BACH2 dosage establishes the hierarchy of stemness and fine-tunes antitumor immunity in CAR T cells

Stem-like T cells promote the efficacy of immunotherapy and are heterogeneous in stemness, with long-term (LT) stem-like T cells at the apex of this hierarchy. How the stemness hierarchy is regulated in chimeric antigen receptor (CAR) T cells and how it affects antitumor function are unclear. Here we show that BACH2 dose-dependently regulates LT stem-like differentiation and antitumor immunity of CAR T cells. LT stem-like CAR T cells that appear before infusion and re-emerge after tumor clearance have superior antitumor immunity and the greatest BACH2 expression. BACH2 promotes the antitumor response of CAR T cells and the LT stem-like transcriptional program. Temporal and quantitative induction of BACH2 expression in CAR T cells during manufacturing using chemical switches fine-tunes the degree of stemness and imprints greater control of solid tumors. Together, these data show that BACH2 dosage defines stemness hierarchy in CAR T cells and can be temporally and tunably controlled to optimize differentiation and antitumor efficacy.