Study of Sacituzumab Govitecan-hziy and Pembrolizumab Versus Treatment of Physician's Choice and Pembrolizumab in Patients With Previously Untreated, Locally Advanced Inoperable or Metastatic Triple-Negative Breast Cancer

Key Inclusion Criteria: * Individuals with locally advanced, inoperable, or metastatic triple-negative breast cancer (TNBC) who have not received previous systemic therapy for advanced disease and whose tumors are programmed cell death ligand 1 (PD-L1) positive at screening. * Individuals must have completed treatment for Stage I to III breast cancer, if indicated, and ≥ 6 months must have elapsed between completion of treatment with curative intent and first documented local or distant disease recurrence. * Individuals presenting with de novo metastatic TNBC are eligible for this study. * TNBC status and tumor PD-L1 combined positive score (CPS) will be confirmed centrally on a recent or archival tumor specimen. * Individuals must have measurable disease by computed tomography (CT) or magnetic resonance imaging (MRI) as per Response Evaluation Criteria in Solid Tumors (RECIST) Version 1.1 criteria as evaluated locally. * Eastern Cooperative Oncology Group (ECOG) performance status score of 0 or 1. * Demonstrates adequate organ function * Male and female individuals of childbearing potential who engage in heterosexual intercourse must agree to use protocol-specified method(s) of contraception. * Individuals with HIV must be on antiretroviral therapy (ART) and have a well-controlled HIV infection/disease. Key Exclusion Criteria: * Positive serum pregnancy test or women who are lactating. * Received prior therapy with an agent directed to another stimulatory or coinhibitory T-cell receptor. * Individuals may not have received systemic anticancer treatment (with the exception of endocrine therapy) within the previous 6 months or radiation therapy within 2 weeks prior to enrollment. * Individuals may not be participating in a study with an investigational agent or investigational device within 4 weeks prior to randomization. Individuals participating in observational studies are eligible. * Have previously received topoisomerase 1 inhibitors or antibody drug conjugates containing a topoisomerase inhibitor. * Have an active second malignancy. * Have active serious infection requiring antibiotics. * Individuals positive for HIV-1 or 2 with a history of Kaposi sarcoma and/or Multicentric Castleman Disease. * Have active hepatitis B virus (HBV) or hepatitis C virus (HCV) infection. * Has an active autoimmune disease that has required systemic treatment in the past 2 years. Note: Other protocol defined Inclusion/Exclusion criteria may apply.