The open-label, phase 3 DESTINY-Breast03 trial enrolled patients with unresectable or metastatic HER2-positive breast cancer who had received prior anti-HER2 treatment in the metastatic setting, as well as individuals who had progressed during or within 6 months of trastuzumab + taxane therapy in the (neo)adjuvant setting. The gene discussed is ERBB2; the disease is breast cancer.