A new approach to menopausal therapy: the tissue selective estrogen complex

Anti-fibrotic effect of a selective estrogen receptor modulator in systemic sclerosis

Background

The rarity of systemic sclerosis (SSc) has hampered the development of therapies for this intractable autoimmune disease. Induced pluripotent stem cell (iPSC) can be differentiated into the key disease-affected cells in vitro. The generation of patient-derived iPSCs has opened up possibilities for rare disease modeling. Since these cells can recapitulate the disease phenotypes of the cell in question, they are useful high-throughput platforms for screening for drugs that can reverse these abnormal phenotypes.

Methods

SSc iPSC was generated from PBMC by Sendai virus. Human iPSC lines from SSc patients were differentiated into dermal fibroblasts and keratinocytes. The iPSC-derived differentiated cells from the SSc patients were used on high-throughput platforms to screen for FDA-approved drugs that could be effective treatments for SSc.

Results

Skin organoids were generated from these cells exhibited fibrosis that resembled SSc skin. Screening of the 770-FDA-approved drug library showed that the anti-osteoporotic drug raloxifene reduced SSc iPSC-derived fibroblast proliferation and extracellular matrix production and skin fibrosis in organoids and bleomycin-induced SSc-model mice.

Conclusions

This study reveals that a disease model of systemic sclerosis generated using iPSCs-derived skin organoid is a novel tool for in vitro and in vivo dermatologic research. Since raloxifene and bazedoxifene are well-tolerated anti-osteoporotic drugs, our findings suggest that selective estrogen receptor modulator (SERM)-class drugs could treat SSc fibrosis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-022-02987-w.

A comprehensive review on anticancer mechanism of bazedoxifene

Cancer is counted as a second leading cause of death among nontransmissible diseases. Identification of novel anticancer drugs is therefore necessary for the effective treatment of cancer. Conventional drug discovery is time consuming and expensive process. Unlike conventional drug discovery, drug repositioning offers a novel strategy for urgent drug discovery since it is a cost-effective and faster process. Bazedoxifene (BZA) is a synthetic selective estrogen receptor modulator, approved by the United States Food and Drug Administration for the treatment of osteoporosis in postmenopausal women. BZA is now being studied for its anticancer activity in various cancers including breast cancer, liver cancer, pancreatic cancer, colon cancer, head and neck cancer, medulloblastoma, brain cancer, and gastrointestinal cancer. Studies have reported that BZA is effective in reducing cancer progression through multiple mechanisms. BZA could effectively inhibit STAT3, PI3K/AKT, and MAPK signaling pathways and induce apoptosis. In addition to its anticancer activity as monotherapy, BZA has been shown to enhance the chemotherapeutic efficacy of clinical drugs such as paclitaxel, cisplatin, palbociclib, and oxaliplatin in multiple neoplasms. This review mainly focused on the anticancer activity, cellular targets, and anticancer mechanism of BZA, which may help the further design and conduct of research and repositioning it for oncological clinic trials.

Sex Hormones in Lymphedema

Simple Summary

Lymphedema is a life-long disease that affects a large number of patients treated for breast-, gynecological-, and urologic cancers in Western countries. Given that hormone levels are strongly modified in these conditions, and that patients widely undergo through hormone therapy, it is tempting to speculate that hormones might be key regulators in the maintenance of lymphedema. Despite an obvious prevalence for women, the role of sex hormones and gender has been poorly investigated in this pathology. This review aims to decipher how sex hormones interact with lymphatic vessels and whether hormone therapy could participate in lymphedema development.

Abstract

Lymphedema is a disorder of the lymphatic vascular system characterized by impaired lymphatic return resulting in swelling of the extremities and accumulation of undrained interstitial fluid/lymph that results in fibrosis and adipose tissue deposition in the limb. Whereas it is clearly established that primary lymphedema is sex-linked with an average ratio of one male for three females, the role of female hormones, in particular estrogens, has been poorly explored. In addition, secondary lymphedema in Western countries affects mainly women who developed the pathology after breast cancer and undergo through hormone therapy up to five years after cancer surgery. Although lymphadenectomy is identified as a trigger factor, the effect of co-morbidities associated to lymphedema remains elusive, in particular, estrogen receptor antagonists or aromatase inhibitors. In addition, the role of sex hormones and gender has been poorly investigated in the etiology of the pathology. Therefore, this review aims to recapitulate the effect of sex hormones on the physiology of the lymphatic system and to investigate whetherhormone therapy could promote a lymphatic dysfunction leading to lymphedema.

Effect of conjugated estrogens and bazedoxifene on glucose, energy and lipid metabolism in obese postmenopausal women

OBJECTIVE

Combining conjugated estrogens (CE) with the selective estrogen receptor modulator bazedoxifene (BZA) is a novel, orally administered menopausal therapy. We investigated the effect of CE/BZA on insulin sensitivity, energy metabolism, and serum metabolome in postmenopausal women with obesity.

DESIGN

Randomized, double-blind, crossover pilot trial with washout was conducted at Pennington Biomedical Research Center. Eight postmenopausal women (age 50-60 years, BMI 30-40 kg/m2) were randomized to 8 weeks CE/BZA or placebo. Primary outcome was insulin sensitivity (hyperinsulinemic-euglycemic clamp). Secondary outcomes included body composition (DXA); resting metabolic rate (RMR); substrate oxidation (indirect calorimetry); ectopic lipids (1H-MRS); fat cell size, adipose and skeletal muscle gene expression (biopsies); serum inflammatory markers; and serum metabolome (LC/MS).

RESULTS

CE/BZA treatment produced no detectable effect on insulin sensitivity, body composition, ectopic fat, fat cell size, or substrate oxidation, but resulted in a non-significant increase in RMR (basal: P = 0.06; high-dose clamp: P = 0.08) compared to placebo. CE/BZA increased serum high-density lipoprotein (HDL)-cholesterol. CE/BZA also increased serum diacylglycerol (DAG) and triacylglycerol (TAG) species containing long-chain saturated, mono- and polyunsaturated fatty acids (FAs) and decreased long-chain acylcarnitines, possibly reflecting increased hepatic de novo FA synthesis and esterification into TAGs for export into very low-density lipoproteins, as well as decreased FA oxidation, respectively (P < 0.05). CE/BZA increased serum phosphatidylcholines, phosphatidylethanolamines, ceramides, and sphingomyelins, possibly reflecting the increase in serum lipoproteins (P < 0.05).

CONCLUSIONS

A short treatment of obese postmenopausal women with CE/BZA does not alter insulin action or ectopic fat but increases serum markers of hepatic de novo lipogenesis and TAG production.

Postmenopausal hormone therapy in BRCA gene mutation carriers: to whom and which?

INTRODUCTION

Risk-reducing-salpingo-oophorectomy (RRSO) inevitably leads BRCA mutation carriers to premature menopause.

AREAS COVERED

To evaluate the existing evidence for use of postmenopausal hormone therapy (HT) in BRCAmc, after RRSO or menopause occurring naturally, for both breast cancer (BC) survivors and those without BC.

EXPERT OPINION

All BC survivors are excluded from any HT treatment: in other BRCAmc, before 51 years of age the benefits of HT overcome the risks after RRSO and/or premature ovarian insufficiency (POF). After 51 years of age, it is important to treat only women with important vasomotor symptoms, after the failure of alternative therapies. Estrogens-only therapy plays a key role in hysterectomized women (HW). In the case of an intact uterus (UW), associations with the lowest dose of progestins/natural progesterone derivatives have to be preferred, as progestins has been shown to play an important role in BC transformation, especially in BRCA1mc. No studies have been performed in BRCAmc with regard to 'progestin-free' HT, in particular the old tibolone (both in HW and UW) and the new tissue-selective estrogen complex (in UW). However, preliminary data obtained from the general population are reassuring about the use of these 'progestin-free' preparations and BC safety.

Conjugated Estrogens and Bazedoxifene Improve β Cell Function in Obese Menopausal Women

CONTEXT

Studies suggest that menopausal hormone therapy (MHT) prevents type 2 diabetes (T2D). The combination of conjugated estrogens (CE) with the selective estrogen receptor modulator bazedoxifene (BZA) is an MHT that improves obesity and T2D in preclinical models of menopausal metabolic syndrome. The effect of CE/BZA on adiposity and glucose homeostasis in obese postmenopausal women is unknown.

OBJECTIVE

To investigate the effect of CE/BZA on body composition, glucose homeostasis, and markers of inflammation in obese postmenopausal women.

RESEARCH DESIGN INTERVENTION AND PARTICIPANTS

Randomized, double-blind, placebo-controlled pilot trial of 12 obese menopausal women assigned to 12-week treatment with CE 0.45 mg/BZA 20 mg (n = 7) or placebo (n = 5). At baseline and after 12 weeks, we assessed body composition (dual-energy X-ray absorptiometry), glucose homeostasis (IV glucose tolerance test), and inflammation biomarkers.

RESULTS

Women treated with CE/BZA exhibited increased β cell function using homeostatic model assessment-B [median (interquartile range) CE/BZA vs placebo: 18.5 (-0.9 to 320.6) μU/mM vs -25.5 (-39.9 to -0.1) μU/mM; P = 0.045], and decreased basal glucose concentrations (Gb) [-5.2 (-9.2 to -1.7) mg/dL vs 2.7 (0.9 to 4.9) mg/dL; P = 0.029]. Insulin sensitivity was higher in the placebo arm [1.35 (1.12 to 1.82) (μU/mL) min-1 vs -0.24 (-1.50 to 0.19) (μU/mL) min-1; P = 0.029]. No changes between treatment groups were observed for the acute insulin response to glucose (AIRg), the disposition index (DI), body composition, and inflammatory biomarkers.

CONCLUSIONS

A 12-week treatment of obese postmenopausal women with CEs/BZA improves fasting β cell function and glucose concentrations without change in AIRg, HOMA-IR, DI, body composition, or markers of inflammation.

Estrogens Promote Misfolded Proinsulin Degradation to Protect Insulin Production and Delay Diabetes

Conjugated estrogens (CE) delay the onset of type 2 diabetes (T2D) in postmenopausal women, but the mechanism is unclear. In T2D, the endoplasmic reticulum (ER) fails to promote proinsulin folding and, in failing to do so, promotes ER stress and β cell dysfunction. We show that CE prevent insulin-deficient diabetes in male and in female Akita mice using a model of misfolded proinsulin. CE stabilize the ER-associated protein degradation (ERAD) system and promote misfolded proinsulin proteasomal degradation. This involves activation of nuclear and membrane estrogen receptor-α (ERα), promoting transcriptional repression and proteasomal degradation of the ubiquitin-conjugating enzyme and ERAD degrader, UBC6e. The selective ERα modulator bazedoxifene mimics CE protection of β cells in females but not in males.

The Role of Estrogens in Pancreatic Islet Physiopathology

In rodent models of insulin-deficient diabetes, 17β-estradiol (E2) protects pancreatic insulin-producing β-cells against oxidative stress, amyloid polypeptide toxicity, gluco-lipotoxicity, and apoptosis. Three estrogen receptors (ERs)-ERα, ERβ, and the G protein-coupled ER (GPER)-have been identified in rodent and human β-cells. This chapter describes recent advances in our understanding of the role of ERs in islet β-cell function, nutrient homeostasis, survival from pro-apoptotic stimuli, and proliferation. We discuss why and how ERs represent potential therapeutic targets for the maintenance of functional β-cell mass.

Preclinical breast effects of a tissue selective estrogen complex (TSEC) including conjugated estrogen with bazedoxifene

The first tissue-selective estrogen complex (TSEC), consisting of a combination of a conjugated equine estrogen (CEE) and bazedoxifene (BZA), has been approved for treatment of the menopause in the USA and European Union. We have postulated that this TSEC might block the estrogenic effects of CEE on breast tissue and thereby prevent breast cancer growth. This manuscript, representing a presentation at a Festschrift honoring Evan Simpson, reviews our published data BZA blocked the in vitro effects of both estradiol and CEE on cell growth and gene expression in MCF-7 cells. BZA completely blocked CEE- or E₂-stimulated ductal and terminal end bud growth of immature murine mammary glands and the growth of experimental breast cancers. These findings provide a rationale for future clinical studies to determine whether this TSEC prevents the growth of occult breast cancer in women.

The evolving role of oral hormonal therapies and review of conjugated estrogens/bazedoxifene for the management of menopausal symptoms

This review describes the evolving role of oral hormone therapy (HT) for treating menopausal symptoms and preventing osteoporosis, focusing on conjugated estrogens/bazedoxifene (CE/BZA). Estrogens alleviate hot flushes and prevent bone loss associated with menopause. In nonhysterectomized women, a progestin should be added to estrogens to reduce the risk of endometrial cancer. Use of HT declined since the Women's Health Initiative (WHI) studies showed that HT does not prevent coronary heart disease (CHD) and that conjugated estrogens/medroxyprogesterone acetate increased the risk of invasive breast cancer after nearly 5 years of use. However, re-analyses of the WHI data suggest that some risks (eg, CHD, all-cause mortality) may be reduced when HT is initiated in women <60 years of age and <10 years since menopause, compared with later. CE/BZA is the first menopausal HT without a progestogen for nonhysterectomized women. Instead, BZA, a selective estrogen receptor modulator, in combination with CE, protects against estrogenic effects on uterine and breast tissue. Data from 5 large, randomized clinical trials show that CE/BZA reduces hot flush frequency/severity, prevents bone loss, reduces bone turnover, improves the vaginal maturation index and ease of lubrication, and improves some measures of sleep and menopause-specific quality of life. In studies of up to 2 years, there was no increase in endometrial hyperplasia, vaginal bleeding, breast density, or breast pain/tenderness compared with placebo. Venous thromboembolism and stroke are risks of all estrogen-based therapies. The choice of HT should be individualized, with consideration of the risk/benefit profile and tolerability of therapy, as well as patient preferences.

The Tissue-Selective Estrogen Complex (Bazedoxifene/Conjugated Estrogens) for the Treatment of Menopause

The tissue-selective estrogen complex (TSEC) pairs conjugated estrogens (CE) with a selective estrogen receptor modulator (SERM), bazedoxifene acetate (BZA). A 2-year treatment with the TSEC improved vasomotor symptoms, quality of life, and vaginal atrophy in healthy postmenopausal women. In addition, the TSEC prevented vertebral and hip bone loss without increasing mammographic density, breast tenderness, the risk of myocardial infarction, stroke, or venous thromboembolism. Finally, the BZA 20 mg/CE 0.45 mg dose did not increase the risk of endometrial hyperplasia. Based on these findings, the TSEC can be considered as a first-line treatment for symptomatic postmenopausal women.

Role of Sex Steroids in β Cell Function, Growth, and Survival

The gonads have long been considered endocrine glands, producing sex steroids such as estrogens, androgens, and progesterone (P4) for the sole purpose of sexual differentiation, puberty, and reproduction. Reproduction and energy metabolism are tightly linked, however, and gonadal steroids play an important role in sex-specific aspects of energy metabolism in various physiological conditions. In that respect, gonadal steroids also influence the secretion of insulin in a sex-specific manner. This review presents a perspective on the physiological roles of estrogens, androgens, and P4 via their receptors in pancreatic β cells in the gender-specific tuning of insulin secretion. I also discuss potential gender-specific therapeutic avenues that this knowledge may open in the future.

Clinical update on the use of ospemifene in the treatment of severe symptomatic vulvar and vaginal atrophy

The physiological decrease in vaginal estrogens is accountable for the emergence of vulvar and vaginal atrophy (VVA) and its related symptoms such as vaginal dryness, dyspareunia, vaginal and/or vulvar irritation or itching, and dysuria. The repercussion of these symptoms on quality of life often makes it necessary to initiate treatment. Up until now, the treatments available included vaginal moisturizers and lubricants, local estrogens, and hormonal therapy. However, therapeutic options have now been increased with the approval of 60 mg ospemifene, the first nonhormonal oral treatment with an agonist effect on the vaginal epithelium and an endometrial and breast safety profile which makes it unique. This is the first selective estrogen receptor modulator indicated in women with moderate-to-severe vaginal atrophy not eligible for local estrogen treatment. Considering that "local estrogen noneligible women" are those in whom such treatment cannot be administered either because it is contraindicated or due to skill issues, who are averse to the mode and convenience of vaginal products' administration or to their use on account of potential systemic absorption, or those who demonstrate dissatisfaction in terms of efficacy and safety, it is clear that there is a significant unmet medical need in VVA management. In fact, a great number of women show lack of adherence, dropping out of at least one VVA treatment, including nonhormonal moisturizers and lubricants, which they consider to be ineffective and uncomfortable. If they could choose, many of them may opt for oral treatment. In Phase III studies, ospemifene demonstrated efficacy in vaginal dryness and dyspareunia, regenerating vaginal cells, improving lubrication, and reducing pain during sexual intercourse. Symptoms improved in the first 4 weeks and endured for up to 1 year. Additionally, it demonstrated a good endometrial, cardiovascular system, and breast safety profile.

Pooled Analysis of the Effects of Conjugated Estrogens/Bazedoxifene on Vasomotor Symptoms in the Selective Estrogens, Menopause, and Response to Therapy Trials

OBJECTIVES

Conjugated estrogens/bazedoxifene (CE/BZA) reduced menopause-related hot flashes (HFs) in the Selective estrogens, Menopause, And Response to Therapy (SMART) trials. This post hoc pooled analysis of SMART-1 and -2 further characterized effects of CE/BZA on HFs in the overall population and patient subgroups.

METHODS

Data from two randomized, double-blind, placebo- and active-controlled, phase 3 studies were pooled for nonhysterectomized postmenopausal women with moderate/severe HFs given CE 0.45 mg/BZA 20 mg, CE 0.625 mg/BZA 20 mg, or placebo for 12 weeks. HF frequency and severity were assessed by daily diary.

RESULTS

The pooled analysis included 403 participants. At 12 weeks, CE 0.45 mg/BZA 20 mg and CE 0.625 mg/BZA 20 mg significantly (all p < 0.001) decreased moderate/severe HF frequency versus placebo (-7.9, -8.2, -4.1), reduced adjusted average daily HF severity score versus placebo (-1.0, -1.3, -0.3), increased the percentage of women who had a ≥50% (81.2%,87.1%, 50.6%) and ≥75% (62.4%, 74.8%, 26.4%) reduction from baseline in daily frequency of moderate/severe HFs, increased the percentage with ≥50% (38.3%, 58.1%, 11.0%) and ≥75% (24.2%, 38.1%, 5.5%) reductions in average daily HF severity score, and improved MENQOL vasomotor function versus placebo (adjusted mean change-3.08, -3.69, -1.37). CE/BZA was significantly more effective than placebo irrespective of time since menopause, with some evidence of a lower placebo response in women in later menopause (>5 years) versus early menopause (≤5 years).

CONCLUSIONS

CE/BZA effectively reduces moderate/severe HFs in postmenopausal women. NCT#'s: NCT00675688; NCT00234819.

Progestogen safety and tolerance in hormonal replacement therapy

INTRODUCTION

Today, it is a mandatory practice to prescribe a combination of estrogens and progestogens for menopausal women requiring hormone therapy and with a uterus. The WHI study and its reanalysis demonstrate a big difference in results between the conjugated equin estrogen (CEE) only vs.CEE plus medroxyprogesterone acetate (MPA) arms in relation with breast cancer and cardiovascular risk. The conclusion is that risk is clearly higher in the arm with MPA than in the CEE only arm. Although the only progestogen used in the WHI study was medroxyprogesterone acetate, side effects and intolerance have been extrapolated as a class effect to all progestogens. Areas covered: Progestogen tolerance and side effects in hormone therapy were reviewed. For that purpose, a limited literature search was conducted on key resources including Pubmed, the Cochrane Library, ECRI, and major international health technology agencies. Expert opinion: Many of the tolerance effects are based on limited data. There are no double-blind randomized trials comparing long-term safety for breast cancer and cardiovascular risk among different progestogens. Short-term clinical studies, observational, and in animal and in vitro studies indicate that both micronized progesterone and dydrogesterone are the safer progestogens with an acceptable metabolic profile.

Ovariectomy shortens the life span of female mice

This study shows that lack of ovarian activity has a negative impact on the life span of female mice. The extent to which this phenomenon could be associated with the anti-inflammatory effect of estrogens was analyzed in metabolic organs and aorta, by quantitative analysis of mRNAs encoding proteins in the inflammatory cascade. We demonstrate that the TNFα, IL-1β, MCP-1, MIP-2 and IL-6 mRNA contents are increased in the liver, adipose tissue and aorta 7 months after ovariectomy (ovx) and this increased basal inflammation is maintained as the mice aged. In contrast, the extent of inflammatory gene expression is directly proportional to age in sham-operated mice. As a consequence, at 22 months, most of the inflammatory parameters examined were higher in the sham-operated group compared with the ovx group. These observations led us to propose that the decreased longevity of ovx mice may be due to an acceleration of the basal state of inflammation in metabolic organs, which is likely driven by the combination of a lack of estrogen-mediated anti-inflammatory activity and the loss of gonadal control of energy metabolism.

Effects of genistein in combination with conjugated estrogens on endometrial hyperplasia and metabolic dysfunction in ovariectomized mice

Tissue-selective estrogen complex (TSEC), which combines a selective estrogen receptor modulator (SERM) with one or more estrogens, is a novel approach to menopausal therapy. It has been demonstrated that the phytoestrogen genistein (GEN) exhibits mixed estrogen receptor agonist and antagonist activity, suggesting that GEN may have potential for use as a natural SERM. We evaluated, for the first time, the effects of GEN, conjugated estrogens (CE), and their pairing effects as a TSEC treatment on estrogen-induced endometrial hyperplasia and metabolic dysfunction in ovariectomized (OVX) mice fed a high-fat diet. CE replacement prevented fat accumulation in the adipose tissue and liver, improved glucose homeostasis, and induced endometrial hyperplasia in OVX mice. GEN at 100 mg/kg showed CE mimetic effects in preventing ovariectomy-induced metabolic dysfunctions without endometrial stimulation. Combination treatments with CE and GEN prevented metabolic dysfunctions more strongly than CE alone, but at both low and high doses, GEN did not reverse CE-induced endometrial hyperplasia. In addition, we found that in a TSEC regimen, a typical SERM raloxifene maintains the metabolic benefits of CE while simultaneously protecting the endometrium in OVX mice. These findings indicate that GEN acts as an estrogen agonist in metabolic regulation, but has no SERM function in the uteri of OVX mice.

Development of conjugated estrogens/bazedoxifene, the first tissue selective estrogen complex (TSEC) for management of menopausal hot flashes and postmenopausal bone loss

Conjugated estrogens (CE) combined with the selective estrogen receptor modulator (SERM) bazedoxifene (BZA) is a new option for alleviating menopausal symptoms and preventing postmenopausal bone loss. The rationale for developing the tissue selective estrogen complex (TSEC) CE/BZA was to combine CE's benefits with the SERM's tissue-specific properties to offset estrogenic stimulation of endometrial and breast tissue. TSECs provide a progestin-free alternative to traditional estrogen-progestin therapy (EPT) in women with a uterus. Preclinical studies supported bazedoxifene as the SERM of choice and demonstrated that CE/BZA provided an optimal balance of estrogen receptor agonist/antagonist activity compared with other potential TSEC pairings. Initial clinical development of CE/BZA focused on determining the appropriate dose ratio that would demonstrate efficacy with minimal to no stimulation of the breast or endometrium. Clinical studies confirmed the efficacy of the selected doses for maintaining bone mass; relieving vasomotor symptoms, vulvar-vaginal atrophy, and dyspareunia; and improving sexual function in postmenopausal women. Reduction of hot flashes also translated into improved menopause-specific quality of life and sleep. Unlike EPT, the FDA-approved dose of CE 0.45 mg/BZA 20mg does not cause a change in breast density or the endometrium, or increase breast pain compared with placebo. In clinical trials up to 2 years, CE 0.45 mg/BZA 20 mg has a favorable tolerability profile and rates of coronary heart disease, venous thromboembolism, and amenorrhea similar to placebo. Therefore, CE 0.45 mg/BZA 20 mg is an effective, well-tolerated alternative to EPT for menopausal symptom relief and osteoporosis prevention for postmenopausal women with a uterus.

Conjugated estrogen/bazedoxifene tablets for the treatment of moderate-to-severe vasomotor symptoms associated with menopause

Conjugated estrogen/bazedoxifene (CE/BZA) therapy represents a new, progestin-free treatment in the management of postmenopausal health. CE/BZA pairs CE with the selective estrogen receptor modulator, BZA. The rationale for the development of CE/BZA was that BZA, acting primarily as a selective estrogen receptor degrader in uterine and breast tissue, would sufficiently inhibit the proliferative effects of CE on the endometrium. The absence of a progestin would reduce the incidence of uterine bleeding, breast pain and increased breast density associated with progestin-containing hormone therapy. CE/BZA has been evaluated in five multicenter, randomized, double-blind, placebo-controlled, and active-controlled Phase III trials known as the SMART trials. CE/BZA has been shown to maintain the established benefits of estrogen therapy for treatment of vasomotor symptoms and prevention of a loss in bone mineral density (bone mass), while minimizing certain estrogenic effects, particularly in the uterine endometrium and breast.

Selective estrogen receptor modulators: tissue specificity and clinical utility

Selective estrogen receptor modulators (SERMs) are a diverse group of nonsteroidal compounds that function as agonists or antagonists for estrogen receptors (ERs) in a target gene-specific and tissue-specific fashion. SERM specificity involves tissue-specific expression of ER subtypes, differential expression of co-regulatory proteins in various tissues, and varying ER conformational changes induced by ligand binding. To date, the major clinical applications of SERMs are their use in the prevention and treatment of breast cancer, the prevention of osteoporosis, and the maintenance of beneficial serum lipid profiles in postmenopausal women. However, SERMs have also been found to promote adverse effects, including thromboembolic events and, in some cases, carcinogenesis, that have proven to be obstacles in their clinical utility. In this review, we discuss the mechanisms of SERM tissue specificity and highlight the therapeutic application of well-known and emergent SERMs.

Effects of bazedoxifene/conjugated estrogens on the endometrium and bone: a randomized trial

OBJECTIVE

This phase 3 study evaluated the endometrial safety of bazedoxifene (BZA)/conjugated estrogens (CE) and bone mineral density (BMD) effects vs BZA alone, hormone therapy, and placebo (PBO).

METHODS

The Selective estrogens, Menopause, And Response to Therapy (SMART)-5 trial was a multicenter, randomized, double-blind, PBO- and active-controlled study in postmenopausal women with an intact uterus (N = 1843; aged 40-65 years) seeking treatment for menopausal symptoms. Subjects received daily oral BZA 20 mg/CE 0.45 or 0.625 mg, BZA 20 mg, CE 0.45 mg/medroxyprogesterone acetate (MPA) 1.5 mg, or PBO. Primary endpoints were incidence of endometrial hyperplasia and percent change in lumbar spine BMD at 12 months. Secondary endpoints included additional osteoporosis parameters and assessments of tolerability and safety.

RESULTS

At 12 months, endometrial hyperplasia incidence was low (<1%) and similar among groups. The BZA/CE group showed significantly greater increases in lumbar spine and total hip BMD vs decreases with PBO (P < .001); the CE/MPA group had increased lumbar spine BMD compared with that in the BZA/CE group. The BZA 20 mg/CE 0.45 and 0.625 mg groups had cumulative amenorrhea rates similar to those with PBO and BZA and significantly higher than those with CE 0.45 mg/MPA 1.5 mg (P < .001). The incidence of breast tenderness with BZA/CE was similar to that with PBO and BZA and significantly lower than with that with CE/MPA (P < .01). Although adverse event (AE) rates were similar among the groups, the incidence of serious AEs overall and AE-related discontinuation rates were higher with CE/MPA than with BZA/CE, BZA, or PBO.

CONCLUSIONS

BZA/CE showed low rates of endometrial hyperplasia and improved lumbar spine and total hip BMD and was generally safe and well tolerated.

Endometrial profile of bazedoxifene acetate alone and in combination with conjugated equine estrogens in a primate model

OBJECTIVE

Concerns of breast cancer risk in postmenopausal women taking combined estrogen + progestin therapy have generated interest in the use of selective estrogen receptor modulators (SERMs) as potential progestin alternatives. Endometrial proliferation and cancer risk are major concerns, however, for estrogens and certain types of SERMs when given alone. The primary aim of this study was to evaluate the endometrial profile of bazedoxifene acetate (BZA), a third-generation SERM, alone and in combination with conjugated equine estrogens (CEE) in a postmenopausal primate model.

METHODS

Ninety-eight ovariectomized cynomolgus monkeys (Macaca fascicularis) were randomized to receive no hormone treatment (controls), BZA 20 mg, CEE 0.45 mg, or the combination of BZA 20 mg + CEE 0.45 mg once daily for 20 months in a parallel-arm study design. The primary outcome measure was endometrial epithelial proliferation.

RESULTS

BZA + CEE and BZA treatment resulted in significantly less endometrial epithelial area and Ki67 expression compared with CEE (P < 0.001 for all). The prevalence of endometrial hyperplasia and other estrogen-induced morphologic changes in the BZA + CEE and BZA groups was not significantly different from controls. The addition of BZA to CEE completely inhibited the expression of estrogen receptor-α-regulated genes (TFF1 and PGR), whereas BZA alone had no effect. BZA + CEE and BZA treatment also resulted in lower estrogen receptor-α protein expression in the endometrium compared with the control and CEE groups (P < 0.05 for all).

CONCLUSIONS

BZA given at a clinically relevant dose inhibits estrogen effects on the endometrium and lacks uterotropic effects when given alone.

Tissue-selective estrogen complexes with bazedoxifene prevent metabolic dysfunction in female mice

Pairing the selective estrogen receptor modulator bazedoxifene (BZA) with estrogen as a tissue-selective estrogen complex (TSEC) is a novel menopausal therapy. We investigated estrogen, BZA and TSEC effects in preventing diabetisity in ovariectomized mice during high-fat feeding. Estrogen, BZA or TSEC prevented fat accumulation in adipose tissue, liver and skeletal muscle, and improved insulin resistance and glucose intolerance without stimulating uterine growth. Estrogen, BZA and TSEC improved energy homeostasis by increasing lipid oxidation and energy expenditure, and promoted insulin action by enhancing insulin-stimulated glucose disposal and suppressing hepatic glucose production. While estrogen improved metabolic homeostasis, at least partially, by increasing hepatic production of FGF21, BZA increased hepatic expression of Sirtuin1, PPARα and AMPK activity. The metabolic benefits of BZA were lost in estrogen receptor-α deficient mice. Thus, BZA alone or in TSEC produces metabolic signals of fasting and caloric restriction and improves energy and glucose homeostasis in female mice.

Energy metabolism and fertility: a balance preserved for female health

In female animals, energy metabolism and fertility are tightly connected, and reciprocally regulated. However, the relative contributions of metabolic and reproductive pathways have changed over the course of evolution. In oviparous animals, metabolic factors take precedence over fertility, enabling egg production to be inhibited in a nutritionally poor environment. By contrast, in placental mammals, the opposite occurs: the need to feed a developing embryo and neonate forces metabolic pathways to adapt to these reproductive needs. This physiological necessity explains why in female mammals alterations of gonadal activity, including age-dependent cessation of ovarian functions, are associated with a disruption of metabolic homeostasis and consequent inflammatory reactions that trigger the onset of metabolic, cardiovascular, skeletal and neural pathologies. This Review discusses how metabolic homeostasis and reproductive functions interact to optimize female fertility and explains the pathogenic mechanisms underlying the disordered energy metabolism associated with human ovarian dysfunction owing to menopause, polycystic ovary syndrome and Turner syndrome. Finally, this article highlights how hormone replacement therapy might aid the restoration of metabolic homeostasis in women with ovarian dysfunction.

Management of osteoporosis and menopausal symptoms: focus on bazedoxifene/conjugated estrogen combination

Loss of estrogen production in women during menopause results in a state of estrogen deficiency which has been associated with multiple problems, including vasomotor symptoms, symptoms of vulvovaginal atrophy, bone loss, and difficulties with sleep, mood, memory, and sexual activity. The only treatment option currently available to address multiple postmenopausal symptoms in women with an intact uterus is estrogen/progestin-containing hormone therapy (HT). Concerns surrounding side effects and published data regarding the association of HT with the increased risk for breast cancer have induced a decrease in the number of women seeking, initiating, and continuing this type of therapy. A combination containing bazedoxifene and conjugated estrogens (BZA/CE) maintains the established benefits of estrogen therapy for treatment of postmenopausal vasomotor symptoms, vulvovaginal atrophy, and osteoporosis, while certain estrogenic effects, such as stimulation of the uterus and breast, are antagonized without the side effects associated with HT. BZA/CE has been evaluated in a series of multicenter, randomized, double-blind, placebo-controlled, and active-controlled Phase III trials known as the Selective estrogens, Menopause, And Response to Therapy (SMART) trials. BZA/CE demonstrated clinically meaningful improvements in vasomotor symptoms, vulvovaginal atrophy, and a protective effect on the skeleton. These clinical benefits were associated with an acceptable safety profile and an improved tolerability compared with HT. BZA/CE showed a favorable safety profile on the breast, endometrium, and ovaries. The incidence of venous thromboembolism was low and the risk does not appear to be any greater than for CE alone or BZA alone or greater than HT. The incidence of coronary heart disease and cerebrovascular accidents were similar to placebo. The overall incidence of cancer (including breast cancer) was low and similar to placebo. The SMART trials demonstrate that BZA/CE is an alternative option for treating non-hysterectomized, symptomatic, postmenopausal women.

Profile of bazedoxifene/conjugated estrogens for the treatment of estrogen deficiency symptoms and osteoporosis in women at risk of fracture

Decreasing levels of estrogens during menopause are associated with reduced bone density and an increased risk of osteoporosis. Many women also experience bothersome vasomotor and vaginal symptoms during the menopausal transition. Results of systematic reviews and meta-analyses of randomized controlled trials have shown that both systemic estrogen therapy or hormone therapy (estrogen combined with a progestin) are useful to prevent bone loss, and they are the most effective treatment for such climacteric symptoms as hot flushes, sweating, vaginal dryness, and dyspareunia. Unfortunately, estrogen therapy and hormone therapy increase the risk of endometrial and breast cancer, respectively. The selective estrogen receptor modulators (SERMs) result in positive estrogenic effects on bone, with no negative effects on the endometrium and breast but do not provide relief from postmenopausal symptoms. The combination of a SERM with estrogen as a tissue selective estrogen complex (TSEC) is a new strategy for the prevention of bone loss and the treatment of climacteric symptoms. This combination is particularly interesting from a clinical point of view, taking into account that estrogen alone did not increase breast cancer risk by the Women’s Health Initiative. TSEC is hypothesized to provide the benefits of estrogen-alone therapy, with an improved tolerability profile because the SERM component can make possible the elimination of progestin. The objective of this review was to critically evaluate the evidence from the reports published to date on the use of bazedoxifene (a third-generation SERM) in combination with conjugated estrogens in postmenopausal women. The conclusion is that effectively, the combination of bazedoxifene and conjugated estrogens may be a promising alternative to hormone therapy for the prevention of osteoporosis and the treatment of postmenopausal symptoms in non-hysterectomized postmenopausal women.

The role of estrogens in control of energy balance and glucose homeostasis

Estrogens play a fundamental role in the physiology of the reproductive, cardiovascular, skeletal, and central nervous systems. In this report, we review the literature in both rodents and humans on the role of estrogens and their receptors in the control of energy homeostasis and glucose metabolism in health and metabolic diseases. Estrogen actions in hypothalamic nuclei differentially control food intake, energy expenditure, and white adipose tissue distribution. Estrogen actions in skeletal muscle, liver, adipose tissue, and immune cells are involved in insulin sensitivity as well as prevention of lipid accumulation and inflammation. Estrogen actions in pancreatic islet β-cells also regulate insulin secretion, nutrient homeostasis, and survival. Estrogen deficiency promotes metabolic dysfunction predisposing to obesity, the metabolic syndrome, and type 2 diabetes. We also discuss the effect of selective estrogen receptor modulators on metabolic disorders.

Effects of bazedoxifene acetate with and without conjugated equine estrogens on the breast of postmenopausal monkeys

OBJECTIVE

Concerns about increased breast cancer risk with estrogen and progestin therapy have led to an increased interest in progestin alternatives. The main objective of this study was to determine if bazedoxifene acetate (BZA), a new selective estrogen receptor modulator, will antagonize the proliferative and transcriptional effects of conjugated equine estrogens (CEE) in the breast.

METHODS

As part of a 20-month preclinical trial, 95 ovariectomized cynomolgus macaques (Macaca fascicularis) were randomized to receive no treatment or treatment with BZA (20 mg/d), CEE (0.45 mg/d), or BZA and CEE in combination (women's daily equivalent doses). The data presented here include breast effects after 6 months of treatment. Endpoints included histomorphometry, histopathological evaluations, gene microarray assays, polymerase chain reaction quantification of specific estrogen receptor α (ER-α) activity markers, and immunohistochemical detection of sex steroid receptors, and the proliferation marker Ki67.

RESULTS

BZA + CEE and BZA resulted in significantly less total epithelial density, lobular enlargement, and Ki67 immunolabeling in the terminal ducts compared with CEE alone (P < 0.05 for all). The addition of BZA to CEE antagonized the expression of ER-α-regulated genes such as GREB1 and TFF1 (P < 0.01 for both), whereas BZA alone had minimal effects on ER-α-mediated transcriptional activity. BZA and BZA + CEE did not significantly up-regulate genes related to cell cycle progression and proliferation. BZA with and without CEE also resulted in less lobular and terminal duct ER-α immunolabeling compared with control and CEE (P < 0.0001 for all).

CONCLUSIONS

These findings demonstrate that BZA given at a clinically relevant dose is an estrogen antagonist in the breast, supporting the idea that CEE + BZA may provide a lower breast cancer risk profile compared with traditional estrogen + progestin therapies.

Inhibitory effects of a bazedoxifene/conjugated equine estrogen combination on human breast cancer cells in vitro

Breast cancer incidence is increased in women receiving menopausal hormone therapy with estrogen plus progestin but not with estrogen alone. The use of a tissue-selective estrogen complex (TSEC) has been proposed as a novel menopausal hormone therapy strategy to eliminate the requirement for a progestogen. Combination of bazedoxifene (BZA) with conjugated estrogens (CEs), the first TSEC, has shown beneficial effects. Whether it would exert antiestrogenic effects on breast cancer is not clear. To address this issue, we compared estradiol (E(2)) and CE alone on proliferation and apoptosis in MCF-7 breast cancer cells. CE stimulated growth of MCF-7 cells at a peak concentration 10-fold higher than required for E(2). Both CE and E(2) alone increased DNA synthesis and reduced apoptosis with activation of MAPK, Akt, and p70S6K and up-regulation of antiapoptotic factors survivin, Bcl-2, and X-linked inhibitor of apoptosis protein, These effects could be completely blocked by BZA. Gene expression studies demonstrated that CE and E(2) were equally potent on expression of cMyc, pS2, and WNT1 inducible signaling pathway protein 2, whereas the stimulatory effects of CE on progesterone receptor and amphiregulin expression were weaker than E(2). BZA effectively blocked each of these effects and showed no estrogen agonistic effects when used alone. Our results indicate that the stimulatory effects of E(2) or CE on breast cancer cells could be completely abrogated by BZA. These studies imply that the CE/BZA, TSEC, exerts antiestrogenic effects on breast cancer cells and might block the growth of occult breast neoplasms in postmenopausal women, resulting in an overall reduction in tumor incidence.

Effects of the conjugated equine estrogen/bazedoxifene tissue-selective estrogen complex (TSEC) on mammary gland and breast cancer in mice

A tissue-selective estrogen complex (TSEC), combining a selective estrogen receptor modulator, bazedoxifene (BZA), with conjugated equine estrogen (CEE), represents a novel strategy of menopausal hormone therapy without involving a progestin. We hypothesized that the antiestrogenic properties of BZA can also block the estrogenic effects of CEE on breast tissue and thereby prevent breast cancer in women. To test our hypothesis, the effects of estradiol (E(2)), CEE, and BZA on mammary gland and breast cancer xenografts were assessed in mouse models. In immature castrate mice, BZA completely blocked CEE- or E(2)-stimulated ductal and terminal end bud growth of mammary gland as well as estrogen-responsive gene expression. As a positive control, E(2) stimulated tumor growth in nude mice bearing MCF-7 xenografts. This effect was completely blocked by BZA as were E(2)-stimulated expression of PR, pS2 (trefoil factor 1), cMyc, and AREG; the enhancement of Ki67 and proliferating cell nuclear antigen (PCNA); and the antiapoptotic effect. CEE was much less potent than E(2) in stimulating Ki67, reducing apoptosis, and stimulating gene expression, but all effects were blocked by BZA. Unexpectedly, CEE alone, even at high doses, did not stimulate tumor growth. As confirmation of its absorption and deconjugation, CEE caused a 6-fold increase in uterine weight and stimulation of gene expression. These data support our hypothesis that the net effect of the CEE/BZA TSEC is to block estrogen action in benign and malignant breast tissue. These findings provide a rationale for a clinical study to determine whether this TSEC prevents breast cancer in women.

The tissue selective estrogen complex: a promising new menopausal therapy

Menopause is associated with health concerns including vasomotor symptoms, vulvar/vaginal atrophy (VVA), and osteoporosis. Estrogen therapy or combined estrogen-progestin therapy (EPT) are primary treatment options for menopausal symptom relief and osteoporosis prevention. Because EPT has been associated with some safety/tolerability concerns relating to undesirable effects of estrogen and progestin, alternative options are needed. The tissue selective estrogen complex (TSEC) is a novel class of agents pairing a selective estrogen receptor modulator (SERM) with 1 or more estrogens. The TSEC combines the established efficacy of estrogens on menopausal symptoms and bone with the protective effects of a SERM on the reproductive tract. The pairing of bazedoxifene (BZA) with conjugated estrogens (CE) has been evaluated in a series of phase 3 clinical trials. BZA 20 mg/CE 0.45 mg and BZA 20 mg/CE 0.625 mg have shown efficacy in reducing the frequency and severity of hot flushes, relieving VVA symptoms, and maintaining bone mass while protecting the endometrium and breast. These BZA/CE doses have been associated with a favorable safety/tolerability profile, with higher rates of cumulative amenorrhea and lower incidences of breast pain than those reported for EPT. Thus, BZA/CE may be a promising alternative to conventional EPT for treating non-hysterectomized, postmenopausal women.

Bazedoxifene: the evolving role of third-generation selective estrogen-receptor modulators in the management of postmenopausal osteoporosis

Osteoporosis is a significant public health concern, particularly for postmenopausal women. Current treatment options may not be appropriate for all women. Selective estrogen-receptor modulators (SERMs) are a class of molecules with tissue-selective activity. Bazedoxifene is currently in clinical development for the prevention and treatment of postmenopausal osteoporosis. In a 2-year, phase III, osteoporosis prevention study (N = 1583), bazedoxifene 10, 20, and 40 mg was shown to preserve bone mineral density and decrease biochemical markers of bone turnover compared with placebo in postmenopausal women at risk for osteoporosis. In a pivotal 3-year, phase III, osteoporosis treatment study (N = 7492), bazedoxifene 20 and 40 mg significantly reduced the incidence of new vertebral fractures compared with placebo (p < 0.05 for both) in postmenopausal women with osteoporosis. In a post hoc subgroup analysis of women at higher risk for fracture (n = 1772), bazedoxifene 20 mg significantly reduced the risk of nonvertebral fractures versus placebo (p = 0.02) and raloxifene 60 mg (p = 0.05). Bazedoxifene 20 mg has demonstrated sustained efficacy in reducing the risk of vertebral fractures over 5 and 7 years. Overall, bazedoxifene was generally safe and well tolerated, with favorable endometrial and breast safety profiles. As with other SERMs, the rate of deep vein thrombosis was higher in the bazedoxifene groups compared with placebo at 3 and 5 years. Considering its demonstrated efficacy and safety, bazedoxifene may be an appropriate osteoporosis therapy for women who cannot take or are unwilling to take bisphosphonates because of safety or tolerability issues. Bazedoxifene may also be appropriate for younger women at increased fracture risk who are concerned about the effects of long-term bisphosphonate therapy. This article reviews the results of key clinical trials of bazedoxifene for the prevention and treatment of postmenopausal osteoporosis and describes its role in clinical practice.

Research resource: Transcriptional profiling in a cellular model of breast cancer reveals functional and mechanistic differences between clinically relevant SERM and between SERM/estrogen complexes

Exploitation of the relationship between estrogen receptor (ER) structure and activity has led to the development of 1) selective ER modulators (SERM), compounds whose relative agonist/antagonist activities differ between target tissues; 2) selective ER degraders (SERD), compounds that induce a conformational change in the receptor that targets it for proteasomal degradation; and 3) tissue-selective estrogen complexes (TSEC), drugs in which a SERM and an ER agonist are combined to yield a blended activity that results in distinct clinical profiles. In this study, we have performed a comprehensive head-to-head analysis of the transcriptional activity of these different classes of ERM in a cellular model of breast cancer. Not surprisingly, these studies highlighted important functional differences and similarities among the existing SERM, selective ER degraders, and TSEC. Of particular importance was the identification of genes that were regulated by various TSEC combinations but not by an estrogen or SERM alone. Cumulatively, the findings of this analysis are informative with respect to the mechanisms by which ER is engaged by different enhancers/promoters and highlights how promoter context influences the pharmacological activity of ER ligands.

Importance of oestrogen receptors to preserve functional β-cell mass in diabetes

Protecting the functional mass of insulin-producing β cells of the pancreas is a major therapeutic challenge in patients with type 1 (T1DM) or type 2 diabetes mellitus (T2DM). The gonadal hormone 17β-oestradiol (E2) is involved in reproductive, bone, cardiovascular and neuronal physiology. In rodent models of T1DM and T2DM, treatment with E2 protects pancreatic β cells against oxidative stress, amyloid polypeptide toxicity, lipotoxicity and apoptosis. Three oestrogen receptors (ERs)--ERα, ERβ and the G protein-coupled ER (GPER)--have been identified in rodent and human β cells. Whereas activation of ERα enhances glucose-stimulated insulin biosynthesis, reduces islet toxic lipid accumulation and promotes β-cell survival from proapoptotic stimuli, activation of ERβ increases glucose-stimulated insulin secretion. However, activation of GPER protects β cells from apoptosis, raises glucose-stimulated insulin secretion and lipid homeostasis without affecting insulin biosynthesis. Oestrogens are also improving islet engraftment in rodent models of pancreatic islet transplantation. This Review describes developments in the role of ERs in islet insulin biosynthesis and secretion, lipid homeostasis and survival. Moreover, we discuss why and how enhancing ER action in β cells without the undesirable effect of general oestrogen therapy is a therapeutic avenue to preserve functional β-cell mass in patients with diabetes mellitus.