ERBB2 and breast cancer: Trastuzumab deruxtecan has received the Food and Drug Administration (FDA) and European Medical Agency (EMA) approval for patients with HER2-positive, unresectable, or metastatic breast cancer (DESTINY-Breast03 trial).44 Furthermore, it has been observed that ADCs exhibit anticancer properties even in cases of HER2-low breast cancer, wherein the HER2 antigen is expressed on breast cancer cells without any gene amplification.