A Multicenter Phase II Clinical Trial of PM01183 in BRCA 1/2-Associated or Unselected Metastatic Breast Cancer to assess the antitumor activity of PM01183 in terms of overall response rate (ORR), duration of response (DR),clinical benefit [ORR or stable disease lasting over three months (SD > 3 months)], progression free survival (PFS), and one-year overall survival (1y-OS) and to evaluate whether the presence of a known germline mutation in BRCA 1/2 predicts response to PM01183 in MBC patients, to explore the activity of PM01183 in specific breast cancer subpopulations according to hormonal receptor status, HER-2 overexpression, number and/or type of prior therapies, or according to other available histological/molecular classifications, to evaluate the safety profile of this PM01183 administration schedule [Day 1 every three weeks (q3wk)] in this patient population, to analyze the pharmacokinetics (PK) of PM01183 in this patient population, to explore PK/PD (pharmacokinetic/ pharmacodynamic) correlations, if applicable and to evaluate the pharmacogenomic (PGx) expression profile of selected putative markers potentially predictive of response to PM01183, in tissues from tumor samples.