Pembrolizumab With or Without Maintenance Sacituzumab Tirumotecan (Sac-TMT; MK-2870) in Metastatic Squamous Non-small Cell Lung Cancer (NSCLC) [MK-2870-023]

Inclusion Criteria: * Histologically or cytologically confirmed diagnosis of squamous non-small cell lung cancer (NSCLC) \[Stage IV: M1a, M1b, M1c, American Joint Committee on Cancer Staging Manual, version 8\] * Measurable disease per Response Evaluation Criteria in Solid Tumours (RECIST) 1.1 as assessed by the local site investigator/radiology * Has life expectancy ≥3 months * Has Eastern Cooperative Oncology Group Performance Status (ECOG PS) score of 0 or 1 assessed within 7 days prior to allocation * Archival tumor tissue sample or newly obtained core, incisional, or excisional biopsy of a tumor lesion not previously irradiated has been provided * Human immunodeficiency virus (HIV)-infected participants must have well controlled HIV on antiretroviral therapy (ART) * Participants who are hepatitis B surface antigen (HBsAg)-positive are eligible if they have received hepatitis B virus (HBV) antiviral therapy for at least 4 weeks and have undetectable HBV viral load before allocation * Participants with history of hepatitis C virus (HCV) infection are eligible if HCV viral load is undetectable at screening * Participants who have adverse events (AEs) due to previous anticancer therapies must have recovered to Grade ≤1 or baseline (participants with endocrine-related AEs who are adequately treated with hormone replacement are eligible) * Has adequate organ function * For Maintenance only (prior to randomization): is without disease progression of their NSCLC, as determined …