A Study of Atezolizumab Plus Carboplatin and Etoposide With or Without Tiragolumab in Patients With Untreated Extensive-Stage Small Cell Lung Cancer

- Symptomatic or actively progressing central nervous system (CNS) metastases - Malignancies other than small cell lung cancer (SCLC) within 5 years prior to randomization, with the exception of those with a negligible risk of metastasis or death treated with expected curative outcome - 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 on screening chest computed tomography (CT) scan - Positive test result for human immunodeficiency virus (HIV) - Active hepatitis B or hepatitis C - Severe infection at the time of randomization - Treatment with any other investigational agent 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 randomization