A Study of Tiragolumab in Combination With Atezolizumab Plus Pemetrexed and Carboplatin/Cisplatin Versus Pembrolizumab Plus Pemetrexed and Carboplatin/Cisplatin in Participants With Previously Untreated Advanced Non-Squamous Non-Small Cell Lung Cancer

Prior treatment

• Severe infection within 4 weeks prior to initiation of study treatment or any active infection that, in the opinion of the investigator, could impact patient safety
• Treatment with investigational therapy within 28 days prior to initiation of study treatment
• Treatment with systemic immunostimulatory agents within 4 weeks or 5 drug-elimination half-lives (whichever is longer) prior to initiation of study treatment
• Treatment with systemic immunosuppressive medication within 2 weeks prior to initiation of study treatment, or anticipation of need for systemic immunosuppressive medication during study treatment

Other illness

• 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
• History of malignancy other than NSCLC within 5 years prior to randomization, with the exception of malignancies with a negligible risk of metastasis or death
• Known allergy or hypersensitivity or other contraindication to any component of the chemotherapy regimen the participant may receive during the study

Lab values

• Mutations in epidermal growth factor receptor (EGFR) gene or anaplastic lymphoma kinase (ALK) fusion oncogene
• Prior treatment with CD137 agonists or immune checkpoint blockade therapies, including anti-cytotoxic T lymphocyte-associated protein 4, anti-TIGIT, anti-PD-1, and anti-PD-L1 therapeutic antibodies

Other

• Pulmonary lymphoepithelioma-like carcinoma subtype of NSCLC
• Symptomatic, untreated, or actively progressing central nervous system (CNS) metastases
• Women who are pregnant, or breastfeeding
• Known targetable c-ROS oncogene 1 (ROS1) or BRAFV600E genomic aberration.

• Eastern Cooperative Oncology Group (ECOG) Performance Status of 0 or 1
• Histologically or cytologically documented locally advanced unresectable or metastatic non-squamous NSCLC that is not eligible for curative surgery and/or definitive chemoradiotherapy
• No prior systemic treatment for metastatic non-squamous NSCLC
• Known tumor programmed death-ligand 1 (PD-L1) status
• Measurable disease, as defined by Response Evaluation Criteria in Solid Tumors, version 1.1 (RECIST v1.1)
• Life expectancy \>= 12 weeks
• Adequate hematologic and end-organ function
• Negative human immunodeficiency virus (HIV) test at screening
• Serology test negative for active hepatitis B virus or active hepatitis C virus at screening.