Estetrol (E4) for the treatment of moderate to severe vasomotor symptoms in postmenopausal women – Efficacy and safety results from the phase 3 E4COMFORT I multicenter, placebo-controlled study

OBJECTIVE: To evaluate the efficacy and safety of estetrol in reducing moderate to severe vasomotor symptoms in postmenopausal women. METHODS: Multicenter, randomized, parallel group (1:1:1), placebo-controlled, double-blind, phase 3 study in hysterectomized and non-hysterectomized participants aged 40-65 years. A total of 640 participants with seven or more moderate to severe hot flashes daily or 50 weekly received estetrol 15 mg, estetrol 20 mg, or placebo for 12 weeks. Co-primary endpoints were the change in frequency and severity of moderate to severe vasomotor symptoms from baseline to weeks 4 and 12. Comparisons versus placebo were made using a mixed-effects model for repeated measures. The safety of estetrol alone was evaluated in relation to treatment-emergent adverse events. RESULTS: Estetrol 15 mg and 20 mg produced significant reductions in the weekly frequency of moderate to severe vasomotor symptoms at week 4 (least square means: -9.63, P = 0.038; and - 14.94, P < 0.001) and at week 12 (-16.41, P < 0.001; and - 22.49, P < 0.001), relative to placebo. Vasomotor symptom severity was significantly reduced with both estetrol doses at week 4 (-0.27, P = 0.011; and - 0.29, P = 0.005) and at week 12 (-0.54 and - 0.66 [both P < 0.0001]), compared with placebo. Drug-related treatment-emergent adverse events occurred in 51.6%, 57.3%, and 20.6% of participants in the estetrol 15 mg, 20 mg, and placebo groups, respectively, with discontinuations due to treatment-emergent adverse events in 6.6%, 7.5%, and 2.3%, respectively. CONCLUSIONS: Estetrol reduced the frequency and severity of moderate to severe vasomotor symptoms and was well tolerated, with low discontinuation rates, supporting its use in symptomatic postmenopausal women. CLINICAL TRIAL REGISTRATION: NCT04209543.