BACH2 regulates T cell lineage states to enhance CAR T cell function [ATAC-seq]

Nearly all chimeric antigen receptors (CARs) signal in the absence of antigen, referred to as “tonic signaling”. Tonic signaling of CARs containing the CD28 costimulatory domain has been shown to driveT cell exhaustion; in contrast, we found that tonic signaling of 41BB-containing CARs enhances T cell function. Using a panel of CARs targeting CD22, we identified that tonic 41BB signaling activatesBACH2, a transcriptional regulator that directs stem and memory programs. Overexpression of BACH2 prevented tonic CD28-driven exhaustion but locked CAR T cells in quiescent states. To overcome this, we linked BACH2 to a degradation domain and found that tuning BACH2 expression enhanced long-term efficacy of exhaustion-prone CAR T cells targeting liquid and solid tumors. Through interrogation of CAR products, we also found an association between BACH2 activity and clinical outcomes in patients with leukemia. These data identify a central role for BACH2 in regulating CAR T cell efficacy.