Antibodies against slam family member 6 and uses thereof

Abstract

While immune checkpoint inhibitors (ICIs) have demonstrated the ability to enhance the immune response against tumors, a significant number of patients do not exhibit a response to the ICIs currently available. The present disclosure provides alternative ICIs. It relates to SLAMF6-binding molecules such as antibodies or antigen-binding fragments thereof that reduce or inhibit cis SLAMF6-SLAMF6 interactions, which negatively regulate T cell activation, and their uses for enhancing T cell activation and / or for preventing T cell exhaustion and / or for increasing the proportion of T cells infiltrating tumors and / or for reducing tumor growth. This mechanism does not require expression of SLAMF6 on tumor cells.

Description

[0001] TITLE

[0002] ANTIBODIES AGAINST SLAM FAMILY MEMBER 6 AND USES THEREOF

[0003] CROSS REFERENCE TO RELATED APPLICATIONS

[0004] This application is PCT application Serial No PCT / CA2025 / * filed on October 2, 2025 and published in English under PCT Article 21 (2), which claims benefit of U.S. provisional application Serial No. 63 / 703,427, filed on 4 October 2024. All documents above are incorporated herein in their entirety by reference.

[0005] STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0006] N.A.

[0007] FIELD OF THE DISCLOSURE

[0008] The present disclosure is concerned with anti-SLAMF6 antibodies for use in increasing T cell activation for e.g., reducing tumor growth.

[0009] REFERENCE TO SEQUENCE LISTING

[0010] Pursuant to 37 C.F.R. 1 .821 (c), a sequence listing is submitted herewith as an ASCII compliant text file named G 10992- 00076-Sequence listing, that was created on October 2, 2025 and having a size of 190 kilobytes. The content of the aforementioned file is hereby incorporated by reference in its entirety.

[0011] BACKGROUND OF THE DISCLOSURE

[0012] T cells have critical roles in anti-tumor and anti-viral immunity, as well as in auto-immune diseases (Chakraborty et al. 2014; Chan et al. 1994; Veillette et al. 2002). Activation of T cells is initiated by antigen-specific signals triggered upon engagement of the T cell receptor (TCR) for antigen. It is also tightly influenced by antigen-independent signals emanating from co-receptors, which optimize beneficial immune cell activation, while restraining unwanted immune responses. Two categories of co-receptors are expressed at the T cell surface that can be engaged in trans by ligands on antigen-presenting cells (APCs) or in cis by ligands co-expressed on T cells: co-stimulatory receptors (such as CD4, CD8, CD28, CD2 and ICOS) that deliver positive signals to T cells, and co-inhibitory receptors (including PD-1 and CTLA-4) that attenuate TCR signal strength (Alegre et al, 2001 ; Ishida et al, 1992; Li et al, 2022; Rudd et al, 2003; Veillette et al, 1988; Zhao et al. 2019).

[0013] Co-inhibitory receptors have a central role in maintaining self-tolerance and regulating immune homeostasis. Under normal physiological conditions, co-inhibitory receptors allow the immune system to respond appropriately to malignancies and infections while protecting normal tissues from damage (Attanasio et al. 2016). However, ligands for co-inhibitory receptors are often overexpressed or aberrantly expressed on tumor cells or tumor stromal cells, thereby diminishing T cell activation and facilitating uncontrolled proliferation of cancer cells (Alsaab et al. 2017). Multiple studies have shown that blockade of co-inhibitory receptors or of their ligands can remove this immunological brake and promote a more effective immune response against tumors. Blocking antibodies targeting CTLA-4, PD-1 (or its ligand PD-L1), LAG-3 or TIGIT, the so-called “immune checkpoint inhibitors (ICIs)”, have led to apparent cures in patients with melanoma, renal cell carcinoma and other cancers (Chae et al. 2018; Ghiringhelli et al. 2023; Weinstock et al. 2015). Unfortunately, many cancer types and patient populations do not respond to the currently available ICIs (Machiraju et al. 2021).

[0014] There is a need for alternative ICIs.

[0015] The present description refers to a number of documents, the content of which is herein incorporated by reference in their entirety.

[0016] SUMMARY OF THE DISCLOSURE

[0017] The present disclosure shows that anti-SLAMF6 mAbs suppress the growth of tumor cells in vivo. The present disclosure also shows that this activity is mediated by enhancing T cell activation in naive and in activated T cells, through blocking homotypic cis SLAMF6-SLAMF6 interaction at the T cell surface which negatively regulates T cell activation. The present disclosure also shows that anti-SLAMF6 mAbs prevent T cell exhaustion and increase the proportion of T cells infiltrating tumors in vivo. These activities are independent of expression of SLAMF6 on tumor cells.

[0018] More specifically, in accordance with the present disclosure, there are provided the following items:

[0019] Item 1 . An anti-SLAM family member 6 (SLAMF6) antibody or an antigen-binding fragment thereof which binds to an Ig like domain defined by residues 35 to 120 of human SLAMF6 or to an epitope within this domain of human SLAMF6.

[0020] Item 2. The anti-SLAMF6 antibody or antigen-binding fragment thereof of item 1 , comprising:

[0021] (i) a light chain complementary determining region (CDR) 1 region comprising an amino acid sequence of formula I: X1 -A-S-X2-X3-X4-X5-X6-X7-X8-A (I) wherein

[0022] X1 is K or R;

[0023] X2 is Q or E;

[0024] X3 is D or N;

[0025] X4 is V or I;

[0026] X5 is S or Y;

[0027] X6 is T, N or S

[0028] X7 is A, R or N; and

[0029] X8 is V or L;

[0030] (ii) a light chain complementary determining region (CDR) 2 region comprising an amino acid sequence of formula II: Y1-A-Y2-Y3-Y4-Y5-Y6 (II) wherein

[0031] Y1 is , G or A;

[0032] Y2 is S or T;

[0033] Y3 is T, S or N;

[0034] Y4 is R or L; Y5 is H, E or A; and

[0035] Y6 is T or D;

[0036] (iii) a light chain complementary determining region (CDR) 3 region comprising an amino acid sequence of formula III:

[0037] Q-Z1-Z2-Z3-Z4-Z5-Z6-Z7-T (III) wherein

[0038] Z1 is Q or H;

[0039] Z2 is H, Y or F;

[0040] Z3 is Y or W;

[0041] Z4 is S or G;

[0042] Z5 is T or N;

[0043] Z6 is P or S; and

[0044] Z7 is F or W;

[0045] (iv) a heavy chain complementary determining region (CDR) 1 region comprising an amino acid sequence of formula IV:

[0046] G-A1-A2-A3-A4-A5-A6-A7-A8 (IV) wherein

[0047] A1 is F or Y;

[0048] A2 is S or T;

[0049] A3 is L or F;

[0050] A4 is S or T;

[0051] A5 is T or D;

[0052] A6 is F or Y;

[0053] A7 is G or absent; and

[0054] A8 is M or absent;

[0055] (v) a heavy chain CDR2 region comprising an amino acid sequence of formula V:

[0056] B1-B2-B3-B4-B5-B6 (V) wherein

[0057] B1 is W or N;

[0058] B2 is W or P;

[0059] B3 is D, S or N;

[0060] B4 is D or N;

[0061] B5 is G or is absent; and

[0062] B6 is D or G; and

[0063] (vi) a heavy chain CDR3 region comprising an amino acid sequence of formula VI:

[0064] C 1 -C2-C3-C4-C5-C6-C7-C8-C9-C 10-D-Y (VI) wherein

[0065] C1 is T, E or S; C2 is G or L;

[0066] C3 is K, S or G;

[0067] C4 is G, L or is absent;

[0068] C5 is N, R or is absent;

[0069] C6 is Y or is absent;

[0070] C7 is Y or is absent;

[0071] C8 is H, S or is absent;

[0072] C9 is A, T or is absent; and

[0073] C10 is F or M.

[0074] Item 3. The anti-S LAM F6 antibody or antigen-binding fragment thereof of item 2, wherein

[0075] (i) the amino acid sequence of formula I is:

[0076] X1-A-S-E-X3-I-Y-X6-X7-L-A (I) wherein

[0077] X1 is K or R;

[0078] X3 is D or N;

[0079] X6 is N or S; and

[0080] X7 is R or N;

[0081] (ii) the amino acid sequence of formula II is:

[0082] Y1-A-T-Y3-L-Y5-Y6 (II) wherein

[0083] Y1 is G or A;

[0084] Y3 is S or N;

[0085] Y5 is E or A; and

[0086] Y6 is T or D;

[0087] (iii) the amino acid sequence of formula III is:

[0088] Q-Z1-Z2-W-Z4-Z5-Z6-W-T (lll) wherein

[0089] Z1 is Q or H;

[0090] Z2 is Y or F;

[0091] Z4 is S or G;

[0092] Z5 is T or N; and

[0093] Z6 is P or S;

[0094] (iv) the amino acid sequence of formula IV is:

[0095] G-Y-T-F-T-D-Y (SEQ ID NO : 1) (IV);

[0096] (v) the amino acid sequence of formula V is:

[0097] N-P-B3-N-G-G (V) wherein B3 is S or N; and

[0098] (vi) the amino acid sequence of formula VI is:

[0099] C 1 -C2-C3-C4-C5-C6-C7-C8-C9-C 10-D-Y (VI) wherein

[0100] C1 is E or S;

[0101] C2 is G or L;

[0102] C3 is S or G;

[0103] 04 is L or is absent;

[0104] C5 is R or is absent;

[0105] C6 is Y or is absent;

[0106] 07 is Y or is absent;

[0107] C8 is H or S;

[0108] C9 is A, or T; and

[0109] C10 is F or M.

[0110] Item 4. The anti-S LAM F6 antibody or antigen-binding fragment thereof of item 1 , comprising:

[0111] (a) a light chain complementary determining region (CDR) 1 comprising one of the following amino acid sequences KASQDVSTAVA (SEQ ID NO: 21), KASEDIYNRLA (SEQ ID NO: 63) or RASENIYSNLA (SEQ ID NO: 105), preferably KASEDIYNRLA (SEQ ID NO: 63) or RASENIYSNLA (SEQ ID NO: 105);

[0112] (b) a light chain CDR2 comprising one of the following amino acid sequences: WASTRHT (SEQ ID NO: 27), GATSLET (SEQ ID NO: 69) or AATNLAD (SEQ ID NO: 111), preferably GATSLET (SEQ ID NO: 69) or AATNLAD (SEQ ID NO: 111);

[0113] (c) a light chain CDR3 comprising one of the following amino acid sequences: QQHYSTPFT (SEQ ID NO: 32), QQYWSNSWT (SEQ ID NO: 74) or QHFWGTPWT (SEQ ID NO: 116), preferably QQYWSNSWT (SEQ ID NO: 74) or QHFWGTPWT (SEQ ID NO: 116);

[0114] (d) a heavy chain CDR1 comprising one of the following amino acid sequences: GFSLSTFGM (SEQ ID NO: 40), or GYTFTDY (SEQ ID NO: 82), preferably GYTFTDY (SEQ ID NO: 82);

[0115] (e) a heavy chain CDR2 comprising one of the following amino acid sequences: WWDDD (SEQ ID NO: 48), NPSNGG (SEQ ID NO: 90) or NPNNGG (SEQ ID NO: 127), preferably NPSNGG (SEQ ID NO: 90) or NPNNGG (SEQ ID NO: 127); and

[0116] (f) a heavy chain CDR3 comprising one of the following amino acid sequences: TGKGNYFDY (SEQ ID NO: 55), EGSLRYYHAMDY (SEQ ID NO: 97) or SLGSTFDY (SEQ ID NO: 134), preferably EGSLRYYHAMDY (SEQ ID NO: 97) or SLGSTFDY (SEQ ID NO: 134).

[0117] Item 5. The anti-SLAMF6 antibody or antigen-binding fragment thereof of item 4, wherein:

[0118] (i) the light chain CDR1 comprises the amino acid sequence KASQDVSTAVA (SEQ ID NO: 21), the light chain CDR2 comprises the amino acid sequence WASTRHT (SEQ ID NO: 27), the light chain CDR3 comprises the amino acid sequence QQHYSTPFT (SEQ ID NO: 32), the heavy chain CDR1 comprises the amino acid sequence GFSLSTFGM (SEQ ID NO: 40); the heavy chain CDR2 comprises the amino acid sequence WWDDD (SEQ ID NO: 48), and the heavy chain CDR3 comprises the amino acid sequence TGKGNYFDY (SEQ ID NO: 55); or

[0119] (ii) the light chain CDR1 comprises the amino acid sequence KASEDIYNRLA (SEQ ID NO: 63), the light chain CDR2 comprises the amino acid sequence GATSLET (SEQ ID NO: 69), the light chain CDR3 comprises the amino acid sequence QQYWSNSWT (SEQ ID NO: 74), the heavy chain CDR1 comprises the amino acid sequence GYTFTDY (SEQ ID NO: 82); the heavy chain CDR2 comprises the amino acid sequence NPSNGG (SEQ ID NO: 90), and the heavy chain CDR3 comprises the amino acid sequence EGSLRYYHAMDY (SEQ ID NO: 97); or

[0120] (iii) the light chain CDR1 comprises the amino acid sequence RASENIYSNLA (SEQ ID NO: 105), the light chain CDR2 comprises the amino acid sequence AATNLAD (SEQ ID NO: 111), the light chain CDR3 comprises the amino acid sequence QHFWGTPWT (SEQ ID NO: 116), the heavy chain CDR1 comprises the amino acid sequence GYTFTDY (SEQ ID NO: 82); the heavy chain CDR2 comprises the amino acid sequence NPNNGG (SEQ ID NO: 127), and the heavy chain CDR3 comprises the amino acid sequence SLGSTFDY (SEQ ID NO: 134).

[0121] Item 6. The anti-SLAMF6 antibody or antigen-binding fragment thereof of any one of items 1 to 5, further comprising:

[0122] (i) a light chain framework region 1 (FR1) comprising an amino acid sequence of formula VII: D-l-Xb1-M-T-Q-S-Xb2-Xb3-Xb4-Xb5-S-Xb6-S-Xb7-G-Xb8-Xb9-V-Xb10-l-T-C (VII) wherein

[0123] Xb1 is V or Q;

[0124] Xb2 is H, S or P;

[0125] Xb3 is K, S or A;

[0126] Xb4 is F or S;

[0127] Xb5 is M, F or L;

[0128] Xb6 is T or V;

[0129] Xb7 is V or L;

[0130] Xb8 is D or E;

[0131] Xb9 is R or T; and

[0132] XbW is S or T;

[0133] (ii) a light chain FR2 comprising an amino acid sequence of formula VIII:

[0134] W-Y-Q-Q-K-Xb11 -G-Xb12-Xb13-P-Xb14-L-L-Xb15-Xb16 (VIII) wherein

[0135] Xb11 is P or Q;

[0136] Xb12 is Q, N or K;

[0137] Xb13 is S or A;

[0138] Xb14 is K, R or Q;

[0139] Xb15 is I or V; and

[0140] Xb16 is Y or S; (iii) a light chain FR3 comprising an amino acid sequence of formula IX:

[0141] G-V-P-Xb17-R-F-Xb18-G-S-G-S-G-Xb19-Xb20-Y-Xb21 -L-Xb22-I-Xb23-S-Xb24-Q-Xb25-E-D-Xb26-Xb27-Xb28-Y-Y-C

[0142] (IX) wherein

[0143] Xb1 isDorS;

[0144] Xb18isTorS;

[0145] Xb19 is T or K;

[0146] Xb20 is D or Q;

[0147] Xb21 isTorS;

[0148] Xb22 is T, S or K;

[0149] Xb23 is S, T or N;

[0150] Xb24 isVor L;

[0151] Xb25 isA, TorS;

[0152] Xb26 is L, V or F;

[0153] Xb27 is A or G; and

[0154] Xb28 is L, TorS;

[0155] (iv) a light chain FR4 comprising an amino acid sequence of formula X:

[0156] F-G-Xb29-G-T-K-L-E-I-K (X) (SEQ ID NO: 195) wherein

[0157] Xb29 is S or G;

[0158] (v) a heavy chain FR1 comprising an amino acid sequence of formula XI:

[0159] Xb30-V-Xb31-L-Xb32-Xb33-S-G-P-Xb34-Xb35-Xb36-Xb37-P-Xb38-Xb39-Xb40-Xb41-Xb42-Xb43-Xb44-C-Xb45-

[0160] Xb46-S (XI) wherein

[0161] Xb30 is Q or E;

[0162] Xb31 isTorQ;

[0163] Xb32 is K or Q;

[0164] Xb33 is E or Q;

[0165] Xb34 is G or E;

[0166] Xb35 is I or L;

[0167] Xb36 isLorV;

[0168] Xb37 is Q or K;

[0169] Xb38 is S or G;

[0170] Xb39 is Q or A;

[0171] Xb40 is T, A or S;

[0172] Xb41 isLorV;

[0173] Xb42 is S or K; Xb43 is L or I;

[0174] Xb44 is T, S or P;

[0175] Xb45 is S or K; and

[0176] Xb46 is F or A;

[0177] (vi) a heavy chain FR2 comprising an amino acid sequence of formula XII:

[0178] Xb47-Xb48-Xb49-W-Xb50-Xb51 -Q-Xb52-Xb53-G-K-Xb54-L-E-W-Xb55-Xb56-Xb57-I (XI I) wherein

[0179] Xb47 is G or absent;

[0180] Xb48 is V or M;

[0181] Xb49 is G, N or D;

[0182] Xb50 is I or V;

[0183] Xb51 is R or K;

[0184] Xb52 is P or S;

[0185] Xb53 is S or H;

[0186] Xb54 is G or S;

[0187] Xb55 is L or I;

[0188] Xb56 is A or G; and

[0189] Xb57 is H or D;

[0190] (vii) a heavy chain FR3 comprising an amino acid sequence of formula XIII:

[0191] Xb58-Xb59-Xb60-N-Xb61 -Xb62-Xb63-K-Xb64-Xb65-Xb66-T-Xb67-Xb68-Xb69-D-Xb70-S-Xb71 -Xb72-Xb73-Xb74-

[0192] Xb75-Xb76-Xb77-Xb78-Xb79-Xb80-Xb81 -Xb82-Xb83-Xb84-D-Xb85-A-Xb86-Y-Y-C-A-Xb87 (XI 11) wherein

[0193] Xb58 is K, S or T;

[0194] Xb59 is Y, R or L;

[0195] Xb60 is Y, N or Y;

[0196] Xb61 is P, Q or R;

[0197] Xb62 is A or K;

[0198] Xb63 is L or F;

[0199] Xb64 is S or G;

[0200] Xb65 is R or K;

[0201] Xb66 is L or A;

[0202] Xb67 is I or L;

[0203] Xb68 is S or T;

[0204] Xb69 is K or V;

[0205] Xb70 is T or K;

[0206] Xb71 is K or S;

[0207] Xb72 is N or S; Xb73 is Q or T;

[0208] Xb74 is V or A;

[0209] Xb75 is F or Y;

[0210] Xb76 is L or M;

[0211] Xb77 is K or E;

[0212] Xb78 is I or L;

[0213] Xb79 is A or R;

[0214] Xb80 is N or S;

[0215] Xb81 is V or L;

[0216] Xb82 is D or T;

[0217] Xb83 is T or S;

[0218] Xb84 is A or E;

[0219] Xb85 is T or S;

[0220] Xb86 is T or V; and

[0221] Xb87 is P or R;

[0222] (viii) a heavy chain FR4 comprising an amino acid sequence of formula XIV:

[0223] W-G-Q-G-T-Xb88-Xb89-T-V-S-S (XIV) (SEQ ID NO: 196) wherein

[0224] Xb88 is T or S; and

[0225] Xb89 is L or V; or

[0226] (ix) a combination of at least two of (i) to (viii).

[0227] Item 7. The anti-SLAMF6 antibody or antigen-binding fragment thereof of item 6, wherein:

[0228] (i) the amino acid sequence of formula VII is: D-I-Q-M-T-Q-S-Xb2-Xb3-S-Xb5-S-V-S-Xb7-G-Xb8-Xb9-V-T-I-T-C (VII) (SEQ ID NO: 197) wherein

[0229] Xb2 is S or P;

[0230] Xb3 is S or A;

[0231] Xb5 is F or L;

[0232] Xb7 is V or L;

[0233] Xb8 is D or E; and

[0234] Xb9 is R or T;

[0235] (ii) the amino acid sequence of formula VIII is:

[0236] W-Y-Q-Q-K-Xb11 -G-Xb12-Xb13-P-Xb14-L-L-Xb15-Xb16 (VIII) (SEQ ID NO: 198) wherein

[0237] Xb11 is P or Q;

[0238] Xb12 is N or K;

[0239] Xb13 is S or A; Xb14 is R or Q;

[0240] Xb15 is I or V; and

[0241] Xb16 is Y or S;

[0242] (iii) the amino acid sequence of formula IX is:

[0243] G-V-P-S-R-F-S-G-S-G-S-G-Xb19-Xb20-Y-Xb21-L-Xb22-l-Xb23-S-L-Q-Xb25-E-D-Xb26-Xb27-Xb28-Y-Y-C (IX)

[0244] (SEQ ID NO: 199) wherein

[0245] Xb19 is T or K;

[0246] Xb20 is D or Q;

[0247] Xb21 is T or S;

[0248] Xb22 is S or K;

[0249] Xb23 is T or N;

[0250] Xb25 is T or S;

[0251] Xb26 is V or F;

[0252] Xb27 is A or G; and

[0253] Xb28 is T or S;

[0254] (iv) the amino acid sequence of formula X is:

[0255] F-G-G-G-T-K-L-E-l-K (SEQ ID NO: 195)

[0256] (v) the amino acid sequence of formula XI is:

[0257] E-V-Q-L-Q-Q-S-G-P-E-L-V-K-P-G-A-Xb40-V-K-l-Xb44-C-K-A-S (XI) (SEQ ID NO: 200) wherein

[0258] Xb40 is A or S; and

[0259] Xb44 is S or P;

[0260] (vi) the amino acid sequence of formula XII is:

[0261] Xb47’-M-Xb49-W-V-K-Q-S-H-G-K-S-L-E-W-I-G-D-I (XII) (SEQ ID NO: 201) wherein

[0262] Xb47’ is D or N; and

[0263] Xb49 is N or D;

[0264] (vii) the amino acid sequence of formula XIII is:

[0265] Xb58-Xb59-Xb60-N-Xb61-K-F-K-G-K-A-T-L-T-V-D-K-S-S-S-T-A-Y-Xb76-E-L-R-S-L-T-S-E-D-Xb85-A-V-Y-Y-C-A-R

[0266] (XIII) (SEQ ID NO: 202) wherein

[0267] Xb58 is S or T;

[0268] Xb59 is R or L;

[0269] Xb60 is N or Y;

[0270] Xb61 is Q or R;

[0271] Xb76 is L or M; and Xb85 is T or S;

[0272] (viii) the amino acid sequence of formula XIV is:

[0273] W-G-Q-G-T-Xb88-Xb89-T-V-S-S (XIV) (SEQ ID NO: 196) wherein

[0274] Xb88 is T or S; and

[0275] Xb89 is L or V; or

[0276] (ix) a combination of at least two of (i) to (viii).

[0277] Item 8. The anti-S LAM F6 antibody or antigen-binding fragment thereof of any one of items 1 to 7, comprising the following framework regions (FRs): (i) a light chain FR1 comprising one of the following amino acid sequences: DIVMTQSHKFMSTSVGDRVSITC (SEQ ID NO: 18), DIQMTQSSSSFSVSLGDRVTITC (SEQ ID NO: 60) or DIQMTQSPASLSVSVGETVTITC (SEQ ID NO: 102); (ii) a light chain FR2 comprising one of the following amino acid sequences: WYQQKPGQSPKLLIY (SEQ ID NO: 24), WYQQKPGNAPRLLIS (SEQ ID NO: 66) or WYQQKQGKSPQLLVY (SEQ ID NO: 108); (iii) a light chain FR3 comprising one of the following amino acid sequences: GVPDRFTGSGSGTDYTLTISSVQAEDLALYYC (SEQ ID NO: 29),

[0278] GVPSRFSGSGSGKDYTLSITSLQTEDVATYYC (SEQ ID NO: 71) or GVPSRFSGSGSGTQYSLKINSLQSEDFGSYYC (SEQ ID NO: 113); (iv) a light chain FR4 comprising one of the following amino acid sequences: FGSGTKLEIK (SEQ ID NO: 34), FGGGTKLEIK (SEQ ID NO: 76) or FGGGTKLEIK (SEQ ID NO: 76); (v) a heavy chain FR1 comprising one of the following amino acid sequences: QVTLKESGPGILQPSQTLSLTCSFS (SEQ ID NO: 37), EVQLQQSGPELVKPGAAVKISCKAS (SEQ ID NO: 79) or EVQLQQSGPELVKPGASVKIPCKAS (SEQ ID NO: 119); (vi) a heavy chain FR2 comprising one of the following amino acid sequences: GVGWIRQPSGKGLEWLAHI (SEQ ID NO: 44), DMNWVKQSHGKSLEWIGDI (SEQ ID NO: 86) or NMDWVKQSHGKSLEWIGDI (SEQ ID NO: 124); (vii) a heavy chain FR3 comprising one of the following amino acid sequences: KYYNPALKSRLTISKDTSKNQVFLKIANVDTADTATYYCAP (SEQ ID NO: 52),

[0279] SRNNQKFKGKATLTVDKSSSTAYLELRSLTSEDSAVYYCAR (SEQ ID NO: 94) or

[0280] TLYNRKFKGKATLTVDKSSSTAYMELRSLTSEDTAVYYCAR (SEQ ID NO: 131); (viii) a heavy chain FR4 comprising one of the following amino acid sequences: WGQGTTLTVSS (SEQ ID NO: 58), WGQGTSVTVSS (SEQ ID NO: 100) or WGQGTTLTVSS (SEQ ID NO: 58); or (ix) at least two of (i) to (viii), preferably at least three, four, five, six, seven or all eight of (i) to (viii).

[0281] Item 9. The anti-SLAMF6 antibody or antigen-binding fragment thereof of any one of items 1 to 8, comprising the following framework regions (FRs):

[0282] (a) (i) a light chain FR1 comprising amino acid sequence DIVMTQSHKFMSTSVGDRVSITC (SEQ ID NO: 18);

[0283] (ii) a light chain FR2 comprising amino acid sequence WYQQKPGQSPKLLIY (SEQ ID NO: 24); (iii) a light chain FR3 comprising amino acid sequence GVPDRFTGSGSGTDYTLTISSVQAEDLALYYC (SEQ ID NO: 29); (iv) a light chain FR4 comprising amino acid sequence FGSGTKLEIK (SEQ ID NO: 34); (v) a heavy chain FR1 comprising amino acid sequence QVTLKESGPGILQPSQTLSLTCSFS (SEQ ID NO: 37); (vi) a heavy chain FR2 comprising amino acid sequence GVGWIRQPSGKGLEWLAHI (SEQ ID NO: 44); (vii) a heavy chain FR3 comprising amino acid sequence KYYNPALKSRLTISKDTSKNQVFLKIANVDTADTATYYCAP (SEQ ID NO: 52); (viii) a heavy chain FR4 comprising amino acid sequence WGQGTTLTVSS (SEQ ID NO: 58); or (ix) at least two of (i) to (viii), preferably at least three, four, five, six, seven or all eight of (i) to (viii);

[0284] (b) (i) a light chain FR1 comprising amino acid sequence DIQMTQSSSSFSVSLGDRVTITC (SEQ ID NO: 60); (ii) a light chain FR2 comprising amino acid sequence WYQQKPGNAPRLLIS (SEQ ID NO: 66); (iii) a light chain FR3 comprising amino acid sequence GVPSRFSGSGSGKDYTLSITSLQTEDVATYYC (SEQ ID NO: 71); (iv) a light chain FR4 comprising amino acid sequence FGGGTKLEIK (SEQ ID NO: 76); (v) a heavy chain FR1 comprising amino acid sequence EVQLQQSGPELVKPGAAVKISCKAS (SEQ ID NO: 79); (vi) a heavy chain FR2 comprising amino acid sequence DMNVWKQSHGKSLEWIGDI (SEQ ID NO: 86); (vii) a heavy chain FR3 comprising amino acid sequence SRNNQKFKGKATLTVDKSSSTAYLELRSLTSEDSAVYYCAR (SEQ ID NO: 94); (viii) a heavy chain FR4 comprising amino acid sequence WGQGTSVTVSS (SEQ ID NO: 100); or (ix) at least two of (i) to (viii), preferably at least three, four, five, six, seven or all eight of (i) to (viii); or

[0285] (c) (i) a light chain FR1 comprising amino acid sequence DIQMTQSPASLSVSVGETVTITC (SEQ ID NO: 102); (ii) a light chain FR2 comprising amino acid sequence WYQQKQGKSPQLLVY (SEQ ID NO: 108); (iii) a light chain FR3 comprising amino acid sequence GVPSRFSGSGSGTQYSLKINSLQSEDFGSYYC (SEQ ID NO: 113); (iv) a light chain FR4 comprising amino acid sequence FGGGTKLEIK (SEQ ID NO: 76); (v) a heavy chain FR1 comprising amino acid sequence EVQLQQSGPELVKPGASVKIPCKAS (SEQ ID NO: 119); (vi) a heavy chain FR2 comprising amino acid sequence NMDVWKQSHGKSLEWIGDI (SEQ ID NO: 124); (vii) a heavy chain FR3 comprising amino acid sequence TLYNRKFKGKATLTVDKSSSTAYMELRSLTSEDTAVYYCAR (SEQ ID NO: 131); (viii) a heavy chain FR4 comprising amino acid sequence WGQGTTLTVSS (SEQ ID NO: 58); or (ix) at least two of (i) to (viii), preferably at least three, four, five, six, seven or all eight of (i) to (viii).

[0286] Item 10. The anti-SLAMF6 antibody or antigen-binding fragment thereof of any one of items 1 to 9, comprising a light chain variable region (VL) comprising the amino acid sequence set forth in SEQ ID NO: 138, 146 or 154, preferably 146 or 154.

[0287] Item 11. The anti-SLAMF6 antibody or antigen-binding fragment thereof of any one of items 1 to 10, comprising a heavy chain variable region (VH) comprising the amino acid sequence set forth in SEQ ID NO: 140, 148 or 156, preferably 148 or 156.

[0288] Item 12. The anti-SLAMF6 antibody or antigen-binding fragment thereof of any one of items 1 to 11 , comprising at least one constant domain or a fragment thereof, which preferably comprises a Fragment crystallizable (Fc) fragment of a heavy chain constant region of an antibody.

[0289] Item 13. The anti-SLAMF6 antibody or antigen-binding fragment thereof of any one of items 1 to 12, wherein the antibody is a fully human antibody or a chimeric antibody, preferably wherein the antibody is an lgG1 antibody.

[0290] Item 14. The anti-SLAMF6 antibody or antigen-binding fragment thereof of any one of items 1 to 13, for enhancing T cell activation and / or for preventing T cell exhaustion and / or for increasing the proportion of T cells infiltrating tumors and / or for reducing tumor growth. Item 15. The anti-SLAMF6 antibody or antigen-binding fragment thereof of any one of items 1 to 14, wherein enhanced T cell activation includes enhanced T cell proliferation, enhanced production of cytokines interleukin-2 (IL-2) and / or enhanced production of interferon-y (IFN-y).

[0291] Other objects, advantages and features of the present disclosure will become more apparent upon reading of the following non-restrictive description of specific embodiments thereof, given by way of example only with reference to the accompanying drawings.

[0292] BRIEF DESCRIPTION OF THE DRAWINGS

[0293] In the appended drawings:

[0294] FIGs. 1A-F. Lack of SLAMF6 in human T cells promote T cell activation. (FIG. 1A) In vitro activation assay of human CD8+T cells lacking SLAMF6. Human peripheral blood CD8+T cells were electroporated either with non-targeting (control; Ctrl) or three different SLAMF6-targeting sgRNA / Cas9 RNPs. After cell sorting, lack of SLAMF6 expression was confirmed by flow cytometry. (FIG. 1 B) Variants of human CD8+T cells were activated in vitro with the indicated concentrations of anti-human CD3 mAb OKT3 (0, 0.1 , 0.3 pg mH). After 48 hours, proliferation was assessed by measuring [3H]-thymidine incorporation into cellular DNA, while production of IL-2 and IFN-y was quantified by ELISA of the culture supernatants. CPM, in counts per minute; IL, interleukin; IFN, interferon. (FIG. 1 C) Same as (FIG. 1A), except that flow cytometry analyses of expression of SLAMF6 on variants of Jurkat cells. Shaded histograms represent isotype control staining. (FIG. 1 D) Variants of Jurkat cells were activated with the indicated concentrations of anti-CD3 mAb OKT3 or PMA (100 ng mH) plus ionomycin (1 pg mH) (P + 1). After 48 hours, production of IL-2 was determined by ELISA. (FIG. 1 E) Variants of Jurkat cells were loaded with lndo-1 and stimulated with anti-TC Ra[3 mAb (0.5 pg mb1) or ionomycin (1 pg mH). Changes in intracellular calcium were determined by ascertaining the fluorescence UV450 / UV530 ratio (FL4 / FL5), with a BD LSR flow cytometer. Arrowheads indicate when the stimulus was added. (FIG. 1 F) Variants of Jurkat cells were incubated for 0 and 2.5 min with biotinylated anti-TCRa|3 mAbs (2 pg mH), followed by avidin (5 pg mH). Phosphotyrosine (P.tyr)-containing proteins were detected by immuno- blotting of total cell lysates with anti (a)-P.tyr mAbs (FIG. 1A). |3-actin was studied in parallel as loading control. The positions of molecular mass markers are shown on the right. Data are representative of 3 in (FIGs. A, C, E and F); each symbol in (FIG. 1 B) represents an individual human sample; results are pooled from three independent experiments in (FIGs. 1 B and D). Error bars represent means with SD. *P < 0.05, **P < 0.01 , ***P < 0.001, ****P < 0.0001, not significant (ns) P > 0.05 (two-sided unpaired Student’s t tests).

[0295] FIGs. 2A-B. Anti-human SLAMF6 mAbs disrupt SLAMF6-SLAMF6 cis interactions. (FIG. 2A) FRET analysis of cis SLAMF6-SLAMF6 interactions. The leftmost cartoon depicts a 293T cell expressing SNAP-hSLAMF6 and CLIP- hSLAMF6. CLIP-hSLAMF6 was labelled with CLIP-Surface 547 (energy donor), while SNAP-hSLAMF6 was labelled with SNAP-Surface 647 (energy acceptor). On the immediate right are pre- and post-bleaching confocal images of a representative condition, followed by the calculated FRET efficiency image (purple to yellow spectrum means weak to strong FRET). The rightmost images are differential interference contrast (DIC) images. The second to eighth row are the same as the first row, except in the presence of hSLAMF6 mAb NT-7 (third row), Fc-silent hSLAMF6 mAbs clone 5, 11 , 21 , 22 or 23 (fourth to eighth row) or Fc-silent Ctrl IgG (MOPC21, second row). (FIG. 1 B) The bar graph summarizes the FRET efficiencies, n=14 cells from 3 independent experiments. Scale bars, 5 pm. Each symbol in (FIG. 2B) represents an individual 293T cell; results are pooled from three independent experiments in (FIG. 2B). Error bars represent means with SD. *P < 0.05, **P < 0.01, ***P < 0.001 , ****P < 0.0001 , not significant (ns) P > 0.05 (two- sided unpaired Student’s t tests).

[0296] FIGs. 3A-B. Anti-human SLAMF6 mAbs promote T cell activation in vitro. (FIG. 3A) Human CD8- T cells were enriched from healthy donor peripheral blood and activated with the indicated concentrations of anti-human CD3 Abs (OKT3, 0, 0.1, and 0.3 pg mH) in the absence or presence of hSLAMF6 mAb NT-7, Fc-silent hSLAMF6 mAbs clone 5, 11 , 21 , 22 or 23 or Fc-silent Ctrl IgG (MOPC21). After 48 hours, proliferation was assessed by measuring [3H]-thymidine incorporation, while production of IL-2 and IFN-y was quantified by ELISA. CPM, in counts per minute; IL, interleukin; IFN, interferon. (FIG. 3B) Same as (FIG. 3A), except that previously activated human CD8+T cells were analyzed. Each symbol in (FIG. 3A) and (FIG. 3B) represents an individual human sample; results are pooled from three independent experiments in (FIG. 3A) and (FIG. 3B). Error bars represent means with SD. *P s 0.05, **P s 0.01 , ***P < Q QQI , ****p < 0.0001 , not significant (ns) P > 0.05 (two-sided unpaired Student’s t tests).

[0297] FIGs. 4A-E. Blocking anti-human SLAMF6 mAbs inhibit tumor growth in vivo. (FIG. 4A) Depiction of the protocol used for FIGs. 4A-E. SLAMF6 knockout (KO) OT-I CD8+T cells were transduced with retroviruses encoding human SLAMF6 and transplanted into EG7 tumor-bearing wild-type (WT) mice (n = 8 per group). EG7 tumor-bearing mice were treated with Fc-silent Ctrl IgG (MOPC21), or Fc-silent hSLAMF6 mAbs clone 21 or clone 23. (FIG. 4B) Tumor growth was measured by caliper every day. Dotted lines show values from individual mice; solid lines represent mean values. (FIGs. 4C-E) Tumors were dissected, measured (FIG. 4C), weighted (FIG. 4D) and analyzed by flow cytometry (FIG. 4E) on day 15. The bar graph in (FIG. 4E) shows the percentage of tumor-infiltrating donor CD8+T cells (TILs) for each mouse. Each symbol in (FIG. 4C) to (FIG. 4E) represents an individual mouse; results are pooled from two independent experiments in (FIG. 4A) to (FIG. 4E). Statistical significance was calculated with two-way analysis of variance (ANOVA) followed by Tukey’s multiple comparisons test with P values noted in (FIG. 4B). Error bars represent means with SD. *P < 0.05, **P < 0.01, ***P < 0.001 , ****P < 0.0001 , not significant (ns) P > 0.05 (two-sided unpaired Student’s t tests).

[0298] FIGs. 5A-J: Blocking SLAMF6 mAbs prevent T cell exhaustion in vivo. (FIGs. 5A-D) Flow cytometry analyses showing the frequencies of TCF- TI M-3- (FIG. 5A), TCF-1 TIM-3* (FIG. 5B), TCF-1 -Tl M-3- (FIG. 5C) and PD- TI M-3- (FIG. 5D) OT-I CD8- T cells among total tumor-infiltrating OT-I CD8+T cells. (FIG. 5E-G) Flow cytometry analyses showing the expression of Tox (FIG. 5E), TIGIT (FIG. 5F) and LAG-3 (FIG. 5G) expression in tumor-infiltrating OT-I CD8+T cells. (FIGs. 5H-J): in vitro exhausted (Ex) and non-exhausted (Non-ex) OT-I CD8+T cells were injected into E.G7 tumor-bearing WT mice. (FIG. 5H)Tumor volumes over time. Dotted lines show values from individual mice; solid lines represent mean values. (FIG. 5I) When tumors were dissected, OT-I CD8+ T cells were enumerated by flow cytometry (upper graph), and intracellular accumulation of IFN-y and TNF-ot was analyzed (lower graph). (FIG. 5J) Flow cytometry analyses showing the frequencies of TCF-1 -TIM-3- (upper left graph), TCF-1 TIM-3- (lower right graph), TCF-1 -Tl M-3- (upper right graph) and PD-1 -TIM-3- (lower right graph) OT-I CD8- T cells among total tumor-infiltrating OT-I CD8- T cells. Numbers in plots in (FIGs. 5A-D, I, J) indicate percentages of positive cells. Numbers in histograms in (FIGs. 5E-G) indicate MFI. In (FIGs. 5H-J), n = 6 mice per group, except for the group injected with exhausted OT-I CD8+T cells and treated with Ctrl IgG MOPC-21, in which n = 7. Each symbol represents an individual mouse; results are pooled from two independent experiments in (FIGs. 5A-J). Error bars represent means with s.d. *P < 0.05, **P < 0.01 , ***P < 0.001 , ****P < 0.0001, ns P > 0.05, not significant. Statistical significance was determined using two-sided unpaired Student’s t tests, except two-way analysis of variance (ANOVA) followed by Tukey’s multiple comparisons test with P values in (FIG. 5H).

[0299] FIGs. 6A-G: Blocking SLAMF6 mAbs promote anti-tumor immunity in a non-TCR transgenic tumor model. Polyclonal SLAMF6 KO CD8+ T cells transduced with human SLAMF6 were injected into Rag-1- / - mice carrying MC-38 colon carcinoma tumors. Mice were treated with blocking SLAMF6 mAb #21 , blocking PD-L1 mAb 10F.9G2 (Fc-active), both or control MOPC-21 (MOPC). (FIG. 6A) Schematic timeline of the in vivo experiment. (FIG. 6B) Tumor volumes over time. Dotted lines show values from individual mice; solid lines represent mean values. (FIG. 6C) Frequency of tumorinfiltrating CD8- T cells. Tumor-infiltrating CD8+ T cells with percentages are in ellipses. (FIG. 6D) Flow cytometry analyses showing intracellular accumulation of IFN-y and TNF-a in tumor-infiltrating CD8+T cells. (FIGs. 6E-F) Flow cytometry analysis showing frequencies of TCF-1 Tim-3+CD8- T cells (FIG. 6E) or PD-1+Tim-3+CD8- T cells (FIG. 6F). (FIG. 6G) Flow cytometry analyses for expression of Tox, TIGIT and LAG-3 in tumor-infiltrating CD8+ T cells. Numbers in plots in (FIGs. 6C-F) indicate percentages of positive cells. Numbers in histograms in (FIG. 6G) indicate MFI. In FIGs. 6C-G, n = 9 mice (Ctrl IgG MOPC), n = 8 mice (PD-L1 mAb 10F.9G2), n = 10 mice (SLAMF6 mAb #21), and in FIGs. 6B-G n = 8 mice (10F.9G2 + #21). Each symbol in FIGs. 6C-G represents an individual tumor-bearing mouse; error bars represent mean with s.d. Error bars represent means with s.d. *P < 0.05; **P < 0.01 ; ***P < 0.001 ; ****P < 0.0001; ns P> 0.05, not significant. For statistical analyses, unpaired t-tests were used in FIGs. 6C-G, whereas two-way analysis of variance (ANOVA) followed by Tukey’s multiple comparisons test was used in FIG. 6B Data are representative of 2 (FIGs. 6B-G) independent experiments.

[0300] FIGs. 7A-B: Blocking SLAMF6 mAbs rescue T cell exhaustion in vivo. OT-I CD8+T cells were exhausted in vitro by repeated stimulation with OVA peptide, as detailed for FIGs. 5H-J. (FIG. 7A) Depiction of protocol. (FIG. 7B) Flow cytometry analyses showing the expression of Tox (left graph), TIGIT (middle graph) and LAG-3 (right graph) in OT-I CD8+T cells injected into E.G7 tumor-bearing WT mice. In FIG. 7B, n = 6 mice per group, except for the group injected with exhausted OT-I CD8+T cells and treated with Ctrl IgG MOPC-21 , in which n = 7. Representatives of two independent experiments are shown FIG. 7B. Each symbol represents an individual mouse; results are pooled from two independent experiments in FIG. 7B. Error bars represent means with s.d. *P < 0.05, **P < 0.01 , ***P < 0.001 , ****P < 0.0001 , ns P > 0.05, not significant. Statistical significance was determined using two-sided unpaired Student’s t tests.

[0301] FIGs. 8A-D: SLAMF6 blockade reinvigorates chronically stimulated T cells. (FIG. 8A) Protocol. Human CD8+ T cells lacking or not SLAMF6 were repeatedly stimulated with CD3 mAb OKT3 (3 pg mL-1) and IL-2 (10 ng mL-1). (FIG. 8B) Flow cytometry analyses showing intracellular accumulation of IFN-y and TNF-a in WT and SLAMF6 KO CD8+ T cells following re-stimulation with CD3 mAb OKT3 in the presence of indicated SLAMF6 mAbs. (FIGs. 8C-D) Expression of Tim-3 and TCF-1 (FIG. 8C), or PD-1 , Tox or LAG-3 (FIG. 8D) was determined by flow cytometry. Numbers in plots in (FIGs. 8B-C) indicate percentages of cells. Numbers in histograms in (FIG. 8D) indicate MFI. In FIGs. 8B-D, a representative experiment is shown on the left, while data from multiple mice are depicted on the right. Each symbol in FIGs. 8B-D represents an individual blood donor; error bars represent mean with s.d. Error bars represent means with s.d. *P < 0.05; **P < 0.01 ; ***P < 0.001 ; ****P < 0.0001 ; ns P> 0.05, not significant. For statistical analyses, unpaired t-tests were used in b-d. Data are representative of 3 (b-d) independent experiments.

[0302] FIGs. 9A-E. (FIG. 9A) Amino acid sequences of human SLAMF6 isoforms 1 and 2 (SEQ ID NOs: 2-3). (FIG. 9B) Alignment of amino acid sequences for the variable light chains of mAb clones 5, 21 , and 23 and their consensus sequence (SEQ ID NOs: 4, 5, 6 and 7). (FIG. 9C) Alignment of amino acid sequences for the variable light chains of mAb clones 21, and 23 and their consensus sequence (SEQ ID NOs: 8, 9 and 10). (FIG. 9D) Alignment of amino acid sequences for the variable heavy chains of mAb clones 5, 21, and 23 and their consensus sequence (SEQ ID NOs: 11, 12, 13 and 14). (FIG. 9E) Alignment of amino acid sequences for the variable heavy chains of mAb clones 21 , and 23 and their consensus sequence (SEQ ID NOs: 15, 16 and 17). CDRs are underlined in (FIGs. 9B-E).

[0303] DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0304] Definitions

[0305] For clarity, definitions of the following terms in the context of the present invention are provided.

[0306] The use of the terms "a" and "an" and "the" and similar referents in the context of describing the technology (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context.

[0307] The terms "comprising", "having", "including", and "containing" are to be construed as open-ended terms (i.e., meaning "including, but not limited to") unless otherwise noted.

[0308] All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context.

[0309] The use of any and all examples, or exemplary language (“e.g.”, "such as") provided herein, is intended merely to better illustrate embodiments of the claimed technology and does not pose a limitation on the scope unless otherwise claimed.

[0310] No language in the specification should be construed as indicating any non-claimed element as essential to the practice of embodiments of the claimed technology.

[0311] Herein, the term "about" has its ordinary meaning. The term “about” is used to indicate that a value includes an inherent variation of error for the device or the method being employed to determine the value, or encompass values close to the recited values, for example within 10% of the recited values (or range of values).

[0312] Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All subsets of values within the ranges are also incorporated into the specification as if they were individually recited herein. Where features or aspects of the disclosure are described in terms of Markush groups or list of alternatives, those skilled in the art will recognize that the disclosure is also thereby described in terms of any individual member, or subgroup of members, of the Markush group or list of alternatives.

[0313] Unless specifically defined otherwise, all technical and scientific terms used herein shall be taken to have the same meaning as commonly understood by one of ordinary skill in the art (e.g., in stem cell biology, cell culture, molecular genetics, immunology, immunohistochemistry, protein chemistry, and biochemistry).

[0314] Unless otherwise indicated, the techniques utilized in the present disclosure are standard procedures, well known to those skilled in the art. Such techniques are described and explained throughout the literature in sources such as, J. Perbal, A Practical Guide to Molecular Cloning, John Wiley and Sons (1984), J. Sambrook et al., Molecular Cloning: A Laboratory Manual, Cold Spring Harbour Laboratory Press (1989), T. A. Brown (editor), Essential Molecular Biology: A Practical Approach, Volumes 1 and 2, IRL Press (1991), D. M. Glover and B. D. Hames (editors), DNA Cloning: A Practical Approach, Volumes 1-4, IRL Press (1995 and 1996), and F. M. Ausubel et al. (editors), Current Protocols in Molecular Biology, Greene Pub. Associates and Wiley-lnterscience (1988, including all updates until present), Ed Harlow and David Lane (editors) Antibodies: A Laboratory Manual, Cold Spring Harbour Laboratory, (1988), and J. E. Coligan et al. (editors) Current Protocols in Immunology, John Wiley & Sons (including all updates until present).

[0315] The present disclosure shows that inhibiting SLAMF6 suppresses the growth of tumor cells in vivo. The present disclosure also shows that this activity is mediated by enhancing T cell activation in naive and in activated T cells, through blocking cis SLAMF6-SLAMF6 interactions on T cells which in turns positively regulates T cell activation. This activity is independent of expression of SLAMF6 on tumor cells.

[0316] Accordingly, the present disclosure provides SLAM F6-binding molecules that enhance T cell activation and suppress tumor cell growth. The present disclosure also provides a method for enhancing T cell activation in a subject (e.g., a human subject), comprising contacting T cells with the SLAM F6-binding molecule. The present disclosure also provides a method for reducing the growth of tumor cells in a subject (e.g., a human subject), comprising administering a S LAM F6-bindi n g molecule to the subject, whereby tumor cells growth is reduced. The present disclosure also provides the use of a SLAMF6-binding molecule for (or in the manufacture of a medicament for) enhancing T cell activation in a subject (e.g., a human subject). The present disclosure also provides the use of a S LAM F6-binding molecule for (or in the manufacture of a medicament for) reducing the growth of tumor cells in a subject (e.g., a human subject).

[0317] SLAMF6, also referred to as Ly108, NTB-A or CD352, is a homophilic SLAM Family Receptor (SFR) expressed on T cells, natural killer (NK) cells, B cells, and dendritic cells (Lu et al. 2019; Wu et al. 2016). Within T cells, it is constitutively expressed on naive T cells. Human SLAMF6 isoforms are depicted in FIG. 9A.

[0318] As used herein, the term “enhancing T cell activation” refers to, without being so limited, and can be determined by one or more of enhanced T cell proliferation, enhanced production of cytokines interleukin-2 (IL-2), enhanced production of interferon-y (IFN-y), enhanced calcium fluxes, augmented overall protein tyrosine phosphorylation, reduced tumor growth, enhanced production of IFN-gamma, and enhanced cytotoxicity. As used herein “T cell exhaustion” is a state of immune dysfunction and a progressive loss of T cell function that occurs in response to chronic antigen stimulation, such as during chronic viral infections or cancer. It is characterized by features like reduced proliferation, impaired cytokine production and cytotoxicity, sustained expression of inhibitory receptors (like PD-1), and altered transcriptional and epigenetic profiles. This state prevents effective control of infections and tumors.

[0319] As used herein “blocking cis SLAMF6-SLAMF6 interaction” is meant to refer to blocking SLAMF6-SLAMF6 interaction on the same cell type (i.e. T cells).

[0320] As used herein, the term “SLAMF6-binding molecule” refers to any molecule capable of binding to SLAMF6, reducing cis SLAMF6-SLAMF6 interaction which in turns positively regulates T cell activation and enhances T cell activation. The term “binding molecule” encompasses “antibodies or antigen-binding fragments thereof”. The term “antibodies or antigen-binding fragments thereof” encompasses monoclonal antibodies (including full-length monoclonal antibodies), polyclonal antibodies, multispecific antibodies (e.g., bispecific antibodies), humanized antibodies, CDR-grafted antibodies, chimeric antibodies, multispecific antibodies (e.g., bispecific antibodies), and fragments thereof so long as they exhibit the desired antigenic specificity / binding activity. The term “binding molecule” also encompasses adnectins; affibodies; affilins; affimers; affitins; alphabodies; antibody mimetics; anticalins; aptamers; armadillo repeat proteinbased scaffolds; atrimers; avimers; DARPins; fynomers; knottins; Kunitz domain peptides; monobodies; nanofitins; peptides; and small molecules (e.g., compounds with molecular weights of less than 1000 Daltons). The ability of the SLAM F6-binding molecule to reduce / inhibit cis SLAMF6-SLAMF6 interactions and / or enhance T cell activation may be assessed using methods / assays known in the art, for example using a FRET-based assay as described in the Examples below.

[0321] Antibody fragments comprise a portion of a full-length antibody, generally an antigen binding or variable region thereof. Examples of antibody fragments include Fab, Fab', F(ab')2, and Fv fragments, diabodies, linear antibodies, single-chain antibody molecules (e.g., single-chain FV, scFV), single domain antibodies (e.g., from camelids), shark NAR single domain antibodies, and multispecific antibodies formed from antibody fragments. Antibody fragments can also refer to binding moieties comprising CDRs or antigen binding domains including, but not limited to, VH regions (VH, VH-VH), anticalins, PepBodies, antibody-T-cell epitope fusions (Troybodies) or Peptibodies.

[0322] The term "monoclonal antibody" as used herein refers to an antibody derived from a population of substantially homogeneous antibodies. This means that the individual antibodies within the population are substantially similar, and bind to the same epitope(s), with the exception of minor variants that may occur during the production of the monoclonal antibody. Typically, such a monoclonal antibody includes an antibody with a variable region that specifically binds to a target, and it is obtained through a selection process involving the identification of the antibody from a larger group of antibodies. For instance, this selection process may involve isolating a unique clone from a collection of clones, such as those from hybridoma, phage display, or recombinant DNA techniques. It is important to note that the selected antibody can undergo further modifications to enhance its affinity for the target, humanize the antibody, improve its production in cell culture, reduce its immunogenicity in vivo, or create a multispecific antibody. An antibody that possesses an altered variable region sequence also qualifies as a monoclonal antibody within the scope of this invention. In addition to their specificity, monoclonal antibody preparations are typically free from contamination by other immunoglobulins. The term "monoclonal" denotes that the antibody originates from a largely homogeneous population and should not be interpreted as necessitating a specific production method. Indeed, the monoclonal antibodies utilized in this invention may be generated through various techniques, including the hybridoma method and methods for producing human or human-like antibodies from animals possessing part or all of the human immunoglobulin loci or genes encoding human immunoglobulin sequences known in the field.

[0323] The monoclonal antibodies herein specifically include "chimeric" or “recombinant” antibodies in which a portion of the light and / or heavy chain is identical with or homologous to corresponding sequences in antibodies derived from a particular species or belonging to a particular antibody class or subclass, while the remainder of the chain(s) is identical with or homologous to corresponding sequences in antibodies derived from another species or belonging to another antibody class or subclass, as well as fragments of such antibodies, so long as they exhibit the desired biological activity. Chimeric antibodies of interest herein include "humanized" antibodies.

[0324] In an embodiment, the SLAMF6-binding molecule, e.g., antibody or antigen-binding fragment thereof, binds to an Ig like domain defined by residues 35 to 120 of human SLAMF6 or to an epitope within this domain. The amino acid sequence of human SLAMF6 isoforms are depicted in FIG. 9A (SEQ ID NO:2; or SEQ ID NO:3), with the above-noted residues in bold and underlined. The results of the studies described herein (see, e.g., FIGs. 2A-B, 3A-B and 4A-F) show that an antibody recognizing the above-noted domain or epitope is able to dissociate the cis SLAMF6-SLAMF6 interaction and activate T cells, and thus any SLAM F6-binding molecule binding to the same domain or epitope is expected to have the ability to interfere with the cis SLAMF6-SLAMF6 interaction and activate T cells.

[0325] In an embodiment, the SLAMF6-binding molecule is an antibody or an antigen-binding fragment thereof, and it comprises the complementary determining regions (CDRs) of antibodies 5, 21 or 23 described in the present Application. The amino acid sequences of the light and heavy chain variable regions of antibodies 5, 21 and 23 are depicted in Tables VII below and FIGs. 9B-E. In FIGs. 9B-E, the residues defining the light chain and heavy chain CDRs (CDR1 , CDR2 and CDR3) are indicated. The term "complementarity determining regions" or "CDRs" when used herein refers to parts of immunological receptors that make contact with a specific ligand (SLAMF6) and determine its specificity. The CDRs of immunological receptors are the most variable part of the receptor protein, giving receptors their diversity, and are carried on six loops at the distal end of the receptor's variable domains, three loops coming from each of the two variable domains of the receptor.

[0326] In an embodiment, the antibody or antigen-binding fragment thereof comprises the following CDRs: a light chain CDR1 comprising or consisting of an amino acid sequence having at least 70%, 75%, 80%, 85%, 90% or 95% identity with any one of the CDR-L1 amino acid sequences shown in Tables I, III and V below, a light chain CDR2 comprising or consisting of an amino acid sequence having at least 70%, 75%, 80%, 85%, 90% or 95% identity with any one of the CDR-L2 amino acid sequences shown in Tables I, III and V below, a light chain CDR3 comprising or consisting of an amino acid sequence having at least 70%, 75%, 80%, 85%, 90% or 95% identity with any one of the CDR-L3 amino acid sequences shown in Tables I, III and V below, a heavy chain CDR1 comprising or consisting of an amino acid sequence having at least 70%, 75%, 80%, 85%, 90% or 95% identity with any one of the CDR-H1 amino acid sequences shown in Tables II, IV and VI below, a heavy chain CDR2 comprising or consisting of an amino acid sequence having at least 70%, 75%, 80%, 85%, 90% or 95% identity with any one of the CDR-H2 amino acid sequences shown in Tables II, IV and VI below, and a heavy chain CDR3 comprising or consisting of an amino acid sequence having at least 70%, 75%, 80%, 85%, 90% or 95% identity with any one of the CDR-H3 amino acid sequences shown in Tables II, IV and VI below.

[0327] In an embodiment, one or two residues in one or more of the above-noted CDRs sequences are substituted. In a further embodiment, one residue in one or more of the above-noted CDRs sequences are substituted. Such substitutions may be useful for increasing the affinity of the antibody or antigen-binding fragment thereof for SLAMF6 (e.g., an affinity- matured antibody or antigen-binding fragment thereof) and / or for reducing non-specific binding.

[0328] In an embodiment, the antibody or antigen-binding fragment thereof comprises the following CDRs: a light chain CDR1 comprising or consisting of the CDR-L1 amino acid sequence shown in any one of Tables I, III and V, a light chain CDR2 comprising or consisting of the CDR-L2 amino acid sequence shown in any one of Tables I, III and V, a light chain CDR3 comprising or consisting of CDR-L3 amino acid sequence shown in any one of Tables I, III and V, a heavy chain CDR1 comprising or consisting of the CDR-H1 amino acid sequence shown in any one of Tables II, IV and VI, a heavy chain CDR2 comprising or consisting of the CDR-H2 amino acid sequence shown in any one of Tables II, IV and VI, and a heavy chain CDR3 comprising or consisting of the CDR-H3 amino acid sequence shown in any one of Tables II, IV and VI. In a further embodiment, the antibody or antigen-binding fragment thereof all the above-noted CDRs of Tables I and II, or of Tables III and IV or of Tables V and VI.

[0329] In an embodiment, the antibody or antigen-binding fragment thereof comprises the following framework regions (FRs): a light chain FR1 comprising an amino acid sequence having at least 50%, 60%, 70%, 75%, 80%, 85%, 90% or 95% identity with any one of the FR-L1 amino acid sequences shown in Tables I, III and V below, a light chain FR2 comprising an amino acid sequence having at least 50%, 60%, 70%, 75%, 80%, 85%, 90% or 95% identity with the any one of the FR-L2 amino acid sequences shown in Tables I, III and V below, a light chain FR3 comprising an amino acid sequence having at least 50%, 60%, 70%, 75%, 80%, 85%, 90% or 95% identity with any one of the FR-L3 amino acid sequences shown in Tables I, III and V below, a light chain FR4 comprising an amino acid sequence having at least 50%, 60%, 70%, 75%, 80%, 85%, 90% or 95% identity with any one of the FR-L4 amino acid sequences shown in Tables I, III and V below, a heavy chain FR1 comprising an amino acid sequence having at least 50%, 60%, 70%, 75%, 80%, 85%, 90% or 95% identity with any one of the FR-H1 amino acid sequences shown in Tables II, IV and VI below, a heavy chain FR2 comprising an amino acid sequence having at least 50%, 60%, 70%, 75%, 80%, 85%, 90% or 95% identity with any one of the FR-H2 amino acid sequences shown in Tables II, IV and VI below, a heavy chain FR3 comprising an amino acid sequence having at least 50%, 60%, 70%, 75%, 80%, 85%, 90% or 95% identity with any one of the FR-H3 amino acid sequences shown in Tables II, IV and VI below, and / or a heavy chain FR4 comprising an amino acid sequence having at least 50%, 60%, 70%, 75%, 80%, 85%, 90% or 95% identity with any one of the FR-H4 amino acid sequences shown in Tables II, IV and VI below.

[0330] In an embodiment, the antibody or antigen-binding fragment thereof comprises the following framework regions (FRs): a light chain FR1 comprising or consisting of any one of the FR-L1 amino acid sequences shown in Tables I, III and V below, a light chain FR2 comprising or consisting of any one of the FR-L2 amino acid sequences shown in Tables I, III and V below, a light chain FR3 comprising or consisting of any one of the FR-L3 amino acid sequences shown in Tables I, III and V below, a light chain FR4 comprising or consisting of any one of the FR-L4 amino acid sequences shown in Tables I, III and V below, a heavy chain FR1 comprising or consisting of any one of the FR-H1 amino acid sequences shown in Tables II, IV and VI below, a heavy chain FR2 comprising or consisting of any one of the FR-H2 amino acid sequences shown in Tables II, IV and VI below, a heavy chain FR3 comprising or consisting of any one of the FR-H3 amino acid sequences shown in Tables II, IV and VI below, and / or a heavy chain FR4 comprising or consisting of any one of the FR-H4 amino acid sequences shown in Tables II, IV and VI below. In a further embodiment, the antibody or antigen-binding fragment thereof all the above-noted FRs of Tables I and II, or of Tables III and IV or of Tables V and VI.

[0331] In an embodiment, the antibody or antigen-binding fragment thereof comprises a light chain variable region (VL) comprising an amino acid sequence having at least 50%, 60%, 70%, 75%, 80%, 85%, 90% or 95% identity with any amino acid sequences depicted in FIG. 9B. In an embodiment, the differences relative to the reference variable light chain sequence are within one or more of the FRs. In a further embodiment, the antibody or antigen-binding fragment thereof comprises a variable light chain comprising or consisting of any amino acid sequence depicted in FIG. 9B.

[0332] In an embodiment, the antibody or antigen-binding fragment thereof comprises a heavy chain variable region (VH) comprising an amino acid sequence having at least 50%, 60%, 70%, 75%, 80%, 85%, 90% or 95% identity with any amino acid sequences depicted in FIG. 9D. In an embodiment, the differences relative to the reference variable heavy chain sequence are within one or more of the FRs. In a further embodiment, the antibody or antigen-binding fragment thereof comprises a variable heavy chain comprising or consisting of any amino acid sequences depicted in FIG. 9D.

[0333] The sequences of the CDRs and FRs described herein are based on the numbering scheme of Chothia (Al-Lazikani et al., J Mol Biol. 1997 Nov 7;273(4):927-48). However, the skilled person would understand that the amino acids forming the CDRs and FRs regions in the sequences of antibodies 5, 21 and 23 may vary depending on the numbering scheme used. Tables I to VI below depict the sequences of the CDRs and FRs regions of antibodies 5, 21 and 23 according to commonly used antibody numbering schemes.

[0334] Table I: Predicted FR and CDR sequences in antibody 5 light chain variable region

[0335]

[0336] Table II: Predicted FR and CDR sequences in antibody 5 heavy chain variable region

[0337]

[0338] Table III: Predicted FR and CDR sequences in antibody 21 light chain variable region

[0339]

[0340] Table IV: Predicted FR and CDR sequences in antibody 21 heavy chain variable region

[0341] Table V: Predicted FR and CDR sequences in antibody 23 light chain variable region

[0342]

[0343] Table VI: Predicted FR and CDR sequences in antibody 23 heavy chain variable region

[0344] Variations in the antibodies or antigen-binding fragments thereof described herein, can be made, for example, using any of the techniques and guidelines for conservative and non-conservative mutations set forth, for instance, in U.S. Patent No. 5,364,934. Variations may be a substitution, deletion or insertion of one or more codons encoding the antibody that results in a change in the amino acid sequence as compared with the native sequence antibody. Optionally the variation is by substitution of at least one amino acid with any other amino acid in one or more of the domains of the anti-SLAMF6 antibody or antigen-binding fragment thereof. Guidance in determining which amino acid residue may be inserted, substituted or deleted without adversely affecting the desired activity may be found by comparing the sequence of the antibody or antigen-binding fragment thereof with that of homologous known protein molecules and minimizing the number of amino acid sequence changes made in regions of high homology. Amino acid substitutions can be the result of replacing one amino acid with another amino acid having similar structural and / or chemical properties, such as the replacement of a leucine with a serine, i.e., conservative amino acid replacements. Insertions or deletions may optionally be in the range of about 1 to 5 amino acids. The variation allowed may be determined by systematically making insertions, deletions or substitutions of amino acids in the sequence and testing the resulting variants for activity exhibited by the full-length or mature native sequence. In embodiment, the variant exhibit at least 50%, 55% or 60%, preferably at least 65, 70, 75, 80, 90, 95, 96, 97, 98 or 99% sequence identity with the sequence of the antibody or antigen-binding fragment thereof described herein, and maintain the ability to specifically bind to SLAMF6.

[0345] "Identity" refers to sequence identity between two polypeptides. Percent (%) sequence identity with respect to a reference polypeptide sequence is the percentage of amino acid residues in a candidate sequence that are identical with the amino acid residues in the reference polypeptide sequence, after aligning the sequences and introducing gaps, if necessary, to achieve the maximum percent sequence identity, and not considering any conservative substitutions as part of the sequence identity. Alignment for purposes of determining percent amino acid sequence identity can be achieved in various ways that are known for instance, using publicly available computer software such as BLAST, BLAST-2, ALIGN or Megalign (DNASTAR) software. Appropriate parameters for aligning sequences are able to be determined, including algorithms needed to achieve maximal alignment over the full length of the sequences being compared. For purposes herein, however, % amino acid sequence identity values are generated using the sequence comparison computer program ALIGN-2. The ALIGN-2 sequence comparison computer program was authored by Genentech, Inc., and the source code has been filed with user documentation in the U.S. Copyright Office, Washington D.C., 20559, where it is registered under U.S. Copyright Registration No. TXU510087. The ALIGN-2 program is publicly available from Genentech, Inc., South San Francisco, Calif., or may be compiled from the source code. The ALIGN-2 program should be compiled for use on a UNIX operating system, including digital UNIX V4.0D. All sequence comparison parameters are set by the ALIGN-2 program and do not vary.

[0346] In situations where ALIGN-2 is employed for amino acid sequence comparisons, the % amino acid sequence identity of a given amino acid sequence A to, with, or against a given amino acid sequence B (which can alternatively be phrased as a given amino acid sequence A that has or comprises a certain % amino acid sequence identity to, with, or against a given amino acid sequence B) is calculated as follows: 100 times the fraction X / Y, where X is the number of amino acid residues scored as identical matches by the sequence alignment program ALIGN-2 in that program's alignment of A and B, and where Y is the total number of amino acid residues in B. It will be appreciated that where the length of amino acid sequence A is not equal to the length of amino acid sequence B, the % amino acid sequence identity of A to B will not equal the % amino acid sequence identity of B to A. Unless specifically stated otherwise, all % amino acid sequence identity values used herein are obtained as described in the immediately preceding paragraph using the ALIGN-2 computer program.

[0347] In an embodiment, the anti-SLAMF6 antibody or antigen-binding fragment thereof comprises at least one constant domain, e.g., a constant domain of a light and / or heavy chain, or a fragment thereof. In a further embodiment, the anti- SLAMF6 antibody or antigen-binding fragment thereof comprises a Fragment crystallizable (Fc) fragment of the constant heavy chain of an antibody. The Fc fragment may comprise two or three constant domains, e.g., a CH2 domain and CH3 domain. The Fc region may be obtained from a human lgG1, a human lgG4, or a variant of a human lgG1 or I gG4 having up to ten amino acid modifications, for example. In an embodiment, the Fc fragment comprises or consists of the CH2 domain and CH3 domain of a human antibody, preferably a human IgG such as lgG1. In an embodiment, the anti-SLAMF6 antibody or antigen-binding fragment thereof comprises a light chain constant domain comprising at least 50%, 55% or 60%, preferably at least 65, 70, 75, 80, 90, 95, 96, 97, 98 or 99% sequence identity with the light chain constant domain amino acid sequence depicted in Table VII or VIII. In an embodiment, the anti-SLAMF6 antibody or antigen-binding fragment thereof comprises a light chain constant domain comprising the light chain constant domain amino acid sequence depicted in Table VII or VIII. In an embodiment, the anti-SLAMF6 antibody or antigen-binding fragment thereof comprises a heavy chain constant domain comprising at least 50%, 55% or 60%, preferably at least 65, 70, 75, 80, 90, 95, 96, 97, 98 or 99% sequence identity with the heavy chain constant domain amino acid sequence depicted in Table VII or VIII. In an embodiment, the anti-SLAMF6 antibody or antigen-binding fragment thereof comprises the heavy chain constant domain amino acid sequence depicted in Table VII or VIII.

[0348] Covalent modifications of antibodies or antigen-binding fragments thereof are included within the scope of this disclosure. Covalent modifications include reacting targeted amino acid residues of the antibody or antigen-binding fragment thereof with an organic derivatizing agent that is capable of reacting with selected side chains or the N- or C- terminal residues of the antibody or antigen-binding fragment thereof. Other modifications include deamidation of glutaminyl and asparaginyl residues to the corresponding glutamyl and aspartyl residues, respectively, hydroxylation of proline and lysine, phosphorylation of hydroxyl groups of seryl or threonyl residues, methylation of the a-amino groups of lysine, arginine, and histidine side chains (T.E. Creighton, Proteins: Structure and Molecular Properties, W.H. Freeman & Co., San Francisco, pp. 79-86 (1983)), acetylation of the N-terminal amine, and amidation of any C-terminal carboxyl group.

[0349] Other types of covalent modification of the antibody or antigen-binding fragment thereof included within the scope of this disclosure include altering the native glycosylation pattern of the antibody or antigen-binding fragment thereof (Beck et al., Curr. Pharm. Biotechnol. 9: 482-501, 2008; Walsh, Drug Discov. Today 15: 773-780, 2010) and linking the antibody or antigen-binding fragment thereof to one of a variety of nonproteinaceous polymers, e.g., polyethylene glycol (PEG), polypropylene glycol, or polyoxyalkylenes, in the manner set forth in U.S. Patent Nos. 4,179,337; 4,301 ,144; 4,496,689; 4,640,835; 4,670,417; or 4,791 ,192.

[0350] The SLAM F6-binding molecule (e.g., antibody or antigen-binding fragment thereof) may further comprise one or more modifications that confer additional biological properties to antibody or antigen-binding fragment thereof such as protease resistance, plasma protein binding, increased plasma half-life, intracellular penetration, etc. Such modifications include, for example, covalent attachment of molecules / moiety to the antibody or antigen-binding fragment thereof such as fatty acids (e.g., Ce-Cis), attachment of proteins such as albumin (see, e.g., U.S. Patent No. 7,268,113); sugars / polysaccharides (glycosylation), biotinylation or PEGylation (see, e.g., U.S. Patent Nos. 7,256,258 and 6,528,485). The above description of modification of the antibody or antigen-binding fragment thereof does not limit the scope of the approaches nor the possible modifications that can be engineered. Thus, in another aspect, the present disclosure provides a conjugate comprising the antibody or antigen-binding fragment thereof described herein and one or more additional molecules or agents (hereinafter secondary molecules or agents). The antibody or antigenbinding fragment thereof may be conjugated to any type of synthetic or natural secondary molecules or agents, such as peptides, proteins, saccharides / polysaccharides, lipids, naturally occurring or synthetic polymers / co-polymers, etc. to modify one or more properties of the antibody or antigen-binding fragment thereof.

[0351] In an embodiment, the conjugate comprises a covalent link or bond between the antibody or antigen-binding fragment thereof and the molecule conjugated thereto. The molecule may be conjugated directly to the antibody or antigenbinding fragment thereof, or indirectly via a linker. The linker may be a polypeptide linker comprising one or more amino acids or another type of chemical linker (e.g., a carbohydrate linker, a lipid linker, a fatty acid linker, a polyether linker, PEG, etc.

[0352] In an embodiment, the SLAMF6-binding molecule (e.g., antibody or antigen-binding fragment thereof) is labelled or conjugated with one or more moieties. The SLAMF6-binding molecule (e.g., antibody or antigen-binding fragment thereof) may be labeled with one or more labels such as a biotin label, a fluorescent label, an enzyme label, a coenzyme label, a chemiluminescent label, or a radioactive isotope label. In an embodiment, the antibody or antigen-binding fragment thereof is labelled with a detectable label, for example a fluorescent moiety (fluorophore). Useful detectable labels include fluorescent compounds (e.g., Alexa Fluor® dyes, fluorescein, fluorescein isothiocyanate, rhodamine, Texas red, etc.), radiolabels, enzymes (e.g., alkaline phosphatase, horseradish peroxidase, and others commonly used in a protein detection assays), and colorimetric labels such as colloidal gold, colored glass or plastic beads (e.g., polystyrene, polypropylene, latex, etc.). Chemiluminescent compounds may also be used. Such labelled antibodies or antigen-binding fragments thereof may be useful, for example, for the detection of SLAMF6 and / or SLAMF6-expressing cells in vivo or in vitro, e.g., by flow cytometry, immunohistochemistry, etc. The antibody or antigen-binding fragment thereof can also be conjugated to detectable or affinity tags that facilitate detection and / or purification of the antibody or antigen-binding fragment thereof. Such tags are well known in the art. Examples of detectable or affinity tags include alkaline phosphatase (AP), and horseradish peroxidase (HRP) tags (see, e.g., Kimple et al., Curr Protoc Protein Sci. 2013; 73: Unit-9.9), calmodulin binding peptide (CBP) tags, chloramphenicol acetyl transferase (CAT), epitope tags (such as FLAG, hemagglutinin (HA), HSV, S / S1 , c-myc, KT3, T7, V5, E2, and Glu-Glu epitope tags), glutathione S- transferase (GST) tags, HaloTag®, maltose binding protein (MBP) tags, polyarginine tags, polyaspartate tags, polycysteine tags, polyhistidine tags (His-tags), polyphenylalanine tags, Profinity eXact® tags, reporter tags such as P-galactosidase (|3-gal), and Streptavidin / Biotin-based tags.

[0353] The SLAMF6-binding molecule (e.g., antibody or antigen-binding fragment thereof) may alternatively or further be combined with the administration an antitumor agent (chemotherapeutic agent, toxin, radioisotope, etc.).

[0354] The antitumor agent may be any compound that has the ability to inhibit the growth and / or kill tumor cells and includes, for example, small molecules, peptides, proteins, oligonucleotides (e.g., siRNA, shRNA), radionuclide agents (e.g.,225Ac,221At,213Bi,18F,68Ga,111ln,177Lu,99mTc,227Thand90Y), as well as drug delivery systems including nanoparticles (e.g., lipid nanoparticles), liposomes, polymersomes, etc., loaded with a therapeutic antitumor agent. In an embodiment, the SLAMF6-binding molecule (e.g., antibody or antigen-binding fragment thereof) is part of a bispecific binding molecule (e.g., a bispecific antibody or antigen-binding fragment thereof). Exemplary bispecific formats that can be used in the context of the present disclosure include, without limitation, e.g., scFv-based or diabody bispecific formats, I gG-scFv fusions, dual variable domain (DVD)-lg, Quadroma, knobs-into-holes, common light chain (e.g., common light chain with knobs-into-holes, etc.), CrossMab, CrossFab, (SEED) body, leucine zipper, Duobody, lgG1 / lgG2, dual acting Fab (DAF)-lgG, and Mab2bispecific formats (see, e.g., Klein et a / . 2012, mAbs 4:6, 1-11, and references cited therein, for a review of the foregoing formats). Bispecific antibodies can also be constructed using peptide / nucleic acid conjugation, e.g., wherein unnatural amino acids with orthogonal chemical reactivity are used to generate site-specific antibody-oligonucleotide conjugates which then self-assemble into multimeric complexes with defined composition, valency and geometry. (See, e.g., Kazane et al. (2012) Site-specific DNA-antibody conjugates for specific and sensitive immuno-PCR, PNAS 109 (10) 3731-3736; DOI: 10.1073 / pnas.1120682109, and U.S. Patents Nos. 4,496,689; 4,301,144; 4,670,417; 4,791 ,192 or 4, 179,337).

[0355] In an embodiment, the SLAMF6-binding molecule (e.g., antibody or antigen-binding fragment thereof) is part of a multispecific binding molecule (e.g., a multispecific antibody or antigen-binding fragment thereof). In an embodiment, the SLAMF6-binding molecule (e.g., antibody or antigen-binding fragment thereof) is part of a bispecific binding molecule (e.g., a bispecific antibody or antigen-binding fragment thereof).

[0356] Exemplary bispecific formats that can be used in the context of the present disclosure include, without limitation, e.g., scFv-based or diabody bispecific formats, IgG-scFv fusions, dual variable domain (DVD)-lg, Quadroma, knobs-into- holes, common light chain (e.g., common light chain with knobs-into-holes, etc.), CrossMab, CrossFab, (SEED) body, leucine zipper, Duobody, lgG1 / lgG2, dual acting Fab (DAF)-lgG, and Mab2 bispecific formats (see, e.g., Klein et al. 2012, mAbs 4:6, 1-11, and references cited therein, for a review of the foregoing formats). Bispecific antibodies can also be constructed using peptide / nucleic acid conjugation, e.g., wherein unnatural amino acids with orthogonal chemical reactivity are used to generate site-specific antibody-oligonucleotide conjugates which then self-assemble into multimeric complexes with defined composition, valency and geometry. (See, e.g., Kazane et al. (2012) Sitespecific DNA-antibody conjugates for specific and sensitive immuno-PCR, PNAS 109 (10) 3731-3736; DOI: 10.1073 / pnas.1120682109, and U.S. Patents Nos. 4,496,689; 4,301 ,144; 4,670,417; 4,791 ,192 or 4,179,337).

[0357] In an embodiment, the bispecific molecule (e.g., bispecific antibody or antigen-binding fragment thereof) is designed to bind simultaneously to SLAMF6 and to a tumor cell-expressed molecule or antigen, that enables the targeting of the SLAMF6 antibodies to the tumor cells.

[0358] In another embodiment, the bispecific molecule (e.g., bispecific antibody or antigen-binding fragment thereof) is designed to simultaneously bind to SLAMF6 and to a checkpoint inhibitor. The term “immune checkpoint inhibitor” (ICI) or “immune checkpoint blocker” (ICB) as used herein refers to an agent that blocks or inhibits the activity of a negative regulator of the immune response. In an embodiment, the ICI blocks or inhibits the activity of T cells (e.g., CTLs and / or CD4 helper T cells) and / or of NK cells. Examples of such negative regulators of the immune response (i.e., immune checkpoint) include Adenosine A2A receptor (A2AR), B7-H3 (CD276), B7-H4 (VTCN1), B and T Lymphocyte Attenuator (BTLA or CD272), Cytotoxic T-Lymphocyte-Associated protein 4 (CTLA-4, CD152), CD47 / SIRPa, Indoleamine 2,3-dioxygenase (IDO), Killer-cell Immunoglobulin-like Receptor (KIR), Lymphocyte Activation Gene-3 (LAG3), nicotinamide adenine dinucleotide phosphate NADPH oxidase isoform 2 (NOX2), poliovirus receptor-related immunoglobulin (PVRIG), carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1), Programmed Death 1 (PD-1) receptor, PD-L1 , PD-L2, T-cell Immunoglobulin domain and Mucin domain 3 (TIM-3), V-domain Ig suppressor of T cell activation (VISTA), and Sialic acid-binding immunoglobulin-type lectin 7 (SIGLEC7 or CD328) and SIGLEC9 (CD329). In an embodiment, the immune checkpoint inhibitor is an inhibitor of CTLA-4, PD-1 or PD-L1. Examples of immune checkpoint inhibitors includes anti-PD-1 antibodies / blockers (e.g., Tislelizumab, Penpulimab, Pidilizumab, Sintilimab, Toripalimab, Retifanlimab, Dostarlimab, Nivolumab, Cemiplimab, Pembrolizumab, Spartalizumab, Camrelizumab, JTX-4014, INCMGA00012 (MGA012), AMP-224, AMP-514), anti-PD-L1 antibodies / blockers (e.g., Durvalumab, Avelumab, Atezolizumab, KN035, CK-301 , AUNP12, CA-170, BMS-986189), anti-CTLA-4 antibodies (e.g., Tremelimumab, Ipilimumab), anti-LAG-3 antibodies (e.g., Relatlimab, LAG525 (IMP701), REGN3767 (R3767), Bl 754,091 , tebotelimab (MGD013), eftilagimod alpha (IMP321), FS118), anti-TIM-3 antibodies (MBG453, Sym023, TSR-022), anti-B7-H3 / H4 antibodies (e.g., MGC018, FPA150), CD73 antagonists / anti-CD73 antibodies (e.g., Mupadolimab (CPI-006), Oleclumab (MEDI9447), Uliledlimab, AB680, BMS-986179, NZV930, AK119, SYM024, INCA00186, ORIC-533, IPH5301, PSB-1248937), and CD39 antagonists (TTX-030, IPH5201, SRF617), anti-NKG2A antibodies (Monalizumab), anti-PVRIG (e.g., COM701), anti-CEACAM1 antibodies (e.g., CM24), and CD47 blockers / inhibitors (Evorpacept (ALX148), Hu5F9-G4 (5F9), TTI-662, RRx-001) (see, e.g., Marin-Acevedo et al., Next generation of immune checkpoint inhibitors and beyond, Journal of Hematology & Oncology, volume 14, Article number: 45 (2021); Xia et al., CD39 / CD73 / A2AR pathway and cancer immunotherapy, Molecular Cancer, volume 22, Article number: 44 (2023)). The chemical structures and sequences of the above-noted immune checkpoint inhibitors are incorporated herein by reference.

[0359] A further aspect of the present disclosure provides nucleic acids encoding the SLAMF6-binding molecule (e.g., antibody or antigen-binding fragment thereof) described herein. The isolated nucleic acid may be a synthetic DNA, a non-naturally occurring mRNA, or a cDNA, for example. The nucleic acid may be inserted within a plasmid, vector, or transcription or expression cassette. The nucleic acids encoding the antibody or antigen-binding fragment described herein may be made and the expressed antibodies or antigen-binding fragments described may be tested using conventional techniques well known in the art.

[0360] In another aspect, the present disclosure provides a cell, for example a recombinant host cell, expressing the SLAMF6- binding molecule (e.g., antibody or antigen-binding fragment thereof) described herein. Methods of preparing antibodies or antigen-binding fragments comprise expressing the encoding nucleic acid(s) in a host cell under conditions to produce the antibodies or antigen-binding fragments and recovering the antibodies or antigen-binding fragments. The process of recovering the antibodies or antigen-binding fragments may comprise isolation and / or purification of the antibodies or antigen-binding fragments. The method of production may comprise formulating the antibodies or antigen-binding fragments into a composition including at least one additional component, such as a pharmaceutically acceptable excipient. The term "recombinant host cell" (or simply "host cell"), as used herein, is intended to refer to a cell into which exogenous DNA has been introduced. It should be understood that such terms are intended to refer not only to the particular subject cell, but, to the progeny of such a cell. Because certain modifications may occur in succeeding generations due to either mutation or environmental influences, such progeny may not, in fact, be identical to the parent cell, but are still included within the scope of the term "host cell" as used herein. Preferably host cells include prokaryotic and eukaryotic cells selected from any of the Kingdoms of life. Preferred eukaryotic cells include protist, fungal, plant and animal cells. Most preferably host cells include but are not limited to the prokaryotic cell line E. Coli] mammalian cell lines CHO, HEK 293 and COS; the insect cell line Sf9; the fungal cell Saccharomyces cerevisiae, plant cells, or algae cells.

[0361] In another aspect, the present disclosure provides a composition comprising the SLAMF6-binding molecule (e.g., antibody or antigen-binding fragment thereof) defined herein. In an embodiment, the composition further comprises the above-mentioned SLAMF6-binding molecule (e.g., antibody or antigen-binding fragment thereof) and a carrier or excipient, in a further embodiment a pharmaceutically acceptable carrier or excipient. Such compositions may be prepared in a manner well known in the pharmaceutical art by mixing the S LAM F6-binding molecule (e.g., antibody or antigen-binding fragment thereof) having a suitable degree of purity with one or more optional pharmaceutically acceptable carriers or excipients. The carrier / excipient can be suitable for administration of the SLAMF6-binding molecule (e.g., antibody or antigen-binding fragment thereof) thereof by any conventional administration route, for example, for oral, intravenous, parenteral, subcutaneous, intramuscular, intracranial, intraorbital, ophthalmic, intraventricular, intracapsular, intraspinal, intrathecal, epidural, intracisternal, intraperitoneal, intranasal or pulmonary (e.g., aerosol) administration. In an embodiment, the carrier / excipient is adapted for administration of the SLAMF6- binding molecule (e.g., antibody or antigen-binding fragment thereof) by the intravenous or subcutaneous route. In an embodiment, the carriers / excipients are adapted for administration of the SLAM F6-binding molecule (e.g., antibody or antigen-binding fragment thereof) by the intravenous route. In another embodiment, the carriers / excipients are adapted for administration of the SLAMF6-binding molecule (e.g., antibody or antigen-binding fragment thereof) by the subcutaneous route.

[0362] An "excipient" as used herein has its normal meaning in the art and is any ingredient that is not an active ingredient (drug) itself. Excipients include for example binders, lubricants, diluents, fillers, thickening agents, disintegrants, plasticizers, coatings, barrier layer formulations, lubricants, stabilizing agent, release-delaying agents and other components. "Pharmaceutically acceptable excipient" as used herein refers to any excipient that does not interfere with effectiveness of the biological activity of the active ingredients (S LAM F6-binding molecule) and that is not toxic to the subject, i.e., is a type of excipient and / or is for use in an amount which is not toxic to the subject. Excipients are well known in the art, and the present system is not limited in these respects. In certain embodiments, one or more formulations of the dosage form include excipients, including for example and without limitation, one or more binders (binding agents), thickening agents, surfactants, diluents, release-delaying agents, colorants, flavoring agents, fillers, disintegrants / dissolution promoting agents, lubricants, plasticizers, silica flow conditioners, glidants, anti-caking agents, anti-tacking agents, stabilizing agents, anti-static agents, swelling agents and any combinations thereof. As those of skill would recognize, a single excipient can fulfill more than two functions at once, e.g., can act as both a binding agent and a thickening agent. As those of skill will also recognize, these terms are not necessarily mutually exclusive. Examples of commonly used excipient include water, saline, phosphate buffered saline, dextrose, glycerol, ethanol, and the like, as well as combinations thereof. In many cases, it will be preferable to include isotonic agents, for example, sugars, polyalcohols, such as mannitol, sorbitol, or sodium chloride in the composition. Additional examples of pharmaceutically acceptable substances are wetting agents or auxiliary substances, such as emulsifying agents, preservatives, or buffers, which increase the shelf life or effectiveness.

[0363] As used herein, the term "effective amount" refers to a quantity of SLAMF6-binding molecule sufficient to achieve a desired biological, therapeutic and / or prophylactic effect, e.g., an amount which results in inhibition / reduction of cis SLAMF6-SLAMF6 interaction and / or enhancement of T cell activation, or in the prevention of, or a decrease in, the symptoms associated with tumor. The amount of the SLAMF6-binding molecule used or administered to the subject will depend, for example, on the type and severity of the disease and on the characteristics of the individual, such as general health, age, sex, body weight and tolerance to drugs. It will also depend on the degree, severity and type of disease. The skilled artisan will be able to determine appropriate dosages depending on these and other factors. The SLAMF6-binding molecule may also be administered in combination with one or more additional therapeutic compounds. In the methods described herein, the SLAM F6-binding molecule may be administered to a subject who would benefit from T cell activation (e.g., a subject having a tumor). For example, a "therapeutically effective amount" of the SLAM F6-binding molecule is meant levels in which tumor is reduced.

[0364] The SLAMF6-binding molecule or composition comprising same described herein may be used in combination with one or more additional active agents or therapies (radiotherapy, surgery, vaccines, etc.) for the treatment the targeted disease / condition or for the management of one or more symptoms of the targeted disease / condition (e.g., pain killers, anti-nausea agents, etc.). In an embodiment, the SLAM F6-binding molecule described herein is used in combination with one or more cell-based therapies (e.g., CAR T cells, CAR NK cells), checkpoint inhibitor (e.g., inhibitors of PD-1 , PD-L1 , CTLA-4, LAG-3), chemotherapeutic agents, or immunotherapies (e.g., with opsonizing antibodies specific for a tumor antigen - such as anti-CD20 antibodies). Examples of chemotherapeutic agents suitable for use in combination with the SLAMF6-binding molecule described herein include, but are not limited to, agents that disrupt microtubule formation (such as colchicines or derivatives thereof), alkylating agents, anthracycline antibiotics, anti-angiogenic agents, antimetabolites (such as nucleoside analogs), EGFR targeting agents, geldanamycin or a derivative thereof (such as 17-AAG), macrolides, platinum-based agents, proteasome inhibitors, retinoids (such as all-trans retinoic acids or a derivative thereof), therapeutic antibodies, topoisomerase inhibitors, transitional metal complexes, tyrosine kinase targeting agent (such as tyrosine kinase inhibitors), vinca alkaloids, and other cancer therapeutic agents recognized in the art. In some embodiments, chemotherapeutic agents for use in combination with the SLAMF6-binding molecule described herein comprise one or more of actinomycin, adriamycin, Alimta®, Avastin®, bleomycin, camptothecin and derivatives thereof, capecitabine, carboplatin, carmustine (BCNU), cisplatin, colchicine, cyclophosphamide, derivatives thereof, Doxil®, doxorubicin, duanorubicin, e.g., epirubicin, erbitux, erlotinib, etoposide, fluorouracil, gemcitabine, Herceptin®, HKP, interferons, Irinotecan, lapatinib, methotrexate, methyl-CCNU, mitomycin, mitoxantrone, nab-5404, nab-5800, nab-5801 , Neulasta®, Ortataxel, Oxaliplatin, paclitaxel and derivatives thereof, phenesterine, piposulfan, sorafenib, tamoxifen, Tarceva®, taxanes and derivatives thereof (e.g., taxol, taxotere and derivatives thereof, therapeutic antibodies, topetecan, Velcade®, vinblastine, vincristine, and vinorelbine. The SLAM F6-binding molecule or composition comprising same described herein may also be used in combination with one or more additional therapeutic antibodies or antibody fragments for the activation of T cells or treatment of tumors, such as one or more of the antibodies disclosed herein (e.g., 5, 21 or 23). In another embodiment, the SLAMF6-binding molecule may also be used in combination with an antibody or antigen-binding fragment thereof capable of inducing antibody-dependent cell-mediated cytotoxicity (ADCC) and / or antibody-dependent cell-mediated phagocytosis (ADCP), such as an opsonizing antibody.

[0365] The combination of active agents and / or compositions comprising same may be administered or co-administered (e.g., consecutively, simultaneously, at different times) in any conventional dosage form. Co-administration in the context of the present invention refers to the administration of more than one therapeutic in the course of a coordinated treatment to achieve an improved clinical outcome. Such co-administration may also be coextensive, that is, occurring during overlapping periods of time. For example, a first agent (e.g., the SLAM F6-binding molecule thereof described herein) may be administered to a patient before, concomitantly, before and after, or after a second active agent (e.g., a chemotherapeutic agent) is administered. The agents may in an embodiment be combined / formulated in a single composition and thus administered at the same time.

[0366] The present disclosure is illustrated in further details by the following non-limiting examples.

[0367] EXAMPLE 1 : Materials and Methods

[0368] Generation and characterization of novel anti-human SLAMF6 antibodies

[0369] To generate anti-human (h) SLAMF6 mAbs, C57BL / 6J mice were immunized with recombinant hSLAMF6-mouse (m) lgG1-Fc fusion proteins, as outlined. Splenocytes from hyperimmune mice were then fused with FO cells using polyethylene glycol (P7306; Sigma-Aldrich, St. Louis, MO, USA), and cultured in hypoxanthine-aminopterin-thymidine medium for 9-14 days before screening. Hybridomas were initially screened by ELISA using the hSLAMF6-mlgG1-Fc fusion protein or an irrelevant Fc fusion protein as control, then further tested for the capacity to stain Jurkat E6.1 cells expressing or not human SLAMF6. Characterization of novel anti-hSLAMF6 mAbs. Binding of Fc-silent Ctrl IgG MOPC21 , hSLAMF6 mAb NT-7 and Fc-silent hSLAMF6 mAbs clone 5, clone 11 , clone 21 , clone 22 and clone 23 to parental or SLAMF6'- Jurkat cells was determined by flow cytometry. The hybridomas producing anti-hSLAMF6 antibodies were then subjected to two rounds of sub-cloning.

[0370] To create recombinant versions of anti-hSLAMF6 mAbs, cDNA sequences encoding the variable regions of heavy chain (VH) and light chain (VL) were determined using total cellular RNA from the hybridomas, followed by RNA sequencing or reverse transcription-PCR, as described (Tang et al. 2023) (Table VII, below). A recombinant version of control immunoglobulin G (IgG) MAb MOPC21 was already reported (Tang et al. 2023). The VH- and VL-encoding cDNAs were cloned in frame into one or both of the following expression plasmids: pAb-mlgG2a(LALAPG), which contains genes encoding Fc-silent mouse lgG2a (mlgG2a) with the LALAPG mutation, and pAb-mlgK; pAb- hlgG1 (LALAPG), which contains genes encoding Fc-silent hlgG1 with the LALAPG mutation, and pAb-hlgK. Recombinant mAbs were then expressed in 293T cells and purified with protein A Sepharose (GE17-1279-03; Sigma- Aldrich). All recombinant mAbs were quantified by SDS-PAGE and Coomassie blue staining, using BSA as a standard.

[0371] Table VII: cDNA and amino acid sequences of the variable regions of heavy chain (VH) and light chain (VL) of anti- hSLAMF6 mAbs clones 5, 11 , 21 , 22 and 23 and MOPC21 , as well as the cDNA and amino acid sequences of the constant regions of mouse kappa light chain, wild-type mouse lgG2a and Fc-silent mouse lgG2a. Anti-hSLAMF6 mAbs are identified as hF6-(clone number).

[0372] Table VIII: Complete amino acid sequences of anti-hSLAMF6 mAbs clone 5, 11, 21, 22 and 23 and MOPC21 including light chain constant regions from either mouse IgK (m IgK) or human IgK (hlgK) and heavy chain constant regions from either Fc-silent mouse lgG2a (mlgG2a) or Fc-silent human lgG1 (hlgG1). Anti-hSLAMF6 mAbs are identified as hF6- (clone number)-(constant region).

[0373] In vitro human T cell activation assays

[0374] Human peripheral blood mononuclear cells (PBMCs) were isolated from human blood by Ficoll-Paque density gradient centrifugation. CD8+T cells were enriched from PBMCs by negative selection (StemCell EasySep™, Stem Cell Technologies, Vancouver, BC, Canada). To generate previously activated human CD8+T cells, purified CD8+T cells were stimulated with plate-bound anti-human CD3 mAb OKT3 (3 pig ml1) for 2 days and then expanded for 3 days in human IL-2 (50 U mMJ-containing medium. To produce SLAMF6 gene-disrupted human CD8- T cells or Jurkat cells, activated CD8+T cells and Jurkat cells were electroporated with ribonucleoprotein complexes containing the guide RNA sequences 5'-CCACGTGACTAATCCGAAAC-3' (SEQ ID NO: 191) (hF6 sgRNAI), 5'- AATCCCGTTCACCATCAATG-3' (SEQ ID NO: 192) (hF6 sgRNA2) or 5'-GGTTTCATGGGGTACTATGA-3' (SEQ ID NO: 193) (hF6 sgRNA3). After sorting SLAMF6-negative cells, lack of SLAMF6 expression on human CD8+T cells and Jurkat cells were confirmed by flow cytometry. For activation, freshly isolated, previously activated human CD8+T cells and Jurkat cells were stimulated with the indicated concentrations of plate-bound anti-human CD3 mAb OKT3. For blockade experiments with anti-hSLAMF6, anti-hSLAMF6 mAbs (2 pig ml1) were coated on plastic prior to addition of T cells, and T cells were stimulated with the indicated anti-CD3 mAbs. Fc-silent hSLAMF6 mAbs clone 5, clone 11 , clone 21, clone 22 and clone 23 generated and produced in the inventors’ laboratory were used, in addition to antihuman SLAMF6 clone NT-7, which was purchased from BioLegend (San Diego, CA, USA). Isotype-matched Fc-silent Ctrl IgG (MOPC21) was used as control.

[0375] Generation of OT-l CD8+ T cells

[0376] To produce exhausted OT-I CD8+T cells, SLAMF6 KO OT-I CD8+T cells mice were first activated with SIINFEKL peptide (10 ng ml-1), in medium supplemented with mouse interleukin-7 (IL-7) (5 ng ml-1 ; cat. #217-17; PeproTech, Cranbury, NJ) and IL-15 (5 ng ml-1 ; cat. #210-15, PeproTech). After 24 h, cells were transduced with retroviruses encoding human SLAMF6, as above. Then, cells were stimulated daily until day 5 with SIINFEKL peptide. At day 5, cells were washed and maintained in medium containing only the cytokines for another 3 days.

[0377] Control non-exhausted cells were activated once with SIINFEKL peptide and then, cultured in media with cytokines but without antigen peptide. To analyze cytokine production, cells were re-stimulated with SIINFEKL peptide for 6 h in the presence of GolgiPlug (cat. #555029; BD Biosciences). Then, intracellular cytokine staining was performed according to BD Biosciences protocols.

[0378] Fluorescence resonance energy transfer (FRET) assay

[0379] The acceptor photobleaching FRET assay was performed as described (Tang et al., 2023). In essence, a SNAP tag or a CLIP tag was added to the amino terminus of human SLAMF6, using PCR. After cloning into the vector pFB-Neo, constructs were co-transfected into HEK293T cells, using polyethylenimine (23966-1 ; Polysciences, Warrington, PA, USA). After 48 hours, cells were harvested and seeded into poly-L-lysine (P8920; Sigma-Aldrich)-treated 96-well plates with glass bottoms (P35G-0-20-C; MatTek Corporation, Ashland, MA, USA). After 24 hours, cells were labeled with CLIP-Surface 547 (S9233S; New England Biolabs, Ipswich, MA, USA) and SNAP-Surface Alexa Fluor 647 (S9136S; New England Biolab) for 45 minutes at 37°C, followed by 3 washes with PBS. In some cases, mAbs (5 pig ml-1) were included. Cells were then fixed for 10 minutes at room temperature with 4% paraformaldehyde (PFA, 22023- 20mL; Biotium, Fremont, CA, USA) and used for the FRET assay. Images were acquired with an LSM700 confocal microscope (Zeiss, Oberkochen, Baden-Wurttemberg, GER) by exciting CLIP-Surface 547 (energy donor) at 543 nm and SNAP-Surface Alexa Fluor 647 (energy acceptor) at 635 nm. The FRET images were acquired using Imaged™ (Fiji) with the AccPbFRET plugin, as described (Tang et al., 2023).

[0380] Retroviral transduction of T cells

[0381] Constructs encoding human SLAMF6 were generated by PCR and cloned into the pMSCV-MIGR-GFP retroviral vector, which also encodes GFP. For retrovirus generation, Phoenix cells were transfected with retroviral vector and the packaging plasmid pCL-Eco (12371 ; Addgene, Watertown, MA, USA), using the jetPRIME™ transfection reagent (VWR, Radnor, PA, USA). Retroviral supernatant was collected for 48 h. For retroviral transduction, ovalbumin (OVA)- specific OT-l transgenic CD8+T cells from SLAMF6 KO mice were stimulated for 24 h with the OVA-derived SIINFEKL (N4) agonist peptide, in the presence of irradiated splenocytes as APCs. The retroviral supernatant and 8 pig mH polybrene (Sigma-Aldrich) were added. Spinfection was performed at 32°C for 1 h at 800 g. Transduced OT-I T cells were cultured for another 48 h with IL-2 (50 U mH). GFP-positive cells were sorted for tumor studies.

[0382] Tumor studies

[0383] Eight to twelve-week-old male and female C57BL / 6J mice were subcutaneously injected with 0.5 x 106EG7 cells (a variant of mouse lymphoma cell line EL-4 expressing OVA) in the right flank. On day 7 after inoculation, mice were adoptively transferred with 0.5 x 106hS LAM F6+SLAM F6 KO OT-I CD8+T cells via the tail vein. For SLAMF6 blockade, either Fc-silent hSLAMF6 mAbs clone 21 or clone 23, or the isotype-matched Fc-silent Ctrl IgG (MOPC21), were administered intraperitoneally at 100 pig every day after the OT-I CD8- T cells transfer. The maximum tumor size allowed was 20 mm in diameter. Tumor volumes were calculated using the formula mm3= (length x width x width / 2).

[0384] For the analysis of tumor-infiltrating lymphocytes (TILs), tumors were harvested when the control tumors reached a diameter of 15-20 mm. Tumors were minced into small fragments and digested by collagenase D (1 mg mH; Sigma- Aldrich) and DNase I (0.05 mg mH; Sigma-Aldrich) for 30 minutes at 37°C. Samples were filtered with 70-pim cell strainers. After blocking with anti-CD16-CD32 hybridoma supernatant, single-cell suspensions were stained with antibodies on ice for 30 min. 7-aminoactinomycin D (7-AAD) was added to identify dead cells. Subsequently, cells were washed and analyzed using a BD LSR Fortessa™ flow cytometer (BD Biosciences).

[0385] EXAMPLE 2: Human T cells lacking SLAMF6 display augmented T cell activation

[0386] There are no published reports of the impact of loss of SLAMF6 expression in normal human T cells. To examine the role of SLAMF6 in human T cell activation, the inventors took a genetic approach. To this end, variants of healthy human donor peripheral blood T cells were rendered SLAM F6-deficient, using CRISPR-Cas technology. Three different SLAMF6-specific guide RNAs, in addition to a control guide RNA, were utilized. Following transfection of the SLAMF6 guide RNAs, a significant proportion of cells became SLAMF6-negative. This population with then purified by cell sorting (FIG. 1A), expended in vitro and tested in re-stimulation assays using anti-CD3 monoclonal antibody 0KT3. Such an experiment showed that T cells lacking SLAMF6 had enhanced responses to TCR stimulation, including proliferation (measured by thymidine incorporation) and production of cytokines interleukin-2 (IL-2) and interferon-y (IFN-y) (measured by ELISA), compared to T cells expressing SLAMF6 (FIG. 1 B). This effect was seen with T cells from multiple independent donors.

[0387] The inventors also generated variants of the human T cell line Jurkat that were deficient in SLAMF6, using a similar approach (FIG. 10). As was the case for human peripheral blood T cells, SLAMF6-deficient Jurkat cells displayed enhanced IL-2 production in response to TCR stimulation (FIG. 1 D). They also showed increased calcium fluxes, as well as augmented overall protein tyrosine phosphorylation in response to TCR stimulation (FIGs. 1 E-F).

[0388] Hence, abrogation of SLAMF6 expression in human T cells resulted in increased TCR signalling and T cell activation, indicating that SLAMF6 is an inhibitory receptor during T cell activation. This effect was independent of the presence of APCs, suggesting that it was mediated by interactions of SLAMF6 expressed on T cells with other SLAMF6 molecules expressed on T cells, the so-called cis interactions.

[0389] The inventors also determined that in mice, SLAMF6 is expressed on all T cells, including naive T cells, and suppressed T cell activation across various modes of TCR stimulation. The effects on T cell activation occurred independently of SLAMF6 expression on APCs (data not shown).

[0390] EXAMPLE 3: Blocking anti-SLAMF6 mAbs promote T cell activation

[0391] To determine whether anti-SLAMF6 mAbs block cis SLAMF6-SLAMF6 interactions, the capacity of SLAMF6 to interact in cis at the cell surface was tested with fluorescence resonance energy transfer (FRET) assays. Using HEK293T cells expressing hSLAMF6 variants labeled either with an energy acceptor (AF647) or with an energy donor (547), respectively, the inventors found that photobleaching of acceptor-labeled SLAMF6 resulted in an increase in fluorescence of donor-labeled SLAMF6, indicating energy transfer from SLAMF6 to SLAMF6 and proximity of 10 nm or less between SLAMF6 molecules (FIGs. 2A-B).

[0392] The ability of anti-hSLAMF6 mAbs clones 5, 11, 21, 22 and 23 and anti-SLAMF6 mAb NT-7 to disrupt SLAMF6- SLAMF6 interactions was next tested. Compared to control mAb MOPC21 , mAb NT-7 caused a small reduction (by -20%) of FRET, implying that it partially blocked the cis SLAMF6-SLAMF6 interactions (FIGs. 2A-B). This effect correlated with a small (less than -1 .5-fold), albeit reproducible, increase in proliferation and cytokine production by human peripheral blood T cells stimulated with anti-CD3 mAb OKT3 (FIGs. 3A-B). The anti-hSLAMF6 mAbs clone 21 and clone 23 yielded a -80-90% reduction in FRET, indicating that they had a much stronger blocking effect compared to NT-7 (FIGs. 2A-B). They also caused a much more robust increase (4- to 8-fold) in T cell activation responses (FIGs. 3A-B). This increase was observed both with ex vivo CD8- T cells and with previously activated CD8- T cells. A less prominent blocking effect on FRET and a less pronounced stimulating effect on T cell activation were achieved with clone 5, while no effects on either parameter were noted with clone 11 and clone 22 (FIGs. 2A-B and 3A-B).

[0393] Combined, these data showed that SLAMF6-SLAMF6 interactions occurred in cis at the cell surface and that anti- SLAMF6 mAbs disrupting these cis interactions were promoting T cell activation. They also indicated that mAbs clones

[0394] 5, 21 and 23 were most efficient at blocking the cis interactions and enhancing T cell activation.

[0395] EXAMPLE 4: Blocking anti-SLAMF6 mAbs inhibit tumor growth in vivo

[0396] To investigate whether the blocking anti-SLAMF6 mAbs enhanced the ability of CD8- T cells to prevent tumor growth, wild-type C57BL / 6J mice were inoculated with a variant of mouse lymphoma cell line EL-4 expressing the antigen ovalbumin (OVA; EG7) which lack endogenous SLAMF6 expression (FIG. 4A). On day 7, mice were adoptively transferred with OVA-specific OT-I CD8+T cells lacking mouse SLAMF6, but with human SLAMF6-encoding retroviruses. Fc-silent hSLAMF6 mAbs clone 21 or clone 23, or the isotype-matched Fc-silent Ctrl IgG (MOPC21), were then administered daily and tumor growth was monitored.

[0397] Compared to MOPC21, clone 21 and clone 23 caused a pronounced reduction in tumor growth (FIG. 4B). This effect was reflected by a diminution of tumor volume and tumor weight (FIGs. 4C-D). There was also an increase in the proportion of OT-I CD8- T cells infiltrating the tumors (FIG. 4E).

[0398] Hence, blocking anti-hSLAMF6 mAbs augmented the capacity of antigen-specific CD8- cells to suppress tumor growth in vivo. This effect was independent of expression of SLAM6 on tumor cells.

[0399] EXAMPLE 5: Blocking SLAMF6 mAbs prevent T cell exhaustion in vivo

[0400] The inventors then analyzed the impact Blocking SLAMF6 mAbs of T cell exhaustion. Tex (T-cell exhaustion) cells are dysfunctional CD8+T cells that have lost their ability to kill cells and release cytokines due to prolonged exposure to the same antigen, such as in chronic infections or cancer. Tex cells are reportedly Tim-3+TCF-1-, whereas naive T cells, Tern and Tpex are Tim-3 TCF-1+. Tex can also express Tox, as well as augmented levels of PD-1 , LAG-3 and TIGIT, although these markers are also enhanced in activated and effector-memory cells.

[0401] SLAMF6 mAb #21 , but not #11 , decreased the proportions of Tim-3+TCF-1- T cells (FIG. 5B), while increasing Tim-3- TCF-1- T cells (FIG. 5A), compared to control IgG (FIGs. 5A-D). It also reduced PD-1+Tim-3+, Tox- and TIGIT- T cells, and augmented LAG-3- T cells, compared to SLAMF6 mAb #11 and control IgG (FIGs. 5D-G). These various changes were compatible with prevention of T cell exhaustion. Similar effects were seen when SLAMF6 KO OT-I cells were injected, compared to wild-type OT-I cells (FIGs. 5A-G).

[0402] Analogous experiments were conducted with non-transgenic polyclonal mouse CD8- T cells expressing human SLAMF6 that were injected in Rag-1-'- mice previously inoculated with MC-38 colon carcinoma cells (FIG. 6A). As MC- 38 is sensitive to PD-1-PD-L1 blockade, the effects of blocking PD-L1 mAb 10F.9G2 were analyzed in parallel. Compared to control IgG, SLAMF6 mAb #21 diminished MC-38 tumor growth (FIG. 6B).

[0403] Additionally, tumors from SLAMF6 mAb #21 -treated mice displayed increased proportions of T cells (FIG. 6C), with augmented production of IFN-y and TNF-a (FIG. 6D) and reduced percentages of Tim-3+TCF-1 T cells, but increased Tim-3 TCF-1- T cells, compared to control IgG (FIG. 6E).

[0404] Reduced PD-1 -Tim-3- (FIG. 6F), Tox- (FIG. 6G, left graph) and TIGIT- T cells (FIG. 6G, middle graph), as well as augmented LAG-3- T cells (FIG. 6G, right graph), were also seen. Similar effects were noted with PD-L1 mAb 10F.9G2, although they tended to be of smaller magnitude, in comparison to SLAMF6 mAb #21 (FIGs. 6F-G).

[0405] The combination of SLAMF6 mAb #21 and PD-L1 mAb 10F.9G2 was more effective than SLAMF6 mAb #21 or PD-L1 mAb 10F.9G2 alone (FIGs. 6B-G).

[0406] The impact of the SLAMF6 mAbs was then evaluated in active models of T cell exhaustion. First was assessed the in vivo effects of SLAMF6 mAbs on OT-I cells that had been exhausted through repeated in vitro stimulation with OVA peptide (FIG. 7 A). In keeping with exhaustion, repeatedly stimulated OT-I cells displayed reduced cytokine production, augmented expression of Tim-3, loss of TCF-1 and elevated expression of Tox in vitro, compared to non-exhausted cells (Data not shown). Most Tim-3* cells still expressed TCF-1, suggesting that they were in the process of becoming Tex.

[0407] When injected in E.G7-bearing mice, the in vitro exhausted T cells were less efficient at suppressing tumor growth (FIG. 5H), and displayed decreased infiltration in tumors (FIG. 5I, upper graphs), lower production of cytokines (FIG. 5I, lower graphs) and augmented expression of Tim-3, compared to non-exhausted T cells (FIG. 5J, lower left graph and upper and lower right graphs).

[0408] Upon treatment with SLAMF6 mAb #21 , however, they showed better suppression of tumor growth (FIG. 5H), greater cytokine production cytokines (FIG. 5I, lower graphs), reduced proportions of Tim-3+TCF-1+and Tim-3+TCF-1' (FIG. 5J, upper right and lower left graphs, respectively), PD-1+Tim-3+(FIG. 5J, lower right graph), Tox- (FIG. 7B, left graph) and TIGIT- cells (FIG. 7B, middle graph), and augmented proportions of Tim-3 TCF-1+(FIG. 5J, upper left graph) and LAG-3- cells (FIG. 7B, right graph), compared to control IgG. Although cells not exhausted in vitro were more tumorsuppressive, compared to in vitro exhausted cells, they were still rescued by SLAMF6 mAb #21. This was expected as T cells not exhausted in vitro still underwent exhaustion in vivo.

[0409] Next were investigated the in vitro effects of SLAM F6 mAbs using human T cells driven to exhaustion through repeated stimulation with CD3 mAbs (FIG. 8A). Upon re-activation with CD3 mAbs (WT+ Ctr IgG), the cells exhibited minimal production of IFN-y and TNF-a (FIG. 8B), along with an increased frequency of Tim-3+TCF-r cells (FIG. 80), in keeping with exhaustion. In contrast, re-activation in the presence of blocking SLAMF6 mAb #21 or #23, but not nonblocking SLAMF6 mAb #11 , restored IFN-y and TNF-a production (FIG. 8B) and reduced the proportions of Tim- 3+TCF-1“ cells (FIG. 80). This was accompanied by diminished proportions of PD-1- (FIG. 8D, left graph), Tox- (FIG. 8D, middle graph) cells, and augmented proportions of LAG-3- cells (FIG. 8D, right graph). Similar effects were seen when human SLAMF6 KO CD8- T cells were tested, in comparison to wild-type CD8+ T cells (FIGs. 8B-D).

[0410] Thus, blocking human SLAMF6 mAbs suppressed tumor growth, enhanced anti-tumor T cell responses, increased TO cell infiltration of tumor cells and prevented T cell exhaustion.

[0411] EXAMPLE 6: Other SLAMF6 activities

[0412] The inventors also demonstrated the following SLAMF6 activities: SLAMF6 suppresses graft-versus-host disease (GVHD), a T cell-dependent immunopathology (data not shown). SLAMF6 suppresses proximal TOR signaling in normal T cells, seemingly through SHP-1 (data not shown). The inhibitory effect of SLAMF6 on T cell activation is not influenced by SAP (data not shown). SLAMF6 inhibits T cell activation in human T cells, due to effects on proximal TCR signaling (data not shown).

[0413] The scope of the claims should not be limited by the embodiments set forth in the examples, but should be given the broadest interpretation consistent with the description as a whole.

[0414] REFERENCES

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Claims

CLAIMS:

1. An anti-SLAM family member 6 (SLAM F6) antibody or an antigen-binding fragment thereof which binds to an Ig like domain defined by residues 35 to 120 of human SLAMF6 or to an epitope within this domain of human SLAMF6.

2. The anti-SLAMF6 antibody or antigen-binding fragment thereof of claim 1 , comprising:(i) a light chain complementary determining region (CDR) 1 region comprising an amino acid sequence of formula I:X1 -A-S-X2-X3-X4-X5-X6-X7-X8-A (I) whereinX1 is K or R;X2 is Q or E;X3 is D or N;X4 is V or I;X5 is S or Y;X6 is T, N or SX7 is A, R or N; andX8 is V or L;(ii) a light chain complementary determining region (CDR) 2 region comprising an amino acid sequence of formula II:Y1-A-Y2-Y3-Y4-Y5-Y6 (II) whereinY1 is W. G or A;Y2 is S or T;Y3 is T, S or N;Y4 is R or L;Y5 is H, E or A; andY6 is T or D;(iii) a light chain complementary determining region (CDR) 3 region comprising an amino acid sequence of formula III:Q-Z1-Z2-Z3-Z4-Z5-Z6-Z7-T (III) whereinZ1 is Q or H;Z2 is H, Y or F;Z3 is Y or W;Z4 is S or G;Z5 is T or N;Z6 is P orS; andZ7isForW;(iv) a heavy chain complementary determining region (CDR) 1 region comprising an amino acid sequence of formula IV:G-A1-A2-A3-A4-A5-A6-A7-A8 (IV) whereinA1 isForY;A2 isS orT;A3 is L or F;A4 isS orT;A5 isT orD;A6 is F orY;A7 is G or absent; andA8 is M or absent;(v) a heavy chain CDR2 region comprising an amino acid sequence of formula V:B1-B2-B3-B4-B5-B6 (V) whereinB1 isWorN;B2 is W or P;B3 is D, S or N;B4 is D or N;B5 is G or is absent; andB6 is D orG; and(vi) a heavy chain CDR3 region comprising an amino acid sequence of formula VI:C 1 -C2-C3-C4-C5-C6-C7-C8-C9-C 10-D-Y (VI) wherein01 is T, E orS;02 is G or L;C3 is K, S orG;C4 is G, L or is absent;C5 is N, R or is absent;C6 is Y or is absent;C7 is Y or is absent;C8 is H, S or is absent;C9 is A, T or is absent; andC10 is F or M.The anti-SLAMF6 antibody or antigen-binding fragment thereof of claim 2, wherein(i) the amino acid sequence of formula I is:X1-A-S-E-X3-I-Y-X6-X7-L-A (I) whereinX1 is K or R;X3 is D or N;X6 is N or S; andX7 is R or N;(ii) the amino acid sequence of formula II is:Y1-A-T-Y3-L-Y5-Y6 (II) whereinY1 is G or A;Y3 is S or N;Y5 is E or A; andY6 is T or D;(iii) the amino acid sequence of formula III is:Q-Z1-Z2-W-Z4-Z5-Z6-W-T (lll) whereinZ1 is Q or H;Z2 is Y or F;Z4 is S or G;Z5 is T or N; andZ6 is P or S;(i v) the amino acid sequence of formula IV is:G-Y-T-F-T-D-Y (SEQ ID NO : 1);(v) the amino acid sequence of formula V is:N-P-B3-N-G-G (V) whereinB3 is S or N; and(vi) the amino acid sequence of formula VI is:C 1 -C2-C3-C4-C5-C6-C7-C8-C9-C 10-D-Y (VI) wherein01 is E or S;02 is G or L;C3 is S or G;C4 is L or is absent;C5 is R or is absent;C6 is Y or is absent;C7 is Y or is absent;C8 is H or S;C9 is A, or T; andC10 is F or M.

4. The anti-SLAMF6 antibody or antigen-binding fragment thereof of claim 1, comprising:(g) a light chain complementary determining region (CDR) 1 comprising one of the following amino acid sequences KASQDVSTAVA (SEQ ID NO: 21), KASEDIYNRLA (SEQ ID NO: 63) or RASENIYSNLA (SEQ ID NO: 105), preferably KASEDIYNRLA (SEQ ID NO: 63) or RASENIYSNLA (SEQ ID NO: 105);(h) a light chain CDR2 comprising one of the following amino acid sequences: WASTRHT (SEQ ID NO: 27), GATSLET (SEQ ID NO: 69) or AATNLAD (SEQ ID NO: 111), preferably GATSLET (SEQ ID NO: 69) or AATNLAD (SEQ ID NO: 111);(i) a light chain CDR3 comprising one of the following amino acid sequences: QQHYSTPFT (SEQ ID NO: 32), QQYWSNSWT (SEQ ID NO: 74) or QHFWGTPWT (SEQ ID NO: 116), preferably QQYWSNSWT (SEQ ID NO: 74) or QHFWGTPWT (SEQ ID NO: 116);(j) a heavy chain CDR1 comprising one of the following amino acid sequences: GFSLSTFGM (SEQ ID NO: 40), or GYTFTDY (SEQ ID NO: 82), preferably GYTFTDY (SEQ ID NO: 82);(k) a heavy chain CDR2 comprising one of the following amino acid sequences: WWDDD (SEQ ID NO: 48), NPSNGG (SEQ ID NO: 90) or NPNNGG (SEQ ID NO: 127), preferably NPSNGG (SEQ ID NO: 90) or NPNNGG (SEQ ID NO: 127); and(l) a heavy chain CDR3 comprising one of the following amino acid sequences: TGKGNYFDY (SEQ ID NO: 55), EGSLRYYHAMDY (SEQ ID NO: 97) or SLGSTFDY (SEQ ID NO: 134), preferably EGSLRYYHAMDY (SEQ ID NO: 97) or SLGSTFDY (SEQ ID NO: 134).

5. The anti-SLAMF6 antibody or antigen-binding fragment thereof of claim 4, wherein:(i) the light chain CDR1 comprises the amino acid sequence KASQDVSTAVA (SEQ ID NO: 21), the light chain CDR2 comprises the amino acid sequence WASTRHT (SEQ ID NO: 27), the light chain CDR3 comprises the amino acid sequence QQHYSTPFT (SEQ ID NO: 32), the heavy chain CDR1 comprises the amino acid sequence GFSLSTFGM (SEQ ID NO: 40); the heavy chain CDR2 comprises the amino acid sequence WWDDD (SEQ ID NO: 48), and the heavy chain CDR3 comprises the amino acid sequence TGKGNYFDY (SEQ ID NO: 55); or(ii) the light chain CDR1 comprises the amino acid sequence KASEDIYNRLA (SEQ ID NO: 63), the light chain CDR2 comprises the amino acid sequence GATSLET (SEQ ID NO: 69), the light chain CDR3 comprises the amino acid sequence QQYWSNSWT (SEQ ID NO: 74), the heavy chain CDR1 comprises the amino acid sequenceGYTFTDY (SEQ ID NO: 82); the heavy chain CDR2 comprises the amino acid sequence NPSNGG (SEQ ID NO: 90), and the heavy chain CDR3 comprises the amino acid sequence EGSLRYYHAMDY (SEQ ID NO: 97); or(iii) the light chain CDR1 comprises the amino acid sequence RASENIYSNLA (SEQ ID NO: 105), the light chain CDR2 comprises the amino acid sequence AATNLAD (SEQ ID NO: 111), the light chain CDR3 comprises the amino acid sequence QHFWGTPWT (SEQ ID NO: 116), the heavy chain CDR1 comprises the amino acid sequence GYTFTDY (SEQ ID NO: 82); the heavy chain CDR2 comprises the amino acid sequence NPNNGG (SEQ ID NO: 127), and the heavy chain CDR3 comprises the amino acid sequence SLGSTFDY (SEQ ID NO: 134).

6. The anti-SLAMF6 antibody or antigen-binding fragment thereof of any one of claims 1 to 5, further comprising:(i) a light chain framework region 1 (FR1) comprising an amino acid sequence of formula VII:D-l-Xb1-M-T-Q-S-Xb2-Xb3-Xb4-Xb5-S-Xb6-S-Xb7-G-Xb8-Xb9-V-Xb10-l-T-C (VII) whereinXb1 is V or Q;Xb2 is H, S or P;Xb3 is K. S or A;Xb4 is F or S;Xb5 is M, F or L;Xb6 is T or V;Xb7 is V or L;Xb8 is D or E;Xb9 is R or T; andXbW is S or T;(ii) a light chain FR2 comprising an amino acid sequence of formula VIII:W-Y-Q-Q-K-Xb11 -G-Xb12-Xb 13-P-Xb14-L-L-Xb 15-Xb16 (VIII) whereinXb11 is P or Q;Xb12 is Q, N or K;Xb13 is S or A;Xb14 is K, R or Q;Xb15 is I or V; andXb16 is Y or S;(iii) a light chain FR3 comprising an amino acid sequence of formula IX:G-V-P-Xb17-R-F-Xb18-G-S-G-S-G-Xb19-Xb20-Y-Xb21-L-Xb22-l-Xb23-S-Xb24-Q-Xb25-E-D-Xb26- Xb27-Xb28-Y-Y-C (IX) whereinXb17 is D or S;Xb18isTorS;Xb19 is T or K;Xb20 is D orQ;Xb21 isTorS;Xb22 is T, S or K;Xb23 is S, T or N;Xb24 is V or L;Xb25 is A, T or S;Xb26 is L, V or F;Xb27 is A or G; andXb28 is L, T or S;(iv) a light chain FR4 comprising an amino acid sequence of formula X:F-G-Xb29-G-T-K-L-E-I-K (X) (SEQ ID NO: 195) whereinXb29 is S or G;(v) a heavy chain FR1 comprising an amino acid sequence of formula XI:Xb30-V-Xb31-L-Xb32-Xb33-S-G-P-Xb34-Xb35-Xb36-Xb37-P-Xb38-Xb39-Xb40-Xb41-Xb42-Xb43-Xb44-C-Xb45-Xb46-S (XI) whereinXb30 is Q or E;Xb31 isTorQ;Xb32 isKorQ;Xb33 is E or Q;Xb34 is G or E;Xb35 is I or L;Xb36 isLorV;Xb37 is Q or K;Xb38 is S or G;Xb39 is Q or A;Xb40 is T, A or S;Xb41 isLorV;Xb42 is S or K;Xb43 is Lor I;Xb44 is T, S or P;Xb45 is S or K; andXb46 is For A;(vi) a heavy chain FR2 comprising an amino acid sequence of formula XII:Xb47-Xb48-Xb49-W-Xb50-Xb51-Q-Xb52-Xb53-G-K-Xb54-L-E-W-Xb55-Xb56-Xb57-l (XII) whereinXb47 is G or absent;Xb48 isVorM;Xb49 is G, N or D;Xb50 is I or V;Xb51 isRor K;Xb52 isPorS;Xb53 is S or H;Xb54 is G or S;Xb55 is Lor I;Xb56 is A or G; andXb57 is H or D;(vii) a heavy chain FR3 comprising an amino acid sequence of formula XIII:Xb58-Xb59-Xb60-N-Xb61-Xb62-Xb63-K-Xb64-Xb65-Xb66-T-Xb67-Xb68-Xb69-D-Xb70-S-Xb71-Xb72-Xb73-Xb74-Xb75-Xb76-Xb77-Xb78-Xb79-Xb80-Xb81-Xb82-Xb83-Xb84-D-Xb85-A-Xb86-Y-Y-O-A-Xb87(XIII) whereinXb58 is K, S or T;Xb59 is Y, R or L;Xb60 isY, NorY;Xb61 is P, Q or R;Xb62 is A or K;Xb63 is L or F;Xb64 isSorG;Xb65 is R or K;Xb66 is L or A;Xb67 is I or L;Xb68 isSorT;Xb69 isKorV;Xb70 is T or K;Xb71 isKorS;Xb72 is N or S;Xb73 is Q or T;Xb74 is V or A;Xb75 isForY;Xb76 is L or M;Xb77 is K or E;Xb78 is I or L;Xb79 is A or R;Xb80 is N or S;Xb81 isVorL;Xb82 isDorT;Xb83 isTorS;Xb84 is A or E;Xb85 isTorS;Xb86 is T or V; andXb87 is P or R;(viii) a heavy chain FR4 comprising an amino acid sequence of formula XIV:W-G-Q-G-T-Xb88-Xb89-T-V-S-S (XIV) (SEQ ID NO: 196) whereinXb88 is T or S; andXb89 is LorV; or(ix) a combination of at least two of (i) to (viii).

7. The anti-SLAMF6 antibody or antigen-binding fragment thereof of claim 6, wherein:(i) the amino acid sequence of formula VII is:D-I-Q-M-T-Q-S-Xb2-Xb3-S-Xb5-S-V-S-Xb7-G-Xb8-Xb9-V-T-I-T-C (VII) (SEQ ID NO: 197) whereinXb2 is S or P;Xb3 is S or A;Xb5 is F or L;Xb7 is V or L;Xb8 is D or E; andXb9 is R or T;(ii) the amino acid sequence of formula VIII is:W-Y-Q-Q-K-Xb11 -G-Xb12-Xb13-P-Xb14-L-L-Xb15-Xb16 (VIII) (SEQ ID NO: 198) whereinXb11 isPorQ;Xb12 is N or K;Xb13 is S or A;Xb14 is R or Q;Xb15 is I or V; andXb16 is Y or S;(iii) the amino acid sequence of formula IX is:G-V-P-S-R-F-S-G-S-G-S-G-Xb19-Xb20-Y-Xb21-L-Xb22-l-Xb23-S-L-Q-Xb25-E-D-Xb26-Xb27-Xb28-Y-Y-C (IX) (SEQ ID NO: 199) whereinXb19 is T or K;Xb20 is D or Q;Xb21 is T or S;Xb22 is S or K;Xb23 is T or N;Xb25 is T or S;Xb26 is V or F;Xb27 is A or G; andXb28 is T or S;(iv) the amino acid sequence of formula X is:F-G-G-G-T-K-L-E-l-K (SEQ ID NO: 194)(v) the amino acid sequence of formula XI is:E-V-Q-L-Q-Q-S-G-P-E-L-V-K-P-G-A-Xb40-V-K-l-Xb44-C-K-A-S (XI) (SEQ ID NO: 200) whereinXb40 is A or S; andXb44 is S or P;(vi) the amino acid sequence of formula XII is:Xb47’-M-Xb49-W-V-K-Q-S-H-G-K-S-L-E-W-I-G-D-I (XII) (SEQ ID NO: 201) whereinXb47’ is D or N; andXb49 is N or D;(vii) the amino acid sequence of formula XIII is:Xb58-Xb59-Xb60-N-Xb61-K-F-K-G-K-A-T-L-T-V-D-K-S-S-S-T-A-Y-Xb76-E-L-R-S-L-T-S-E-D-Xb85-A-V-Y-Y-C-A-R (XIII) (SEQ ID NO: 202) whereinXb58 is S or T;Xb59 is R or L;Xb60 is N or Y;Xb61 is Q or R;Xb76 is L or M; andXb85 is T or S;(viii) the amino acid sequence of formula XIV is:W-G-Q-G-T-Xb88-Xb89-T-V-S-S (XIV) (SEQ ID NO: 196) whereinXb88 is T or S; andXb89 is L or V; or(ix) a combination of at least two of (i) to (viii).

8. The anti-SLAMF6 antibody or antigen-binding fragment thereof of any one of claims 1 to 7, comprising the following framework regions (FRs): (i) a light chain FR1 comprising one of the following amino acid sequences: DIVMTQSHKFMSTSVGDRVSITC (SEQ ID NO: 18), DIQMTQSSSSFSVSLGDRVTITC (SEQ ID NO: 60) or DIQMTQSPASLSVSVGETVTITC (SEQ ID NO: 102); (ii) a light chain FR2 comprising one of the following amino acid sequences: WYQQKPGQSPKLLIY (SEQ ID NO: 24), WYQQKPGNAPRLLIS (SEQ ID NO: 66) or WYQQKQGKSPQLLVY (SEQ ID NO: 108); (iii) a light chain FR3 comprising one of the following amino acid sequences: GVPDRFTGSGSGTDYTLTISSVQAEDLALYYC (SEQ ID NO: 29),GVPSRFSGSGSGKDYTLSITSLQTEDVATYYC (SEQ ID NO: 71) orGVPSRFSGSGSGTQYSLKINSLQSEDFGSYYC (SEQ ID NO: 113); (iv) a light chain FR4 comprising one of the following amino acid sequences: FGSGTKLEIK (SEQ ID NO: 34), FGGGTKLEIK (SEQ ID NO: 76) or FGGGTKLEIK (SEQ ID NO: 76); (v) a heavy chain FR1 comprising one of the following amino acid sequences: QVTLKESGPGILQPSQTLSLTCSFS (SEQ ID NO: 37), EVQLQQSGPELVKPGAAVKISCKAS (SEQ ID NO: 79) or EVQLQQSGPELVKPGASVKIPCKAS (SEQ ID NO: 119); (vi) a heavy chain FR2 comprising one of the following amino acid sequences: GVGWIRQPSGKGLEWLAHI (SEQ ID NO: 44), DMNWVKQSHGKSLEWIGDI (SEQ ID NO: 86) or NMDWVKQSHGKSLEWIGDI (SEQ ID NO: 124); (vii) a heavy chain FR3 comprising one of the following amino acid sequences: KYYNPALKSRLTISKDTSKNQVFLKIANVDTADTATYYCAP (SEQ ID NO: 52), SRNNQKFKGKATLTVDKSSSTAYLELRSLTSEDSAVYYCAR (SEQ ID NO: 94) orTLYNRKFKGKATLTVDKSSSTAYMELRSLTSEDTAVYYCAR (SEQ ID NO: 131); (viii) a heavy chain FR4 comprising one of the following amino acid sequences: WGQGTTLTVSS (SEQ ID NO: 58), WGQGTSVTVSS (SEQ ID NO: 100) or WGQGTTLTVSS (SEQ ID NO: 58); or (ix) at least two of (i) to (viii), preferably at least three, four, five, six, seven or all eight of (i) to (viii).

9. The anti-SLAMF6 antibody or antigen-binding fragment thereof of any one of claims 1 to 8, comprising the following framework regions (FRs):(d) (i) a light chain FR1 comprising amino acid sequence DIVMTQSHKFMSTSVGDRVSITC (SEQ ID NO: 18); (ii) a light chain FR2 comprising amino acid sequence WYQQKPGQSPKLLIY (SEQ ID NO: 24); (iii) a light chain FR3 comprising amino acid sequence GVPDRFTGSGSGTDYTLTISSVQAEDLALYYC (SEQ ID NO: 29); (iv) a light chain FR4 comprising amino acid sequence FGSGTKLEIK (SEQ ID NO: 34); (v) a heavy chain FR1 comprising amino acid sequence QVTLKESGPGILQPSQTLSLTCSFS (SEQ ID NO: 37);(vi) a heavy chain FR2 comprising amino acid sequence GVGWIRQPSGKGLEWLAHI (SEQ ID NO: 44);(vii) a heavy chain FR3 comprising amino acid sequence KYYNPALKSRLTISKDTSKNQVFLKIANVDTADTATYYCAP (SEQ ID NO: 52); (viii) a heavy chain FR4 comprising amino acid sequence WGQGTTLTVSS (SEQ ID NO: 58); or (ix) at least two of (i) to (viii), preferably at least three, four, five, six, seven or all eight of (i) to (viii);(e) (i) a light chain FR1 comprising amino acid sequence DIQMTQSSSSFSVSLGDRVTITC (SEQ ID NO: 60);(ii) a light chain FR2 comprising amino acid sequence WYQQKPGNAPRLLIS (SEQ ID NO: 66); (iii) a light chain FR3 comprising amino acid sequence GVPSRFSGSGSGKDYTLSITSLQTEDVATYYC (SEQ ID NO: 71); (iv) a light chain FR4 comprising amino acid sequence FGGGTKLEIK (SEQ ID NO: 76); (v) a heavy chain FR1 comprising amino acid sequence EVQLQQSGPELVKPGAAVKISCKAS (SEQ ID NO: 79); (vi) a heavy chain FR2 comprising amino acid sequence DMNWVKQSHGKSLEWIGDI (SEQ ID NO: 86); (vii) a heavy chain FR3 comprising amino acid sequence SRNNQKFKGKATLTVDKSSSTAYLELRSLTSEDSAVYYCAR (SEQ ID NO: 94); (viii) a heavy chain FR4 comprising amino acid sequence WGQGTSVTVSS (SEQ ID NO: 100); or (ix) at least two of (i) to (viii), preferably at least three, four, five, six, seven or all eight of (i) to (viii); or(f) (i) a light chain FR1 comprising amino acid sequence DIQMTQSPASLSVSVGETVTITC (SEQ ID NO: 102); (ii) a light chain FR2 comprising amino acid sequence WYQQKQGKSPQLLVY (SEQ ID NO: 108);(iii) a light chain FR3 comprising amino acid sequence GVPSRFSGSGSGTQYSLKINSLQSEDFGSYYC (SEQ ID NO: 113); (iv) a light chain FR4 comprising amino acid sequence FGGGTKLEIK (SEQ ID NO: 76); (v) a heavy chain FR1 comprising amino acid sequence EVQLQQSGPELVKPGASVKIPCKAS (SEQ ID NO: 119); (vi) a heavy chain FR2 comprising amino acid sequence NMDVWKQSHGKSLEWIGDI (SEQ ID NO: 124); (vii) a heavy chain FR3 comprising amino acid sequence TLYNRKFKGKATLTVDKSSSTAYMELRSLTSEDTAVYYCAR (SEQ ID NO: 131); (viii) a heavy chain FR4 comprising amino acid sequence WGQGTTLTVSS (SEQ ID NO: 58); or (ix) at least two of (i) to (viii), preferably at least three, four, five, six, seven or all eight of (i) to (viii).

10. The anti-SLAMF6 antibody or antigen-binding fragment thereof of any one of claims 1 to 9, comprising a light chain variable region (VL) comprising the amino acid sequence set forth in SEQ ID NO: 138, 146 or 154, preferably 146 or 154.

11. The anti-SLAMF6 antibody or antigen-binding fragment thereof of any one of claims 1 to 10, comprising a heavy chain variable region (VH) comprising the amino acid sequence set forth in SEQ ID NO: 140, 148 or 156, preferably 148 or 156.

12. The anti-SLAMF6 antibody or antigen-binding fragment thereof of any one of claims 1 to 11 , comprising at least one constant domain or a fragment thereof, which preferably comprises a Fragment crystallizable (Fc) fragment of a heavy chain constant region of an antibody.

13. The anti-SLAMF6 antibody or antigen-binding fragment thereof of any one of claims 1 to 12, wherein the antibody is a fully human antibody or a chimeric antibody, preferably wherein the antibody is an lgG1 antibody.

14. The anti-SLAMF6 antibody or antigen-binding fragment thereof of any one of claims 1 to 13, for enhancing T cell activation and / or for preventing T cell exhaustion and / or for increasing the proportion of T cells infiltrating tumors and / or for reducing tumor growth.

15. The anti-SLAMF6 antibody or antigen-binding fragment thereof of any one of claims 1 to 14, wherein enhanced T cell activation includes enhanced T cell proliferation, enhanced production of cytokines interleukin-2 (IL-2) and / or enhanced production of interferon-y (IFN-y).

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