Lumretuzumab (Anti-Human ERBB3 Recombinant Antibody) is a humanized anti-HER3 (ERBB3) monoclonal antibody. Lumretuzumab effectively inhibits the activity of key oncogenic signaling pathways such as PI3K/AKT and MAPK. Lumretuzumab has been optimized through glycosyl engineering to enhance antibody-dependent cell-mediated cytotoxicity (ADCC). Lumretuzumab can be used to study HER3-positive, HER2-low-expressing solid tumors, especially breast cancer.