Compared with placebo plus fulvestrant, PFS was significantly improved by CDK4/6 inhibitor plus fulvestrant, mTOR inhibitor plus fulvestrant, mTOR inhibitor plus exemestane, and PI3K inhibitor plus fulvestrant, but not HDAC inhibitor plus exemestane….mTOR inhibitor and CDK4/6 inhibitor-based regimens demonstrated superior clinical efficacy and comparable safety profiles as second-line treatment in patients with HR-positive, HER2-negative advanced breast cancer.