A Study of Atezolizumab and Tiragolumab Compared With Durvalumab in Participants With Locally Advanced, Unresectable Stage III Non-Small Cell Lung Cancer (NSCLC) (SKYSCRAPER-03)

Inclusion Criteria:

• Eastern Cooperative Oncology Group (ECOG) Performance Status of 0 or 1
• Histologically or cytologically documented NSCLC with locally advanced, unresectable Stage III NSCLC of either squamous or non-squamous histology
• Whole-body Positron Emission Tomography-Computed Tomography (PET-CT) scan, performed prior and within 42 days of the first dose of concurrent chemoradiotherapy (cCRT)
• At least two prior cycles of platinum-based chemotherapy administered concurrently with radiotherapy (RT), which must be completed within 1 to 42 days prior to randomization in the study (one cycle of cCRT is defined as 21 or 28 days)
• The radiotherapy (RT) component in the cCRT must have been at a total dose of radiation of 60 (±10 percent [%]) gray (Gy) (54 Gy to 66 Gy) administered by intensity modulated RT (preferred) or 3D-conforming technique
• No progression during or following concurrent platinum-based CRT
• A known PD-L1 result
• Life expectancy >/= 12 weeks
• Adequate hematologic and end-organ function
• Female participants must be willing to avoid pregnancy for 90 days after the final dose of tiragolumab and 5 months after the final dose of atezolizumab, or for 3 months after the final dose of durvalumab
• Male participants must remain abstinent or use a condom during the treatment period and for 90 days after the final dose of tiragolumab
• Male participants must not donate sperm during the treatment period and for 90 days after the final dose of tiragolumab

Exclusion Criteria:

• Any history of prior NSCLC and/or any history of prior treatment for NSCLC (participants must be newly diagnosed with unresectable Stage III disease)
• NSCLC known to have a mutation in the epidermal growth factor receptor (EGFR) gene or an anaplastic lymphoma kinase (ALK) fusion oncogene
• Any evidence of Stage IV disease
• Treatment with sequential CRT for locally advanced NSCLC
• Participants with locally advanced NSCLC who have progressed during or after the definitive cCRT prior to randomization
• Any Grade >2 unresolved toxicity from previous CRT
• Grade >= 2 pneumonitis from prior CRT
• 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 screening with the exception of malignancies with a negligible risk of metastasis or death
• Prior allogeneic stem cell or solid organ transplantation
• Active Epstein-Barr virus (EBV) infection or known or suspected chronic active EBV infection at screening
• Treatment with investigational therapy within 28 days prior to initiation of study treatment
• Prior treatment with CD137 agonists or immune checkpoint blockade therapies, including anti-cytotoxic T lymphocyte-associated protein 4, anti-T-cell immunoreceptor with Ig and ITIM domains (anti-TIGIT), anti-PD-1 and anti-PD-L1
• Any prior Grade >/= 3 immune-mediated adverse event or any unresolved Grade > 1 immune-mediated adverse event while receiving any previous immunotherapy agent other than immune checkpoint blockade agents
• Treatment with systemic immunosuppressive medication
• Women who are pregnant, or breastfeeding