ERBB2 and breast cancer: For example, trastuzumab deruxtecan (T-DXd) therapy provided a survival benefit in patients with advanced HER2-low breast cancer, suggesting that antibody–drug coupler (ADC) analogues may have a targeted killing effect on low HER2-expressing tumour cells (Modi et al., 2022) In the current study, we present the study of ADCs for HER2-low expression in advanced breast cancer patients and describe the progress and challenges in the treatment of advanced breast cancer patients with low HER2 expression.