U3-1302 is an antibody drug conjugate comprising a recombinant fully human anti HER3 monoclonal antibody linked to a linker containing topoisomerase I inhibitor. This study is a phase II study of U3-1402 in subjects with MBC who have received no prior anti HER2 therapy. The study will be conducted in 3 parts (Part A, Part B, and Part Z). All enrolled subjects in part A will undergo pretreatment biopsies to determine if subjects with particular biomarker expression (ER/PR/HER2/HER3) show preliminary efficacy after an analysis is performed at 24 weeks. Part B will enroll subgroups of subjects that will be defined from part A based on ER/PR/HER2/HER3 expression and will be evaluated for efficacy analysis. Part Z will enroll additional 21 subjects with HER2+ MBC.
This study is to evaluate safety and efficacy of an antibody drug conjugate U3-1402 in patients with locally advanced or metastatic breast cancer (MBC).