This study will examine whether the investigational drug EPO906, given by intravenous infusion (IV directly into the vein), is effective in shrinking tumors and preventing the growth of cells that cause breast cancer.

Inclusion Criteria:

The following patients may be eligible for this study:

• Histologically or cytologically documented evidence of disease with at least one measurable lesion;
• Life expectancy of greater than three (3) months;
• Patients who have had only one prior therapy for metastatic disease;
• Patients who have received prior treatment with hormonal agents or who have had prior treatment regimens of radiotherapy in addition to one or no previous chemotherapy regimens are eligible;
• Patients who have had no prior therapy for metastatic disease, but who have received a taxane and an anthracycline (single or combination therapy) as adjuvant treatment, are eligible. For patients who have had previous radiation therapy to the target lesion(s), the lesion(s) must since have demonstrated progression.

Exclusion Criteria:

The following patients are not eligible for this study:

• Bone-only disease;
• Symptomatic pleural effusions;
• Symptomatic CNS metastases or leptomeningeal involvement;
• Any peripheral neuropathy or unresolved diarrhea greater than Grade 1;
• Severe cardiac insufficiency;
• Patients taking Coumadin or other warfarin-containing agents with the exception of low dose Coumadin (1 mg or less) for the maintenance of in-dwelling lines or ports;
• History of another malignancy within 5 years prior to study entry except curatively treated non-melanoma ckin cancer or cervical cancer in situ;
• Active or suspected acute or chronic uncontrolled infection including abcesses or fistulae;
• HIV+ patients;
• Pregnant or lactating females;
• Patients who have had radiation, chemotherapy, or hormonal therapy within the last four (4) weeks excluding palliative radiotherapy to isolated peripheral bone metastases not being used as markers for efficacy;
• Patients taking Herceptin less than three (3) weeks prior to study start.