ERBB2 and breast cancer: In contrast to the lack of efficacy of neratinib, DS-8201a, a humanized HER2 antibody topoisomerase I inhibitor drug conjugate (trastuzumab deruxtecan, Daiichi-Sankyo) recently approved by the FDA for unresectable or metastatic HER2-positive breast cancer (NCT03248492)38, significantly inhibited UCC14-PDX growth.