Inclusion Criteria:

• Histologically or cytologically proven diagnosis of breast adenocarcinoma that is now metastatic or locally recurrent and inoperable with curative intent.
• Prior treatment with a standard regimen of anthracycline and taxane.
• Female patients at least 18 years old.
• ECOG performance status (PS): 0-2
• Adequate organ and bone marrow function
• Measurable disease by Response Evaluation Criteria in Solid Tumors (RECIST) criteria (For the part I component, patients with non-measurable disease are accepted.)
• Resolution of all clinically significant toxic effects
• Completion of all prior therapy ≥ 3 weeks prior to registration. Patients on bisphosphonate therapy may continue such therapy.
• Patients must be either post-menopausal, surgically sterile, or using effective contraception.
• Willing and able to comply with study procedures and sign informed consent

Exclusion Criteria:

• History of any second malignancy within the last 5 years (except adequately treated basal cell or squamous cell skin cancer, or in situ carcinoma of the cervix uteri).
• Patients receiving more than one adjuvant regimen or more than one metastatic regimen
• Known brain or leptomeningeal disease.
• Concurrent treatment on another clinical trial or with any other cancer therapy including chemotherapy, biological therapy, hormonal therapy, radiotherapy, chemoembolization therapy, cryotherapy, targeted non-cytotoxic therapies, or patients planning to receive these treatments during the study.
• Prior treatment with capecitabine, XRP9881, or any investigational chemotherapy.
• History of hypersensitivity to taxanes, Polysorbate-80, or to compounds with similar chemical structures. Patients with known intolerance to fluoropyrimidines or patients with known dihydropyrimidine dehydrogenase (DPD) deficiency.
• Concurrent treatment with potent inhibitors of cytochrome P450 3A4, or patients planning to receive these treatments. For patients who were receiving treatment with such agents, a one-week washout period is required prior to registration.
• Peripheral neuropathy grade ≥ 2.
• Any of the following within the 6 months prior to registration: myocardial infarction, severe/unstable angina, coronary/peripheral artery bypass graft surgery, clinically symptomatic and uncontrolled cardiovascular disease, or clinically significant cardiac arrhythmias (grade 3-4).
• History of inflammatory bowel disease or chronic diarrhea.
• Lack of physical integrity of the upper gastrointestinal tract, malabsorption syndrome, or inability to take oral medication.
• Other severe acute or chronic medical or psychiatric condition, or significant laboratory abnormality requiring further investigation or that may cause undue risk for the patient's safety.
• Known human immunodeficiency virus (HIV) infection requiring treatment or acquired immunodeficiency-syndrome (AIDS)-related illness.
• Patients who are pregnant or breastfeeding.