Pharmaceutical compositions, kits and methods for treating tumors such as glioma and cancers such as leukemia with (R)-2-hydroxyglutarate (R-2HG) are provided, along with therapeutic regimens including treatment of a patient suffering from glioma or leukemia with a MYC-signaling inhibitor followed by or cotemporaneous with treatment with R-2HG, and optionally other chemotherapeutic agents.