Abstract 5298: BSI-093, a best-in-class anti-BTN3A monoclonal antibody for cancer immunotherapy by activation of Vg9Vd2 T cells

Abstract

Abstract Background: Gamma delta T (γδ T) cells are potent anti-cancer effectors with the potential to target tumors broadly, independent of patient-specific neoantigens or human leukocyte antigen background. Among tumor-infiltrating lymphocytes, the presence of γδ T cells is the most favorable prognostic marker for overall survival of patients with various solid and hematologic tumors. Vγ9Vδ2 T cells are the predominant γδ T cells in peripheral circulation. Butyrophilin 3A (BTN3A) members, widely expressed in tumors, have emerged as novel molecules modulating the function of Vγ9Vδ2 T cells. Targeting BTN3A for activation of Vγ9Vδ2 T cells provides an alternative strategy for cancer immunotherapy. Experimental procedures: BALB/c mice were immunized with recombinant BTN3A1-ECD-Fc. The Biosion proprietary H3 (High-throughput, High-content and High-efficiency) antibody discovery platform was used to identify an anti-BTN3A monoclonal antibody lead candidate - BSI-093. The target binding specificity, binding activity, and affinity of BSI-093 were evaluated by protein-based ELISA, cell-based FACS and Biacore-based SPR. Ex vivo assays were used to evaluate the cellular bioactivity of BSI-093 on activating Vγ9Vδ2 T cells for killing activity of various tumor cells. B-NDG mice bearing Jurkat-GFP-Luc tumors were used to evaluate the tumor inhibitory activity of the anti-BTN3A antibody. Summary: BSI-093 is a humanized monoclonal antibody with the following critical properties: (1) binds to all BTN3A members (BTN3A1, BTN3A2 and BTN3A3) with high affinity; (2) has potentially longer half-life and silenced Fc-effector function by Fc-engineering; (3) exhibits cross-reactivity to rhesus BTN3A members; (4) demonstrates strong activity on activating Vγ9Vδ2 T cells to kill a variety of natural cancer cells in ex vivo assays; and (5) shows significant anti-tumor efficacy in a CDX model. Conclusion: BSI-093 demonstrates potential best-in-class biophysical properties and functional characteristics, supporting the initiation of development activities including manufacturing and IND-enabling studies. Citation Format: Wenwen Dai, Jun Li, Jinyu Liu, Hongyan Li, Xiaodong F. Liu, Shukai Xia, Qun Lyu, Hugh M. Davis, Mingjiu Chen, Zeyu Peng. BSI-093, a best-in-class anti-BTN3A monoclonal antibody for cancer immunotherapy by activation of Vg9Vd2 T cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5298.