Field of the invention

The present invention relates to the field of immunology, more in particular to the field of antibodies which bind to human CDld. In particular, the invention relates to the treatment of hematological malignancies using antibodies comprising a first binding moiety that is able to bind human CDld and a second binding moiety that is able to bind the human Vy9V62-TCR.

Background of the invention

In recent years, the therapeutic arsenal for chronic lymphocytic leukemia (CLL) has substantially increased with the introduction of tyrosine kinase inhibitors, Bcl-2 inhibitors and monoclonal antibodies. However, the need for long-term or continuous treatment, resistance and toxicity concerns highlight the need for novel treatment options.

The curative responses observed after allogeneic stem cell transplantation in CLL indicate the therapeutic potential of T cell-based therapies (van Gelder et al. (2017) Bone Marrow Transplant 52:372). Recent attempts to exploit T cell-based therapies in CLL have focused on the development of chimeric antigen receptor (CAR) T cells, in which a diverse, non-antigen specific pool of T cells is endowed with a CAR that recognizes a tumor- associated surface antigen. In contrast to the promising clinical responses observed with CAR T cell therapy in acute lymphoblastic leukemia and diffuse large B cell lymphomas, the response rates and durations in CLL have been disappointing Park et al. (2018) N Engl J Med. 378(5):449-459; Chow et al. (2018) Blood 132(8):777-781). Toxicity is another important concern with CAR T cell therapy, particularly in the elderly CLL population (Brudno et al. (2019) Blood Rev 34:45).

Selective activation of intrinsically tumor-responsive cytotoxic T lymphocytes represents an alternative approach that could generate a potent and focused anti-tumor response. Vy9V62-T cells form a conserved T cell subset that can induce apoptosis in a wide range of malignant cells in an HLA-independent way (Lo Presti et al. (2017) Front Immunol. 8:1401; de Weerdt et al. (2018) Blood 132(21):2260-2272; Gertner-Dardenne et al. (2012) J Immunol. 188(9):4701-4708; Kunzmann et al. (2000) Blood 96(2):384-392). The Vy9V62-T cell receptor (TCR) recognizes conformational changes in CD277 (BTN3A1) that occur with high levels of phosphoantigens, metabolites generated in inter alia the mevalonate pathway. Phosphoantigens are upregulated during cellular stress, such as infection or malignant transformation, or through pharmacological manipulation with aminobisphosphonates (ABP). In addition, NK receptors allow Vy9V62-T cells to recognize malignant cells via stress ligands, such as the NKG2D ligands MICA/B and ULBP4. Following activation, Vy9V62-T cell functions include cytotoxicity, secretion of pro-inflammatory cytokines and antigen presentation (Vantourout et al. (2013) Nat Rev Immunol. 13(2):88-100).

These characteristics have led to clinical trials aiming to exploit the anti-tumor potential of Vy9V62-T cells, including ABP-based approaches to induce in vivo Vy9V62-T cell proliferation (Dieli et al. (2007) Cancer Res. 67(15):7450-7457; Wilhelm et al. (2003) Blood 102(l):200-206; Kunzmann et al. (2012) J Immunother. 35(2):205-213). Alternative strategies employed adoptive transfer of ex vivo expanded Vy9V62-T cells (Abe et al (2009) Exp Hematol. 37(8):956-968; Wilhelm et al. (2014) J Transl Med. 12:45; Kobayashi et al. (2011) Cancer Immunol Immunother. 60(8):1075-1084). With both strategies, objective responses were observed in hematological malignancies, along with a limited toxicity profile, thus establishing the feasibility of Vy9V62-T cell therapy (Wilhelm et al. (2003) Blood 102(1):200- 206; Kunzmann et al. (2012) J Immunother. 35(2):205-213; Abe et al (2009) Exp Hematol. 37(8):956-968; Wilhelm et al. (2014) J Transl Med. 12:45). However, these pilot studies demonstrated substantial variability in responses. In summary, although prior studies have demonstrated incidental clinical benefit and safety of Vy9V62-T cell-based therapy, the observed response rates and durations thereof have so far been unsatisfactory, indicating that novel strategies are needed both for the treatment of CLL as well as for the treatment of other hematological malignancies such as multiple myeloma and acute myeloid leukemia.

Summary of the invention

The inventors have now identified CDld as a suitable target for antibody-based strategies in the majority of a large cohort of 78 CLL patients, particularly in patients with advanced disease. It has furthermore been demonstrated that a CDld-specific Vy9V62-T cell engager (a bispecific CDld/Vy9V62 antibody) based on single domain antibodies (VHHs) induces robust activation and degranulation of Vy9V62-T cells. This enables Vy9V62-T cells from both healthy controls and CLL patients to lyse leukemic cells at favorable effector to target ratios. Moreover, all-trans retinoic acid induces upregulation of CDld on CLL cells and sensitizes the malignant cells to lysis induced by a bispecific CDld/Vy9V62 antibody. Furthermore, evidence is provided that the Vy9V62-T cell receptor retains its responsiveness to phosphoantigens when the bispecific antibody is bound, and aminobisphosphonates can therefore enhance bispecific antibody mediated-tumor-specific killing. Collectively, the data demonstrate the immunotherapeutic potential of this novel CDld-specific Vy9V62-T cell engager in CLL.

Furthermore, the inventors have shown that a bispecific CDld/Vy9V62-TCR antibody can induce degranulation of iNKT cells and Vy9V62-T cells and control growth of other CDld- expressing tumor cells, including multiple myeloma cells and acute myeloid leukemia cells. Furthermore, in a mouse multiple myeloma model, infusion of both iNKT cells and y6 T cells with a bispecific CDld/Vy9V62-TCR antibody significantly prolonged survival compared to a mixture of the iNKT cells and y6 T cells alone without the antibody.

Accordingly, in a first aspect, the invention relates to an antibody comprising a first binding moiety that is able to bind human CDld and a second binding moiety that is able to bind the human Vy9V62-TCR for use in the treatment of Chronic Lymphocytic Leukemia (CLL), Multiple Myeloma (MM) or Acute Myeloid Leukemia (AML).

In a further aspect, the invention relates to a method for the treatment of Chronic Lymphocytic Leukemia, Multiple Myeloma or Acute Myeloid Leukemia, comprising administration of an antibody comprising a first binding moiety that is able to bind human CDld and a second binding moiety that is able to bind the human Vy9V62-TCR to a human subject in need thereof.

Brief description of the drawings

Fig. 1. Anti-CDld VHH mediated activation and inhibition of invariant natural killer T (iNKT) cells. iNKT CD25 expression and interferon-y (IFN-y) production were determined after a 24-hr co-culture of iNKT cells with CDld-transfected HeLa cells pulsed with vehicle control (vehicle) or aGalCer whether or not in combination with anti-CDld VHH 1D12 (100 nM) or 1D22 (1000 nM). Representative dot-plots illustrating marked activation by 1D12 (A) or inhibition by 1D22 (B) of iNKT cells as depicted by CD25 expression, in addition to a marked increase (by 1D12) or decrease (by 1D22) in iNKT cell IFN-y production (C and D). Data represent mean + SD of 3-4 individual experiments with iNKT obtained from different donors, **P<0.01, ***P < 0.001, calculated with a one-way analysis of variance with Turkey's post hoc test.

Fig. 2. V6l-sulf-CDld interaction is prevented by anti-CDld VHH 1D12 and reduced by 1D22. Endogenous or sulfatide loaded CDld-PE tetramers were incubated with either PBS (control), 1D12 or 1D22 (4:1 VHH:CDld ratio) after which tetramers were used to stain Jurkat-V61 cells (final concentration tetramer 2 pg/ml) in combination with CD3-APC. Tetramer binding is prevented by 1D12 and reduced by 1D22 (A). ClR-CDld cells were incubated with DMSO controls or sulfatide (25 pg/ml) after which medium or anti-CDld VHH were added at 1000 or 100 nM and incubated for 30 min. Next Jurkat-V61 cells were added and the co-culture was incubated for an additional 24h after which CD69 expression was determined by flow cytometry (B). N=3.

Fig. 3. Dual activation of iNKT cells and Vy9V62-T cells by a bispecific CDld and Vy9V62-TCR targeting VHH resulting in effector cell degranulation and rapid tumor cell lysis. CDld- expressing CCRF-CEM cells were incubated with either iNKT cells or Vy9V62-T cells or both at an effector to target ratio of 1:2 in the presence of medium only, monovalent 1D12 or bispecific 1D12-5C8. Robust degranulation (as depicted by CD107a expression) of iNKT cells in the presence of 1D12 was observed, but only simultaneous degranulation of iNKT cells and Vy9V62-T cells was seen in the presence of the bispecific VHH (A). In accordance, a striking reduction in living CCRF-CEM cells (B) was observed. Data represent mean+SD of 3 individual experiments with iNKT/ Vy9V62-T obtained from different donors.

Fig. 4. Bispecific 1D12-5C8 supports iNKT and Vy9V62-T cell expansion and induces tumor growth control. iNKT, Vy9V62-T or a mixture (2:3 ratio) were incubated with MM.ls-CDld cells at an effector to target ratio of 1:10 in the presence of medium only or bispecific 1D12- 5C8. Clear induction of iIMKT cell expansion was observed, however Vy9V62-T expansion was only observed in the presence of 1D12-5C8 and iNKT cells (A). Noteworthy, tumor growth was contained in the presence of 1D12-5C8 (B). Data represent mean+SD of 3 individual experiments with paired iNKT/ Vy9V62-T obtained from different donors.

Fig. 5. Anti-CDld VHH 1D12 and anti-CDld 51.1 mAb, but not anti-CDld VHH 1D22, interfere with binding of 1D12-5C8 bispecific VHH. CDld transfected multiple myeloma cells (MM. Is) were incubated with for 45 min with PBS (negative control, NC), anti-CDld VHH (1000 nM) or anti-CDld mAb (100 nM) after which PBS (NC) or biotinylated 1D12-5C8 bispecific VHH (100 nM) was added and incubated for an additional 30 min. After extensive washing samples were stained with streptavidin-APC and analyzed by flow cytometry. Data represent mean + SD of 3 individual experiments, ****P < 0.0001, calculated with a two - way analysis of variance with Turkeys's post hoc test.

Fig. 6. Bispecific antibody 1D12-5C8 promotes survival in a mouse multiple myeloma model in the presence of iNKT and/or Vy9V62-T cells. Panel A shows the effects of administration of antibody 1D12-5C8 and/or iNKT cells on survival. Panel B shows the effects of administration of antibody 1D12-5C8 and/or Vy9V62-T cells. Panel C shows the effects of administration of antibody 1D12-5C8 and/or a mixture ("mix") of iNKT and Vy9V62-T cells.

Fig. 7. CDld expression on CLL cells.

CDld expression was measured on CD5 ⁺ CD19 ⁺ lymphocytes from untreated CLL patients and corrected for background fluorescence using fluorescence minus one (FMO) samples. (A) Representative example histogram of CDld expression on CLL cells. (B) CDld expression in the total cohort; each bar represents an individual patient (n=78). The dotted lines indicate CDld ^neg/dim (relative MFI <50), CDld ^low (relative MFI >50 and <150) and CDld ^hlgh (relative MFI >150) expression. CDld expression according to (C) Rai stage (Rai 0: n=25, Rai Ml: n=22, Rai lll-IV: n=6) and (D) IgVH-status (M-CLL: n=26, U-CLL: n=21). Bars represent mean. *P<0.05. (C: one-way ANOVA followed by Holm-Sidak's post hoc test; D: unpaired t-test).

Fig. 8. The bispecific anti-CDld-V62 VHH activates Vy9V62-T cells.

(A, B) Cytokine production and degranulation of Vy9V62-T cells in the presence of the bispecific antibody 1D7-5C8, brefeldin, monensin and anti-CD107a as measured by flow cytometry. (A) Healthy donor-derived Vy9V62-T cells were cultured with medium control, Jeko-l cells (1:1 ratio), bispecific antibody 1D7-5C8 (lOOnM), Jeko-1 cells and bispecific antibody 1D7-5C8 (1:1 ratio, lOpM), or Jeko-1 cells and bispecific antibody 1D7-5C8 (1:1 ratio, lOOpM). Representative plots for 3 experiments. (B) Healthy donor-derived Vy9V62-T cells were cultured with Jeko-1 cells (1:1 ratio) and the indicated concentrations of bispecific antibody 1D7-5C8 (n=3). (B: non-linear regression analysis). Symbols and error bars represent mean and range; vertical line and shaded area represent EC50 and 95% confidence interval. Fig. 9. The bispecific anti-CDld-V62 VHH induces lysis of malignant B cells.

Lysis of target cells after overnight culture with healthy donor-derived Vy9V62-T cells in a 1:1 effector to target ratio in the presence of the indicated concentrations of the bispecific antibody 1D7-5C8. (A) Specific lysis of Jeko-1 cell line (n=3). (B) CDld expression on WT or CDld-transfected MM. Is cell line (blank histogram: CDld-stained, grey filled histogram: fluorescence minus one control). (C) Specific lysis of WT or CDld-transfected MM. Is cell line (n=4). (D) Specific lysis of primary CLL cells with negative, low or high CDld expression (n=4 per group). Specific lysis is calculated by correcting for background cell death in condition without Vy9V62-T cells. Data represent mean and SD. *P <0.05, **P <0.01, ****p <0.0001. (A: one-way ANOVA followed by Dunnett's post hoc test compared to untreated condition, C: two-way ANOVA followed by Sidak's post hoc test comparing WT vs CDld for each concentration, D: two-way ANOVA followed by Tukey's post hoc test comparing each CDld group for each concentration).

Fig. 10. The bispecific anti-CDld-V62 VHH activates Vy9V62-T cells from CLL patients and induces autologous tumor lysis

(A-C) Activation of and cytokine production and degranulation by patient-derived Vy9V62-T cells. PBMCs from CLL patients were enriched for T cells by depletion of CD19 ⁺ CLL cells and then cultured overnight with CD19 ⁺ CLL cells in a 1:1 ratio with bispecific antibody 1D7-5C8 (50nM) or medium control in the presence of brefeldin, monensin and anti-CD107a to measure (A) CD25 expression, (B) cytokine production and (C) degranulation by flow cytometry (n=7). (D) Lysis of primary CLL cells by autologous Vy9V62-T cells. CD3 ⁺ cells were isolated from CLL PBMCs and cultured with total CLL PBMCs in a low (5:1 CD3:PBMC, which equals ± 1:5 V62:CLL) or higher (20:1 CD3:PBIVIC, which equals ± 1:20 V62:CLL) ratio with bispecific antibody 1D7-5C8 (lOnM) or medium control. Live CLL cells were quantified by flow cytometry using counting beads (n=5). (E) Expansion of patient-derived Vy9V62-T cells. PBMCs from CLL patients were enriched for T cells by depletion of CD19 ⁺ CLL cells and then cultured with CD19 ⁺ CLL cells in a 2:1 ratio on irradiated CD40L-expressing fibroblasts with IL- 2 (50IU/mL) or IL-2 and bispecific antibody 1D7-5C8 (50nM). Percentage Vy9V62-T cells after 1 week (n=8). Data are presented as mean and SD. *P <0.05, **P <0.01, ***P <0.001. (A-D: one-way ANOVA followed by Dunnett's post hoc test compared to medium control; E: paired t-test).

Fig. 11. ATRA enhances bispecific antibody lD7-5C8-induced killing by upregulation of CDld expression

(A) CDld expression on Jeko-1 cells after 48 hours of ATRA treatment. (B) Time-curve of CDld expression upon ATRA treatment (n=3). (C) Viability of Jeko-1 cells after 48 hours of treatment with lOOnM ATRA (n=4). (D) Lysis of Jeko-1 cells after pretreatment with ATRA. Jeko-1 cells were treated with lOOnM ATRA or medium control for 48 hours and cultured overnight with healthy donor-derived Vy9V62-T cells in a 1:2 effector to target ratio in the presence of the indicated concentrations of the bispecific antibody 1D7-5C8 (n=4). (E) CDld expression on primary CLL cells after 48 hours of different concentrations of ATRA or medium control treatment (n=17). (F) Lysis of CLL cells after pretreatment with ATRA. Primary CLL cells were treated with lOOnM ATRA or medium control for 48 hours and cultured overnight with healthy donor-derived Vy9V62-T cells in a 1:1 effector to target ratio in the presence of the indicated concentrations of the bispecific antibody 1D7-5C8 (n=6). Specific lysis is calculated by correcting for background cell death in condition without Vy9V62-T cells. Data represent mean and SD. *P <0.05, ***p< 0.001, ****p <0.0001. (C: paired t-test; D, F: two- way ANOVA followed by Sidak's post hoc test comparing control vs ATRA-treated for each concentration; E: Friedman test followed by Dunnett's post hoc test compared to medium control).

Fig. 12. Vy9V62-T cell activation by the bispecific antibody 1D7-5C8 can be modified through modulation of phosphoantigen recognition

(A) Specific lysis of Jeko-1 cells after pretreatment with mevastatin or pamidronate. Jeko-1 cells were treated with 25mM mevastatin, 50mM pamidronate or medium control for 2 hours and cultured for 6 hours with healthy donor-derived Vy9V62-T cells in a 1:2 ratio with lOOnM bispecific antibody 1D7-5C8 (n=3). (B) CDld expression on B cells from healthy donor PBMCs. (C) Specific lysis of healthy B cells and CLL cells after pretreatment with ABP. Healthy B cells (isolated from healthy donor PBMCs, CFSE-labeled) and CLL cells (isolated from CLL PBMCs, CTV-labeled) were mixed in 1:1 ratio and pretreated with 50mM pamidronate or medium control for 2 hours. Target cells were then cultured for 6 hours with healthy donor-derived Vy9V62-T cells in a 1:1:1 (Vy9V62-T cell: B cell: CLL cell) ratio with the indicated concentrations of bispecific antibody 1D7-5C8 (n=4). (D) Specific lysis of Jeko-1 cells after blockade of CDld or CD277. Jeko-1 cells were incubated with an anti-CDld antibody (5pg/mL), anti-CD277 antibody (lOpg/mL), anti-CDld and anti-CD277 antibodies, or medium control for 10 minutes. Target cells were then cultured overnight with healthy donor-derived Vy9V62-T cells in a 1:3 ratio with lOpM bispecific antibody 1D7-5C8 (n=3). Specific lysis is calculated by correcting for background cell death in condition without Vy9V62-T cells. Data represent mean and SD. *P <0.05, **P<0.01, ***p <0.001. (A: two-way ANOVA followed by Dunnett's post hoc test comparing control vs each pretreatment; C: two-way ANOVA followed by Sidak's post hoc test comparing untreated vs ABP pre-treated D: one-way ANOVA followed by Dunnett's post hoc test compared to medium control;).

Detailed description of the invention

Definitions

The term "antibody" as used herein is intended to refer to an immunoglobulin molecule, a fragment of an immunoglobulin molecule, or a derivative of either thereof, which has the ability to specifically bind to an antigen under typical physiological conditions with a half-life of significant periods of time, such as at least about 30 minutes, at least about 45 minutes, at least about one hour, at least about two hours, at least about four hours, at least about 8 hours, at least about 12 hours, about 24 hours or more, about 48 hours or more, about 3, 4, 5, 6, 7 or more days, etc., or any other relevant functionally-defined period (such as a time sufficient to induce, promote, enhance, and/or modulate a physiological response associated with antibody binding to the antigen and/or time sufficient for the antibody to recruit an effector activity). The binding region (or binding domain) which interacts with an antigen, comprises variable regions of both the heavy and light chains of the immunoglobulin molecule. The constant regions of the antibodies (Abs) may mediate the binding of the immunoglobulin to host tissues or factors, including various cells of the immune system (such as effector cells and T cells) and components of the complement system such as Clq, the first component in the classical pathway of complement activation. In some embodiments, however, the Fc region of the antibody has been modified to become inert, "inert" means an Fc region which is at least not able to bind any Fey Receptors, induce Fc- mediated cross-linking of FcRs, or induce FcR-mediated cross-linking of target antigens via two Fc regions of individual proteins, such as antibodies. In a further embodiment, the inert Fc region is in addition not able to bind Clq. In one embodiment, the antibody contains mutations at positions 234 and 235 (Canfield and Morrison (1991) J Exp Med 173:1483), e.g. a Leu to Phe mutation at position 234 and a Leu to Glu mutation at position 235. In another embodiment, the antibody contains a Leu to Ala mutation at position 234, a Leu to Ala mutation at position 236 and a Pro to Gly mutation at position 329.

As indicated above, the term antibody as used herein, unless otherwise stated or clearly contradicted by context, includes fragments of an antibody that retain the ability to specifically interact, such as bind, to the antigen. It has been shown that the antigen-binding function of an antibody may be performed by fragments of a full-length antibody. Examples of binding fragments encompassed within the term "antibody" include (i) a Fab' or Fab fragment, a monovalent fragment consisting of the VL, VH, CL and CHI domains, or a monovalent antibody as described in W02007059782; (ii) F(ab')2 fragments, bivalent fragments comprising two Fab fragments linked by a disulfide bridge at the hinge region; (iii) a Fd fragment consisting essentially of the VH and CHI domains; and (iv) a Fv fragment consisting essentially of the VL and VH domains of a single arm of an antibody. Furthermore, although the two domains of the Fv fragment, VL and VH, are coded for by separate genes, they may be joined, using recombinant methods, by a synthetic linker that enables them to be made as a single protein chain in which the VL and VH regions pair to form monovalent molecules (known as single chain antibodies or single chain Fv (scFv), see for instance Bird et al., Science 242, 423-426 (1988) and Huston et al., PNAS USA 85, 5879-5883 (1988)). Such single chain antibodies are encompassed within the term antibody unless otherwise noted or clearly indicated by context. Although such fragments are generally included within the meaning of antibody, they collectively and each independently are unique features of the present invention, exhibiting different biological properties and utility. These and other useful antibody fragments in the context of the present invention are discussed further herein. It also should be understood that the term antibody, unless specified otherwise, also includes polyclonal antibodies, monoclonal antibodies (mAbs), chimeric antibodies and humanized antibodies, and antibody fragments retaining the ability to specifically bind to the antigen (antigen-binding fragments) provided by any known technique, such as enzymatic cleavage, peptide synthesis, and recombinant techniques. An antibody as generated can possess any isotype.

The term "immunoglobulin heavy chain", "heavy chain of an immunoglobulin" or "heavy chain" as used herein is intended to refer to one of the chains of an immunoglobulin. A heavy chain is typically comprised of a heavy chain variable region (abbreviated herein as VH) and a heavy chain constant region (abbreviated herein as CH) which defines the isotype of the immunoglobulin. The heavy chain constant region typically is comprised of three domains, CHI, CH2, and CH3. The heavy chain constant region may further comprise a hinge region. The term "immunoglobulin" as used herein is intended to refer to a class of structurally related glycoproteins consisting of two pairs of polypeptide chains, one pair of light (L) chains and one pair of heavy (H) chains, all four potentially inter-connected by disulfide bonds. Within the structure of the immunoglobulin (e.g. IgG), the two heavy chains are interconnected via disulfide bonds in the so-called "hinge region". Equally to the heavy chains each light chain is typically comprised of several regions; a light chain variable region (abbreviated herein as VL) and a light chain constant region (abbreviated herein as CL). The light chain constant region typically is comprised of one domain, CL. Furthermore, the VH and VL regions may be further subdivided into regions of hypervariability (or hypervariable regions which may be hypervariable in sequence and/or form structurally defined loops), also termed complementarity determining regions (CDRs), interspersed with regions that are more conserved, termed framework regions (FRs). Each VH and VL is typically composed of three CDRs and four FRs, arranged from amino-terminus to carboxy-terminus in the following order: FR1, CDR1, FR2, CDR2, FR3, CDR3, FR4. CDR sequences may be determined by use of various methods, e.g. the methods provided by Choitia and Lesk (1987) J. Mol. Biol. 196:901 or Kabat et al. (1991) Sequence of protein of immunological interest, fifth edition. NIH publication. Various methods for CDR determination and amino acid numbering can be compared on www.abysis.orR (UCL).

The term "isotype" as used herein, refers to the immunoglobulin (sub)class (for instance IgGl, lgG2, lgG3, lgG4, IgD, IgA, IgE, or IgM) or any allotype thereof, such as IgGlm(za) and IgGlm(f) [SEQ ID IMO:407]) that is encoded by heavy chain constant region genes. Thus, in one embodiment, the antibody comprises a heavy chain of an immunoglobulin of the IgGl class or any allotype thereof. Further, each heavy chain isotype can be combined with either a kappa (K) or lambda (l) light chain.

The term "chimeric antibody" as used herein, refers to an antibody wherein the variable region is derived from a non-human species (e.g. derived from rodents) and the constant region is derived from a different species, such as human. Chimeric antibodies may be generated by antibody engineering. "Antibody engineering" is a generic term used for different kinds of modifications of antibodies, and which is a well-known process for the skilled person. Thus, the chimeric antibody may be a genetically engineered recombinant antibody. Some chimeric antibodies may be both genetically or an enzymatically engineered. It is within the knowledge of the skilled person to generate a chimeric antibody, and thus, generation of a chimeric antibody may be performed by other methods than described herein. Chimeric monoclonal antibodies for therapeutic applications are developed to reduce antibody immunogenicity. They may typically contain non-human (e.g. murine) variable regions, which are specific for the antigen of interest, and human constant antibody heavy and light chain domains. The terms "variable region" or "variable domains" as used in the context of chimeric antibodies, refers to a region which comprises the CDRs and framework regions of both the heavy and light chains of the immunoglobulin.

The term "humanized antibody" as used herein, refers to a genetically engineered nonhuman antibody, which contains human antibody constant domains and non-human variable domains modified to contain a high level of sequence homology to human variable domains. This can be achieved by grafting of the six non-human antibody complementaritydetermining regions (CDRs), which together form the antigen binding site, onto a homologous human acceptor framework region (FR). In order to fully reconstitute the binding affinity and specificity of the parental antibody, the substitution of framework residues from the parental antibody (i.e. the non-human antibody) into the human framework regions (back-mutations) may be required. Structural homology modeling may help to identify the amino acid residues in the framework regions that are important for the binding properties of the antibody. Thus, a humanized antibody may comprise non-human CDR sequences, primarily human framework regions optionally comprising one or more amino acid back-mutations to the non-human amino acid sequence, and fully human constant regions. Optionally, additional amino acid modifications, which are not necessarily back-mutations, may be applied to obtain a humanized antibody with preferred characteristics, such as affinity and biochemical properties. The amino acid sequence of an antibody of non-human origin is distinct from antibodies of human origin, and therefore a non-human antibody is potentially immunogenic when administered to human patients. However, despite the non-human origin of the antibody, its CDR segments are responsible for the ability of the antibody to bind to its target antigen and humanization aims to maintain the specificity and binding affinity of the antibody. Thus, humanization of non-human therapeutic antibodies is performed to minimize its immunogenicity in man while such humanized antibodies at the same time maintain the specificity and binding affinity of the antibody of non-human origin.

The term "multispecific antibody" refers to an antibody having specificities for at least two different, such as at least three, typically non-overlapping, epitopes. Such epitopes may be on the same or different targets if the epitopes are on different targets, such targets may be on the same cell or different cells or cell types.

The term "bispecific antibody" refers to an antibody having specificities for at least two different, typically non-overlapping, epitopes. Such epitopes may be on the same or different targets. If the epitopes are on different targets, such targets may be on the same cell or different cells or cell types. In one embodiment, the bispecific antibody comprises a first and a second heavy chain.

Examples of bispecific antibody molecules which may be used in the present invention comprise (i) a single antibody that has two arms comprising different antigen-binding regions, (ii) a single chain antibody that has specificity to two different epitopes, e.g., via two scFvs linked in tandem by an extra peptide linker; (iii) a dual-variable- domain antibody (DVD- IgTM), where each light chain and heavy chain contains two variable domains in tandem through a short peptide linkage; (iv) a chemically-linked bispecific (Fab')2 fragment; (v) a TandAb ^® , which is a fusion of two single chain diabodies resulting in a tetravalent bispecific antibody that has two binding sites for each of the target antigens; (vi) a flexibody, which is a combination of scFvs with a diabody resulting in a multivalent molecule; (vii) a so called "dock and lock" molecule (Dock-and-Lock ^® ), based on the "dimerization and docking domain" in Protein Kinase A, which, when applied to Fabs, can yield a trivalent bispecific binding protein consisting of two identical Fab fragments linked to a different Fab fragment; (viii) a so-called Scorpion molecule, comprising, e.g., two scFvs fused to both termini of a human Fab-arm; and (ix) a diabody.

Examples of different classes of bispecific antibodies include but are not limited to (i) IgG-like molecules with complementary CH3 domains to force heterodimerization; (ii) recombinant IgG-like dual targeting molecules, wherein the two sides of the molecule each contain the Fab fragment or part of the Fab fragment of at least two different antibodies; (iii) IgG fusion molecules, wherein full length IgG antibodies are fused to extra Fab fragment or parts of Fab fragment; (iv) Fc fusion molecules, wherein single chain Fv molecules or stabilized diabodies are fused to heavy-chain constant- domains, Fc-regions or parts thereof; (v) Fab fusion molecules, wherein different Fab- fragments are fused together, fused to heavy-chain constant-domains, Fc-regions or parts thereof; and (vi) ScFv, diabody-based and heavy chain antibodies (e.g., domain antibodies, Nanobodies ^® ) wherein different single chain Fv molecules or different diabodies or different heavy-chain antibodies (e.g. domain antibodies, Nanobodies ^® ) are fused to each other or to another protein or carrier molecule fused to heavy-chain constant-domains, Fc-regions or parts thereof.

Examples of IgG-like molecules with complementary CH3 domain molecules include but are not limited to the Triomab ^® (Trion Pharma/Fresenius Biotech), the Knobs-into-Holes (Genentech), CrossMAbs (Roche) and the electrostatically-matched (Amgen, Chugai, Oncomed), the LUZ-Y (Genentech, Wranik et al. J. Biol. Chem. 2012, 287(52): 43331-9, doi: 10.1074/jbc.M112.397869. Epub 2012 Nov 1), DIG-body and PIG-body (Pharmabcine,

WO2010134666, W02014081202), the Strand Exchange Engineered Domain body (SEEDbody)(EMD Serono), the Biclonics (Merus, W02013157953), FcAAdp (Regeneron), bispecific IgGl and lgG2 (Pfizer/Rinat), Azymetric scaffold (Zymeworks/Merck,), mAb-Fv (Xencor), bivalent bispecific antibodies (Roche, W02009080254) and DuoBody ^® molecules (Genmab).

Examples of recombinant IgG-like dual targeting molecules include but are not limited to Dual Targeting (DT)-lg (GSK/Domantis, W02009058383), Two-in-one Antibody (Genentech, Bostrom, et al 2009. Science 323, 1610-1614), Cross-linked Mabs (Karmanos Cancer Center), mAb2 (F-Star), ZybodiesTM (Zyngenia, LaFleur et al. MAbs. 2013 Mar-Apr;5(2):208-18), approaches with common light chain, xXBodies (Novlmmune, W02012023053) and CovX- body ^® (CovX/Pfizer, Doppalapudi, V.R., et al 2007. Bioorg. Med. Chem. Lett. 17,501-506).

Examples of IgG fusion molecules include but are not limited to Dual Variable Domain (DVD)-lgTM (Abbott), Dual domain double head antibodies (Unilever; Sanofi Aventis), IgG-like Bispecific (ImClone/Eli Lilly, Lewis et al. Nat Biotechnol. 2014 Feb;32(2):191-8), Ts2Ab (Medlmmune/AZ, Dimasi et al. J Mol Biol. 2009 Oct 30;393(3):672-92) and BsAb (Zymogenetics, W02010111625), HERCULES (Biogen Idee), scFv fusion (Novartis), scFv fusion (Changzhou Adam Biotech Inc) and TvAb (Roche).

Examples of Fc fusion molecules include but are not limited to ScFv/Fc Fusions (Academic Institution, Pearce et al Biochem Mol Biol Int. 1997 Sep;42(6):1179), SCORPION (Emergent BioSolutions/Trubion, Blankenship JW, et al. AACR 100th Annual meeting 2009 (Abstract #5465); Zymogenetics/BMS, W02010111625), Dual Affinity Retargeting Technology (Fc-DARTTM) (MacroGenics) and Dual(ScFv)2-Fab (National Research Center for Antibody Medicine - China).

Examples of Fab fusion bispecific antibodies include but are not limited to F(ab)2

(Medarex/AMGEN), Dual-Action or Bis-Fab (Genentech), Dock-and-Lock ^® (DNL) (ImmunoMedics), Bivalent Bispecific (Biotecnol) and Fab-Fv (UCB-Celltech).

Examples of ScFv-, diabody-based and domain antibodies include but are not limited to Bispecific T Cell Engager (BiTE ^® ) (Micromet, Tandem Diabody (Tandab) (Affimed), Dual Affinity Retargeting Technology (DARTTM) (MacroGenics), Single-chain Diabody (Academic, Lawrence FEBS Lett. 1998 Apr 3;425(3):479-84), TCR-like Antibodies (AIT, ReceptorLogics), Human Serum Albumin ScFv Fusion (Merrimack, W02010059315) and COMBODY molecules (Epigen Biotech, Zhu et al. Immunol Cell Biol. 2010 Aug;88(6):667-75), dual targeting nanobodies ^® (Ablynx, Hmila et al., FASEB J. 2010), dual targeting heavy chain only domain antibodies.

A "binding moiety" in the context of the present invention is an antibody moiety, that is capable of specifically binding to a target. A binding moiety may, e.g., comprise: an intact immunoglobulin molecule such as a monoclonal antibody. Alternatively, the binding moiety can comprise an antigen-binding functional fragment, including, but not limited to, Fab, F(ab'), F(ab')2, Fv, dAb, Fd, a complementarity determining region (CDR) fragment, a single chain antibody (scFv), a divalent single chain antibody, a single chain phage antibody, a bispecific double chain antibody, a triabody, a tetrabody, a single domain antibody (nanobody ^® ), a (poly)peptide containing at least an amino acid sequence that is sufficient to specifically bind to its target, and artificial immunoglobulin fragments, such as plastic antibodies (Hoshino et al (2008) J Am Chem Soc 130(46):15242). In a preferred embodiment, a binding moiety is a single domain antibody. Preferably, a binding moiety of the present invention comprises three heavy chain CDRs.

The term "specifically binds" as used herein, refers to the binding of a binding moiety or antibody to a predetermined antigen or target (e.g. human CDld) to which binding typically is with an affinity corresponding to a K _D of about 10 ⁶ M or less, e.g. Id ⁷ M or less, such as about 10 ⁸ M or less, such as about 10 ⁹ M or less, about 10 ¹⁰ M or less, or about 10 ¹¹ M or even less when determined by for instance surface plasmon resonance (SPR) technology in a BIAcore 3000 instrument using the antigen as the ligand and the binding moiety or antibody as the analyte, and binds to the predetermined antigen with an affinity corresponding to a K _D that is at least ten-fold lower, such as at least 100 fold lower, for instance at least 1,000 fold lower, such as at least 10,000 fold lower, for instance at least 100,000 fold lower than its affinity for binding to a non-specific antigen (e.g., BSA, casein) other than the predetermined antigen or a closely- related antigen. The degree with which the affinity is lower is dependent on the KD of the binding moiety or antibody, so that when the KD of the binding moiety or antibody is very low (that is, the binding moiety or antibody is highly specific), then the degree with which the affinity for the antigen is lower than the affinity for a non-specific antigen may be at least 10,000 fold. The term "KD" (M), as used herein, refers to the dissociation equilibrium constant of a particular interaction between the antigen and the binding moiety or antibody.

In the context of the present invention, "competition" or "able to compete" or "compete" refers to any detectably significant reduction in the propensity for a particular antibody (e.g. a CDld antibody) to bind a particular binding partner (e.g. CDld) in the presence of another molecule (e.g. a different CDld antibody) that binds the binding partner. Typically, competition means an at least about 25 percent reduction, such as an at least about 50 percent, e.g. an at least about 75 percent, such as an at least 90 percent reduction in binding between a CDld antibody or moiety, caused by the presence of another CDld antibody or moiety as determined by, e.g., ELISA analysis or flow cytometry using sufficient amounts of the two or more competing antibodies or moieties. Additional methods for determining binding specificity by competitive inhibition may be found in for instance

Harlow et al., Antibodies: A Laboratory Manual, Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y., 1988), Colligan et al., eds., Current Protocols in Immunology, Greene Publishing Assoc, and Wiley InterScience N. Y., (1992, 1993), and Muller, Meth. Enzymol. 92, 589-601 (1983)). As described above, in a main aspect, the invention provides an antibody comprising a first binding moiety that is able to bind human CDld and a second binding moiety that is able to bind the human Vy9V62-TCR for use in the treatment of Chronic Lymphocytic Leukemia, Multiple Myeloma or Acute Myeloid Leukemia. The term "binds to a Vy9V62-TCR" means that the antibody binds Vy9V62-TCR, but does not exclude that the antibody binds to one of the separate subunits in the absence of the other subunit, i.e. to the Vy9 chain alone or to the V62 chain alone. For example, as can be seen in Table 2 herein, antibody 5C8 is an antibody that binds the Vy9V62-TCR, but also binds the V62 chain when the V62 chain is expressed alone.

The term "first" and "second" binding moiety does not refer to their orientation / position in the antibody, i.e. it has no meaning with regard to the N- or C-terminus. The term "first" and "second" only serves to correctly and consistently refer to the two different binding moieties in the claims and the description. In one preferred embodiment, the first binding moiety and the second binding moiety are coupled to each other through one or more amide bond(s), preferably through a linker, more preferably comprising the amino acids GGGGS (SEQ ID NO: 159). Two, non-limiting, examples of antibodies comprising a first and a second binding moiety linked through a peptide linker (GGGGS), are depicted in Table 1 (SEQ ID NO: 160 and SEQ ID NO: 164). In another preferred embodiment, the antibody is a bispecific antibody, such as a full-length bispecific antibody. The term "full-length antibody" when used herein, refers to an antibody which contains all heavy and light chain constant and variable domains corresponding to those that are normally found in a wild-type antibody of that isotype.

With "able to activate Vy9V62 T cells" in the context of the present invention is meant that Vy9V62 T cells are activated in the presence of the antibody according to the invention, in particular in the presence of a target cell expressing CDld. Preferably the activation of the Vy9V62 T cells is measurable through gene-expression and/or (surface) marker expression (e.g., activation markers, such as CD25, CD69, or CD107a) and/or secretory protein (e.g., cytokines or chemokines) profiles. In a preferred embodiment, the antibody is able to induce activation (e.g. upregulation of CD69 and/or CD25 expression) resulting in degranulation (marked by an increase in CD107a expression; Example 3) and cytokine production (e.g. TNFa, IFNy) by Vy9V62 T cells. Preferably activation of Vy9V62 T cells takes place in vivo, particularly in a human body that has been administered an antibody according to the invention and which human body comprises Vy9V62 T cells and preferably CDld+ target cells. Preferably, an antibody of the present invention is able to increase CD107a expression on Vy9V62 T cells to at least 10%, more preferably at least 20%, more preferably at least 40%, most preferably at least 90%, when used in an assay as described in Example 3, wherein e.g. 10% means that 10% of the total number of cells is positive for CD107a. In another embodiment, the number of cells positive for CD107a is increased 1.5-fold, such as 2-fold, e.g. 5-fold, in the presence of an antibody used in the method of the invention.

Similarly, for iNKT cells, "able to activate" in the context of the present invention means that iNKT cells behave differently in the presence of an antibody for use according to the invention, in particular in the presence of a CDld molecule, preferably in the presence of a CDld molecule on a cell surface. Markers, such as CD25 (Example 1), CD69, CD107a (Example 3), or cytokines / chemokines, such as IFNy (Example 1), TNFa, IL-2, are used to determine whether iNKT cells are activated. Preferably the activation of iNKT cells takes place in vivo, particularly in a human body that has been administered an antibody according to the invention and which human body comprises iNKT cells and preferably CDld+ target cells. With CDld+ target cells are meant CDld+ cells that contribute to disease pathogenicity and not normal CDld-expressing cells. Preferably an antibody of the present invention is able to increase CD107a expression on iNKT cells to at least 20%, more preferably to at least 30%, most preferably to at least 40%, when used in an assay as described in Example 3, wherein e.g. 10% means that 10% of the total number of cells is positive for CD107a. In another embodiment, the number of cells positive for CD107a is increased 1.5-fold, such as 2-fold, e.g. 5-fold, in the presence of an antibody used in the method of the invention. Furthermore, preferably an antibody used in the present invention is able to increase CD25 expression on iNKT cells to at least 10 fold, more preferably to at least 20 fold, most preferably to at least 30 fold compared to a "vehicle" control, as measured mean fluorescence intensity by flow cytometry, using allophycocyanin (APC) -conjugated CD25 in a FACS, when used in an assay as described in Example 1. Preferably, an antibody of the present invention is able to increase IFNy expression by iNKT cells at least 1.5-fold, such as at least 2-fold or at least 3-fold, when used in an assay as described in Example 1. Further aspects and embodiments of the invention

As described above, in a first main aspect, the invention provides an antibody comprising a first binding moiety that is able to bind human CDld and a second binding moiety that is able to bind the human Vy9V62-TCR for use in the treatment of Chronic Lymphocytic Leukemia, Multiple Myeloma or Acute Myeloid Leukemia.

The antibody used in the invention is thus a multispecific antibody. The antibody may be bispecific or comprise even further binding moieties capable of binding an antigen. Several antibodies that are able to bind human CDld have been described in W02016122320. These antibodies are, non-limiting, examples of the sequences that may be used in as first binding moiety in the antibody used in the invention. These antibodies, VHH 1 - VHH 21, are depicted in Table 1.

The second binding moiety is able to bind to a Vy9V62-TCR, preferably to the V62 chain. Several such antibodies, which bind to the V62 chain or the Vy9 chain of the TCR have been described in W02015156673 and are depicted in Table 1 and Table 2. Table 1 Designation of VHH (CDR), TCR chains, and sequences of the various VHHs comprised within an antibody used in the invention.

Table 2: From W02015156673: Binding of VHHs to gd T- cells expressing a Vy9 or V52 chain (paired with a non V62 or Vy9 chain respectively ), expressing the complete Vy9V62 TCR, or

and 20 and "++" indicates an MFI above 20.

In one embodiment of the invention, the antibody is for use in combination with a further agent, e.g. a further therapeutic agent. In one embodiment, the antibody is for use in combination with a compound capable of upregulating CDld expression, such as all-trans retinoic acid (ATRA). The ability of a compound to upregulate CDld expression may, e.g. be evaluated using the methods described in Li et al. (2014) Blood 124:2201.

In a further embodiment, the antibody is for use in combination with a compound capable of upregulating CDld expression, such as all-trans retinoic acid, and an EZH2 inhibitor, e.g. tazemetostat. In another embodiment, the antibody is for use in combination with an aminobisphosphonate.

In another embodiment of the invention, the antibody is for use in an elderly patient, such as a patient of above 65 years of age, such as above 70 years of age.

In a further embodiment, the invention relates to a method for the treatment of Chronic Lymphocytic Leukemia (CCL), comprising the steps of:

i) selecting a CDld+ CLL patient, and

ii) administration of an antibody comprising a first binding moiety that is able to bind human CDld and a second binding moiety that is able to bind to the human Vy9V62-TCR to said patient. Selection of a CDld+ CLL patient may be performed by characterizing CLL cells from said patients using the assay described in the Examples herein.

The antibody may have any antibody format suitable for the indicated uses. However, in a preferred embodiment, the first and/or second binding moiety of the antibody is a single domain antibody. Single domain antibodies (sdAb, also called Nanobody ^® , or VHH) are well known to the skilled person. Single domain antibodies comprise a single CDR1, a single CDR2 and a single CDR3. Examples of single domain antibodies are variable fragments of heavy chain only antibodies, antibodies that naturally do not comprise light chains, single domain antibodies derived from conventional antibodies, and engineered antibodies. Single domain antibodies may be derived from any species including mouse, human, camel, llama, shark, goat, rabbit, and cow. For example, naturally occurring VHH molecules can be derived from antibodies raised in Camelidae species, for example in camel, dromedary, alpaca and guanaco.

Like a whole antibody, a single domain antibody is able to bind selectively to a specific antigen. Single domain antibodies may contain only the variable domain of an immunoglobulin chain, i.e. CDR1, CDR2 and CDR3 and framework regions. With a molecular weight of only about 12-15 kDa, single domain antibodies are much smaller than common antibodies (150-160 kDa) which are composed of two heavy chains and two light chains or even Fab fragments (53 kDa), composed of one light chain and part of a heavy chain. The format of a single domain antibody has the advantage of less steric hindering when bound to its target.

In one embodiment, the antibody used in the invention is able to compete with a single domain antibody having a sequence according to any one of SEQ ID NOs: 64-84 in binding to human CDld, preferably wherein the antibody binds to the same epitope on human CDld as a single domain antibody having a sequence according to any one of SEQ ID NOs: 64-84. Methods for determining the epitope of an antibody are known in the art.

In another embodiment, the antibody is able to activate iNKT cells. The inventors have shown that antibody 1D12 (VH H 12) is able to activate iNKT cells, irrespective of the presence of an exogenous ligand for iNKT cells, such as a-galactosylceramide. The present invention further provides the insight that CDld recognition by V61+ T cells can be blocked by such antibodies and that the presence of a second binding moiety in an antibody according to the invention enables the activation of V62+ T cells. Such triple acting antibody, i.e. capable of reducing activation of CDld-restricted V61+ T cells and activating iNKT cells, and at the same time allowing activation of V62+ T cells, create a micro-environment that is skewed towards a Thl-type anti-tumor response. The reduced activation of V61+ T cells, the activation of iNKT cells, and the activation of V62+ T cells synergize towards a tumor- aggressive micro-environment promoting effective tumor-cell killing. In another embodiment, the antibody used in the invention is able to reduce V61 T cell activation. Reducing V6l T cell activation in this context means that a V6l T cell is no longer able to recognize its ligand on a CDld molecule that is bound to an antibody as defined in the invention. Such reduced V61 T cell activation can, e.g., be determined by measuring the expression of activation marker CD69 on V61+ T cells. Lower CD69 expression levels are observed in less activated V61+ T cells, e.g., Jurkat cells as used in Example 2. In particular when used in the context of V61+ tumor cells, blocking means that the presence of the antibody according to the invention has a negative impact on tumor cell growth and/or viability. Preferably, CD69 expression on Jurkat cells is increased less than 5-fold, such as less than 2-fold by an antibody according to the invention, as compared to "vehicle" control when tested in an assay as described in Example 2.

In a further embodiment, the first binding moiety of the antibody comprises:

i) CDR1, CDR2 and CDR3 sequences according to SEQ ID NO: 1, 2 and 3, respectively, ii) CDR1, CDR2 and CDR3 sequences according to SEQ ID NO: 4, 5 and 6, respectively, iii) CDR1, CDR2 and CDR3 sequences according to SEQ ID NO: 7, 8 and 9, respectively, iv) CDR1, CDR2 and CDR3 sequences according to SEQ ID NO: 10, 11 and 12, respectively, v) CDR1, CDR2 and CDR3 sequences according to SEQ ID NO: 13, 14 and 15, respectively, vi) CDR1, CDR2 and CDR3 sequences according to SEQ ID NO: 16, 17 and 18, respectively, vii) CDR1, CDR2 and CDR3 sequences according to SEQ ID NO: 19, 20 and 21, respectively, viii) CDR1, CDR2 and CDR3 sequences according to SEQ ID NO: 22, 23 and 24, respectively, ix) CDR1, CDR2 and CDR3 sequences according to SEQ ID NO: 25, 26 and 27, respectively, x) CDR1, CDR2 and CDR3 sequences according to SEQ ID NO: 28, 29 and 30, respectively, xi) CDR1, CDR2 and CDR3 sequences according to SEQ ID NO: 31, 32 and 33, respectively, xii) CDR1, CDR2 and CDR3 sequences according to SEQ ID NO: 34, 35 and 36, respectively, xiii) CDR1, CDR2 and CDR3 sequences according to SEQ ID NO: 37, 38 and 39, respectively, xiv) CDR1, CDR2 and CDR3 sequences according to SEQ ID NO: 40, 41 and 42, respectively, xv) CDR1, CDR2 and CDR3 sequences according to SEQ ID NO: 43, 44 and 45, respectively, xvi) CDR1, CDR2 and CDR3 sequences according to SEQ ID NO: 46, 47 and 48, respectively, xvii) CDR1, CDR2 and CDR3 sequences according to SEQ ID NO: 49, 50 and 51, respectively, xviii)CDRl, CDR2 and CDR3 sequences according to SEQ ID NO: 52, 53 and 54, respectively, xix) CDR1, CDR2 and CDR3 sequences according to SEQ ID NO: 55, 56 and 57, respectively, xx) CDR1, CDR2 and CDR3 sequences according to SEQ ID NO: 58, 59 and 60, respectively, or xxi) CDR1, CDR2 and CDR3 sequences according to SEQ ID NO: 61, 62 and 63, respectively.

CDR1, CDR2 and CDR3 sequences or framework regions may be exchanged between species. For example, from a llama immunoglobulin molecule, CDR sequences may be selected and exchanged with CDR sequences in a human immunoglobulin molecule, to obtain a human immunoglobulin molecule having the specificity that is derived from the llama CDR sequences. This may be advantageous as a human sequence may be less immunogenic to humans as compared to an antibody containing the original llama framework sequence. Such an exchange of sequences is known as humanization. Hence, the immunoglobulin molecules as provided by the invention may have human derived immunoglobulin sequences or immunoglobulin sequences derived from other animals, such as but not limited to: camelid, llama, shark, and have the CDR1, CDR2 and CDR3 sequences replaced with the CDR sequences according to the invention in order to provide for human CDld binding. In other words, the antibody according to the invention may comprise a humanized single-domain antibody with CDRs as disclosed herein. For example, a single domain antibody may have human framework sequences and CDR regions as disclosed herein.

In a further embodiment, first binding moiety of the antibody comprises any one of the sequences set forth in SEQ ID NOs: 64-84 or 161.

As described, the antibody used in the invention is able to bind the human Vy9V62-TCR. In one embodiment, the antibody is able to bind Vy9, while in another embodiment, the antibody is able to bind V62.

In one embodiment, the antibody is able to compete with a single domain antibody having a sequence according to any one of SEQ ID NOs: 139-156 in binding to the human Vy9V62-TCR, preferably wherein the antibody binds to the same epitope on the human Vy9V62-TCR as a single domain antibody having a sequence according to any one of SEQ ID

NOs: 139-156. Thus, further provided is an antibody for use according to the invention, wherein the second binding moiety is able to compete with binding to a Vy9V62-TCR with single domain antibody 5E3 (SEQ ID NO: 139), 6H1 (SEQ ID NO: 140), 5G3 (SEQ ID NO: 141), 5C1 (SEQ ID NO: 142), 5D3 (SEQ ID NO: 143), 6E3 (SEQ ID NO: 144), 6H4 (SEQ ID NO: 145), 6C1 (SEQ ID NO: 146), 6H3 (SEQ ID NO: 147), 6G3 (SEQ ID NO: 148), 5C8 (SEQ ID NO: 149), 5F5 (SEQ ID NO:

150), 6A1 (SEQ ID NO: 151), 6E4 (SEQ ID NO: 152), 5C7 (SEQ ID NO: 153), 5D7 (SEQ ID NO: 154), 5B11 (SEQ ID NO: 155), or 6C4 (SEQ ID NO: 156). Preferably, the second binding moiety binds to the same epitope sequence as recognized by binding moiety 5E3, 6H1, 5G3, 5C1, 5D3, 6E3, 6H4, 6C1, 6H3, 6G3, 5C8, 5F5, 6A1, 6E4, 5C7, 5D7, 5B11 or 6C4.

In a further embodiment, the second binding moiety comprises:

i) CDR1, CDR2 and CDR3 sequences according to SEQ ID NO:85, 86 and 87, respectively, ii) CDR1, CDR2 and CDR3 sequences according to SEQ ID NO:88, 89 and 90, respectively, iii) CDR1, CDR2 and CDR3 sequences according to SEQ ID NO:91, 92 and 93, respectively, iv) CDR1, CDR2 and CDR3 sequences according to SEQ ID NO: 94, 95 and 96, respectively, v) CDR1, CDR2 and CDR3 sequences according to SEQ ID NO: 97, 98 and 99, respectively, vi) CDR1, CDR2 and CDR3 sequences according to SEQ ID NO:100, 101 and 102, respectively, vii) CDR1, CDR2 and CDR3 sequences according to SEQ ID NO:103, 104 and 105, respectively, viii) CDR1, CDR2 and CDR3 sequences according to SEQ ID NO:106, 107 and 108, respectively, ix) CDR1, CDR2 and CDR3 sequences according to SEQ ID NO:109, 110 and 111, respectively, x) CDR1, CDR2 and CDR3 sequences according to SEQ ID NO:112, 113 and 114, respectively, xi) CDR1, CDR2 and CDR3 sequences according to SEQ ID NO:115, 116 and 117, respectively, xii) CDR1, CDR2 and CDR3 sequences according to SEQ ID NO:118, 119 and 120, respectively, xiii) CDR1, CDR2 and CDR3 sequences according to SEQ ID NO:121, 122 and 123, respectively, xiv) CDR1, CDR2 and CDR3 sequences according to SEQ ID NO:124, 125 and 126, respectively, xv) CDR1, CDR2 and CDR3 sequences according to SEQ ID NO:127, 128 and 129, respectively, xvi) CDR1, CDR2 and CDR3 sequences according to SEQ ID NO:130, 131 and 132, respectively, xvii) CDR1, CDR2 and CDR3 sequences according to SEQ ID NO:133, 134 and 135, respectively, or xviii)CDRl, CDR2 and CDR3 sequences according to SEQ ID NO:136, 137 and 138, respectively.

In a further embodiment, second binding moiety of the antibody comprises any one of the sequences set forth in SEQ ID NOs: 139-156 or 162 or 163. In a further embodiment, the antibody comprises the sequence set forth in SEQ ID NO: 164.

In a further embodiment, the antibody comprises a further tumor targeting moiety. A tumor-targeting moiety comprises a binding moiety that is able to specifically bind to a tumor antigen. Tumor antigens are proteins that are produced by tumor cells that elicit an immune response, particularly T-cell mediated immune responses. The selection of the antigen binding moiety will depend on the particular type of cancer to be treated. Tumor antigens are well known in the art and include, for example a glioma-associated antigen, carcinoembryonic antigen (CEA), EGFRvlll, Interleukin- 11 receptor alpha (IL-I IRa), Interleukin- 13 receptor subunit alpha-2 (IL-13Ra or CD213A2), epidermal growth factor receptor (EGFR), B7H3 (CD276), Kit (CD117), carbonic anhydrase (CA-IX), CS-1 (also referred to as CD2 subset 1), Mucin 1, cell surface associated (MUC1), BCMA, oncogene fusion protein consisting of breakpoint cluster region (BCR) and Abelson murine leukemia viral oncogene homolog 1 (Abl) bcr-abl, Receptor tyro sine-protein kinase ERBB2 (HER¾/neu), b-human chorionic gonadotropin, alphafetoprotein (AFP), anaplastic lymphoma kinase (ALK), CD19, CD123, cyclin Bl, lectin-reactive AFP, Fos-related antigen 1, adrenoceptor beta 3 (ADRB3), thyroglobulin, tyrosinase; ephrin type-A receptor 2 (EphA2), Receptor for Advanced Glycation End products (RAGE-1), renal ubiquitous 1 (RU1), renal ubiquitous 2 (RU2), synovial sarcoma, X breakpoint 2 (SSX2), A kinase anchor protein 4 (AKAP-4), lymphocyte-specific protein tyrosine kinase (LCK), proacrosin binding protein sp32 (OY-TES1), Paired box protein Pax-5 (PAX5), Squamous Cell Carcinoma Antigen Recognized By T Cells 3 (SART3), C-type lectin-like molecule- 1 (CLL-1 or CLECL1), fucosyl GM1, hexasaccharide portion of globoH glycoceramide (GloboH), MN-CA IX, Epithelial cell adhesion molecule (EPCAM), EVT6-AML, transglutaminase 5 (TGS5), human telomerase reverse transcriptase (hTERT), polysialic acid, placenta-specific 1 (PLAC1), intestinal carboxyl esterase, LewisY antigen, sialyl Lewis adhesion molecule (sLe), lymphocyte antigen 6 complex, locus K 9 (LY6K), heat shock protein 70-2 mutated (mut hsp70-2), M-CSF, v-myc avian, myelocytomatosis viral oncogene neuroblastoma derived homolog (MYCN), Ras Homolog Family Member C (RhoC), Tyrosinase-related protein 2 (TRP-

2), Cytochrome P450 1B1 (CYP1B1), CCCTC-Binding Factor (Zinc Finger Protein)-Like (BORIS or Brother of the Regulator of Imprinted Sites), prostase, prostate-specific antigen (PSA), paired box protein Pax-3 (PAX3), prostatic acid phosphatase (PAP), Cancer/testis antigen 1 (IMY-ESO-1), Cancer/testis antigen 2 (LAGE-la), LMP2, neural cell adhesion molecule (NCAM), tumor protein p53 (p53), p53 mutant, Rat sarcoma (Ras) mutant, glycoprotein 100 ( gplOO), prostein, OR51E2, pannexin 3 (PANX3), , prostate stem cell antigen (PSCA),high molecular weight-melanoma-associated antigen (HMWMAA), Hepatitis A virus cellular receptor 1 (HAVCRI), vascular endothelial growth factor receptor 2 (VEGFR2), Platelet-derived growth factor receptor beta (PDGFR-beta), legumain, human papilloma virus E6 (HPV E6), human papilloma virus E7 (HPV E7), survivin, telomerase, sperm protein 17 (SPA17), Stage- specific embryonic antigen-4 (SSEA-4), tyrosinase, TCR Gamma Alternate Reading Frame Protein (TARP), Wilms tumor protein (WT1), prostate-carcinoma tumor antigen- 1 (PCTA-1), melanoma inhibitor of apoptosis (ML-IAP), MAGE, Melanoma-associated antigen 1 (MAGE- Al), melanoma cancer testis antigen-1 (MAD-CT-1), melanoma cancer testis antigen-2 (MAD- CT-2), melanoma antigen recognized by T cells 1 (MelanA/MARTI), X Antigen Family, Member 1A (XAGE1), elongation factor 2 mutated (ELF2M), ERG (TMPRSS2 ETS fusion gene), N-Acetyl glucosaminyl-transferase V (NA17), neutrophil elastase, sarcoma translocation breakpoints, mammary gland differentiation antigen (NY-BR-1), ephrinB2, CD20, CD22, CD24, CD30, CD33, CD38, CD44v6, CD97, CD171, CD179a, androgen receptor, insulin growth factor (IGF)-I, IGF-II, IGF-I receptor, ganglioside GD2 (GD2), o-acetyl-GD2 ganglioside (OAcGD2), ganglioside GD3 (aNeu5Ac(2-8)aNeu5Ac(2-3)bDGalp(l -4)bDGIcp(l-l)Cer), ganglioside GM3 (al\leu5Ac(2-

3)bDGa3p(l-4)bDGIcp(l-l)Cer), G protein-coupled receptor class C group 5, member D (GPRC5D), G protein-coupled receptor 20 (GPR20), chromosome X open reading frame 61

(CXORF61), folate receptor (FRa), folate receptor beta, Receptor tyrosine kinase-like orphan receptor 1 (ROR1), Fms-Like Tyrosine Kinase 3 (Flt3), Tumor-associated glycoprotein 72 (TAG72), Tn antigen (TN Ag or (GalNAca-Ser/Thr)), angiopoietin-binding cell surface receptor 2 (Tie 2), tumor endothelial marker 1 (TEM1 or CD248), tumor endothelial marker 7- related (TEM7R), claudin 6 (CLDN6), thyroid stimulating hormone receptor (TSHR), uroplakin 2 (UPK2), mesothelin, Protease Serine 21 (Testisin or PRSS21), epidermal growth factor receptor (EGFR), fibroblast activation protein alpha (FAP), Olfactory receptor 51E2 (OR51E2), ETS translocation-variant gene 6, located on chromosome 12p (ETV6-AML), CD79a; CD79b; CD72; Leukocyte-associated immunoglobulin-like receptor 1 (LAIR1); Fc fragment of IgA receptor (FCAR or CD89); Leukocyte immunoglobulin-like receptor subfamily A member 2 (LILRA2); CD300 molecule-like family member f (CD300LF); C-type lectin domain family 12 member A (CLEC12A); bone marrow stromal cell antigen 2 (BST2); EGF-like module- containing mucin-like hormone receptor-like 2 (EMR2); lymphocyte antigen 75 (LY75); Glypican-3 (GPC3); Fc receptor-like 5 (FCRL5); immunoglobulin lambda-like polypeptide 1 (IGLL1); folate receptor (FRot); mesothelin; EGFR variant III (EGFRvlll); B-cell maturation antigen (BCMA); GD2; CLL-1; CA-IX; MUC1; HER2; and any combination thereof. In one preferred embodiment, the tumor antigen is selected from the group consisting of folate receptor (FRct), mesothelin, EGFRvlll, IL-13Ra, CD123, CD19, CD33, BCMA, GD2, CLL-1, CA-IX, MUC1, HER2, and any combination thereof. In one embodiment, the tumor targeting moiety is an immunoglobulin that specifically binds to PD-L1, EGFR, CD40, Fler2, MUC-1, CEA, c-met, CD19, CD20, BCMA, Her3, AFP, CAIX, or CD38.

Pharmaceutical compositions, dosages, modes of administration and methods of treatment Polypeptides, such as antibodies may be formulated with pharmaceutically acceptable carriers or diluents as well as any other known adjuvants and excipients in accordance with conventional techniques such as those disclosed in (Rowe et al., Handbook of Pharmaceutical Excipients, 2012 June, ISBN 9780857110275). The pharmaceutically acceptable carriers or diluents as well as any other known adjuvants and excipients should be suitable for the polypeptides or antibodies and the chosen mode of administration. Suitability for carriers and other components of pharmaceutical compositions is determined based on the lack of significant negative impact on the desired biological properties of the chosen compound or pharmaceutical composition of the present invention (e.g., less than a substantial impact (10% or less relative inhibition, 5% or less relative inhibition, etc.) upon antigen binding). A pharmaceutical composition may also include diluents, fillers, salts, buffers, detergents (e.g., a nonionic detergent, such as Tween-20 or Tween-80), stabilizers (e.g., sugars or protein-free amino acids), preservatives, tissue fixatives, solubilizers, and/or other materials suitable for inclusion in a pharmaceutical composition. Further pharmaceutically acceptable excipients and carriers include any and all suitable solvents, dispersion media, coatings, antibacterial and antifungal agents, isotonicity agents, antioxidants and absorption-delaying agents, and the like that are physiologically compatible with an antibody of the present invention.

The invention provides methods of treating a disease or disorder comprising administering antibodies as defined herein to a subject in need thereof. In one embodiment, the subject is human. The method of the invention involves administering an effective amount of the antibodies. "Treatment" or "treating" refers to the administration of an effective amount of a therapeutically active polypeptide according to the present invention with the purpose of easing, ameliorating, arresting or eradicating (curing) symptoms or disease states. An "effective amount" or "therapeutically effective amount" refers to an amount effective, at dosages and for periods of time necessary, to achieve a desired therapeutic result. A therapeutically effective amount of a polypeptide, such as an antibody, may vary according to factors such as the disease stage, age, sex, and weight of the individual, and the ability of the antibody to elicit a desired response in the individual. A therapeutically effective amount is also one in which any toxic or detrimental effects of the antibody or antibody portion are outweighed by the therapeutically beneficial effects.

Administration may be carried out by any suitable route, but will typically be parenteral, such as intravenous, intramuscular or subcutaneous. Effective dosages and the dosage regimens for the antibody, depend on the disease or condition to be treated and may be determined by the persons skilled in the art.

Antibodies used in the present invention may also be administered in combination therapy, i.e., combined with other therapeutic agents relevant for the disease or condition to be treated. Accordingly, in one embodiment, the antibody-containing medicament is for combination with one or more further therapeutic agents, such as cytotoxic, chemotherapeutic or anti-angiogenic agents. Such combined administration may be simultaneous, separate or sequential. Thus, in a further embodiment, the present invention provides a method for treating or preventing disease, such as cancer, which method comprises administration to a subject in need thereof of a therapeutically effective amount of an antibody or a pharmaceutical composition of the present invention, in combination with radiotherapy and/or surgery.

Further aspects and embodiments of the invention

In a further aspect, the invention relates to a method for the treatment of Chronic Lymphocytic Leukemia, Multiple Myeloma or Acute Myeloid Leukemia, comprising administration of an antibody comprising a first binding moiety that is able to bind human CDld and a second binding moiety that is able to bind the human Vy9V62-TCR to a human subject in need thereof. In one embodiment, said method has any one of the further features of the antibody or use described herein. Methods of preparing antibodies of the invention

Antibodies used in the invention, such as polypeptides, in particular antibodies, are typically produced recombinantly, i.e. by expression of nucleic acid constructs encoding the polypeptides in suitable host cells, followed by purification of the produced recombinant polypeptide from the cell culture. Nucleic acid constructs can be produced by standard molecular biological techniques well-known in the art. The constructs are typically introduced into the host cell using a vector. Suitable nucleic acid constructs, vectors are known in the art. Host cells suitable for the recombinant expression of polypeptides, such as antibodies are well-known in the art, and include CHO, HEK-293, Expi293F, PER-C6, NS/t) and Sp¾t) cells. Alternatively, expression may be performed in yeast such as Pichia pastoris, Hansenula polymorpha or Saccharomyces cerevisiae or bacteria.

Examples

Materials

Cell lines The human Epstein-Barr virus-transformed B-lymphoblast cell line C1R, stably transduced with CDld, and the human cell line JY were grown in Iscove's modified Dulbecco's medium (catalogue no. 12-722F; Lonza, Basel, Switzerland) supplemented with 10% (v/v) fetal calf serum (catalogue no. SV30160.03; HyClone GE Healthcare, Chalfont, St Giles, UK), 0.05 mm b-mercaptoethanol, 100 lU/ml sodium penicillin, 100 pg/ml streptomycin sulphate and 2.0 mm l-glutamine (catalogue no. 10378-016; Life Technologies, Carlsbad, CA). The human cervical adenocarcinoma cell line HeLa, stably transduced with CDld, was cultured in Dulbecco's modified Eagle's medium (catalogue no. BE12-709F; Lonza) supplemented with 10% (v/v) fetal calf serum, 0.05 mm b-mercaptoethanol, 100 lU/ml sodium penicillin, 100 pg/ml streptomycin sulphate and 2.0 mm l-glutamine. The human myeloma cell line MM. Is with or without mcherry/luc and, stably transduced with CDld, the human acute T- lymphoblastic leukemia cell line CCRF-CEM, the human acute T cell leukemia cell line Jurkat transduced with a V6l sulfatide-CDld restricted TCR, and the human acute myeloid leukemia cell lines MOLM-13 and NOMO-1 were cultured in RPMI-1640 (catalogue no. BE12-115F; Lonza) medium supplemented with 10% (v/v) fetal calf serum, 0.05 mm b-mercaptoethanol, 100 lU/ml sodium penicillin, 100 pg/ml streptomycin sulphate and 2.0 mm l-glutamine. CCRF-CEM and MM. Is genetic characteristics were determined by PCR-single-locus- technology and found identical to the published DNA-profiles. Cells were tested mycoplasma-negative and frequently tested for purity (transfectants) by flow cytometry. Flow cytometry and monoclonal antibodies

The following antibodies were used in this study: fluorescein isothiocyanate (FITC) conjugated V62, FITC CD69, phycoerythrin (PE) and allophycocyanin (APC) -conjugated CD25 (catalogue nos 555432 and #340907), and APC CD3 were purchased from BD Biosciences (Franklin Lakes, NJ). Phycoerythrin-Cyanine 7-conjugated Va24 (catalogue no. PN A66907) and nbΐΐ PE (catalogue no. IM2290) were purchased from Beckman Coulter (Brea, CA). 7-aminoactinomycin D (7-AAD) was purchased from Sigma (St Louis, MO), PE Vy9 from Biolegend (San Diego, USA), PE CD107a from Miltenyi (Miltenyi Biotec, Bergisch Gladbach, Germany) and FITC annexin V from VPS Diagnostics (Hoever, the Netherlands) (catalogue no. A700). Tetramers were made in house. Flow cytometry staining was performed in FACS buffer (PBS supplemented with 0.1% BSA and 0.02% sodium azide) for 30 min at 4°, unless otherwise specified. Samples were analyzed on FACS Fortessa (BD Biosciences).

Generation of DC, iNKT and Vy9V62-T cell lines

moDC and primary human iNKT and gd T cells were generated as described previously (De Bruin et al (2016) Clin Immunol 169:128). Briefly, monocytes were isolated from peripheral blood mononuclear cells with the use of CD14 MicroBeads (Miltenyi Biotec, Bergisch Gladbach, Germany) and cultured in complete RPMI-1640 medium in the presence of 1000 U/ml granulocyte-macrophage colony-stimulating factor (Sanofi Leukine, Bridgewater, NJ) and 20 ng/ml IL-4 (catalogue no. 204-IL/CF; R&D Systems, Minneapolis, MN) for 5-7 days and subsequently matured with 100 ng/ml lipopolysaccharide (LPS) (catalogue no. L6529; Sigma) in the presence or absence of 100 ng/ml ot-GalCer (catalogue no. KRN7000; Funakoshi, Tokyo, Japan) for 48-72 hr. iNKT cells were purified from peripheral blood mononuclear cells of healthy volunteers using magnetic bead sorting, and stimulated weekly with mature a-GalCer-loaded moDC in Yssel's medium supplemented with 1% human AB serum, 10 U/ml IL-7 (catalogue no. 207-IL/CF; R&D Systems) and 10 ng/ml IL-15 (catalogue no. 34-8159; eBioscience). gd T cells were purified from peripheral blood mononuclear cells of healthy volunteers using magnetic bead sorting, and stimulated weekly with pamidronate (10 mM) (PCH, Pharmachemie BV, Haarlem, The Netherlands) loaded moDC in Yssel's medium supplemented with 1% human AB serum, 100 U/ml IL-2 (BioVision, Mountain View, California, USA) 10 U/ml IL-7 and 10 ng/ml IL-15. Alternatively, gd T cells were weekly stimulated with irradiated feeders cells (1x10 ^s mixed PBMC's of two donors and O.lxlO ⁶ JY cells), 10 lU/mL rhlL-7, 10 pg/mL rhlL-15 and 50 ng/mL PHA in in RPMI-1640 medium supplemented as described above. Depending on culture density, cultured cells were split and fresh culture medium was added. Pure (> 95% Va24+ nb11+ or Vy9+ V62+) iNKT and gd T cells were used for experiments.

Generation of anti-CDld and anti-ydTCR specific VHH

The anti-CDld and anti-y6TCR specific VHHs were identified and generated as described previously (Lameris R et al (2016) Immunology 149(1):111; De Bruin et al (2016) Clin Immunol 169:128). Tag-less 1D12 (SEQ ID NO:75), 1D22 (SEQ ID NO:84) and 1D12-5C8 (SEQ ID NO:160) were produced by UPE (Utrecht, the Netherlands).

in vivo xenograft: mouse multiple myeloma (MM) model

A disseminated MM model was established by intravenous transfer of CDld ⁺ MM cells into NOD sold gamma (NSG) mice. Female 18-26-week-old NSG mice (Charles River) were irradiated with 2 Gy 24hr prior to intravenous (i.v.) injection of 2.5xl0 ⁶ MM.ls.mcherry/luc.CDld cells via the tail vain (day 0). On day 7, 14 and 21, lxlO ⁷ human iNKT cells, human gd T cells or a mixture thereof (1:1 ratio) were i.v. injected. Mice were biweekly intraperitoneally (i.p.) injected with PBS or bispecific antibody 1D12-5C8 (100 pg/mouse). Mice were euthanized when pre-set human end-points were reached. Animal experiments were approved by the Dutch Central Authority for Scientific Procedures on Animals (CCD).

Example 1

Modulation of iNKT cell activation

To evaluate the capacity of 1D12 and 1D22 to stimulate or inhibit iNKT cell activation, 5xl0 ⁴ Hela-CDld cells were seeded per well in a 96-well tissue culture plate and pulsed overnight with vehicle control (DMSO 0.01%) or 100 ng/ml a-GalCer. Cells were then washed with PBS and incubated with medium, or the anti-CDld specific VHH for 1 hr at the indicated concentrations. Subsequently, 5*10 ⁴ pure and resting iNKT were added to each well. After 24 hr, culture supernatants were analyzed for (induction or inhibition of) cytokine production by CBA (BD Biosciences) whereas iNKT cells were harvested and analyzed for CD25 expression by flow cytometry. As can be seen in figure 1, we identified an anti-CDld VHH (clone 1D22) that completely blocked iNKT cell activation and cytokine production (P < 0.0001) and thus recognition of the CDld-a-GalCer complex. In sharp contrast anti-CDld VHH clone 1D12 was found to potentiate CDld-restricted iNKT cell activation even in the absence of exogenously added glycolipid Ag (fig. 1 a and c) (P < 0.0001).

Example 2

Modulation of Jurkat-V6l cell activation iNKT cells are known to dock over the extreme F' pocket of CDld which contrasts with sulfatide-CDld restricted V61-T cells that dock more towards the A' pocket. We therefore evaluated the effect of 1D12 and 1D22 on sulfatide-CDld restricted V61-T cells. To evaluate the effect of 1D12 and 1D22 on Jurkat-V61 cell activation, 1x10 ^s ClR-CDld cells were seeded per well in a 96-well tissue culture plate and pulsed for 2 hr with vehicle control (DMSO 0.05%) or 25 pg/ml sulfatide. Cells were then incubated with medium, or the anti-CDld specific VHH for 1 hr at lOOnM (not depicted) or 1000 nM. Subsequently, 5xl0 ⁴ Jurkat-V61 were added to each well. After 24 hr Jurkat-V6l cells were harvested and analysed for CD69 expression by flow cytometry. As can be seen in figure 2B, addition of 1D12 during the co- culture completely abrogated activation of V6l-Jurkat, whereas 1D22 had only a limited impact on expression of the activation marker CD69. Incubation with 100 nM or 1000 nM yielded similar results (data not shown).

To evaluate the effect of 1D12 and 1D22 on CDld-tetramer binding on Jurkat-V6l cells, endogenous or sulfatide-loaded CDld-PE tetramers were incubated with either PBS (control), 1D12 or 1D22 (ratio VHH:CDld of ~4:1) for 30 min at room temperature after which tetramers were added to Jurkat-V6l cells (final concentration tetramer 2 pg/ml) in combination with CD3-APC and incubated for 45 min at 4 degrees Celsius. Data was analyzed by flow cytometry. Incubation of sulfatide-loaded CDld tetramers with 1D12 prevented binding to Jurkat-V6l cells completely, while 1D22 had only a limited impact (figure 2A). These data support the ability of the anti-CDld VHH to modulate reactivity of specific CDld restricted T-cells, which contrast sharply with known mAb, such as 51.1 mAb, that block CDld-TCR interaction of a broad range of CDld-restricted T-cells (Nambiar et al. (2015) MAbs 7:638; Migalovich Sheikhet et al. (2018) Front Immunol 9:753). Example 3

Dual activation of iNKT and Vy9V62-T cells by a bispecific anti-CDld-anti-Vy9V62 TCR VHH Previously, well characterized anti-Vy9V62-TCR VHH have been fused to VHHs specific for tumor-associated antigens for anti-tumor therapeutic purposes. CDld is expressed on various (hematological) malignancies and on tumor associated macrophages and myeloid- derived suppressor cells and could therefore be used as an anti-cancer therapeutic target. To evaluate the ability of 1D12-5C8 to induce dual activation of iIMKT and Vy9V62-T-cells resulting in tumor target lysis, lxlO ⁵ CCRF-CEM cells were incubated with either 5xl0 ⁴ iNKT cells, 5xl0 ⁴ Vy9V62-T cells or 5xl0 ⁴ mixed iNKT/Vy9V62-T (1:1 ratio) in the presence of medium alone, monovalent 1D12 or bispecific 1D12-5C8. After 4 hr degranulation of effector cells was measured by CD107a expression and analyzed by flow cytometry. To asses cytotoxicity towards target cells, living CCRF-CEM cells (Annexin V and 7-AAD negative) were quantified after 16h co-culture using flow cytometry cell counting beads.

To determine the capacity of 1D12-5C8 to support iNKT and Vy9V62-T expansion and control tumor growth, freshly isolated iNKT and Vy9V62-T from the same donor were expanded for 1 week. 5xl0 ⁴ MM.ls-CDld cells were subsequently incubated with medium or 1D12-5C8 (50 nM) for 30 min after which iNKT, Vy9V62-T cells or a mixture thereof (2:3 ratio) was added in a 10:1 target: effector ratio. Living MM.ls-CDld (or MOLM-13 or NOMO-1), iNKT and Vy9V62-T cells (7-AAD negative) were quantified after 7 days using flow cytometry cell counting beads.

As can be seen in figure 3a, robust simultaneous degranulation of iNKT and Vy9V62-T cells was only observed in the presence of the bispecific construct. Moreover, effector cell activation resulted in a striking reduction in living tumor cells (fig. 3b).

The unfavourable effector to target ratio in vivo, usually requires expansion of tumor targeting effector cells to control tumor growth. To investigate whether the bispecific 1D12- 5C8 VHH could induce both effector cell expansion and tumor control in such a setting, MM.ls-CDld cells were incubated with 1D12-5C8, after which iNKT, Vy9V62-T cells or a mixture thereof were added at an effector to target ratio of 1:10. The ability of 1D12-5C8 to induce expansion and control tumor growth was evaluated after a 7 day co-culture by flow cytometric quantification of these cells. As can be seen in figure 4a expansion of iNKT was observed in the presence of the bispecific construct. However, Vy9V62-T cells only showed expansion in the presence of both iNKT cells and the bispecific construct. Moreover, robust tumor growth control was induced by the bispecific construct in combination with effector cells (fig. 4b). Similar, tumor growth control and effector cell expansion were observed with the acute myeloid leukemia tumor cell lines MOLM-13 and NOMO-l (not shown), underscoring the powerful anti-tumor efficacy and broad applicability of this bispecific anti- CDld-anti- Vy9V62-TCR VHH. Example 4

Binding competition of lD12 and 1D12-5C8

To evaluate whether 1D12 binding would interfere with 1D12-5C8 binding, 1x10 ^s MMls- CDld cells were incubated with either PBS (negative control, NC), 1D12 (1000 nM), 1D22 (1000 nM) or anti-CDld mAb 51.1 (100 nM) for 45 min after which PBS (NC) or NHS-biotin (ThermoFischer Scientific Inc., Waltham, MA) linked 1D12-5C8 (100 nM) was added for an additional 30 min at 4 degrees Celsius. After extensive washing samples were stained with streptavidin-APC (eBioscience, San Diego, CA) and analyzed by flow cytometry.

To evaluate competition between 1D12 and 1D12-5C8, CDld expressing MM cells were sequentially incubated with either PBS, 1D12, 1D22 (which should not interfere with 1D12- 5C8 binding) or anti-CDld mAb 51.1) followed by biotinylated 1D12-5C8. The ability of 1D12-

5C8 to complex with CDld was then determined by analysing binding of streptavidin-APC by flow cytometry. As can be seen in figure 5, pre-incubation of 1D12 or anti-CDld mAb 51.1, but not 1D22, greatly reduced 1D12-5C8 binding. Example 5

In vivo xenograft mouse multiple myeloma (MM) model

The anti-tumour efficacy of bispecific CDld/V62 binding antibody 1D12-5C8 was studied in an in vivo model where mice were i.v. inoculated with MM.ls.mCherry/luc.CDld cells to establish a disseminated MM model followed by three i.v. infusions of human iNKT cells, human y6 T cells or a mixture thereof starting 7 days post tumour inoculation whether or not in combination with 1D12-5C8. Whereas biweekly i.p. dosing of 1D12-5C8 alone had no effect (median survival 47 days versus 49.5 days, P>0,05), combination treatment of 1D12- 5C8 and type I NKT cells significantly (p O.0001) prolonged survival compared to iNKT alone (median survival 58.5 days) with all mice being alive at termination of the study (day 90). Compared to treatment with human gd T cells only, treatment of human gd T cells and 1D12- 5C8 showed a trend towards increased median survival from 48 days to 60 days (p=0.16). Infusion of both type I IMKT cells and gd T cells with biweekly i.p. dosing 1D12-5C8 significantly prolonged survival with 7/8 mice being alive at study termination (day 90) (p>0.0001) compared to the mixture of the cells alone without antibody (median survival 55 days).

Example 6 Use of bispecific CDld/Vy9V62 antibodies for the treatment of hematological malignancies

6.1 Materials and methods

Patient and healthy donor material

Peripheral blood mononuclear cells (PBMCs) were isolated from peripheral blood (PB) samples from untreated CLL patients or age-matched healthy control (HC) buffy coats from Sanquin Blood Supply (Amsterdam, the Netherlands) and cryopreserved. The presence of monoclonal B-cell lymphocytosis was excluded in HCs by CD5, CD19, k and l immunophenotyping. Healthy B cells were obtained from HC PBMCs by CD 19 selection (130- 050-301, magnetic microbeads, Miltenyi Biotec, Bergisch Gladbach, Germany). The study was approved by the medical ethics committee at the Amsterdam UMC. Written informed consent from all subjects was obtained in accordance with the Declaration of Helsinki.

Cell lines

Culture medium was supplemented with 10% fetal calf serum (F7524), 0.05 mM b-mercapto- ethanol (M6250, both Merck, Kenilworth, NJ, USA), 200mM L-glutamine (25030-123), and 10,000U/mL penicillin/streptomycin (15140-122, both Thermo Fisher Scientific, Waltham, MA, USA). The multiple myeloma cell line MM. Is, either wildtype (WT) or stably transduced with CDld (kind gift from Dr. W. Song, Dana Farber Cancer Center, Boston, MA, USA) and mantle cell lymphoma cell line Jeko-1 were cultured in Roswell Park Memorial Institute 1640 medium (52400-025, Thermo Fisher Scientific). NIH-3T3 fibroblasts transfected with CD40L were cultured in supplemented Iscove's Modified Dulbecco's Medium (12440-053, Thermo Fisher Scientific). Vy9V62-T cell lines were generated as described previously (de Bruin et al. (2017) Oncoimmunology 7(l):el375641.). In short, V62 ⁺ -T cells were isolated from HC PBMCs using FITC-conjugated anti-V62 TCR (Table 4) in combination with anti-mouse IgG microbeads (130- 048-401, Miltenyi Biotec) and cultured weekly with irradiated feeder mix consisting of PBMCs from 2 HCs, JY cells, IL-7 (10 U/mL, 207-IL-025), IL-15 (10 ng/mL, 247-ILB-25, R&D Systems, Minneapolis, MN, USA) and PHA (50ng/mL, R30852801, Thermo Fisher Scientific). Purity of Vy9V62-T cell lines was maintained at >90%.

Flow cytometry

Cells were stained with antibodies and viability dyes (Table 4) and measured on an LSR Fortessa or FACS Canto cytometer (BD Biosciences, Franklin Lakes, NJ, USA). Samples were analyzed with Flowjo MacVlO. Cytofix/Cytoperm reagent was used for detection of intracellular cytokines (BD Biosciences). Relative CDld expression is defined as geometric MFI (CDld stained) - geometric MFI (fluorescence minus one).

Generation, production and purification of bispecific antibody 1D7-5C8

The CDld-specific VHH 1D7 (SEQ ID NO:70) (W02016122320) and the Vy9V62-specific VHH 5C8 (SEQ ID NO:149) (W02015156673), binding to the V62 chain of the TCR, were previously generated. In short, VHFIs were generated by llama immunization and identified by subsequent phage display and screening. To create the CDld-V62 bispecific VHH, VHH 5C8 (C-terminal) was joined to VHH 1D7 (N-terminal) with a Gly4Ser-linker. Bispecific antibody 1D7-5C8 (SEQ ID NO:165) protein from this gene sequence was produced in mammalian

HEK293E-253 cells by UPE (Utrecht, the Netherlands) and purified from the supernatant by sequential protein A-based selection and size exclusion using fast protein liquid chromatography (AKTAexplorer, GE Healthcare, Chicago, IL, USA).

VHH binding

To assess binding, CDld-transfected MM. Is or Vy9V62-T cell lines were incubated with bispecific antibody 1D7-5C8 for 30 minutes at 37°C. Bound bispecific antibody 1D7-5C8 was detected by sequential incubation with rabbit-anti-llama and PE-conjugated goat-anti-rabbit antibodies for 20 minutes at 4°C (Table 4).

Cytokine and degranulation assays Vy9V62-T cell lines were incubated with bispecific antibody 1D7-5C8 or medium control for 30 minutes at 37°C. Subsequently, Vy9V62-T cells were cocultured with Jeko-1 cells for 4 hours in a 1:1 ratio in the presence of Brefeldin A (10 pg/mL; B7651, Sigma-Aldrich, St. Louis, MO, USA), GolgiStop (554724, BD Biosciences) and anti-CD107a (Table 4).

In the assays with autologous Vy9V62-T cells, CLL PBMCs were partially depleted of CD19 ⁺ cells using magnetic beads (Miltenyi Biotec; after depletion ±50% of cells were CD19 ⁺ ) and then cultured overnight with bispecific antibody 1D7-5C8 or medium control in the presence of Brefeldin A, GolgiStop and anti-CD107a.

Cytotoxicity assays

For cytotoxicity assays, target cells were labeled with carboxyfluorescein succinimidyl ester (CFSE; C1157, Thermo Fisher Scientific) or Cell Trace Violet (CTV; C34557, Thermo Fisher Scientific) and incubated with bispecific antibody 1D7-5C8 or medium control for 30 minutes at 37°C. Target cells were then cocultured overnight with Vy9V62-T cell lines in a 1:1 ratio unless otherwise indicated. Viability was measured using Mitotracker Orange (25-minute incubation at 37°C, M7510) and To-pro-3 (10-minute incubation at room temperature; T3605, both Thermo Fisher Scientific).

If indicated, target cells were pretreated with 25 mM mevastatin (M2537, Sigma-Aldrich), 50 mM aminobisphosphonates (pamidronate, #12J08RD, TEVA Pharmachemie, Haarlem, the Netherlands) or medium control for 2 hours.

If indicated, cells were cultured with the indicated concentrations of all-trans retinoic acid (ATRA; R2625, Sigma-Aldrich) for 48 hours unless otherwise indicated. ATRA was washed away prior to cytotoxicity assays.

If indicated, target cells were pre-incubated with 5pg/mL anti-CDld mAb (clone 51.1, 350304, Biolegend, San Diego, CA, USA) and/or 10pg/mL anti-CD277 mAb (clone 103.2, Creative Biolabs, Shirley, NY, USA) for 10 minutes.

For cytotoxicity assays performed with patient-derived Vy9V62-T cells, CD3 ⁺ cells were enriched from patient PBMC by magnetic bead selection (130-050-101, Miltenyi Biotec; >90% purity). Pure PBMCs were pre-incubated with bispecific antibody 1D7-5C8 or medium control for 30 minutes at 37°C and cultured overnight with purified CD3 ⁺ cells from the same patient in a 5:1 or 20:1 (CD3 ⁺ :PBMC) ratio. Viable cells were then quantified by fluorescence- labeled antibodies and viability dyes in combination with counting beads (01-1234-42, Thermo Fisher Scientific).

Proliferation assays

For proliferation assays, PBMCs from CLL patients were enriched for T cells by depletion of CD19 ⁺ CLL cells. After attachment of irradiated (30Gy) CD40L-expressing fibroblasts to culture plates, T cell enriched PBMC (<10% CD19 ⁺ ) and purified CD19 ⁺ (>90% CD19 ⁺ ) PBMC fractions were added in a 2:1 (CD19 :CD19 ⁺ ) ratio. Cells were cultured in the presence of 50IU/mL IL-2 (200-02, Peprotech, Rocky Hill, NJ, USA) or 50IU/mL IL-2 and 50nM bispecific antibody 1D7- 5C8 for 1 week.

Table 4:

6.2 The majority of CLL patients express CDld on the cell surface

In order to assess the suitability of CDld as a target for antibody-based treatment in CLL, we analyzed CDld surface expression on CLL cells in a cohort of 78 untreated patients. Within each patient sample, CDld was expressed homogenously (Figure 7A). However, the expression of CDld was highly variable across the cohort (median relative MFI 131.2 ±135.1; Figure 7B). We categorized the cohort into three groups, that each contained approximately one-third of the cohort, based on negative or very low (neg/dim) (relative MFI <50), low (relative MFI >50 and <150) or high (relative MFI >150) CDld levels.

CDld expression was higher on CLL cells from patients with advanced stage disease according to Rai classification (Figure 7C). There was no difference in CDld levels between patients with mutated (M-CLL) or unmutated (U-CLL) immunoglobulin heavy chain (IgVH) genes (Figure 7D).

In summary, CDld is expressed on the surface of leukemic cells from approximately two- thirds of CLL patients, particularly in patients with advanced disease.

6.3 Bispecific anti-CDld-V62 VHH induces effector responses of Vy9V62-T cells

Next, we constructed a bispecific anti-CDld Vy9V62-T cell engager by joining the previously generated CDld-specific VHH 1D7 and the V62-specific VHH 5C8 with a Gly4-Ser linker. The previously characterized CDld-specific VHH has a high affinity for CDld, without affecting DC maturation or recognition of glycolipid-loaded CDld by iNKT cells (Lameris et al. (2016) Immunology 149(1):111). Prior characterization of the Vy9V62-T cell-specific VHH demonstrated that it binds to the V62 chain of the TCR and can conditionally activate Vy9V62-T cells (de Bruin et al. (2016) Clin Immunol 169:128).

We first confirmed that binding to CDld and Vy9V62-T cells is retained in the bispecific format. The bispecific antibody 1D7-5C8 bound with high affinity to cultured Vy9V62-T cells (apparent Kd 0.36nM and to CDld-transfected MM. Is cells (apparent Kd 0.40nM), similar to data obtained with our monovalent VHHs (Lameris et al. (2016) Immunology 149(1):111); de Bruin et al. (2016) Clin Immunol 169:128).

Subsequently, we tested whether the bispecific antibody could induce Vy9V62-T cell activation. For this purpose, Vy9V62-T cells were cultured together with Jeko-1 cells, a malignant B cell line that naturally expresses CDld at moderate levels (Li et al. (2014) Med Sci (Basel) 2(2):82). Vy9V62-T cells did not produce IFN-y and hardly degranulated in response to exposure to target cells alone or to the bispecific antibody 1D7-5C8 alone, but this was dose dependently enhanced in cultures containing both Jeko-1 cells and the bispecific antibody 1D7-5C8 (Figure 8A). The half-maximum activating effect on Vy9V62-T cells was reached around 3pM (EC50 IFN-y: 2.6pM, TNF-a: 3.5pM, CD107a: 3.1pM; Figure 8B).

In conclusion, we generated a bispecific anti-CDld-V62 VHH that elicits target cell- dependent Vy9V62-T cell activation at low picomolar concentrations.

6.4 The bispecific antibody 1D7-5C8 promotes CDld-dependent cytotoxicity

We then evaluated whether the activation of Vy9V62-T cells also led to lysis of CDld ⁺ tumor cells. Less than ten percent of Jeko-1 cells were lysed during overnight coculture with Vy9V62-T cells alone. The bispecific antibody 1D7-5C8 enhanced target lysis in a dose- dependent manner, lysing 75.2% ± 21.0 of the Jeko-1 cells in the presence of lOnM bispecific antibody 1D7-5C8 (Figure 9A). The bispecific antibody 1D7-5C8 did not induce target cell lysis in the absence of Vy9V62-T cells.

Next, we analyzed the specificity of bispecific antibody lD7-5C8-induced cytotoxicity using CDld-transfected and wildtype CDld-negative MM. Is cells ⁽ Figure 9B). When the MM. Is cells were exposed to Vy9V62-T cells alone, less than 20% lysis of both the wildtype and CDld ⁺ cells was observed during overnight coculture (Figure 9C). The bispecific antibody 1D7-5C8 clearly increased lysis of the CDld ⁺ cells, but had no effect on lysis of the wildtype cells, demonstrating that the Vy9V62-T cell-mediated cytotoxicity triggered by the bispecific antibody 1D7-5C8 is CDld-specific.

We then tested the efficacy of the bispecific antibody 1D7-5C8 against primary CLL cells in samples with variable CDld expression levels. Again, a minority of CLL target cells was killed when exposed to Vy9V62-T cells alone after overnight coculture (Figure 9D). The bispecific antibody 1D7-5C8 enhanced cytotoxicity against CLL cells with low or high CDld expression, but not with negative CDld expression. Furthermore, CDld ^hlgh CLL cells were more susceptible to bispecific antibody lD7-5C8-induced cell death than CDld ^l0W CLL cells, as lOOnM bispecific antibody 1D7-5C8 induced lysis in 49.3% ± 6.6 of CDld ^low cells versus 74.5% ± 19.1 of CDld ^high cells (P = 0.0083).

Taken together, the bispecific anti-CDld-V62 VHH potently enhances Vy9V62-T cell mediated cytotoxicity against tumor cells in a CDld-dependent manner.

6.5 The bispecific anti-CDld-V62 VHH induces lysis of autologous leukemic cells by Vy9V62- T cells from CLL patients

Since Vy9V62-T cells from CLL patients can be functionally suppressed (de Weerdt et al. (2018) Blood 132(21):2260; Coscia et al. (2012) Blood 120(16):3271), we assessed whether

CLL patient-derived Vy9V62-T cells could be activated by the bispecific antibody 1D7-5C8. Vy9V62-T cells present in the PBMC fraction of CLL patients upregulated the activation marker CD25 on average 20.8-fold upon overnight culture with the bispecific antibody 1D7- 5C8, to a level that was comparable to and not significantly different from that observed when PBMC were cultured with ABP (20.5-fold, Figure 10A).

The bispecific antibody 1D7-5C8 also induced production of IFN-g and TNF-a by the patient-derived Vy9V62-T cells (Figure 10B) and in addition triggered Vy9V62-T cell degranulation (Figure 10C).

Next, we evaluated whether the induction of Vy9V62-T cell effector responses by the bispecific antibody 1D7-5C8 would also enable lysis of autologous leukemic cells. For this purpose, we enriched for Vy9V62-T cells by culturing magnetically isolated CD3 ⁺ cells (>90% purity) together with full PBMCs from the same donor in a CD3:PBMC ratio of 5:1 (±1:20 V62:CLL) or 20:1 (±1:5 V62:CLL) in the presence or absence of the bispecific antibody 1D7- 5C8. Patient-derived Vy9V62-T cells were capable of inducing cell death in autologous CLL cells, with a higher Vy9V62-T celhtumor ratio leading to more leukemic cell death (Figure 10D).

We then determined whether the bispecific antibody 1D7-5C8 could also promote proliferation of Vy9V62-T cells when added to PBMCs from CLL patients enriched for T cells by CD19 magnetic isolation (2:1 CD19 : CD19 ⁺ ratio). After one week of culture in the presence of 50IU/mL IL-2, the percentage of Vy9V62-T cells within the T cell fraction (baseline 1.2% ± 1.0) increased in all 8 samples tested and was 3.1-fold higher with the bispecific antibody 1D7-5C8 (5.6% ± 4.7) than without (1.8% ± 1.5, P = 0.0353, Figure 10E).

Together these data indicate that the bispecific antibody 1D7-5C8 is capable of activating CLL patient-derived Vy9V62-T cells and thereby enables autologous tumor lysis at relatively low E:T ratios and promotes Vy9V62-T cell proliferation.

6.6 ATRA upregulates CDld expression and enhances bispecific anti-CDld-V62 VHH- induced cytotoxicity

ATRA can increase the expression of CDld on B cells (Allan et al. (2011) J Immunol. 186(9):5261). Since the capacity of the bispecific antibody 1D7-5C8 to induce target lysis was dependent on CDld expression levels, we hypothesized that ATRA-induced upregulation of CDld could increase cytotoxicity. ATRA caused upregulation of CDld expression on Jeko-1 cells, which was detectable with lOpM of ATRA and further increased with higher doses (Figure 11A). Peak CDld expression occurred after two days of culture (Figure 11B).

ATRA did not induce cell death directly, nor did ATRA pretreatment increase Vy9V62-T cell- mediated cytotoxicity in the absence of the bispecific antibody (Figure 11C and D). However, Jeko-1 cells that were pretreated with ATRA were more sensitive to bispecific antibody 1D7- 5C8-induced cell death than control Jeko-1 cells (Figure 11D). Next, we tested whether ATRA would also increase CDld expression on primary CLL cells. CDld levels increased 2.6-fold with InM of ATRA and the highest expression occurred with lOOnM ATRA (3.7-fold increase on average, Figure HE). There was considerable variation after ATRA treatment (relative MFI after lOOnM ATRA: 504.6 ±366.0), which could partially be explained by baseline CDld expression (r ² = 0.4025, p = 0.0062).

As with Jeko-1 cells, ATRA pretreatment of primary CLL cells did not affect their sensitivity to Vy9V62-T cell-mediated lysis in the absence of the bispecific antibody 1D7-5C8 (Figure 11F), but did sensitize primary CLL cells to bispecific antibody lD7-5C8-mediated cell death.

In summary, ATRA increased the susceptibility of tumor cells towards Vy9V62-T cell- mediated lysis induced by bispecific anti-CDld-V62 VHH by upregulating CDld expression.

6.7 Modulation of phosphoantigen recognition by Vy9V62-T cells alters bispecific anti- CDld-V62 VHH-induced target lysis

In previous work, we found that the V62-specific VHH 5C8 was not effective in inhibiting phosphoantigen-CD277 mediated Vy9V62-T cell activation (de Bruin et al. (2017) J Immunol. 198(1):308). We therefore wondered whether the level of Vy9V62-T cell activation induced by the bispecific antibody 1D7-5C8 could be affected by residual recognition of the phosphoantigen-CD277 complex. Because the mevalonate pathway is often overactive in malignant cells, we hypothesized that ABP could enhance bispecific antibody 1D7-5C8- induced cytotoxicity specifically against tumor cells.

Jeko-1 cells were more sensitive to Vy9V62-T cell-mediated cytotoxicity following pretreatment with the ABP pamidronate (Figure 12A). In contrast, pretreatment with mevastatin, which reduces intracellular phosphoantigen levels (Boutin et al. (2018) Front Immunol. 9:828), led to a reduction in lysis. A similar pattern was observed in the presence of the bispecific antibody 1D7-5C8, in which pamidronate pretreatment led to an increase in bispecific antibody lD7-5C8-induced lysis of Jeko-1 cells, whilst mevastatin decreased bispecific antibody lD7-5C8-induced lysis. Together, this indicates that the Vy9V62-TCR can still detect phosphoantigens through sensing changes in the conformation of BTN3A1 when the bispecific antibody 1D7-5C8 is bound to the TCR.

Healthy B cells express low levels of CDld (Figure 12B). To test the effects of ABP on CLL and healthy B cells we performed mixed coculture experiments, in which B cells from healthy donors and CLL cells were pretreated with pamidronate for 2 hours and subsequently cultured for six hours with Vy9V62-T cells from a third donor in a 1:1:1 ratio in the presence of the bispecific anti-CDld-V62 VHH. Lysis of healthy B cells by Vy9V62-T cells was minimal, irrespective of ABP pretreatment and the presence of bispecific antibody 1D7-5C8 (lOpM bispecific antibody 1D7-5C8; no ABP: 4.8% ± 0.6, with ABP: 5.4% ± 4.5, Figure 12C). In contrast, while Vy9V62-T cell lysis of CLL cells was triggered by the bispecific antibody 1D7- 5C8, CLL cells were more prone to Vy9V62-T cell lysis in the presence of the bispecific antibody 1D7-5C8 following pamidronate pretreatment (lOpM bispecific antibody 1D7-5C8; no ABP: 19.6% ± 4.8, with ABP: 25.1% ± 5.2).

To further confirm the ability to recognize CD277 in the presence of the bispecific antibody 1D7-5C8 and to assess the relative contribution of bispecific antibody 1D7-5C8- induced versus CD277-Vy9V62 TCR-dependent target cell recognition, we evaluated the effect of blocking CD277 and CDld. The bispecific antibody lD7-5C8-induced cytotoxicity of Jeko-1 cells (29.6% ± 0.9, lysis without bispecific antibody 1D7-5C8 3.7% ± 1.3) was reduced 11.4% on average by a CD277-blocking antibody (clone 103.2 (Harly et al. (2012) Blood 120(11):2269), 18.2% ± 2.0), confirming a remaining role for ligand recognition by the Vy9V62-TCR (Figure 12D). Bispecific antibody lD7-5C8-induced lysis also decreased on average 15.9% with a CDld-blocking antibody (to 13.7% ± 1.0), and declined by 20.2% when CD277 was simultaneously blocked (to 9.4% ± 0.8).

Taken together, these data indicate that the Vy9V62-TCR of Vy9V62-T cells bound to bispecific antibody 1D7-5C8 can still recognize phosphoantigen-induced conformational changes in CD277 on target cells allowing for the potential of a further increase in bispecific antibody lD7-5C8-induced tumor cell lysis in the presence of ABP.