A Study of Single-Agent Eribulin Mesylate as First-Line Therapy for Locally Recurrent or Metastatic Human Epidermal Growth Factor Receptor Two (HER2) Negative Breast Cancer

Key Inclusion Criteria Females age 18 years or older at the time of informed consent Have histologically or cytologically proven adenocarcinoma of the breast Subjects with locally recurrent or metastatic disease with at least one measurable lesion according to Response Evaluation Criteria in Solid Tumors (RECIST) criteria v 1.1 Human epidermal growth factor receptor (HER2)-negative disease as determined by fluorescence in situ hybridization (FISH) or 0 or 1+ by immunohistochemical (IHC) staining. Life expectancy of greater than 24 weeks Eastern Cooperative Oncology Group (ECOG) Performance Score (PS) of 0, 1 or 2 At least 12 months since prior neoadjuvant or adjuvant chemotherapy At least 2 weeks since prior radiotherapy or endocrine therapy, with complete recovery from the effects of these interventions Adequate renal function Adequate bone marrow function Adequate liver function Key Exclusion Criteria Subjects who meet any of the following criteria will be excluded from participation in this study: Prior chemotherapy, biologic therapy, or investigational therapy for locally recurrent or metastatic breast cancer Subjects who have had a prior malignancy other than carcinoma in situ of the cervix or nonmelanoma skin cancer Prior exposure of greater than 360 mg/m2 doxorubicin or liposomal doxorubicin, greater than 120 mg/m2 mitoxantrone, greater than 90 mg/m2 idarubicin, or greater than720 mg/m2 epirubicin Inflammatory breast cancer Clinically significant cardiovascular impairment Subjects with known CNS disease are not eligible, except for those with treated brain metastasis. Pulmonary lymphangitic involvement that results in pulmonary dysfunction requiring the use of oxygen Currently pregnant or breast-feeding. Subjects with pre-existing Grade 3 or 4 neuropathy. Any peripheral neuropathy must recover to Grade 2 before enrollment.