Feucht and Sun et al. generated 1928ζ CAR T cells in which two of three CD3ζ immunoreceptor tyrosine based-activation motifs (ITAMs) were impeded, leading to 1XX, X2X, and XX3 CAR T cells. Functional studies and transcriptome analysis showed that compared to the full construct, 1XX (targeted to the TRAC locus) showed enhanced antitumor efficacy (both short- and long-term), an increase in central memory cells, a decrease in terminal effector or exhausted cells, long-term cytotoxicity and polyfunctionality, and enhanced persistence. Due to its more distal ITAM, XX3 CAR T cells were more naive/memory-like and had limited effector function.
Chimeric antigen receptors (CARs) are synthetic receptors that target and reprogram T cells to acquire augmented antitumor properties(1). CD19-specific CARs that comprise CD28 and CD3zeta signaling motifs(2) have induced remarkable responses in patients with refractory leukemia(3-5) and lymphoma(6) and were recently approved by the US Food and Drug Administration(7). These CARs program highly performing effector functions that mediate potent tumor elimination(4,8) despite the limited persistence they confer on T cells(3-6,8). Extending their functional persistence without compromising their potency should improve current CAR therapies. Strong T cell activation drives exhaustion(9,10), which may be accentuated by the redundancy of CD28 and CD3zeta signaling(11,12) as well as the spatiotemporal constraints imparted by the structure of second-generation CARs(2). Thus, we hypothesized that calibrating the activation potential of CD28-based CARs would differentially reprogram T cell function and differentiation. Here, we show that CARs encoding a single immunoreceptor tyrosine-based activation motif direct T cells to different fates by balancing effector and memory programs, thereby yielding CAR designs with enhanced therapeutic profiles.