Results from the HORIZON-Breast06 phase 3 trial showed that trastuzumab rezetecan (SHR-A1811) improved progression-free survival versus physician’s choice chemotherapy in patients with HER2-low advanced breast cancer. In chemotherapy-naïve patients, median PFS rose to 16.6 months from 6.8 months, with benefits reported as consistent across hormone-receptor subgroups, while overall survival data remain immature.