ASCENTAn International, Multi-Center, Open-Label, Randomized, Phase III Trial of Sacituzumab Govitecan Versus Treatment of Physician Choice in Patients With Metastatic Triple-Negative Breast Cancer Who Received at Least Two Prior Treatments

Study start date: November 7, 2017

Key Inclusion Criteria: * Histologically or cytologically confirmed TNBC based on the most recent analyzed biopsy or other pathology specimen. Triple negative is defined as \<1% expression for estrogen receptor (ER) and progesterone receptor (PR) and negative for human epidermal growth factor receptor 2 (HER2) by in-situ hybridization. * Refractory to or relapsed after at least two prior standard therapeutic regimens for advanced/metastatic TNBC. * Prior exposure to a taxane in localized or advanced/metastatic setting. * Eligible for one of the chemotherapy options listed as TPC (eribulin, capecitabine, gemcitabine, or vinorelbine) as per investigator assessment. * Eastern Cooperative Oncology Group (ECOG) performance score of 0 or 1. * Measurable disease by computed tomography (CT) or magnetic resonance imaging (MRI) as per Response Evaluation Criteria in Solid Tumors version 1.1 (RECIST 1.1). Bone-only disease is not permitted. * At least 2 weeks beyond prior anti-cancer treatment (chemotherapy, endocrine therapy, radiotherapy, and/or major surgery), and recovered from all acute toxicities to Grade 1 or less (except alopecia and peripheral neuropathy). * At least 2 weeks beyond high dose systemic corticosteroids (however, low dose corticosteroids \< 20 mg prednisone or equivalent daily are permitted provided the dose is stable for 4 weeks). * Adequate hematology without ongoing transfusional support (hemoglobin \> 9 g/dL, absolute neutrophil count (ANC) \> 1,500 per mm\^3, platelets \> 100,000 per mm\^3). * Adequate renal and hepatic function (creatinine clearance \[CrCL\] \> 60 mL/min, bilirubin ≤ 1.5 institutional upper limit of normal \[IULN\], aspartate aminotransferase \[AST\] and alanine aminotransferase \[ALT\] ≤ 2.5 x IULN or ≤ 5 x IULN if known liver metastases and serum albumin ≥3 g/dL). * Recovered from all toxicities to Grade 1 or less by National Cancer Institute common terminology criteria for adverse events (NCI CTCAE) v4.03 (except alopecia or peripheral neuropathy that may be Grade 2 or less) at the time of randomization. Participants with Grade 2 neuropathy are eligible but may not receive vinorelbine as TPC. * Participants with treated, non-progressive brain metastases, off high-dose steroids (\>20 mg prednisone or equivalent) for at least 4 weeks can be enrolled in the trial. Key Exclusion Criteria: * Women who are pregnant or lactating. * Women of childbearing potential or fertile men unwilling to use effective contraception during study and up to three months after treatment discontinuation in women of child-bearing potential and six months in males post last study drug. * Participants with Gilbert's disease. * Participants with non-melanoma skin cancer or carcinoma in situ of the cervix are eligible, while participants with other prior malignancies must have had at least a 3-year disease-free interval. * Participants known to be human immunodeficiency (HIV) positive, hepatitis B positive, or hepatitis C positive. * Infection requiring antibiotic use within one week of randomization. * Other concurrent medical or psychiatric conditions that, in the Investigator's opinion, may be likely to confound study interpretation or prevent completion of study procedures and follow-up examinations. Note: Other protocol defined Inclusion/Exclusion criteria may apply.