Two phase 3 clinical trials are currently evaluating the efficacy of trastuzumab deruxtecan (T-Dxd, DS-8201) in this dawning breast cancer subtype; DESTINY-Breast04 has revealed exciting positive results that trastuzumab deruxtecan almost doubled the progression-free survival in advanced HER2-Low breast cancer patients compared to the physician’s choice [7]. Here, ERBB2 is linked to breast cancer.