The potential of combining checkpoint inhibitors with OV therapy is currently being tested in a phase II clinical study (NCT02798406) where the adenovirus DNX-2401 with pembrolizumab are used in the treatment of glioblastoma (GBM) and gliosarcoma. Interim results of this phase II revealed that there was no dose-limiting toxicity or unexpected safety issues with 47% of the patients experienced clinical benefit and two patients with >94% tumour regression [188]. Following the evaluation of **data** obtained from the phase I trial (NCT00805376), avoidance of tumour immune suppression through checkpoint inhibitors has been strongly implicated as a way to help augment clinical benefit [179]. T-cell exhaustion was partially overcome by DNX-2401 in NCT00805376 as its administration induced a decrease in transmembrane immunoglobulin mucin-3 (TIM-3) (discussed in Section 3.2.1.1) [179].