Dose Escalation of POL6326 in Combination With Eribulin in Patients With Metastatic Breast Cancer

Inclusion Criteria: * Histologically confirmed invasive cancer of the breast. * Presence of at least one measurable lesion per RECIST 1.1 criteria * Stage IV disease by AJCC criteria (7th edition). * HER2 negative (IHC 0,1 or FISH HER2:CEP17 ratio \< 2.0) * Must have had treatment with at least 2 but no more than 3 previous regimens in the metastatic setting. Previous treatment must have included an anthracycline and taxane in either the adjuvant or metastatic setting. * At least 21 days from the completion of any previous cytotoxic chemotherapy or biological therapy at time of initiation of POL6326. * ECOG performance status \< 2 Exclusion Criteria: * Previously received eribulin. * Peripheral neuropathy \> Grade 2. * Receipt of any other investigational agent within the 28 days prior to Day 1. * Receipt of colony stimulating factor filgrastim, pegfilgrastim, or sargramostim within 14 days prior to Day 1. * Radiation therapy within the 14 days prior to Day 1. * Severe concurrent illness or psychiatric illness/social situation that would limit compliance with study requirements. * History of other malignancy ≤ 5 years previous with the exception of basal cell or squamous cell carcinoma of the skin which were treated with local resection only or carcinoma in situ of the cervix. * Pregnant or breastfeeding. * Known HIV positivity on combination antiretroviral therapy; these patients are at increased risk of lethal infections when treated with marrow-suppressive therapy