Anti-Human/Rhesus monkey ERBB3 Monoclonal Antibody (Lumretuzumab)

ERBB3 (also known as HER3) is a functionally unique member of the epidermal growth factor receptor (EGFR/ERBB) family, characterized most notably by critical amino acid mutations in its intracellular tyrosine kinase domain that render it virtually catalytically inactive. Therefore, ERBB3 must function by forming heterodimers with other catalytically active members of the family, particularly ERBB2/HER2. Upon stimulation by ligands such as neuregulins, multiple tyrosine residues in its cytoplasmic tail are phosphorylated by its dimerization partner, thereby potently activating key pro-survival and pro-proliferative signaling pathways, most notably the PI3K/AKT and RAS/MAPK cascades. By virtue of this unique signal-amplifying capability, ERBB3 plays a critical role in various solid tumors (including breast, lung, and ovarian cancers), where its overexpression is not only associated with tumorigenesis and disease progression but also constitutes one of the core mechanisms driving therapeutic resistance—when EGFR or HER2 is inhibited by targeted drugs, tumor cells often "find an alternative route" by upregulating ERBB3 or its ligands to restore downstream survival signaling and evade treatment. Given its central role in oncogenesis and drug resistance, ERBB3-targeted therapeutics—including monoclonal antibodies, bispecific antibodies, and antibody-drug conjugates—are being actively developed to overcome resistance challenges in cancer therapy.