Abstract 1855: Potent anti-tumor activity against patient CLL, MM and AML by LAVA-051, a bispecific Vγ9Vδ2-T and type 1 NKT cell engager targeting CD1d

Bispecific antibodies that target tumors by engaging innate-like semi-invariant T cell subsets with inherent anti-tumor activity, such as Vγ9Vδ2-T cells and type 1 natural killer T (NKT) cells, may combine high therapeutic efficacy with limited off-tumor toxicity. Type 1 NKT cells respond to self and foreign (glyco)lipid antigens presented in the context of the MHC class I like molecule CD1d which is expressed on various (hematological) malignancies. Vγ9Vδ2-T cells respond to intracellular accumulation of phosphoantigens in cancer cells by sensing conformational alterations in the butyrophilin (BTN)2A1-3A1 complex. By linking a CD1d-specific single domain antibody (VHH) to a Vδ2-TCR specific VHH, we created a bispecific VHH, termed LAVA-051. Besides targeting Vγ9Vδ2-T cells to CD1d-expressing tumor cells, LAVA-051 has the unique ability to also trigger strong activation of type 1 NKT cells in a CD1d-restricted fashion, resulting in potent killing of CD1d-expressing tumor cells by engagement of Vγ9Vδ2-T cells and/or type 1 NKT cells (EC50 1 pM for Vγ9Vδ2-T cells and 216 pM for type 1 NKT cells; >85% target cell lysis in overnight assays at low effector:target ratios of 1:2). LAVA-051 triggered strong activation, pro-inflammatory cytokine production, and proliferation of type 1 NKT and Vγ9Vδ2-T cells and exerted substantial antitumor activity against human primary acute myeloid leukemia (AML), chronic lymphocytic leukemia (CLL) and multiple myeloma (MM) cells that express CD1d. Moreover, improved survival was observed in in vivo AML and MM mouse models. Due to lack of cross-reactivity of LAVA-051 with non-human primate (NHP) CD1d and Vγ9Vδ2-T cells, a cross-reactive surrogate bispecific engager was generated to assess safety, pharmacokinetic (PK) and pharmacodynamic (PD) parameters. Multiple dose studies in NHP (7 daily doses up to 1 mg/kg i.v.) showed clear signs of Vγ9Vδ2-T cell engagement but no clinical, laboratory, or histopathological toxicity. Reflecting the low molecular size of this bispecific engager, PK studies revealed a short plasma half-life which was however compensated for by the prolonged (up to 5 days) binding of the bispecific engager to peripheral blood Vγ9Vδ2-T cells allowing intermittent dosing. Although VHHs have low inherent immunogenicity LAVA-051 was humanized and engineered to avoid binding to pre-existing anti-VHH antibodies that have been reported in ±15% of human individuals and that may limit therapeutic activity. Based on the