Translation of Autophagy-Reprogrammed B7-H3 CAR T
| Despite major advances in pediatric oncology, outcomes for children with relapsed or refractory sarcomas remain dismal, with survival rates below 25 percent and limited therapeutic options. Immunotherapy with chimeric antigen receptor (CAR) T cells has transformed the treatment of leukemia and lymphoma, but its success in solid tumors has been modest. The main barriers are the poor persistence of CAR T cells, their metabolic exhaustion and the highly immunosuppressive tumor microenvironment (TME) that characterizes most sarcomas. Our research focuses on improving the metabolic fitness and longevity of CAR T cells through a process known as autophagy, a natural mechanism that allows cells to recycle energy and maintain homeostasis under stress. We recently demonstrated that the manufacturing process of CAR T cells profoundly suppresses autophagy, impairing their survival and antitumor activity. Using gene engineering, we successfully restored this pathway by reintroducing the protein Beclin1, which reactivates autophagy. This intervention markedly improved CAR T cell persistence, mitochondrial function and tumor-killing capacity in preclinical models, without toxicity. These findings were obtained through our previous Sarcoma Foundation of America funded project (SFA-1070868). In parallel, we developed a CAR targeting B7-H3, a molecule abundantly expressed across multiple pediatric sarcoma subtypes, including osteosarcoma, Ewing sarcoma, synovial sarcoma and rhabdomyosarcoma. B7-H3 is also found on immunosuppressive cells within the TME, such as M2 macrophages and myeloid-derived suppressor cells, suggesting that its targeting could simultaneously attack tumor cells and remodel the immune environment. Our preclinical studies show that the new B7-H3.CAR performs as effectively as our clinically validated GD2.CAR platform, while offering broader coverage across sarcoma types. This proposal seeks to complete the translational development of autophagy-reprogrammed B7-H3.CAR T cells, advancing them toward clinical evaluation. The project will (1) perform in vivo safety and biodistribution studies; (2) establish a stable GMP-grade viral producer line to ensure reproducible manufacturing; and (3) define GMP release criteria and B7-H3 expression thresholds for patient selection in an academic phase I clinical trial. The proposed work integrates strong mechanistic innovation with a direct path to patient benefit. By combining metabolic reprogramming through autophagy restoration with a broadly expressed and immunomodulatory target, this strategy has the potential to overcome the major limitations of CAR T therapy in solid tumors. Successful completion of the project will lay the foundation for a first-in-human trial in children with relapsed or refractory B7-H3+ sarcomas, ultimately offering a novel and durable immunotherapeutic option where few alternatives exist. |