Ivosidenib, the first-in-class IDH 1 inhibitor, was evaluated in a multicenter, open-label, phase 1 study in 66 patients with recurrent IDH1-mutant gliomas, 32 of whom had grade 2 gliomas, 18 had grade 3 gliomas, and 12 had grade 4 gliomas.145 Only one partial response was observed, in a patient with grade 3 a non-enhancing tumor. The gene discussed is IDH1; the disease is central nervous system cancer.