ERBB2 and breast cancer: T-DM1 (Kadcyla®), an ADC comprising trastuzumab and the tubulin inhibitor emtansine, which achieves significantly longer median overall survival (OS) and progression-free survival (PFS) in EMILIA (Verma et al., 2012) and TH3RESA (Krop et al., 2017) trials, has been approved for the treatment of HER2-positive metastatic BC patients who previously received trastuzumab.