The first published phase I trial of CD19-4-1BB-CD3ζ CAR-T cells for B-ALL at Children’s Hospital of Philadelphia (CHOP) (NCT01626495 and NCT01029366) showed that 3 of 27 CR patients (11%) relapsed due to loss of CD19 in leukemia cells [111]. The gene discussed is CD19; the disease is leukemia.