IDH2 and acute myeloid leukemia: AG-221 (Enasidenib), a selective inhibitor of mutant IDH2, has demonstrated activity in pre-clinical models of acute myeloid leukemia (AML) [40,41,42] and is currently being assessed in multiple phases I/II clinical trials in subjects with advanced solid tumors, including iCCA, who harbor an IDH2 mutation (NCT02273739).