CTLA4 and head and neck squamous cell carcinoma: In the CIAO-trial, investigating neoadjuvant ICB in patients with mainly HPV-positive oropharyngeal HNSCC, Ferrarotto et al. observed a primary tumor MPR in only 2 of 25 evaluable patients (8%) after two cycles of durvalumab (anti-PD-1, n = 13) or durvalumab with tremelimumab (anti-CTLA-4, n = 12), one in each treatment arm39.