A Multi-Center, Open Label Phase Ib/II Clinical Study to Evaluate JS001 in Patients With Advanced Gastric Adenocarcinoma, Esophageal Squamous Cell Carcinoma, Nasopharyngeal Carcinoma and Head and Neck Squamous Cell Carcinoma

This study is planned to conduct the 3 mg/kg dose group study at first. After enrollment, the subjects will be administered every 2 weeks (Q2W) with 4 weeks as a cycle, until absence of further benefits, acceptable toxicity, investigator decision, consent withdrawal or death. If patient experiences 1st onset of disease progression and investigator judges that patient will obtain clinical benefit from the study treatment, patient can continue the study treatment after the discussion between investigator and medical monitor from sponsor or authorized CRO and approval is obtained afterwards. If the subject develops 2nd disease progression after 1st disease progression, he/she should permanently withdraw from the study treatment.

Subjects will receive corresponding regimen of standard first-line chemotherapy combined with JS001 360 mg once every 3 weeks (Q3W). JS001 360 mg Q3W can be administrated after the end of chemotherapy until absence of further benefits judged by the investigator, disease progression, occurrence of intolerable toxicity, investigator's decision, and withdrawal of informed consent by the subject, or death.

Subjects will receive corresponding regimen of standard first-line chemotherapy combined with JS001 240 mg once every 3 weeks (Q3W). JS001 240 mg Q3W can be administrated after the end of chemotherapy until absence of further benefits judged by the investigator, disease progression, occurrence of intolerable toxicity, investigator's decision, and withdrawal of informed consent by the subject, or death.