Mycophenolate Mofetil Combined With Radiation Therapy in Glioblastoma

Inclusion Criteria: * Glioblastoma or gliosarcoma (recurrent or newly diagnosed). * Karnofsky Performance Status 60 or greater. * Phase 0: Candidate for clinically indicated re-resection or biopsy of glioblastoma or gliosarcoma per treating physician(s). * Phase 1, Recurrent: Candidate for clinically indicated re-irradiation of glioblastoma or gliosarcoma per treating physician(s) (No more than one prior course of radiation for GBM). * Phase 1, Newly Diagnosed: Candidate for upfront standard of care chemoradiation for glioblastoma or gliosarcoma per treating physician(s), to start no earlier than 14 days post- operatively from last definitive surgery for glioblastoma or gliosarcoma (if more than one surgery done. Ex. biopsy prior to resection). * ANC \>=1,500 cells/mm\^3 within 14 days prior to enrollment. * Patient (men and childbearing age women) agrees to the use of highly effective contraception during study participation and for at least 6 weeks for female patients and 90 days for male patients after final MMF administration. * Ability to understand and the willingness to sign a written informed consent. Exclusion Criteria: * Lack of histopathological diagnosis of the tumor. * Gliomatosis cerebri pattern (tumor involving 3 or more lobes) of disease. * Leptomeningeal disease. * Use of bevacizumab within 8 weeks of study enrollment. * Known history of HIV. * Active hepatitis B or C infection. * Active systemic or central nervous system (CNS) infection. * Grade 4 lymphop…