Oncolytic Adenovirus, DNX-2401, for Naive Diffuse Intrinsic Pontine Gliomas

Inclusion Criteria: 1. Informed consent OF PATIENT OR PARENTS 2. Patient must be, in the investigator opinion, able to comply with all the protocol procedures. 3. Age 1 - 18 years 4. Negative pregnant blood test in case of fertile women (A woman is considered of childbearing potential (WOCBP), i.e. fertile, following menarche and unless permanently sterile. Permanent sterilization methods include hysterectomy, bilateral salpingectomy and bilateral oophorectomy. 5. Patient newly diagnosed of DIPG in MRI 6. Lansky Performance Status ≥ 70 before inclusion 7. Lesion considered by the investigator to be accessible for stereotactic biopsy. Lesion location will allow injection without entrance of virus in the ventricular system. 8. No previous treatment for DIPG Exclusion Criteria: 1. Severe infections or intercurrent medical conditions including, but not limited to, severe renal, hepatic, heart or bone marrow failure, that, on investigator´s criteria, do not allow the inclusion. Patients must be afebrile at baseline \[i.e., \< 38 degrees (Cº)\]. 2. Investigational medication in the previous 30 days. 3. Subjects with immunodeficiency, autoimmune conditions or active hepatitis. 4. Any medical or psychological condition that might interfere with the subject's ability to participate if older than 16 years or parents ability when younger than 16, or give informed consent or would compromise the patient's ability to tolerate therapy or any disease that will obscure toxicity or dangerously alter drug metabolism. 5. Tumor with multiple locations or doubt in MRI of a DIPG. 6. Pregnant or breast-feeding females will be excluded, due to the risk for the fetal development of a recombinant virus containing genes related to cellular growth and differentiation. 7. Severe bone marrow hypoplasia. 8. AST (aspartate transaminase) and/or ALT (alanine transaminase)\> 3 times over upper normal laboratory level 9. Neutrophils \< 1 x 109/L 10. Thrombocytes ≤ 100 x 109/L 11. Hemoglobin \< 9g/dl 13\. Patients with Li-Fraumeni Syndrome or with a known germ line deficit in the retinoblastoma gene or its related pathways. 14\. Vaccinations of any kind within 30 days prior to DNX-2401 administration. 15. Transfusions or medications (G-CSF) to treat pancytopenia or other hematological conditions within 28 days of baseline.