Slow recruitment rate

Unresectable, ER-positive and/or PR-positive and HER2-negative locally-recurrent or metastatic breast cancer (mBC).

Pre- and post-menopausal women age ≥ 18 years with unresectable, ER-positive and/or PR-positive and HER2-negative locally-recurrent or metastatic breast cancer (mBC) with no prior line of chemotherapy in the metastatic setting, and that have shown progression while on an aromatase inhibitor-containing regimen in the metastatic setting or within six months from last aromatase inhibitor dose in the adjuvant setting. Patients must have received at least one taxane or anthracycline regimen in either the adjuvant or the neoadjuvant setting. Subjects must have adequate bone marrow and creatinine clearance functions.

Inclusion Criteria:

• ER-positive and/or PR-positive breast cancer.
• HER2-negative breast cancer.
• Unresectable locally advanced or metastatic breast cancer.
• Confirmed disease progression while in the last aromatase inhibition-containing regimen in the metastatic setting.
• At least one taxane or anthracycline regimen in either the adjuvant or the neoadjuvant setting.
• Patients with no prior line of chemotherapy in the metastatic setting.
• At least 1 and up to 3 prior lines of endocrine therapy in the metastatic setting.
• ECOG score 0 or 1.
• Patients have adequate bone marrow and organ function.
• Patients must have measurable disease (RECIST v.1.1).
• Premenopausal with LHRH analogues for at least 28 days) and postmenopausal women.
• Patients must agree to not breastfeed during the study and for 3 months after the last dose of study treatment.
• Life expectancy greater or equal to 12 weeks.
• Patients agree to collection of blood samples (liquid biopsy) and optional collection of metastatic tumour sample (biopsy) at the time of inclusion and progression (if appropriate).

Exclusion Criteria:

• Have received radiation therapy or limited-field palliative radiotherapy within two weeks prior to Cycle 1, Day 1, or patients who have not recovered from radiotherapy-related toxicities.
• Have received prior chemotherapy for locally advanced or metastatic disease.
• Have peripheral neuropathy grade 2 or greater.
• QTc > 480 msec on basal assessments, history of congenital or personal history of long QT syndrome, Brugada syndrome, or Torsade de Pointes (TdP), or uncontrolled electrolyte disorders
• Child-bearing potential women not using highly effective methods of contraception.
• Known hypersensitivity to eribulin, endocrine therapy or its excipients.
• Other malignancies within the previous two years except adequately treated basal cell or squamous cell skin cancer or carcinoma in situ of cervix or breast.
• Known uncontrolled metastases to the central nervous system (CNS) or any progressing CNS disease.
• Have a serious concomitant systemic disorder incompatible with the study.
• Major surgical procedure or significant traumatic injury within 28 days prior to randomization.
• Have received any anti-cancer biology or investigational treatment within 30 days prior to randomization.