A third case described a similar switch from an IDH1 to IDH2 mutation in cholangiocarcinoma and a fourth case described a switch from IDH2R140Q-mutant AML to IDHR132C after Enasidenib treatment that was then responsive to second-line treatment with pan-inhibitor, AG-881 (99). The gene discussed is IDH2; the disease is cholangiocarcinoma.