Chimeric Antigen Receptors with a MyD88 and CD40 costimulatory endodomain endow T cells with superior antitumor activity

CAR T-cell therapy for solid tumors has shown limited efficacy in early phase clinical studies. The majority of CARs encode CD28 and/or 41BB costimulatory endodomains and we explored here if MyD88 and CD40 (MC) costimulatory endodomains in CARs improve their antitumor activity. We generated CD28-, 41BB-, and MC-CAR T-cells and demonstrate that MC-CAR T-cells have greater proliferative capacity and antitumor activity in repeat stimulation assays and in tumor models in vivo. Transcriptomic analysis revealed that MC-CAR T-cells expressed higher levels of MYB and FOXM1, key cell cycle regulators, and are activated at base line. After stimulation, MC-CAR T-cells remain in a less differentiated state than CD28- and 41BB-CAR T-cells as judged by low levels of TBET and BLIMP1 expression, and lower cytolytic activity in comparison to CD28- and 41BB-CAR T-cells. Thus, including MyD88 and CD40 signaling domains in CARs may improve current CAR T-cell therapy approaches for solid tumors. Overall design: Examination of CD4+ and CD8+ unstimulated and stimulated 4H5D-, CD28-, 41BB- and MC-CAR T cell costimulatory endodomains