Patients were randomized to receive CMAB819 or Nivolumab 480 mg by intravenous infusion every 4 weeks until documented disease progression, discontinuation, withdrawal of consent, or up to 4 doses in subjects without disease progression, whichever occurs earlier. After completing 4 doses of therapy, administer of CMAB819 480 mg intravenous (IV) solution for injection every 4 weeks until documented disease progression, discontinuation, withdrawal of consent or the study ends. Randomization was stratified by Eastern Cooperative Oncology Group (ECOG) performance status ECOG (0 versus 1), sex (male versus female), weight （≤60 kg versus >60kg）and clinical trial institution (up to 20 centers) .
The purpose of this study is to compare the pharmacokinetic, safety, immunogenicity and efficacy of CMAB819 and Nivolumab in subjects with recurrent or metastatic head and neck squamous cell carcinoma., after failure of prior platinum-based chemotherapy.