Preventive effect of oral estetrol in a menopausal hot flush model

Oestrogens in oral contraception: considerations for tailoring prescription to women's needs

BACKGROUND

The oestrogenic component of combined oral contraceptives (COCs) has changed over years with the aim of reducing oestrogen-related side effects and risks, whilst maintaining oestrogen beneficial effects, particularly on cycle control.

PURPOSE

To describe the pharmacological profiles of different oestrogens commonly used in COCs to provide insights on contraceptive prescription tailored to women's needs.

RESULTS

All COCs ensure a high contraceptive efficacy. COCs containing the natural oestrogens oestradiol (E2), oestradiol valerate (E2V) and estetrol (E4) have limited impact on liver metabolism, lipid and carbohydrate metabolism, haemostasis and sex hormone binding globulin levels, compared with ethinylestradiol (EE). COCs with E2 and E2V appear also to entail a lower elevation of the risk of venous thromboembolism vs. EE-containing pills. No epidemiological data are available for E4-COC. E2- and E2V-containing COCs seem to exert a less stabilising oestrogenic effect on the endometrium compared with EE-COCs. The E4-COC results in a predictable bleeding pattern with a high rate of scheduled bleeding and minimal unscheduled bleeding per cycle. Based on in vitro and in vivo animal data, E4 seems to be associated with a lower effect on cell breast proliferation.

CONCLUSION

Today various COCs contain different oestrogens. Prescribers must be familiar with the different properties of each oestrogen for a tailored contraceptive recommendation, considering their safety and contraceptive efficacy, as well as women's needs and preferences.

Estetrol Inhibits Endometriosis Development in an In Vivo Murine Model

Endometriosis is characterized by the growth of endometrial-like tissue outside the uterus, and it is associated with alterations in the expression of hormone receptors and inflammation. Estetrol (E4) is a weak estrogen that recently has been approved for contraception. We evaluated the effect of E4 on the growth of endometriotic-like lesions and the expression of TNF-α, estrogen receptors (ERs), and progesterone receptors (PRs) in an in vivo murine model. Endometriosis was induced surgically in female C57BL/6 mice. E4 was delivered via Alzet pump (3 mg/kg/day) from the 15th postoperative day for 4 weeks. E4 significantly reduced the volume (p < 0.001) and weight (p < 0.05) of ectopic lesions. Histologically, E4 did not affect cell proliferation (PCNA immunohistochemistry) but it did increase cell apoptosis (TUNEL assay) (p < 0.05). Furthermore, it modulated oxidative stress (SOD, CAT, and GPX activity, p < 0.05) and increased lipid peroxidation (TBARS/MDA, p < 0.01). Molecular analysis showed mRNA (RT-qPCR) and protein (ELISA) expression of TNF-α decreased (p < 0.05) and mRNA expression of Esr2 reduced (p < 0.05), in contrast with the increased expression of Esr1 (p < 0.01) and Pgr (p < 0.05). The present study demonstrates for the first time that E4 limited the development and progression of endometriosis in vivo.

Comparison of Estetrol Exposure between Women and Mice to Model Preclinical Experiments and Anticipate Human Treatment

Estetrol (E4) is a natural estrogen with promising therapeutic applications in humans. The European Medicines Agency and the Food and Drug Administration have approved the use of 15 mg E4/3 mg drospirenone for contraceptive indication. Phase III clinical trials with 15-20 mg E4 for the relief of climacteric complaints are currently running. Relevant data from preclinical animal models are needed to characterize the molecular mechanisms and the pharmacological effects of E4 and possibly to reveal new therapeutic applications and to anticipate potential adverse effects. Therefore, it is important to design experimental procedures in rodents that closely mimic or anticipate human E4 exposure. In this study, we compared the effects of E4 exposure after acute or chronic administration in women and mice. Women who received chronic E4 treatment per os at a dose of 15 mg once daily reached a steady state within 6 to 8 days, with a mean plasma concentration of 3.20 ng/mL. Importantly, with subcutaneous, intraperitoneal or oral administration of E4 in mice, a stable concentration over time that would mimic human pharmacokinetics could not be achieved. The use of osmotic minipumps continuously releasing E4 for several weeks provided an exposure profile mimicking chronic oral administration in women. Measurements of the circulating concentration of E4 in mice revealed that the mouse equivalent dose necessary to mimic human treatment does not fit with the allometric prediction. In conclusion, this study highlights the importance of precise definition of the most appropriate dose and route of administration to utilize when developing predictive preclinical animal models to mimic or anticipate specific human treatment.

Estetrol: From Preclinical to Clinical Pharmacology and Advances in the Understanding of the Molecular Mechanism of Action

Estetrol (E4) is the most recently described natural estrogen. It is produced by the human fetal liver during pregnancy and its physiological function remains unclear. E4 is the estrogenic component of a recently approved combined oral contraceptive. It is also in development for use as menopausal hormone therapy. In the context of these developments, the pharmacological activity of E4, alone or in combination with a progestin, has been extensively characterized in preclinical models as well as in clinical studies in women of reproductive age and postmenopausal women. Despite the clinical benefits, the use of oral estrogens for contraception or menopause is also associated with unwanted effects, such as an increased risk of breast cancer and thromboembolic events, due to their impact on non-target tissues. Preclinical and clinical data for E4 point to a tissue-specific activity and a more selective pharmacological profile compared with other estrogens, including a low impact on the liver and hemostasis balance. This review summarizes the characterization of the pharmacological properties of E4 as well as recent advances made in the understanding of the molecular mechanisms of action driving its activity. How the unique mode of action and the different metabolism of E4 might support its favorable benefit-risk ratio is also discussed.

Profile of estetrol, a promising native estrogen for oral contraception and the relief of climacteric symptoms of menopause

INTRODUCTION

Estrogens used in women's healthcare have been associated with increased risks of venous thromboembolism (VTE) and breast cancer. Estetrol (E4), an estrogen produced by the human fetal liver, has recently been approved for the first time as a new estrogenic component of a novel combined oral contraceptive (E4/drospirenone [DRSP]) for over a decade. In phase 3 studies, E4/DRSP showed good contraceptive efficacy, a predictable bleeding pattern, and a favorable safety and tolerability profile.

AREAS COVERED

This narrative review discusses E4's pharmacological characteristics, mode of action, and the results of preclinical and clinical studies for contraception, as well as for menopause and oncology.

EXPERT OPINION

Extensive studies have elucidated the properties of E4 that underlie its favorable safety profile. While classical estrogens (such as estradiol) exert their actions via both activation of nuclear and membrane estrogen receptor α (ERα), E4 presents a specific profile of ERα activation: E4 binds and activates nuclear ERα but does not induce the activation of membrane ERα signaling pathways in specific tissues. E4 has a small effect on normal breast tissue proliferation and minimally affects hepatic parameters. This distinct profile of ERα activation, uncoupling nuclear and membrane activation, is unique.

Estetrol: A New Choice for Contraception

Estetrol (E4) is a natural estrogenic steroid that is normally produced by human fetal liver. Recent research has demonstrated that it is a potent, orally bioavailable, natural selective estrogen receptor modulator; it has a moderate affinity for both human estrogen receptor alpha (ERα) and ERβ, with a preference for ERα. Clinical studies have demonstrated possible use as an estrogen in combined oral contraceptives (COC). COCs containing E4 and drospirenone (DRSP) showed a high acceptability, tolerability, and user satisfaction also when compared to COCs containing ethinylestradiol (EE). E4/DRSP effectively inhibits ovulation, with a similar effect on endometrium thickness than that of EE-containing COCs. Low doses (15 mg) of E4 with DRSP (3 mg) showed promising results in term of bleeding pattern and cycle control, also when compared to other COCs containing synthetic estrogens. Moreover, the association has limited effects on serum lipids, liver, SHBG levels, and carbohydrate metabolism. This combination also could drive a lower risk of venous thromboembolism than EE-containing COCs. In this review, we will summarize the actual knowledge about the new E4-containing contraceptive. Further large-scale studies in the full target population are needed to provide more insights into the cardiovascular safety profile and user satisfaction of E4/DRSP.

Estetrol and Mammary Gland: Friends or Foes?

Estrogens have pleiotropic effects on many reproductive and non-reproductive tissues and organs including the mammary gland, uterus, ovaries, vagina, and endothelium. Estrogen receptor α functions as the principal mediator of estrogenic action in most of these tissues. Estetrol (E4) is a native fetal estrogen with selective tissue actions that is currently approved for use as the estrogen component in a combined oral contraceptive and is being developed as a menopause hormone therapy (MHT, also known as hormone replacement therapy). However, exogenous hormonal treatments, in particular MHTs, have been shown to promote the growth of preexisting breast cancers and are associated with a variable risk of breast cancer depending on the treatment modality. Therefore, evaluating the safety of E4-based formulations on the breast forms a crucial part of the clinical development process. This review highlights preclinical and clinical studies that have assessed the effects of E4 and E4-progestogen combinations on the mammary gland and breast cancer, focusing in particular on the estrogenic and anti-estrogenic properties of E4. We discuss the potential advantages of E4 over current available estrogen-formulations as a contraceptive and for the treatment of symptoms due to menopause. We also consider the potential of E4 for the treatment of endocrine-resistant breast cancer.

Tumor suppression, dose-limiting toxicity and wellbeing with the fetal estrogen estetrol in patients with advanced breast cancer

Purpose

The aim of this study (the ABCE4 study) was to assess dose-limiting toxicity (DLT), safety, tolerability and preliminary efficacy of high doses of the fetal estrogen estetrol (E4) in postmenopausal patients with heavily pretreated, locally advanced and/or metastatic ER+/HER2−breast cancer, resistant to anti-estrogens.

Methods

This was a multicenter, open-label, phase IB/IIA, dose-escalation study with a 3 + 3 cohort design, whereby successive cohorts of three patients received 20 mg, 40 mg or 60 mg E4 per day for 12 weeks by oral administration. DLTs, safety and wellbeing were evaluated after 4, 8 and 12 weeks of treatment. Anti-tumor effects were investigated by computer tomography scanning and evaluated according to RECIST criteria before and after 12 weeks of treatment. Wellbeing was judged weekly by the investigator and by quality-of-life questionnaires by the patients. In view of the small number of patients, no statistical testing was performed.

Results

All 12 patients enrolled had progressive, heavily pre-treated advanced breast cancer. No treatment-related serious adverse events or DLTs occurred during the first 4 weeks of E4 treatment allowing the investigation of all three doses. Five of nine patients completing 12 weeks of E4 treatment showed objective anti-tumor effects and six of nine patients reported improved wellbeing.

Conclusion

High doses of estetrol seem to be safe and are well tolerated during 12 weeks of treatment without dose-limiting toxicity and with anti-tumor effects in five of nine heavily treated patients with progressive, anti-estrogen resistant, advanced breast cancer.

Acupuncture ameliorated vasomotor symptoms during menopausal transition: single-blind, placebo-controlled, randomized trial to test treatment efficacy

OBJECTIVES

This study aimed to evaluate the effects of acupuncture on women with vasomotor symptoms during the menopausal transition with the aid of the Kupperman-Blatt Menopausal Index.

METHOD

Crossover, single-blind, sham-controlled trial with 100 women randomly divided into two groups of 50 participants each: G1 and G2. During the first 24 weeks of treatment, the G1 women received acupuncture and the G2 women were given sham acupuncture. The crossover was then applied: the G1 participants were given sham acupuncture, and the G2 participants received acupuncture for 24 more weeks.

RESULTS

The mean score of hot flashes of the group who first experienced acupuncture (G1) was statistically higher than that of the group that started with sham acupuncture (G2, P = 0.020). Also, both groups had similar mean scores in the middle of the study (both were receiving acupuncture). During the last 6 months of the study, after crossover, the values of G2 (acupuncture) were lower than those of G1 (sham acupuncture).

CONCLUSIONS

Acupuncture treatment may mitigate hot flashes and other climacteric symptoms during the menopausal transition.

[Towards an optimization of the modulation of the estrogen receptor during menopausal hormonal therapy]

Women now live more than a third of their lives after the onset of menopause. The decline in endogenous estrogen production during this period is accompanied by functional disorders that affect quality of life. These symptoms may be relieved by menopausal hormone therapy (MHT) initially based on the administration of equine conjugated estrogens (mainly in the United States, oral route) or the natural estrogen, 17β-estradiol (in Europe, transdermal route). Estrogen receptor α (ERα), but not ERβ, mediates most of the physiological effects of estrogens. ERα belongs to the superfamily of nuclear receptors and regulates the transcription of genes via its activation functions AF1 and AF2. In addition to these classical genomic actions, estrogens can activate a subpopulation of ERα present at the cell membrane and thereby induce rapid signals. In this review, we will summarize the evolution of MHTs in last decades, as well as treatments that use various selective estrogen receptor modulators (SERMs). Next, we will describe recent advances in the understanding of the mechanisms of estrogen action, in particular the respective roles of nuclear and membrane ERα as well as the potential implications for future therapies.

Effect of estetrol, a selective nuclear estrogen receptor modulator, in mouse models of arterial and venous thrombosis

Estetrol (E4) is a natural estrogen synthesized exclusively during pregnancy by the human fetal liver, and the physiological role of this hormone is unknown. Interestingly, E4 was recently evaluated in preclinical and phase II-III clinical studies in combination with a progestin, with the advantage to not increase the circulating level of coagulation factors, at variance to oral estradiol or ethinylestradiol. Here, we evaluated the effect of E4 on hemostasis and thrombosis in mouse. Following chronic E4 treatment, mice exhibited a prolonged tail-bleeding time and were protected from arterial and also venous thrombosis in vivo. In addition, E4 treatment decreased ex vivo thrombus growth on collagen under arterial flow conditions. We recently showed that E4 activates uterine epithelial proliferation through nuclear estrogen receptor (ER) α. To analyze the impact of nuclear ERα actions on hemostasis and thrombosis, we generated hematopoietic chimera with bone marrow cells deficient for nuclear ERα. E4-induced protection against thromboembolism was significantly reduced in the absence of hematopoietic nuclear ERα activation, while the increased tail-bleeding time was not impacted by this deletion. In addition to its "liver friendly" profile described in women, our data shows that E4 has anti-thrombotic properties in various mouse models. Altogether, the natural fetal estrogen E4 could represent an attractive alternative to classic estrogens in oral contraception and treatment of menopause.

Buspirone Nanovesicular Nasal System for Non-Hormonal Hot Flushes Treatment

The aim of this work was to design and characterize a new nanovesicular nasal delivery system (NDS) containing buspirone, and investigate its efficiency in an animal model for the treatment of hot flushes. The presence of multilamellar vesicles with a mean size distribution of 370 nm was evidenced by transition electron microscopy (TEM), cryo-scanning electron microscopy (Cryo-SEM), and dynamic light scattering (DLS) tests. Pharmacodynamic evaluation of the nasal treatment efficacy with the new system was carried out in ovariectomized (OVX) rat—an animal model for hot flushes—and compared with other treatments. We found that the nasal administration of a buspirone NDS resulted in a significant reduction in tail skin temperature (TST). This effect was not observed in the control buspirone-treated groups. Buspirone levels in the plasma and brain of nasally-treated normal rats were quantified and compared with those of rats that had received oral administration by a LC-MS/MS assay. A significantly higher bioavailability was achieved with the new treatment relative to an oral administration of the same drug dose. No pathological changes in the nasal cavity were observed following sub-chronic nasal administration of buspirone NDS. In conclusion, the data of our investigation show that buspirone in the new nanovesicular nasal carrier could be considered for further studies for the development of a treatment for the hot flushes ailment.

Towards optimization of estrogen receptor modulation in medicine

Women now spend more than one-third of their lives in the postmenopausal years, and the decline of endogenous estrogen production during menopause is accompanied by a series of functional disorders that affect the quality of life. These symptoms could be alleviated or even totally suppressed by menopausal hormone therapy (MHT), initially based on natural estrogens extracted from the urine of pregnant mares (mainly in the USA, using the oral route) and later from the synthesis of the natural estrogen, 17β-estradiol (mainly in Europe, in particular using the transdermal route). Estrogen receptor (ER) α is the main receptor mediating the physiological effects of estrogens. ERα belongs to the nuclear receptor superfamily and activates gene transcription in a time and tissue-specific manner through two distinct activation functions (AF), AF1 and AF2. In addition to these classical genomic actions, ERα also mediates membrane initiated signaling enabling rapid actions of estrogen, potentially along or in interaction with other receptors. Here, we provide a brief historical overview of MHT, and we then highlight recent advances in the characterization of new treatments based on the association of estrogens with selective estrogen receptor modulators (SERMs) or on the modulation of nuclear or membrane ERα.

Pharmacodynamic effects of the fetal estrogen estetrol in postmenopausal women: results from a multiple-rising-dose study

OBJECTIVE

Estetrol (E4) is an estrogen produced exclusively by the human fetal liver during pregnancy. In this study the pharmacodynamic effects of escalating doses of E4 in postmenopausal women were investigated.

METHODS

This was a partly randomized, open-label, multiple-rising-dose study in 49 postmenopausal women. Participants were randomized to receive either 2 mg E4 or 2 mg estradiol-valerate (E2 V) for 28 days. Subsequent dose-escalation groups were (non-randomized): 10, 20 and 40 mg E4. Blood samples were collected regularly for measuring endocrine and hemostasis variables, lipids and lipoproteins, fasting glucose and bone turnover markers.

RESULTS

Estetrol treatment resulted in a decrease of follicle-stimulating hormone and luteinizing hormone and an increase of sex-hormone binding globulin. Changes in hemostasis variables were small. A lowering effect on low-density lipoprotein cholesterol was accompanied with an increase in high-density lipoprotein cholesterol and no or minimal changes in triglycerides. The considerable decrease in osteocalcin levels in the three highest E4 dose groups and the small decrease in C-telopeptide levels were comparable to the E2 V control group and suggest a preventive effect on bone loss. All changes observed were dose-dependent.

CONCLUSIONS

In this study, estetrol treatment showed dose-dependent estrogenic effects on endocrine parameters, bone turnover markers, and lipids and lipoproteins. The effect on triglycerides was small as were the effects on hemostatic variables. These results support the further investigation of estetrol as a candidate for hormone therapy. Quantitatively, the effects of 10 mg estetrol were similar to the study comparator 2 mg estradiol valerate.

Estradiol shows anti-skin cancer activities through decreasing MDM2 expression

Estradiol plays important roles in many biological responses inducing tumor genesis and cancer treatment. However, the effects of estradiol on tumors were inconsistent among a lot of researches and the mechanism is not fully understood. Our previous study indicated that splicing factor hnRNPA1 could bind to the human homologue of mouse double minute (MDM2), an oncogene which has been observed to be over-expressed in numerous types of cancers. In this research, we investigated whether and how estradiol correlate to cancer cell behaviors through heterogeneous nuclear ribonucleoprotein (hnRNPA1) and MDM2. Results showed that 10×10^-13Mestradiol elevated the expression of hnRNPA1 regardless ER expression in cells, and then down-regulated the expression of MDM2. At the same time, estradiol inhibited cell proliferation, migration and epithelial-mesenchymal transition progression of A375 and GLL19 cells. While, knocking down hnRNPA1 through the transfection of hnRNPA1 siRNA led to the increase of MDM2 at both protein level and gene level In vivo experiment, subcutaneous injection with estradiol every two days near the tumor at doses of 2.5mg/kg/d suppressed tumor growth and reduced MDM2 expression. In a word, via increasing hnRNPA1 level and then reducing the expression of MDM2, estradiol prevented carcinogenesis in melanomas. We confirmed therapeutic effect of estradiol, as well as a new way for estradiol to resist skin cancer.

A Comprehensive Method To Quantify Adaptations by Male and Female Mice With Hot Flashes Induced by the Neurokinin B Receptor Agonist Senktide

Vasomotor symptoms (VMS; or hot flashes) plague millions of reproductive-aged men and women who have natural or iatrogenic loss of sex steroid production. Many affected individuals are left without treatment options because of contraindications to hormone replacement therapy and the lack of equally effective nonhormonal alternatives. Moreover, development of safer, more effective therapies has been stymied by the lack of an animal model that recapitulates the hot-flash phenomenon and enables direct testing of hypotheses regarding the pathophysiology underlying hot flashes. To address these problems, we developed a murine model for hot flashes and a comprehensive method for measuring autonomic and behavioral thermoregulation in mice. We designed and constructed an instrument called a thermocline that produces a thermal gradient along which mice behaviorally adapt to a thermal challenge to their core body temperature set point while their thermal preference over time is tracked and recorded. We tested and validated this murine model for VMS by administration of a TRPV1 agonist and a neurokinin B receptor agonist, capsaicin and senktide, respectively, to unrestrained mice and observed their autonomic and behavioral responses. Following both treatments, the mice exhibited a VMS-like response characterized by a drop in core body temperature and cold-seeking behavior on the thermocline. Senktide also caused a rise in tail skin temperature and increased Fos expression in the median preoptic area, a hypothalamic temperature control center. This dynamic model may be used to fully explore the cellular and molecular bases for VMS and to develop and test new therapeutic options.

Estetrol, a Fetal Selective Estrogen Receptor Modulator, Acts on the Vagina of Mice through Nuclear Estrogen Receptor α Activation

The genitourinary syndrome of menopause has a negative impact on quality of life of postmenopausal women. The treatment of vulvovaginal atrophy includes administration of estrogens. However, oral estrogen treatment is controversial because of its potential risks on venous thrombosis and breast cancer. Estetrol (E4) is a natural estrogen synthesized exclusively during pregnancy by the human fetal liver and initially considered as a weak estrogen. However, E4 was recently evaluated in phase 1 to 2 clinical studies and found to act as an oral contraceptive in combination with a progestin, without increasing the level of coagulation factors. We recently showed that E4 stimulates uterine epithelial proliferation through nuclear estrogen receptor (ER) α, but failed to elicit endothelial responses. Herein, we first evaluated the morphological and functional impacts of E4 on the vagina of ovariectomized mice, and we determined the molecular mechanism mediating these effects. Vaginal epithelial proliferation and lubrication after stimulation were found to increase after E4 chronic treatment. Using a combination of pharmacological and genetic approaches, we demonstrated that these E4 effects on the vagina are mediated by nuclear ERα activation. Altogether, we demonstrate that the selective activation of nuclear ERα is both necessary and sufficient to elicit functional and structural effects on the vagina, and therefore E4 appears promising as a therapeutic option to improve vulvovaginal atrophy.

Clinical effects of the fetal estrogen estetrol in a multiple-rising-dose study in postmenopausal women

OBJECTIVE

Estetrol (E4) is a natural fetal estrogen. The safety of increasing doses of E4 and its preliminary effects on the vagina, endometrium and menopausal vasomotor symptoms were investigated.

STUDY DESIGN

This was a partly randomized, open-label, multiple-rising-dose study in 49 postmenopausal women. Subjects with an intact uterus were randomized to receive either 2mg E4 or 2mg estradiol-valerate (E2V) for 28days. Subsequent dose-escalation groups (non-randomized) were: 10mg E4 (intact uterus and ≥35 hot flushes/week); and 20mg and 40mg E4 (hysterectomized subjects).

MAIN OUTCOME MEASURE

Adverse events (AEs) and vaginal cytology were evaluated in all treatment groups; hot flushes/sweating and endometrial proliferation were analyzed with 2 and 10mg E4 and 2mg E2V.

RESULTS

Estetrol appeared to be safe, without serious drug-related AEs. In all the groups there was a clear shift from parabasal to superficial vaginal cells, indicating an estrogenic effect and a potential for the treatment of vulvovaginal atrophy. The endometrial thickness remained stable in the 2mg E4 group and increased with E2V and 10mg E4. A decrease in the mean number of hot flushes and sweating was seen with 2 and 10mg E4 and 2mg E2V.

CONCLUSIONS

Estetrol in a dose range of 2-40mg per day improved vaginal cytology and vasomotor symptoms in postmenopausal women. Endometrial proliferation occurred with the 10mg dose. Estetrol seems a safe and suitable candidate to develop further for hormone therapy.

Combined estrogenic and anti-estrogenic properties of estetrol on breast cancer may provide a safe therapeutic window for the treatment of menopausal symptoms

Increased risk of breast cancer is a critical side effect associated with the use of a menopausal hormone therapy (MHT). Estetrol (E4) is a natural estrogen produced by the human fetal liver and is a promising compound for clinical use in MHT. However, its impact on breast cancer is controversial and poorly defined. In this preclinical study, we show that E4 acts as a weak estrogen by stimulating the growth of hormone-dependent breast cancer only at concentrations exceeding menopausal therapeutic needs. E4 presents also an antitumor activity by decreasing the strong proliferative effect of estradiol (E2). While estrogen receptor alpha (ERα) is the predominant receptor mediating its effects, the dual weak-estrogenic/anti-estrogenic feature of E4 results from differential signaling pathways activation. Both nuclear and rapid extra-nuclear signaling pathway are necessary for a complete estrogenic effect of E4. However, the antitumor action of E4 is not due to a capacity to antagonize E2-induced nuclear activity. Altogether, our results highlight that E4 has a limited impact on breast cancer and may offer a safe therapeutic window for the treatment of menopausal symptoms.

The uterine and vascular actions of estetrol delineate a distinctive profile of estrogen receptor α modulation, uncoupling nuclear and membrane activation

Estetrol (E₄) is a natural estrogen with a long half-life produced only by the human fetal liver during pregnancy. The crystal structures of the estrogen receptor α (ERα) ligand-binding domain bound to 17β-estradiol (E₂) and E₄ are very similar, as well as their capacity to activate the two activation functions AF-1 and AF-2 and to recruit the coactivator SRC3. In vivo administration of high doses of E₄ stimulated uterine gene expression, epithelial proliferation, and prevented atheroma, three recognized nuclear ERα actions. However, E₄ failed to promote endothelial NO synthase activation and acceleration of endothelial healing, two processes clearly dependent on membrane-initiated steroid signaling (MISS). Furthermore, E₄ antagonized E₂ MISS-dependent effects in endothelium but also in MCF-7 breast cancer cell line. This profile of ERα activation by E₄, uncoupling nuclear and membrane activation, characterizes E₄ as a selective ER modulator which could have medical applications that should now be considered further.

Estetrol is a weak estrogen antagonizing estradiol-dependent mammary gland proliferation

Estetrol (E4) is a natural estrogen produced exclusively by the human fetal liver during pregnancy. Its physiological activity remains unknown. In contrast to ethinyl estradiol and estradiol (E2), E4 has a minimal impact on liver cell activity and could provide a better safety profile in contraception or hormone therapy. The aim of this study was to delineate if E4 exhibits an activity profile distinct from that of E2 on mammary gland. Compared with E2, E4 acted as a low-affinity estrogen in both human in vitro and murine in vivo models. E4 was 100 times less potent than E2 to stimulate the proliferation of human breast epithelial (HBE) cells and murine mammary gland in vitro and in vivo respectively. This effect was prevented by fulvestrant and tamoxifen, supporting the notion that ERα (ESR1) is the main mediator of the estrogenic effect of E4 on the breast. Interestingly, when E4 was administered along with E2, it significantly antagonized the strong stimulatory effect of E2 on HBE cell proliferation and on the growth of mammary ducts. This study characterizes for the first time the impact of E4 on mammary gland. Our results highlight that E4 is less potent than E2 and exhibits antagonistic properties toward the proliferative effect of E2 on breast epithelial cells. These data support E4 as a potential new estrogen for clinical use with a reduced impact on breast proliferation.

Estetrol Modulates Endothelial Nitric Oxide Synthesis in Human Endothelial Cells

Estetrol (E4) is a natural human estrogen that is present at high concentrations during pregnancy. E4 has been reported to act as an endogenous estrogen receptor modulator, exerting estrogenic actions on the endometrium or the central nervous system but presenting antagonistic effects on the breast. Due to these characteristics, E4 is currently being developed for a number of clinical applications, including contraception and menopausal hormone therapy. Endothelial nitric oxide (NO) is a key player for vascular function and disease during pregnancy and throughout aging in women. Endothelial NO is an established target of estrogens that enhance its formation in human endothelial cells. We here addressed the effects of E4 on the activity and expression of the endothelial nitric oxide synthase (eNOS) in cultured human umbilical vein endothelial cells (HUVEC). E4 stimulated the activation of eNOS and NO secretion in HUVEC. E4 was significantly less effective compared to E2, and a peculiar concentration-dependent effect was found, with higher amounts of E4 being less effective than lower concentrations. When E2 was combined with E4, an interesting pattern was noted. E4 antagonized NO synthesis induced by pregnancy-like E2 concentrations. However, E4 did not impede the modest induction of NO synthesis associated with postmenopausal-like E2 levels. These results support the hypothesis that E4 may be a regulator of NO synthesis in endothelial cells and raise questions on its peculiar signaling in this context. Our results may be useful to interpret the role of E4 during human pregnancy and possibly to help develop this interesting steroid for clinical use.

Antiestrogenic effects of the fetal estrogen estetrol in women with estrogen-receptor positive early breast cancer

Estetrol (E4) is a fetal estrogen with estrogenic effects on reproductive organs and bone in preclinical models and in postmenopausal women. However, E4 exerts antiestrogenic effects on breast cancer (BC) cell growth in vitro and in vivo. We have investigated the effect of 14 days preoperative treatment with 20mg E4 per day on tumor proliferation markers, sex steroid receptor expression and endocrine parameters in a prospective, randomized, placebo-controlled, preoperative window trial in 30 pre- and post-menopausal women with estrogen-receptor positive early BC. E4 had a significant pro-apoptotic effect on tumor tissue, whereas Ki67 expression remained unchanged in both pre- and post-menopausal women. E4 increased sex-hormone-binding globulin significantly thereby reducing the concentrations of bioavailable estradiol. Follicle-stimulating hormone levels decreased in postmenopausal women only and luteinizing hormone levels remained unchanged. Systemic insulin growth factor-1 levels decreased significantly. Intratumoral epithelial ERα expression decreased significantly and a trend was found towards an increased expression of ERβ. This clinical data support the preclinical findings that E4 has antiestrogenic effects on BC cells, whereas earlier studies have shown that E4 has estrogenic effects on reproductive tissues and bone. Further clinical studies seem acceptable and are needed to confirm the safety and efficacy of E4 for the breast in hormone replacement therapy, including hormone replacement therapy in women who have or have had BC, especially in those BC patients treated with aromatase inhibitors and suffering from serious complaints due to estrogen deficiency.

Effects of Estetrol on Migration and Invasion in T47-D Breast Cancer Cells through the Actin Cytoskeleton

Estetrol (E4) is a natural human estrogen present at high concentrations during pregnancy. Due to its high oral bioavailability and long plasma half-life, E4 is particularly suitable for therapeutic applications. E4 acts as a selective estrogen receptor (ER) modulator, exerting estrogenic actions on the endometrium or the central nervous system, while antagonizing the actions of estradiol in the breast. We tested the effects of E4 on its own or in the presence of 17β-estradiol (E2) on T47-D ER+ breast cancer cell migration and invasion of three-dimensional matrices. E4 administration to T47-D cells weakly stimulated migration and invasion. However, E4 decreased the extent of movement and invasion induced by E2. Breast cancer cell movement requires a remodeling of the actin cytoskeleton. During exposure to E4, a weak, concentration-dependent, re-distribution of actin fibers toward the cell membrane was observed. However, when E4 was added to E2, an inhibition of actin remodeling induced by E2 was seen. Estrogens stimulate ER+ breast cancer cell movement through the ezrin-radixin-moesin family of actin regulatory proteins, inducing actin and cell membrane remodeling. E4 was a weak inducer of moesin phosphorylation on Thr(558), which accounts for its functional activation. In co-treatment with E2, E4 blocked the activation of this actin controller in a concentration-related fashion. These effects were obtained through recruitment of estrogen receptor-α. In conclusion, E4 acted as a weak estrogen on breast cancer cell cytoskeleton remodeling and movement. However, when E2 was present, E4 counteracted the stimulatory actions of E2. This contributes to the emerging hypothesis that E4 may be a naturally occurring ER modulator in the breast.

Vasorelaxing effects of estetrol in rat arteries

This study compared ex vivo relaxing responses to the naturally occurring human hormone estetrol (E(4)) vs 17β-estradiol (E(2)) in eight different vascular beds. Arteries were mounted in a myograph, contracted with either phenylephrine or serotonin, and cumulative concentration-response curves (CRCs) to E(4) and E(2) (0·1-100  μmol/l) were constructed. In all arteries tested, E(4) had lower potency than E(2), although the differential effect was less in larger than smaller arteries. In uterine arteries, the nonselective estrogen receptor (ER) blocker ICI 182 780 (1  μmol/l) caused a significant rightward shift in the CRC to both E(4) and E(2), indicating that the relaxation responses were ER dependent. Pharmacological blockade of nitric oxide (NO) synthases by N(ω)-nitro-L-arginine methyl ester (L-NAME) blunted E(2)-mediated but not E(4)-mediated relaxing responses, while inhibition of prostaglandins and endothelium-dependent hyperpolarization did not alter relaxation to either E(4) or E(2) in uterine arteries. Combined blockade of NO release and action with L-NAME and the soluble guanylate cyclase (sGC) inhibitor ODQ resulted in greater inhibition of the relaxation response to E(4) compared with E(2) in uterine arteries. Endothelium denudation inhibited responses to both E(4) and E(2), while E(4) and E(2) concentration-dependently blocked smooth muscle cell Ca(2)(+) entry in K(+)-depolarized and Ca(2)(+)-depleted uterine arteries. In conclusion, E(4) relaxes precontracted rat arteries in an artery-specific fashion. In uterine arteries, E(4)-induced relaxations are partially mediated via an endothelium-dependent mechanism involving ERs, sGC, and inhibition of smooth muscle cell Ca(2)(+) entry, but not NO synthases or endothelium-dependent hyperpolarization.

S-equol and the fermented soy product SE5-OH containing S-equol similarly decrease ovariectomy-induced increase in rat tail skin temperature in an animal model of hot flushes

OBJECTIVE

The aim of this study was to compare the effect of SE5-OH, a fermented soy product containing S-equol, with purified S-equol on hot flushes in an ovariectomized rat model.

METHODS

Eleven-week-old female Sprague-Dawley rats were assigned to either the sham group (vehicle; n = 30) or one of four ovariectomized groups: control (vehicle; n = 30), conjugated equine estrogens (CEE; 6.0 mg kg(-1) d(-1) CEE; n = 10), SE5-OH (2,000 mg kg(-1) d(-1) SE5-OH containing 11.7 mg kg(-1) d(-1) as S-equol; n = 30), and S-equol (11.7 mg kg(-1) d(_1) S-equol; n = 30). Three days after sham operation or ovariectomy, animals were treated once daily for 38 days. Tail skin temperature (TST) was assessed on days 21, 28, and 35 after surgery. Plasma estradiol and follicle-stimulating hormone levels and uterine weight and uteri histology were evaluated at the end of treatment.

RESULTS

The rise in TST resulting from ovariectomy was inhibited by CEE, SE5-OH, and S-equol. Compared with the control, TST was decreased by 68.9% and 86.2% in SE5-OH group on days 21 and 28, respectively (P = 0.014, 0.020), and by 60.1% and 89.1% in S-equol group, respectively (P = 0.038, 0.016). Unlike in the CEE group, plasma estradiol and follicle-stimulating hormone levels, uterine weight, epithelial height, stromal expansion, and myometrial thickness were not affected in SE5-OH and S-equol groups.

CONCLUSIONS

The results of this animal model of hot flushes suggest that S-equol is one of the primary components of SE5-OH and that both SE5-OH and S-equol represent promising alternatives for the treatment of menopausal symptoms. Clinical research is needed to confirm these findings.

Pharmacology and clinical applications of selective estrogen receptor modulators

Compounds that can be described as selective estrogen receptor modulators (SERMs) have expanded dramatically over the past two decades. The ability of SERMs to act as estrogens in certain tissues while remaining inert or acting as an anti-estrogen in other tissues has opened up opportunities for treating specific estrogen-modulated diseases without accepting the risk of systemic estrogen activity. SERM development has resulted in significant therapeutic advances for breast cancer, osteoporosis and potentially other diseases associated with the menopause. After the publication of the Women's Health Initiative, interest in compound selectivity that reduces menopausal symptoms while protecting bone, breast, uterus and the heart has increased. Future SERMs may also have a therapeutic profile that can be tailored to specific patient populations, including men. This review paper summarizes the characteristics of different SERMs from various pharmacological categories and the feasibility and scope of their use for a large range of disease/health conditions.

Clinical applications for estetrol

In this paper the potential clinical applications for the human fetal estrogen estetrol (E(4)) are presented based on recently obtained data in preclinical and clinical studies. In the past E(4) has been classified as a weak estrogen due to its rather low estrogen receptor affinity. However, recent research has demonstrated that due to its favorable pharmacokinetic properties, especially the slow elimination and long half-life, E(4) is an effective orally bioavailable estrogen agonist with estrogen antagonistic effects on the breast in the presence of estradiol. Based on the pharmacokinetic properties, the pharmacological profile and the safety and efficacy results in human studies, E(4) seems potentially suitable as a drug for human use in applications such as hormone replacement therapy (vaginal atrophy and vasomotor symptoms), contraception, osteoporosis and breast cancer.

Estetrol review: profile and potential clinical applications

In this review paper, the existing information on the human fetal steroid estetrol (E4) has been summarized. In the past, E4 was considered as a weak estrogen and interest disappeared. However, recent new research has demonstrated that E4 is a potent, orally bioavailable, natural human fetal selective estrogen receptor modulator, since it acts in the rat as an estrogen on all tissues investigated except breast tumor tissue, where it has estrogen antagonistic properties in the presence of estradiol. Based on its safety data, its pharmacokinetic properties, its pharmacological profile and the results of first human studies, E4 may be suitable as a potential drug for human use in applications such as hormone replacement therapy (vaginal atrophy, hot flushes), contraception and osteoporosis. Additional areas worth exploring are the treatment of breast and prostate cancer, hypoactive sexual desire disorder and topical use (wrinkles) in women, auto-immune diseases, migraine, cardiovascular applications and the treatment of selected obstetric disorders.