This clinical study is designed as an open, single group, multi-center, phase 4 clinical study to assess the safety of eribulin which is approved for the treatment of the patients in Korea with locally advanced or metastatic breast cancer who had received two to five prior chemotherapy regimens including anthracyclines and taxanes for advanced disease.

Subjects who meet the inclusion/exclusion criteria are administered of 1.4 mg/m2 of the investigational product intravenously in 2-5 min on day 1 and day 8 of every 21-day cycle. In case of the progression of disease, unacceptable toxicity, withdrawal of the consent, or judgment by investigator that the treatment needs to be stopped, the treatment of investigational product is stopped, and treatment termination assessment is performed within 30 days from the last treatment.

Inclusion Criteria:

1. Female, Age greater or equal to 20 years

2. Patients with histologically or cytologically confirmed carcinoma of the breast

3. Patients with locally advance or metastatic carcinoma of the breast

4. Patients who have received two to five prior chemotherapeutic regimens including an antracycline and a taxane and 2 or more regimens for locally recurrent and/or metastatic disease

5. Patients must have proved refractory to the most recent chemotherapy on or within six (6) months of therapy

6. Patients who have assessable lesion according to RECIST v 1.1

7. Adequately maintained bone marrow function

   • absolute neutrophil count (ANC) greater than or equal to 1.5 x 10^9 /L
   • hemoglobin greater than or equal to 10.0 g/dl (a hemoglobin less than 10.0 g/dL is acceptable if it is corrected by erythropoietin or transfusion)
   • Platelet count greater than or equal to 100 x 10^9 /L

8. Adequately maintained liver function

   • Total bilirubin: less than or equal to 1.5 times the upper limits of normal (ULN) and
   • Alkaline phosphatase(ALP), alanine aminotransferase (ALT), and aspartate aminotransferase (AST) less than or equal to 3 x ULN (in the case of liver metastases less than or equal to 5 x ULN)

9. Adequately maintained renal function

   • Serum creatinine less than or equal to 2.0 mg/dl or
   • Calculated creatinine clearance greater than or equal to 40 ml/min (Cockcroft and Gault formula)

10. Resolution of all chemotherapy or radiation-related toxicities to Grade 1 severity or lower, except for

    • alopecia
    • stable sensory neuropathy less than or equal to Grade 2

11. Eastern Cooperative Oncology Group (ECOG) Performance Status of 0 to 2

12. Life expectancy of greater than or equal to 3 months

13. Patients willing and able to comply with the study protocol for the duration of the study

14. Patients who have provided written consent to participate in this study

Exclusion Criteria

1. Patients who have received a chemotherapy, radiation, biologics, immunotherapy or hormonal therapy within three weeks before treatment start (but, palliative radiation can be enrolled)

2. Pulmonary lymphangitic involvement that results in pulmonary dysfunction requiring active treatment, including the use of oxygen

3. Patients with brain or subdural metastases are not eligible, unless they have completed local therapy and have discontinued the use of corticosteroids for this indication for at least four weeks before starting treatment in this study. Any signs and/or symptoms of brain metastases must be stable for at least four weeks before starting study treatment

4. Patients with meningeal carcinomatosis

5. Significant cardiovascular impairment

   • Myocardial infarction within the past six months, unstable angina, history of congestive heart failure NYHA class III or IV, or serious cardiac arrhythmia
   • QTc prolongation (Bazett's Formula greater than 480 msec) or congenital long QT syndrome

6. Severe/uncontrolled intercurrent illness/infection required administration of antibiotic injection

7. Patients who have processed a major surgery within four weeks before participation in this clinical trial

8. Patients who have had a prior malignancy within the past five years other than breast cancer (but, treated non-melanoma skin cancer and carcinoma in situ of the cervix will not be excluded)

9. Patients with known positive HIV status

10. Patients who have received genetic therapy or other investigational drug within 4 weeks before treatment start or expected to receive prohibited medication

11. Patients with prior allergies to Halichondrin B, its derivatives, active ingredient, or other diluting agent

12. Patients who have received this investigational product before registration for this study

13. Patients who are pregnant, who may possibly be pregnant, or are lactating

14. Patients who do not agree to practice contraception for the study periods

15. Patients who have participated in other clinical trial within 4 weeks before screening

16. Patients otherwise judged by investigator or sub investigator to be unsuitable for inclusion