Coformulation of Pembrolizumab/Vibostolimab (MK-7684A) Versus Pembrolizumab (MK-3475) Monotherapy for Programmed Cell Death 1 Ligand 1 (PD-L1) Positive Metastatic Non-Small Cell Lung Cancer (MK-7684A-003, KEYVIBE-003)

Inclusion Criteria:

* Has a histologically or cytologically confirmed diagnosis of Stage IV: M1a, M1b, or M1c non-small cell lung cancer (NSCLC) per the American Joint Committee on Cancer (AJCC) Staging Manual, version 8
* Has measurable disease based on Response Evaluation Criteria in Solid Tumors (RECIST) 1.1, as determined by the local site assessment
* Has confirmation that epidermal growth factor receptor (EGFR)-, anaplastic lymphoma kinase (ALK)-, or reactive oxygen species proto-oncogene 1 (ROS1)-directed therapy is not indicated as primary therapy and absence of ALK and ROS1 gene rearrangements
* Has provided tumor tissue that demonstrates Programmed Cell Death 1 Ligand 1 (PD-L1) expression in ≥1% of tumor cells as assessed by immunohistochemistry (IHC) at a central laboratory
* Has an Eastern Cooperative Oncology Group (ECOG) performance score of 0 or 1 assessed within 7 days prior to randomization
* Has a life expectancy of at least 3 months
* A female participant is eligible to participate if she is not pregnant or breastfeeding, and at least one of the following conditions applies:

  * Is not a woman of childbearing potential (WOCBP)
  * Is a WOCBP and using a contraceptive method that is highly effective (with a failure rate of \<1% per year), with low user dependency or be abstinent from heterosexual intercourse as their preferred and usual lifestyle (abstinent on a long term and persistent basis), during the intervention period and for at least 120 days after the last dose of study intervention
* Has adequate organ function

Exclusion Criteria:

* Has a known history of an additional malignancy, except if the participant has undergone potentially curative therapy with no evidence of that disease recurrence for at least 3 years since initiation of that therapy
* Has received prior systemic chemotherapy or other targeted or biological antineoplastic therapy for their metastatic NSCLC.

  * Prior treatment with chemotherapy and/or radiation as part of neoadjuvant/adjuvant or chemoradiation therapy for nonmetastatic NSCLC is allowed as long as therapy was completed at least 6 months before the diagnosis of metastatic NSCLC.
  * Participants must have recovered from all AEs due to previous therapies to Grade ≤1 or baseline. Participants with Grade ≤2 neuropathy may be eligible. Participants with endocrine-related AEs Grade ≤2 requiring treatment or hormone replacement may be eligible.
* Has received prior therapy with an anti-programmed cell death receptor 1 (PD-1), anti-programmed cell death receptor ligand 1 (PD-L1), or anti-programmed cell death receptor ligand 2 (PD-L2) agent or with an agent directed to another stimulatory or co-inhibitory T-cell receptor (eg, cytotoxic T-lymphocyte-associated protein 4 (CTLA-4), OX-40, CD137)
* Has received previous treatment with another agent targeting the T cell immunoreceptor with immunoglobulin (Ig) and immunoreceptor tyrosine-based inhibition motif (ITIM) domains (TIGIT) receptor pathway
* Has received radiotherapy within 2 weeks of start of study intervention. Participants must have recovered from all radiation-related toxicities, not require corticosteroids, and not have had radiation pneumonitis. A 1-week washout is permitted for palliative radiation (≤2 weeks of radiotherapy) to non-central nervous system (CNS) disease
* Has received a live or live-attenuated vaccine within 30 days prior to the first dose of study intervention. Administration of killed vaccines is allowed.

  * Any licensed COVID-19 vaccine (including for Emergency Use) in a particular country is allowed in the study as long as they are mRNA vaccines, adenoviral vaccines, or inactivated vaccines. These vaccines will be treated just as any other concomitant therapy.
  * Investigational vaccines (i.e., those not licensed or approved for Emergency Use) are not allowed.
* Is currently participating in or has participated in a study of an investigational agent or has used an investigational device within 4 weeks prior to the first dose of study intervention
* Has known active or untreated CNS metastases and/or carcinomatous meningitis. Participants with previously treated brain metastases may participate provided they are radiologically stable for at least 4 weeks by repeat imaging, clinically stable, and without requirement of steroid treatment for at least 14 days prior to first dose of study intervention
* Has severe hypersensitivity (≥Grade 3) to pembrolizumab/vibostolimab or pembrolizumab and/or any of its excipients
* Has an active autoimmune disease that has required systemic treatment in past 2 years (ie, with use of disease modifying agents, corticosteroids, or immunosuppressive drugs). Replacement therapy (eg, thyroxine, insulin, or physiologic corticosteroid replacement therapy for adrenal or pituitary insufficiency) is not considered a form of systemic treatment and is allowed.
* Has a diagnosis of immunodeficiency or is receiving chronic systemic steroid therapy (in dosing exceeding 10 mg daily of prednisone equivalent) or any other form of immunosuppressive therapy within 7 days prior to the first dose of study intervention
* Has a history of (non-infectious) pneumonitis that required steroids or has current pneumonitis
* Has a known history of interstitial lung disease. Lymphangitic spread of the NSCLC is not exclusionary.
* Has an active infection requiring systemic therapy
* Has a known history of human immunodeficiency virus (HIV) infection. No HIV testing is required unless mandated by local health authority
* Has a known history of Hepatitis B or known active Hepatitis C virus infection
* Has a history or current evidence of any condition, therapy, or laboratory abnormality that prevents the participant from receiving platinum-doublet chemotherapy for first line NSCLC, or that might confound the results of the study, interfere with the participant's participation for the full duration of the study, or is not in the best interest of the participant to participate, in the opinion of the treating investigator.
* Has a known psychiatric or substance abuse disorder that would interfere with the participant's ability to cooperate with the requirements of the study