoxicity (ADCC) prediction.

[00257] The NK cell recruitment potential of anti-B7-H3 antibody (VA clone) was predicted via an artificial ADCC assay. The artificial ADCC assay uses an engineered T-cell line which carries inducible luciferase transgene. Upon engagement of an IgG Fc moiety, resulting luminescence indicates antibody-to-cell interaction and serves to predict NK recruitment capacity by anti-B7-H3 antibody (VA clone).

[00258] Human osteosarcoma (U2OS) cells were cultured in McCoy’s 5a media (Thermo Fisher Scientific; Cat. No. 16600082) supplemented with 1% antibiotic s/antimycotics (Fisher Scientific; Cat. No. 15240062) and 10% FBS (Genesee Scientific; Cat. No. 25550). Cells were harvested using trypsin/EDTA (Thermo Fisher Scientific; Cat. No. 25300120), sedimented by centrifugation at 1500 rpm for 5 minutes and washed once with PBS (CellGro; Cat. No. 21-031-CM). Cells were counted and plated in 96-well plates at 3xl0³ cells/well. Antibodies (anti-B7-H3 antibody (VA clone) or Enoblituzumab) were added at indicated concentrations to each well. Effector cells (engineered Jurkat cells) (Promega, core kit; Cat. No. G7018) were added at 25:1 E:T ratio on 96-well plates. The target/effector cells were then incubated for 6 hours at 37°C, 5% CO2. Luciferase substrates (from the kit) were added to the wells, followed by incubation for 10 minutes at RT. Luminescence was read using Spark microplate reader, and data was analyzed.

[00259] FIG. 7A shows ADCC activity of anti-B7-H3 antibody (VA clone) and Enoblituzumab by luminescence acquisition. FIG. 7A shows that predicted ADCC capacity of anti-B7-H3 antibody (VA clone) surpasses the predicted ADCC capacity of Enoblituzumab. Additionally, it shows that anti-B7-H3 antibody (VA clone) has ADCC capacity even at low concentrations.

[00260] Example 8: Antibody-dependent cell-mediated cytotoxicity (ADCC) assay.

[00261] Human osteosarcoma (U2OS) cells were cultured in McCoy’s 5a media (Thermo Fisher Scientific; Cat. No. 16600082) or EMEM:F12 1:1 media (ATCC; Cat. No. 30-2003: Thermo Scientific; Cat. No. 31765035) supplemented with 1% antibiotic s/antimycotics (Fisher Scientific; Cat. No. 15240062) and 10% FBS (Genesee Scientific; Cat. No. 25550). Cells were harvested using trypsin/EDTA (Thermo Fisher Scientific; Cat. No. 25300120), sedimented by centrifugation at 1500 rpm for 5 minutes and washed once with PBS (CellGro; Cat. No. 21-031-CM). Cells were counted and plated in 96-well plates at 3xl0³ cells/well. Antibodies (anti-B7-H3 antibody (VA clone), Enoblituzumab or anti-RSV antibody) were added at indicated concentrations to each well. Effector cells (NK cells) were added at 25:1 E:T ratio on 96-well plates. NK cells were purified from human PBMC (ATCC; Cat. No. PCS 800011) using EasySep™ human NK cell enrichment kit following manufacturer’s instructions (Stemcell technologies; Cat. No. 19055). The target/effector cells were then incubated for 6 hours at 37°C, 5% CO2. Recombinant luciferase and its substrate (CellTiter- Glo; Promega; Cat. No. G7572) were added to the wells, followed by incubation for 10 minutes at RT to allow ATP-dependent enzymatic substrate turnover according to manufacturer’s instructions. Luminescence was read using Spark microplate reader, and data was analyzed.

[00262] FIG. 7B shows ADCC activity (by indirect killing) of anti-B7-H3 antibody (VA clone) compared to Enoblituzumab. FIG. 7B shows that anti-B7-H3 antibody (VA clone) mediated target cell killing by NK cells considerably surpasses Enoblituzumab mediated target cell killing.

[00263] FIG. 7C compares ADCC activity (by indirect killing) of anti-B7-H3 antibody (VA clone) compared to anti-RSV antibody (isotype IgG control). FIG. 7C shows that anti- RSV antibody does not have ADCC activity.

[00264] Example 9: Antigen-restricted target cell engagement ADCC assay.

[00265] To test whether anti-B7-H3 antibody (clone VA) mediated target cell engagement is restricted to its antigen, loss-of-function B7-H3 knockout cells were generated and compared to parental B7-H3⁺ cells in an artificial ADCC assay.

[00266] Human lung cancer A549 cells (wild type WT, or knockout KO for B7-H3) were cultured in F-12K cell culture media (ATCC; Cat. No. 30-2004) supplemented with 1% antibiotic s/antimycotics (Fisher Scientific; Cat. No. 15240062) and 10% FBS (Genesee Scientific; Cat. No. 25550). Cells were harvested using trypsin/EDTA (Thermo Fisher Scientific; Cat. No. 25300120), sedimented by centrifugation at 1500 rpm for 5 minutes and washed once with PBS (CellGro; Cat. No. 21-031-CM). Cells were counted and plated in 96- well plates at 3xl0³ cells/well. Antibodies (anti-B7-H3 antibody (VA clone) or Enoblituzumab) were added at indicated concentrations to each well. Effector cells (engineered Jurkat cells) (Promega, core kit; Cat. No. G7018) were added at 15:1 E:T ratio on 96-well plates. The target/effector cells were then incubated for 6 hours at 37°C, 5% CO2. Luciferase substrates (from the kit) were added to the wells, followed by incubation for 10 minutes at RT. Luminescence was read using Spark microplate reader, and data was analyzed.

[00267] FIG. 8A demonstrates the role of B7-H3 antigen in anti-B7-H3 antibody’s (clone VA) mediated cell engagement. Anti-B7-H3 antibody (clone VA) mediates cell engagement with B7-H3⁺ A549 lung cancer cells. FIG. 8B shows that upon loss of B7-H3 cell expression (A549 B7-H3 KO cells) anti-B7-H3 antibody (clone VA) mediated cell engagement is completely desensitized. Loss of B7-H3 expression is proportional to loss of luminescence.

[00268] Example 10: B7-H3 surface expression by A549 WT or A549 B7-H3 KO cells by flow cytometry.

[00269] Procedure for flow cytometric analysis was described above in Example 6, except in the instant procedure APC-labeled anti-human CD276 (B7-H3) antibody (Biolegend; 351006) was used (1:200) as the primary antibody for immunostaining of cells (instead of B7-H3 VA clone). Alternatively, the cells were unstained or stained with anti-RSV antibody for isotype control.

[00270] FIG. 9 shows the B7-H3 surface expression by A549 WT cells and A549 B7-H3 KO (knockout) cells. Gating is focused on B7-H3 expressing cells, expressed as % of population. FIG. 9 demonstrates that B7-H3 is expressed only by A549 WT cells.

[00271] Example 11: In vivo efficacy study of anti-B7-H3 clone VA in human neuroblastoma tumor model.

[00272] Human neuroblastoma tumor growth kinetics was assessed following high frequency dosing or low frequency dosing with anti-B7-H3 antibody (clone VA). Human neuroblastoma cells (SK-N-BE(2)) were cultured in EMEM:F12 1:1 cell culture media (ATCC; Cat. No. 30-2003: Thermo Scientific; Cat. No. 31765035) supplemented with 1% antibiotic s/antimycotics (Fisher Scientific; Cat. No. 15240062) and 10% FBS (Genesee Scientific; Cat. No. 25550). Cells were harvested using trypsin/EDTA (Thermo Fisher Scientific; Cat. No. 25300120), sedimented by centrifugation at 1500 rpm for 5 minutes and resuspended in HBSS/Matrigel mixed at 1:1 ratio (Corning; Cat. Nos. 21-022-CM and 356237) to provide 5xl0⁶ cells/100 pL HBSS/Matrigel. SCID mice underwent hair removal procedure using hair removal cream (Nair) 24 hours before tumor cell inoculation. On day 0 each mouse received 100 pL HBSS/Matrigel with 5xl0⁶ cells in their shaved flanks subcutaneously. Starting on day 4, once tumors reached volume of 50-100 mm³, tumor bearing mice were randomized and (N=8 for all groups) underwent systemic treatment at indicated doses and frequencies (see paragraph [00161] below). Tumor bearing mice were administered - 200 pL HBSS (buffer control), anti-RSV antibody (isotype control, 10 mg/kg), or various doses of anti-B7-H3 antibody (clone VA) diluted in HBSS - systematically via retro-orbital route. For dose administration, mice were anaesthetized using 2-4% isoflurane/oxygen.

[00273] Mice were dosed at 1 mg/kg, 5 mg/kg or 10 mg/kg every other day three times per week (for high frequency dosing experiments), or at 0.1 mg/kg, 1 mg/kg or 10 mg/kg once per two weeks (for low frequency dosing experiments). Tumor dimensions were assessed using calipers. Tumor volume was calculated as volume=l/2xlengthxwidth².

[00274] FIG. 10 shows the effect of 1 mg/kg, 5 mg/kg or 10 mg/kg of anti-B7-H3 antibody (clone VA) and 10 mg/kg of isotype control (anti-RSV), when administered every other day three times per week, on the tumor volume - averaged for 8 mice, measured over 36 days. **P<0.01; ***P<0.001 conducted between vehicle group and anti-B7-H3 antibody (VA clone) groups, is considered statistically significant.

[00275] FIG. 11 shows the effect of 0.1 mg/kg, 1 mg/kg or 10 mg/kg of anti-B7-H3 antibody (clone VA) and 10 mg/kg of isotype control (anti-RSV), when administered once per two weeks, on the tumor volume - averaged for 8 mice, measured over 32 days. **P<0.01; ***P<0.001 conducted between vehicle group and anti-B7-H3 antibody (VA clone) groups, is considered statistically significant.

[00276] FIGS. 10 and 11 show that anti-B7-H3 antibody (VA clone) administered systematically reduces tumor growth kinetics at doses as low as 1 mg/kg. Anti-B7-H3 antibody (VA clone) treatment reduces tumor growth kinetics in a dose-dependent manner.

[00277] Example 12: Hemagglutination assessment of anti-B7-H3 clone VA.

[00278] Hemagglutination of red blood cells (RBCs) was assessed in the presence of anti- B7-H3 antibodies - STI-B7-H3-VA (this name was used interchangeably with B7-H3 VA clone), B7-H3-VA LALA, anti-CD47 Hu5F9 (HC MEWSWVFLFFLSVTTGVHSQVQLVQSGAEVKKPGASVKVSCKASGYTFTNYNMH WVRQAPGQRLEWMGTIYPGNDDTSYNQKFKDRVTITADTSASTAYMELSSLRSEDT AVYYCARGGYRAMDYWGQGTLVTVSSASTKGPSVFPLAPCSRSTSESTAALGCLVK DYFPEPVTVSWNSGALTSGVHTFPAVLQSSGLYSLSSVVTVPSSSLGTKTYTCNVDH KPSNTKVDKRVESKYGPPCPPCPAPEFLGGPSVFLFPPKPKDTLMISRTPEVTCVVVD VSQEDPEVQFNWYVDGVEVHNAKTKPREEQFNSTYRVVSVLTVLHQDWLNGKEYK CKVSNKGLPSSIEKTISKAKGQPREPQVYTLPPSQEEMTKNQVSLTCLVKGFYPSDIA VEWESNGQPENNYKTTPPVLDSDGSFFLYSRLTVDKSRWQEGNVFSCSVMHEALHN HYTQKSLSLSLGK (SEQ ID NO: 113) and LC MEWSWVFLFFLSVTTGVHSDIVMTQSPLSLPVTPGEPASISCRSSQSIVYSNGNTYLG WYLQKPGQSPQLLIYKVSNRFSGVPDRFSGSGSGTDFTLKISRVEAEDVGVYYCFQG SHVPYTFGQGTKLEIKRTVAAPSVFIFPPSDEQLKSGTASVVCLLNNFYPREAKVQW KVDNALQSGNSQESVTEQDSKDSTYSLSSTLTLSKADYEKHKVYACEVTHQGLSSPV TKSFNRGEC (SEQ ID NO: 114) ), and MG-B7-H3 (i.e., enoblituzumab).

[00279] Red blood cells (RBCs) were prepared from human patient blood by mixing 1 ml blood with 14 ml PBS in a 15 ml Falcon tube and centrifuged at 800 rpm for 10 min at RT. Supernatant was discarded and another 15 ml PBS was added to the cell pellet and centrifugation was repeated. 9 ml PBS was added to cell pellet producing a 10% STOCK solution of RBCs. RBC number was determined.

[00280] 0.5% RBC working solution was prepared by diluting the 10% STOCK solution in assay buffer (2% FBS, 2 mM EDTA in DBPS).

[00281] 50 pl/well of working solution was added to a U-bottom low-adhesive 96-well plate. The following antibodies were used in this assay: anti-CD47 Hu5F9, B7-H3-VA (anti- B7-H3), B7-H3-VA LALA (anti-B7-H3), MG-B7-H3 (anti-B7-H3, Enoblituzumab from MacroGenics), and isotype control (anti-RSV antibody). Serial dilutions of antibodies were made in PBS (1:5 serial dilution). The antibody dilutions were transferred into the plate containing RBCs (100 pL/well, starting antibody concentration: 100 pg/mL). The plates were incubated for 24 hours at 37°C, and images acquired. In a similar experiment, 1 :2 serial dilution was performed starting at 200 pg/ml, and B7-H3 VA antibody did not show any hemagglutination even at 200 pg/ml.

[00282] Negative results (no hemagglutination) appear as red dots in the centre of round- bottomed plates. Positive results (hemagglutination) will form a uniform reddish color across the well.

[00283] FIG. 12A provides a diagram and example of positive and negative results. FIGS. 12B and 12C (plate images) show the results of the assay. In FIG. 12B MG-B7-H3 antibody induces hemagglutination in the wells corresponding to antibody concentrations starting from 100 pg/mL, with hemagglutination disappearing at antibody concentration of 50 g/mL and below. In contrast, even at the highest antibody concentration of STI-B7-H3-VA (200 pg/mL), hemagglutination is not apparent. Positive control antibody Hu5F9 induces hemagglutination in the wells corresponding to antibody concentrations starting from 0.032 pg/mL. Negative control non-binding anti-RSV antibody (Isotype control) did not induce hemagglutination at any concentration. In FIG. 12C MG-B7-H3, B7-H3-VA LALA, and isotype control (anti-RSV) antibodies did not induce hemagglutination up to the maximum antibody concentration tested (100 pg/mL). Positive control antibody Hu5F9 induces hemagglutination in the wells corresponding to antibody concentrations starting from 0.16 pg/mL.

[00284] Conclusion: Neither STI-B7-H3-VA nor B7-H3-VA LALA antibodies induce hemagglutination even at high concentration, up to 200 pg/mL.

[00285] Example 13: Cell binding activity of B7-H3 clone VA measured by flow cytometry.

[00286] Flow cytometry was used to test the binding capacity of anti-B7-H3 antibody (VA clone) to human melanoma cells (A375), human lung carcinoma cells (A549), and human pancreatic carcinoma cells (Panc-1).

[00287] Human cancer cell lines were sub-cultured at conditions with media as recommended by the vendor, briefly, human malignant melanoma A375 and human pancreatic carcinoma PANC-1 cells were cultured with DMEM media, human lung carcinoma A549 cells were cultured with F-12K media, all cell culture media were supplemented with 10% FBS and antibiotic s/antimy cotic s .

[00288] Cells were harvested with DPBS containing 10 mM EDTA and plated at 100,000 cells/well suspended in 50 pl staining buffer (1% BSA in DPBS) in a 2 ml deep-well 96-well plate. The following antibodies were used in this assay: B7-H3-VA (anti-B7-H3), MG-B7-H3 (anti-B7-H3, Enoblituzumab from MacroGenics), and isotype control (anti-RSV antibody). Serial dilutions of antibodies were made in staining buffer (1:5 serial dilution) (containing 1% BSA in DPBS) starting at 100 pg/ml final concentration (with 200 pg/ml being prepared).

[00289] The antibody dilutions were transferred into the plate containing the cells (50 pL/well antibody was added to each well; starting antibody concentration: 100 pg/mL). The plate was incubated for 25 minutes at 37°C, then washed with 1 ml/well staining buffer (1% BSA in DPBS), centrifuged at 1,500 rpm for 3 min at RT, and the supernatant was discarded. [00290] 100 |ll of fluorescently labelled secondary antibody diluted 1:500 in staining buffer (1% BSA in DPBS) was added to each well, and the plate was incubated for 20 min at 37°C. The plate was washed with 1 ml staining buffer (1% BSA in DPBS), and centrifuged at 1,500 rpm for 3 min at RT. 100 |ll cold fixation buffer (4% paraformaldehyde in PBS) was added to each well and the plate was incubated for 20 min at 37°C (protected from light). Then 100 |ll of staining buffer was added to each well and the cells were analyzed by flow cytometry using an AttuneNXT instrument. The collected data was analyzed by FlowJo vlO software converting to raw fluorescence to values of the geometric mean fluorescence. [00291] Dose-dependent binding of antibodies was conducted in triplicates and acquired by flow cytometry. FIG. 13 shows results of immuno staining of human melanoma cells (A375), human lung carcinoma cells (A549), or human pancreatic carcinoma cells (Panc-1) with anti-RSV (isotype control IgG), Macrogenics (MG-B7-H3 antibody), or anti-B7-H3 antibody (VA clone). FIG. 13 demonstrates that MG-B7-H3 has reduced binding, in all 3 cell types, as compared to B7-H3- VA. B7-H3-VA exhibits 10-100-fold stronger cell binding activity (cell type dependent) than MG-B7-H3. B7-H3-VA shows binding to human cancer cells A375, A549 and Panc-1 at very low concentrations (even at 0.0001 |lg/ml).

[00292] Example 14: Receptor occupancy of B7-H3 clone VA measured by flow cytometry.

[00293] Flow cytometry was used to measure the receptor engagement of anti-B7-H3 antibody (VA clone) to human melanoma cells (A375), human lung carcinoma cells (A549), and human pancreatic carcinoma cells (Panc-1).

[00294] Human cancer cell lines were sub-cultured at conditions with media as recommended by the vendor, briefly, human malignant melanoma A375 and human pancreatic carcinoma PANC-1 cells were cultured with DMEM media, human lung carcinoma A549 cells were cultured with F-12K media, all cell culture media were supplemented with 10% FBS and antibiotic s/antimycotics.

[00295] Cells were detached from culture dishes with Cell Dissociation Buffer according to the manufacturer’s instructions and plated at 100,000 cells/well suspended in 50 pl assay buffer (4% FBS in RPMI1640 media) in a 96-well U-bottom plate immediately prior to antibody application. [00296] All antibodies were fluorescently labelled (in-house) with a fluorophore excitable at 647 nm (near-infrared, nIR).

[00297] The following antibodies were used in this assay: B7-H3-VA (anti-B7-H3), B7- H3 MG (anti-B7-H3, Enoblituzumab from MacroGenics), and isotype control (anti-RSV antibody).

[00298] Serial dilutions (1:5 dilution) of AF647 labelled antibodies were made in assay buffer (4% FBS in RPMI1640) starting at 100 pg/ ml final concentration (with 200 pg/ml being prepared).

[00299] Cells were incubated on ice (4°C) in the dark for 1 hour before being centrifuged at 300 g for 5 minutes to pellet cells (supernatant discarded). Cells were washed three times with washing buffer (2% FBS, 5 mM EDTA diluted in DPBS) and centrifuged at 300 g for 5 minutes to pellet cells (supernatant discarded). The plate was analyzed by flow cytometry using AttuneNXT instrument and quantified using Bangslabs AF647 quantification beads. [00300] Standard curve was generated using MESF (molecules of equivalent soluble fluorochrome). MESF standard microsphere solution was prepared by dilution in assay buffer per manufacturer’s instructions. Alexa Fluor 647 fluorescently labelled MESF beads were read by the cytometer and values were entered into the “QuickCal Template” to generate a regression curve according to the manufacturer’s instructions.

[00301] Differences in fluorophore to antibody (F/P) ratio were adjusted by normalization to known F/P ratio for each antibody conjugate to yield the geometric mean of total antibodies bound. The collected data was analyzed by FlowJo vlO software converting raw fluorescence to values of the geometric mean fluorescence. Kd [pg/ml] and B_max were calculated using the fitted standard curve according to the manufacturer’s instructions using the GraphPad software

[00302] FIG. 14 shows that B7-H3-VA displays significantly elevated engagement to surface antigen expressed by human cancer cells A375, A549 and Panc-1. B7-H3-VA displays higher receptor engagement activity compared to MG-B7-H3.

[00303] Example 15: Receptor occupancy of B7-H3 clone VA (with LALA mutation in the Fc region) measured by flow cytometry.

[00304] Flow cytometry was used to measure the receptor engagement of anti-B7-H3-VA antibody (with LALA mutation in the Fc region) to human melanoma cells (A375), human lung carcinoma cells (A549), and human pancreatic carcinoma cells (Panc-1). [00305] The assay was carried out according to methods described in Example 14 above. The following antibodies were used in this assay: B7-H3-VA-LALA (anti-B7-H3), B7-H3 MG (anti-B7-H3, Enoblituzumab from MacroGenics), and isotype control (anti-RSV antibody).

[00306] FIG. 15 shows that B7-H3-VA LALA displays significantly elevated engagement to surface antigen expressed by human cancer cells A375, A549 and Panc-1. B7-H3-VA LALA displays comparable receptor engagement activity to the parental B7-H3-VA antibody, and significantly higher receptor engagement activity compared to MG-B7-H3 antibody (Macrogenics).

[00307] Example 16: Restoration of CD4+ T cell proliferation with B7-H3-VA.

[00308] Efficacy of B7-H3-VA antibody was tested based on its ability to restore CD4+ T cell proliferation. sB7-H3 (soluble B7-H3) polypeptide is a known inhibitor of activation and proliferation of CD4+ T cells, contributing to tumor cell immune evasion. Restoration of CD4+ T cell proliferation was assessed using B7-H3-VA antibody, and isotype control (anti- RSV antibody).

[00309] CD4+ T cells were isolated by negative isolation from human blood according to the manufacturer’s instructions. CD4+ T cells underwent staining with CFSE cell permeant dye in 5 ml PBS for 20 min at 37°C according to the manufacturer’s instructions. 10 ml RPMI1640 supplemented with 10% FBS was added to the CD4+ T cells, and the cells were incubated for 10 min at RT. The cells were centrifuged at 1,500 rpm for 3 min at RT, and the supernatant was discarded. The cells were resuspended in RPMI1640 supplemented with 10% FBS and then plated - 500 pl/well (500,000 cells) in a 48-well plate.

[00310] 500 ng/ml of anti-CD3 antibody was added to each well (to trigger CD4+ T cell proliferation), followed by addition of soluble B7-H3 polypeptide (sB7-H3, 0.5 pg/well).

[00311] Finally, 50 pg/ we 11 anti-B7-H3-VA antibody or isotype control (anti-RSV antibody) (300 nM antibodies) were added to the plate, and it was incubated for 72 h at 37°C. [00312] The cells were fixed with 2% paraformaldehyde diluted in PBS for 20 min at RT, and CFSE fluorescence was acquired by flow cytometry. Analysis gating excluding cell debris and whole cell populations were subjected to automated proliferation modeling provided by FlowJo software.

[00313] Panel 1 of FIG. 16 shows CFSE fluorescence of CD4+ T cells on day 0, panel 2 shows CFSE fluorescence of CD4+ T cells after 72 hours. Panel 3 of FIG. 16 demonstrates that addition of anti-CD3 antibody enhances proliferation of CD4+ T cells. Panel 4 of FIG.

16 demonstrates that addition of sB7-H3 polypeptide blocks (and reverses) the proliferation of CD4+ T cells. Panel 5 of FIG. 16 demonstrates that addition of anti-B7-H3-VA antibody (following the addition of sB7-H3) restores the proliferation of CD4+ T cells (by blocking the B7-H3 receptor). Panel 5 of FIG. 16 demonstrates that addition of anti-RSV (nontargeting) antibody does not restore proliferation of CD4+ T cells. CD4+ T cell proliferation was acquired by flow cytometry assessing cell division by CFSE dilution of dividing T cells. [00314] Conclusion: FIG. 16 shows that B7-H3-VA restores the proliferation of CD4+ T cells, counteracting the T cell suppressing activity of soluble B7-H3 polypeptide. Thus, demonstrating the efficacy of B7-H3-VA antibody as a blocking antibody.

[00315] Example 17: Antibody-dependent cell-mediated cytotoxicity (ADCC) efficacy loss-of-function.

[00316] Antibody mediated recruitment potential of effector cells is assessed by a reporter assay. The following antibodies were compared in this assay: B7-H3-VA and B7-H3-VA LALA (anti-B7-H3), MG-B7-H3 (anti-B7-H3, Enoblituzumab from MacroGenics), and isotype control (anti-RSV antibody).

[00317] 5 ,000 human melanoma target cells/well (A375) were plated (100 pl/wcll) in a 96- well plate and incubated overnight at 37°C.

[00318] Serial dilutions of the antibodies were prepared in ADCC assay buffer according to the manufacturer’s instructions. 95 pl/wcll cell solution was removed, and 25 pl/wcll assay buffer was added, followed by addition of 25 pl/wcll of the serially diluted antibody solution. Then 25 pl/well effector cells (engineered Jurkat cells expressing NF AT luciferase; = 75,000 cells/well) were added to achieve a 1:15 ratio of target:effector cell, and the plate was incubated for 6 h at 37°C. Following incubation, 40 pl/wcll of OneGlo™ luciferase substrate solution was added to the plate and the plate was incubated for 5-10 min at RT. Induced bioluminescence was acquired using a plate reader.

[00319] FIG. 17 displays the results of two independently performed experiments (R1 and R2 which are repeats of the same experiment). Both graphs in FIG. 17 show that LALA mutation in the Fc region of the anti-B7-H3-VA antibody results in loss-of -function, i.e., the antibody does not induce cell-engagement-dependent bioluminescence, compared to the parental B7-H3-VA antibody or MG-B7-H3 (Macrogenics) antibody. [00320] Example 18: Red blood cell (RBC) binding activity measured by flow cytometry.

[00321] Flow cytometry was used to test the binding capacity of anti-B7-H3 antibodies (MG-B7-H3, VA clone and VA LALA clone), isotype control antibody (anti-RSV), and anti- CD47 Hu5F9 antibody to human red blood cells (RBCs).

[00322] RBCs from three donors were prepared as described above in Example 12 (paragraph [00267]).

[00323] Antibody immunostaining: The following antibodies were used in this assay: B7- H3-VA (anti-B7-H3), B7-H3-VA LALA (anti-B7-H3), MG-B7-H3 (anti-B7-H3, Enoblituzumab from MacroGenics), Hu5F9 (anti-CD47 antibody), and isotype control (anti- RSV antibody). Serial dilutions of antibodies were made in staining buffer (1:5 serial dilution) (containing 1% BSA in DPBS) starting at 100 pg/ml final concentration (with 200 pg/ml being prepared).

[00324] The antibody dilutions were transferred into the plate containing 100 pl/well RBCs (50 pL/well antibody was added to each well; starting antibody concentration: 100 pg/mL) and mixed gently. The plate was incubated for 25 minutes at 37°C, then washed with 1 ml/well staining buffer (1% BSA in DPBS), centrifuged at 1,500 rpm for 3 min at RT, and the supernatant was discarded.

[00325] 100 pl of fluorescently labelled secondary antibody diluted 1:500 in staining buffer (1% BSA in DPBS) was added to each well, and the plate was incubated for 20 min at 37°C. The plate was washed twice with 200 pl/well of staining buffer (1% BSA in DPBS), and centrifuged at 1,500 rpm for 3 min at RT, and supernatant was removed. Then 100 pl of staining buffer was added to each well and the cells were analyzed by flow cytometry using an AttuneNXT instrument. The collected data was analyzed by FlowJo vlO software converting raw fluorescence to values of the geometric mean fluorescence.

[00326] Dose-dependent binding of antibodies was conducted in triplicates and acquired by flow cytometry. FIG. 18 shows results of immuno staining of human RBCs with anti-RSV (isotype control IgG), Macrogenics (MG-B7-H3 antibody), anti-B7-H3 antibody (VA clone and VA LALA clone), and Hu5F9 (anti-CD47 antibody). FIG. 18 shows that only Hu5F9 (anti-CD47 antibody) exhibits RBC binding, whereas MG-B7-H3 antibody, anti-B7-H3 antibody (VA clone and VA LALA clone), and anti-RSV (isotype control IgG) did not exhibit any appreciable RBC binding. [00327] Example 19: Measuring binding affinities using surface plasmon resonance.

[00328] Binding kinetics of anti-B7-H3 antibodies with his-tagged B7-H3 protein were measured using surface plasmon resonance (SPR). The anti-B7-H3 antibodies tested included proprietary antibodies (B3-A6, B3-4A1, B3-4F7, B3-D1, B3-2D1, B3-2H1, B3-2E3, and B3-5A6). Anti-human Fc antibody from Human Antibody Capture Kit (Cytiva; Cat No. BR100839) was immobilized on a CM5 sensor chip to approximately 5,000 RU using standard N -hydroxy succinimide/ 1 -Ethyl-3 -(3 -dimethylaminopropyl) carbodiimide hydrochloride (NHS/EDC) coupling methodology.

[00329] Anti-B7-H3 antibodies (approximately 5 pg/mL) were captured for 60 seconds at a flow rate of 10 pL/minute. Recombinant human his-tagged B7-H3 protein included amino acid 1 to amino acid 461 of SEQ ID NO:1 (i.e., SEQ ID NO:2) (Sino Biologicals; Cat. No. 11188-H08H-50). This polypeptide was serially diluted 1:1 in a running buffer HBS-EP (Cytiva; Cat. No. BR1OO188) starting at 100 nM. All measurements were conducted in HBS- EP buffer with a flow rate of 30 pL/minute as automated by BIAcore 3000. Surfaces were regenerated with 3M MgCh for 60 sec. A 1:1 (Langmuir) binding model was used to fit the data. All BIACORE assays were performed at room temperature using BIAcore 3000 (GE Healthcare).

[00330] The SPR sensorgrams of anti-B7-H3 antibodies are shown in FIG. 19, and their corresponding binding kinetics are listed in Table 3 below. All B7-H3 antibodies showed an affinity in the nM range against their cognate antigen.

[00331] Table 3:

[00332] Example 20: Cell binding activity of B7-H3 clones (B3-5A6, B3-2E3, B3-2D1, B3-D1, B3-2G11, B3-4A1) measured by flow cytometry.

[00333] Flow cytometry was used to test the binding capacity of anti-B7-H3 antibodies (B3-5A6, B3-2E3, B3-2D1, B3-D1, B3-2G11, B3-4A1) to dendritic cells (DC).

[00334] Dendritic cells were prepared by culturing purified monocytes with granulocytemacrophage colony- stimulating factor (GM-CSF) 1,000 U/mL plus interleukin 4 (IL-4) 500 U/mL for 6-7 days.

[00335] Monocytes were obtained from peripheral blood mononuclear cells (PBMCs) by reactivity to biotin anti-human CD 14, followed the addition of magnetic anti-biotin beads and separation by passage over a column attached to a magnet. This typically resulted in a population of >90% pure CD 14 positive monocytes.

[00336] MSKCC B7-H3 a B7-H3 antibody of Memorial Sloan Kettering Cancer Center was expressed in-house and used as positive control.

[00337] Test antibodies (B3-5A6, B3-2E3, B3-2D1, B3-D1, B3-2G11, B3-4A1, and a positive control MSKCC B7-H3) were added to the cells at a final concentration of 10 mg/ml, 1 mg/ml, or 0.1 mg/ml. After 20 minutes at 4°C, the cells were washed, then resuspended in PBS + 1%FCS containing APC-conjugated goat anti-human IgG at a 1:1,000 dilution. After 20 minutes at 4°C, the cells were washed and resuspended in PBS + 1%FCS and analyzed by flow cytometry.

[00338] FIG. 20 shows results of B7-H3 antibodies binding to dendritic cells. FIG. 20 shows that some anti-B7-H3 antibodies (B3-5A6, B3-2D1, and B3-4A1) exhibit stronger binding than MKSCC B7-H3 control antibody at some if not all concentrations. It also shows that anti-B7-H3 antibodies (B3-2D1 and B3-4A1) distinctly binds dendritic cells even at concentrations as low as 0.1 pg/ml.

[00339] The detailed description set-forth above is provided to aid those skilled in the art in practicing the present invention. However, the invention described and claimed herein is not to be limited in scope by the specific embodiments herein disclosed because these embodiments are intended as illustration of several aspects of the invention. Any equivalent embodiments areintended to be within the scope of this invention. Indeed, various modifications of the invention in addition to those shown and described herein will become apparent to those skilled in the art from the foregoing description which do not depart from the spirit or scope of the present inventive discovery. Such modifications are also intended to fall within the scope of the appended claims.

[00340] All publications, patents, patent applications and other references cited in this application are incorporated herein by reference in their entirety for all purposes to the same extent as if each individual publication, patent, patent application or other reference was specifically and individually indicated to be incorporated by reference in its entirety for all purposes. Citation of a reference herein shall not be construed as an admission that such is priorart to the present invention.

Claims

What is claimed:

1. An anti-B7-H3 antigen-binding protein or fully human anti-B7-H3 antibody, or an antigen-binding fragment thereof, comprising a heavy chain variable region and a light chain variable region, wherein the heavy chain variable region comprises a heavy chain complementarity determining region 1 CDR1, a heavy chain CDR2, and a heavy chain CDR3, and the light chain variable region comprises a light chain CDR1, a light chain CDR2, and a light chain CDR3; and a. the heavy chain CDR1 has the amino acid sequence of SEQ ID NO: 12, the heavy chain CDR2 has the amino acid sequence of SEQ ID NO: 13, the heavy chain CDR3 has the amino acid sequence of SEQ ID NO: 14, the light chain CDR1 has the amino acid sequence of SEQ ID NO: 15, the light chain CDR2 has the amino acid sequence of SEQ ID NO: 16, and the light chain CDR3 has the amino acid sequence of SEQ ID NO: 17; or b. the heavy chain CDR1 has the amino acid sequence of SEQ ID NO:22, the heavy chain CDR2 has the amino acid sequence of SEQ ID NO:23, and the heavy chain CDR3 has the amino acid sequence of SEQ ID NO:24, and the light chain CDR1 has the amino acid sequence of SEQ ID NO:25, the light chain CDR2 has the amino acid sequence of SEQ ID NO:26, and the light chain CDR3 has the amino acid sequence of SEQ ID NO:27; or c. the heavy chain CDR1 has the amino acid sequence of SEQ ID NO:32, the heavy chain CDR2 has the amino acid sequence of SEQ ID NO:33, and the heavy chain CDR3 has the amino acid sequence of SEQ ID NO:34, and the light chain CDR1 has the amino acid sequence of SEQ ID NO:35, the light chain CDR2 has the amino acid sequence of SEQ ID NO:36, and the light chain CDR3 has the amino acid sequence of SEQ ID NO:37; or d. the heavy chain CDR1 has the amino acid sequence of SEQ ID NO:42, the heavy chain CDR2 has the amino acid sequence of SEQ ID NO:43, and the heavy chain CDR3 has the amino acid sequence of SEQ ID NO:44, and the light chain CDR1 has the amino acid sequence of SEQ ID NO:45, the light chain CDR2 has the amino acid sequence of SEQ ID NO:46, and the light chain CDR3 has the amino acid sequence of SEQ ID NO:47; or e. the heavy chain CDR1 has the amino acid sequence of SEQ ID NO:52, the heavy chain CDR2 has the amino acid sequence of SEQ ID NO:53, and the heavy chain CDR3 has the amino acid sequence of SEQ ID NO:54, and the light chain CDR1 has the amino acid sequence of SEQ ID NO: 55, the light chain CDR2 has the amino acid sequence of SEQ ID NO:56, and the light chain CDR3 has the amino acid sequence of SEQ ID NO:57; or f. the heavy chain CDR1 has the amino acid sequence of SEQ ID NO:62, the heavy chain CDR2 has the amino acid sequence of SEQ ID NO:63, and the heavy chain CDR3 has the amino acid sequence of SEQ ID NO:64, and the light chain CDR1 has the amino acid sequence of SEQ ID NO:65, the light chain CDR2 has the amino acid sequence of SEQ ID NO:66, and the light chain CDR3 has the amino acid sequence of SEQ ID NO:67; or g. the heavy chain CDR1 has the amino acid sequence of SEQ ID NO:72, the heavy chain CDR2 has the amino acid sequence of SEQ ID NO:73, and the heavy chain CDR3 has the amino acid sequence of SEQ ID NO:74, and the light chain CDR1 has the amino acid sequence of SEQ ID NO:75, the light chain CDR2 has the amino acid sequence of SEQ ID NO:76, and the light chain CDR3 has the amino acid sequence of SEQ ID NO:77; or h. the heavy chain CDR1 has the amino acid sequence of SEQ ID NO:82, the heavy chain CDR2 has the amino acid sequence of SEQ ID NO:83, and the heavy chain CDR3 has the amino acid sequence of SEQ ID NO:84, and the light chain CDR1 has the amino acid sequence of SEQ ID NO: 85, the light chain CDR2 has the amino acid sequence of SEQ ID NO:86, and the light chain CDR3 has the amino acid sequence of SEQ ID NO:87; or i. the heavy chain CDR1 has the amino acid sequence of SEQ ID NO:92, the heavy chain CDR2 has the amino acid sequence of SEQ ID NO:93, and the heavy chain CDR3 has the amino acid sequence of SEQ ID NO:94, and the light chain CDR1 has the amino acid sequence of SEQ ID NO:95, the light chain CDR2 has the amino acid sequence of SEQ ID NO:96, and the light chain CDR3 has the amino acid sequence of SEQ ID NO:97; or j. the heavy chain CDR1 has the amino acid sequence of SEQ ID NO: 102, the heavy chain CDR2 has the amino acid sequence of SEQ ID NO: 103, and the heavy chain CDR3 has the amino acid sequence of SEQ ID NO: 104, and the light chain CDR1 has the amino acid sequence of SEQ ID NO: 105, the light chain CDR2 has the amino acid sequence of SEQ ID NO: 106, and the light chain CDR3 has the amino acid sequence of SEQ ID NO: 107. The antigen-binding protein, antibody or antigen-binding fragment thereof of claim 1, wherein: a. the heavy chain variable region has at least 95% sequence identity to the amino acid sequence of SEQ ID NO: 10, and the light chain variable region has at least 95% sequence identity to the amino acid sequence of SEQ ID NO: 11; or b. the heavy chain variable region has at least 95% sequence identity to the amino acid sequence of SEQ ID NO:20, and the light chain variable region has at least 95% sequence identity to the amino acid sequence of SEQ ID NO:21; or c. the heavy chain variable region has at least 95% sequence identity to the amino acid sequence of SEQ ID NO:30, and the light chain variable region has at least 95% sequence identity to the amino acid sequence of SEQ ID NO:31; or d. the heavy chain variable region has at least 95% sequence identity to the amino acid sequence of SEQ ID NO:40, and the light chain variable region has at least 95% sequence identity to the amino acid sequence of SEQ ID NO:41; or e. the heavy chain variable region has at least 95% sequence identity to the amino acid sequence of SEQ ID NO:50, and the light chain variable region has at least 95% sequence identity to the amino acid sequence of SEQ ID NO:51; or f. the heavy chain variable region has at least 95% sequence identity to the amino acid sequence of SEQ ID NO: 60, and the light chain variable region has at least 95% sequence identity to the amino acid sequence of SEQ ID NO:61; or g. the heavy chain variable region has at least 95% sequence identity to the amino acid sequence of SEQ ID NO:70, and the light chain variable region has at least 95% sequence identity to the amino acid sequence of SEQ ID NO:71; or h. the heavy chain variable region has at least 95% sequence identity to the amino acid sequence of SEQ ID NO: 80, and the light chain variable region has at least 95% sequence identity to the amino acid sequence of SEQ ID NO:81; or i. the heavy chain variable region has at least 95% sequence identity to the amino acid sequence of SEQ ID NO: 90, and the light chain variable region has at least 95% sequence identity to the amino acid sequence of SEQ ID NO:91; or j. the heavy chain variable region has at least 95% sequence identity to the amino acid sequence of SEQ ID NO: 100, and the light chain variable region has at least 95% sequence identity to the amino acid sequence of SEQ ID NO: 101. An antigen-binding protein or fully human anti-B7-H3 antibody, or an antigenbinding fragment thereof, comprising a heavy chain variable region and a light chain variable region, a. the heavy chain variable region having at least 95% sequence identity to the amino acid sequence of SEQ ID NO: 10, and the light chain variable region having at least 95% sequence identity to the amino acid sequence of SEQ ID NO:l l; or b. the heavy chain variable region having at least 95% sequence identity to the amino acid sequence of SEQ ID NO:20, and the light chain variable region having at least 95% sequence identity to the amino acid sequence of SEQ ID NO:21; or c. the heavy chain variable region having at least 95% sequence identity to the amino acid sequence of SEQ ID NO:30, and the light chain variable region having at least 95% sequence identity to the amino acid sequence of SEQ ID NO:31; or d. the heavy chain variable region having at least 95% sequence identity to the amino acid sequence of SEQ ID NO:40, and the light chain variable region having at least 95% sequence identity to the amino acid sequence of SEQ ID NO:41; or e. the heavy chain variable region having at least 95% sequence identity to the amino acid sequence of SEQ ID NO:50, and the light chain variable region having at least 95% sequence identity to the amino acid sequence of SEQ ID NO:51; or f. the heavy chain variable region having at least 95% sequence identity to the amino acid sequence of SEQ ID NO: 60, and the light chain variable region having at least 95% sequence identity to the amino acid sequence of SEQ ID NO:61; or g. the heavy chain variable region having at least 95% sequence identity to the amino acid sequence of SEQ ID NO:70, and the light chain variable region having at least 95% sequence identity to the amino acid sequence of SEQ ID NO:71; or h. the heavy chain variable region having at least 95% sequence identity to the amino acid sequence of SEQ ID NO: 80, and the light chain variable region having at least 95% sequence identity to the amino acid sequence of SEQ ID NO:81; or i. the heavy chain variable region having at least 95% sequence identity to the amino acid sequence of SEQ ID NO: 90, and the light chain variable region having at least 95% sequence identity to the amino acid sequence of SEQ ID NO:91; or j. the heavy chain variable region having at least 95% sequence identity to the amino acid sequence of SEQ ID NO: 100, and the light chain variable region having at least 95% sequence identity to the amino acid sequence of SEQ ID NO:101. An antigen-binding protein or fully human anti-B7-H3 antibody, or an antigenbinding fragment thereof, comprising: a. a heavy chain variable region and a light chain variable region, wherein the heavy chain variable region and the light chain variable region comprise the amino acid sequences of SEQ ID NOS: 10 and 11, respectively; or b. a heavy chain variable region and a light chain variable region, wherein the heavy chain variable region and the light chain variable region comprise the amino acid sequences of SEQ ID NOS:20 and 21, respectively; or c. a heavy chain variable region and a light chain variable region, wherein the heavy chain variable region and the light chain variable region comprise the amino acid sequences of SEQ ID NOS:30 and 31, respectively; or d. a heavy chain variable region and a light chain variable region, wherein the heavy chain variable region and the light chain variable region comprise the amino acid sequences of SEQ ID NOS:40 and 41, respectively; or e. a heavy chain variable region and a light chain variable region, wherein the heavy chain variable region and the light chain variable region comprise the amino acid sequences of SEQ ID NOS:50 and 51, respectively; or f. a heavy chain variable region and a light chain variable region, wherein the heavy chain variable region and the light chain variable region comprise the amino acid sequences of SEQ ID NOS:60 and 61, respectively; or g. a heavy chain variable region and a light chain variable region, wherein the heavy chain variable region and the light chain variable region comprise the amino acid sequences of SEQ ID NOS:70 and 71, respectively; or h. a heavy chain variable region and a light chain variable region, wherein the heavy chain variable region and the light chain variable region comprise the amino acid sequences of SEQ ID NOS:80 and 81, respectively; or i. a heavy chain variable region and a light chain variable region, wherein the heavy chain variable region and the light chain variable region comprise the amino acid sequences of SEQ ID NOS:90 and 91, respectively; or j. a heavy chain variable region and a light chain variable region, wherein the heavy chain variable region and the light chain variable region comprise the amino acid sequences of SEQ ID NOS: 100 and 101, respectively. The antigen-binding protein, antibody or antigen-binding fragment thereof of any one of claims 1-4, wherein the heavy chain CDR1 has the amino acid sequence of SEQ ID NO: 12, the heavy chain CDR2 has the amino acid sequence of SEQ ID NO: 13, the heavy chain CDR3 has the amino acid sequence of SEQ ID NO: 14, the light chain CDR1 has the amino acid sequence of SEQ ID NO: 15, the light chain CDR2 has the amino acid sequence of SEQ ID NO: 16, and the light chain CDR3 has the amino acid sequence of SEQ ID NO: 17. The antigen-binding protein, antibody or antigen-binding fragment thereof of any one of claims 1-4, wherein the heavy chain variable region has at least 95% sequence identity to the amino acid sequence of SEQ ID NO: 10, and the light chain variable region has at least 95% sequence identity to the amino acid sequence of SEQ ID NO: 11. The antigen-binding protein, antibody or antigen-binding fragment thereof of any one of claims 1-4, wherein the heavy chain variable region and the light chain variable region comprise the amino acid sequences of SEQ ID NOS: 10 and 11, respectively. The antigen-binding fragment of any one of claims 1-7, comprising a Fab fragment. The antigen-binding fragment of any one of claims 1-7, comprising a single chain antibody, wherein the heavy chain variable domain and the light chain variable domain are joined together with a peptide linker. The antigen-binding protein, antibody or antigen-binding fragment thereof, of any one of the preceding claims, comprising an IgG antibody, optionally wherein the IgG antibody is an IgGl, IgG2, IgG3, or IgG4 class antibody. The antigen-binding protein, antibody or antigen-binding fragment thereof, of claim 10, wherein the IgG antibody is an IgGl or IgG4 class antibody. The antigen-binding protein, antibody or antigen-binding fragment thereof, of claim 11, wherein the IgGl antibody comprises a mutant Fc region. The antigen-binding protein, antibody or antigen-binding fragment thereof, of claim 12, wherein the mutant Fc region comprises one or more mutations selected from L234A and L235A. The antigen-binding protein, antibody or antigen-binding fragment thereof, of claim 13, wherein the mutant Fc region comprises the mutations L234A and L235A (LALA). The antigen-binding protein, antibody or antigen-binding fragment thereof, of any one of the preceding claims, wherein the antigen-binding protein, antibody, or the antigenbinding fragment thereof, binds human B7-H3 protein with a KD of 10’⁷ M or less. A pharmaceutical composition comprising the antigen-binding protein, antibody or antigen-binding fragment of any one of the preceding claims and a pharmaceutically acceptable excipient. A kit comprising the comprising the antigen-binding protein, antibody or antigenbinding fragment of any one of claims 1-15 and a pharmaceutically acceptable excipient. A nucleic acid that encodes a polypeptide comprising the heavy chain variable region of the antigen-binding protein, antibody or antigen-binding fragment of any one of claims 1-15. A nucleic acid that encodes a polypeptide comprising the light chain variable region of the antigen-binding protein, antibody or antigen-binding fragment of any one of claims 1-15. A nucleic acid that encodes (i) a first polypeptide comprising the heavy chain variable region of the antigen-binding protein, antibody or antigen-binding fragment of any one of claims 1-15, and (ii) a second polypeptide comprising the light chain variable region of the antigen-binding protein, antibody or antigen-binding fragment. A vector comprising the nucleic acid of claim 18. A vector comprising the nucleic acid of claim 19. A vector comprising the nucleic acid of claim 20. A host cell harboring the vector of claim 21. The host cell of claim 24, wherein the vector is an expression vector, and wherein the host cell expresses the polypeptide comprising the heavy chain variable region. A host cell harboring the vector of claim 22. The host cell of claim 26, wherein the vector is an expression vector, and wherein the host cell expresses the polypeptide comprising the light chain variable region. A host cell harboring a first vector comprising the vector of claim 21 and a second vector comprising the vector of claim 22. The host cell of claim 28, wherein the first vector is a first expression vector, wherein the second vector is a second expression vector, and wherein the host cell expresses the polypeptide comprising the heavy chain variable region and the polypeptide comprising the light chain variable region. A host cell harboring the vector of claim 23. The host cell of claim 30, wherein the vector is an expression vector, and wherein the host cell expresses the first and second polypeptides. A method for preparing a heavy chain variable region of an antigen-binding protein, antibody or antigen-binding fragment, the method comprising: culturing a population of the host cell of claim 25 under conditions suitable for expressing the heavy chain variable region of the antigen-binding protein, antibody or antigen-binding fragment. The method of claim 32, further comprising: recovering from the host cells the expressed heavy chain variable region of the antigen-binding protein, antibody or antigen-binding fragment. A method for preparing a polypeptide comprising a light chain variable region of an antigen-binding protein, antibody or antigen-binding fragment, the method comprising: culturing a population of the host cell of claim 27 under conditions suitable for expressing the polypeptide comprising the light chain variable region of the antigenbinding protein, antibody or antigen-binding fragment. The method of claim 34, further comprising: recovering from the host cells the expressed light chain variable region of the antigen-binding protein, antibody or antigen-binding fragment. A method for preparing (i) a first polypeptide comprising a heavy chain variable region of an antigen-binding protein, antibody or antigen-binding fragment, and (ii) a second polypeptide comprising a light chain variable region of an antigen-binding protein, antibody or antigen-binding fragment, the method comprising: culturing a population of the host cell of claim 29 under conditions suitable for expressing (i) the first polypeptide, and (ii) the second polypeptide. The method of claim 36, further comprising: recovering from the host cells (i) the expressed first polypeptide, and (ii) the expressed second polypeptide. A method for preparing (i) a first polypeptide comprising a heavy chain variable region of an antigen-binding protein, antibody or antigen-binding fragment, and (ii) a second polypeptide comprising a light chain variable region of an antigen-binding protein, antibody or antigen-binding fragment, the method comprising: culturing a population of the host cell of claim 31 under conditions suitable for expressing (i) the first polypeptide, and (ii) the second polypeptide. The method of claim 38, further comprising: recovering from the host cells (i) the expressed first polypeptide, and (ii) the expressed second polypeptide. A method for inhibiting growth or proliferation of B7-H3-expressing cells, comprising: contacting (i) a population of effector cells with (ii) a population of target cells which express B7-H3 (iii) in the presence of the antigen-binding protein, antibody or antigen-binding fragment thereof of any one of claims 1-15, under conditions that are suitable for inhibiting growth or proliferation of the B7-H3- expressing cells. The method of claim 40, wherein the population of effector cells comprises peripheral blood mononuclear cells (PBMCs) or natural killer (NK) cells. The method of claim 40 or 41, wherein the population of target cells comprise B7-H3 expressing human cancer cells or transgenic cells expressing B7-H3. The method of any one of claims 40-42, wherein the ratio of the effector cells to the target cells is 1-5:1, optionally wherein the ratio is 1:1, 2:1, 3:1, 4:1 or 5:1. The method of any one of claims 40-42, wherein the ratio of the effector cells to the target cells is 5-10:1, 10-20:1, or 20-30:1. A method for killing B7-H3-expressing cells, comprising: contacting (i) a population of effector cells with (ii) a population of target cells which express B7-H3 (iii) in the presence of the antigen-binding protein, antibody or antigen-binding fragment thereof of any one of claims 1-15, under conditions that are suitable for killing the B7-H3- expressing cells. The method of claim 45, wherein the population of effector cells comprises PBMCs or NK cells. The method of claim 45 or 46, wherein the population of target cells comprises B7- H3 expressing human cancer cells or transgenic cells expressing B7-H3. The method of any one of claims 45-47, wherein the ratio of the effector cells to the target cells is 1-5:1, optionally wherein the ratio is 1:1, 2:1, 3:1, 4:1 or 5:1. The method of any one of claims 45-47, wherein the ratio of the effector cells to the target cells is 5-10:1, 10-20:1, or 20-30:1. The method of any one of claims 40-49, wherein the population of target cells are in a subject and the antigen-binding protein, antibody, or antigen-binding fragment thereof is administered to the subject. The method of any one of claims 40-49, which is an in vitro method. A method for treating a subject having a disease associated with B7-H3 expression, the method comprising: administering to the subject an effective amount of a pharmaceutical composition comprising the antigen-binding protein, antibody or antigen-binding fragment of any one of claims 1-15. The method of claim 52, wherein the disease associated with B7-H3 expression is cancer. The method of claim 53, wherein cancer is carcinoma of the ovary, colon, prostate, skin, pancreas, kidney, urothelial, or lung cancer. The method of claim 53, wherein cancer is acute myeloid lymphoma (AML), nonHodgkin lymphoma (NHL), non-small cell lung cancer (NSCLC), small cell lung cancer, urothelial cell carcinoma, esophageal cancer, hepatocellular carcinoma, glioma, neuroblastoma, glioblastoma multiforme, blastoma, sarcoma, leukemia, lymphoid malignancies, pancreatic cancer, head and neck cancer, ovarian cancer, oral cancer, breast cancer, triple negative breast cancer (TNBC), lymphoma, renal cell carcinoma, clear cell renal cell carcinoma, colon cancer, colorectal cancer, melanoma, stomach cancer, lung cancer, liver cancer, bladder cancer, prostate cancer, anal cancer, endometrial cancer, vulvar cancer, squamous cell tumors, hypopharyngeal squamous cell carcinoma, or squamous cell carcinoma (e.g., squamous cell lung cancer or squamous cell head and neck cancer). The method of any one of claims 53-55, wherein the cancer is a metastatic cancer, refractory cancer, or recurrent cancer. The antigen-binding protein, antibody or antigen-binding fragment of any one of claims 1-15, for use in the method of any one of claims 40-56. Use of the antigen-binding protein, antibody or antigen-binding fragment of any one of claims 1 ■ 15 in the manufacture of a medicament for use in the method of any one of claims 40-56.