Nonetheless, patients with HER2-low-expression BC, comprising 45%-55% of BC cases, frequently derive limited benefit from conventional anti-HER2 medications.17,18 Recent clinical studies on novel anti-HER2 ADCs have shown promising therapeutic efficacy in patients with HER2-low-expression BC, signaling a shift in their treatment landscape.19-21 DESTINY-Breast04 (DB-04) is the first phase III clinical trial to achieve positive results for patients with HER2-low-expression metastatic BC. The gene discussed is ERBB2; the disease is breast cancer.