AG-221 is an orally available inhibitor of mutant IDH2-R140 and IDH2-R172 (Yen et al., 2017), and is currently undergoing phase I/II clinical trials as a single agent for the treatment of AML and solid tumors (e.g., glioma and angioimmunoblastic T-cell lymphoma; NCT01915498 and NCT02273739, respectively). The gene discussed is IDH2; the disease is glioma.