This is a Phase II, open label, single arm, multicenter study of NK012 in patients with locally advanced non-resectable and metastatic breast cancer with ER-negative, PR negative and HER2-negative phenotype. NK012 will be administered by infusion over 30 minutes once every 28 days (on Day 1 of each cycle). Patients will be screened for UGT1A1 polymorphism prior to enrollment in order to determine their starting dose.