Pertuzumab

Human epidermal growth factor receptor-2 (HER2) is a tyrosine kinase receptor that plays an integral role in cell proliferation, differentiation, and survival. HER2 becomes active following dimerization with another HER2 receptor, another member of the HER protein family (e.g. HER3), or with a ligand - this dimer then phosphorylates and activates numerous intracellular signaling proteins, initiating signal transduction via pathways that include the Ras/mitogen-activated protein kinase pathway, the phosphatidylinositol 3' kinase (PI3K)/Akt pathway, and then Janus kinases/signal transducer and activator transcription pathway. HER2 is also a known oncogene - it is overexpressed or gene-amplified (i.e. HER2-positive) in approximately 20% of breast cancers and these cancers carry a generally poorer prognosis than HER2-negative breast cancers.

Pertuzumab targets the extracellular dimerization domain (subdomain II) of HER2, thereby inhibiting ligand-initiated intracellular signaling via the MAP kinase and PI3K pathways. Inhibition of these pathways results in inhibition of cell growth and the initiation of apoptosis, respectively. Pertuzumab also appears to mediate antibody-dependent cell-mediated cytotoxicity.