Abstract 7337: Development of novel anti BCMA as a low cost adoptive cellular therapy candidate in multiple myeloma

Abstract Background: Multiple myeloma (MM) involves the proliferation of malignant plasma cells (PCs) in the bone marrow (BM), leading to excessive monoclonal immunoglobulins in patients' blood and urine. The use of monoclonal antibodies (MoAbs) as immunotherapies in MM treatment has significantly improved outcomes. However, MM remains incurable for most patients due to the emergence and evolution of drug-resistant clones. BCMA (B Cell Maturation Antigen), overexpressed in MM, is being explored as a target for antibody-based and cellular therapies. Method: BCMA expression in MM patients was quantified via RQ-PCR, and soluble BCMA levels were measured using ELISA to analyze BCMA dynamics in this cohort. The extracellular domain (ECD) of BCMA was cloned, sequenced, and expressed in the Expi293 system, with characterization confirmed through SDS-PAGE. To generate anti-BCMA ECD antibodies, mice were immunized with the purified ECD protein , leading to the development of hybridoma cells. These were purified and validated through western blotting and other assays to identify top-binding clones. The highest-affinity clone was purified using a protein A IgG purification kit. Molecular docking and dynamic simulations were then conducted to determine the BCMA ECD epitope/paratope targeted by our antibody. Results: We analyzed BCMA expression in multiple myeloma (MM) patients and observed elevated mRNA levels and increased serum BCMA, both linked to poor treatment outcomes. BCMA was validated as a promising therapeutic target, and the BCMA ECD protein was successfully expressed in a eukaryotic system, facilitating hybridoma generation. From this, 20 unique clones were developed and screened via ELISA for optimal binding to the BCMA ECD protein, with the clone 9C4 emerging as the lead candidate. Molecular docking revealed four novel epitopes (S, Q, N, E) distinct from previously identified ones. Our antibody demonstrated superior binding, interacting with 23 BCMA residues compared to 12-16 residues targeted by existing antibodies. The ScFv sequence of the 9C4 clone was incorporated into a second-generation CAR construct. This novel Anti-BCMA CAR was successfully expressed on T cells, enabling the development of CAR-T cells for advanced therapeutic applications. Conclusion: Our findings confirm BCMA as a key target in multiple myeloma, demonstrated by the successful development of the high-affinity 9C4 antibody. Incorporating the 9C4 ScFv into a second-generation CAR construct establishes a foundation for developing a novel academic Anti-BCMA CAR-T cell therapy for multiple myeloma. Citation Format: Ashna Gupta, Gunjan Dagar, Ravi Chauhan, Kalpana Luthra, Mayank Singh. Development of novel anti BCMA as a low cost adoptive cellular therapy candidate in multiple myeloma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 7337.