CTLA4 and glioblastoma: A phase I clinical trial on recurrent GBM (rGBM) confirmed that perioperative intravenous administration of ipilimumab (IPI, a CTLA-4 inhibitor) ± nivolumab (NIVO, a PD-1 inhibitor) in rGBM was safe, and exploratory findings merit further investigation of immunotherapy for GBM (22).