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