Although the 5-year survival rate for leukemia has been improved from 14% in ~1960 to higher than 60% in ~2010, the overall survival of the more malignant subtypes such as acute myeloid leukemia (AML; overall survival rate < 25%) (1, 2) and acute lymphoblastic leukemia [ALL; particularly the KMT2A (MLL)–rearranged subtype; overall survival rate < 20% in adult patients] (3) remain stunningly low. The gene discussed is KMT2A; the disease is acute lymphoblastic leukemia.