This clinical trial is focused on studying a type of lung cancer known as non-small cell lung cancer (NSCLC). The study is investigating the effects of a new treatment combination involving two medications: tiragolumab and atezolizumab. Tiragolumab is an experimental drug that works as an anti-TIGIT antibody, while atezolizumab is an anti-PD-L1 antibody, which is already used in cancer treatment. The trial compares the combination of tiragolumab and atezolizumab with a combination of a placebo and atezolizumab.

The purpose of this study is to evaluate how effective the combination of tiragolumab and atezolizumab is in treating patients with previously untreated, locally advanced, unresectable, or metastatic PD-L1-selected NSCLC. The study will monitor participants over a period to assess their progression-free survival, which means the length of time during and after the treatment that a patient lives with the disease without it getting worse, and overall survival, which is the length of time from either the date of diagnosis or the start of treatment that patients diagnosed with the disease are still alive.

Participants in the study will receive the medications through an intravenous infusion, which means the drugs are given directly into a vein. The study is designed to be double-blinded, meaning neither the participants nor the researchers know who is receiving the actual medication or the placebo, to ensure unbiased results. The trial will help determine if the new combination of medications can provide better outcomes for patients with this type of lung cancer.