Fourth Ventricular Administration of Immune Checkpoint Inhibitor (Nivolumab) and Methotrexate or 5-Azacytidine for Recurrent Medulloblastoma, Ependymoma, and Other CNS Malignancies

Nivolumab infusions will be given intraventricularly once every other week for 12 weeks. Dosing will be based upon patient body weight.

2 mg methotrexate infusions will be given intraventricularly daily for 4 consecutive days per week every other week for 12 weeks.

10 mg 5-Azacytidine infusions will be given intraventricularly once weekly for twelve consecutive weeks.