CTLA4 and glioblastoma: However, immune checkpoint inhibitors such as anti‐CTLA‐4 and anti‐PD‐1 antibodies have had little success as monotherapies in the treatment of GBM (Chen & Hambardzumyan, 2018), suggesting that blockade of immune checkpoints alone is not sufficient to restore anti‐tumour immune functions in the GBM TME.