A Phase I Study of AdV-tk + Prodrug Therapy in Combination With Radiation Therapy for Pediatric Brain Tumors

Inclusion Criteria: * Patients must be 3 years of age or older * Patients must be planning to undergo standard of care treatment with surgery and radiation therapy. * Patients must have malignant glioma or recurrent ependymoma * Tumor must be accessible for injection and must not be located in the brainstem or deep midbrain * Performance Score: Karnofsky ≥60% if \>10y/o, Lansky ≥60 if ≤10y/o * Bone Marrow Function: Patients must have adequate bone marrow function defined as a peripheral absolute neutrophil count ≥ 1000/µl, platelet count ≥ 100,000/µl (transfusion independent) and hemoglobin ≥ 8.0 gm/dL * Renal Function: Patients must have serum creatinine ≤ 1.5 times upper limit of institutional normal for age and/or GFR ≥ 70 mL/min/1.73 m2. * Hepatic Function: Bilirubin ≤ 1.5 times institutional normal; SGPT (ALT) \< 3 times institutional normal * Serum electrolyte values (sodium, potassium, magnesium, calcium) must be checked prior to enrollment and clinically significant abnormalities corrected prior to surgery/AdV-tk injection * Patients with seizure disorder may be enrolled if well controlled * Signed informed consent according to institutional guidelines must be obtained Exclusion Criteria: * Prior or ongoing liver disease including known cirrhosis, hepatitis B or C infection but not to exclude patients with a distant history of resolved hepatitis A infection * Patients on immunosuppressive drugs (with exception of corticosteroid) * Known history of HIV or underlying immunodeficiency * Patients with acute infections (viral, bacterial or fungal infections requiring therapy) * Pregnant or breast-feeding patients. Female patients of childbearing age must have negative serum or urine pregnancy test within 1 week of beginning therapy * Other serious co-morbid illness or compromised organ function * No other investigational anti-tumor agents within 30 days prior to study entry or during active participation in the study (defined as from study entry until tumor progression)