Abstract A029: Overcoming heterogeneous glioblastoma with armored CAR-T cell therapy. Authors: Clubb, J. D., Shih, R., Gao, T., Shafer, A, Vajragiri, S., Talluri, S., Bouren, A., Brown, C. E., Okada, H., Nathanson, D., Chen, Y

Abstract Glioblastoma is the most common primary central nervous system malignancy and has a median overall survival of only 8 months after diagnosis [1]. In recent years, chimeric-antigen receptor (CAR)-T cell therapy has shown unprecedented efficacy against advanced B-cell malignancies. However, the application of CAR-T cell therapy to solid tumors, including GBM, has been largely unsuccessful [2]. In glioblastoma, two key challenges curtail CAR-T cell efficacy: tumor heterogeneity, and an immunosuppressive tumor microenvironment [2]. To address solid-tumor challenges, one approach is to equip CAR-T cells with one or more immunomodulatory proteins, a term commonly referred to as “armoring” the CAR-T cells. In this work, we have engineered CAR-T cells to secrete combinations of armor proteins, such that the CAR-T cells can not only directly attack tumor cells, but also remodel the tumor milieu to inhibit immunosuppression and engage endogenous immunity as a powerful complementary force. Through an in vivo screen of potentially synergistic armor combinations, we have found that CAR-T cells engineered to secrete both IL-12 and the decoy-resistant form of IL-18 (CAR-12.DR18 T cells) are remarkably efficacious against syngeneic, orthotopic, antigen-heterogenous glioblastoma tumors. However, this combination of potent cytokines also results in transient but significant toxicity. Upon interrogating various toxicity reduction strategies, we found that pooling CAR-12.DR18 T cells with CAR-T cells that secrete a novel anti-VEGF scFv ameliorates toxicity while maintaining robust efficacy. References 1. Q. T. Ostrom et al., CBTRUS Statistical Report: Primary Brain and Other Central Nervous System Tumors Diagnosed in the United States in 2016-2020. Neuro Oncol 25, iv1-iv99 (2023). 2. R. C. Sterner, R. M. Sterner, CAR-T cell therapy: current limitations and potential strategies. Blood Cancer J 11, 69 (2021). Citation Format: Justin D Clubb, Ryan Shih, Torahito Gao, Amanda Shafer, Shreya Vajragiri, Sohan Talluri, Amber Bouren, Christine E Brown, Hideho Okada, David Nathanson, Yvonne Chen. Overcoming heterogeneous glioblastoma with armored CAR-T cell therapy. Authors: Clubb, J. D., Shih, R., Gao, T., Shafer, A, Vajragiri, S., Talluri, S., Bouren, A., Brown, C. E., Okada, H., Nathanson, D., Chen, Y [abstract]. In: Proceedings of the AACR IO Conference: Discovery and Innovation in Cancer Immunology: Revolutionizing Treatment through Immunotherapy; 2025 Feb 23-26; Los Angeles, CA. Philadelphia (PA): AACR; Cancer Immunol Res 2025;13(2 Suppl):Abstract nr A029.