Phase 1b Study of PD-0332991 in Combination With T-DM1(Trastuzumab-DM1)

Standard of care: Treatment with Trastuzumab Experimental: 21-Day Cycle of Combination therapy with T-DM1 intravenously on Day 1 and oral PD-0332991 on Days 5-18 Study Design and Methodology: This is a phase 1B inter-patient dose escalation study of PD-0332991 in combination with T-DM1 in patients with recurrent or metastatic HER2-positive breast cancer after prior trastuzumab or other HER2-directed therapies. The subjects will be administered T-DM1 by intravenous infusion at 3.6 mg/kg for 90 minutes on day 1 of each 21 day cycle. Infusion timing may vary from 30-90 minutes depending on how well the subject tolerates the treatment. A standard 3+3 trial design will be used for PD-0332991 dose escalation cohorts.The dosing of PD-0332991 will be divided into 3 cohorts, the subjects will receive PD-0332991 on days 5-18 of each 21 day cycle. Cohort 1 : PD-0332991 - 100 mg daily (oral) Cohort 2 : PD-0332991 - 150 mg daily (oral) Cohort 3 : PD-0332991 - 200 mg daily (oral) The 3+3 design entails that if one patient out of the first three patients has a DLT, up to three additional patients will be entered at that dose level Treatment cycles will continue until disease progression or withdrawal from study.