This oral agent was initially approved in anthracycline and taxane-resistant breast cancer and subsequently approved for use in combination with docetaxel as second-line therapy in metastatic BC, or in combination with small-molecule lapatinib in women with human epidermal growth factor receptor type 2 (HER2)-positive metastatic BC, following progression on trastuzumab-based therapy [31,32]. Here, ERBB2 is linked to breast cancer.