Rational protein engineering to enhance MHC-independent T cell receptors

Abstract Chimeric antigen receptor (CAR)-based therapies have pioneered synthetic cellular immunity against cancer, however remain limited in their scope and long-term efficacy. Emerging data suggest that dysregulated CAR-driven T cell activation causes T cell dysfunction and therapeutic failure. To re-engage the endogenous T cell response, we designed hybrid MHC-independent T cell receptors (miTCRs) by linking antibody variable domains to TCR constant domains. While functional, we observed stark differences in miTCR-driven T cell function that were dependent on receptor orientation. Using predictive structural modeling, we observed significant biochemical conflicts at the hybrid variable-constant domain interface. To overcome this, we performed iterative sequence modifications and structural modeling to design a panel of miTCR variants predicted to have improved interface stability. Functional screening nominated a variant with superior efficacy to all other miTCRs as well as a standard CAR against high burdens of leukemia. Statement of Significance Improving the durability of engineered T cell immunotherapies is critical to enhancing efficacy. We used structure-informed design to evolve MHC-independent T cell receptors that drive improved tumor control. This work underscores the central role of synthetic receptor structure on T cell function and provides a framework for improved receptor engineering.