Additional Study Information: The purpose of this study is to test the safety of the investigational study drug CB-839 when used in combination with radiation therapy and temozolomide chemotherapy. This study tests different doses of CB-839 to see which dose is safer for people. There will be up to 40 people taking part in this study. Another purpose of this study is to test magnetic resonance spectroscopy (MRS) scans, which are a way to take pictures of your type of cancer. MRS scans are based on the same technology as MRI scans, however MRI scans evaluate the structure of your brain while MRS scans evaluate the amount of various chemicals in your brain. The study doctors want to see if MRS scans are able to detect changes in certain tumor markers because of treatment with the highest dose of CB-839 when used in combination with radiation and temozolomide. The MRS scans done in this study will not be combined with any planned clinical MRI scans. There will be about 10 people taking part in this study as part of the expansion part.