CD19 and acute lymphoblastic leukemia: On August 30, 2017, the US Food and Drug Administration (FDA) approved the use of tisagenlecleucel (CTL-019; Kymriah®, Novartis, Basel, Switzerland), a CD19-directed chimeric antigen receptor (CAR) T cell, for adoptive cell therapy (ACT) to treat patients with relapsed/refractory B-cell acute lymphoblastic leukemia (r/r B-ALL) (1–3).