CD19 and acute lymphoblastic leukemia: Chimeric antigen receptor (CAR)-modified T-cells targeting CD19 have proven benefit for the treatment of multiply relapsed or refractory CD19+ acute lymphoblastic leukemia (ALL).1–9 Tisagenlecleucel, a CD19/4-1BB CAR T-cell product, received US Food and Drug Administration) approval in 2017 for pediatric and young adult patients with B-cell ALL that is refractory or in second or greater relapse.