ERBB2 and breast cancer: Composed of the anti-HER2 antibody trastuzumab linked to the microtubule inhibitor emtansine (DM1) via a non-cleavable linker, T-DM1 was the first ADC to be approved for the treatment of HER2-positive breast cancer and the first one to be evaluated in patients with NSCLC; T-DM1 has a DAR of 3.5 [30,32].