ERBB2 and breast cancer: ERBB2-targeted therapy drugs approved by the Food and Drug Administration (FDA), including the monoclonal antibodies trastuzumab and pertuzumab, the small molecule ERBB1/2 tyrosine kinase inhibitor (TKI) lapatinib, neratinib, tucatinib and the antibody-drug conjugate trastuzumab emtansine (TDM1), have significantly improved outcomes for patients with ERBB2-positive breast cancer (Xu et al., 2017).