Intratumoral DNX-2401 for High Grade Pediatric Brain Tumors

Inclusion Criteria: * The participant or participant's parents or legally acceptable representatives (if applicable) provides written informed consent for the trial and the pediatric participant provides writ-ten assent, where applicable, based on age and country requirements. * Patients with recurrent or refractory high grade malignant brain tumors (high grade glioma, embryonal CNS tumors \[medulloblastomas, ATRT, EMTR, pineoblastoma\], and ependymomas) diagnosis based on initial histopathological diagnosis and further clinical and radiological fol-low-up, in whom gross total resection is not feasible, and with a life expectancy of at least 16 weeks at the time of consent. * Recurrences within the radiation field will be considered if there is confirmed growth of the lesion in two consecutive MRI or if they occur at least 12 weeks after completion of ra-diation therapy, or if there is clear histopathological confirmation of tumor recurrence. * Male and female participants age ≥ 1 years and ≤ 25 years. * A single measurable lesion longer than 10 mm in two perpendicular diameters, considered by the investigator to be accessible for safe stereotactic biopsy and virus injection. * Lansky Performance Status (LPS) ≥ 60 for participants \< 16 years, or Karnofsky Performance Status (KPS) ≥ 60 for participants ≥ 16 years. * No other chemotherapy or immunotherapy in the 4 weeks before inclusion. * Steroids: free off or requiring decreasing or stable corticosteroid dose (≥ 0.05 mg/kg …