Chimeric antigen receptor-modified T cells (CAR T cells) directed against CD19 have shown promise as a novel therapy for hematological malignancies; complete remission (CR) has been achieved in as many as 70–90% of cases of relapsed/refractory acute lymphoblastic leukemia (R/R B-ALL) [1–5]. Here, CD19 is linked to acute lymphoblastic leukemia.