Transient “rest” restores functionality in exhausted CAR-T cells via epigenetic remodeling

T cell exhaustion limits immune responses against cancer and is a major cause of resistance to chimeric antigen receptor (CAR) T cell therapeutics. Using xenograft models and an in vitro model wherein tonic CAR signaling induces hallmark features of exhaustion, we tested the impact of transient cessation of receptor signaling, or “rest”, on the development and maintenance of exhaustion. Induction of rest via enforced CAR protein downregulation using a drug-regulatable system or treatment with the multi-kinase inhibitor dasatinib resulted in acquisition of a memory-like phenotype, wholescale transcriptional and epigenetic reprogramming, and restored anti-tumor functionality in exhausted CAR-T cells. This work demonstrates that rest can enhance CAR-T cell efficacy by preventing or reversing exhaustion and challenges the notion that exhaustion is an epigenetically fixed state.