Trial of NLG802 Indoximod Prodrug Plus Temozolomide for Patients With Progressive Pediatric Brain Cancer

Inclusion Criteria: * Age must be ≥ 5 years and \< 22 years. * Subjects must have relapsed or treatment-refractory primary brain or spinal malignancy of any histology. * Subjects are allowed to have surgical debulking and/or radiation/proton therapy prior to enrollment in this trial. * Tumor tissue is required for central review of tissue diagnosis and biomarker correlate studies. * Collection of baseline blood samples for required biomarker correlate trials. * Performance score: Lansky or Karnofsky performance status score must be ≥ 70. * Life expectancy must be ≥ 3 months. * Hemoglobin ≥ 10 g/dL * Platelets ≥ 100,000/μL * ANC ≥ 1,000/μL * ALT ≤ 3-times upper limit of normal. * Total bilirubin ≤ 1.5-times upper limit of normal. * Adequate renal function * Seizure disorders must be well controlled with antiepileptic medication. * Subjects must be able to swallow pills. * Corticosteroid therapy: When necessary for adrenal replacement, subjects may receive hydrocortisone ≤ 1.7 mg/kg/day, maximum dose 70 mg/day (or equivalent). * At the time of starting protocol therapy, subjects must be ≥ 21 days from the administration of any prior cytotoxic therapy (including chemotherapy). * At the time of starting protocol therapy, subjects must be ≥ 28 days from any radiation or proton therapy. * At the time of starting protocol therapy, subjects must be ≥ 28 days from administration of antibody-based immune checkpoint-inhibitor therapies, tumor-directed vaccines, or cellular immune thera…