This is a humanized IgG1 monoclonal antibody using the same sequences as the therapeutic antibody pertuzumab. It targets the extracellular dimerization domain (subdomain II) of HER2, a receptor tyrosine kinase, in order to prevent the formation of HER2/HER3 dimer. Pertuzumab has been approved for use in combination with docetaxel and trastuzumab, in the treatment of metastatic HER2-positive breast cancer. It inhibits ligand-initiated intracellular signaling via the MAP kinase and PI3K pathways. Inhibition of these pathways results in suppression of cell growth and the initiation of apoptosis, respectively. Additionally, pertuzumab appears to facilitate antibody-dependent cell-mediated cytotoxicity.