We conducted a single-arm, phase 2 trial evaluating the efficacy of abemaciclib in patients with recurrent oligodendroglioma, isocitrate dehydrogenase (IDH)-mutant and 1p/19q-codeleted, WHO grade 3, following prior RT and ≥1 line of alkylating chemotherapy. The gene discussed is IDH2; the disease is oligodendroglioma.