Abstract 54: Engineering Chimeric Antigen Receptor (CAR) T Cells Using Autoantigen Binding Domains for Treatment of B Cell Malignancies with Increased Specificity

Abstract Introduction: Chronic inflammation often leads to cancer, and many autoimmune diseases lead to a significantly increased risk of developing cancer. Though many autoimmune diseases, like Graves’ Disease (GD), don’t have treatments that address this risk. Chimeric antigen receptor (CAR) T cells are an effective treatment for hematological cancers by eliminating all B cells, but a more targeted form of CAR T cells could eliminate specific B cell populations in B cell malignancies, including GD. Methods: To allow our CAR T cells to target specific B cell populations that cause GD, we engineered chimeric autoantigen receptors (CAAR) with epitopes of thyroid stimulating hormone receptor (TSHR) as the binding domain. This acts as bait for the anti-TSHR B cells. Jurkat T cells were lentivirally transduced with these CAAR plasmids. Anti-TSHR B cell lines were engineered by transducing Nalm6 cells with lentivirus for anti-TSHR B cell receptors. Cytotoxicity assays were performed on primary human TSHR CAAR T cells incubated with the anti-TSHR B cell lines. Cytokine production, proliferation, and cytotoxicity assays were performed on these coincubated cells to determine the efficacy of our TSHR CAAR T cells. Results: Two of the three Jurkat TSHR CAAR T cells showed significant binding to anti-TSHR antibodies (TRAbs). They also showed significant activation, measured by CD69 expression, when incubated with plate bound TRAbs, but not soluble TRAbs. The B cell lines were validated by binding to TSHR. The primary TSHR CAAR T cells showed significantly increased proliferation and production of TNF, IFN-y, and IL-2, when compared with controls. The TSHR CAAR T cells also had significant cytotoxic action against the anti-TSHR B cell lines, but not Nalm6 B cells. The cytotoxic function was comparable to our CD19 CAR T cell with the same activation domains, though it demonstrated specificity to only anti-TSHR B cells. Conclusion: TSHR CAAR T cells are a potentially curative treatment for GD that will stop chronic inflammation and could reduce GD patient’s risk of developing thyroid cancer. This is also an important development in CAR T cell therapies that allows for specific targeting of certain B cell populations. Citation Format: Abiagil Cheever, Hunter Lindsay, MacKenzie Hansen, Chloe Kang, K. Scott Weber, Kim O'Neill. Engineering chimeric antigen receptor (CAR) T cells using autoantigen binding domains for treatment of B cell malignancies with increased specificity [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 54.