Estetrol for the treatment of moderate to severe vasomotor symptoms in postmenopausal women: The design of the E4COMFORT I and II trials

Estetrol is a natural estrogen with a favorable safety profile, showing minimal effects on liver proteins, blood clotting, and breast tissue, which may reduce the risks of blood clots and cardiovascular disease. This review presents the profile of estetrol in support of the rationale of two pivotal phase 3 clinical trials, E4COMFORT I and E4COMFORT II, as well as the design of those. E4COMFORT I and II are aimed at assessing the efficacy and safety of estetrol in the treatment of moderate to severe vasomotor symptoms in postmenopausal women. The E4COMFORT I and II trials were divided into an efficacy part (arms 1-3) and a safety part (arm 4). Efficacy was evaluated through a randomized, double-blind, placebo-controlled study examining two doses of estetrol (15 mg and 20 mg) in postmenopausal participants, both hysterectomized and non-hysterectomized, who experienced 7 or more moderate to severe vasomotor symptoms per day (or 50 or more per week). To comply with Food and Drug Administration and European Medicines Agency guidelines for long-term safety assessments in both groups, these trials evaluated the overall and endometrial safety of unopposed estetrol and of estetrol combined with natural progesterone. The total enrolment across the E4COMFORT I and II trials was 2576 participants. The results of these trials are expected to give a thorough understanding of estetrol 's potential as a new, distinctive treatment option for women with postmenopausal symptoms. CLINICALTRIALS REGISTRATION: NCT04209543 and NCT04090957.