A CS1-NKG2D Bispecific Antibody Collectively Activates Cytolytic Immune Cells against Multiple Myeloma

Abstract

Multiple myeloma (MM) is an incurable hematologic malignancy of plasma cells, with an estimated 30,000 new cases diagnosed each year in the United States, signifying the need for new therapeutic approaches. We hypothesized that targeting MM using a bispecific antibody (biAb) to simultaneously engage both innate and adaptive cytolytic immune cells could present potent antitumor activity. We engineered a biAb by fusing an anti-CS1 single-chain variable fragment (scFv) and an anti-NKG2D scFv (CS1-NKG2D biAb). Although NKG2D is a potent activation receptor ubiquitously expressed on mostly cytolytic immune cells including NK cells, CD8 T cells, γδ T cells, and NKT cells, the CS1 tumor-associated antigen on MM represents a promising target. CS1-NKG2D biAb engaged human MM cell lines and NKG2D immune cells, forming immune synapses. In effector cells, CS1-NKG2D biAb triggered the phosphorylation of AKT, a downstream protein kinase of the activated NKG2D-DAP10 complex. The EC values of CS1-NKG2D biAb for CS1 and for CS1 MM cell lines with effector PBMCs were 10 and 10 mol/L, respectively. CS1-NKG2D biAb acted through multiple types of immune cells, and this induced cytotoxicity was both CS1- and NKG2D-specific. , survival was significantly prolonged using CS1-NKG2D biAb in a xenograft NOD-SCID (NSG) mouse model engrafted with both human PBMCs and MM cell lines. Collectively, we demonstrated that the CS1-NKG2D biAb facilitated an enhanced immune synapse between CS1 MM cells and NKG2D cytolytic innate and antigen-specific effector cells, which, in turn, activated these immune cells for improved clearance of MM. .

Targeting Natural Killer Cells for Tumor Immunotherapy

“…Multiple other CD16-directed BiKEs, such as CD16 × Erb-B2 receptor tyrosine kinase 2, CD16 × human epidermal growth factor receptor 2/neu, CD16 × EGFR, CD16 × carcinoembryonic antigen, and CD16 × EpCAM, are under investigation (103). A bi-specific Ab-recognizing CS1-NKG2D, which comprises an anti-NKG2D scFv and an anti-CS1 scFv, showed enhanced cytotoxicity and cytokine production from NK cells and significantly prolonged their survival in a multiple myeloma xenograft NOD-SCID IL2γc−/− (NSG) mouse model (104). A novel CD30/CD16A tetravalent bispecific Ab (AFM13), which has a longer half-life compared with that of other bi-/trispecific Abs, is currently under evaluation in a phase II clinical trial to treat patients with relapsed/refractory Hodgkin's lymphomas (NCT03192202) (105,106).…”

Natural Killer Cell Responses in Hepatocellular Carcinoma: Implications for Novel Immunotherapeutic Approaches

“…More scFvs and IL-15 were further integrated to create tri-and tetra-specific killer cell engagers (TriKEs and TetraKEs) in order to increase therapeutic benefits by targeting more tumor antigens and boost NK cell responses [106,107]. Chan et al created a BiKE containing an anti-CS1scFv and an anti-NKG2D scFv (CS1-NKG2D) that displayed a dose-dependent increase in specific cytotoxicity of NK cells as well as cytokine production in vitro, and significantly prolonged survival in a human multiple myeloma model [108]. In conclusion, BiKEs and TriKEs provide a non-cell-based immunotherapeutic approach that can harness the patients' own NK cells against cancer.…”

Mechanisms of Resistance to NK Cell Immunotherapy

“…Recently, a new generation of NK cell-activating antibodies has been developed [25]. Particularly, bispecific and trispecific killer cell engagers (BiKEs and TRiKEs) that stimulate NK cells against one or more tumor antigens are promising agents that are in preclinical and initial clinical studies [25][26][27]. Similarly, novel mAbs that block NK cell-expressed checkpoint proteins and inhibitory receptors-including PD-1/PD-L1, NKG2A-HLA-E, Tim-3, LAG-3, TIGIT and CD96-are under preclinical and clinical evaluation [8,18,[28][29][30][31][32][33].…”