T lymphocytes expressing the switchable chimeric Fc receptor CD64 exhibit augmented persistence and antitumor activity

Abstract

Chimeric antigen receptor (CAR) Tcell therapy lacks persistent efficacy with "on-target, off-tumor" toxicities for treating solid tumors. Thus, an antibody-guided switchable CAR vector, the chimeric Fc receptor CD64 (CFR64), composed of a CD64 extracellular domain, is designed. Tcells expressing CFR64 exert more robust cytotoxicity against cancer cells than CFR Tcells with high-affinity CD16 variant (CD16v) or CD32A as their extracellular domains. CFR64 Tcells also exhibit better long-term cytotoxicity and resistance to Tcell exhaustion compared with conventional CAR Tcells. With trastuzumab, the immunological synapse (IS) established by CFR64 is more stable with lower intensity induction of downstream signaling than anti-HER2 CAR Tcells. Moreover, CFR64 Tcells exhibit fused mitochondria in response to stimulation, while CARH2 Tcells contain predominantly punctate mitochondria. These results show that CFR64 Tcells may serve as a controllable engineered Tcell therapy with prolonged persistence and long-term antitumor activity.