CTLA4 and glioblastoma: In order to obtain a sufficiently high local concentration of nivolumab and ipilimumab while still avoiding potential (systemic) side effects that have traditionally limited clinical trials with anti-cytotoxic T-lymphocyte associated protein-4 (CTLA-4), we hypothesized that local administration following resection of glioblastoma could improve the anti-tumor immune response and improve patient outcome (44).