Ventana Medical Systems Inc., of Tucson, Ariz., a member of the Roche Group, said the Ventana HER2/neu (4B5) Rabbit Monoclonal Primary Antibody assay is available as a companion diagnostic for detecting HER2 protein expression in patients who may be candidates for Perjeta (pertuzumab) and Kadcyla (ado-trastuzumab emtansine).