CAR-T cells rest to get back in the race Chimeric antigen receptor (CAR)–T cells, which are engineered to target specific tumor antigens, are increasingly used as an immunotherapy. CAR-T cells have shown promising results in patients, particularly in hematologic cancers, but their anticancer activity can be limited by the onset of exhaustion and the loss of effectiveness. Weber et al. characterized the phenotypic and epigenomic changes associated with CAR-T cell exhaustion caused by continuous activity and the beneficial effects of transient rest periods (see the Perspective by Mamonkin and Brenner). The authors tested different approaches for providing these rest periods, such as using the drug dasatinib to temporarily suppress T cell activity, which helped to prevent exhaustion and improved antitumor activity in mouse models. Science , this issue p. eaba1786 ; see also p. 34