Anti-PD-1 in Combination With Chemotherapy as First-Line Treatment to Lung Cancer

This is a Phase II, open-label, 4-cohort study of the monoclonal antibody BGB-A317 in combination with standard platinum-based chemotherapy in participants with advanced NSCLC or SCLC. The 4 cohorts will be enrolled concurrently including non-squamous NSCLC Cohort, squamous NSCLC Cohort A, squamous NSCLC Cohort B and SCLC Cohort. Participants with a mixed adenocarcinoma and squamous cell NSCLC will be allocated to one of the NSCLC cohorts based on the predominant histopathological profile. (e.g., participants with adenocarcinoma component accounting for \> 50% will be allocated to non-squamous NSCLC cohort.). Participants with squamous NSCLC will be sequentially enrolled into either of the 2 squamous NSCLC cohorts by the trial stage i.e. the sequence of the enrollment for the squamous NSCLC cohorts will be as Cohort A safety run-in Stage, followed by Cohort B safety run-in Stage, Cohort A dose-expansion stage and Cohort B dose-expansion Stage.