A Study of Tiragolumab in Combination With Atezolizumab Compared With Placebo in Combination With Atezolizumab in Patients With Previously Untreated Locally Advanced Unresectable or Metastatic PD-L1-Selected Non-Small Cell Lung Cancer

Inclusion Criteria: * Eastern Cooperative Oncology Group (ECOG) Performance Status of 0 or 1 * Histologically or cytologically documented locally advanced or recurrent NSCLC not eligible for curative surgery and/or definitive radiotherapy with or without chemoradiotherapy, or metastatic Stage IV non-squamous or squamous NSCLC * No prior systemic treatment for metastatic NSCLC * High tumor tissue PD-L1 expression * Measurable disease per Response Evaluation Criteria in Solid Tumors, Version 1.1 (RECIST v1.1) * Adequate hematologic and end-organ function * For participants enrolled in the extended China enrollment phase: current resident of mainland China or Taiwan and of Chinese ancestry. Exclusion Criteria: * Known mutation in the EGFR gene or an ALK fusion oncogene * Symptomatic, untreated, or actively progressing central nervous system metastases * Active or history of autoimmune disease or immune deficiency * History of idiopathic pulmonary fibrosis, organizing pneumonia, drug-induced pneumonitis, or idiopathic pneumonitis, or evidence of active pneumonitis * Malignancies other than NSCLC within 5 years, with the exception of those with a negligible risk of metastasis or death treated with expected curative outcome * Severe infection within 4 weeks prior to initiation of study treatment * Positive test result for human immunodeficiency virus (HIV) * Active hepatitis B or hepatitis C * Treatment with investigational therapy within 28 days prior to initiation of study treatment * Prior treatment with CD137 agonists or immune checkpoint blockade therapies, anti-CTLA-4, anti-TIGIT, anti-PD-1, and anti-PD-L1 therapeutic antibodies * Treatment with systemic immunostimulatory agents within 4 weeks or 5 drug elimination half-lives prior to initiation of study treatment.