Trastuzumab (Herceptin®; Genentech Inc, South San Francisco, CA), is a recombinant, DNA derived, humanized, anti-Her-2 monoclonal antibody which selectively targets subdomain IV of the extracellular domain over expressed Her-2 receptors and is licensed as a therapy for Her-2 positive breast cancer. The gene discussed is ERBB2; the disease is breast carcinoma.