The purpose of this study is to evaluate whether treatment with a new drug called ZK-Epothilone (ZK-Epo) in patients with metastatic breast cancer helps to decrease or stop tumor growth.

This study has previously been registered by Berlex, Inc. Berlex, Inc. has been renamed to Bayer HealthCare Pharmaceuticals, Inc.Bayer HealthCare Pharmaceuticals, Inc.is the sponsor of this study.

Inclusion Criteria:

• Metastatic breast cancer (meaning the cancer has spread beyond its original location)
• At least one measurable lesion by CT or MRI
• Progression of disease following previous therapy for breast cancer
• Have received previous treatment with anthracyclines (e.g. doxorubicin[Adriamycin or Doxil] or epirubicin [Ellence]), taxanes (paclitaxel [Taxol or Abraxane] or docetaxel [taxotere]) for your breast cancer
• Not be pregnant
• Additional criteria to be determined at screening visit.

Exclusion Criteria:

• More than 3 previous chemotherapy regimens
• More than one treatment with non cytotoxic agents for breast cancer therapy (e.g. herceptin [trastuzumab] or Avastin [bevacizumab)
• Prior treatment with epothilones (e.g. Ixabepilone)
• Symptomatic brain metastases
• Additional criteria to be determined at screening visit](streamdown:incomplete-link)