Antibodies directed to slamf6

Abstract

The present invention is directed to novel antibodies capable of specifically binding SLAMF6 and uses thereof in cancer immunotherapy.

Description

[0001] ANTIBODIES DIRECTED TO SLAMF6

[0002] FIELD OF THE INVENTION

[0003] The present invention relates generally to antibodies useful for therapy and diagnosis, and specifically to antibodies targeting SLAM Family Member 6 (SLAMF6).

[0004] BACKGROUND OF THE INVENTION

[0005] Researchers and physicians are constantly searching for the next innovative treatment to face cancer. Although there have been continuous improvements in survival and life expectancy in cancer patients over the years, there is still an unmet need for new, different, effective and safe components or compositions for treating terminal cancer patients without any therapeutic horizon. Monoclonal antibody-based immunotherapy has become an important modality in the treatment of cancer, alongside more traditional treatments such as surgery, radiation, and chemotherapy. Therapeutic antibodies are disclosed for example in Waldman., AD., et. al., Nat. Rev. Immunol, 2022, 20, 651 and in US 2021 / 0277123, US 2022 / 0332816, US 2021 / 206867, US 2019 / 0100588 and US 2019 / 0153471. One of the major problems with the use of monoclonal antibodies (mAbs) treatment is that cancer cells are constantly mutating which often leads to resistance or even complete lack of responsiveness to treatment.

[0006] Among the approaches used in the search for new immunomodulatory mechanisms relevant for cancer immunotherapy is to identify lymphocyte surface receptors that are likely to have a regulatory function. The clinical success of targeting the immunoglobulin superfamily receptors PD-1 and CTLA-4 fueled interest in the uncharacterized members of several structural Ig-like subfamilies.

[0007] The SLAM (signaling lymphocyte activation molecules) family of receptors is a group of type I transmembrane receptors that includes SLAMF1 (CD150; SLAM), SLAMF2 (CD48), SLAMF3 (Ly-9; CD229), SLAMF4 (CD244; 2B4), SLAMF5 (CD84), SLAMF6 (Lyl08; NTB- A; CD352), SLAMF7 (CRACC; CS1; CD319), SLAMF8 (BLAME; CD353), and SLAMF9 (CD84-H1; SF2001; CD2F10). All SFR except 2B4 and CD48 are homotypic binders, i.e. they engage a same ectodomain sequence, either in a cis (same cell) or trans (adjacent cell) configuration. Most cell types express 3-5 members of the SLAM family. SFR generate signals via a bi-phasic recruitment mechanism to tyrosines in their cytoplasmic domain, which are designated immunoreceptor tyrosine-based switch motifs (ITSMs). SLAMF6, also known as NTB-A and CD352, is one such homotypic SFR expressed on NK, T, and B lymphocytes and dendritic cells (DC). Previous publications established its role as an important modulator of T cell response. Engagement of SLAMF6 on human T cells can substitute the CD28 co- stimulatory pathway and induce polarization toward a Thl phenotype. However, CD4-positive T cells from Ly-108 knockout mice (the murine SLAMF6 ortholog) show impairment in IL-4 production, suggesting a role of SLAMF6 in Th2 polarization. Engagement of SLAMF6 on human NK cells stimulates cytotoxicity and proliferation, as well as interferon gamma (IFN-y) and tumor necrosis factor alpha (TNF-a) production.

[0008] A publication by the inventors and colleagues suggests a major role for SLAMF6 in lymphocyte co-modulation, showing that targeting SLAMF6 by its soluble ectodomain yields CD8+T cell with powerful anti-tumor reactivity that do not need interleukin-2 (IL-2) supplementation, neither in vitro nor in vivo, in a model of adoptive transfer of Pmel-1 T cells to melanoma bearing mice (Eisenberg et al., Cancer Immunol Res; 6(2) 2018). WO 2015 / 104711, to some of the present inventors, discloses the use of soluble NTB-A polypeptides or agonists thereof for the treatment of cancer patients, for preventing and treating cytopenia in susceptible patients, and for the ex vivo preparation of improved T cell compositions for adoptive cell therapy.

[0009] WO 2019 / 155474, to some of the present inventors, relates to improved therapeutic modalities for cancer immunotherapy involving specifically modulating the expression and / or activity of SLAMF6 splice variants. WO '474 discloses inter alia compositions and methods for cancer therapy, including adoptive T cell transfer therapies, cell vaccines and / or polypeptide-based medicaments. The publication further discloses compositions and methods providing selective augmentation of SLAMF6 variant 3 (SLAMF6var3) expression or activity on T cells and / or tumor cells.

[0010] WO 2020 / 261265, to some of the present inventors, relates to nucleic acid agents modulating the expression of SLAMF6 isoforms, compositions comprising same and methods for their use in immunomodulation. Specifically, provided are splice-switching oligonucleotides and constructs useful in cancer immunotherapy. Another publication to some of the present inventors, namely Hajaj et al., 2021 (Cancer Immunol Res. 9(6):637-650) further evaluates SLAMF6- specific splice-switching antisense oligonucleotides, and reports that alternative splicing of SLAMF6 generates a dominant positive form, boosting T-cell effector functions.

[0011] WO 2020 / 261266, to some of the present inventors, relates to cancer management, specifically to therapeutic combinations and methods for immunotherapy of tumors and malignancies, in particular employing the use of a SLAMF6-mediated T cell activator in combination with a LAG3 inhibitor. Antibodies directed to SLAMF6 have been developed for various purposes. Some of these antibodies have been evaluated for their therapeutic potential in cancer therapy, either directly (by assessing their ability to modulate the activity of SLAMF6-expressing cells) or indirectly (as antibody-toxin conjugates and / or by assessing their ability to induce antibody-dependent cellular cytotoxicity (ADCC) against SLAMF6-expressing tumors).

[0012] For example, US 2019 / 0375841 to Seattle Genetics relates to antibodies, including antibody drug conjugates, that specifically bind to SLAMF6, and to methods for using the antibodies to detect or modulate activity of (e.g., inhibit proliferation of) an SLAMF6-expressing cell, as well as for diagnoses or treatment of diseases or disorders (e.g., cancer) associated with SLAMF6-expressing cells. Further disclosed therein is a method of treating multiple myeloma using an anti-SLAMF6 antibody drug conjugate. The activity of the disclosed antibodies was determined in the form of antibody-drug conjugates, with no direct activity or effect on tumor cells not expressing SLAMF6 being demonstrated.

[0013] Additional antibodies against SLAMF6 are described, for example, by Korver et al. (British Journal of Haematology 2007, 137, pp. 307-318). These antibodies exerted cytotoxic effects on SLAMF6 expressing lymphocytes, and had no effect on T cell proliferation or cytokine secretion.

[0014] Antibodies directed to SLAMF6 are also used or referred to in US 2009 / 017014 to Valdez et al. Valdez et al (J Biol Chem 2004, 279(18), pp. 18662-18669) teach that SLAMF6 activates T cells by homotypic interactions, and, using a mixture of mAbs against human SLAMF6 in CD4+T cells, disclose improved IFNy secretion in naive T cells, but not in memory cells.

[0015] WO 2021 / 001653 to Oxford Bio therapeutics relates to antibodies and other therapeutic proteins directed against SLAMF6, nucleic acids encoding them, methods for preparing antibodies and other therapeutic proteins, and methods for the treatment of diseases, such as cancers, by using antibodies and other therapeutic proteins directed against SLAMF6. Among the antibody clones disclosed therein is the 1B3 clone, described as having the ability to enhance T cell proliferation and cytokine secretion induced by anti-CD3 antibodies, and postulated to bind to the homodimerization epitope of SLAMF6.

[0016] US 2017 / 0334989 to ARCA Biopharma is directed to anti-SLAMF6 antibodies and antigen-binding fragments thereof, to pharmaceutical compositions comprising same, and to methods of their use to bind SLAMF6 and treat diseases, such as hematologic malignancies characterized by expression of SLAMF6. The publication discloses that the antibodies had no effect on T cell proliferation and cytokine secretion, either alone or in combination with anti-CD3 antibodies, suggesting that they target a non- activating epitope of SLAMF6. Rather, the publication suggests that the antibodies may affect tumor cells indirectly via complementdependent cytotoxicity (CDC) and / or ADCC, and may accordingly be used in treating SLAMF6- expressing tumors. Additional anti-SLAMF6 antibodies that may be used for inducing ADCC are described in WO2024240896.

[0017] Yigit et al., 2016 (Oncotarget 7 (18): 26346-60) discloses that combination of an anti- SLAMF6 antibody and ibrutinib efficiently abrogates expansion of chronic lymphocytic leukemia cells. Yigit et al., 2019 (Cancer Immunol Res 7:1485-96) suggests a role for SLAMF6 as a regulator of exhausted CD8+T cells in cancer. More specifically, the publications evaluate the effects of the anti-human SLAMF6 antibody clones 994.1 (ARCA Biopharma) and NT-7 (Biolegend), respectively, on various functions related to their ability to mediate ADCC against SLAMF6-expressing tumors.

[0018] The activity of the NT-7 antibody was further characterized under additional experimental settings. For example, Dragovich et al. 2019 (PLoS ONE 14(6): e0218109) explores the role of SLAMF6 clustering in T cell activation. The authors report that primary human T cells and T cell lines incubated with a combination of plate-bound antibodies against CD3 and SLAMF6 (NT-7) responded in improved proliferation and cytokine secretion compared to equivalent cells treated with the anti-CD3 antibody alone, and identify SLAMF6 as a stimulatory T cell co-receptor. A subsequent publication authored by some of these researchers (Gartshteyn et al., 2022, Life Sci Alliance 8;6(2):e202201533) discloses that T cell activity is enhanced when SLAMF6 colocalizes with the CD3 complex. In particular, the publication discloses that co-localization of the anti-CD3 antibody and the anti-SLAMF6 antibody, by conjugation to the same beads or by administration as bispecific antibodies, enhanced T cell activation to a greater extent than to each antibody alone or in combination, while physical separation between the antibodies (for example, conjugation to discrete beads) impaired their activation.

[0019] While the ability to induce ADCC or CDC and to mediate drug-induced cytotoxicity may be desirable as means for treating SLAMF6-expressing tumors, many tumors and in particular solid tumors do not express SLAMF6. In addition, such approaches may even be harmful to non- malignant immune cells that express SLAMF6 naturally, thereby impairing anti-tumor immunity in the treated patient.

[0020] There remains an unmet medical need for additional effective and safe therapeutic modalities for cancer. The development of therapeutic SLAMF6-specific antibodies, and in particular of mAbs capable of enhancing anti-tumor immunity in a specific and predictable manner, would be advantageous for the development of improved immunotherapy regimes. SUMMARY OF THE INVENTION

[0021] According to embodiments of the present invention, antibodies directed to SLAMF6 are provided. In particular, disclosed are anti-SLAMF6 antibodies having improved characteristics, and molecules comprising at least an antigen-binding fragment thereof, that are particularly useful for therapeutic applications. The invention in embodiments thereof further provides nucleic acid sequences encoding the antibodies, methods for producing the antibodies and molecules, and methods of using same in cancer immunotherapy.

[0022] The invention is based, in part, on the development of unexpectedly improved anti-human SLAMF6 (hSLAMF6) antibodies, characterized by exceptional functional properties. In particular, disclosed herein is the development of several antibody clones, including chimeric and humanized antibodies, which selectively bind to hSLAMF6 under physiologically relevant conditions. Surprisingly, the antibodies were remarkably effective in inducing or enhancing antitumor immunity, and exhibited functional superiority over known SLAMF6-specific antibodies in enhancing T cell cytotoxicity. In particular, antibodies produced in accordance with the invention were capable of increasing tumor-induced direct cytotoxicity by primary human lymphocytes directly, in a manner that does not require binding to Fc receptors (FcR) and is independent from induction of drug-induced toxicity, antibody-dependent cellular cytotoxicity (ADCC) and / or complement-dependent cytotoxicity (CDC).

[0023] According to embodiments of the invention, provided are antibodies specific to hSLAMF6, and molecules comprising at least an antigen-binding fragment thereof. These antibodies and molecules, collectively referred to herein as the antibodies of the invention, are characterized by structural and functional properties as described hereinbelow. In one embodiment, the antibody is a monoclonal antibody (mAb, e.g. a murine anti- hSLAMF6 mAb). In another embodiment the antibody is a chimeric antibody. In another embodiment the antibody is a humanized antibody.

[0024] In some embodiments, an antibody of the invention is characterized in that it induces or enhances direct cell-mediated cytotoxicity by primary human lymphocytes (that does not require FcR binding and induction of drug-induced toxicity, ADCC or CDC). In another embodiment, the lymphocytes are tumor- specific lymphocytes. In another embodiment, the antibody induces or enhances tumor-induced Granzyme B secretion from said lymphocytes. In another embodiment, said antibody induces or enhances said direct cell-mediated cytotoxicity without substantially inducing or enhancing drug-induced toxicity, ADCC and CDC.

[0025] In one aspect, there is provided an antibody specific to hSLAMF6, or a molecule comprising at least an antigen-binding fragment thereof, wherein: a) the antibody or molecule comprises a set of a heavy chain variable region (VH) and a light chain variable region (VL) as follows:

[0026] EVQLVQSGAEVKKPGS SVKVSCKASGYTFTDYYMNWVKQRPGQGLEWI GD INPNGGD S SYNQKF KGKVTLTADKS T S TAYMELS SLRSEDTAVYYCASFTTVDYWGQGTTVTVS S (VH, SEQ ID NO: 137), and

[0027] DVVMTQSPLSLPVTLGQPAS I SCKS SQSLLD SYGKTYLNWLQQRPGQSPRRL I YLVSKLD SGVP DRF SGSGSGTDFTLKI SRVEAEDVGVYYCWQGTHFPQTFGGGTKVE IK (VL, SEQ ID NO: 139), b) the antibody or molecule comprises VH and VL sequences having at least 90%, 95%, 98% or 99% identity to the VH and VL sequences of a), or c) the antibody or molecule comprises a set of six complementarity determining regions (CDRs) as follows: DYYMN (SEQ ID NO: 7), D INPNGGD S SYNQKFKG (SEQ ID NO: 79), FTTVDY (SEQ ID NO: 13), KS SQSLLD SYGKTYLN (SEQ ID NO: 33), LVSKLD S (SEQ ID NO: 11), and WQGTHFPQT (SEQ ID NO: 15), or comprises up to 3 amino acid modifications in each CDR.

[0028] Each possibility represents a separate embodiment of the invention. In one embodiment, the antibody or molecule comprises a set of six CDRs selected from the group consisting of: a. SEQ ID NOs: 7, 79, 13, 33, 11 and 15, b. GYTFTDYYMN (SEQ ID NO: 47) and SEQ ID NOs: 79, 13, 33, 11 and 15, and c. GYTFTDY (SEQ ID NO: 148) and SEQ ID NOs: 79, 13, 33, 11 and 15.

[0029] Each possibility represents a separate embodiment of the invention.

[0030] In another embodiment, the antibody or molecule comprises the VH and VL sequences of SEQ ID NOs: 137 and 139. In another embodiment, the antibody or molecule comprises VH and VL sequences having at least 90%, 95%, 98% or 99% identity to the VH and VL sequences of SEQ ID NOs: 137 and 139, with the proviso that the leucine at position 41 of SEQ ID NO: 139 is retained.

[0031] In another embodiment, the antibody or molecule is a monoclonal antibody. In another embodiment the antibody comprises a human or humanized constant (Fc) region of the IgGl or IgG4 isotype. In another embodiment said Fc region is an engineered human IgGl or IgG4 that does not substantially bind to Fey receptors. In another embodiment said antibody or molecule binds to a SLAMF6 polypeptide having the amino acid sequence as set forth in SEQ ID NO: 130 with an equilibrium dissociation constant (KD) of LOlx10-7M to 4.85x10-10M, wherein each possibility represents a separate embodiment of the invention.

[0032] In another embodiment there is provided a nucleic acid construct encoding the antibody or molecule. According to an exemplary embodiment, the nucleic acid construct comprises - a nucleic acid sequence as set forth in SEQ ID NO: 143 or 145, or has at least 90%, 95%, 98% or 99% identity thereto. In another embodiment said nucleic acid construct comprises at least one nucleic acid sequence as described herein (e.g. SEQ ID NO: 143 or 145, or at least 90%, 95%, 98% or 99% identical thereto). In another embodiment the invention provides a host cell comprising at least one nucleic acid construct as described herein.

[0033] In another aspect there is provided a pharmaceutical composition comprising a therapeutically effective amount of at least one such antibody or molecule, and a pharmaceutical excipient. In another embodiment the pharmaceutical composition is formulated for injection and comprises an arginine-succinate buffer, trehalose, and at least one surfactant. In another embodiment the pharmaceutical composition is for use in therapy.

[0034] In another embodiment the pharmaceutical composition is for use in treating cancer in a subject in need thereof, the subject is afflicted with a solid tumor. In another embodiment the tumor is selected from the group consisting of melanoma, renal cell carcinoma, lung carcinoma, breast carcinoma, and head and neck carcinoma, wherein each possibility represents a separate embodiment of the invention. In another embodiment said antibody or molecule is an antibody comprising a human or humanized Fc region of the IgG4 isotype optionally engineered to substantially eliminate binding to Fey receptors, or a human or humanized Fc region of the IgGl isotype engineered to substantially eliminate binding to Fey receptors. In another embodiment the use does not substantially include induction of drug-induced toxicity, ADCC and / or CDC. In another embodiment said treatment or use does not substantially include induction of any one of drug-induced toxicity, ADCC and CDC. In yet another embodiment, the subject is afflicted with a hematopoietic malignancy.

[0035] In another aspect there is provided a method of treating cancer in a subject in need thereof, comprising administering to the subject the pharmaceutical composition. In another embodiment the subject is afflicted with a solid tumor. In another embodiment the tumor is selected from the group consisting of melanoma, renal cell carcinoma, lung carcinoma, breast carcinoma, and head and neck carcinoma. In another embodiment said antibody or molecule is an antibody comprising a human or humanized Fc region of the IgG4 isotype optionally engineered to substantially eliminate binding to Fey receptors, or a human or humanized Fc region of the IgGl isotype engineered to substantially eliminate binding to Fey receptors. In another embodiment the treatment does not substantially include induction of drug-induced toxicity, ADCC and / or CDC. In another embodiment said treatment or use does not substantially include induction of any one of drug-induced toxicity, ADCC and CDC. In yet another embodiment, the subject is afflicted with a hematopoietic malignancy. In another aspect, the invention provides a method for detecting or quantifying the presence of SLAMF6 in a sample, comprising the steps of:

[0036] (i) incubating the sample with the antibody or molecule, under conditions enabling the formation of an antigen-antibody complex; and

[0037] (ii) detecting or quantifying the antigen-antibody complex.

[0038] In another embodiment the antibody comprises a set of a heavy chain variable region (VH) and a light chain variable region (VL) of an antibody disclosed herein, e.g. an antibody listed in Table 28 below. In another embodiment said antibody comprises VH and VL sequences having at least 90%, 95%, 98% or 99% identity to the VH and VL sequences of an antibody listed in Table 28. In another embodiment said antibody is a chimeric or humanized form of the antibody listed in Table 28. For instance, exemplary chimeric and humanized antibodies in accordance with the invention are listed in Table 27 and further described in the Examples. In another embodiment, said antibody or molecule is characterized by complementarity determining regions (CDRs) as disclosed herein. For example, the antibody may comprise a set of six CDRs as set forth in one of Tables 1-26 below, and having 0, 1, 2 or 3 amino acid modifications in each CDR. In another embodiment said antibody comprises VH and VL sequences having at least 90%, 95%, 98% or 99% identity to the VH and VL sequences of an antibody listed in Table 28 wherein the CDR sequences of said antibody are retained. In another embodiment, there is provided an antibody, or a molecule comprising at least an antigen binding fragment thereof, which binds to an epitope on hSLAMF6 recognized by an antibody of the invention, or which cross-competes for hSLAMF6 binding with an antibody of the invention.

[0039] In another embodiment, said antibody or molecule comprises a set of six CDRs as set forth in one of Tables 1-26, optionally comprising up to 3 amino acid modifications in each CDR. In another embodiment, there is provided an antibody, or a molecule comprising at least an antigen-binding fragment thereof, which comprises a set of six CDRs as set forth in one of Tables 1-26, or which binds to an epitope on hSLAMF6 recognized by an antibody comprising a set of six CDRs as set forth in one of Tables 1-26, or which cross-competes for hSLAMF6 binding with an antibody comprising a set of six CDRs as set forth in one of Tables 1-26.

[0040] Thus, in one aspect, there is provided an antibody specific to hSLAMF6, or a molecule comprising at least an antigen-binding fragment thereof, wherein: a) The antibody comprises a set of a heavy chain variable region (VH) and a light chain variable region (VL) of an antibody listed in Table 28, b) said antibody comprises VH and VL sequences having at least 90%, 95%, 98% or 99% identity to the VH and VL sequences of a), c) said antibody is a chimeric or humanized form of the antibody of a) or b), or d) said antibody or molecule comprises a set of six CDRs as set forth in one of Tables 1-26, and comprising up to 3 amino acid modifications in each CDR.

[0041] In another embodiment the antibody or molecule comprises a set of six CDRs as set forth in one of Tables 1-26. In another embodiment the antibody or molecule comprises a set of six CDRs of an antibody selected from the group consisting of: a) Ab07, comprising the three VH CDR sequences and the three VL CDR sequences as set forth in Table 7, b) Ab 19, comprising the three VH CDR sequences and the three VL CDR sequences as set forth in Table 17, c) Ab04, comprising the three VH CDR sequences and the three VL CDR sequences as set forth in Table 4, and d) Ab02, comprising the three VH CDR sequences and the three VL CDR sequences as set forth in Table 2, or wherein said antibody or molecule comprises a set of six CDRs having 0, 1, 2 or 3 amino acid modifications in total compared to the antibody of a) to d).

[0042] In another embodiment the antibody or molecule comprises VH and VL sequences selected from the group consisting of: a) SEQ ID NOs: 87 and 88, corresponding to VH and VL sequences of Ab02, respectively, b) SEQ ID NOs: 91 and 92, corresponding to VH and VL sequences of Ab04, respectively, c) SEQ ID NOs: 97 and 98, corresponding to VH and VL sequences of Ab07, respectively, and d) SEQ ID NOs: 116 and 117, corresponding to VH and VL sequences of Abl9, respectively.

[0043] In another embodiment the antibody or molecule is cross-reactive with cynomolgus monkey SLAMF6 (cynoSLAMF6). For example, said antibody or molecule may comprises a set of six CDRs of an antibody selected from the group consisting of: a) Ab 19, comprising the three VH CDR sequences and the three VL CDR sequences as set forth in Table 17, and b) Ab04, comprising the three VH CDR sequences and the three VL CDR sequences as set forth in Table 4, or may comprise a set of six CDRs having 0, 1, 2 or 3 amino acid modifications in total compared to the antibody of a) or b).

[0044] In another embodiment the antibody or molecule is a chimeric or humanized antibody. For example, said antibody or molecule may comprise a set of six CDRs of an antibody selected from the group consisting of: a) Ab07, comprising the three VH CDR sequences and the three VL CDR sequences as set forth in Table 7, b) Ab07 VH(NG_ GG), comprising the three VH CDR sequences and the three VL CDR sequences set forth in Table 21, c) Ab07 VH(NG_SG), comprising the three VH CDR sequences and the three VL CDR sequences set forth in Table 22, d) Ab07 VH(NG. _NA), comprising the three VH CDR sequences and the three VL CDR sequences set forth in Table 23, e) Ab 19, comprising the three VH CDR sequences and the three VL CDR sequences set forth in Table 17, f) Ab 19 VL(DG_SG), comprising the three VH CDR sequences and the three VL CDR sequences set forth in Table 24, g) Ab 19 VL(DG_DA), comprising the three VH CDR sequences and the three VL CDR sequences set forth in Table 25, and h) Ab 19 VL(DG_GG), comprising the three VH CDR sequences and the three VL CDR sequences set forth in Table 26.

[0045] In another embodiment the antibody or molecule comprises a set of VH and VL regions of an antibody listed in Table 27. In a particular embodiment, said antibody is selected from the group consisting of Hu007-05 (BM1), Hu007-09 (BM2), Hu007-06 (BM3), Hu007-10 (BM4), Hu007-07 (BM5), Hu007-l l (BM6), Hu007-08 (BM7), and Hu007-12 (BM8) as presented in Table 27. In another particular embodiment, said antibody is selected from the group consisting of Hu007-05 (BM1), Hu007-08 (BM7), Hu007-09 (BM2) and Hu007-12 (BM8). In another embodiment said antibody comprises VH and VL sequences having at least 90%, 95%, 98% or 99% identity to the VH and VL sequences of an antibody as disclosed herein, e.g. Ab07- VH(NG_GG), with the proviso that the leucine at position 41 is retained. Each possibility represents a separate embodiment of the invention. In a particular embodiment said antibody is Hu007-08 (BM7).

[0046] In another embodiment, chimeric or humanized antibodies of the invention may comprise a human or humanized constant (Fc) region of the IgGl or IgG4 isotype. In another embodiment said Fc region is an engineered human IgGl or IgG4 that does not substantially bind to Fey receptors. In a particular embodiment said Fc region is an engineered human IgGl comprising a LALA mutation. In certain other exemplary embodiments, the CDRs are grafted into suitable human variable chains, including, but not limited to IGHV1-69*O2 and / or IGKV2-30*01.

[0047] In another embodiment, the chimeric or humanized antibody comprises a VH as set forth in SEQ ID NO: 137 and a VL as set forth in SEQ ID NO: 139. In another embodiment, the chimeric or humanized antibody comprises VH and VL sequences having at least 90%, 95%, 98% or 99% identity to the VH and VL sequences of SEQ ID NOs: 137 and 139, respectively. In another embodiment the chimeric or humanized antibody comprises VH and VL sequences having at least 90%, 95%, 98% or 99% identity to the VH and VL sequences of SEQ ID NOs: 137 and 139, with the proviso that the leucine at position 41 of SEQ ID NO: 139 is retained. Each possibility represents a separate embodiment of the invention. In a particular embodiment said antibody is a humanized antibody comprising a VH as set forth in SEQ ID NO: 144 and a VL as set forth in SEQ ID NO: 146. In another embodiment said antibody is a humanized antibody having at least 95%, 98% or 99% identity to the VH as set forth in SEQ ID NO: 144 and the VL as set forth in SEQ ID NO: 146. In another embodiment said chimeric or humanized antibody comprises a constant region as set forth in SEQ ID NO: 141 and / or 142.

[0048] In another embodiment, the chimeric or humanized antibody comprises a set of six CDRs as set forth in SEQ ID NOs: 7, 79, 13, 33, 11 and 15, a set of six CDRs as set forth in SEQ ID NOs: 147, 79, 13, 33, 11 and 15, or a set of six CDRs as set forth in SEQ ID NOs: 148, 79, 13, 33, 11 and 15, wherein each possibility represents a separate embodiment of the invention. In another embodiment, the chimeric or humanized antibody comprises a set of six CDRs selected from the group consisting of SEQ ID NOs: 7, 147, 148, 79, 13, 33, 11 and 15, optionally comprising up to 3 amino acid modifications in each CDR. In some embodiments, said chimeric or humanized antibody may have 1, 2 or 3 amino acid modifications in one or more of SEQ ID NOs: 7, 147, 148, 79, 13, 33, 11 and 15, wherein each possibility represents a separate embodiment of the invention. In other embodiments, said chimeric or humanized antibody comprises 1, 2 or 3 amino acid substitutions in one, two or three of SEQ ID NOs: 7, 147, 148, 79, 13, 33, 11 and 15, wherein each possibility represents a separate embodiment of the invention.

[0049] In another embodiment, the antibody or molecule binds to a SLAMF6 polypeptide having the amino acid sequence as set forth in SEQ ID NO: 130 with an equilibrium dissociation constant (KD) of LOlx10-07M to 4.85x10-10M. Yet in certain advantageous embodiments, provided are antibodies characterized by exceptional anti-tumor activity while exhibiting moderate binding affinity to hSLAMF6. In a particular embodiment, the antibody or molecule binds to a SLAMF6 polypeptide having the amino acid sequence as set forth in SEQ ID NO: 130 with a KD of 9x10'08M to Ix10-9M.

[0050] In another aspect, there is provided a nucleic acid construct (or molecule) encoding an antibody of the invention. In another aspect there is provided a host cell comprising at least one nucleic acid construct (or molecule) encoding an antibody of the invention.

[0051] In another aspect the invention provides a pharmaceutical composition comprising a therapeutically effective amount of at least one antibody or molecule according to the invention. In another aspect there is provided a kit comprising at least one antibody or molecule according to the invention.

[0052] In another embodiment, the pharmaceutical composition comprises an antibody comprising a set of six CDRs of an antibody selected from the group consisting of: a) Ab07, comprising the three VH CDR sequences and the three VL CDR sequences as set forth in Table 7, b) Ab 19, comprising the three VH CDR sequences and the three VL CDR sequences as set forth in Table 17, c) Ab04, comprising the three VH CDR sequences and the three VL CDR sequences as set forth in Table 4, and d) Ab02, comprising the three VH CDR sequences and the three VL CDR sequences as set forth in Table 2, or e) a set of six CDRs having 0, 1, 2 or 3 amino acid modifications in total compared to the antibody of a)-d).

[0053] In another embodiment the antibody is a chimeric or humanized antibody. In another embodiment said antibody comprises a set of six CDRs of an antibody selected from the group consisting of: a) Ab07, comprising the three VH CDR sequences and the three VL CDR sequences as set forth in Table 7, b) Ab07 VH(NG_ GG), comprising the three VH CDR sequences and the three VL CDR sequences set forth in Table 21, c) Ab07 VH(NG_ SG), comprising the three VH CDR sequences and the three VL CDR sequences set forth in Table 22, d) Ab07 VH(NG. NA), comprising the three VH CDR sequences and the three VL CDR sequences set forth in Table 23, e) Ab 19, comprising the three VH CDR sequent and the three VL CDR sequences as set forth in Table 17, f) Ab 19 VL(DG_SG), comprising the three VH CDR sequences and the three VL CDR sequences set forth in Table 24, g) Ab 19 VL(DG_DA), comprising the three VH CDR sequences and the three VL CDR sequences set forth in Table 25, and h) Ab 19 VL(DG_GG), comprising the three VH CDR sequences and the three VL CDR sequences set forth in Table 26.

[0054] In another embodiment said antibody comprises a human or humanized Fc region of the IgGl or IgG4 isotype, optionally engineered to substantially eliminate binding to Fey receptors. In another embodiment said antibody is selected from the group consisting of Hu007-05 (BM1), Hu007-09 (BM2), Hu007-06 (BM3) Hu007-10 (BM4), Hu007-07 (BM5), Hu007-l l (BM6), Hu007-08 (BM7), and Hu007-12 (BM8) as presented in Table 27. In another embodiment said antibody is selected from the group consisting of Hu007-05 (BM1), Hu007-08 (BM7), Hu007-09 (BM2) and Hu007-12 (BM8). In a particular embodiment said antibody is Hu007-08 (BM7).

[0055] In another aspect, pharmaceutical compositions in accordance with the invention are for use in therapy. In another embodiment the pharmaceutical composition is for use in treating cancer in a subject in need thereof. In another aspect there is provided a method of treating cancer in a subject in need thereof, comprising administering to the subject a pharmaceutical composition of the invention.

[0056] In another embodiment of the methods and pharmaceutical compositions for use of the invention, the subject is afflicted with a solid tumor. In another embodiment the tumor is selected from the group consisting of melanoma, renal cell carcinoma, lung carcinoma, breast carcinoma, and head and neck carcinoma. In another embodiment (e.g. when the subject is afflicted with a solid tumor), said antibody or molecule is an antibody comprising a human or humanized Fc region of the IgG4 isotype optionally engineered to substantially eliminate binding to Fey receptors, or a human or humanized Fc region of the IgGl isotype engineered to substantially eliminate binding to Fey receptors. In another embodiment, the treatment or use does not substantially include induction of drug-induced toxicity, ADCC and / or CDC. In another embodiment said treatment or use does not substantially include induction of any one of drug- induced toxicity, ADCC and CDC. In another embodiment the subject is afflicted with a hematopoietic malignancy.

[0057] In another aspect the invention provides a method for detecting or quantifying the presence of SLAMF6 in a sample, comprising the steps of:

[0058] (i) incubating the sample with the antibody or molecule of the invention, under conditions enabling the formation of an antigen-antibody complex; and (ii) detecting or quantifying the antigen-antibody complex.

[0059] Other objects, features and advantages of the present invention will become clear from the following description and drawings.

[0060] BRIEF DESCRIPTION OF THE DRAWINGS

[0061] Figures 1A-1C depict test bleed results following mice immunization. Figure 1A - third test bleed (TB3) binding to the human SLAMF6 (hSLAMF6) ectodomain by ELISA. hSLAMF6 ectodomain protein SLAMF6-ECD-6 HIS was used for immunization of mice, and coated on plates at Ipg / ml. Binding (OD at 450nm) is shown as a function of antisera dilution of test bleeds obtained from individual immunized Balb / c mice (designated 13136 and 13137) and SJL (13138 and 13139). Figure IB - TB3 FACS test in hSLAMF6-expressing CH0K1 (1G3) cells. MFI - mean fluorescence intensity. Figure 1C - TB3 FACS test in CH0K1 (3A3) cells expressing recombinant cynomolgus monkey SLAMF6 (cynoSLAMF6). Controls included mlgGl, sheep anti-monkey SLAMF6 antibody ("ctrl Ab#3") and its isotype control (sheep IgG).

[0062] Figure 2. Jurkat cell binding of test antibodies. Jurkat cells were reacted with mouse anti- SLAMF6 antibodies and secondary antibody: Alexa Fluor® 488 goat anti-human IgG(H+L). mlgGl - murine isotype control. Mean fluorescence intensity (MFI) as a function of the concentration of the tested antibody in nanomolar (Abs. cone. (nM)) is shown.

[0063] Figure 3. CHOKl-cynoSLAMF6 binding for the determination of cross-species anti- SLAMF6 variants. Cells were labeled with mouse anti SLAMF6 antibodies (or isotype control) and secondary antibody: Alexa Fluor® 488 donkey anti-mouse IgG (H+L).

[0064] Figures 4A-4B. Anti-SLAMF6 antibodies enhance Granzyme B secretion in activated Jurkat T cells. Jurkat T cells were activated for 24h with plate-bound anti-CD3 in the presence of anti-SLAMF6 antibodies or isotype control antibodies (mlgGl) as listed in figures. Supernatants were collected and Granzyme B secretion was detected using ELISA. Figure 4A - tested antibody clones Ab01-Ab06, Ab09-Abl0, Abl5-Abl8. Figure 4B - tested antibody clones Ab02, Ab07- Ab08, Abl l-Abl4, Abl9-Ab22.

[0065] Figure 5A-5B. PBMCs from two healthy donors (presented in Figures 5A and 5B, respectively) were activated every two days for a total of three activations with plate-bound anti- CD3 and anti-SLAMF6 antibodies (or control antibodies). Cells were collected at day 7 (3 days after the last activation). Percent of CD107+ / CD8+expressing cells was detected using Flow cytometry. As controls, anti-hSLAMF6 antibodies Ctrl Ab#l (humanized anti-hSLAMF6) and its isotype control (hlgGl) and Ctrl Ab#2 (mouse-anti-hSLAMF6) were used, as well as antibodies against human PD-1 or LAG3, and the corresponding isotype controls. Student t test.

[0066] Figure 6A-6B. PBMCs from the two healthy donors described in Figures 5A and 5B, respectively, were activated every 2 days for a total of three activations with plate-bound anti- CD3 and anti-SLAMF6 antibodies (or control antibodies). Cell culture supernatants were collected at day 7 (3 days after the last activation). Granzyme B secretion was detected using ELISA. Control antibodies are as described in Figures 5A-5B. Student t test.

[0067] Figure 7A-7B. Anti mart-1 melanoma antigen- specific tumor infiltrating lymphocytes (TIL) extracted from two melanoma patient tumors (Figure 7A - TIL 412, Figure 7B - TIL 431) were activated with plate-bound anti-CD3 and anti-SLAMF6 for 48h as depicted in the graph. Cells collected and co-cultured (1 to 1 ratio) for additional 24h with 624 melanoma tumor cells. Supernatants were collected and Granzyme B secretion was detected using ELISA. Control antibodies are as described in Figures 5A-5B. Student t test.

[0068] Figure 8. GplOO melanoma antigen- specific TIL extracted from melanoma patient tumor (TIL209) were activated with plate-bound anti CD3 and anti-SLAMF6 antibodies (or control antibodies) for 48h as depicted in the graph. Cells collected and co-cultured (1 to 1 ratio) for additional 1.5h with DDAO-SE cell trace labeled 624 melanoma tumor cells. Percent Cleaved caspase 3+624 cells was detected using Flow cytometry. Control antibodies are as described in Figures 5A-5B, and further included a test group activated with anti-CD3 and anti-CD28 antibodies as a positive control. Student t test.

[0069] Figure 9. Jurkat cell binding of chimeric antibodies. Jurkat cells were labeled with chimeric anti SLAMF6 antibodies and secondary antibody: Alexa Fluor® 488 goat anti-human IgG(H+L). "ctrl Ab# l_IgGl" is Ctrl Ab#l as described above, and "ctrl Ab# l_IgG4" has the same specificity as Ctrl Ab#l, with the Fc isotype switched to IgG4.

[0070] Figure 10. CHOKl-cyno SLAMF6 binding of chimeric antibodies. Cells were labeled with chimeric anti SLAMF6 antibodies and secondary antibody.

[0071] Figure 11. chimeric anti-SLAMF6 antibodies enhance Granzyme B secretion in activated Jurkat T cells. Jurkat T cells were activated for 24h with plate-bound anti-CD3 and SLAMF6 antibodies (or control antibodies) at the concentrations listed in the figure. Supernatants were collected and Granzyme B secretion was detected using ELISA.

[0072] Figure 12. Jurkat FACS binding of chimeric anti-SLAMF6 antibodies designed with hotspot removal alternatives. Figure 13. depicts CHO-cyno SLAMF6 FACS binding of chimeric anti SLAMF6 antibodies designed with hotspot removal alternatives.

[0073] Figures 14A-14B. show the results of a functional assay of activation-induced Granzyme B secretion measured by ELISA. PBMCs from two healthy donors A and B (Figures 14A and 14B, respectively) were activated for 48 hours with plate-bound anti-CD3 (0.1 g / ml) and chimeric anti-SLAMF6 antibodies or control IgGl (2.5pg / ml). After 48 hours supernatants were collected for Granzyme B ELISA. "No t" indicates no activation.

[0074] Figure 15A-15C. PBMCs from a healthy donor were activated for 48 hours with platebound anti-CD3 (0.1 pg / ml) and chimeric anti-SLAMF6 antibodies or control IgGl (2.5pg / ml). After 48 hours supernatants were collected for ELISA and cells were collected for flow cytometry. Figure 15A - Granzyme B secretion by ELISA. Figure 15B - IFN-y secretion by ELISA. Figure 15C - percent of CD107+ / CD8+expressing cells.

[0075] Figures 16. humanized anti-SLAMF6 antibody enhances the generation of cytokines and cytotoxic mediators at early time points following activation with anti-CD3 antibodies. A summary of the percentile of CD 107, IFN-y and TNF-a positive CD8+cells obtained in two healthy donor PBMC is shown.

[0076] Figure 17. Jurkat FACS binding of humanized anti-SLAMF6 antibodies.

[0077] Figures 18A-18B. Humanized anti-SLAMF6 variants retain the capacity to enhance Granzyme B release in Jurkat T cells following activation with an anti-CD3 antibody. Figures 18A - secreted Granzyme B in pg / ml. Figure 18B - fold increase in Granzyme B secretion calculated as fold increase over average Granzyme B of Max Isotype IgG.

[0078] Figures 19A-19B. Humanized anti SLAMF6 variants retain the capacity to enhance granzyme B release form human PBMCs following activation with anti-CD3. The relative granzyme B secretion (fold over the levels secreted upon activation with anti-CD3 only), from PBMC obtained from two healthy human donors (Figures 19A and 19B, respectively) are presented.

[0079] Figures 20A-20B. Enhanced IFN-y release and CD 107 a degranulation in human PBMC following activation with anti CD3 and the humanized anti-SLAMF6 antibody Hu007-08. Figure 20A - IFN-y levels were measured by ELISA. Figure 20B - percentage of CD107a-CD8 positive cells was evaluated by flow cytometry.

[0080] Figures 21A-21C. Humanized Hu007-08 antibody stability. Hu007-08 was reconstituted in either PBS or in TT1 buffer and stored under different temperatures and relative humidity conditions: Figure 21A - storage at -20±5°C; Figure 21B - storage at 5±3°C; Figure 21C - storage at 25±5°C, 60%±5% relative humidity (RH). The results are presented as % of the monomer fraction over time.

[0081] Figure 22. Augmented cytotoxicity against LCL721.221 lymphoblastoid tumor cell line by NK cells when treated with humanized anti SLAMF6 antibody.

[0082] Figure 23. Augmented cytotoxicity against MDA-MB-231 breast tumor cells of anti-CD3 activated PBMCs when treated with humanized anti-SLAMF6 antibodies.

[0083] DETAILED DESCRIPTION OF THE INVENTION

[0084] According to embodiments of the present invention, antibodies that selectively bind to SLAMF6 are provided. In particular, provided are therapeutic antibodies directed to human SLAMF6 (hSLAMF6).

[0085] In one aspect, there is provided an antibody specific to hSLAMF6, or a molecule comprising at least an antigen-binding fragment thereof, wherein: a) the antibody or molecule comprises a set of a heavy chain variable region (VH) and a light chain variable region (VL) as follows:

[0086] EVQLVQSGAEVKKPGS SVKVSCKASGYTFTDYYMNWVKQRPGQGLEWI GD INPNGGD S SYNQKF KGKVTLTADKS T S TAYMELS SLRSEDTAVYYCASFTTVDYWGQGTTVTVS S (VH, SEQ ID NO: 137), and

[0087] DVVMTQSPLSLPVTLGQPAS I SCKS SQSLLD SYGKTYLNWLQQRPGQSPRRL I YLVSKLD SGVP DRF SGSGSGTDFTLKI SRVEAEDVGVYYCWQGTHFPQTFGGGTKVE IK (VL, SEQ ID NO: 139), b) the antibody or molecule comprises VH and VL sequences having at least 90%, 95%, 98% or 99% identity to the VH and VL sequences of a), or c) the antibody or molecule comprises a set of six complementarity determining regions (CDRs) as follows: DYYMN (SEQ ID NO: 7), D INPNGGD S SYNQKFKG (SEQ ID NO: 79), FTTVDY (SEQ ID NO: 13), KS SQSLLD SYGKTYLN (SEQ ID NO: 33), LVSKLD S (SEQ ID NO: 11), and WQGTHFPQT (SEQ ID NO: 15), or comprises up to 3 amino acid modifications in each CDR.

[0088] In one embodiment, the antibody or molecule comprises a set of six CDRs as set forth in SEQ ID NOs: 7, 79, 13, 33, 11 and 15. In another embodiment said antibody or molecule comprises a set of six CDRs as set forth in SEQ ID NOs: 147, 79, 13, 33, 11 and 15. In another embodiment said antibody or molecule comprises a set of six CDRs as set forth in SEQ ID NOs: 148, 79, 13, 33, 11 and 15. In another embodiment the antibody or molecule comprises the VH and VL sequences of SEQ ID NOs: 137 and 139. In another embodiment the antibody or molecule comprises VH and VL sequences having at least 90%, 95%, 98% or 99% identity to the VH and VL sequences of SEQ ID NOs: 137 and 139, with the proviso that the leucine at position 41 of SEQ ID NO: 139 is retained.

[0089] In another aspect, there is provided an antibody specific to hSLAMF6, or a molecule comprising at least an antigen-binding fragment thereof, wherein: a) the antibody comprises a set of a heavy chain variable region (VH) and a light chain variable region (VL) of an antibody listed in Table 28, b) said antibody comprises VH and VL sequences having at least 90%, 95%, 98% or 99% identity to the VH and VL sequences of a), c) said antibody is a chimeric or humanized form of the antibody of a) or b), and / or d) said antibody or molecule comprises a set of six CDRs as set forth in one of Tables 1-26, and having 0, 1, 2 or 3 amino acid modifications in each CDR.

[0090] In another aspect, the invention provides an antibody, or a molecule comprising at least an antigen-binding fragment thereof, which comprises a set of six CDRs as set forth in one of Tables 1-26. In another aspect, the invention provides an antibody, or a molecule comprising at least an antigen-binding fragment thereof, which comprises a set of VH and VL regions of an antibody listed in Table 28. In another aspect, the invention provides an antibody, or a molecule comprising at least an antigen-binding fragment thereof, which comprises a set of VH and VL regions of an antibody listed in Table 27. In another aspect, the invention relates to an antibody, or a molecule comprising at least an antigen binding fragment thereof, which binds to an epitope on hSLAMF6 recognized by an antibody as disclosed herein, or which cross-competes for hSLAMF6 binding with an antibody as disclosed herein.

[0091] In another aspect, there is provided a nucleic acid construct encoding the antibody or molecule. According to an exemplary embodiment, the nucleic acid construct comprises comprising a nucleic acid sequence as set forth in SEQ ID NO: 143 or 145, or has at least 90%, 95%, 98% or 99% identity thereto. In another aspect there is provided a host cell comprising at least one nucleic acid construct encoding the antibody of the invention.

[0092] In another aspect, the invention provides a pharmaceutical composition comprising a therapeutically effective amount of at least one antibody or molecule according to the invention.

[0093] In another aspect, there is provided a pharmaceutical composition comprising a therapeutically effective amount of at least one antibody or molecule according to the invention, for use in therapy. In another embodiment the pharmaceutical composition is for use in treating cancer in a subject in need thereof. In another aspect, there is provided a method of treating cancer in a subject in need thereof, comprising administering to the subject the pharmaceutical composition.

[0094] In another aspect, the invention provides a method for detecting or quantifying the presence of SLAMF6 in a sample, comprising the steps of:

[0095] (i) incubating the sample with the antibody or molecule, under conditions enabling the formation of an antigen-antibody complex; and

[0096] (ii) detecting or quantifying the antigen-antibody complex.

[0097] These and other embodiments will be discussed in greater detail below.

[0098] Antibodies

[0099] In one embodiment, the invention relates to a monoclonal antibody specific to SLAMF6, or a molecule comprising at least an antigen-binding fragment thereof, in particular, antibodies in accordance with the invention are directed to human SLAMF6.In another embodiment said antibody is selected from the group consisting of a monoclonal murine antibody, a monoclonal chimeric antibody, a monoclonal humanized antibody and a monoclonal fully human antibody. In another embodiment said antibody is an intact antibody. In another embodiment the invention relates to a molecule comprising at least an antigen-binding fragment of the antibody, wherein said fragment is selected from the group consisting of: Fab, Fab', Fd, Fd', Fv, dAb, F(ab')2, single chain Fv, diabody and linear antibody. In another embodiment said molecule is a monovalent molecule selected from the group consisting of Fab, Fab', Fd, Fd', Fv, dAb, single chain Fv and linear antibody.

[0100] The term "antibody" (or Ab) as used herein refers to an immunoglobulin or fragment thereof, and encompasses any molecule (e.g. polypeptide) comprising an antigen-binding fragment or an antigen-binding domain. The term includes but is not limited to monoclonal, humanized, human, single-chain, chimeric, synthetic, recombinant, hybrid, mutated, grafted, and in vitro generated antibodies. In some embodiments, e.g. unless preceded by the word "intact", the term "antibody" includes antibody fragments such as Fab, Fab’ F(ab')2, Fv and other antibody fragments that retain antigen-binding function. Typically, such fragments would comprise an antigen-binding domain. Such molecules may be provided by any known technique, including, but not limited to, enzymatic cleavage, peptide synthesis or recombinant techniques. Additional examples include e.g. (scFv)2, dAb, Fd fragments, diabodies, F(ab')3, disulfide linked Fv, sdAb (VHH or nanobody), di-scFv, bi-scFv, tascFv (tandem scFv), triabody, tetrabody, and the like.

[0101] Antibodies, or immunoglobulins, comprise two heavy chains linked together by disulfide bonds and two light chains, each light chain being linked to a respective heavy chain by disulfide bonds in a "Y" shaped configuration. Proteolytic digestion of an antibody yields Fv (Fragment variable) and Fc (fragment crystalline) domains. The antigen binding domains, Fab', include regions where the polypeptide sequence varies. The term F (ab' represents two Fab' arms linked together by disulfide bonds. The central axis of the antibody is termed the Fc fragment, and is known to mediate phagocytosis, trigger inflammation and target Ig to particular tissues; the Fc portion is also important in complement activation. Each heavy chain has at one end a variable domain (VH) followed by a number of constant domains (CH). Each light chain has a variable domain (VL) at one end and a constant domain (CL) at its other end, the light chain variable domain being aligned with the variable domain of the heavy chain and the light chain constant domain being aligned with the first constant domain of the heavy chain (CHI).

[0102] The variable domains of each pair of light and heavy chains form the antigen binding site. The domains on the light and heavy chains have the same general structure and each domain comprises four framework regions, whose sequences are relatively conserved, joined by three hypervariable domains known as complementarity determining regions (CDR1-3). These hypervariable domains contribute to the specificity and affinity of the antigen binding site.

[0103] The terms "antigen-binding domain" and "antigen-binding fragment" refer to a part of an antibody molecule that comprises-amino acids responsible for the specific binding between antibody and antigen. The part of the antigen that is specifically recognized and bound by the antibody is referred to as the “epitope”. An antigen-binding domain may comprise an antibody light chain variable region (VL) and an antibody heavy chain variable region (VH); however, it does not have to comprise both. Fd fragments, for example, have two VH regions and often retain some antigen-binding function of the intact antigen-binding domain.

[0104] Epitopes or antigenic determinants usually consist of chemically active surface groupings of molecules such as amino acids or sugar side chains and have specific three-dimensional structural characteristics as well as specific charge characteristics.

[0105] An "antigen" is a molecule or a portion of a molecule capable of being bound by an antibody, which is additionally capable of inducing an animal to produce antibodies capable of binding to an epitope of that antigen. An antigen may have one or more than one epitope. The specific reaction referred to herein is meant to indicate that the antigen will react, in a highly selective manner, with its corresponding antibody and not with the multitude of other antibodies which may be evoked by other antigens.

[0106] The isotype of the heavy chain (gamma, alpha, delta, epsilon or mu) determines immunoglobulin class (IgG, IgA, IgD, IgE or IgM, respectively). The light chain is either of two isotypes (kappa, or lambda,) found in all antibody classes. Single chain antibodies fall within the scope of the present invention. Single chain antibodies can be single chain composite polypeptides having antigen binding capabilities and comprising amino acid sequences homologous or analogous to the variable regions of an immunoglobulin light and heavy chain (linked Vn-V or single chain Fv (ScFv)). Both VH and VL may copy natural monoclonal antibody sequences or one or both of the chains may comprise a CDR-FR construct of the type described in US patent 5,091,513, the entire contents of which are hereby incorporated herein by reference. The separate polypeptides analogous to the variable regions of the light and heavy chains are held together by a polypeptide linker. Methods of production of such single chain antibodies, particularly where the DNA encoding the polypeptide structures of the VH and VL chains are known, may be accomplished in accordance with the methods described, for example, in US patents 4,946,778, 5,091, 513 and 5,096,815, the entire contents of each of which are hereby incorporated herein by reference.

[0107] Fab miniantibodies (see WO 93 / 15210, WO 96 / 13583 and WO 96 / 37621, the entire contents of which are incorporated herein by reference) and chimeric or single-chain antibodies incorporating such reactive fraction, as well as any other type of molecule or cell in which such antibody reactive fraction has been physically inserted, such as a chimeric T-cell receptor, are also encompassed within certain embodiments of the present invention. Such molecules may be provided by any known technique, including, but not limited to, enzymatic cleavage, peptide synthesis or recombinant techniques.

[0108] Methods of generating monoclonal and polyclonal antibodies are well known in the art. Antibodies may be generated via any one of several known methods, which may employ induction of in vivo production of antibody molecules, screening of immunoglobulin libraries, or generation of monoclonal antibody molecules by continuous cell lines in culture. These include, but are not limited to, the hybridoma technique, the human B-cell hybridoma technique, and the Epstein-Barr virus (EBV) -hybridoma technique.

[0109] In cases where target antigens are too small to elicit an adequate immunogenic response when generating antibodies in vivo, such antigens (referred to as "haptens") can be coupled to antigenically neutral carriers such as keyhole limpet hemocyanin (KLH) or serum albumin (e.g., bovine serum albumin (BSA)) carriers (see, for example, US. Pat. Nos. 5,189,178 and 5,239,078). Coupling a hapten to a carrier can be effected using methods well known in the art. For example, direct coupling to amino groups can be effected and optionally followed by reduction of the imino linkage formed. Alternatively, the carrier can be coupled using condensing agents such as dicyclohexyl carbodiimide or other carbodiimide dehydrating agents. Linker compounds can also be used to effect the coupling; both homobifunctional and heterobifunctional linkers are available from Pierce Chemical Company, Rockford, Illinois, USA. The resulting immunogenic complex can then be injected into suitable mammalian subjects such as mice, rabbits, and others. Suitable protocols involve repeated injection of the immunogen in the presence of adjuvants according to a schedule designed to boost production of antibodies in the serum. The titers of the immune serum can readily be measured using immunoassay procedures which are well known in the art.

[0110] The antisera obtained can be used directly (e.g. as diluted sera or as purified polyclonal antibodies), or monoclonal antibodies may be obtained, as described herein.

[0111] A monoclonal antibody (mAb) is a substantially homogeneous population of antibodies to a specific antigen. The term "monoclonal antibody" as used herein refers to an antibody (typically intact) obtained from a population of substantially homogeneous antibodies, i.e., the individual antibodies comprising the population are identical except for possible naturally occurring mutations that may be present in minor amounts. Monoclonal antibodies are highly specific, being directed against a single antigen. Furthermore, in contrast to polyclonal antibody preparations that typically include different antibodies directed against different determinants (epitopes), each monoclonal antibody is directed against a single determinant on the antigen. The modifier "monoclonal" is not to be construed as requiring production of the antibody by any particular method. mAbs may be obtained by methods known to those skilled in the art. For example, the monoclonal antibodies to be used in accordance with the present invention may be made by hybridoma methods, or may be made by recombinant DNA methods (see, e.g., U.S. Pat. No. 4,816,567). The "monoclonal antibodies" may also be isolated from phage antibody libraries. See, for example US patent 4,376,110; Ausubel et al ("Current Protocols in Molecular Biology," Volumes I-III, John Wiley & Sons, Baltimore, Maryland, 1994).

[0112] A hybridoma producing a mAb may be cultivated in vitro or in vivo. High titers of mAbs can be obtained in in vivo production where cells from the individual hybridomas are injected intraperitoneally into pristine-primed Balb / c mice to produce ascites fluid containing high concentrations of the desired mAbs. mAbs of isotype IgM or IgG may be purified from such ascites fluids, or from culture supernatants, using column chromatography methods well known to those of skill in the art.

[0113] Antibody fragments may be obtained using methods well known in the art. (See, for example, Harlow, E. and Lane, D. (1988). Antibodies: A Laboratory Manual, Cold Spring Harbor Laboratory, New York). For example, antibody fragments according to the present invention can be prepared by proteolytic hydrolysis of the antibody or by expression in E. coli or mammalian cells (e.g., Chinese hamster ovary (CHO) cell culture or other protein expression systems) of DNA encoding the fragment. Alternatively, antibody fragments can be obtained by pepsin, papain or ficin digestion of whole antibodies by conventional methods. As described hereinabove, (Fab’ antibody fragments can be produced by enzymatic cleavage of antibodies with pepsin to provide a 5S fragment. This fragment can be further cleaved using a thiol reducing agent, and optionally a blocking group for the sulfhydryl groups resulting from cleavage of disulfide linkages, to produce 3.5S Fab’ monovalent fragments. Alternatively, enzymatic cleavage using pepsin produces two monovalent Fab’ fragments and an Fc fragment directly and enzymatic cleavage using ficin in the presence of high concentration reducing agent produces two monovalent Fab fragments and cleaved Fc fragments. Ample guidance for practicing such methods is provided in the literature of the art (for example, refer to: U.S. Pat. Nos. 4,036,945 and 4,331,647). Other methods of cleaving antibodies, such as separation of heavy chains to form monovalent light-heavy chain fragments, further cleavage of fragments, or other enzymatic, chemical, or genetic techniques may also be used, so long as the fragments retain the ability to bind to the antigen that is recognized by the intact antibody.

[0114] Besides the conventional method of raising antibodies in vivo, antibodies can be generated in vitro using phage display technology. Such a production of recombinant antibodies is much faster compared to conventional antibody production and they can be generated against an enormous number of antigens. In contrast, in the conventional method, certain antigens prove to be non-immunogenic or extremely toxic, and therefore cannot be used to generate antibodies in animals. Moreover, affinity maturation (i.e., increasing the affinity and specificity) of recombinant antibodies is very simple and relatively fast. Finally, large numbers of different antibodies against a specific antigen can be generated in one selection procedure. To generate recombinant monoclonal antibodies one can use various methods all based on phage display libraries to generate a large pool of antibodies with different antigen recognition sites. Such a library can be made in several ways: One can generate a synthetic repertoire by cloning synthetic CDR3 regions in a pool of heavy chain germline genes and thus generating a large antibody repertoire, from which recombinant antibody fragments with various specificities can be selected. One can use the lymphocyte pool of humans as starting material for the construction of an antibody library. It is possible to construct naive repertoires of human IgM antibodies and thus create a human library of large diversity. This method has been widely used successfully to select a large number of antibodies against different antigens. Protocols for bacteriophage library construction and selection of recombinant antibodies are provided in the well-known reference text Current Protocols in Immunology, Colligan et al (Eds.), John Wiley & Sons, Inc. (1992- 2000), Chapter 17, Section 17.1. As described hereinabove, an Fv is composed of paired heavy chain variable and light chain variable domains. This association may be noncovalent. Alternatively, as described hereinabove, the variable domains may be linked to generate a single-chain Fv by an intermolecular disulfide bond, or alternately such chains may be cross-linked by chemicals such as glutaraldehyde.

[0115] Preferably, the Fv is a single-chain Fv. Single-chain Fvs are prepared by constructing a structural gene comprising DNA sequences encoding the heavy chain variable and light chain variable domains connected by an oligonucleotide encoding a peptide linker. The structural gene is inserted into an expression vector, which is subsequently introduced into a host cell such as E. coli. The recombinant host cells synthesize a single polypeptide chain with a linker peptide bridging the two variable domains. Ample guidance for producing single-chain Fvs is provided in the literature of the art. Improved bivalent miniantibodies, with identical avidity as whole antibodies, may be produced by high cell density fermentation of Escherichia coli. (U.S. Pat. No. 4,946,778).

[0116] Isolated complementarity-determining region peptides can be obtained by constructing genes encoding the CDR of an antibody of interest. Such genes may be prepared, for example, by RT-PCR of the mRNA of an antibody -producing cell. Ample guidance for practicing such methods is provided in the literature of the art.

[0117] The term "human antibody" includes antibodies having variable and constant regions corresponding substantially to human germline immunoglobulin sequences known in the art. The human antibodies of the invention may include amino acid residues not encoded by human germline immunoglobulin sequences (e.g., mutations introduced by random or site-specific mutagenesis in vitro or by somatic mutation in vivo), for example in the CDRs, and in particular, CDR3. The human antibody can have at least one, two, three, four, five, or more positions replaced with an amino acid residue that is not encoded by the human germline immunoglobulin sequence.

[0118] Chimeric antibodies are molecules, the different portions of which are derived from different animal species, such as those having a variable region derived from a murine mAb and a human immunoglobulin constant region. Antibodies which have variable region framework residues substantially from human antibody (termed an acceptor antibody) and complementarity determining regions substantially from a mouse antibody (termed a donor antibody) are also referred to as humanized antibodies. Chimeric antibodies are primarily used to reduce immunogenicity in application and to increase yields in production, for example, where murine mAbs have higher yields from hybridomas but higher immunogenicity in humans, such that human / murine chimeric mAbs are used. Chimeric antibodies and methods for their production are known in the art (e.g. European Patent Applications 125023, 171496, 173494, 184187, 173494, PCT patent applications WO 86 / 01533, WO 97 / 02671, WO 90 / 07861, WO 92 / 22653 and US patents 5,693,762, 5,693,761, 5,585,089, 5,530,101 and 5,225,539). Additionally, CDR grafting may be performed to alter certain properties of the antibody molecule including affinity or specificity. A non-limiting example of CDR grafting is disclosed in US patent 5,225,539. Further methods for producing chimeric and humanized antibodies are described, for example, in US patent 4,816,567 and Almagro., J.C., et.al, 2018., Front. Immunol. 8,1751. These references are hereby incorporated by reference.

[0119] It will be appreciated that for human therapy, humanized antibodies are preferably used. Humanized forms of non-human (e.g., murine) antibodies are genetically engineered chimeric antibodies or antibody fragments having (preferably minimal) portions derived from non-human antibodies. Humanized antibodies include antibodies in which the CDRs of a human antibody (recipient antibody) are replaced by residues from a CDR of a non-human species (donor antibody), such as mouse, rat, or rabbit, having the desired functionality. In some instances, the Fv framework residues of the human antibody are replaced by corresponding non-human residues. Humanized antibodies may also comprise residues found neither in the recipient antibody nor in the imported CDR or framework sequences. In general, the humanized antibody will comprise substantially all of at least one, and typically two, variable domains, in which all or substantially all of the CDRs correspond to those of a non-human antibody and all or substantially all of the framework regions correspond to those of a relevant human consensus sequence. Humanized antibodies optimally also include at least a portion of an antibody constant region, such as an Fc region, typically derived from a human antibody.

[0120] Methods for humanizing non-human antibodies are well known in the art. Generally, a humanized antibody has one or more amino acid residues introduced into it from a source which is non-human. These non-human amino acid residues are often referred to as imported residues, which are typically taken from an imported variable domain. Humanization can be performed as is known in the art (see, for example: U.S. Pat. No. 4,816,567), by substituting human CDRs with corresponding rodent CDRs. Accordingly, humanized antibodies are chimeric antibodies, wherein substantially less than an intact human variable domain has been substituted by the corresponding sequence from a non-human species. In practice, humanized antibodies may be typically human antibodies in which some CDR residues and possibly some framework residues are substituted by residues from analogous sites in rodent antibodies. Human antibodies can also be produced using various additional techniques known in the art, including phage-display libraries. Humanized antibodies can also be created by introducing sequences encoding human immunoglobulin loci into transgenic animals, e.g., into mice in which the endogenous immunoglobulin genes have been partially or completely inactivated. Upon antigenic challenge, human antibody production is observed in such animals which closely resembles that seen in humans in all respects, including gene rearrangement, chain assembly, and antibody repertoire. Ample guidance for practicing such an approach is provided in the literature of the art (for example, refer to: U.S. Pat. Nos. 5,545,807; 5,545,806; 5,569,825; 5,625,126; 5,633,425; and 5,661,016).

[0121] In another embodiment, antibodies of the invention may comprise a human or humanized constant (Fc) region, e.g. of the IgGl or IgG4 isotype. In another embodiment said Fc region is an engineered human IgGl or IgG4 that does not substantially bind to Fey receptors. For example, Fc sequences in which a L234AL235A (LALA) mutation has been introduced in accordance with embodiments of the invention, e.g. as disclosed and exemplified herein. For example, without limitation, the hIgGl(L234AL235A) constant region including a L234AL235A mutation (e.g. SEQ ID NOs: 141) or the hIgG4(S228P) constant region including a S228P mutation (e.g. SEQ ID NOs: 142) may be used.

[0122] Additional humanized Fc regions are described in Wilkinson, I., et.al, 2021, PLoS ONE16, e0260954, incorporated herein by reference.

[0123] After antibodies have been obtained, they may be tested for activity, for example via enzyme-linked immunosorbent assay (ELISA).

[0124] Functional properties

[0125] In various embodiments, the antibodies of the present invention are anti-SLAMF6 antibodies, i.e. Abs that specifically bind to SLAMF6, more specifically human SLAMF6 (hSLAMF6). The terms "specific binding" or "specifically binds" refers to two molecules forming a complex that is relatively stable under physiologic conditions. Specific binding is characterized by a high affinity and a low to moderate capacity as distinguished from nonspecific binding which usually has a low affinity with a moderate to high capacity. Typically, binding is considered specific when the association constant KA is higher than 106M'1. If necessary, nonspecific binding can be reduced without substantially affecting specific binding by varying the binding conditions. The appropriate binding conditions, such as concentration of antibodies, ionic strength of the solution, temperature, time allowed for binding, concentration of a blocking agent (e.g., serum albumin, milk casein), etc., may be optimized by a skilled artisan using routine techniques. The term “specifically bind” as used herein may further indicate that the binding of an antibody to an antigen is not competitively inhibited by the presence of non-related molecules. Conveniently, detection of the capacity of an antibody to specifically bind an antigen, e.g. hSLAMF6, may be performed by quantifying specific antigen-antibody complex formation (e.g. by immunoassays such as ELISA).

[0126] Generally, SLAMF6 is comprised of the following domains in the order of N’ to C’:

[0127] I. an N-terminal signal peptide;

[0128] II. an extracellular portion (ectodomain), comprising two conserved immunoglobulin (Ig)- like motifs: an N’ Ig-like V-type domain (IgV, having a two-layered P-sheet structure, with predominantly neutral, albeit polar, front surfaces), and a C’ Ig-like C2-type domain (IgC2, characterized by an overall P-strand topology and several disulfide bonds);

[0129] III. a helical transmembrane domain; and

[0130] IV. a topological (cytoplasmic) domain, containing immunoreceptor tyrosine-based switch motifs (ITSMs), which are docking sites for the SH2 domain of SLAM-associated protein (SAP) and the related Ewing’s sarcoma-associated transcript. ITSM motifs carry the consensus sequence TxYxxV / I / L that have overlapping specificity for activating and inhibitory binding partners.

[0131] The term "human SLAMF6" (hSLAMF6) refers to a SLAMF6 polypeptide of human origin, and encompasses SLAMF6 variants naturally occurring in human cells (e.g. splice variants, alleles and isoforms) and recombinantly produced polypeptides, as described herein.

[0132] For example, in canonical human SLAMF6 (e.g. accession no. Q96DU3, isoform 1), the signal peptide has been identified to be located at positions 1-21 of the transcribed polypeptide, the ectodomain has been identified to be located at positions 22-226 (wherein IgV was located at positions 35-120 and IgC2 at positions 132-209), the transmembrane domain was located at positions 227-247, and the cytoplasmic (intracellular) domain - at positions 248-331. Exon 2 encodes for the amino acids at positions 17-128. Human SLAMF6var2differs from SLAMF6varlby deletion of a single alanine at position 266 . Human SLAMF6var3(precursor, NM_001184715.1) differs from SLAMF6varl(Q96DU3, isoform 1) by deletion of amino acids (aa) 17-65. The deletion includes aa 17-21 residing in the signal peptide, and aa 22-65, residing in the ectodomain. Human SLAMF6var4(precursor, NM_001184716.1) differs from SLAMF6varlby deletion of aa 18-128.

[0133] In some embodiments, an antibody of the invention (or a molecule comprising at least an antigen-binding fragment thereof) is characterized in that it induces or enhances direct cell- mediated cytotoxicity by primary human lymphocytes (that does not require FcR binding and induction of drug-induced toxicity, ADCC or CDC). In another embodiment, the lymphocytes are tumor- specific lymphocytes. In another embodiment, the antibody induces or enhances tumor- induced Granzyme B secretion from said lymphocytes. In another embodiment, said antibody induces or enhances said direct cell-mediated cytotoxicity without substantially inducing or enhancing drug-induced toxicity, ADCC and CDC. In another embodiment, said antibody induces or enhances the direct cell-mediated cytotoxicity of primary human lymphocytes under conditions insufficient for substantially inducing or enhancing proliferation of said lymphocytes.

[0134] The term “primary” and analogous terms in reference to a cell or cell population as used herein correspond to their commonly understood meaning in the art, i.e., referring to cells that have been obtained directly from living tissue (i.e. a biopsy) or bodily fluid (e.g. a blood sample) or from a subject, which cells have not been passaged in culture, or have been passaged and maintained in culture but without immortalization.

[0135] For example, primary human lymphocytes may be obtained from human peripheral blood mononuclear cells (PBMC) or human tumor biopsies. In various embodiments, the lymphocytes comprise or consist of T cells, B cells NK cells and combinations thereof.

[0136] The term "tumor- specific lymphocytes" indicates a cell population containing purified or enriched lymphocytes having an antigen receptor (e.g. a T cell receptor) that is specific to a tumor antigen. For example, tumor- specific lymphocytes may be obtained from PBMC samples by selection or culture using a tumor antigen (or suitable antibodies directed to a tumor- specific antigen receptor). Tumor-infiltrating lymphocytes (TIL) may be isolated or purified from human tumor biopsies, e.g. by selection for lymphocyte markers using cell sorting or magnetic separation. In some embodiments the tumor- specific lymphocytes are effector cells such as tumorspecific cytotoxic T lymphocytes (CTL).

[0137] The term “cytotoxic” or “cytotoxicity” refers to killing or damaging cells. In this context, the term "direct" indicates that binding of the antigen-binding domain of an antibody to its antigen is sufficient to elicit the cytotoxic response, without the need for the antibody constant domain (Fc) to bind an Fc receptor on a responding lymphocyte. Without wishing to be bound by a specific theory or mechanism of action, specific binding of an antibody of the invention to its SLAMF6 epitope on an immune cell induces or enhances the responsiveness of the immune cell to an encountered tumor cell. This term is thus differentiated from other mechanisms such as ADCC and CDC which require FcR binding.

[0138] Cell mediated cytotoxicity includes cytotoxic cytolytic exerted by immune cells, typically effector cells such as CTL and / or NK cells. For example, in case of T cells as the primary human lymphocytes, T cell-mediated cytotoxicity refers to the directed killing of a target cell by a T cell, in particular through the release of granules containing cytotoxic mediators or through the engagement of death receptors. In an exemplary embodiment, the cytotoxic activities include - tumor-induced secretion of Granzyme B (namely enhanced secretion of the cytotoxic mediator Granzyme B specifically in the presence of tumor cells).

[0139] The term “drug-induced toxicity” refers to cytotoxicity induced by a drug-conjugated antibody (also known as targeted drug therapy). For example, cancer therapeutics involving drug- induced toxicity include tumor- specific antibodies conjugated to toxins, chemotherapeutic drugs or radioisotopes.

[0140] The term “complement-dependent cytotoxicity” or “CDC” refers to a mechanism for inducing cell death in which the Fc effector domain of a target-binding antibody binds to and activates a complement component Clq, and Clq then activates the complement cascade, resulting in the death of the target cell. Activation of a complement may also result in the deposition of complement components on the surface of target cells that promote CDC by binding to complement receptors on leukocytes (e.g., CR3).

[0141] The term “antibody-dependent cellular cytotoxicity” or “ADCC” is a mechanism for inducing cell death that depends upon the interaction of antibody-coated target cells with effector cells possessing lytic activity (such as natural killer cells, monocytes, macrophages and neutrophils) via Fc gamma receptors (FcyR) expressed on effector cells.

[0142] As disclosed herein, antibodies of the invention are capable of inducing or enhancing antitumor cytotoxicity to an extent that is independent from (and cannot be attributed solely to) FcR- dependent mechanisms such as ADCC and CDC. As further disclosed herein, antibodies of the invention are further capable of inducing or enhancing said direct cell-mediated cytotoxicity without substantial (statistically significant) induction or enhancement of ADCC and / or CDC. In another embodiment, the antibody or molecule binds to a SLAMF6 polypeptide having the amino acid sequence as set forth in SEQ ID NO: 130 with an equilibrium dissociation constant (KD) of l.OlxlO’07M to 4.85xlO’10M. Yet in certain advantageous embodiments, provided are antibodies characterized by exceptional anti-tumor activity while exhibiting moderate binding affinity to hSLAMF6. In a particular embodiment, the antibody or molecule binds to a SLAMF6 polypeptide having the amino acid sequence as set forth in SEQ ID NO: 130 with a KD of 9x10’08M to IxlO’9M. It is to be understood, that SEQ ID NO: 130 sets forth the polypeptide precursor of a recombinant polypeptide comprising the human SLAMF6 (hSLAMF6) ectodomain fused at its C to a histidine tag (herein denoted SLAMF6-ECD-6 HIS), including the signal that is typically absent in the mature polypeptide. Thus, it may also be considered that the antibody or molecule of the invention binds to a SLAMF6 polypeptide corresponding to (or obtained from) a precursor having the amino acid sequence as set forth in SEQ ID NO: 130 with a KD of 1.01x10’07M to 4.85xl0’10M, IO’07to 10’8M, or 9xl0’08M to IxlO’9M.

[0143] The term dissociation constant (KD) as used herein refers to an equilibrium constant that measures the propensity of a complex of associated molecules to separate (dissociate) reversibly into the separate molecules. In the context of the present specification, the term KD refers in particular to antibody-antigen complexes and is typically expressed in molar concentration [mol / L] corresponding to the concentration of antibody at which half of the binding sites of the antigen are occupied.

[0144] In various embodiments, antibodies in accordance of the invention are characterized by KD values in the range of IO’07M to 5xl0’10M to their cognate antigen. For example, as demonstrated herein, antibodies of the invention bind (i.e. specifically bind) to a SLAMF6 polypeptide having the amino acid sequence as set forth in SEQ ID NO: 130 with a KD of 1.01x10’07M to 4.85xl0’10M. In some embodiments, antibodies of the invention remarkably exhibit moderate binding affinity (in the range of 10’08M to IxlO’9M) to hSLAMF6 (e.g. SEQ ID NO: 130) without compromising the exerted anti-tumor activity.

[0145] As used herein, the term "anti-tumor activity" refers to the ability of the antibody to specifically inhibit, delay or impair tumor growth, viability and / or expansion (e.g. in vivo or in the presence of immune cells in culture). In some embodiments, the anti-tumor activity is conveniently evaluated as enhancement of direct cell-mediated cytotoxicity, as disclosed herein.

[0146] In some embodiments, the invention encompasses antibodies that bind to an epitope on hSLAMF6 recognized by an antibody of the invention (i.e. specifically bind to the epitope such as they compete for binding of hSLAMF6 with an antibody of the invention), as well as antibodies that cross-compete for hSLAMF6 binding with an antibody of the invention. The term “compete for binding” refers to the interaction of two antibodies in their binding to a binding target. A first antibody competes for binding with a second antibody if binding of the first antibody with its cognate epitope is detectably decreased in the presence of the second antibody compared to the binding of the first antibody in the absence of the second antibody. The alternative, where the binding of the second antibody to its epitope is also detectably decreased in the presence of the first antibody, can, but need not, be the case. That is, a first antibody can inhibit the binding of a second antibody to its epitope without that second antibody inhibiting the binding of the first antibody to its respective epitope. However, where each antibody detectably inhibits the binding of the other antibody with its cognate epitope, whether to the same, greater, or lesser extent, the antibodies are said to “cross-compete” with each other for binding of their respective epitope(s). Assays for evaluating antibody competition and cross competition are known in the art and include various immunoassays e.g. as disclosed and exemplified herein.

[0147] As used herein and in the context of a targeting agent (e.g., antibody), the term “cross- reactive,” refers to a property of the agent being capable of specifically binding to more than one antigen of a similar type or class (e.g., related antigens that are homologs, paralogs, or orthologs and may have a shared epitope) with similar affinity or avidity. For example, in some embodiments, an antibody that is cross-reactive against human and non-human primate antigens of a similar type or class (e.g., a human SLAMF6 and non-human primate SLAMF6) is capable of binding to the human antigen and non-human primate antigens with a similar affinity or avidity. In a particular embodiment the antibody is cross-reactive with cynomolgus monkey SLAMF6 (cynoSLAMF6, e.g. SEQ ID NO: 131). Methods of assessing cross -reactivity are known to one skilled in the art (e.g. US 20090311253) and exemplified in the Examples below.

[0148] In another embodiment the antibody or molecule exhibits a functional property as disclosed and exemplified herein. In another embodiment said antibody or molecule exhibits a plurality of functional properties as disclosed and exemplified herein.

[0149] Structural properties

[0150] In one particular embodiment, the antibody is monoclonal murine mAb as exemplified herein, e.g. mAb sub-clone Ab01-Ab23 as described herein. In another embodiment the antibody is a chimeric humanized or fully humanized antibody as exemplified herein, e.g. designated cmAbO2-IgG4, cmAbO4-IgG4, cmAbO4-IgGl, cmA007-IgG4, cmAbl9-IgG4, AbO7-VH(NG_GG), AbO7-VH(NG_ SG), AbO7-VH(NG. _NA), AbO19-VL(DG_ SG), AbO19-VL(DG_DA) or AbO19-VL(DG_GG) (chimeric antibodies) or Hu007-05 (BM1), Hu007-06 (BM3), Hu007-07 (BM5), Hu007-08 (BM7), Hu007-09 (BM2), Hu007-10 (BM4), Hu007-ll (BM6), or Hu007-12 (BM8) (humanized antibodies). For example, disclosed herein is the production of chimeric and humanized antibodies, including antibodies comprising a humanized IgG4 constant region including a S228P (e.g. cmAbO2-IgG4, cmAbO4-IgG4, cmA007-IgG4 and cmAbl9-IgG4), or a fully humanized IgGl constant region including a L234AL235A mutation (e.g. AbO7-VH(NG_GG) and humanized antibodies derived therefrom such as Hu007-05 (BM1), Hu007-06 (BM3), Hu007-07 (BM5), Hu007-08 (BM7), Hu007-09 (BM2), Hu007-10 (BM4), Hu007-ll (BM6), and Hu007-12 (BM8). In another particular embodiment, said antibody is selected from the group consisting of Hu007- 05 (BM1), Hu007-08 (BM7), Hu007-09 (BM2) and Hu007-12 (BM8). In a particular embodiment said antibody is Hu007-08 (BM7).

[0151] It should be appreciated, that for human use, adequately purified antibody preparations (sufficiently sterile and free from toxic agents or other impurities) are used, as known in the art. In other specific embodiments, the antibody has substantially the same specificity as an antibody as disclosed herein. For example, the antibody may contain an antigen-binding fragment of said subclones or it may contain an antigen-binding fragment which is not identical to that of said subclones but recognizes the same SLAMF6 epitope in a specific manner.

[0152] In one embodiment, the antibody is characterized in that it competes with an antibody of the invention such as Ab01-Ab23, cmAbO2-IgG4, cmAbO4-IgG4, cmAbO4-IgGl, cmA007-IgG4, cmAbl9-IgG4, AbO7-VH(NG_GG), AbO7-VH(NG_sG), AbO7-VH(NG_NA), AbO19-VL(DG_sG), Ab019- VL(DG_DA), AbO19-VL(DG_GG), Hu007-05 (BM1), Hu007-06 (BM3), Hu007-07 (BM5), Hu007-08 (BM7), Hu007-09 (BM2), Hu007-10 (BM4), Hu007-ll (BM6), or Hu007-12 (BM8), on binding to human SLAMF6.

[0153] In one embodiment, there is provided an antibody specific to hSLAMF6, which comprises a set of VH and VL regions as set forth in SEQ ID NOs: 137 and 139, respectively. In another embodiment there is provided an antibody specific to hSLAMF6, which comprises VH and VL sequences having at least 90%, 95%, 98% or 99% identity to the VH and VL sequences as set forth in SEQ ID NOs: 137 and 139, respectively. In another embodiment the invention provides an antibody specific to hSLAMF6, which comprises a set of six CDRs as set forth in SEQ ID NOs: 7, 79, 13, 33, 11 and 15. In another embodiment the invention provides an antibody specific to hSLAMF6, which comprises a set of six CDRs as set forth in SEQ ID NOs: 147, 79, 13, 33, 11 and 15. In another embodiment the invention provides an antibody specific to hSLAMF6, which comprises a set of six CDRs as set forth in SEQ ID NOs: 148, 79, 13, 33, 11 and 15. In another embodiment the invention provides an antibody specific to hSLAMF6, which comprises a set of six CDRs comprising up to 3 amino acid modifications in each CDR as set forth in SEQ ID NOs: 7, 79, 13, 33, 11 and 15 (e.g. 1, 2 or 3 in one or more of said CDRs). In another embodiment the invention provides an antibody specific to hSLAMF6, which comprises a set of six CDRs comprising up to 3 amino acid modifications in each CDR as set forth in SEQ ID NOs: 147, 79, 13, 33, 11 and 15. In another embodiment the invention provides an antibody specific to hSLAMF6, which comprises a set of six CDRs comprising up to 3 amino acid modifications in each CDR as set forth in SEQ ID NOs: 148, 79, 13, 33, 11 and 15. In another embodiment there is provided a molecule comprising at least an antigen-binding fragment of said antibody. Each possibility represents a separate embodiment of the invention.

[0154] Sequences of exemplary mAb subclones identified in accordance with the invention, are provided in Table 28 below. In some embodiments, antibodies in accordance with the invention comprise VH and / or VL sequences of an antibody listed in Table 28, e.g. AbOl (100E9E2, SEQ ID NOs: 85-86), Ab02 (103A2G9, SEQ ID NO: 87-88), Ab03 (107D11H5, SEQ ID NO: 89-90), Ab04 (116A10A9, SEQ ID NO: 91-92), Ab05 (117F11A8, SEQ ID NO: 93-94), Ab06 (119C1H2, SEQ ID NO: 95-96), Ab07 (120F6B2, SEQ ID NO: 97-98), Ab08 (112G8C10, SEQ ID NO: 99- 100), Ab09 (95B8G6, SEQ ID NO: 101-102), AblO (104G2B10, SEQ ID NO: 89 and 103), Abl 1 (108F11G12, SEQ ID NO: 87 and 88), Abl2 (109E6G10, SEQ ID NO: 104-105), Abl3 (111E3D12, SEQ ID NO: 106-107), Abl4 (113H6A2, SEQ ID NO: 89 and 103), Abl5 (115G6C10, SEQ ID NO: 108 and 109), Abl6 (117A2E9, SEQ ID NO: 110-111), Abl7 (82B2B 1A5, SEQ ID NO: 112-113), Abl8 (120C9G2A4, SEQ ID NO: 114-115), Abl9 (101D8- 1F6-2C11, SEQ ID NO: 116-117), Ab20 (106G5F7-1G12, SEQ ID NO: 118-119), Ab21 (103C7E6D1, SEQ ID NO: 120-121), Ab22 (102A10B1B7, SEQ ID NO: 108-109) and Ab23 (69H3A6, SEQ ID NO: 122-123).

[0155] In another embodiment the antibody comprises a set of VH and VL of an antibody listed in Table 28. In another embodiment said antibody comprises VH and VL sequences having at least 90%, 95%, 98% or 99% identity to the VH and VL sequences of an antibody listed in Table 28, wherein each possibility represents a separate embodiment of the invention. In another embodiment said antibody comprises VH and VL sequences having at least 90%, 95%, 98% or 99% identity to the VH and VL sequences of an antibody listed in Table 28 wherein the CDR sequences of said antibody are retained. In a particular embodiment, antibodies and molecules comprising at least an antigen-binding portion thereof containing homologous VH and VL sequences to VH and VL sequences provided herein (e.g. 90%, 95%, 98% or 99% amino acid identity) are provided with the proviso that the amino acid at position 41 of the VL sequence is retained.

[0156] The terms "homology" and "sequence identity" as used herein refer to the degree of relatedness between two or more amino acid sequences, or two or more nucleic acid sequences, as determined by comparing the sequences. The comparison of sequences and determination of sequence identity or homology may be accomplished using a mathematical algorithm; those skilled in the art will be aware of computer programs available to align two sequences and determine the percent identity between them. The term "homology" refers in particular to the percentage of amino acid residues or nucleotides in a sequence that are identical with the residues of the reference polypeptide or polynucleotide with which it is compared, after aligning the sequences and in some embodiments after introducing gaps, if necessary, to achieve the maximum percentage homology, and not considering any conservative substitutions. As used here, the term “% identity,” which may be used interchangeably with the term “sequence identity”, in the context of two or more nucleic acid or polypeptide sequences, refer to two or more sequences that have a specified percentage of nucleotides or amino acid residues that are the same, when compared and aligned for maximum correspondence, as measured using a suitable sequence comparison algorithm (e.g., BLASTP and BLASTN or other algorithms available to persons of skill) or by visual inspection. Further, with respect to sequence identity as used herein, the overall length of the molecules compared is also taken into consideration, such that the degree of identity is calculated over the entire length of the sequences rather than locally.

[0157] The sequences of complementarity determining regions 1, 2 and 3 of the heavy chain (CDRHI, CDRH2 and CDRH3, respectively) and of the light chain (CDRLI, CDRL2 and CDRL3, respectively) of the antibodies listed in Table 28 are presented in Tables 1-20, as follows:

[0158] Table 1 - CDR sequences of AbOl

[0159] Table 2 - CDR sequences of Ab02 and Abl 1

[0160] Table 3 - CDR sequences of Ab03

[0161] Table 4 - CDR sequences of Ab04

[0162] Table 5 - CDR sequences of Ab05 Table 6 - CDR sequences of Ab06

[0163] Table 7 - CDR sequences of Ab07 Table 8 - CDR sequences of Ab08

[0164] Table 9 - CDR sequences of Ab09

[0165] Table 10 - CDR sequences of Ab 10 and Ab 14

[0166] Table 11 - CDR sequences of Ab 12

[0167] Table 12 - CDR sequences of Ab 13 Table 13 - CDR sequences of Ab 15 and Ab22

[0168] Table 14 - CDR sequences of Ab 16 Table 15 - CDR sequences of Ab 17

[0169] Table 16 - CDR sequences of Ab 18

[0170] Table 17 - CDR sequences of Ab 19

[0171] Table 18 - CDR sequences of Ab20

[0172] Table 19 - CDR sequences of Ab21

[0173] Table 20 - CDR sequences of Ab23

[0174] As can be determined from Tables 1-20, some of the antibody clones identified share one or more common CDR sequences. For example, SEQ ID NO: 7 denotes a CDRHI sequence shared between antibody clones Ab02, Ab03, Ab07, Ab08, AblO, Abl l, Abl4. In addition, Abl l was determined to have the same CDR set as Ab02, Ab22 was determined to have the same CDR set as Abl5, and Abl4 was determined to have the same CDR set as AblO.

[0175] In another embodiment an antibody or a molecule comprising at least an antigen-binding fragment thereof in accordance with the invention comprises a plurality of CDRs as set forth in Tables 1-20. In another embodiment the antibody or molecule comprises a set of six CDRs as set forth in one of Tables 1-20. In another embodiment said antibody or molecule has 0, 1, 2 or 3 amino acid modifications in each CDR as set forth in one of Tables 1-20. Each possibility represents a separate embodiment of the invention.

[0176] As used herein, the term “CDR set” refers to the three hypervariable regions of a heavy or light chain V region. Proceeding from the N-terminus of a heavy or light chain, these regions are denoted as “CDR1,” “CDR2,” and “CDR3” respectively. An antigen binding site, therefore, includes six CDRs, comprising the CDR set from each of a heavy and a light chain V region (also referred to herein as a set of six CDRs).

[0177] There are several methods known in the art for determining the CDR sequences of a given antibody molecule. Determination of CDR sequences from antibody heavy and light chain variable regions can be made according to any method known in the art, including but not limited to the methods known as KABAT, Chothia and IMGT. A selected set of CDRs may include sequences identified by more than one method, namely, some CDR sequences may be determined using KABAT and some using IMGT, for example. According to some embodiments, the CDR sequences of the mAb variable regions are determined using the Kabat and / or Chothia method. For example, the CDRHI sequences marked in Tables 32 and 33 were determined using both the Kabat and Chothia numbering systems, and are thus distinct from those listed in Table 28 determined using the Kabat numbering system alone (as were the other CDR sequences presented in Tables 32 and 33). It may thus be appreciated that a CDRHI sequence corresponding to SEQ ID NO: 7, for example (DYYMN, Kabat CDRHI of Hu007-08), may be used interchangeably with that of SEQ ID NO: 147 (GYTFTDYYMN, Kabat and Chothia CDRHI of Hu007-08), or SEQ ID NO: 148 (GYTFTDY, Chothia CDRHI of Hu007-08), in various embodiments of the invention.

[0178] Conservative substitutions of amino acids as known to those skilled in the art are within the scope of the present invention. Conservative amino acid substitutions include replacement of one amino acid with another having the same type of functional group or side chain, e.g., aliphatic, aromatic, positively charged, negatively charged.

[0179] In some embodiments, antibodies in accordance with the invention may comprise up to 3 amino acid modifications in each CDR, e.g. 0, 1, 2 or 3 modifications (e.g. substitutions, additions, or deletions) in one or more CDR sequence as described herein, wherein each possibility represents a separate embodiment of the invention. It is to be understood that an antibody comprising up to 3 amino acid modifications in each CDR of a CDR set as disclosed herein may have a different number of modifications in each CDR (e.g. a single amino acid substitution in CDRHI and two amino acid substitutions in CDRLI), or may have a CDR set comprising both modified and non-modified CDRs. It is to be further understood that such modifications may be introduced as long as the resulting antibody specificity to SLAMF6 is retained. Typically, the modifications are conservative substitutions.

[0180] In another embodiment, said antibody is a chimeric or humanized form of an antibody as disclosed herein, e.g. of an antibody as set forth in Table 28. Sequences of exemplary chimeric and humanized antibodies identified in accordance with the invention, are provided in Table 27 below. The sequences of CDRHI, CDRH2 and CDRHS, CDRLI, CDRL2 and CDRL3,of the antibodies listed in Table 27 are presented in Tables 21-26, as follows:

[0181] Table 21 - CDR sequences of Ab07 VH(NG_ GG) and humanized derivatives

[0182] Table 21 sets forth the CDR sequences of AbO7-VH(NG_GG) and humanized antibodies derived therefrom, including Hu007-05 (BM1), Hu007-06 (BM3), Hu007-07 (BM5), Hu007-08 (BM7), Hu007-09 (BM2), Hu007-10 (BM4), Hu007-ll (BM6), and Hu007-12 (BM8). Table 22 - CDR sequences of Ab07 VH(NG_SG)

[0183] Table 23 - CDR sequences of Ab07 VH(NG_NA) Table 24 - CDR sequences of Ab 19 VL(DG_SG)

[0184] Table 25 - CDR sequences of Ab 19 VL(DG_DA)

[0185] Table 26 - CDR sequences of Ab 19 VL(DG_GG)

[0186] In another embodiment an antibody or a molecule comprising at least an antigen-binding fragment thereof in accordance with the invention comprises a plurality of CDRs as set forth in Tables 21-26. In another embodiment the antibody or molecule comprises a set of six CDRs as set forth in one of Tables 21-26. In another embodiment said antibody or molecule has 0, 1, 2 or 3 amino acid modifications in each CDR as set forth in one of Tables 21-26. Each possibility represents a separate embodiment of the invention.

[0187] Table 27 - Sequences of exemplary chimeric and humanized antibodies

[0188] In another embodiment, the antibody comprises a set of VH and VL of an antibody listed in Table 27. In another embodiment said antibody comprises VH and VL sequences having at least 90%, 95%, 98% or 99% identity to the VH and VL sequences of an antibody listed in Table 27, wherein each possibility represents a separate embodiment of the invention. In another embodiment said antibody comprises VH and VL sequences having at least 90%, 95%, 98% or 99% identity to the VH and VL sequences of an antibody listed in Table 27 wherein the CDR sequences of said antibody are retained. In a particular embodiment, antibodies and molecules comprising at least an antigen-binding portion thereof containing homologous VH and VL sequences to VH and VL sequences provided herein (e.g. 90%, 95%, 98% or 99% amino acid identity) are provided with the proviso that the amino acid at position 41 of the VL sequence is retained. For example, in humanized antibodies derived from clones Ab07, Ab08, AblO, Abl l, Abl4, Abl8, Abl9 and Ab20 (e.g. including a framework derived from human IGKV2-30*01 VL), the leucine at position 41 is advantageously retained. In some embodiments, analogs and derivatives of sequences described herein retain at least the CDR sequences of the original sequence from which they are derived. In other embodiments, analogs and derivatives of sequences described herein retain the charge properties of the original sequence from which they are derived. In some embodiments, analogs or derivatives as described herein contain no more than 3, no more than 2, or no more than 1 amino acid substitutions.

[0189] In another embodiment, chimeric or humanized antibodies of the invention may comprise a human or humanized constant (Fc) region of the IgGl or IgG4 isotype. In another embodiment said Fc region is an engineered human IgGl or IgG4 that does not substantially bind to Fey receptors. In a particular embodiment said Fc region is an engineered human IgGl comprising a LALA mutation (e.g. a L234A-L235A mutation in human IgGl). In certain other exemplary embodiments, the CDRs are grafted into suitable human variable chains, including, but not limited to IGHV1-69*O2 and / or IGKV2-30*01. Examples of generating, characterizing and using antibodies in accordance with the invention, comprising variable regions and / or CDRs as disclosed herein with various forms of modified IgGl and IgG4 human Fc chains, are provided in the Examples below.

[0190] In another embodiment said antibody comprises VH and VL sequences having at least 90%, 95%, 98% or 99% identity to the VH and VL sequences of an antibody listed in Table 28 or 27 wherein the CDR sequences of said antibody (which may be determined according to known methods and / or numbering systems) are retained. In another embodiment said antibody comprises VH and VL sequences having at least 90%, 95%, 98% or 99% identity to the VH and VL sequences of an antibody listed in Table 28 or 27 wherein the CDR sequences of said antibody and the amino acid at position 41 of the light chain are retained. In another particular embodiment, the antibody to be used in compositions and methods in accordance with the invention is selected from the group consisting of Hu007-05 (BM1), Hu007-08 (BM7), Hu007-09 (BM2) and Hu007-12 (BM8). Each possibility represents a separate embodiment of the invention.

[0191] In some embodiments, there is provided an antibody comprising a human or humanized Fc region of the IgG4 isotype optionally engineered to substantially eliminate binding to Fey receptors, or a human or humanized Fc region of the IgGl isotype engineered to substantially eliminate binding to Fey receptors.

[0192] As used herein, an antibody that does not substantially bind to Fey receptors (or was engineered to substantially eliminate binding to Fey receptors) is an antibody characterized by lack of significant binding to said receptor under physiological conditions. Thus, the binding of such an antibody to FcyR under physiological conditions is insufficient to induce measurable (statistically significant) biological responses characteristic of binding of a native antibody via its Fc region to its cognate to Fey receptor.

[0193] Various binding assays known in the art may be used to determine binding of the antibody to Fey receptors, for example, immunoassays such as ELISA may be used, in which the FcyR is immobilized on a plate, and then the antibody (either in solution or immobilized) is added to the well. Binding can be detected using an enzyme-conjugated secondary antibody specific to the antibody’s Fc region. In addition, Surface Plasmon Resonance (SPR) may be used, to measure real-time binding kinetics of the antibody to FcyR. In this assay, changes in refractive index near the surface of a sensor chip is detected when an antibody binds to a receptor immobilized on the surface. Similarly, biolayer Interferometry (BLI) may be used, where the interaction between an antibody and FcyR immobilized on a biosensor is measured by detecting changes in the interference pattern of light reflected from the sensor surface.

[0194] Assays for biological responses characteristic of binding of a native antibody via its Fc region to its cognate to Fey receptor such as CDC and ADCC are also readily available to the skilled artisan. For example, an ADCC Reporter Bioassay may conveniently be used, which obviates the requirement for primary cell culture that is used in classical ADCC assays. In this assay, the primary effector cells are replaced by an engineered effector cell line expressing Fey Illa and NFAT-RE luciferase. When binding to an antibody Fc fragment, the reporter gene is activated and the luciferase activity is measured quantitatively to indicate antibody ADCC bioactivity.

[0195] These antibodies typically contain mutations at certain residues known to be involved in Fc binding to FcR. For example, engineered Fc regions to be used in humanized antibodies in accordance with the invention may be obtained by engineering (genetically modifying) constructs encoding naturally occurring human IgG4 or IgGl Fc domains, and inserting targeted mutations (e.g. non-conservative substitutions or deletions) at residues known to be involved in FcyR binding.

[0196] Modification that reduces binding of a CH2 domain to an Fc receptor, in particular an Fey receptor are well known in the art and. For example, without limitation, such mutations can be introduced at any one of the positions 233, 234, 235, 236, 237, 239, 263, 265, 267, 273, 297, 329, and 331, and may include: Glu 233->Pro (E233P), deletion of Glu 233, L234F, L234A, L234G, L234E, L234V, deletion of Leu 234, L235E, L235A, L235R, L235F, deletion of Leu 235, deletion of Gly 236, G237A, S239K, V263L, D265A, S267K, V273E, N297G, N297A, K332A, P329G, P331S and combinations thereof. Preferably, such a modification comprises one or both of Leu 234->Ala and Leu 235->Ala (also known as “LALA” mutation). Without wishing to be bound by a specific theory or mechanism of action, a LALA mutation may reduce FcyR binding and complement interactions, effectively dampening immune activation. Additional exemplary mutations that may be used to reduce or minimize FcR binding may be introduced at positions 270 and / or 297. For example, the D270A mutation inhibits FcyRIIa binding without affecting FcRn-mediated recycling while N297 glycan removal abolishes FcyR and Clq interactions.

[0197] The construction of exemplary humanized antibodies comprising engineered human Fc regions that do not substantially bind to Fey receptors is described in the Examples section below. In some embodiments, the humanized antibody has a heavy chain as set forth in SEQ ID NO: 144 below. In various embodiments, the heavy chain has at least 90%, 95%, 98% or 99% identity to SEQ ID NO: 144. In other embodiments, said heavy chain has at least 90%, 95%, 98% or 99% identity to SEQ ID NO: 144, and a set of CDRs as set forth in SEQ ID NOs: 7, 79, and 13. In other embodiments, the humanized antibody has a light chain as set forth in SEQ ID NO: 146 below. In various embodiments, the light chain has at least 90%, 95%, 98% or 99% identity to SEQ ID NO: 146. In other embodiments, said light chain has at least 90%, 95%, 98% or 99% identity to SEQ ID NO: 146, and a set of CDRs as set forth in SEQ ID NOs: 33, 11 and 15. In other embodiments, said humanized antibody has a heavy chain as set forth in SEQ ID NO: 144 and a light chain as set forth in SEQ ID NO: 146. In various embodiments, the heavy chain and light chain each have at least 90%, 95%, 98% or 99% identity to SEQ ID NOs: 144 and 146, respectively. In some embodiments, the heavy chain and light chain each have at least 90%, 95%, 98% or 99% identity to SEQ ID NOs: 144 and 146, respectively, and said antibody comprises a set of six CDRs as set forth in SEQ ID NOs: 7, 79, 13, 33, 11 and 15. Each possibility represents a separate embodiment of the invention.

[0198] Nucleic acid constructs

[0199] Polypeptides, peptides and nucleic acid molecules may conveniently be produced by recombinant technology. Recombinant methods for designing, expressing and purifying proteins, peptides and nucleic acid molecules are known in the art (see, e.g. Sambrook et al., 2001, Molecular Cloning: A Laboratory Manual, Cold Springs Harbor Laboratory, New York). Nucleic acid molecules may include DNA, RNA, or derivatives of either DNA or RNA. An isolated nucleic acid sequence encoding a polypeptide or peptide can be obtained from its natural source, either as an entire (i.e., complete) gene or a portion thereof. A nucleic acid molecule can also be produced using recombinant DNA technology (e.g., polymerase chain reaction (PCR) amplification, cloning) or chemical synthesis. Nucleic acid sequences include natural nucleic acid sequences and homologs thereof, including, but not limited to, modified nucleic acid sequences in which nucleotides have been inserted, deleted, substituted, and / or inverted in such a manner that such modifications do not substantially interfere with the nucleic acid molecule’s ability to encode a functional product. A polynucleotide or oligonucleotide sequence can be deduced from the genetic code of a protein, however, the degeneracy of the code must be taken into account, as well as the allowance of exceptions to classical base pairing in the third position of the codon, as given by the so-called “Wobble rules”. Polynucleotides that include more or less nucleotides can result in the same or equivalent proteins. Using recombinant production methods, selected host cells, e.g. of a microorganism such as E. coli or yeast, are transformed with a hybrid viral or plasmid DNA vector including a specific DNA sequence coding for the polypeptide and the polypeptide is synthesized in the host upon transcription and translation of the DNA sequence.

[0200] Such recombinant methods may also be used in the preparation of nucleic acid constructs, including in particular expression constructs or vectors used for delivering and expressing the antibodies of the invention host cell. The constructs comprise nucleic acid molecules encoding antibody chains of the invention, and may also comprise regulatory sequences or selectable markers, as known in the art. The nucleic acid construct (also referred to in some embodiments as a vector) may include additional sequences that render this vector suitable for replication and integration in prokaryotes, eukaryotes, or optionally both (e.g., shuttle vectors). In addition, a typical cloning vector may also contain transcription and translation initiation sequences, transcription and translation terminators, and a polyadenylation signal.

[0201] In another aspect, there is provided a nucleic acid construct encoding at least one chain of the isolated antibody. In another embodiment, the nucleic acid construct comprises at least one nucleic acid molecule encoding the antibody H and L chains as disclosed herein. In another embodiment, the at least one nucleic acid molecule is operatively linked to one or more transcription control elements.

[0202] In some embodiments, the antibody is a humanized antibody having a heavy chain encoded by a nucleic acid construct having the sequence as set forth in SEQ ID NO: 143 below. In some embodiments, the humanized antibody has a heavy chain encoded by a nucleic acid construct having at least 90%, 95%, 98% or 99% identity to SEQ ID NO: 143. In some embodiments, the humanized antibody has a light chain encoded by a nucleic acid construct having the sequence as set forth in SEQ ID NO: 145 below. In some embodiments, the humanized antibody has a light chain encoded by a nucleic acid construct having at least 90%, 95%, 98% or 99% identity to SEQ ID NO: 145. In other embodiments, the humanized antibody has a heavy chain encoded by a nucleic acid construct having the sequence as set forth in SEQ ID NO: 143 and a light chain encoded by a nucleic acid construct having the sequence as set forth in SEQ ID NO: 145. In other embodiments, the humanized antibody has a heavy chain encoded by a nucleic acid construct having at least 90%, 95%, 98% or 99% identity to SEQ ID NO: 143 and a light chain encoded by a nucleic acid construct having at least 90%, 95%, 98% or 99% identity to SEQ ID NO: 145. Each possibility represents a separate embodiment of the invention.

[0203] In another embodiment there is provided a nucleic acid construct comprising a nucleic acid sequence as set forth in SEQ ID NO: 143. In another embodiment there is provided a nucleic acid construct comprising a nucleic acid sequence having at least 90%, 95%, 98% or 99% identity to SEQ ID NO: 143. In another embodiment there is provided a nucleic acid construct comprising a nucleic acid sequence as set forth in SEQ ID NO: 145. In another embodiment there is provided a nucleic acid construct comprising a nucleic acid sequence having at least 90%, 95%, 98% or 99% identity to SEQ ID NO: 145. In another embodiment there is provided a nucleic acid construct comprising a nucleic acid sequence as set forth in SEQ ID NO: 143 and a nucleic acid sequence as set forth in SEQ ID NO: 145. In another embodiment there is provided a nucleic acid construct comprising a nucleic acid sequence having at least 90%, 95%, 98% or 99% identity to SEQ ID NO: 143 and a nucleic acid sequence having at least 90%, 95%, 98% or 99% identity to SEQ ID NO: 145. Each possibility represents a separate embodiment of the invention.

[0204] It is to be understood that sequences disclosed herein as protein precursors (or constructs encoding same) may optionally be provided in a mature, processed without their corresponding signal peptides. For example, as described in Example 7 below, the signal peptides are identified at positions 1-19 of SEQ ID NO: 144, at positions 1-22 of SEQ ID NO: 146, at positions 1-57 of the construct of SEQ ID NO: 143, and at positions 1-66 of the construct of SEQ ID NO: 145.

[0205] The phrase “operably linked” refers to a nucleic acid sequence linked a to a transcription control sequence in a manner such that the molecule is able to be expressed when transfected (i.e., transformed, transduced, infected, or transfected) into a host cell. Transcription control sequences are sequences, which control the initiation, elongation, and termination of transcription. Particularly important transcription control sequences are those which control transcription initiation, such as promoter, enhancer, operator and repressor sequences.

[0206] In another embodiment, the invention provides a host cell comprising the vector. The term “host cell” denotes a cell comprising an exogenous nucleic acid of interest, and is intended to include any individual cell or cell culture that can be or has / have been recipients of a nucleic acid molecule of the invention or a construct or vector encoding same, as well as the progeny thereof, as long as the nucleic acid molecule is present. Suitable host cells include prokaryotic or eukaryotic cells, and also include but are not limited to bacteria, yeast cells, and animal cells such as insect cells and mammalian cells, e.g., murine, rat, or human. According to specific embodiments, the host cell is an immune cell, in particular human immune cells. Pharmaceutical compositions

[0207] According to another embodiment, the present invention provides a pharmaceutical composition comprising as an active ingredient an antibody or therapeutic agent according to the invention. Said compositions may be in any pharmaceutical form suitable for administration to a patient, including but not limited to solutions, suspensions, lyophilized powders for reconstitution with a suitable vehicle or dilution prior to usage, capsules, tablets, sustained-release formulations and the like. The compositions may comprise a therapeutically effective amount of an antibody of the present invention, preferably in purified form, and a pharmaceutical excipient. As used herein, "pharmaceutical excipient" includes solvents, dispersion media, coatings, antibacterial and antifungal agents, isotonic and absorption delaying agents etc. and combinations thereof, which are compatible with pharmaceutical administration. The compositions may also contain other active compounds providing supplemental, additional, or enhanced therapeutic functions. For example, the antibody of the invention may be conjugated to a chemotherapeutic or other agent that is beneficial in treating the disorder to provide targeted therapy. In another embodiment, the composition consists essentially of the antibody or conjugate and one or more pharmaceutical excipients. In another embodiment, the composition consists of the antibody and one or more pharmaceutical excipients.

[0208] Pharmaceutical compositions of the present invention may be manufactured by processes well known in the art, e.g., by means of conventional mixing, dissolving, granulating, grinding, pulverizing, dragee-making, levigating, emulsifying, encapsulating, entrapping or lyophilizing processes. A pharmaceutical composition of the invention is formulated to be compatible with its intended route of administration. Methods to accomplish the administration are known to those of ordinary skill in the art. Examples of suitable excipients and modes for formulating the compositions are described in the latest edition of "Remington's Pharmaceutical Sciences" by E. W. Martin.

[0209] Pharmaceutical compositions according to the invention are typically liquid formulations suitable for injection or infusion. Examples of administration of a pharmaceutical composition include oral ingestion, inhalation, intravenous and continues infusion, intraperitoneal, intramuscular, intracavity, subcutaneous, cutaneous, or transdermal administration. According to certain particular embodiments, the compositions are suitable for intralesional (e.g. intratumoral) administration. In another particular embodiment said compositions are formulated for intravenous administration.

[0210] For example, saline solutions and aqueous dextrose and glycerol solutions can be employed as liquid carriers, particularly for injectable solutions. Suitable pharmaceutical excipients include starch, glucose, lactose, sucrose, gelatin, malt, rice, flour, chalk, silica gel, sodium stearate, glycerol monostearate, talc, sodium chloride, dried skim milk, glycerol, propylene, glycol, water, ethanol and the like.

[0211] Solutions or suspensions used for intravenous administration typically include a carrier such as physiological saline, bacteriostatic water, Cremophor EL™ (BASF, Parsippany, N.J.), ethanol, or polyol. In all cases, the composition must be sterile and fluid for easy syringeability. Proper fluidity can often be obtained using lecithin or surfactants. The composition must also be stable under the conditions of manufacture and storage. Prevention of microorganisms can be achieved with antibacterial and antifungal agents, e.g., parabens, chlorobutanol, phenol, ascorbic acid, thimerosal, etc. In many cases, isotonic agents (sugar), polyalcohols (mannitol and sorbitol), or sodium chloride may be included in the composition. Prolonged absorption of the composition can be accomplished by adding an agent which delays absorption, e.g., aluminum monostearate and gelatin. Where necessary, the composition may also include a local anesthetic such as lignocaine to ease pain at the site of the injection. Generally, the ingredients are supplied either separately or mixed together in unit dosage form, for example, as a dry lyophilized powder or water free concentrate in a hermetically sealed container such as an ampoule or sachette indicating the quantity of active agent. Where the composition is to be administered by infusion, it can be dispensed with an infusion bottle containing sterile pharmaceutical grade water or saline. Where the composition is administered by injection, an ampoule of sterile water for injection or saline can be provided so that the ingredients may be mixed prior to administration.

[0212] Typically and conveniently, antibody formulations in accordance with the invention include intravenous, intratumoral and subcutaneous formulations, provided as solutions or as lyophilized powders to be reconstituted as solutions prior to injection. Common excipients to be used in such formulations include tonicity / osmolality adjusters, buffers (typically 0.005-0.03M or 0.01-0.02M, with pH ranges of 4.8-8.0), surfactants, and / or lyoprotectants. Common buffers include histidine, phosphate, citrate, acetate, succinate, tromethamine, MES, adipic acid, or lactic acid. Viscosity-lowering agents such as arginine (e.g. 5-42 mg / mL), glycine (e.g. 0.1-80 mg / mL), and proline (e.g. 15-25 mg / mL) may be included in high-concentration formulations. Viscositylowering excipients may also contain sodium chloride and lysine.

[0213] In some embodiments, a pharmaceutical composition for injection may comprise an arginine containing buffer, for example an arginine-succinate buffer (e.g. at concentrations of 100-300 mM) or an arginine-citrate buffer. Arginine (conveniently provided in the form of an arginine buffer) may also function to adjust ionic strength and minimize aggregation. For example, arginine-containing formulations for subcutaneous administration do not typically contain sodium chloride nor a sugar or polyol, thus, in those solutions, arginine may function to adjust tonicity and the arginine concentration may be e.g. 0.11M-0.22M. Exemplary tonicity / osmolality adjusters include sodium chloride (e.g. 3-15 mg / mL), sucrose (e.g. 40-160 mg / mL and trehalose (e.g.7.5-150 mg / mL). In a particular embodiment the composition comprises an arginine- succinate buffer (e.g. at concentrations of 100-300 mM).

[0214] In another embodiment the composition may further comprise one or more carbohydrates such as a sugar, sugar derivative or polyol. In a particular embodiment, the carbohydrate is trehalose, provided e,g, at a concentration of 2.5-10%. For example, when trehalose is used alone in solution products, the most common concentration is 60-80 mg / mL and ranges from 40 mg / mL to 104 mg / mL. Lyoprotectants to be used in lyophilized powders may contain for example sucrose or trehalose.

[0215] In another embodiment the composition may contain one or more surfactants. For example, surfactants included in the formulation may inhibit aggregation, and minimize surface adsorption at the air-water interface, the packaging container, and upon dilution into intravenous fluids. Exemplary surfactants include polysorbate 20 (Tween 20, e.g. 0.04-2 mg / mL), polysorbate 80 (Tween 80, e.g. 0.01-2 mg / mL) and poloxamer 188. In some embodiments, the surfactant is used at a concentration above its critical micelle concentration (CMC), e.g. above 0.06 mg / mL for polysorbate 20 and above 0.017 mg / mL for polysorbate 80. In a particular embodiment, the formulation comprises Polysorbate 80, e.g. at 0.01-0.1%. In another embodiment, the composition may have a pH in the range of about 4.8 to about 8.0, e.g. 4.8 to 6.5 or 4.8-5.5.

[0216] In some embodiments, the composition is formulated for injection and comprises an arginine-containing buffer, trehalose and at least one surfactant. In some embodiments, the composition is formulated for injection and comprises 100-300 mM of an arginine- succinate buffer, 2.5-10% trehalose, and 0.01-0.1% polysorbate 80, and has a pH in the range of about 4.08 to about 5.5. According to an exemplary embodiment, an injectable composition in accordance with the invention (e.g. for i.v. administration) may contain 200mM Arginine, 137mM Succinic acid, 5% by weight Trehalose, and by weight 0.05% polysorbate 80, and has a pH of 5.0.

[0217] Oral compositions include an inert diluent or edible carrier. The composition can be enclosed in gelatin or compressed into tablets. For the purpose of oral administration, the antibodies can be incorporated with excipients and placed in tablets, troches, or capsules. Pharmaceutically compatible binding agents or adjuvant materials can be included in the composition. The tablets, troches, and capsules, may optionally contain a binder such as microcrystalline cellulose, gum tragacanth or gelatin; an excipient such as starch or lactose, a disintegrating agent such as alginic acid, Primogel, or corn starch; a lubricant such as magnesium stearate; a glidant such as colloidal silicon dioxide; or a sweetening agent or a flavoring agent.

[0218] The composition may also be administered by a transmucosal or transdermal route. For example, antibodies that comprise an Fc portion may be capable of crossing mucous membranes in the intestine, mouth, or lungs (via Fc receptors). Transmucosal administration can be accomplished through the use of lozenges, nasal sprays, inhalers, or suppositories. Transdermal administration can also be accomplished through the use of a composition containing ointments, salves, gels, or creams known in the art. For transmucosal or transdermal administration, penetrants appropriate to the barrier to be permeated are used. For administration by inhalation, the antibodies are delivered in an aerosol spray from a pressured container or dispenser, which contains a propellant (e.g., liquid or gas) or a nebulizer. The composition can be formulated as a suppository, with traditional binders and carriers such as triglycerides.

[0219] Solutions or suspensions used for intradermal or subcutaneous application typically include at least one of the following components: a sterile diluent such as water, saline solution, fixed oils, polyethylene glycol, glycerin, propylene glycol, or other synthetic solvent; antibacterial agents such as benzyl alcohol or methyl parabens; antioxidants such as ascorbic acid or sodium bisulfite; chelating agents such as ethylenediaminetetraacetic acid (EDTA); buffers such as acetate, citrate, or phosphate; and tonicity agents such as sodium chloride or dextrose. The pH can be adjusted with acids or bases. Such preparations may be enclosed in ampoules, disposable syringes, or multiple dose vials.

[0220] In certain embodiments, the antibodies of this invention are prepared with carriers to protect the antibodies against rapid elimination from the body. Biodegradable polymers (e.g., ethylene vinyl acetate, polyanhydrides, polyglycolic acid, collagen, polyorthoesters, and polylactic acid) are often used. Methods for the preparation of such formulations are known by those skilled in the art. Liposomal suspensions can be used as pharmaceutically acceptable carriers too. The liposomes can be prepared according to established methods known in the art (U.S. Pat. No. 4,522,811).

[0221] In addition, the antibodies of the present invention may be administered in concurrent or sequential combination with various effector molecules such as heterologous polypeptides (including, but not limited to, other antibodies), drugs, radionucleotides, or toxins. In certain embodiments, the antibody is chemically conjugated (i.e. via a stable or labile linker) to said effector molecule. In a particular embodiment, said molecule is a cytotoxic drug, including, but not limited to Calicheamicin, Monomethyl auristatin E (MMAE), Maytansinoid DM1 and Maytansinoid DM4. In other particular embodiments, the antibodies of the invention may be used in combination with additional antibodies. The pharmaceutical compositions may also be included in a container, pack, or dispenser and optionally instructions for administration. For example, the kit may contain instructions for administering the composition to a subject afflicted with or predisposed to cancer, as detailed herein.

[0222] Pharmaceutical compositions suitable for use in context of the present invention include compositions wherein the active ingredients are contained in an amount effective to achieve the intended purpose. All formulations for administration should be in dosages suitable for the chosen route of administration. More specifically, a “therapeutically effective” dose means an amount of a compound effective to prevent, alleviate or ameliorate symptoms of a disease of the subject being treated. Determination of a therapeutically effective amount is well within the capability of those skilled in the art, especially in light of the detailed disclosure and Examples provided herein. According to non-limitative examples, antibodies of the invention may be used in therapeutically effective amounts of 0.01-50 mg / kg body weight, typically 0.1-25 mg / kg. In some embodiment, therapeutically effective amounts of from about 1 mg / kg to about 10, 15 or 20 mg / kg may be administered by injection.

[0223] In certain circumstances, it may be advantageous to formulate compositions in unit dosage form for ease of administration and uniformity of dosage. Unit dosage form as used herein refers to physically discrete units suited for the patient. Each unit dosage contains a predetermined quantity of e.g. an antibody calculated to produce a therapeutic effect in association with the carrier. The unit dosage depends on the characteristics of the agent (e.g. antibodies) and the particular therapeutic effect to be achieved.

[0224] Toxicity and therapeutic efficacy of the compositions described herein can be determined by standard pharmaceutical procedures in cell cultures or experimental animals, e.g., by determining the IC50 (the concentration which provides 50% inhibition), LD50 (the dose lethal to 50% of the population) and the ED50 (the dose therapeutically effective in 50% of the population) and the maximal tolerated dose for a subject compound. The dose ratio between toxic and therapeutic effects is the therapeutic index and it can be expressed as the ratio LD50 / ED50. Antibodies that exhibit large therapeutic indices may be less toxic and / or more therapeutically effective.

[0225] The data obtained from these cell culture assays and animal studies can be used in formulating a range of dosage for use in human. The dosage may vary depending upon the dosage form employed and the route of administration utilized. The exact formulation, route of administration and dosage can be chosen by the individual physician in view of the patient's condition. Depending on the severity and responsiveness of the condition to be treated, dosing can also be a single administration of a slow-release composition, with course of treatment lasting from several days to several weeks or until cure is effected or diminution of the disease state is achieved. The amount of a composition to be administered will, of course, be dependent on the subject being treated, the severity of the affliction, the manner of administration, the judgment of the prescribing physician, and all other relevant factors.

[0226] There is therefore provided, in accordance with an embodiment of the invention, a pharmaceutical or diagnostic composition comprising an antibody that selectively binds to SLAMF6, in particular to human SLAMF6. In an embodiment, the antibody is a monoclonal murine antibody. In an embodiment, the antibody is a monoclonal chimeric antibody. In an embodiment, the antibody is a monoclonal humanized antibody. In an embodiment, the antibody is a monoclonal fully human antibody. In another embodiment, the antibody is an antibody of the invention as described herein.

[0227] In another embodiment, there is provided a kit comprising at least one antibody of the invention (or a molecule comprising at least an antigen-binding fragment thereof), in various embodiments, the kit may comprise means (e.g. reagents) for using the at least one antibody in a method of the invention. In another embodiment the kit comprises instructions for using the at least one antibody in a method of the invention. The kit can further contain one or more additional reagents, such as an immunosuppressive reagent, a cytotoxic agent or a radiotoxic agent. In another embodiment kits for producing multi-dose or single-dose administration units are provided. For example, kits according to the invention may each contain both a first container having a dried protein (e.g. antibody) and a second container having an aqueous diluent, including for example single and multi-chambered pre-filled syringes (e.g., liquid syringes, lyosyringes or needle-free syringes). In another embodiment, the antibody can be labeled with a fluorescent molecule, a spin-labeled molecule, an enzyme, or a radioisotope, and can be provided in the form of kit with all the necessary reagents to perform an immunoassay for SLAMF6. The antibodies can also be used to purify SLAMF6, e.g., by affinity chromatography.

[0228] Therapeutic applications

[0229] According to certain embodiments, the antibodies of the invention may be used in the treatment of various disorders and pathologies, as detailed herein. In another embodiment, an antibody or antigen-binding fragment thereof, or a pharmaceutical composition according to the invention, is for use in therapy or for use as a medicament.

[0230] In one embodiment, the antibodies and compositions of the invention are for use in treating cancer in a subject in need thereof. In another embodiment the antibodies and compositions are used for preventing or delaying the formation of tumor metastasis. In another embodiment said antibodies and compositions are for use in inducing or enhancing anti-tumor immunity.

[0231] In other embodiments, there are provided methods for treating a subject in need thereof comprising administering to a subject in need thereof a therapeutically effective amount of at least one antibody of the invention (or molecule comprising at least an antigen-binding fragment thereof). Typically, the antibody or molecule is administered in the form of a pharmaceutical composition comprising a therapeutically effective amount of at least one antibody or molecule of the invention, and a pharmaceutical excipient. In various embodiments the methods are used for treating cancer in a subject in need thereof, for preventing or delaying the formation of tumor metastasis, or for inducing or enhancing anti-tumor immunity. Each possibility represents a separate embodiment of the invention.

[0232] In one embodiment relating to the compositions and methods of the invention, the subject is afflicted with a tumor. In another embodiment the subject is at risk for developing a tumor (e.g. afflicted with a pre-cancerous lesion or diagnosed with a condition associated with high risk for tumor formation). In another embodiment the subject is at risk for developing tumor metastasis. In another embodiment said subject has been diagnosed with cancer. Advantageously, said subject is a human subject.

[0233] In another embodiment, the cancer is a solid tumor. In various embodiments, the cancer (or tumor) is selected from the group consisting of melanoma, renal cell carcinoma, lung cancer, breast cancer, and head and neck cancer, wherein each possibility represents a separate embodiment of the invention. In other embodiments, the cancer may be e.g. melanoma, urinary tract cancer, gynecological cancer, head and neck carcinoma, primary brain tumor, bladder cancer, liver cancer, lung cancer, breast cancer, ovarian cancer, prostate cancer, cervical cancer, colon cancer and other cancers of the intestinal tract, bone malignancies, connective and soft tissue tumors, or skin cancers. In a particular embodiment, said cancer is melanoma. Additional solid tumors to be treated by antibodies of the invention are non-small cell lung carcinoma, uterine and cervical carcinoma and squamous cell cancer of head and neck, wherein each possibility represents a separate embodiment of the invention. In another embodiment the tumor is selected from the group consisting of melanoma, renal cell carcinoma, lung carcinoma, breast carcinoma, head and neck carcinoma, non-small cell lung carcinoma, uterine and cervical carcinoma and squamous cell cancer of head and neck. In a particular embodiment, said cancer is breast cancer, including e.g. breast carcinoma, breast adenocarcinoma, triple negative breast cancer (TNBC), and hormone receptor-positive breast cancer. Each possibility represents a separate embodiment of the invention. In another embodiment said cancer or tumor is hematopoietic. In another embodiment the subject is afflicted with a hematopoietic malignancy. Exemplary hematological malignancies to be treated by antibodies of the invention include, without limitation, multiple myeloma, B cell lymphoma, and plasma cell leukemia, wherein each possibility represents a separate embodiment of the invention.

[0234] In another embodiment the tumor is a sloid tumor. In another embodiment said tumor is a SLAMF6-expressing tumor. In yet another embodiment said tumor is a SLAMF6 non-expressing tumor. In another embodiment the tumor is a metastatic tumor. In another embodiment said tumor is a treatment-resistant tumor. In another embodiment said tumor is resistant to treatment with at least one anti-cancer therapy selected from the group consisting of chemotherapy, radiotherapy and immunotherapy. In another embodiment said tumor is resistant to treatment with immune checkpoint inhibitors, e.g. directed to PD-1, PD-E1, CTEA-4, EAG3, TIGIT or combinations thereof. In another embodiment said tumor is resistant to adoptive cell therapies (ACT).

[0235] In another embodiment said tumor contains dense immune cell infiltrate around or within tumor cell clusters. In another embodiment said tumor contains SEAMF6-expressing immune cell infiltrates (including immune cells of lymphoid and / or myeloid origin). Thus, in some embodiments, the methods of the invention may include a step of evaluating SEAMF6 expression in a sample of the tumor, for example evaluating if a solid tumor comprises SEAMF6-expressing immune cell infiltrates. According to these embodiments, the methods of the invention may include a step of evaluating SEAMF6 expression in a sample of the tumor, wherein enhanced SEAMF6 expression compared to a control (non-malignant) sample indicates that the tumor is amenable for treatment by antibodies of the invention. In yet another embodiment, said tumor is devoid of immune cell infiltrates. Each possibility represents a separate embodiment of the invention.

[0236] In another embodiment the subject is afflicted with cytopenia. In another embodiment the subject is at risk for developing cytopenia. In another embodiment the subject is afflicted with lymphocytopenia. In another embodiment the subject is at risk for developing lymphocytopenia.

[0237] In another embodiment the treatment does not substantially include induction of drug- induced toxicity, antibody-dependent cellular cytotoxicity (ADCC) and / or complementdependent cytotoxicity (CDC), wherein each possibility represents a separate embodiment of the invention. In another embodiment said treatment does not substantially include induction of any one of drug-induced toxicity, ADCC and CDC. In another embodiment said subject is afflicted with a tumor not amenable for induction of drug-induced toxicity, ADCC and / or CDC. In another embodiment, the antibodies of the invention are for use in the preparation of cell compositions that may be used in immunotherapeutic regimens, such as those suitable for adoptive transfer into a recipient subject in need thereof. As used herein, and unless otherwise specified, the term "adoptive transfer" refers to a form of passive immunotherapy where previously sensitized immunologic agents (e.g., cells or serum) are transferred to the recipients. The phrases “adoptive transfer immunotherapy”, “adoptive cell therapy” and “adoptive cell immunotherapy” are used interchangeably herein to denote a therapeutic or prophylactic regimen or modality, in which effector immunocompetent cells, such as T cell compositions as disclosed herein, are administered (adoptively transferred) to a subject in need thereof, to alleviate or ameliorate the development or symptoms of cancer or infectious diseases.

[0238] For example, compositions for adoptive cell transfer may be prepared by methods including activating a T cell population by a TCR stimulation, and expansion of the cells to obtain a therapeutically effective amount of effector T cells for administration. Such methods include but are not limited to, Rapid Expansion Protocols (REP). According to embodiments of the invention, the activation and / or expansion steps may be performed in the presence of one or mor antibodies of the invention.

[0239] In various embodiments, the TCR stimulation may be antigen non-specific (performed, for example, using antibodies specific to CD3 that activate the receptor upon binding, e.g. 0KT3 or SP34) or antigen- specific (using suitable antigen presenting cells and antigen). In the context of cancer treatment, antigen- specific stimulation typically employs stimulation to tumor- associated antigens. The term “tumor-associated antigen” (TAA) refers to any protein, peptide or antigen associated with (carried by, expressed by, produced by, secreted by, etc.) a tumor or tumor cell(s). Tumor-associated antigens may be (nearly) exclusively associated with a tumor or tumor cell(s) and not with healthy normal cells or may be over expressed (e.g., 2 times, 5 times, 10 times, 50 times, 100 times, 1000 times or more) in a tumor tissue or tumor cell(s) compared to healthy normal tissue or cells. More particularly, a TAA is an antigen capable of being presented (in processed form) by MHC determinants of the tumor cell. Hence, tumor-associated antigens are likely to be associated only with tumors or tumor cells expressing MHC molecules. Non-limitative examples of well-known TAA are MART-1, gplOO 209-217, gplOO 154-163, CSPG4, NY-ESO, MAGE-A1, Tyrosinase.

[0240] In some embodiments, one commonly used approach for stimulating proliferation, in particular of CD8+T cells, is the incubation of T cells with soluble anti-CD3 antibody in the presence of Fc receptor-bearing accessory cells (feeder cells), an approach designated the REP. Antibody "presented" to T cells in this manner generates a more effective proliferative signal than soluble anti-CD3 alone or anti-CD3 immobilized on a plastic surface. In the treatment of cancer, adoptive cell therapy typically involves collecting T cells that are found within the tumor of the patient (referred to as tumor-infiltrating lymphocytes, TIL), which are encouraged to multiply ex vivo using high concentrations of IL-2, anti-CD3 and allo-reactive feeder cells. These T cells are then transferred back into the patient along with exogenous administration of IL-2 to further boost their anti-cancer activity.

[0241] Thus, according to certain additionally advantageous embodiments, activation and / or expansion (e.g. as part of a REP protocol) is performed in the presence of feeder cells. The term “feeder cells” generally refers to cells of one type that are co-cultured with cells of a second type, to provide an environment in which the cells of the second type can be maintained and proliferated. For the purpose of the present invention, this term specifically refers to Fc receptorbearing accessory cells, which are typically allo-reactive with the T cell containing population to be propagated. In other words, the feeder cells need not be histocompatible with the T-cell containing population to be propagated, and in certain advantageous embodiments the two populations typically HLA-mismatched. A typical example of feeder cells used in embodiments of the invention is allogeneic normal donor peripheral blood mononuclear cells, PBMC. Typically and advantageously, the use of such feeder cells is performed in conjunction with antigen nonspecific TCR stimulation, e.g. by incubation with antigen non-specific stimulating antibodies, as detailed herein.

[0242] In another embodiment, adoptive transfer T cell compositions are prepared with irradiated PBMC (incapable of proliferation) as feeder cells. For example, PBMC may conveniently be attenuated by irradiation by exposing the cells to 7000RAD. In another embodiment, adoptive transfer T cell compositions are prepared with artificial antigen presenting entities including antigen presenting cells and inert particles carrying antigens, to provide antigen- specific stimulation.

[0243] In another embodiment, ACT compositions in accordance with the invention encompass engineered ACT compositions. For example, without limitation, a population of lymphocytes (e.g. T cells or NK cells) may be genetically engineered (e.g. transduced or transfected) to express a tumor- specific receptor such as a TCR or a chimeric antigen receptor (CAR) directed to a TA A, and expanded to produce an ACT composition.

[0244] In another embodiment the antibodies of the invention are used for modulating the activity of a SLAMF6-expressing cell. In another embodiment the modulation is performed in vitro. In another embodiment modulation is performed ex vivo. In another embodiment the SLAMF6- expressing cell is a lymphocyte. In another embodiment the SLAMF6-expressing cell is a cytotoxic effector cell. In another embodiment the SLAMF6-expressing cell is a T cell. In another embodiment the SLAMF6-expressing cell is a natural killer (NK) cell. In another embodiment modulation is performed in vivo. In various embodiments, modulation comprises inducing or enhancing T cell activity selected from the group consisting of activation, proliferation, cytokine secretion, cytotoxic activity and combinations thereof. In another embodiment said activity is a tumor-induced activity. In another embodiment modulation comprises inhibition of T-cell exhaustion. In another embodiment said activity is a direct cell-mediated cytotoxic activity (e.g. by T cells and / or NK cells). Each possibility represents a separate embodiment of the invention. In another embodiment, said antibody is used to induce or enhance the direct cell-mediated cytotoxicity of primary human lymphocytes under conditions insufficient for substantially inducing or enhancing proliferation of said lymphocytes.

[0245] In another embodiment the antibodies of the invention are used for detecting a SLAMF6- expressing cell. In another embodiment the antibodies of the invention are used for detecting the presence of SLAMF6 in a biological sample. In some embodiments, methods for detecting or quantifying the presence of SLAMF6 in a sample comprise the steps of:

[0246] (i) incubating the sample with the antibody or molecule of claim 1, under conditions enabling the formation of an antigen-antibody complex; and

[0247] (ii) detecting or quantifying the antigen-antibody complex.

[0248] In one embodiment, the sample is a biological sample. The term “biological sample” as used herein refers to a sample of tissue or fluid isolated from a subject such as, but not limited to, blood, plasma, platelets, serum, fecal matter, urine, bone marrow, bile, spinal fluid, lymph fluid, cerebrospinal fluid, samples of the skin, secretions of the skin, respiratory, intestinal, and genitourinary tracts, tears, saliva, milk, blood cells, organs, biopsies and also samples of in vitro or ex vivo cell culture constituents, including, but not limited to, conditioned media resulting from the growth of cells and tissues in culture medium, e.g., recombinant cells, as well as cells and cell components. The samples detailed above need not necessarily be in the form obtained directly from the source. For example, the sample can be treated prior to use, such as, for example, by heating, centrifuging, etc. prior to analysis.

[0249] In various embodiments, detecting or quantifying the presence of SLAMF6 in the sample may conveniently be performed using well known immunoassays including, but not limited to: ELISA (including various multiplexed ELISA technologies), dipstick, antibody arrays and chips, lateral flow tests and the like. Such assays and methods enable detection and / or quantification of formed antigen-antibody complexes and may be employed using various available protocols. Non-limiting examples of the use of immunoassays to detect or quantify the presence of SLAMF6 in a sample are presented in the Examples section below.

[0250] The following examples are presented in order to more fully illustrate some embodiments of the invention. They should, in no way be construed, however, as limiting the broad scope of the invention.

[0251] EXAMPLES

[0252] Example 1. Generation of murine monoclonal antibodies directed to SLAMF6

[0253] A recombinant polypeptide comprising the human SLAMF6 (hSLAMF6) ectodomain fused at its C to a histidine tag (herein denoted SLAMF6-ECD-6 HIS) was synthesized and purified. The polypeptide precursor had the following amino acid sequence (in which the signal peptide is underlined, and the histidine tag is in bold:

[0254] MLWLFQSLLFVFCFGPGNVVSQS SLTPLMVNGILGESVTLPLEFPAGEKVNF I TWLFNETSLAF IVPHETKSPE IHVTNPKQGKRLNFTQSYSLQLSNLKMEDTGSYRAQI STKTSAKLS SYTLRILR QLRNIQVTNHSQLFQNMTCELHLTCSVEDADDNVSFRWEALGNTLS SQPNLTVSWDPRI S SEQD YTCIAENAVSNLSFSVSAQKLCEDVKIQYTDTKMHHHHHH (SEQ ID NO: 130).

[0255] SJL and BLAB / c mice were immunized with the recombinant polypeptide. Following immunization, test bleeds were analyzed for binding of the hSLAMF6 ectodomain, and of cell surface-expressed SLAMF6 using ELISA and flow cytometry, respectively. In addition, the antibodies were analyzed for binding to surface expressed cynomolgus monkey SLAMF6 by flow cytometry. For the binding assay, a recombinant cynomolgus monkey SLAMF6 protein containing a 3HA tag (herein denoted cynoSLAMF6, SEQ ID NO: 131), was used. The sequence of the cynoSLAMF6 precursor is provided below (in which the signal peptide is underlined and the 3HA tag is in bold):

[0256] MLWLFQSLLFVFCFGPGNLYP YDVPDYAYP YDVPDYAYP YDVPDYAVS Q S S S TP LMVNGVLGE S VILPLELSAGEMIAS I TWLCNGTSLAF IEP SETKSPNIRVTHPKQRKRLNFTQSYSLKLSNLEM EDTGSYSAQI TTETSVKLS SYTLRIFRQLRS IQVNNYSQLFQNRTCE IHLTCSVEDADDNVSFR WEALGS ILS SEPNI TTSWDPRI SGEQDYTCIAENAVSNLSFSVSAQKLCGDVKIQYTDTKMILF VVFGICIVTGF I IMLLLVLRKRRGRFSTFVYSANTGPCRACGEHRVCFSLS SEQHCVCFSHSFK QGNGNLDTYEKCYCHNLLHS (SEQ ID NO: 131).

[0257] The results are presented in Figures 1A (recombinant hSLAMF6 binding by ELISA), IB (binding to hSLAMF6-expressing CHOK1 cells by FACS) and 1C (binding to cynoSLAMF6- expressing CHOK1 cells by FACS). In Figure IB, black columns indicate sera dilution of 1:100, white columns indicate sera dilution of 1:1000, mlgGl indicates murine isotype control; secondary antibody was Alexa Fluor® 488 donkey anti-mouse IgG (H+L) antibody. Control antibodies for cynoSLAMF6 flow cytometry included sheep anti-monkey SLAMF6 antibody ("ctrl Ab#3") and its isotype control (sheep IgG), as indicated in Figure 1C. Secondary antibody was Alexa Fluor® 488 donkey anti-mouse IgG (H+L) antibody.

[0258] As can be seen, repeated test bleeds revealed high titer of anti-hSLAMF6 antibodies in the immunized mice. Results also revealed anti-cynoSLAMF6 reactivity in several mice, wherein the proportion of sera highly reactive to both SLAMF6 polypeptides was higher in SJL mice than in BLAB / c mice. Mice demonstrating high serum reactivity to both hSLAMF6 and cynoSLAMF6 were selected for hybridoma production.

[0259] In addition, two more groups of mice, each immunized with a different KLH-conjugated peptide derived from the auto-dimerization domain of human SLAMF6, were included, and test bleeds were analyzed as described above. Based on the analyses performed in the three groups of immunized nice, splenocytes of the first group (immunized with SLAMF6-ECD-6 HIS), which showed superior results over the other two groups, were used for hybridoma production.

[0260] To this end, spleens of selected mice were harvested, and B cells were fused with myeloma cells to create hybridoma cells. Hybridomas were screened, subcloned, and screened again using binding assays as described above for mice test bleeds and functional assays (presented in Example 2). The results are presented in Figures 2 (binding to hSLAMF6-expressing Jurkat cells by FACS) and 3 (binding to cynoSLAMF6-expressing CHOK1 cells by FACS).

[0261] Figure 2 shows exemplary sub-clones that were selected for further characterization of antibody binding to naturally expressed human SLAMF6 on the Jurkat T cell line. Figure 3 shows an example of two of the anti-SLAMF6 antibodies developed that are able to recognize and bind cynoSLAMF6-expressing cells. Notably, the reference anti SLAMF6 antibody (a known humanized anti-human SLAMF6 antibody) did not show cynoSLAMF6 binding.

[0262] In summary, several clones of monoclonal antibodies were generated and characterized as having various levels of affinity to human and cynomolgus SLAMF6.

[0263] Example 2. Functional assays reveal unexpected efficacy and superiority over known anti-SLAMF6 antibodies

[0264] Selected clones identified in the binding assays were also screened using in-vitro functional assays. For this purpose, Jurkat T cells were activated for 24h with plate-bound anti- CD3, in the presence of the anti-SLAMF6 antibodies or control antibodies. Then culture supernatants were collected, and Granzyme B secretion was evaluated using ELISA. The results are presented in Figures 4A and 4B (each depicting a subset of the tested antibodies, as indicated in the Figures). mlgGl indicates isotype control antibodies (mouse IgGl anti-human SLAMF6).

[0265] As can be seen, several clones were able to induce secretion of high levels of the cytotoxicity mediator Granzyme B from Jurkat cells, including, for example, antibody clones Ab04, Ab02, Abl l, Ab20, Ab07 and Ab 19.

[0266] Additional functional assays were performed to further characterize and select the best candidate antibody for development. In particular, the ability of the antibodies to induce or enhance cytotoxicity in primary human lymphocytes was evaluated. Figures 5A and 5B show the CD107 / CD8 positive cells obtained from two healthy donor PBMC populations undergoing three repeated activations with anti-CD3 and the selected anti-SLAMF6 antibodies in the course of 7 days. As controls, known anti-hSLAMF6 antibodies, designated "ctrl Ab#l" (humanized antihuman SLAMF6 IgGl antibody) and its isotype control (hlgGl), and "ctrl Ab#2" (commercial mouse-anti-human SLAMF6) were used, as well as antibodies against human PD-1 or LAG3, and their corresponding isotype controls. In the Figures 5A-5B and the following figures, "no t" indicates cells with no added antibody treatment.

[0267] The results demonstrate an increase in the CD8+population expressing the cytotoxic degranulation marker CD 107 following activation with the selected antibodies (for example, mAb clones Ab02, Ab04, Ab07 and Abl9). As can be seen in Figures 5A and 5B, the results also show marked and unexpected functional superiority of the selected antibodies over the reference anti- SLAMF6 antibodies. In particular, mAb clones Ab02, Ab04, Ab07 and Abl9 exhibited an exceptional ability to improve T cell cytotoxicity, and superiority over known antibody Ab#l. Notably, commercial antibody Ab#2 did not significantly affect the cytotoxic capacity of the cells.

[0268] Cell culture supernatants from the activated T cells were collected, and Granzyme B secretion levels by the T cells were detected by ELISA. The results for the two tested donors (corresponding to those tested in Figures 5A and 5B) are shown in Figures 6A and 6B, respectively. As can be seen, Granzyme B levels following activation with the anti-CD3 antibody in combination with the selected test antibodies were increased. The results show unexpected functional superiority of the selected test antibodies over the reference antibodies. In particular, mAb clones Ab02, Ab04 and Ab07 demonstrated an exceptional increase in T cell cytotoxicity as evaluated by Granzyme B secretion, and superiority over Ab#l, which was apparent in both donors for Ab07; Ab02, Ab04, Ab07 and Ab 19 exhibited superiority over Ab#2.

[0269] Next, tumor infiltrating lymphocytes (TILs) extracted from tumors of melanoma patients were activated for 48h with the anti-CD3 antibody and the four selected test antibodies (clones Ab02, Ab04, Ab07 and Ab 19) or control antibodies, followed by an additional 24h co- culture with cognate melanoma cells. Supernatants were collected and the secretion of Granzyme B was evaluated using ELISA. Figures 7A and 7B show the results obtained in TIL 412 and 431, respectively. As can be seen, Granzyme B levels were augmented following activation with the anti SLAMF6 antibodies. Additionally, significant superiority over the reference antibody Ab#l was revealed in both TILs. Significant superiority was also observed over reference antibody Ab#2 in TIL 412 (without wishing to be bound by a specific theory or mechanism of action, that could be attributed to patient variability).

[0270] An additional experiment with TIL, evaluating melanoma tumor killing, was performed. Figure 8 demonstrates a significantly enhanced killing capacity of TILs activated with an anti- CD3 antibody in combination with the anti SLAMF6 antibody Ab 19, exceeding even the ability of the potent co-stimulator anti-CD28 antibody to enhance tumor cell killing. Notably, the known reference antibody Ab#l (used as a control), as well as other antibodies directed to checkpoint molecules PD-1 and LAG-3, did not exert a significant effect in this system.

[0271] In summary, the results presented above indicate an unexpected efficacy of several antibody clones, including in particular clones Ab02, Ab04, Ab07 and Ab 19, in enhancing antitumor immunity. The results further show significant functional superiority of several antibody clones, including in particular clones Ab02, Ab04, Ab07 and Ab 19, over known anti-SLAMF6 antibodies.

[0272] Example 3. Antibody sequences

[0273] The sequences of the 23 subclones of mouse anti SLAMF6 mAbs chosen for further characterization were obtained and are provided in Table 28 below. The CDRs (determined using the Kabat numbering system) are marked with an underline, and the type (isotype) of the heavy chain and light chain are indicated.

[0274] Table 28 - Sequences of mouse anti human SLAMF6 mAb subclones

[0275] The sequencing analysis revealed that some of the antibody clones had identical variable region sequences. Specifically, Ab 11 was determined to have the same VH and VL sequences as Ab02, Ab22 was determined to have the same VH and VL sequences as Abl5, and Abl4 was determined to have the same VH and VL sequences as Ab 10.

[0276] Example 4. Binding properties

[0277] Ten mouse anti-human SLAMF6 antibodies were selected, based on the results of the functional assays described herein, for kinetic (Biacore) analysis of their interaction with the recombinant human SLAMF6 ectodomain, and the results are presented in Table 29. The kinetics model used in the assay was 1:1 binding, and the analyte solution contained the Human SLAMF6 ECD-6his polypeptide. For the capture solution, 2 pg / ml of the indicated test antibody or control antibody were used.

[0278] As can be seen, Table 29 shows KD values ranging from LOlx10-07M to 4.85x10-10M for selected antibodies, with subclones Ab04, Ab013, Ab016 and Ab019 exhibiting particularly low KD values (in the range of about IO'09- IO'10M). Notably, the binding affinity of the Ab04 subclone was significantly higher than the control anti-SLAMF6 antibody (ctrl Ab#l). As can further be seen, several mAb clones including for example Ab02, Ab07, Ab08, Ab 14 and Ab20 exhibited moderately low KD values (within the range of about IO'07- 10'8M). Further, several antibodies, notably including Ab07 and Ab019, exhibited KD within the range of 9x10-08M to Ix10-9M.

[0279] Table 29 - Affinity analysis by Biacore - mAb subclones

[0280] An epitope binning assay was performed by competitive FACS for the ten selected antibodies listed in Table 29 and the reference antibody Ctrl Ab#l. The grouping criteria were set for an inhibition rate between antibodies that exceeded 80%. Epitope binning results showed that the eleven tested anti-hSLAMF6 antibodies (including the control Ab#l) were divided into four bins. In particular, Ab02, Ab 14, Ab08, and Ab20 were identified as belonging to epitope bin 1; Ctrl Ab#l was identified as belonging to epitope bin 2; Ab 12 was identified as belonging to epitope bin 3; and Ab 16, Ab04, Ab 19 and Ab 13 were identified as belonging to epitope bin 4. Epitope bins 1 and 2 were found to be partly overlapping, with Ab07 identified as being belonging to both epitope bins.

[0281] In summary, antibody clones were subjected to affinity and epitope characterization. From comparing the results in Examples 1-2 and 4, it is apparent that the affinities of the antibodies to human SLAMF6 were not necessarily correlated with their capacity to modulate T cell activity, with several antibody clones exhibiting moderately high binding affinities while exerting exceptionally high capacity to enhance primary T cell cytotoxicity.

[0282] Example 5. Generation and characterization of chimeric antibodies

[0283] Based on the experiments described in Examples 1-3 above, four antibodies were chosen for chimeric antibody design, namely clones Ab02, Ab04, Ab07 and Ab 19 as presented above. All antibodies were generated as IgG4, using a modified human IgG4 containing a S228P mutation (SEQ ID NO: 142). Ab04 was also generated as IgGl in order to evaluate and compare functional attributes to the Fc isotype. Chimeric antibodies were engineered, produced and purified. Briefly, mouse constant regions (Fc) were replaced with human constant regions as described above, while retaining the mouse variable regions. To this end, DNA sequences of the variable region genes (VH and VL) of the mouse antibody and the constant region genes (CH and CL) of the human antibody’s heavy (IgG) and light chains were cloned. A chimeric antibody gene was constructed to combine the mouse variable region genes with human constant region genes. The chimeric antibody genes were introduced the into the ExpiCHO expression system. Following expression, the chimeric antibodies were purified from the cell culture supernatant using affinity chromatography.

[0284] Biacore analysis of the resulting antibodies, designated cmAbO2-IgG4, cmAbO4-IgG4, cmAbO4-IgGl, cmA007-IgG4 and cmAbl9-IgG4, was performed essentially as described in Example 4 above, and the results are presented in Table 30. The kinetics model used in the assays was 1:1 binding, and the analyte solution contained the human SLAMF6 ECD-6His polypeptide. As can be seen in Table 30, the resulting chimeric antibodies exhibited remarkably low KD values, similar to those obtained for their corresponding mAb clones.

[0285] Table 30 - Affinity analysis by Biacore - chimeric Abs

[0286] The chimeric antibodies were further evaluated for binding to Jurkat cells by flow cytometry, and the results are presented in Figure 9. All antibodies showed binding to Jurkat cells. EC50 values were determined for each antibody and the results are presented in Table 31. Additionally, the chimeric antibodies cmAbO4 (IgG4 and IgGl isotypes) and cmAbl9 were evaluated for their ability to bind CHOK1 cells expressing cynoSLAMF6. As can be seen in Figure 10, the tested chimeric antibodies were able to bind the cynoSLAMF6-expressing cells. The secondary antibody used for the flow cytometry experiments depicted in Figures 9-10, as well as those further described below and depicted in Figures 12-13 and 16, was Alexa Fluor® 488 goat anti-human IgG(H+E).

[0287] Table 31 - Chimeric antibodies binding to Jurkat cells

[0288] Next, an in-vitro functional assay (Granzyme B secretion) was performed on selected chimeric antibodies, essentially as described in Example 2. The results are presented in Figure 11. As can be seen, Jurkat cells activated with chimeric anti SLAMF6 antibodies, and in particular cmAbO7 and cmAbO2 as well as cmAbl9 (in the context of modified human IgG4 Fc) exhibited enhanced Granzyme B secretion.

[0289] Example 6. Generation and characterization of humanized antibodies

[0290] Based on the in-vitro results obtained from antibody characterization and functional assays, two out of four chimeric antibodies, namely cmAbO7 and cmAbl9, were selected for further modification and humanization. To this end, the chimeric antibodies were sequenced, and the resulting sequences were further modified to generate a series of antibodies derived from each original chimeric antibody clone.

[0291] The selected human constant regions for generating the antibodies were of the IgGl isotype, in which a EAEA mutation was generated at the Fc domain (SEQ ID NO: 141). The resulting antibodies thus exhibited elimination or significant downregulation of the ability of their Fc domain to bind Fc gamma receptors (FcyR). Accordingly, without wishing to be bound by a specific theory or mechanism of action, unwanted inflammatory responses such as ADC or ADCC may be avoided. Initially, second-generation chimeric antibody clones containing various hotspot alternatives were developed, and their variable region sequences are presented in Tables 32 and 33 below (in which the CDRs are underlined, and hot spot alternatives are marked in bold). In particular, each chimeric antibody listed in Table 32, namely AbO7-VH(NG_GG), AbO7-VH(NG_sG) and AbO7-VH(NG. NA), includes the original AbO7-VE, and its corresponding modified VH; the sequence of the original AbO7-VH is shown for comparison. In addition, each chimeric antibody listed in Table 33, namely AbO19-VE(DG_sG), AbO19-VE(DG_DA) and AbO19-VE(DG_GG), includes the original AbO19-VH, and its corresponding modified VE; the sequence of the original Ab019- VL is shown for comparison. As may be further appreciated, the CDRHI marked in Tables 32 and 33 were determined using the Chothia numbering system (in addition to the Kabat numbering system), and are thus distinct from those listed in Table 28 determined using the Kabat numbering system. The antibodies are subjected to binding and functional assays as described above. Table 32 - Variable regions of modified chimeric antibodies derived from Ab07

[0292] Table 33 - Variable regions of modified chimeric antibodies derived from Ab 19

[0293] The modified chimeric antibodies were then subjected to various functional assays, and the results are presented in Figures 12-15.

[0294] Figure 12 depicts Jurkat FACS binding of chimeric anti-SLAMF6 antibodies designed with hotspot removal alternatives, with variable regions as described in Tables 32 and 33 and LALA-modified IgGl constant regions as described above. hlgG(LALA) (also identified in subsequent figures as "IgGl(LALA)") represents isotype control containing the modified Fc IgGl used in the chimeric and humanized antibodies. For the chimeric humanized antibodies derived from Ab07, three variants (designated in the Figures cmAbO7-VH(NG_GG), cmAbO7-VH(NG_sG) and cmAbO7-VH(NG_NA)) and their parental chimeric antibody (designated "cmAbO7_IgGl(LALA)" in the figures) showed similar binding affinities to Jurkat cells. For Ab019-derived chimeric antibodies, cmAbO19-VL(DG_DA) and its parental antibody (designated "cmAbO19_IgGl(LALA)" in the figures) showed similar binding affinity to Jurkat cells. . These findings suggest that the hotspot removal modifications to the cmAbO7_IgGl(LALA) and the DG_DA modification to cmAbO19_IgGl(LALA) retained the binding affinity of the chimeric antibodies to Jurkat cells, indicating preserved functionality in these variants.

[0295] Figure 13 depicts CHO-cyno SLAMF6 FACS binding of chimeric anti SLAMF6 antibodies designed with hotspot removal alternatives as described above. cmAbO19-VL(DG_DA) and its parental antibody cmAbO19_IgGl(LALA) showed similar binding affinities to cynoSLAMF6. cmAbO19-VL(DG_ SG) and cmAbO19-VL(DG_GG) showed lower binding with cynoSLAMF6. These results suggest that while some variants, like cmAbO19-VL(DG_DA), maintain similar binding affinity to cynoSLAMF6 as the parental antibody, others, such as cmAbO19-VL(DG_SG) and cmAbO19-VL(DG_GG), exhibit reduced binding, highlighting the influence of hotspot modifications on antibody-target interaction.

[0296] Figures 14A-14B show the results of a functional assay of activation-induced Granzyme B secretion measured by ELISA. PBMCs from two healthy donors A and B (Figures 14A and 14B, respectively) were activated for 48 hours with plate-bound anti-CD3 (0.1 g / ml) and chimeric anti-SLAMF6 antibodies (with hotspot removal alternatives derived from Ab07 as described above) or control IgGl(LALA) (2.5pg / ml). After 48 hours supernatants were collected for Granzyme B ELISA.

[0297] Figures 15A-15C show the results of additional functional assays with chimeric antibodies derived from Ab07 with hotspot removal alternatives as described above. PBMCs from a healthy donor were activated for 48 hours with plate-bound anti-CD3 (0.1 pg / ml) and chimeric anti-SLAMF6 antibodies or control IgGl (2.5pg / ml). After 48 hours supernatants were collected for Granzyme B (Figure 15A) and IFN-y (Figure 15B) ELISA. Cells were collected for flow cytometry to evaluate the percent of CD107+ / CD8+ expressing cells (Figure 15C). "No t" indicates no activation. The results indicate that all the antibody variants with tested modifications retain the functional attributes of the parental antibody.

[0298] Additional functional analyses of the chimeric humanized AbO7-VH(NG_GG) antibody were performed, as follows. PBMCs from two healthy donors were activated for 6 hours with platebound anti-CD3 and AbO7-VH(NG_GG) (designated in the figures "cmAbO7-VH(NG_GG)"), or control antibodies. Brefeldin A was added to the culture to allow intracellular labeling of TNF-a and IFN-y. Anti CD107a Ab was added at the beginning of the culture. Control groups included anti-CD3 in combination with the isotype control antibody (aCD3+IgGl(LALA)), anti-CD3 activation alone (aCD3) and non-activated cells (no t). Figure 16 shows a summary of the percentile of CD107a, IFN-y and TNF-a-positive CD8+cells obtained in two healthy donor PBMC.

[0299] The results in Figure 16 demonstrate an increase in the proportion of the CD8+population expressing the cytotoxic de-granulation marker CD107a, and the proinflammatory cytokines IFN- y and TNF-a following activation with AbO7-VH(NG_GG). As can be seen, the humanized anti- SLAMF6 antibody enhanced the generation of cytokines and cytotoxic mediators at early time points following activation with anti CD3. Thus, antibodies in accordance with the invention exhibit immunomodulatory functions during various stages of cell culture, apparent from several hours up to several days in culture. The results also show that antibodies in accordance with the invention are effective even in modulating the activity of non-exhausted lymphocytes. Without wishing to be bound by a specific theory or mechanism of action, antibodies of the invention may exhibit enhanced modulatory activity with enhanced cell density, thereby revealing a potential for rheostatic regulation by SLAMF6 modulation.

[0300] Further to the results of the modified chimeric antibodies, full humanization of certain antibodies was effected by CDR grafting with sequences derived from the Ab07 lineage. In particular, CDRs of AbO7-VH(NG_GG) and AbO7-VL were used. In-silico analyses were performed to select human variable region sequences for grafting the CDRs. IGHV1-69*O2 was selected as the germline for VH CDR grafting based on in-silico analyses considering framework homology, VH germline usage rate in therapeutic mAbs, and distribution of the VH gene in natural human antibody repertoire. The IGHV1-69*O2 VH sequence is as follows:

[0301] QVQLVQSGAEVKKPGSSVKVSCKASGGTFSSYTISWVRQAPGQGLEWMGRIIPILGIANYAQKFQGRVTITAD KSTSTAYMELSSLRSEDTAVYYCASWGQGTTVTVSS (SEQ ID NO: 132).

[0302] IGKV2-30*01 was selected as the germline for VK CDR grafting based on in-silico analyses that considered homology, VK germline usage rate, and distribution of VK gene in natural human antibody repertoire. The IGKV2-30*01 VL sequence is as follows: DVVMTQSPLSLPVTLGQPASISCRSSQSLVYSDGNTYLNWFQQRPGQSPRRLIYKVSNRDSGVPDRFSGSGS GTDFTLKISRVEAEDVGVYYCMQGTHWPFGGGTKVEI K (SEQ ID NO: 133).

[0303] Variable region sequences of the resulting humanized antibodies are listed in Table 34, in which the CDRs are underlined. Table 34 - Variable regions of humanized antibodies derived from Ab07

[0304] Table 35 describes the designations of the humanized antibody variants produced. Using a combination of VH and VL variants, 12 humanized antibodies were produced in CHO-1 cells. Table 35 - Designation of humanized antibodies derived from Ab07

[0305] Figure 17 shows FACS binding of humanized anti-SLAMF6 antibodies to Jurkat cells, as compared to the parental chimeric antibody cmAbO7-VH(NG_GG) or isotype control hlgGl(LALA). As can be seen, Hu007-01 (BMO), Hu007-02 (BM2), Hu007-03 (BM4) and Hu007-04 (BM6) did not exhibit considerable binding to Jurkat cells, whereas the other antibodies could bind to Jurkat cells under physiological conditions. Accordingly, and without wishing to be bound by a specific theory or mechanism of action, the leucine residue at position 41 of the light chain may be involved in the interaction with the antigen, and is advantageously retained in antibodies showing physiologically-compatible binding to endogenous surface-expressed hSLAMF6 on human lymphocytes.

[0306] An in-vitro functional assay (Granzyme B secretion by Jurkat T cell line) was performed using humanized antibodies Hu007-05 (BM1), Hu007-06 (BM3), Hu007-07 (BM5), Hu007-08 (BM7), Hu007-09 (BM2), Hu007-10 (BM4), Hu007-l l (BM6) and Hu007-12 (BM8) essentially as described in Example 2. Briefly, Jurkat cells were activated for 24h with plate-bound anti-CD3 (0.125pg / ml), in the presence of the anti-SLAMF6 antibodies or control antibodies (Ab07- VH(NG_GG) or isotype control). Then culture supernatants were collected and Granzyme B secretion was evaluated using ELISA. The results are presented in Figures 18A (secreted granzyme B in pg / ml) and 18B (fold increase in Granzyme B secretion calculated as fold increase over average Granzyme B of Max Isotype IgG).

[0307] The results demonstrate that all eight humanized antibodies are capable of enhancing the release of Granzyme B in a concentration-dependent manner (antibody concentration ranging from 5 pg / ml to 0.039 pg / ml). Antibodies Hu007-05 (BM1), Hu007-08 (BM7), Hu007-09 (BM2) and Hu007-12 (BM8) showed superior capacity to enhance Granzyme B secretion compared to the other tested antibodies (Figure 18A and 18B). The increased release of Granzyme B suggests that the humanized anti-SLAMF6 antibodies may promote a stronger cytotoxic T cell response and potentially enhanced tumor cell killing.

[0308] In an additional functional assay, performed essentially as described above with respect to Figure 15A (Granzyme B secretion by primary human PBMCs from healthy donors), PBMCs from two healthy donors (presented in Figures 19A and 19B, respectively), were activated for 48 hours with plate bound anti-CD3 and humanized anti-SLAMF6 variants or control antibodies, essentially as described above. Conditioned media was collected and Granzyme B levels was measured by ELISA. Results are presented as fold increase compared to Granzyme B of CD3 activation only control.

[0309] As can be seen in Figures 19A and 19B, humanized anti SLAMF6 variants retain the capacity to enhance granzyme B release form human PBMCs following activation with anti-CD3. In particular, Hu007-05 (BM1), Hu007-08 (BM7), Hu007-09 (BM2) and Hu007-12 (BM8) showed superior effects compared to the other tested antibodies. For further evaluating the ability of the Hu07-08 antibody to modulate IFN-y release and CD107a degranulation in human PBMC, healthy donor PBMC were activated for 48 hours with plate-bound anti-CD3 and Hu07-08 or its isotype control (hlgGl(LALA)), essentially as described above. Conditioned media were collected and IFN-y levels were measured by ELISA, as indicated in Figure 20A. controls includes the anti-CD3 antibody alone (aCD3) and cells with no added antibody treatment ("no t"). In parallel, cells were collected and the percentage of CD107a-CD8 positive cells was evaluated by flow cytometry, as indicated in Figure 20B. The results demonstrate enhanced IFN-y release and CD107a degranulation in human PBMC following activation with anti CD3 and the humanized anti-SLAMF6 antibody Hu07-08. The increased release of IFN-y and CD107a degranulation suggests that the humanized anti-SLAMF6 antibody is promoting a stronger cytotoxic T cell response, potentially enhancing immune surveillance and tumor cell killing.

[0310] In summary, several anti SLAMF6 antibodies were generated, with varying binding affinities (KD) to human SLAMF6, including monoclonal murine antibodies, chimeric antibodies and humanized antibodies. Antibodies that showed enhanced functionality in several functional assays were selected for further development. Several antibodies also demonstrated functional superiority in comparison to known anti-SLAMF6 antibodies. Several antibodies also showed cross-binding to cynoSLAMF6.

[0311] Example 7. Large-scale production and characterization of fully humanized antibodies

[0312] The fully humanized antibody Hu007-08 (BM7) was selected for large-scale production and further characterization, as detailed below. For recombinant production of the humanized antibody Hu007-08 (BM7), nucleic acid constructs encoding the corresponding antibody chains were cloned into expression vector PCDNA3.4. The nucleic acid sequences and corresponding encoded protein sequences used to construct the expression vector are provided below, in which the signal peptides are underlined and the variable regions are in bold.

[0313] Heavy chain construct - hu007-VH-g0(BM6)-hIgGl(DEL. L234A.L235A), SEQ ID NO: 143:

[0314]

[0315] Large-scale production of the Hu007-08 (BM7) antibody and its isotype control was performed as follows.

[0316] Expression vectors (also referred to herein as plasmids) were amplified for mammalian expression. To this end, plasmids were transformed to E.coli strains (DH5a / TOP10) for propagation respectively in appropriate scale. Purified plasmids were checked by agarose gel and confirmed by sequencing.

[0317] The plasmids encoding the heavy chain and light chain of each antibody were cotransfected into CHO cells using polyethylenimine (PEI, PEI MAX-Transfection (Polysciences Inc, Cat#24765-1, according to manufacturer's instructions), and cultured at 32°C. Culture supernatants were harvested 9 days post transfection by centrifugation at 120 rpm.

[0318] Following centrifugation and filtration, cell culture supernatants were subjected to Protein A affinity chromatography using MabSelectPrismA Protein A column (Cytiva, Cat#17549852, according to the manufacturer instructions) for purification of the produced antibodies. The eluted antibodies were dialyzed into formulation buffer and analyzed by SDS-PAGE, SEC-HPLC and endotoxin measurement.

[0319] Next, binding affinity of the resulting antibody was characterized essentially as described above. A binding assay using intact Jurkat cells that naturally express SLAMF6 on their surface was conducted essentially as described above. Secondary antibody used was Alexa Fluor® 488 goat anti-human IgG(H+E). The results indicate that large-scale produced humanized antibody Hu007-08(BM7) demonstrated similar binding affinity to cell-presented SEAMF6 as the small- scale produced antibody used in the previous Examples.

[0320] Table 36 presents the results of a kinetic (Biacore) analysis of the interaction of large- scale produced Hu007-08 (BM7) with the recombinant human SEAMF6 ectodomain polypeptide. The kinetics (affinity) model used in the assays was 1:1 binding, and the analyte solution contained the human SEAMF6 ECD-6His polypeptide. For the capture solution, 2 pg / ml of the indicated test antibody Hu007-08 (BM7) or parental chimeric antibody cmAbO7-VH(NG-GG) antibody (containing the same IgGl(EAEA) constant region) were used. As can be seen, the large- scale produced humanized antibody and corresponding chimeric antibody retained similar binding affinity to the SEAMF6 polypeptide.

[0321] Table 36 - Affinity analysis by Biacore - large-scale produced Hu007-08 and corresponding chimeric antibody.

[0322] Next, the large-scale produced antibody was subjected to stability studies. To this end, the Hu007-08 antibody was reconstituted in either phosphate buffered saline (PBS) or in TT1 buffer containing 200mM Arginine, 137mM Succinic acid, 5% Trehalose, and 0.05% Tween-80 (% by weight), pH5.0, and stored under different temperatures and relative humidity conditions, as indicated in Figures 21A-21C. The stored samples were filtrated through MILLEX-MP 0.22um. Stability study was performed by SEC-HPLC measurement of degradation of the monomeric fraction of the antibody. The results are presented as % of the monomer fraction over time in Figures 21A (storage at -20±5°C), 21B (storage at 5±3°C), and 21C (storage at 25±5°C, 60%±5% relative humidity (RH)). As can be seen, the antibody exhibited high stability in various storage conditions. As can further be seen, the TT1 buffer facilitated enhanced stability of the antibody throughout the storage conditions as compared to PBS. Similar results were obtained for antibody storage at 40°C for 4 weeks.

[0323] Example 8. Anti-tumor cytotoxicity

[0324] The ability of the antibodies to modulate anti-tumor lymphocyte response was examined using two tumor cell lines: MDA-MB-231 human breast cancer cells, and LCL 721.221 human B-lymphoblastoid cells.

[0325] NK cell killing assay was performed by an over-night co-culture of YTS NK cells with LCL721.221 tumor cells together with plate-bound anti-SLAMF6 Hu07-08 (5pg / ml). Two effector-to-target ratios were used (2.5 to 1 and 1.25 to 1). Conditioned media were collected and Calcein AM levels were used as a marker for target cell lysis measurement. Percent Lysis calculation: Specific Lysis (%) = ((calcein reading - spontaneous release) / (maximal release - spontaneous release))* 100. The results are presented in Figure 22, in which " Hu-007-08(BM7)" represents YTS NK and tumor cells co-cultured with the humanized antibody, "hlgG (LALA)" represents YTS NK and tumor cells co-cultured with the isotype control, and "No Ab" represents YTS NK and tumor cells incubated without antibody present in culture. As can be seen, the results demonstrate augmented cytotoxicity against LCL721.221 lymphoblastoid tumor cell line by NK cells when treated with humanized anti SLAMF6 antibody.

[0326] Healthy donor PBMC were activated for 24h with 1 g / ml plate bound anti-CD3 and 5 pg / ml anti-SLAMF6 Hu08-07 or control antibodies. The resulting lymphocytes were co-cultured at a 10 to 1 ratio with MDA-MB-231 tumor cells stably expressing red fluorescent protein (MDA- 231-RFP+ cells). The number of surviving tumor cells were longitudinally (4 days) counted using an Incucyte device. The results are presented as the proportion of viable tumor cells (normalized red object counts per image) in Figure 23, in which "IgGl(LALA)" represents an isotype control antibody, "Ctrl Ab#l" represents a reference anti-SLAMF6 antibody), and Hu07-08(BM7) represents large-scale produced humanized antibody Hu08-07. As can be seen, Hu08-07 induced significantly augmented lymphocyte cytotoxicity against MDA-MB-231 cells as compared to both the isotype control antibody and the reference anti-SLAMF6 antibody.

[0327] The foregoing description of the specific embodiments will so fully reveal the general nature of the invention that others can, by applying current knowledge, readily modify and / or adapt for various applications such specific embodiments without undue experimentation and without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. The means, materials, and steps for carrying out various disclosed functions may take a variety of alternative forms without departing from the invention.

Claims

CLAIMS1. An antibody specific to human SLAMF6 (hSLAMF6), or a molecule comprising at least an antigen-binding fragment thereof, wherein: a) the antibody or molecule comprises a set of a heavy chain variable region (VH) and a light chain variable region (VL) as follows:b) the antibody or molecule comprises VH and VL sequences having at least 90%, 95%, 98% or 99% identity to the VH and VL sequences of a), or c) the antibody or molecule comprises a set of six complementarity determining regions (CDRs) as follows: DYYMN (SEQ ID NO: 7), D INPNGGD S SYNQKFKG (SEQ ID NO: 79), FTTVDY (SEQ ID NO: 13), KS SQSLLD SYGKTYLN (SEQ ID NO: 33), LVSKLD S (SEQ ID NO: 11), and WQGTHFPQT (SEQ ID NO: 15), or comprises up to 3 amino acid modifications in each CDR.

2. The antibody or molecule of claim 1, which comprises a set of six CDRs selected from the group consisting of:

3. The antibody or molecule of claim 2, which comprises the VH and VL sequences of SEQ ID NOs: 137 and 139.

4. The antibody or molecule of claim 1 or 2, which comprises VH and VL sequences having at least 90%, 95%, 98% or 99% identity to the VH and VL sequences of SEQ ID NOs: 137 and 139, with the proviso that the leucine at position 41 of SEQ ID NO: 139 is retained.

5. The antibody or molecule of claim 1, which induces or enhances direct cell- mediated cytotoxicity by primary human lymphocytes.

6. The antibody or molecule of any one of the preceding claims, which is a monoclonal antibody.

7. The antibody of claim 6, comprising a human or humanized constant (Fc) region of the IgGl or IgG4 isotype.

8. The antibody of claim 7, wherein said Fc region is an engineered human IgGl or IgG4 that does not substantially bind to Fey receptors.

9. The antibody or molecule of claim 1, which binds to a SLAMF6 polypeptide having the amino acid sequence as set forth in SEQ ID NO: 130 with an equilibrium dissociation constant (KD) of 1.01x10-7M to 4.85x10-10M.

10. The antibody or molecule of claim 5, wherein the lymphocytes are tumor- specific lymphocytes.

11. The antibody or molecule of claim 5, which induces or enhances tumor-induced Granzyme B secretion from said lymphocytes.

12. The antibody or molecule of claim 5, which induces or enhances said direct cell- mediated cytotoxicity without substantially inducing or enhancing drug-induced toxicity, antibody-dependent cellular cytotoxicity (ADCC) and complement-dependent cytotoxicity (CDC).

13. A nucleic acid construct encoding the antibody or molecule according to any one of the preceding claims.

14. The nucleic acid construct of claim 13, comprising a nucleic acid sequence as set forth in SEQ ID NO: 143 or 145, or having at least 90%, 95%, 98% or 99% identity thereto.

15. A host cell comprising at least one nucleic acid construct of claim 13 or 12.

16. A pharmaceutical composition comprising a therapeutically effective amount of at least one antibody or molecule according to any one of claims 1-12, and a pharmaceutical excipient.

17. The pharmaceutical composition of claim 16, which is formulated for injection and comprises an arginine- succinate buffer, trehalose, and at least one surfactant.

18. The pharmaceutical composition of claim 16 or 17, for use in therapy.

19. The pharmaceutical composition of claim 18, for use in treating cancer in a subject in need thereof.

20. The pharmaceutical composition of claim 19, wherein the subject is afflicted with a solid tumor.

21. The pharmaceutical composition of claim of claim 20, wherein the tumor is selected from the group consisting of melanoma, renal cell carcinoma, lung carcinoma, breast carcinoma, and head and neck carcinoma.

22. The pharmaceutical composition for use of any one of claims 18-21, wherein said antibody or molecule is an antibody comprising a human or humanized Fc region of the IgG4 isotype optionally engineered to substantially eliminate binding to Fey receptors, or a human or humanized Fc region of the IgGl isotype engineered to substantially eliminate binding to Fey receptors.

23. The composition for use of any one of claims 18-21, wherein the use does not substantially include induction of drug-induced toxicity, antibody-dependent cellular cytotoxicity (ADCC) and / or complement-dependent cytotoxicity (CDC).

24. The composition for use of claim 23, wherein said treatment or use does not substantially include induction of any one of drug-induced toxicity, ADCC and CDC.

25. The composition for use of claim 19 wherein the subject is afflicted with a hematopoietic malignancy.

26. A method of treating cancer in a subject in need thereof, comprising administering to the subject the pharmaceutical composition of claim 16.

27. The method of claim 26, wherein the subject is afflicted with a solid tumor.

28. The method of claim 27, wherein the tumor is selected from the group consisting of melanoma, renal cell carcinoma, lung carcinoma, breast carcinoma, and head and neck carcinoma.

29. The method of claim 26, wherein said antibody or molecule is an antibody comprising a human or humanized Fc region of the IgG4 isotype optionally engineered to substantially eliminate binding to Fey receptors, or a human or humanized Fc region of the IgGl isotype engineered to substantially eliminate binding to Fey receptors.

30. The method of claim 29, wherein the treatment does not substantially include induction of drug-induced toxicity, antibody-dependent cellular cytotoxicity (ADCC) and / or complement-dependent cytotoxicity (CDC).

31. The method of claim 30, wherein said treatment or use does not substantially include induction of any one of drug-induced toxicity, ADCC and CDC.

32. The method of claim 26, wherein the subject is afflicted with a hematopoietic malignancy.

33. A method for detecting or quantifying the presence of SLAMF6 in a sample, comprising the steps of:(i) incubating the sample with the antibody or molecule of claim 1, under conditions enabling the formation of an antigen-antibody complex; and(ii) detecting or quantifying the antigen-antibody complex.

34. An antibody specific to human SLAMF6 (hSLAMF6), or a molecule comprising at least an antigen-binding fragment thereof, wherein: a) the antibody comprises a set of a heavy chain variable region (VH) and a light chain variable region (VL) of an antibody listed in Table 28, b) said antibody comprises VH and VL sequences having at least 90%, 95%, 98% or 99% identity to the VH and VL sequences of a), c) said antibody is a chimeric or humanized form of the antibody of a) or b), or d) said antibody or molecule comprises a set of six complementarity determining regions (CDRs) as set forth in one of Tables 1-26, or comprising up to 3 amino acid modifications in each CDR.

35. The antibody or molecule of claim 34, which comprises a set of six CDRs as set forth in one of Tables 1-26.

36. The antibody or molecule of any one of claims 34-35, which is a chimeric or humanized antibody.

37. The antibody or molecule of claim 36, which comprises a set of six CDRs of an antibody selected from the group consisting of: a) Ab07, comprising the three VH CDR sequences and the three VL CDR sequences as set forth in Table 7, b) Ab07 VH(NG_ GG), comprising the three VH CDR sequences and the three VL CDR sequences set forth in Table 21, c) Ab07 VH(NG_SG), comprising the three VH CDR sequences and the three VL CDR sequences set forth in Table 22, d) Ab07 VH(NG. NA), comprising the three VH CDR sequences and the three VL CDR sequences set forth in Table 23, e) Abl9, comprising the three VH CDR sequences and the three VL CDR sequences set forth in Table 17, f) Ab 19 VL(DG_SG), comprising the three VH CDR sequences and the three VL CDR sequences set forth in Table 24,g) Ab 19 VL(DG_DA), comprising the three VH CDR sequences and the three VL CDR sequences set forth in Table 25, and h) Ab 19 VL(DG_GG), comprising the three VH CDR sequences and the three VL CDR sequences set forth in Table 26.

38. The antibody or molecule of claim 37, which comprises a set of VH and VL regions of an antibody listed in Table 27.

39. An antibody, or a molecule comprising at least an antigen-binding fragment thereof, which comprises a set of six CDRs as set forth in one of Tables 1-26, or which binds to an epitope on hSLAMF6 recognized by an antibody comprising a set of six CDRs as set forth in one of Tables 1-26, or which cross-competes for hSLAMF6 binding with an antibody comprising a set of six CDRs as set forth in one of Tables 1-26.

40. The antibody or molecule of claim 39, which comprises a set of VH and VL regions of an antibody listed in Table 28 or 27.

41. The antibody or molecule of any one of claims 34-40, which is a monoclonal antibody.

42. The antibody of claim 41, which is a chimeric antibody or a humanized antibody preferably comprising a human or humanized constant (Fc) region of the IgGl or IgG4 isotype.

43. The antibody of claim 42, wherein said Fc region is an engineered human IgGl or IgG4 that does not substantially bind to Fey receptors.

44. The antibody or molecule of any one of claims 34-43, which binds to a SLAMF6 polypeptide having the amino acid sequence as set forth in SEQ ID NO: 130 with an equilibrium dissociation constant (KD) of l.Olx10-7M to 4.85x10-10M, or which binds to a SLAMF6 polypeptide having the amino acid sequence as set forth in SEQ ID NO: 130 with a KD of 9xl0'8M to Ix10-9M.

45. A nucleic acid construct encoding the antibody or molecule according to any one of claims 34-44.

46. A host cell comprising at least one nucleic acid construct of claim 45.

47. A pharmaceutical composition comprising a therapeutically effective amount of at least one antibody or molecule according to any one of claims 34-46, and a pharmaceutical excipient.

48. The pharmaceutical composition of claim 47, for use in therapy.

49. The pharmaceutical composition of claim 45, for use in treating cancer in a subject in need thereof.

50. A method of treating cancer in a subject in need thereof, comprising administering to the subject the pharmaceutical composition of claim 47.

51. A method for detecting or quantifying the presence of SLAMF6 in a sample, comprising the steps of:(i) incubating the sample with the antibody or molecule of claim 32 or 37, under conditions enabling the formation of an antigen-antibody complex; and (ii) detecting or quantifying the antigen-antibody complex.

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