Mutations in the TFs ERG and ETV6 and the histone demethylase complex subunit ARID5B, previously linked to poor treatment outcomes in ALL [46, 78], were prevalent in EOI slow responders, while mutations in IKZF2 and the histone H3K79 methyltransferase DOT1L were enriched in fast responders. The gene discussed is IKZF2; the disease is acute lymphoblastic leukemia.