CD19 and cancer: Colorectal cancer (CRC) is the second leading cause of cancer death worldwide, with approximately half of patients ultimately developing advanced, incurable CRC, and limited advancements in treatment outcomes.1,2,3 Chimeric antigen receptor (CAR) T-cell therapy (CART) has conferred marked efficacy in hematologic cancers but not in solid cancers.4 One contributing factor is the robust expansion of CD19-targeting CAR T cells compared with those targeting solid tumor antigens.