Abstract
Abstract BCMA antigen is overexpressed in multiple myeloma cells and has been shown to be a promising target for novel cellular and antibody therapeutics. The humanized BCMA (clone 4C8A) antibody that effectively targeted multiple myeloma in a CAR (chimeric antigen receptor) format was used for designing several formats of bispecific BCMA-CD3 antibodies. Several different designs including univalent and bivalent BCMA-CD3 CrossMAB; triple chain BCMA-FAB-CD3 ScFv-Fc and tetravalent BCMA ScFv-CD3 ScFv-Fc antibodies were tested for affinity and binding with BCMA-positive cells and T cells. Real time cytotoxic activity (RTCA) and IFN-gamma secretion were also tested with multiple myeloma and CHO-BCMA target cells. All BCMA bispecific antibody designs demonstrated specific affinity with CHO-BCMA but not CHO cells in the nanoM range of 0.3-33 nM; all designs bound to T cells by FACS. The triple chain BCMA-FAB-CD3 ScFv-Fc designs had the highest Kd of binding with CHO-BCMA cells (Kd=0.3 nM) and with multiple myeloma MM1S, and H929 cells (0.1 and 0.3 nM, respectively). All antibodies with T cells specifically killed CHO-BCMA and multiple myeloma cells in a dose-dependent manner but not CHO or K562 cells, measured by RTCA assay. The bivalent BCMA-CD3 CrossMAB and triple chain BCMA FAB CD3scFv-Fc antibodies with T cells secreted IFN-gamma with EC50 =0.01-0.02 nM. In addition, the BCMA bispecific antibodies had high in vivo efficacy using a MM1S xenograft NSG mouse model. Significance: This data demonstrates high efficacy of novel hBCMA-CD3 antibodies with multiple myeloma cells and provides a basis for future pre-clinical and clinical development. Citation Format: Yanwei Huang, John Sienkiewicz, Jinying Sun, Liselle Guiang, Feng Li, Liming Yang, Lijun Wu, Vita M. Golubovskaya. Novel bispecific humanized BCMA-CD3 antibodies specifically target multiple myeloma cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2889.
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