Trastuzumab-emtansine (TDM-1), a second-generation ADC, was first approved by the FDA in 2013 for HER2-positive metastatic BC (in second- and third-line settings, following the failure of trastuzumab and taxane), and subsequently, in 2019 it was approved in the adjuvant setting for early-stage HER2-positive BC with residual invasive disease after neoadjuvant treatment [34]. Here, ERBB2 is linked to breast cancer.