Embryonal Tumor Of Brain

The goal of this clinical trial is to learn if intratumoral administration of DNX-2401 works to treat recurrent and refractory high grade brain tumors in children and young adults. It will also learn about the safety of DNX-2401. The main questions it aims to answer are: * Does a single intratumoral administration of DNX-2401 elicit tumor response and improve survival? * Is a single intratumoral administration of DNX-2401 safe and well tolerated? Participants will: * Undergo surgery for tumor biopsy followed by a single intratumoral administration of DNX-2401 * Visit the clinic periodically for checkups and tests