摘要Entinostat plus exemestane in hormone receptor-positive(HR+)advanced breast cancer(ABC)previously showed encouraging outcomes.This multicenter phase 3 trial evaluated the efficacy and safety of entinostat plus exemestane in Chinese patients with HR+ABC that relapsed/progressed after≥1 endocrine therapy.Patients were randomized(2:1)to oral exemestane 25 mg/day plus entinostat(n=235)or placebo(n=119)5 mg/week in 28-day cycles.The primary endpoint was the independent radiographic committee(IRC)-assessed progression-free survival(PFS).The median age was 52(range,28-75)years and 222(62.7％)patients were postmenopausal.CDK4/6 inhibitors and fulvestrant were previously used in 23(6.5％)and 92(26.0％)patients,respectively.The baseline characteristics were comparable between the entinostat and placebo groups.The median PFS was 6.32(95％CI,5.30-9.11)and 3.72(95％CI,1.91-5.49)months in the entinostat and placebo groups(HR,0.76;95％CI,0.58-0.98;P=0.046),respectively.Grade≥3 adverse events(AEs)occurred in 154(65.5％)pa-tients in the entinostat group versus 23(19.3％)in the placebo group,and the most common grade≥3 treatment-related AEs were neutropenia[103(43.8％)],thrombocytopenia[20(8.5％)],and leucopenia[15(6.4％)].Entinostat plus exemestane significantly improved PFS compared with exemestane,with generally manageable toxicities in HR+ABC(ClinicalTrials.gov#NCT03538171).