DESTINY-Breast11 is the first trial investigating trastuzumab deruxtecan (T-DXd) as neoadjuvant therapy for high-risk early HER2+ breast cancer, leveraging its unique ability to address intratumoral HER2 heterogeneity via a cleavable linker that enables bystander killing of low-HER2-expressing cells. This evidence concerns the gene ERBB2 and breast cancer.