Trastuzumab and pertuzumab are recombinant humanized anti-HER2 monoclonal antibodies bind to extracellular domain IV (ECD IV) and domain II (ECD II) of HER2, respectively, interfere the formation of heterodimerization of other ErbB members, block downstream signaling pathways and inhibit cancer cell proliferation. The gene discussed is ERBB2; the disease is cancer.