Despite outstanding the initial responses observed with CD19 CAR T cells for younger patients with B-cell acute lymphoblastic leukemia, historical data show more than half of patients experience disease relapse within 4 to 5 years, so current research is focused on whether HSCT after CAR T-cell therapy may have a positive effect on treatment durability, and indeed, CD19-directed CAR T-cell therapy before HSCT was shown to lead to more durable remissions [14], with important implications for future practice guidelines. This evidence concerns the gene CD19 and B-cell acute lymphoblastic leukemia.