Ibrutinib and PD-1 blockade potentiate mesothelin-targeting CAR-T cell therapy in preclinical models of pancreatic cancer

Abstract Purpose: Pancreatic ductal adenocarcinoma (PDAC) remains refractory to chimeric antigen receptor (CAR) T cell therapies due to its immunosuppressive microenvironment and a dense extracellular matrix deposited by cancer-associated fibroblasts (CAFs), which impair CAR-T cell infiltration. To address these barriers, we previously developed a dual-targeting CAR-TEAM platform in which mesothelin-specific CAR-T cells secrete a FAP-targeting T cell engager antibody molecule (TEAM) to simultaneously kill tumor cells and CAFs. Here, we leveraged mesothelin-targeting CAR-T cells and tested rational drug combinations and optimal delivery strategies to enhance therapeutic efficacy and guide potential combinations that could be incorporated into a clinical study. Experimental design: Tumor mesothelin shedding by proteases and CAR-T cell dysfunction remain key obstacles to CAR-T cell efficacy. Using pre-clinical PDAC models, we tested mesothelin-targeting CAR-T cells in combination with agents that increase tumor mesothelin expression, promote T cell polarization and persistence, and support T cell function. Furthermore, we compared intravenous versus intraperitoneal delivery routes to treat peritoneal metastases. Results: We demonstrated that ibrutinib enhanced CAR-T cell expansion, Th1 skewing, and anti-tumor activity in PDAC. PD-1 blockade synergistically improved CAR-T cell anti-tumor function in a patient-derived PDAC xenograft and intraperitoneal delivery proved superior against peritoneal disease. Conversely, while an ADAM10/17 inhibitor prevented mesothelin shedding and improved tumor killing in vitro, it did not enhance efficacy in vivo. Conclusion: These findings identify clinically actionable strategies to optimize CAR-T cell therapy against PDAC. A phase-I clinical trial testing meso-FAP CAR-TEAM T cells, alone or in combination with ibrutinib or PD-1 blockade is in development.