A Randomized, Open-label, Phase 3 Study of Sacituzumab Govitecan and Pembrolizumab Versus Treatment of Physician’s Choice and Pembrolizumab in Patients With Previously Untreated, Locally Advanced Inoperable or Metastatic Triple-Negative Breast Cancer, Whose Tumors Express PD-L1

The primary objective of this study is to compare the progression-free survival (PFS) between
sacituzumab govitecan-hziy (SG) and pembrolizumab versus treatment of physician's choice
(TPC) and pembrolizumab in participants with previously untreated, locally advanced
inoperable or metastatic triple-negative breast cancer, whose tumors express programmed cell
death ligand 1 (PD-L1).

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.