Gu, Y.; Choi, J.; Mutha, D.; Wu, C.; Ganem, N. J.; Grinstaff, M.; Wong, W.

Chimeric antigen receptor T (CAR-T) cell therapy is transforming the treatment landscape of hematological malignancies. However, manufacturing with integrating viral vectors is costly, slow, and carries risks including insertional mutagenesis, pro-longed B cell aplasia, and other long-term toxicities. Expression of CAR with mRNA can reduce cost, manufacturing timelines, and improve safety. However, the short-lived expression necessitates frequent repeat dosing. Here, we describe a modified self-amplifying RNA (saRNA) platform for engineering CAR T cells with prolonged CAR expression and enhanced durability of tumor control relative to mRNA CAR T cells. In an acute lymphoblastic leukemia (ALL) xenograft model, saRNA CAR T cells achieve superior tumor suppression and prolong survival. Further, a single-strand modified saRNA supports the co-expression of multiple proteins, enabling the construction of advanced CAR systems, such as OR- and AND-gated logic CAR T cells. Together, these results highlight saRNA as a powerful and versatile platform for CAR T cell engi-neering with favorable safety, efficacy, and accessibility.