Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1

Histologically or cytologically confirmed diagnosis of advanced or metastatic non squamous NSCLC that is not eligible for curative surgery and/or definitive chemoradiotherapy

Measurable disease, as defined by RECIST v1.1

No prior systemic treatment for advanced or metastatic NSCLC

Documentation of the presence of a KRAS G12C mutation

Documentation of known PD-L1 expression status in tumor tissue

Availability of a representative tumor specimen

Adequate end-organ function

Eligible to receive a platinum-based chemotherapy regimen

Known concomitant second oncogenic driver with available targeted treatment

Symptomatic, untreated, or actively progressing central nervous system (CNS) metastases

Spinal cord compression not definitively treated with surgery and/or radiation or previously diagnosed and treated spinal cord compression without evidence that disease has been clinically stable for >=2 weeks prior to randomization

History of leptomeningeal disease

Uncontrolled tumor-related pain

Uncontrolled pleural effusion, pericardial effusion, or ascites requiring recurrent drainage procedures (once a month or more frequently)

Exclusion Criteria Related to Current or Prior Treatments:

Any anti-cancer systemic therapy, including hormonal therapy, within 21 days prior to randomization, or is expected to require any other form of antineoplastic therapy while in the study

Radiation therapy including palliative RT to bone metastases within 2 weeks prior to randomization and RT to the lung >30Gy within 6 months prior to randomization

Prior treatment with KRAS G12C inhibitors or pan-KRAS/RAS inhibitors

Treatment with systemic immunosuppressive or immunostimulatory medications, including CD137 agonists and immune checkpoint inhibitors

Current treatment with medications that are well known to prolong the QT interval

Treatment with therapeutic oral or IV antibiotics within 2 weeks prior to randomization

Prior allogeneic stem cell or solid organ transplantation

Exclusion Criteria Related to General Health:

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 (e.g., 5-year overall survival [OS] rate >90%), such as adequately treated carcinoma in situ of the cervix, non melanoma skin carcinoma, localized prostate cancer, ductal breast carcinoma in situ, or Stage I uterine cancer

Individuals with chronic diarrhea, short bowel syndrome or significant upper gastrointestinal surgery including gastric resection, a history of inflammatory bowel disease (e.g., Crohn's disease or ulcerative colitis) or any active bowel inflammation (including diverticulitis), malabsorption syndrome, conditions that would interfere with enteral absorption

History of idiopathic pulmonary fibrosis, organizing pneumonia (e.g., bronchiolitis obliterans), drug-induced pneumonitis, or idiopathic pneumonitis, or evidence of active pneumonitis on the screening chest computed tomography scan

Significant cardiovascular disease within 3 months prior to screening