Inclusion Criteria

Major Eligibility Criteria:

1. Female sex.

2. Age ≥18 years.

3. Body weight 40-100 kg.

4. ECOG performance status of 0 or 1.

5. Histologically or cytologically confirmed adenocarcinoma of the breast.

6. Presence of metastatic disease not amenable to surgery, radiation therapy, or
chemoradiotherapy with curative intent.

7. No active second metastatic malignancy other than breast cancer.

8. No unstable brain or leptomeningeal disease.

9. Discontinuation of other therapies (except for anastrozole, letrozole, or exemestane)
for the treatment of breast cancer and resolution of any acute toxic effects of prior
therapies.

10. Adequate bone marrow, liver, and kidney function.

11. No uncontrolled hypertension, major bleeding, HIV infection or recent acute
cardiovascular event.

12. If sexually active and not postmenopausal or surgically sterile, willingness to
abstain from sexual intercourse or employ an effective barrier method of
contraception during the study drug administration and follow-up periods.

13. No pregnancy or breast-feeding.

14. Willingness and ability to comply with scheduled visits, drug administration plan,
laboratory tests, other study procedures, and study restrictions.

15. Willingness to provide informed consent. In addition to the criteria noted above,
Stage 2 subjects must also have natural or induced suppression of ovarian function to
post-menopausal levels and be receiving or be a candidate for hormonal therapy.