CAR-adapted PIK3CD base editing enhances T cell anti-tumor potency.

Insufficient functional T cell persistence impedes therapeutic success of chimeric antigen receptor (CAR) therapies. Here we performed a CAR-adapted base-editing screen of PIK3CD, a key regulator of T cell function, metabolism and fate. We identified point mutations that beneficially modulate CAR T cell profiles in 4-1BBz and 28z CAR T cells, respectively. We found that point mutations with differing effects on phosphatidylinositol-3-kinase delta (PI3Kδ) signaling activity were advantageous in distinct CAR contexts: The PI3Kδ-activating substitution E81K enhanced proliferation, metabolic fitness and effector function of 4-1BBz CARs, promoting long-term functional persistence and enhanced therapeutic efficacy in vivo. Conversely, the PI3Kδ-attenuating substitution L32P improved T cell memory formation and functionality of 28z CAR T cells. Together, our approach of rational optimization of activation-dependent signaling through targeted allelic reprogramming (ROADSTAR) illustrates the importance of CAR design-specific fine-tuning of intrinsic T cell signaling and demonstrates the potential of base editing for next-generation cellular therapies.