Low-Strength Type I Interferon Signaling Promotes CAR T-cell Treatment Efficacy.

CD19-directed chimeric antigen receptor (CAR) T-cell therapy has significantly advanced the treatment landscape for relapsed/refractory diffuse large B-cell lymphoma (r/r DLBCL). However, up to 60% of patients do not achieve a complete response. To uncover determinants of therapeutic efficacy, we analyzed the infusion products (IPs) of eight r/r DLBCL patients with distinct clinical responses to axicabtagene ciloleucel using single-cell transcriptomics. Compared with patients who exhibited progressive disease, IPs of complete responders demonstrated enriched signatures of type I interferon (IFN-I) signaling. Based on these findings, we developed a strategy to improve CD19-directed CAR T-cell treatment efficacy by incorporating IFN-I as an enhancer during the ex vivo manufacturing process, with IFN-I removal before CAR T-cell infusion to avoid in vivo toxicities. For both CD28- and 4-1BB-costimulated second-generation CARs, we found that low-strength IFN-I signaling enhanced CAR T-cell cytotoxicity and treatment efficacy against B-cell lymphoma and leukemia. Our low-strength IFN-I-enhanced CAR T-cell ex vivo manufacturing approach leverages an existing FDA-approved pharmacologic agent, circumvents in vivo interferon-associated toxicities, and remains fully compatible with current CAR constructs and manufacturing workflows. Together, our results establish IFN-I as a potent and costimulation-independent enhancer of CAR T-cell efficacy and provide a translationally feasible approach to enhance CAR T-cell therapies.