Phase 3 Study of Vorasidenib (S095032/AG-881) in Asian Participants With Residual or Recurrent Grade 2 Glioma With an IDH1 orIDH2 Mutation

Inclusion Criteria: * Be at least 12 years of age (for Randomized Double-Blind phase) and weigh at least 40 kg. * Have a Karnofsky Performance Scale (KPS) score (for participants ≥16 years of age) or Lansky Play Performance Scale (LPPS) score (for participants \<16 years of age) of ≥80%. * Have Grade 2 oligodendroglioma or astrocytoma per WHO 2016 criteria. * Have had at least 1 prior surgery for glioma with the most recent one having occurred at least 1 year (-1 month) and not more than 5 years (+3 months) before randomization, and no other prior anticancer therapy, including radiotherapy and not be in need of immediate chemotherapy or radiotherapy. * Have confirmed IDH1 (IDH1 R132H/C/G/S/L mutation variants tested) or IDH2 (IDH2 R172K/M/W/S/G mutation variants tested) gene mutation status disease * Have MRI-evaluable, measurable, non-enhancing disease, as confirmed by the BIRC for double blind part. Exclusion Criteria: * Have had any prior anticancer therapy other than surgery (biopsy, sub-total resection, gross-total resection) for treatment of glioma including systemic chemotherapy, radiotherapy, vaccines, small-molecules, IDH inhibitors, investigational agents, laser ablation, etc. * Concurrent active malignancy except for a) curatively resected nonmelanoma skin cancer or b) curatively treated carcinoma in situ. Participants with previously treated malignancies are eligible provided they have been disease-free for 3 years at Screening. * Have any other acute or chronic medical or psychiatric condition that may increase the risk associated with the study participation or investigational product administration or may interfere with the interpretation of study results. * Have known active hepatitis B virus (HBV) or hepatitis C virus (HCV) infection, known positive human immunodeficiency virus antibody results, or AIDS-related illness. Participants with a sustained viral response to HCV treatment or immunity to prior HBV infection will be permitted. Participants with chronic HBV that is adequately suppressed by institutional practice will be permitted.