PDCD1 and medulloblastoma: Nevertheless, clinical trials, such as NCT02359565 and NCT03173950, which target PD-1 with pembrolizumab and nivolumab, are recruiting patients with CNS tumors, including medulloblastoma, with a high mutational burden (e.g., rare constitutional MMR-deficiency syndrome – CMMRD) and recurrent or refractory tumors (47).