A Study of Belrestotug Plus Dostarlimab Compared With Placebo Plus Pembrolizumab in Previously Untreated Participants With Programmed Death Ligand 1 (PD-L1) High Non-small-cell Lung Cancer (NSCLC)

Inclusion Criteria:

• Has a histologically or cytologically confirmed diagnosis of locally advanced,unresectable NSCLC (not eligible for curative surgery and/or definitive radiotherapywith or without chemotherapy), or Metastatic NSCLC

• Has not received prior systemic therapy for their locally advanced or metastaticNSCLC.

• Provides a fresh tumor tissue sample obtained at the time of or after the initialdiagnosis of locally advanced or metastatic NSCLC.

• Has a PD-L1-high (Tumor cells [TC] ≥50%) tumor

• Has measurable disease (at least 1 target lesion) based on RECIST 1.1

• Has an Eastern Cooperative Oncology Group (ECOG) Performance status (PS) score of 0or 1.

• Has adequate organ function

Exclusion Criteria:

• Has NSCLC with a tumor that harbors any of the following molecular alterations:

1. Epidermal growth factor receptor (EGFR) mutations that are sensitive toavailable targeted inhibitor therapy

2. Anaplastic lymphoma kinase (ALK) translocations that are sensitive to availabletargeted inhibitor therapy

3. Any other known genomic aberrations or oncogenic driver mutations for which alocally approved targeted therapy is available for first line treatment oflocally advanced or metastatic NSCLC.

• Has had surgery within 4 weeks of the first dose of study intervention and has notrecovered from AEs (i.e., has any ongoing surgery-related events ≥ Grade 1)/complications related to surgery or has received lung radiation therapy of >30gray (Gy) within 6 months

• Has received prior therapy with any immune checkpoint inhibitors, includingantibodies or drugs targeting PD-(L)1, Cytotoxic T-lymphocyte-associated protein 4 (CTLA-4), T cell immunoglobulin and ITIM domain (TIGIT), or other checkpointpathways.

• Has never smoked, defined as smoking <100 tobacco cigarettes in a lifetime.

• Has an invasive malignancy or history of invasive malignancy other than the diseaseunder study within the last 5 years, with the exception of those with a negligiblerisk of metastasis or death and/or treated with expected curative outcome.

• Has symptomatic, untreated, or actively progressin g brain metastases orleptomeningeal disease

• Has autoimmune disease or syndrome (current or history thereof) that requiredsystemic treatment within the past 2 years.

• Has received any live vaccine within 30 days prior to first dose of studyintervention.

• Has any history of idiopathic pulmonary fibrosis, organizing pneumonia, drug inducedpneumonitis, idiopathic pneumonitis, or evidence of active pneumonitis.

• Has symptomatic ascites, pleural effusion, or pericardial effusion.

• Has active inflammatory bowel disease

• Has a history of significant acute or chronic cardiac diagnosis requiringintervention/treatment in the last 6 months.

• Has severe infection or complication thereof 4 weeks prior to randomisationincluding active tuberculosis.

• Has a history of allogeneic tissue/stem cell transplant or solid organ transplant.