The HER2-targeting antibody-drug conjugate (vic-)trastuzumab duocarmazine (SYD985) showed promising clinical activity in heavily-pretreated women with metastatic breast cancer, according to results from a phase I expansion cohort presented at the 2018 ASCO Annual Meeting.
The objective response rate (ORR) was 33% (16/48) among evaluable patients with HER2-positive disease, including 29% (11/38), among those who had prior T-DM1 (ado-trastuzumab emtansine; Kadcyla). The ORR was 27% (8/30) among evaluable patients with HER2-low/hormone receptor (HR)-positive disease, and 40% (6/15) for those with triple-negative disease. All responses across these subgroups were partial responses.
The median progression-free survival (PFS) was 9.4 months (95% CI, 4.5-12.4) overall in the HER2-positive group, and 8.3 months (95% CI, 4.1-15.0) among those in the group with prior T-DM1. The median PFS was 4.1 months (95% CI, 2.4-5.4) and 4.4 months (95% CI, 1.0-7.1) in the HER2-low/HR-positive and triple-negative arms, respectively.
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