Anti-inflammatory drugs remodel the tumor immune environment to enhance immune checkpoint blockade efficacy [SZ9]

Identifying strategies to improve the efficacy of immune checkpoint blockade (ICB) remains a major clinical need. Here, we show that therapeutically targeting the COX-2/PGE2/EP2-4 pathway with widely used non-steroidal and steroidal anti-inflammatory drugs synergized with ICB in mouse cancer models. We exploited a bilateral surgery model to harness the heterogeneity in treatment outcome and distinguish responders from non-responders shortly following treatment. Deep cellular and molecular tumor profiling revealed acute IFN-γ-driven tumor remodeling in responder mice that was also associated with patient benefit to ICB. Crucially, monotherapy with COX-2 inhibitors or EP2-4 PGE2 receptor antagonists rapidly induced this response program and, in combination with ICB, increased the intratumoral accumulation of T cells with enhanced effector function. Inhibition of the COX-2/PGE2 pathway in patient-derived tumor fragments from multiple patients and cancer types revealed a similar shift in the tumor inflammatory environment to favor T cell activation. Our findings establish the COX-2/PGE2/EP2-4 axis as an independent immune checkpoint and a readily translatable strategy to switch the tumor inflammatory profile from cold to hot and enhance the efficacy of immunotherapy. Bulk RNA profiling of CT26 colorectal tumours treated with vehicle, celecoxib (CXB), anti-PD-1 or anti-PD-1 plus celecoxib for 7 days.