Efficacy of sacituzumab govitecan (anti-Trop-2-SN-38 antibody-drug conjugate) for treatment-refractory hormone-receptor positive (HR+)/HER2- metastatic breast cancer (mBC).

1004Background: Sacituzumab govitecan is a novel antibody-drug conjugate consisting of SN-38, the active metabolite of irinotecan, conjugated to a humanized mAb targeting Trop-2 (trophoblastic antigen-2), which is highly expressed in many epithelial cancers. A phase I/II basket trial (NCT01631552) investigated its activity in patients (pts) with advanced cancers, and we previously reported on pts with triple-negative mBC. Results in HR+/ HER2 negative (as per ASCO/CAP guidelines) mBC pts who had ≥ 1 prior hormonal therapy are presented here. Methods: Pts received sacituzumab govitecan at a dose of 10 mg/kg on days 1 & 8 of a 21-day cycle until progression or unacceptable toxicity. Eligibility included ≥ 1 prior line of standard therapy for metastatic disease, measurable disease by CT or MRI. Efficacy was assessed locally by RECIST 1.1. Adverse events (AE) were evaluated according to CTCAE v4.0, Results: Fifty-four pts with HR+/HER2- mBC (all female; median age 54 yrs, range 33-79) were accrued between 2/2...