Recently, patients with relapsed, refractory IDH1- and IDH2-mutant AML were demonstrated to have significant ORR and CR rates to the novel, selective IDH1- and IDH2-mutant inhibitors, ivosidenib and enasidenib, with evidence of differentiation of blasts, in a subset of patients leading to a differentiation syndrome akin to the previously described differentiation syndrome described in patients with APL treated with ATRA and ATO, in accordance with the predicted mechanisms of actions of these novel inhibitors (105, 166). The gene discussed is IDH1; the disease is acute promyelocytic leukemia.