Progression-free survival was modestly improved with margetuximab.
HER2-directed therapies, starting with trastuzumab, have significantly improved outcomes for patients with HER2+ (ERBB2-amplified) metastatic breast cancer. Recent additions include antibody-drug conjugates, tyrosine kinase inhibitors, and other HER2 antibodies. Median overall survival (OS) is now approaching 5 years (Lancet Oncol 2020; 21:519). Margetuximab is a chimeric immunoglobulin G1 (IgG1) monoclonal antibody designed to increase antibody-dependent cell-mediated cytotoxicity (ADCC), a mechanism of trastuzumab activity. Margetuximab shares HER2 epitope specificity with trastuzumab but has an engineered Fc region designed to increase affinity for activating Fcγ receptor CD16A and decrease affinity for inhibitory Fcγ receptor CD32B. Pol…