Patients with breast cancer must have had at least one prior chemotherapy regimen for metastatic disease. Additionally, patients with breast cancer must have received prior tamoxifen and/or aromatase inhibitor therapy (if postmenopausal) with at least one hormonal regimen in the metastatic setting. Patients with HER2+ breast cancer must have progressed after at least one prior HER2-directed regimen (trastuzumab, lapatinib) for metastatic disease.