Prior treatment\r\n* No more than two prior chemotherapy regimens in the metastatic setting\r\n* Prior treatment with fulvestrant in the metastatic setting is required, except for patients with a history of ER-negative metastatic breast cancer\r\n* Unlimited prior endocrine therapy regimens in the metastatic setting are allowed\r\n* No prior treatment with an aurora Kinase inhibitor (either an aurora A or pan-aurora kinase inhibitor) Patients who have received prior administration of an Aurora A kinase targeted agent (including alisertib) are not eligible Prior administration of an aurora A kinase-targeted agent, including alisertib Any prior treatment with an aurora kinase inhibitor (either an aurora A kinase or pan-aurora kinase inhibitor) Prior treatment with Aurora A-targeted agents, including MLN Prior treatment with irinotecan or aurora A-targeted agents, including MLN Patient must not have received any previous treatment with any aurora-kinase inhibitors (MTD expansion cohort only) Prior administration of an aurora A kinase-targeted agent, including alisertib No prior Aurora kinase inhibitor Patients may not have received prior therapy with an Aurora kinase inhibitor Prior administration of an aurora A kinase-targeted agent, including alisertib