Estetrol (Donesta) relieved vasomotor menopausal symptoms without stimulating breast tenderness or raising triglyceride levels in a dose-finding study of the investigational drug presented at the annual meeting of the North American Menopause Society.
Estetrol (E4), an estrogen produced by the fetal liver, is the first native estrogen acting selectively in tissues. Since it crosses the placenta, estetrol is present in maternal urine at about 9 weeks’ gestation. In fetal plasma, it circulates at concentrations about 12 times higher than maternal estetrol levels. The hormone has a half-life of 28-32 hours, longer than the half-life of most other estrogens.
E4 “has been shown to have a remarkably safe profile and I like to describe it as the first natural oral estrogen with the safety profile of a transdermal estrogen,” said, the Arthur H. Bill Professor of Obstetrics & Gynecology at Case Western Reserve University, Cleveland. Estetrol uniquely activates nuclear estrogen receptor–alpha, while antagonizing membrane estrogen receptor-alpha. These properties give E4 selective tissue action, with low breast stimulation meaning less breast tenderness and “low carcinogenic impact.”
Additionally, triglyceride levels are minimally affected, and serum markers for venous thromboembolism generally remain unchanged with E4 exposure, he said.
In a phase 2b dose-finding study, a variety of estetrol doses were compared with placebo to treat vasomotor symptoms in postmenopausal women aged 40-65 years with at least 7 moderate to severe hot flashes daily, or at least 50 moderate to severe hot flashes in the week before randomization. The multicenter, double-blind randomized controlled trial took place in five European countries, with 200 women overall completing the study. The study design excluded women with personal histories of malignancy, thromboembolism, or coagulopathy, and women with diabetes and poor glycemic control. Women with a uterus who had current or past endometrial hyperplasia, polyps, or an abnormal cervical smear were also excluded.
Women who had an intact uterus were included if transvaginal ultrasound showed endometrial thickness of 5 mm or less. Participants were randomized 1:1:1:1 to receive four different E4 doses: 2.5 mg, 5 mg, 10 mg, or 15 mg.
At the highest dose of 15 mg, E4 significantly reduced the frequency of vasomotor symptoms compared with placebo by study week 4 and throughout the 12-week study period (P less than .05).
This high dose also resulted in a 28% reduction in vasomotor symptom severity, compared with placebo by study week 12, with a significant separation from placebo by week 12.
In terms of the number of women who experienced at least a 50% drop in severe vasomotor symptoms, the 15-mg E4 dose also bested placebo (P less than .01). Among the group taking the 15 mg dose, significantly more also saw at least a 75% drop in frequency of severe vasomotor symptom (P less than .001).
Vaginal cytology showed that by week 12 all doses of E4 significantly increased the vaginal maturation index from baseline, a finding that corresponds with less thinning of vaginal tissues (P less than .001, compared with placebo for all doses).
The safety profile of E4 was good, Dr. Utian said. Coagulation markers were unaffected, and most lipid and blood glucose markers were also unchanged. There were “small but potentially beneficial changes in HDL-C [HDL cholesterol levels] and HbA1c values [hemoglobin A1c]” in groups taking the two highest doses of E4.
Also, C-telopeptide of type 1 collagen and osteocalcin values were reduced, “suggesting reduction in bone resorption,” he said.
According to Dr. Utian, those taking the two highest doses also saw a “slight though significant increase” from baseline in sex hormone–binding globulin levels, “indicating that the E4 estrogenic effect was mild and dose dependent.”
Endometrial biopsies showed no hyperplasia. In those taking the 15-mg E4 dose, mean endometrial thickness did increase from a mean 2 mm at baseline to 6 mm at 12 weeks. However, endometrial thickness returned to baseline after progestin therapy, said Dr. Utian. There were no unexpected adverse events during the study.
Dr. Utian reported consultant relationships with Mithra, the maker of estetrol; AMAG; Pharmavite; and Endoceutics. The study was funded by Mithra.
SOURCE: Utian W. NAMS 2018, .