A phase II study of eribulin mesylate in combination with trastuzumab and pertuzumab in patients (pts) with human epidermal growth factor receptor 2-positive (HER2+) metastatic breast cancer (MBC).

1034Background: As a single agent, eribulin is an active agent among MBC pts. In the first-line setting, pertuzumab improves progression free and overall survival when added to trastuzumab and chemotherapy (CT); however there are limited data in the second line or beyond. The primary aim of this study was to evaluate the activity of eribulin in combination with trastuzumab and pertuzumab in pts with HER2+ MBC whose cancers are refractory to trastuzumab containing regimens. Safety and toxicity were examined and correlative studies are also planned. Methods: Single center, single-arm, phase II, 2 cohorts study planned to enroll up to 81 pts. The studied combination would be of clinical interest if the true overall response rate (ORR) was 40% among those without prior pertuzumab exposure (Cohort A) and 30% among those with prior pertuzumab exposure (Cohort B). The trial was stopped prematurely due to low accrual. Prior to the start of the phase II study, a run-in established dose of eribulin with standard do...