Inclusion Criteria:

• Signed Informed Consent.
• Histologically confirmed Stage IIIb or IV breast cancer.
• Refractory breast cancer defined as progression in the metastatic setting after prior therapy with anthracyclines, taxanes and capecitibine.
• Subjects with documented ErbB2 tumor overexpression must have received at least 6 cycles of trastuzumab.
• Documented disease progression of the most recent treatment is required.
• Archived tumor tissue available for testing.
• Measurable lesions according to Response Evaluation Criteria In Solid Tumors (RECIST).
• At least 3 weeks since prior cancer therapies except for trastuzumab which must be discontinued at least 2 weeks prior to the beginning of study drug.
• Bisphosphonate therapy initiated prior to study entry is allowed, however, initiation of bisphosphonates following study entry is not allowed.
• Able to swallow and retain oral medication.
• Cardiac ejection fraction within the institutional normal range as measured by echocardiogram or MUGA (Multiple Gated Acquisition) scan.
• Adequate kidney and liver function.
• Adequate bone marrow function.

Exclusion criteria:

• Pregnant or lactating.
• Copies of nadir scans and/or photographs of the tumor prior to disease progression as well as scans documenting disease progression are not available for review.
• Malabsorption syndrome, ulcerative colitis, disease significantly affecting gastrointestinal function or resection of the stomach or small bowel.
• History of other malignancy.
• Serious medical or psychiatric disorder that would interfere with the patient''s safety or informed consent.
• Active or uncontrolled infection.
• Known history of uncontrolled or symptomatic angina, arrhythmias or congestive heart failure.
• Known history of or clinical evidence of leptomeningeal carcinomatosis.
• Active infection.
• Concurrent cancer therapy or investigational therapy.
• Use of oral or IV steroids.
• Unresolved or unstable serious toxicity from prior therapy.
• Prior treatment with an ErbB1 and/or ERbB2 inhibitor other than trastuzumab.