Regnase-1 suppresses TCF-1+ precursor exhausted T-cell formation to limit CAR-T-cell responses against ALL

Chimeric antigen receptor (CAR)-T-cell therapeutic efficacy is associated with long-term T-cell persistence and acquisition of memory. Memory-subset formation requires T-cell factor 1 (TCF-1), a master transcription factor for which few regulators have been identified. Here, we demonstrate using an immune-competent mousemodel of B-cell acute lymphoblastic leukemia (ALL; B-ALL) that Regnase-1 deficiency promotes TCF-1 expression to enhance CAR-T-cell expansion and memory-like cell formation. This leads to improved CAR-T-mediated tumor clearance, sustained remissions, and protection against secondary tumor challenge. Phenotypic, transcriptional, and epigenetic profiling identified increased tumor-dependent programming of Regnase-1-deficient CAR-T cells into TCF-1(+) precursor exhausted T cells (T-PEX) characterized by upregulation of both memory and exhaustion markers. Regnase-1 directly targets Tcf7 messenger RNA (mRNA); its deficiency augments TCF-1 expression leading to the formation of TPEX that support long-term CAR-T-cell persistence and function. Regnase-1 deficiency also reduces exhaustion and enhances the activity of TCF-1(-) CAR-T cells. We further validate these findings in human CAR-T cells, where Regnase-1 deficiency mediates enhanced tumor clearance in a xenograft B-ALL model. This is associated with increased persistence and expansion of a TCF-1(+) CAR-T-cell population. Our findings demonstrate the pivotal roles of TPEX, Regnase-1, and TCF-1 in mediating CAR-T-cell persistence and recall responses, and identify Regnase-1 as a modulator of human CAR-T-cell longevity and potency that may be manipulated for improved therapeutic efficacy.