PDCD1 and head and neck squamous cell carcinoma: However, some phase III studies investigating the combination therapy of PD1/PD-L1 inhibitors, such as nivolumab (CheckMate 651) or durvalumab (EAGLE and KESTREL), combined with anti CTLA-4-mAb (e.g., ipilimumab or tremilimumab), did not reveal a statistically improvement in OS compared to the EXTREME treatment regimen or standard of care in patients with R/M HNSCC (AstraZeneca communication https://www.astrazeneca.com/media-centre/press-releases/2021/update-on-kestrel-phase-iii-trial-for-imfinzi.html, accessed on 22 September 2022 [60,78]).