Many clinical data concur in demonstrating a clinical benefit for patients affected by B cell lymphoid malignancies treated with CAR.CD19 T cells [40, 41], but while CD19 is well known to be a good target for CAR T cell-based therapy, in AML, the application of single-targeting approaches remains difficult, as none of the known antigens are exclusively expressed on AML cells, raising the concern of potential severe on-target off-tumour toxicity [12, 42]. The gene discussed is CD19; the disease is acute myeloid leukemia.