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

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.