CD19 and acute lymphoblastic leukemia: In contrast to CD19-targeting CAR T cells in acute lymphoblastic leukemia (ALL) and diffuse large B-cell lymphoma (DLBCL), which require long-term persistence for durable remissions [1, 2], we observed that CAR T cells were undetectable in PB 100 days after infusion in most patients, even in those with sustained response.