Pertuzumab (Perjeta®) is a dual HER2/HER3 mAb that was approved by the FDA in 2012 in combination with trastuzumab and docetaxel for first-line treatment of HER2+ metastatic BC as it increased OS, according to the results obtained in the Cleopatra trial (NCT00567190) [95,105]. The gene discussed is ERBB2; the disease is breast cancer.