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.