Advancing outcomes of metastatic HER2-positive breast cancer

HER2 is a cell surface protein overexpressed in approximately 15–20% of patients with breast cancer.1 Conventionally, monoclonal antibodies and small-molecule tyrosine kinase inhibitors have been used to target HER2. In the past 10 years, multiple antibody–drug conjugates have emerged for the treatment of haematological and solid malignancies.2 Trastuzumab deruxtecan is a second-generation antibody-drug conjugate with an antibody backbone with a similar amino acid sequence as trastuzumab, and a topoisomerase I inhibitor payload conjugated to a tetrapeptide-based cleavable linker.