ERBB2 and breast cancer: It is currently undergoing further clinical trials: DESTINY-Breast03 (NCT03529110) [38], to compare trastuzumab emtansine and [fam]-trastuzumab deruxtecan for unresectable and/or metastatic breast cancer previously treated with trastuzumab and taxane, and DESTINY-Breast02 (NCT03523585) [39], to observe the efficacy of [fam]-trastuzumab deruxtecan in pre-treated HER2 breast cancer that cannot be surgically removed or has spread.