We discovered that azacitidine and decitabine were highly effective in our infant KMT2A-rearranged preclinical models, supporting the rationale for investigation of azacitidine in the Children’s Oncology Group (COG) AALL15P1 pilot study for infants with KMT2A-rearranged ALL (NCT02828358). The gene discussed is KMT2A; the disease is acute lymphoblastic leukemia.