CAR T cell therapies targeting CD19 have shown significant efficacy in treating patients with relapsed or refractory (r/r) B cell malignancies, with clinical trials of CD19 CAR T cells showing complete remission rates of 70–90% in B cell acute lymphoblastic leukemia (B-ALL) [1–3] and 40–58% in Non-Hodgkin’s Lymphoma (NHL) [4]. Here, CD19 is linked to B-cell acute lymphoblastic leukemia.