Herpes Virus Entry Mediator Costimulation Signaling Enhances CAR T-cell Efficacy Against Solid Tumors Through Metabolic Reprogramming

Costimulatory domains (CSD) of 4-1BB and CD28 are most widely used in chimeric antigen receptor (CAR)-engineered T cells. These CAR T cells have shown encouraging efficacy in the treatment of hematologic malignancies but have limited efficacy in solid tumors. The herpes virus entry mediator (HVEM) is a costimulatory molecule with a novel downstream signaling pathway. In response to target cells, CAR T cells with a HVEM CSD (HVEM-CAR T) displayed more robust cytokine release and cytotoxicity than 4-1BB-CAR T or CD28-CAR T in vitro. Furthermore, HVEM-CAR T showed superior therapeutic efficacy in several mouse tumor models. Mechanistically, the HVEM CSD endowed CAR T cells with attenuated exhaustion, improved function and persistence, and enhanced metabolic activities in tumor tissue compared with 4-1BB-based or CD28-based CAR T cells. These studies establish that the HVEM CSD has the potential to improve the therapeutic efficacy of CAR T cells against solid tumors.