TET2 regulates early and late transitions in exhausted CD8 ⁺ T cell differentiation and limits CAR T cell function

CD8 ⁺ T cell exhaustion hampers control of cancer and chronic infections and limits chimeric antigen receptor (CAR) T cell efficacy. Targeting TET2 in CAR T cells provides therapeutic benefit; however, TET2’s role in exhausted T cell (T _EX ) development is unclear. In chronic lymphocytic choriomeningitis virus (LCMV) infection, TET2 drove conversion from stem cell–like T _EX progenitors toward terminally differentiated and effector (T _EFF )–like T _EX . TET2 also enforced a terminally differentiated state in the early bifurcation between T _EFF and T _EX , indicating broad roles for TET2 in acquisition of effector biology. To exploit the therapeutic potential of TET2, we developed clinically actionable TET2- targeted CAR T cells by disrupting TET2 via knock-in of a safety switch alongside CAR knock-in at the TRAC locus. TET2 -targeted CAR T cells exhibited restrained terminal exhaustion in vitro and enhanced antitumor responses in vivo. Thus, TET2 regulates fate transitions in T _EX differentiation and can be targeted with a safety mechanism in CAR T cells for improved tumor control.