To evaluate for an efficacy signal in the treatment of recurrent oligodendroglioma, we conducted a single-center, single-arm, open-label phase 2 clinical trial of abemaciclib monotherapy in patients with recurrent, IDH-mutant and 1p/19q-codeleted, WHO grade 3 disease who had previously received RT and at least 1 line of alkylating chemotherapy. Here, IDH1 is linked to oligodendroglioma.