Entinostat,a classⅠselective histone deacetylase inhibitor,plus exemestane for Chinese patients with hormone receptor-positive advanced breast cancer:A multicenter,randomized,double-blind,placebo-controlled,phase 3 trial

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%)patients 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).