Study of Pembrolizumab (MK-3475) Monotherapy Versus Sacituzumab Govitecan in Combination With Pembrolizumab for Participants With Metastatic Non-small Cell Lung Cancer (NSCLC) With Programmed Cell Death Ligand 1 (PD-L1) Tumor Proportion Score (TPS) ≥50% (MK-3475-D46)

Has history of a second malignancy, unless potentially curative treatment has been completed with no evidence of malignancy for 3 years

Has received prior systemic chemotherapy or other targeted or biological antineoplastic therapy for their metastatic NSCLC

Has previously received treatment with Topoisomerase 1 inhibitors or Trop-2 targeted therapy

Has received prior therapy with an anti-programmed cell death 1 protein (anti-PD-1), anti-programmed cell death ligand 1 (anti-PD-L1), or anti anti- programmed cell death ligand 2 (PD-L2) agent or with an agent directed to another stimulatory or coinhibitory T-cell receptor

Has received prior radiotherapy within 2 weeks of start of study intervention or has radiation-related toxicities requiring corticosteroids

Has received radiation therapy to the lung that is \>30 Gray (Gy) within 6 months of the first dose of study intervention

Has received a live or live-attenuated vaccine within 30 days before the first dose of study intervention

Has received an investigational agent or has used an investigational device within 4 weeks before study intervention administration

Has cardiac disease

* Myocardial infarction or unstable angina pectoris within 6 months of enrollment

* History of serious ventricular arrhythmia, high-grade atrioventricular block, or other cardiac arrhythmias requiring antiarrhythmic medications; history of QT interval prolongation

* New York Heart Association (NYHA) Class III or greater congestive heart failure or left ventricular ejection fraction of \<40%

Has active chronic inflammatory bowel disease

Has diagnosis of immunodeficiency or is receiving chronic systemic steroid therapy or any other form of immunosuppressive therapy within 7 days prior the first dose of study medication

Has known active central nervous system (CNS) metastases and/or carcinomatous meningitis

Has severe hypersensitivity (≥Grade 3) to pembrolizumab or sacituzumab govitecan and/or any of their excipients

Has active autoimmune disease that has required systemic treatment in past 2 years except replacement therapy

History of (noninfectious) pneumonitis/interstitial lung disease that required steroids or has current pneumonitis/interstitial lung disease

Has active infection requiring systemic therapy

Has history of human immunodeficiency virus (HIV) infection

History of hepatitis B or known active hepatitis C virus infection

Has history or current evidence of any condition, therapy, laboratory abnormality, or other circumstance that might confound the results of the study or interfere with the participant's participation for the full duration of the study, such that it is not in the best interest of the participant to participate, in the opinion of the treating investigator

Have not adequately recovered from major surgery or have ongoing surgical complications

What this study is about