A phase II study of HER3-DXD in patients (pts) with metastatic breast cancer (MBC)

HER3, a member of the HER receptor tyrosine kinase (RTK) family, is overexpressed in many solid tumors including breast cancer (BC), and this overexpression is associated with decreased survival. HER3 lacks intrinsic kinase activity and forms heterodimers with other RTKs, most notably HER2, and subsequent downstream signaling promotes tumorigenesis and metastasis. HER3-DXd is an antibody drug conjugate (ADC) comprised of a fully human anti-HER3 IgG1 monoclonal antibody (patritumab), covalently linked to a topoisomerase 1 inhibitor payload, an exatecan derivative (DXd), via a tetrapeptide-based cleavable linker.