Open Label Trial of INCB07839 to Determine Effect and Safety of INCB007839 Plus Trastuzumab in HER2 Positive Metastatic Breast Cancer

Inclusion Criteria: * Histologically or cytologically confirmed metastatic breast carcinoma that is HER2 positive * Measurable disease as defined by the RECIST criteria * Life expectancy greater than or equal to 6 months * Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1 Exclusion Criteria: * Received any anticancer medications in the 28 days prior to enrollment into this study * Received any anticancer medications for cancers other than breast cancer within 6 months prior to enrollment in this study. * History of deep venous thrombosis within the last year * Contraindication to low dose warfarin therapy * Clinically significant cardiomyopathy * Prior treatment with INCB007839 or trastuzumab or lapatinib