IMMU-13. Synergistic Integration of TCR and CAR T Cell Platforms for Enhanced Adoptive Immunotherapy in Brain Tumors

Abstract Background The effectiveness of T-cell-based immunotherapies, such as Chimeric Antigen Receptor (CAR) T cells and antigen-specific T Cell Receptor (TCR) T cells, remains limited in addressing aggressive solid tumors like high-grade gliomas (HGG). Each platform presents unique advantages in tackling challenges related to T cell activation, persistence, and exhaustion. Both B7H3, a pan-cancer antigen, and gp100, a transmembrane glycoprotein, are overexpressed in HGG, making them attractive targets for immunotherapy. In this study, we engineered dual-specific gp100-TCR and B7H3 CAR T cells, leveraging the strengths of both platforms to mitigate antigen escape, improve T cell persistence, and achieve synergistic cytotoxic effects. Objective To assess the cytotoxicity and persistence of dual-specific TCRgp100-B7H3 CAR T cells against HGG. Methods/Design T cells expressing the gp100 TCR were transduced with a B7H3 CAR to generate dual-specific TCRgp100-B7H3 CAR T cells. Efficacy and persistence were assessed against HGG cell lines using repeated stimulation and MTS cytotoxicity assays. Functional analysis included memory phenotyping and exhaustion marker evaluation (PD1, TIM3, and TIGIT) using FACS. Results Preliminary data indicate that TCR-CAR T cells exhibit significantly improved persistence, proliferation, and sequential killing capacity compared to standard CAR-only T cells. While initial cytotoxicity was comparable, TCR-CAR T cells maintained higher cytotoxicity at low effector-to-target ratios compared to CAR-only T cells during repeated stimulations. In contrast, CAR-only T cells showed diminished cytotoxicity over time. Early mechanistic studies revealed that TCR-CAR T cells underwent alterations in memory T cell phenotypes and epigenetic changes in exhaustion markers during repeated stimulation. Conclusion Our results demonstrate that combining TCR and CAR T cell platforms significantly enhances T cell activity and persistence in vitro. Future work will explore in vivo efficacy and underlying mechanisms. These findings highlight the potential of TCR and CAR integration to improve adoptive T cell efficacy against brain tumors.