The inhibitor of mutant IDH1 ivosidenib (40, 130) and mutant IDH2 enasidenib (159, 160) exhibited positive responses in patients with relapsed or refractory gliomas, intrahepatic cholangiocarcinomas, and chondrosarcomas (48, 130) in phase I/II clinical trials. The gene discussed is IDH2; the disease is central nervous system cancer.