In Part 1, the dose of poziotinib, in combination with the standard dose of T-DM1 (3.6 mg/kg IV) on Day 1 of each cycle will be determined using a 3+3 design with up to 3 dose levels tested beginning with 8 mg/day.~Poziotinib dose escalation/de-escalation for the next dose cohort will proceed based on the occurrence of dose-limiting toxicities (DLTs) during Cycle 1 of the dose cohort. Patients in the dose cohort, if not discontinued, will continue treatment until discontinuation.~In Part 2 of the study, approximately 10 patients will be treated at the MTD/MAD to confirm dose for safety of the combination and to evaluate preliminary efficacy. Treatment for all patients will continue until disease progression, unacceptable toxicity, or continuation of study treatment is not in the best interest of the patient.~The Screening period (Day -30 to Day -1) will last up to 30 days prior to Cycle 1, Day 1.~During each 21-day cycle, eligible patients will receive poziotinib at the assigned dose, orally, once daily. T-DM1 3.6 mg/kg IV will be administered on Day 1 of each treatment cycle.~All treated patients will be followed for response until disease progression or the start of new treatment and then for survival (3 year study duration).
This is a Phase 1b, open-label, multicenter study to determine the Maximum Tolerated Dose (MTD) or Maximum Administered Dose (MAD) of poziotinib when administered with standard dosing of T-DM1 (3.6 mg/kg IV on Day 1 of each 21-day cycle) in women with advanced or metastatic HER2+ breast cancer. The poziotinib dose identified in Part 1 of the study will be used in combination with standard dose of T-DM1 in Part 2 of the study to confirm the poziotinib dose and evaluate the preliminary efficacy of the combination therapy.