Researchers are looking for new ways to treat locally advanced non-small cell lung cancer (NSCLC) that is unresected and has a gene mutation called KRAS G12C. Researchers want to learn if calderasib (MK-1084) can be given with durvalumab, an immunotherapy, to treat NSCLC after chemotherapy and radiation therapy.

The goal of this trial is to learn if participants who receive calderasib and durvalumab live longer without the cancer growing or spreading compared to participants who receive placebo and durvalumab.

DRUG: Calderasib

Tablet for oral administration.

BIOLOGICAL: Durvalumab

Solution for intravenous (IV) infusion.

OTHER: Placebo to MK-1084

Placebo to MK-1084.

• Progression-Free Survival (PFS)

The main inclusion criteria include but are not limited to the following:

• Has a histological or cytological diagnosis of locally advanced, unresected Stage II (node-positive) to III non-small cell lung cancer (NSCLC) with predominantly nonsquamous histology.
• Has completed definitive platinum-based concurrent chemoradiotherapy (CCRT) prior to enrollment, without disease progression.
• Has provided a tumor tissue sample for central laboratory testing of Kirsten rat sarcoma G12C (KRAS G12C) status, programmed cell death ligand 1 (PD-L1) status, and biomarker research.
• Tumor tissue sample has a demonstrated presence of KRAS G12C mutation and an evaluable PD-L1 status result.
• If human immunodeficiency virus (HIV)-infected, has well-controlled HIV on antiretroviral therapy (ART).
• If hepatitis B surface antigen (HBsAg)-positive, has undetectable hepatitis B virus (HBV) viral load and has received HBV antiviral therapy.
• If has a history of hepatitis C virus (HCV) infection, has undetectable HCV viral load.
• Has a body weight ≥35 kg.

The main exclusion criteria include but are not limited to the following:

• Has a diagnosis of small cell lung cancer or mixed tumors with small cell elements.
• Has a gastrointestinal disorder affecting absorption or is unable to swallow orally administered medication.
• Has active inflammatory bowel disease requiring immunosuppressive medication or previous clear history of inflammatory bowel disease.
• Has uncontrolled, significant cardiovascular disease or cerebrovascular disease.
• Is HIV-infected with a history of Kaposi's sarcoma and/or Multicentric Castleman's Disease.
• Has received prior treatment (other than definitive CCRT) for NSCLC.
• Has a known additional malignancy that is progressing or has required active treatment within the past 3 years.
• Has an active autoimmune disease that has required systemic treatment in the past 2 years.
• Has a history of, or has current, (noninfectious) pneumonitis/interstitial lung disease that required/requires steroids.
• Has an active infection requiring systemic therapy.
• Has a history of stem cell/solid organ transplant.
• Has not adequately recovered from major surgery or has ongoing surgical complications.