CD19 and acute lymphoblastic leukemia: Tisagenlecleucel, developed at the University of Pennsylvania, is composed of an extracellular CD19 targeting scFv (FMC63) fused to CD137 (4-1BB) and CD3z intracellular signaling domains and has been approved for the treatment of relapse/refractory (r/r) B cell acute lymphoblastic leukemia (B-ALL) and diffuse large B-cell lymphoma (DLBCL) (10–12).