CXCL13 Expression Promotes CAR T Cell Antitumor Activity and Potentiates Response to PD‐1 Blockade

Abstract Immune checkpoint blockade (ICB) and chimeric antigen receptor (CAR) T cell therapies have revolutionized cancer immunotherapy, offering significant benefits across various cancers. However, challenges remain, particularly in solid tumors where immunosuppressive tumor microenvironments and T cell exhaustion limit effectiveness. Combining ICB with CAR T cell therapy has shown potential but requires further optimization for effective synergy. Here, the bioinformatic analysis identified that CXCL13 expression is highly elevated in T cells from patients who respond to ICB, indicating its possible role in enhancing T cell antitumor responses. Mouse CAR T cells are engineered to overexpress CXCL13 and observed that these cells displayed reduced exhaustion, increased central memory phenotype, and improved mitochondrial function and proliferation in an AKT‐mTOR dependent manner. CXCL13‐overexpressing CAR T cells show significantly increased antitumor activity in vivo, particularly when combined with PD‐1 inhibition, promoting the expansion and persistence of early exhausted CD8 + CAR T cells. CXCL13 also conferred similar in vitro phenotypic enhancements in human CAR T cells as observed in murine cells. These results indicate that CXCL13 expression improves CAR T cell function and responsiveness to ICB, offering a promising and translationally relevant strategy to optimize CAR T cell therapy for solid tumors in clinical settings.