Chimeric antigen receptor (CAR) T cells targeting CD19 were granted U.S. Food and Drug Administration (FDA) approval in 2017 after demonstrating nearly unprecedented response rates in heavily pretreated patients suffering from acute lymphoblastic leukemia (ALL) or diffuse large B cell lymphoma (DLBCL) [67,68,69,70]. The gene discussed is CD19; the disease is acute lymphoblastic leukemia.