Study of the IDO Pathway Inhibitor, Indoximod, and Temozolomide for Pediatric Patients With Progressive Primary Malignant Brain Tumors

Eligibility Criteria * Age: 3-21 years. * Group 1 or Group 3: histologically proven initial diagnosis of primary malignant brain tumor, with no known curative treatment options. * Group 2: histologically proven initial diagnosis of high-grade glioma (WHO grade III and IV), ependymoma, medulloblastoma, or other primary central nervous system tumor. * Group 3b: Patients with a radiographic diagnosis or histologically proven diagnosis of diffuse intrinsic pontine glioma (DIPG). * MRI confirmation of tumor progression or regrowth. * Patients must be able to swallow whole capsules. * Patients with metastatic disease are eligible for enrollment. * Lansky or Karnofsky performance status score must be \> 50%. * Seizure disorders must be well controlled on antiepileptic medication. * DIPG patients enrolled to Group 3b must not have been previously treated with radiation or any medical therapy. * Patients previously treated with temozolomide, cyclophosphamide, and/or etoposide are eligible for enrollment. Exclusion Criteria * Prior invasive malignancy, other than the primary central nervous system tumor, unless the patient has been disease free and off therapy for that disease for a minimum of 3 years * Patients with baseline QTc interval of more than 470 msec at study entry, and patients with congenital long QTc syndrome. * Active autoimmune disease