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

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. Remarkably, point mutations with differing effects on PI3Kδ signaling activity were advantageous in distinct CAR contexts: The PI3Kδ-activating mutation E81K enhanced proliferation, metabolic fitness and effector function in 4-1BBz CARs, promoting long-term functional persistence and enhanced therapeutic efficacy in vivo. Conversely, the PI3Kδ-attenuating mutation L32P improved T cell memory formation and functionality in 28z CAR T cells. Together, our approach of Rational Optimization of Activation-dependent Signaling via Targeted Allelic Reprogramming (ROADSTAR) illustrates the importance of CAR design-specific fine-tuning of tailoring intrinsic T cell signaling and demonstrates the potential of base editing for next-generation cellular therapies.