This study evaluates the safety and usefulness of a new investigational drug called AG-881-C-004 in participants with residual or recurrent Grade 2 glioma (a type of brain cancer) that have a IDH1 or IDH2 mutation. Participants will be randomly assigned to take either the study drug or a placebo (a medically inactive substance). If your disease progresses and you were receiving the placebo, you will be given the opportunity to start taking the study drug.

Glioblastoma adaptive, global, innovative learning environment or GBM AGILE trial is to identify effective therapies and improve survival for a type of brian cancer called glioblastoma (GBM) and to match effective therapies with adult patients with newly diagnosed or recurring glioblastoma. Eligible participants will have a 50/50 chance of taking either standard therapy medications or a medication not yet approved by the FDA called regorafenib during their standard of care treatment for GBM.