Orteronel as Monotherapy in Patients With Metastatic Breast Cancer (MBC) That Expresses the Androgen Receptor (AR)

The androgen receptor (AR) is expressed in 70-90 percent of primary breast tumors and in 75 percent of breast metastases. There is evidence to suggest that Androgen Receptor (AR) may be a target in patients with advanced breast cancer. Breast cancer patients whose tumors do not express the ER, PR or HER2 (triple negative) have very few options for treatment. Orteronel is being developed as an endocrine therapy for relevant hormone-sensitive cancers such as prostrate cancer and breast cancer. Triple-negative metastatic breast cancer patients with AR expression could potentially benefit from anti-androgen therapy like orteronel.

This open-label multicenter study will be conducted in 2 stages. * Lead-in Phase: The first 6 patients treated will be evaluated to confirm the safety and feasibility of this regimen. After all 6 patients complete at least 4 weeks of treatment, and if no prohibitive toxicities are identified, continuous study treatment will begin. * Continuous Study Treatment: Patients will continue to be enrolled into both cohorts based on their tumor specificities with an anticipated total of 31 patients in Cohort 1 (ER-/PR-/HER2-/AR+) and an anticipated total of 55 patients in Cohort 2 (ER+ and/or PR+/AR+). Patients will be evaluated every eight weeks for response to treatment. All patients who respond to treatment (complete response \[CR\] or partial response \[PR\]) or have stable disease (SD) will continue to receive orteronel until they develop progressive disease (PD) or unacceptable toxicity.