A Study of Etirinotecan Pegol (NKTR-102) Versus Treatment of Physician's Choice (TPC) in Patients With Metastatic Breast Cancer Who Have Stable Brain Metastases and Have Been Previously Treated With an Anthracycline, a Taxane, and Capecitabine

Inclusion Criteria:

• Female or male, age ≥ 18 years.
• Histologically-confirmed carcinoma of the breast (either the primary or metastaticlesions) for whom single-agent cytotoxic chemotherapy is indicated. Patients may haveeither measurable or non-measurable disease according to RECIST version 1.1.
• Patients must have a history of brain metastases that are non-progressing.
• For triple-negative breast cancer, a minimum of 1 prior cytotoxic chemotherapy regimenmust have been administered for the indication of metastatic disease.Depending onreceptor status, 1 or 2 prior cytotoxic regimens are required prior to enrollment inthis trial; hormonal and/or human epidermal growth factor receptor 2 (HER2) -targetedagents may be required.
• Have had prior therapy (administered in the neoadjuvant, adjuvant, and/or metastaticsetting) with an anthracycline, a taxane, and capecitabine (prior anthracycline can beomitted if not medically appropriate or contraindicated for the patient).
• Last dose of anticancer therapy must have been administered within 6 months of thedate of randomization into this study.
• All anticancer- and radiation therapy-related toxicities must be completely resolvedor downgraded to Grade 1 or less (neuropathy may be Grade 2 or less).
• Have an Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1.
• Demonstrate adequate organ function obtained within 14 days prior to randomization andanalyzed by the central laboratory.
• Women of childbearing potential (WCBP) must agree to use highly effective methods ofbirth control throughout the duration of the study until 6 months following the lastdose of study drug.
• Males with female partners of child-bearing potential must agree to use a barriercontraception (e.g., condom with spermicidal foam/gel/film/cream/suppository)throughout the duration of the study until 6 months following the last dose of studydrug; in addition to their female partner using either an intrauterine device orhormonal contraception and continuing until 6 months following the last dose of studydrug. Male patients should not donate sperm until 6 months following the last dose ofstudy drug.

Exclusion Criteria:

• Last dose of anticancer therapy (including HER2-targeted therapy) within 14 days priorto randomization.
• High-dose chemotherapy followed by stem cell transplantation (autologous orallogeneic).
• Major surgery within 28 days prior to randomization.
• Concomitant use of any anticancer therapy or use of any investigational agent(s).
• Received prior treatment for cancer with a camptothecin-derived agent.
• Lesions on imaging, by cerebrospinal fluid or with neurological findings that areconsistent with leptomeningeal disease or meningeal carcinomatosis.
• Chronic or acute GI disorders resulting in diarrhea of any severity grade.
• Patients who are pregnant or lactating, plan to get pregnant, or have a positive serumpregnancy test prior to randomization.
• Enzyme-inducing anti-epileptic drugs (EIAEDs) within 14 days of randomization.
• Hepatitis B or C, tuberculosis, or HIV.
• Cirrhosis.
• Prior malignancy (other than breast cancer) unless diagnosed and definitively treatedmore than 5 years prior to randomization.
• Daily use of oxygen supplementation.
• Significant known cardiovascular impairment.
• Prior treatment with NKTR-102.
• Psychiatric illness, social situation, or geographical situation that precludeinformed consent or limit compliance.
• Known intolerance or hypersensitivity to any of the products used in this study ortheir excipients.
• For patients selecting vinorelbine or gemcitabine as the TPC agent, patients may notreceive yellow fever vaccine in the 28 days prior to randomization.