AFP464 is an investigational agent which may be effective in the treatment of cancer. The purpose of this study is to test the efficacy of AFP464 +/- Faslodex in ER+ breast cancer patients.

This is a randomized, open-label study. Patients will be randomized in a 1:1 ratio to single arm AFP464, or AFP464+Faslodex. Patients will be treated until disease progression is noted.

Inclusion Criteria:

• proven breast cancer, ER+ status; progression on an aromatase inhibitor; measurable disease or evaluable disease with serum CA27.29>=50 U/mL; adequate bone marrow, liver and renal function; DLco grade 0 or 1.

Exclusion Criteria:

• HER2 positive, thoracic radiotherapy or symptomatic pulmonary disease, brain metastases,