9F7-F11

**9F7-F11** is a monoclonal antibody targeting the human epidermal growth factor receptor 3 (**HER3**, also known as **ErbB3**). It is a non-competing, neuregulin (NRG1)-non-competitive antibody, meaning it binds HER3 at a site distinct from the NRG1 ligand-binding site, and its binding is allosterically enhanced by the presence of NRG1. 9F7-F11 induces rapid ubiquitination and proteasomal degradation of HER3 via activation of the E3 ubiquitin ligase ITCH/AIP4, which is JNK1/2-dependent and stabilized by deubiquitinases USP8 and USP9X. This mechanism leads to down-regulation of HER3, inhibition of the PI3K/AKT signaling pathway, cell cycle arrest, and induction of apoptosis. In preclinical models, 9F7-F11 demonstrates significant anti-tumor activity, notably in NRG1-positive and HER3-dependent cancers such as pancreatic, breast, and prostate tumors, resulting in tumor growth inhibition and regression. Further pro-apoptotic effects involve extrinsic (TRAIL-R2/DR5 upregulation and caspase-8 activation) and intrinsic (caspase-9/3, BAX/BIM upregulation) apoptotic pathways. The antibody has not yet entered clinical trials and remains in the preclinical stage of development[1][2][3][4].