Watanabe, N.; Leong, L.; Narula, M.; Englisch, J.; Ou, C.; Mamonkin, M.

Chimeric antigen receptor (CAR)-modified V{delta}2 T cells are an attractive therapeutic cell platform for cancer immunotherapy. However, their clinical efficacy is limited by short in vivo persistence due to insufficient cytokine support and high susceptibility to activation-induced cell death (AICD). Through comparison of membrane-bound (mb) cytokines, we identified mbIL-18 to support superior anti-tumor activity of CAR-V{delta}2 T cells in vitro and in vivo. To reduce constitutive surface exposure of IL-18 and enable antigen-driven signal 3, we fused MyD88 - the key IL-18R signaling mediator - to an extracellular domain of Fas (Fas88). Antigen stimulation-induced FasL engagement of Fas88 triggered IL-18 signaling while simultaneously protecting V{delta}2 T cells from AICD. Fas88-armed human CAR-V{delta}2 T cells produced superior yet stimulation-dependent in vivo expansion and functional persistence in xenograft models of hematologic and solid malignancies. Together, these findings highlight the importance of IL-18 signaling and AICD resistance for CAR-V{delta}2 T cell activity, enabling a single-transgene modification to limit inflammatory risk and facilitate clinical translation.