An Open-Label, Multicenter, Single Arm Phase II Study of Oral GW572016 as Single Agent Therapy in Subjects With Advanced or Metastatic Breast Cancer Who Have Progressed While Receiving Herceptin Containing Regimens

Inclusion Criteria:

(The patient must meet the following criteria in order to be eligible
for this study.)

- Signed informed consent

- No more than two prior regimens for metastatic breast cancer. Each regimen must have
contained Herceptin.

- Refractory Stage IIIb or IV breast cancer

- HER2/neu tumor overexpression

- Disease progression while receiving a prior chemotherapy regimen with Herceptin alone
or in combination with other chemotherapy.

- Tumor tissue available for testing.

- 2 weeks since treatment with Herceptin (alone or in combination).

- Able to swallow and retain oral medication

- Cardiac ejection fraction within the institutional range of normal as measured by
MUGA (Multiple Gated Acquisition Scan).

- Adequate kidney and liver function

- Adequate bone marrow function

Exclusion Criteria: (The patient cannot meet any of the following criteria in order to be
eligible for this study.)

- Prior regimens did not include Herceptin.

- Pregnant or lactating.

- Conditions that would affect absorption of an oral drug

- Serious medical or psychiatric disorder that would interfere with the patient's
safety or informed consent.

- Severe cardiovascular disease or cardiac disease requiring a device.

- Active infection.

- Brain metastases.

- Concurrent cancer therapy or investigational therapy.

- Use of oral or IV steroids.

- Unresolved or unstable serious toxicity from prior therapy.

- Treatment with EGFR (Endothelial Growth Factor Receptor) inhibitor other than
Herceptin.