The effects of combined raloxifene and oral estrogen on vasomotor symptoms and endometrial safety

Guideline No. 451: Asymptomatic Endometrial Thickening in Postmenopausal Women

OBJECTIVE

To formulate strategies for clinical assessments for endometrial thickening on ultrasound in a postmenopausal woman without bleeding.

TARGET POPULATION

Postmenopausal women of any age.

OUTCOMES

To reduce unnecessary invasive interventions and investigations in women with asymptomatic endometrial thickening while selectively investigating women at risk for endometrial cancer.

BENEFITS, HARMS, AND COSTS

It is anticipated that the adoption of these recommendations would save postmenopausal women unnecessary anxiety, pain, and risk of procedural complications. It is also expected to decrease the cost to the health care system by eliminating unnecessary interventions.

EVIDENCE

English language articles from Medline, Cochrane, and PubMed databases for relevant peer-reviewed articles dating from 1995 to 2022 (e.g., asymptomatic endometrial thickness, endometrial cancer, postmenopausal bleeding, transvaginal ultrasound, endometrial biopsy, cervical stenosis, hormone therapies and the endometrium, tamoxifen, tibolone, aromatase inhibitors). Results were restricted to systematic reviews and meta-analyses, randomized controlled trials/controlled clinical trials, and observational studies.

VALIDATION METHODS

The authors rated the quality of evidence and strength of recommendations using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach. See Appendix A (Tables A1 for definitions and A2 for interpretations of strong and conditional [weak] recommendations).

INTENDED AUDIENCE

Physicians, including gynaecologists, obstetricians, family physicians, radiologists, pathologists, and internists; nurse practitioners and nurses; medical trainees, including medical students, residents, and fellows; and other providers of health care of the postmenopausal population.

SOCIAL MEDIA ABSTRACT

Postmenopausal women often have a thickening of the lining of the uterus found during ultrasound. Without bleeding, an endometrium <11 mm is rarely a serious problem but should be evaluated by a health care provider.

SUMMARY STATEMENTS

RECOMMENDATIONS.

Small molecule targeted therapies for endometrial cancer: progress, challenges, and opportunities

Endometrial cancer (EC) is a common malignancy among women worldwide, and its recurrence makes it a common cause of cancer-related death. Surgery and external radiation, chemotherapy, or a combination of strategies are the cornerstone of therapy for EC patients. However, adjuvant treatment strategies face certain drawbacks, such as resistance to chemotherapeutic drugs; therefore, it is imperative to explore innovative therapeutic strategies to improve the prognosis of EC. With the development of pathology and pathophysiology, several biological targets associated with EC have been identified, including PI3K/Akt/mTOR, PARP, GSK-3β, STAT-3, and VEGF. In this review, we summarize the progress of small molecule targeted therapies in terms of both basic research and clinical trials and provide cases of small molecules combined with fluorescence properties in the clinical applications of integrated diagnosis and treatment. We hope that this review will facilitate the further understanding of the regulatory mechanism governing the dysregulation of oncogenic signaling in EC and provide insights into the possible future directions of targeted therapeutic regimens for EC treatment by developing new agents with fluorescence properties for the clinical applications of integrated diagnosis and treatment.

Effects of a Whole Plant Extract of Scutellaria rubropunctata var. rubropunctata on Bone Metabolism with Estrogen Receptor Activation

We screened natural resources for estrogen receptor (ER)-activating and bone metabolism-promoting activities with the aim of finding potential treatments for osteoporosis. A screen of 1531 extracts from Ryukyu Arc plants using a luciferase reporter assay identified an 80% MeOH extract of Scutellaria rubropunctata var. rubropunctata (SRE) with dose-dependent ER transcription-promoting activity. Importantly, SRE had no proliferative effect on human breast cancer cells. SRE enhanced the ALP activity of pre-osteoblast MC3T3-E1 cells after 72 h in culture and slightly enhanced mineralization at 14 and 21 d. SRE did not significantly affect the TRAP activity of RAW264.7 cells. Gene expression analysis in MC3T3-E1 cells by quantitative real-time PCR revealed that SRE upregulated the mRNA levels of Runx2, Osterix (Osx), Osteopontin (Opn), Osteocalcin (Ocn), Smad1, Smad4, and Smad5 at 72 h, and those of Runx2, Osx, Smad1, Smad4, and Smad5 at 21 d of osteogenic induction. Analysis of the expression levels of osteogenic markers suggested that SRE may promote osteogenic differentiation by acting at the early stage of differentiation rather than at the late stage of differentiation. These results indicate that SRE activates ER and induces osteoblast differentiation by activating Runx2 and Osx through the BMP/Smad pathway, suggesting that SRE may be useful for the prevention and treatment of postmenopausal osteoporosis.

Selective Estrogen Receptor Modulators in Gynecology Practice

Selective estrogen receptor (ER) modulators have variable tissue specific estrogen agonist and antagonist activities. Tamoxifen is approved for treatment and prevention of breast cancer; acts as an endometrial estrogen agonist. Raloxifene is approved for prevention and treatment of osteoporosis and prevention of breast cancer. The selective ER modulators bazedoxifene paired with conjugated estrogens relieves vasomotor symptoms and prevents bone loss with neutral effects on breast and amenorrhea similar to placebo. Ospemifene is approved to treat dyspareunia. Lasofoxifene is in development for resistant ER positive breast cancer. Estetrol (E4), synthesized by human fetal liver, has dual weak-estrogenic/antiestrogenic features, now approved as a contraceptive.

Selective estrogen receptor modulators and bone health

Selective estrogen receptor modulators (SERMs) are synthetic molecules that bind to the estrogen receptor and can have agonistic activity in some tissues while being estrogen antagonistic in others. While not all SERMs are clinically available in all parts of the world, this article will review preclinical and clinical effects of various SERMs on bone. These include tamoxifen, used as adjuvant therapy in breast cancer patients as well as for breast cancer prevention; raloxifene, approved for osteoporosis prevention and treatment as well as breast cancer prevention; bazedoxifene, approved for prevention of osteoporosis and also in combination with conjugated equine estrogen for treatment of vasomotor symptoms and prevention of bone loss in postmenopausal patients; and ospemifene, approved for treatment of dyspareunia due to vulvovaginal atrophy/genitourinary syndrome of menopause. Thus, these SERMs are a diverse group of estrogen agonist/antagonists that seem to have class effects in the bone and breast, although the amount of clinical trial data is quite variable. However, there does not seem to be the same unidirectional class activity in tissues like the uterus or vagina. Health-care providers should be cognizant of all available information in helping patients make the best possible shared decision-making choices.

Effects of Raloxifene Combined with Low-dose Conjugated Estrogen on the Endometrium in Menopausal Women at High Risk for Breast Cancer

OBJECTIVES

To compare the effects of low-dose conjugated estrogen (CE), raloxifene, and the combination thereof on the endometrium of postmenopausal women.

METHODS

Postmenopausal women between 45 and 60 years of age, with Gail score≥1.67 and no endometrial disorders, were randomly assigned to receive low-dose CE (0.3 mg), raloxifene (60 mg), or combined therapy for 1 year. Transvaginal ultrasound was performed at baseline and every 3 months; the Kupperman Index was assessed at baseline and every 6 months. Endometrial biopsies were performed if endometrial thickness (ET) was ≥5 mm or if vaginal bleeding occurred. The primary outcome was the occurrence of ET≥5 mm over the one-year period.

RESULTS

Seventy-three women were randomly assigned and analyzed on an intent-to-treat basis. Eight, three, and four women in the CE, raloxifene, and combination groups, respectively, exhibited ET≥5 mm. No genital bleeding was reported in the combination group. Endometrial biopsy revealed atrophy or polyps in all groups, with one patient in the CE group exhibiting a proliferative endometrium without atypia. At 6 months, there was a progressive increase in mean ET in the CE group, but not in the other two groups, with statistically significant differences at 6, 9, and 12 months. Mean scores for vasomotor symptoms and Kupperman Index favored the CE and combination groups over raloxifene.

CONCLUSION

Combined raloxifene and low-dose CE decreased the severity of menopausal symptoms to a similar extent as CE alone and had similar effects as raloxifene alone on the endometrium.

Design, synthesis, and biological evaluation of new raloxifene analogues of improved antagonist activity and endometrial safety

Raloxifene agonism of estrogen receptor (ER) in post-menopausal endometrium is not negligible. Based on a rational drug design workflow, we synthesized 14 analogues of raloxifene bearing a polar group in the aromatic ring of the basic side chain (BSC) and/or changes in the bulkiness of the BSC amino group. Analogues with a polar BSC aromatic ring and amino group substituents of increasing volume displayed increasing ER antagonism in Ishikawa cells. Analogues with cyclohexylaminoethoxy (13a) or adamantylaminoethoxy BSC (13b) lacking a polar aromatic ring displayed high ER-binding affinity and ER antagonism in Ishikawa cells higher than raloxifene and similar to fulvestrant (ICI182,780). The endometrial surface epithelium of immature female CD1 mice injected with 13b was comparable to that of vehicle-treated mice, while that of mice treated with estradiol, raloxifene or 13b in combination with estradiol was hyperplastic. These findings indicate that raloxifene analogues with a bulky BSC amino group could provide for higher endometrial safety treatment of the menopausal syndrome.

Beyond estrogen: advances in tissue selective estrogen complexes and selective estrogen receptor modulators

Selective estrogen receptor modulators (SERMs) are synthetic non-steroidal agents which have variable estrogen agonist and antagonist activities in different target tissues. Tamoxifen is an anti-estrogen in the breast used for treatment and prevention of breast cancer, with estrogen agonist activity in the uterus. Raloxifene prevents and treats osteoporosis and prevents breast cancer, and can be safely combined with vaginal but not systemic estrogen. The tissue selective estrogen complex combines conjugated equine estrogens (CEE) with the SERM bazedoxifene (BZA). The five Selective Estrogen Menopause and Response to Therapy studies, with up to 2 years of data, demonstrated that CEE/BZA 0.45 mg/BZA 20 mg improved vasomotor symptoms and vulvovaginal atrophy, prevented bone loss, and was neutral on breast tenderness, breast density, with breast cancer incidence similar to placebo. Protection against estrogen-induced endometrial hyperplasia and cancer was found, with similar amenorrhea rates to placebo. Ospemifene is approved to treat dyspareunia, with potential benefits on bone and the breast, while lasofoxifene is being developed to treat resistant estrogen receptor-positive breast cancer in women. Estetrol is an estrogen synthesized exclusively during pregnancy by the human fetal liver and initially considered a weak estrogen, but it appears to have dual weak estrogenic/anti-estrogenic features.

Variation in menopausal vasomotor symptoms outcomes in clinical trials: a systematic review

BACKGROUND

There is substantial variation in how menopausal vasomotor symptoms are reported and measured among intervention studies. This has prevented meaningful comparisons between treatments and limited data synthesis.

OBJECTIVES

To review systematically the outcome reporting and measures used to assess menopausal vasomotor symptoms from randomised controlled trials of treatments.

SEARCH STRATEGY

We searched MEDLINE, Embase, and Cochrane Central Register of Controlled Trials from inception to May 2018.

SELECTION CRITERIA

Randomised controlled trials with a primary outcome of menopausal vasomotor symptoms in women and a sample size of at least 20 women per study arm.

DATA COLLECTION AND ANALYSIS

Data about study characteristics, primary vasomotor-related outcomes and methods of measuring them.

MAIN RESULTS

The search identified 5591 studies, 214 of which were included. Forty-nine different primary reported outcomes were identified for vasomotor symptoms and 16 different tools had been used to measure these outcomes. The most commonly reported outcomes were frequency (97/214), severity (116/214), and intensity (28/114) of vasomotor symptoms or a composite of these outcomes (68/214). There was little consistency in how the frequency and severity/intensity of vasomotor symptoms were defined.

CONCLUSIONS

There is substantial variation in how menopausal vasomotor symptoms have been reported and measured in treatment trials. Future studies should include standardised outcome measures which reflect the priorities of patients, clinicians, and researchers. This is most effectively achieved through the development of a Core Outcome Set. This systematic review is the first step towards development of a Core Outcome Set for menopausal vasomotor symptoms.

TWEETABLE SUMMARY

Menopausal hot flushes and night sweats have been reported in 49 different ways in clinical research. A core outcome set is urgently required.

Tissue selective estrogen complex (TSEC): a review

Objective:

This review describes historical development of selective estrogen receptor modulators (SERMs) and their combination with estrogens, termed a tissue selective estrogen complex (TSEC), and considers the potential for future TSEC development.

Methods:

This narrative review is based on literature identified on PubMed and the TSEC research and development experience of the authors.

Results:

SERMs have estrogenic and antiestrogenic effects in various tissues; however, no single agent has achieved an optimal balance of agonist and antagonist effects for the treatment of menopausal symptoms. Clinically, a number of SERMs protect against osteoporosis and breast cancer but can exacerbate vasomotor symptoms. Estrogens alleviate menopausal hot flushes and genitourinary symptoms as well as reduce bone loss, but the addition of a progestogen to menopausal hormone therapy to protect against endometrial cancer increases vaginal bleeding risk, breast tenderness, and potentially breast cancer. The search for an effective menopausal therapy with better tolerability led to the investigation of TSECs. Clinical development of a TSEC consisting of conjugated estrogens/bazedoxifene increased understanding of the importance of a careful consideration of the combination's components and their respective doses to balance safety and efficacy. Bazedoxifene is an estrogen receptor agonist in bone but an antagonist/degrader in the endometrium, which has contributed to its success as a TSEC component. Other oral TSEC combinations studied thus far have not demonstrated similar endometrial safety.

Conclusions:

Choice of SERM, selection of doses, and clinical trial data evaluating safety and efficacy are key to ensuring safety and adequate therapeutic effect of TSECs for addressing menopausal symptoms.

Initial investigation into the optimal dose ratio of conjugated estrogens and bazedoxifene: a double-blind, randomized, placebo-controlled phase 2 dose-finding study

OBJECTIVE

The aim of the study was to explore dose-related endometrial effects of conjugated estrogens/bazedoxifene (CE/BZA).

METHODS

In this randomized, double-blind, phase 2 study, 408 nonhysterectomized, symptomatic (with hot flushes [HFs]) postmenopausal women received ≥1 dose of CE 0.3 or 0.625 mg alone or with BZA 5, 10, or 20 mg/d; placebo; BZA 5 mg/d alone; or CE 0.625 mg with medroxyprogesterone acetate 2.5 mg/d for 84 days. The primary outcome was endometrial thickness on transvaginal ultrasound. HF frequency and severity based on diaries were key secondary outcomes.

RESULTS

CE 0.625 mg alone increased endometrial thickness compared with placebo (mean 5.5 vs 2.95 mm, P < 0.001); BZA countered this in a dose-related manner such that average thickness with the addition of BZA 5, 10, and 20 mg was 5.99, 4.33, and 3.54 mm, respectively. On average, endometrium was significantly less thick with CE 0.625 mg/BZA 20 mg than CE 0.625 mg (P < 0.001) and CE 0.3 mg/BZA 20 mg versus CE 0.3 mg (2.94 vs 3.92 mm, P < 0.05); endometrial thickness was similar to placebo with CE 0.625 mg/BZA 20 mg. Lower BZA doses failed to reduce endometrial thickness relative to the same dose of CE alone. Regimens containing CE 0.625 mg reduced HF frequency and severity versus placebo; CE 0.3 mg with BZA 10 or 20 mg was ineffective.

CONCLUSIONS

BZA ≥20 mg is needed to counter endometrial growth resulting from treatment with CE 0.3 or 0.625 mg. CE 0.3 mg inadequately controls HFs if given with BZA 20 mg.

Effects of bazedoxifene/conjugated estrogens on reproductive endocrinology and reproductive tract ultrasonographic appearance in premenopausal women: a preliminary study

Bazedoxifene (BZA) paired with conjugated estrogens (CE) is the first tissue selective estrogen receptor complex (TSEC) approved by the United States Food and Drug Administration for the treatment of menopausal symptoms. Clinical trials in menopausal women and in premenopausal murine models of endometriosis have demonstrated safety and efficacy, however, the impact of BZA/CE on premenopausal women is not known. Here we report a case series study in premenopausal women assessing effects of BZA/CE on reproductive hormones, and uterine/ovarian ultrasonographic appearance. After one monitoring cycle, five subjects underwent daily administration of BZA/CE (20 mg/0.45 mg) for 12 weeks, and were followed for 4 weeks after treatment. Uterine/ovarian morphology was assessed with ultrasound, and endocrinologic function with ovulation prediction kits and serum assessment of reproductive hormones throughout the menstrual cycle. All subjects demonstrated an LH surge on the medication; interestingly there was a significant decrease in luteinizing hormone level during treatment compared to posttreatment values. BZA/CE was well-tolerated in premenopausal women and did not induce clinically relevant reproductive hormone changes, endometrial alterations, or abnormal ovarian folliculogenesis.

Tissue-selective Estrogen Complex for Menopausal Hormone Therapy

The first approved tissue-selective estrogen complex is a pairing of conjugated estrogen combined with the selective estrogen-receptor modulator, bazedoxifene. Advantages include relief of menopausal symptoms without the increased chance of bleeding or breast tenderness unlike with traditional estrogen-progestin therapy, which is associated with both bleeding and breast tenderness. Tissue-selective estrogen complex effects on relief of vasomotor symptoms, prevention of bone loss, improvement in vaginal symptoms, lack of significant cardiovascular effects beyond the expected 2-fold increase in venous thrombosis, neutral effect on breast, and protective effects on the endometrium are discussed.

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.

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.

Bazedoxifene and Conjugated Equine Estrogen: A Combination Product for the Management of Vasomotor Symptoms and Osteoporosis Prevention Associated with Menopause

Bazedoxifene (BZA), a third-generation selective estrogen receptor modulator (SERM), has been combined with conjugated equine estrogen (CE) to create a tissue selective estrogen complex (TSEC) for the management of vasomotor symptoms (VMS) and the prevention of osteoporosis (OP) associated with menopause. Both of these outcomes of menopause contribute to significant negative effects on quality of life and increases in utilization of health care resources and dollars. Current treatment modalities for VMS and OP include estrogen therapy that requires the use of progestin in women who have a uterus to reduce the risk of endometrial hyperplasia and resultant cancer. However, progestin use results in nuisance bleeding as well as a further increased risk of breast cancer when combined with estrogen. And while SERMs can be used to prevent OP, their use alone has been shown to increase hot flashes. The combination of BZA and CE does not require progestin treatment with CE as the BZA component acts as an antagonist on endometrial tissue. The U.S. Food and Drug Administration approval of BZA/CE in 2013 was based on a series of five phase 3 studies known as the Selective estrogens, Menopause And Response to Therapy (SMART) trials. These trials, in their entirety, evaluated the impact of BZA/CE on VMS frequency and severity, bone mineral density, bone turnover markers, vaginal symptoms, lipid profiles, sleep, quality of life, breast density, and endometrial safety. The approved dose of BZA/CE is 20 mg BZA and 0.45 mg CE. Although this TSEC manages VMS while opposing breast and endometrial proliferation, preventing bone resorption, and improving lipid profiles, long-term experience with BZA/CE is currently lacking.

Patient considerations in the management of menopausal symptoms: role of conjugated estrogens with bazedoxifene

Menopausal symptoms (eg, hot flushes and vaginal symptoms) are common, often bothersome, and can adversely impact women's sexual functioning, relationships, and quality of life. Estrogen-progestin therapy was previously considered the standard care for hormone therapy (HT) for managing these symptoms in nonhysterectomized women, but has a number of safety and tolerability concerns (eg, breast cancer, stroke, pulmonary embolism, breast pain/tenderness, and vaginal bleeding) and its use has declined dramatically in the past decade since the release of the Women's Health Initiative trial results. Conjugated estrogens paired with bazedoxifene (CE/BZA) represent a newer progestin-free alternative to traditional HT for nonhysterectomized women. CE/BZA has demonstrated efficacy in reducing the frequency and severity of vasomotor symptoms and preventing loss of bone mineral density in postmenopausal women. CE/BZA provides an acceptable level of protection against endometrial hyperplasia and does not increase mammographic breast density. Compared with traditional estrogen-progestin therapy, it is associated with lower rates of breast pain/tenderness and vaginal bleeding. Patient-reported outcomes indicate that CE/BZA improves menopause-specific quality of life, sleep, some measures of sexual function (especially ease of lubrication), and treatment satisfaction. This review looks at the rationale for selection and combination of CE with BZA at the dose ratio in the approved product and provides a detailed look at the efficacy, safety, tolerability, and patient-reported outcomes from the five Phase III trials. Patient considerations in the choice between CE/BZA and traditional HT (eg, tolerability, individual symptoms, and preferences for route of administration) are also considered.

The Effect of Menopausal Hormone Therapies on Breast Cancer: Avoiding the Risk

Estrogen and P treatment results in greater risk of breast cancer than placebo. Treatment with estrogen alone does not increase the risk of breast cancer, may be used by women who have had a hysterectomy, and may even result in a decreased risk of breast cancer. Continued research seeks to improve the understanding of the interplay between estrogen and progestogens that predispose to adverse effects on breast tissue. Caution over this hypothesized benefit is warranted until it is substantiated by data on the incidence of breast cancer in tissue selective estrogen complex users.

Clinical effects of selective estrogen receptor modulators on vulvar and vaginal atrophy

OBJECTIVE

Vaginal estrogen therapy at the lowest effective dose is generally recommended for the treatment of vulvar and vaginal atrophy (VVA), but not all women are candidates. Selective estrogen receptor modulators (SERMs) aim to elicit specific positive effects on targeted tissues with neutral or minimal negative effects on other tissues. This review compares the vaginal effects of currently available and investigational SERMs.

METHODS

Relevant English-language articles published between 1980 and 2012 were identified through the PubMed database (search string "[Selective Estrogen Receptor Modulator OR SERM] AND [Vulvar OR Vaginal] AND Atrophy"), article reference lists, and EMBASE searches for individual SERMs. Both authors reviewed all articles, which formed the basis of this narrative literature review.

RESULTS

Activity profiles of SERMs in various tissues are distinct. Tamoxifen and arzoxifene have no specific positive vaginal effects but have reported variable or adverse gynecologic effects. Raloxifene does not improve VVA but can be used safely in combination with vaginal estrogen. Bazedoxifene has no demonstrated efficacy for VVA but, in combination with oral conjugated equine estrogens, improves the signs and symptoms of VVA. SERMs with positive vaginal effects (such as improvement in the vaginal maturation index, reduced vaginal pH, and improvement in the signs and symptoms of VVA) on postmenopausal symptomatic women include lasofoxifene (clinical development on hold) and ospemifene, which was recently approved for the treatment of VVA-related dyspareunia, with a class effect warning of potential venous thrombosis risk.

CONCLUSIONS

SERMs that specifically target the pathophysiology underlying VVA may provide an alternative to vaginal or systemic estrogen therapy.

From empirical to mechanism-based discovery of clinically useful Selective Estrogen Receptor Modulators (SERMs)

Our understanding of the molecular mechanisms underlying the pharmacological actions of estrogen receptor (ER) ligands has evolved considerably in recent years. Much of this knowledge has come from a detailed dissection of the mechanism(s) of action of the Selective Estrogen Receptor Modulators (SERMs) tamoxifen and raloxifene, drugs whose estrogen receptor (ER) agonist/antagonist properties are influenced by the cell context in which they operate. These studies have revealed that notwithstanding differences in drug pharmacokinetics, the activity of an ER ligand is determined primarily by (a) the impact that a given ligand has on the receptor conformation and (b) the ability of structurally distinct ER-ligand complexes to interact with functionally distinct coregulators. Exploitation of the established relationships between ER structure and activity has led to the development of improved SERMs with more favorable therapeutic properties and of tissue-selective estrogen complexes, drugs in which a SERM and an ER agonist are combined to yield a blended activity that results in distinct clinical profiles. Remarkably, endogenous ligands that exhibit SERM activity have also been identified. One of these ligands, 27-hydroxycholesterol (27HC), has been shown to manifest ER-dependent pathological activities in the cardiovascular system, bone and mammary gland. Whereas the physiological activity of 27HC remains to be determined, its discovery highlights how cells have adopted mechanisms to allow the same receptor ligand complex to manifest different activities in different cells, and also how these processes can be exploited for new drug development.

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.

Use of SERMs for treatment in postmenopausal women

Selective estrogen receptor modulators (SERMs) are synthetic non-steroidal agents which have varying estrogen agonist and antagonist activities in different tissues, most likely due to the receptor conformation changes associated with that SERM's binding and the subsequent effect on transcription. Clinical trials aim to differentiate amongst SERMs on selected target tissues for use in postmenopausal women including effects on breast, bone, cardiovascular venous thrombosis risk, endometrium, vagina, vasomotor symptoms, and brain. This paper describes differences in clinical effects on selected target tissues of SERMs that are approved, discontinued or in development. FDA approved SERMs include tamoxifen and toremifene used for prevention and treatment of breast cancer, raloxifene approved for prevention and treatment of osteoporosis and prevention of invasive breast cancer, and ospemifene approved for treatment of dyspareunia from menopausal vaginal atrophy. The FDA approved first tissue selective estrogen complex (TSEC) a pairing of conjugated equine estrogens with the SERM, bazedoxifene. This pairing reduces the risk of endometrial hyperplasia that can occur with the estrogenic component of the TSEC without the need for a progestogen in women with a uterus. It also allows for the estrogenic benefits on relief of hot flashes and prevention of bone loss without stimulating the breast or the endometrium. In clinical practice, the tissue-selective actions of SERMs, alone or paired with estrogens, allow for individualization in meeting the treatment needs of postmenopausal women by providing targeted tissue effects. This article is part of a Special Issue entitled 'Menopause'.

Treatment with bazedoxifene and conjugated estrogens results in regression of endometriosis in a murine model

Bazedoxifene (BZA), a selective estrogen receptor modulator (SERM), inhibits the action of estrogens on endometrial proliferation. Here, we evaluate the effect of a tissue-selective estrogen complex (TSEC) containing BZA and conjugated estrogens (CE) on ectopic endometrial lesions in a mouse model of endometriosis. Experimental endometriosis was created in 60 female CD-1 mice. The mice were randomly divided into 10 groups that received varying doses of either BZA (1, 2, 3, or 5 mg/kg/day), BZA (1, 2, 3, or 5 mg/kg/day) in combination with CE (3 mg/kg/day), CE treatment alone (3 mg/kg/day), or vehicle control for 8 wk. Treatment with BZA alone or the TSEC containing BZA/CE led to a decrease in endometriotic lesion size compared to controls. The mean surface area of the untreated lesions was 19.6 mm(2). Treatment with BZA or BZA/CE resulted in reduced lesion size (to 8.8 and 7.8 mm(2), respectively). No significant difference was found in lesion size between the BZA and BZA/CE treatment groups or between different doses of either treatment. Ovarian cyst formation was not evident in the treated groups. Treatment with the TSEC containing higher BZA dosages (3 and 5 mg/kg/day) led to significantly lower levels of estrogen receptor (Esr1) mRNA expression compared to the control treatment. No differences were observed in expression of progesterone receptor (Pgr). Immunohistochemical analysis also demonstrated a decrease in ESR protein. The combination of CE and BZA may prove to be a novel treatment option for endometriosis.

Conjugated estrogens combined with bazedoxifene: the first approved tissue selective estrogen complex therapy

Menopausal therapy with a tissue selective estrogen complex combines estrogens with a selective estrogen receptor modulator, with the goal of blending the desirable effects of estrogens on menopausal symptoms and bone with the tissue selective properties of a selective estrogen receptor modulator. The first tissue selective estrogen complex to receive regulatory approval is a combination of conjugated estrogens (CE) with bazedoxifene (BZA). Clinical trials with CE/BZA in postmenopausal women have shown improvement in vasomotor symptoms, vulvo-vaginal atrophy, and bone mineral density, without stimulation of the endometrium or breast tissue, with a generally favorable safety and tolerability profile. CE/BZA represents a new approach to the management of menopausal symptoms in women with a uterus.

Current and evolving approaches to individualizing estrogen receptor-based therapy for menopausal women

CONTEXT

Adding progestogens to estrogens changes the risk profile of hormonal therapy for menopausal women, and recent data support the need for progestogen-free options. Several current and evolving approaches to managing estrogen deficiency allow for progestogen omission. We review the mechanisms of estrogen activity and provide an overview of emerging and available estrogen receptor (ER)-based therapies.

EVIDENCE ACQUISITION

PubMed was searched for relevant English-language articles using keywords pertaining to estrogen deficiency, menopause, hormone therapy, and estrogen-only therapy. Pivotal or recent randomized controlled trials, large observational studies, comprehensive meta-analyses, and established therapeutic guidelines were compiled.

EVIDENCE SYNTHESIS

Advances in our understanding of ER pharmacology have led to therapies designed to optimize ER activity, including selective ER modulators (SERMs) and tissue-selective estrogen complexes (TSECs). Each estrogen, SERM, and TSEC exhibits a unique profile of tissue-specific activity, spanning the spectrum from ER agonism to antagonism. Systemic estrogens unopposed by progestogens effectively manage menopausal symptoms in hysterectomized postmenopausal women but require progestogen use in postmenopausal women with a uterus. SERMs are effective for managing certain aspects of estrogen deficiency in postmenopausal women, but data suggest that pairing a SERM with estrogens to form a TSEC provides a more optimal therapeutic profile for women with a uterus.

CONCLUSIONS

Treating signs and symptoms of estrogen deficiency requires an individualized approach based on a woman's goals and the purported risks of different therapies. New and emerging agents have demonstrated efficacy in postmenopausal women with a uterus, while allowing these women to avoid progestogens and their possible adverse effects.

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.

Animal models for the effective development of atrophic vaginitis therapies: possibilities and limitations

INTRODUCTION

Vaginal atrophy (VA) is an inflammation of the vagina that develops when there is a significant decrease in levels of the estrogen. Prolonged periods of hypoestrogenism may induce severe VA and treatment is essential. This is a significant problem which requires more focused attention for the development of existing and future therapies.

AREAS COVERED

This review evaluates the suitable animal models of VA, including: mice, rodents and non-human primates. It focuses particularly on the possibilities and limitations of these in vivo models for the effective development of VA therapies.

EXPERT OPINION

Hormone replacement therapy (HRT) has been prescribed and successfully used for VA. However, some studies have shown that HRT may be linked to an increased risk of breast cancer, coronary heart diseases and others risks. Thus, there is a growing interest in effective and safe alternatives to VA symptoms. There are, however, a number of things that must be considered for future drug discovery efforts. One major consideration is what animal model should be used and whether the model is appropriate for the study aim. Similarly, research studies must also consider the influencing factors on these animal models, so that these models can effectively mimic the actual disease. The authors also highlight the need to standardize research parameters to produce more reliable and reproducible data.

Effects of bazedoxifene/conjugated estrogens on endometrial safety and bone in postmenopausal women

OBJECTIVES

Bazedoxifene/conjugated estrogens (BZA/CE) has demonstrated efficacy in improving vasomotor and vulvar/vaginal atrophy symptoms in postmenopausal women. This study evaluated the endometrial safety of BZA/CE and effects on bone mineral density (BMD) compared with CE/medroxyprogesterone acetate (MPA) and placebo.

METHODS

The Selective estrogens, Menopause, And Response to Therapy (SMART)-4 trial was a 1-year, multicenter, double-blind, randomized, placebo- and active-controlled, phase-3 study in non-hysterectomized, postmenopausal women (n = 1061; aged 40 -< 65 years). Subjects received BZA 20 mg/CE 0.45 or 0.625 mg, CE 0.45 mg/MPA 1.5 mg, or placebo daily. Primary endpoints were the incidence of endometrial hyperplasia and the change in lumbar spine BMD at 1 year. Secondary endpoints included the change in total hip BMD and rates of amenorrhea and breast pain.

RESULTS

At 1 year, no cases of endometrial hyperplasia were identified in the BZA 20-mg/CE 0.45-mg group, while three cases (1.1%) were confirmed for the BZA 20-mg/CE 0.625-mg group (95% one-sided confidence interval upper limit < 4%). Both BZA/CE doses significantly increased lumbar spine and total hip BMD versus placebo (p ≤ 0.001) and showed low incidences of bleeding and breast tenderness, similar to placebo and significantly lower than for CE 0.45 mg/MPA 1.5 mg (p < 0.05). BZA/CE treatment was generally safe and well tolerated.

CONCLUSIONS

BZA 20 mg/CE 0.45 and 0.625 mg significantly improved BMD while maintaining endometrial safety and showed a favorable safety/tolerability profile over 1 year. BZA/CE may be a promising therapy for treating menopausal symptoms and preventing osteoporosis in non-hysterectomized, postmenopausal 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.

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.

Selective oestrogen receptor modulators decrease the inflammatory response of glial cells

Neuroinflammation comprises a feature of many neurological disorders that is accompanied by the activation of glial cells and the release of pro-inflammatory cytokines and chemokines. Such activation is a normal response oriented to protect neural tissue and it is mainly regulated by microglia and astroglia. However, excessive and chronic activation of glia may lead to neurotoxicity and may be harmful for neural tissue. The ovarian hormone oestradiol exerts protective actions in the central nervous system that, at least in part, are mediated by a reduction of reactive gliosis. Several selective oestrogen receptor modulators may also exert neuroprotective effects by controlling glial inflammatory responses. Thus, tamoxifen and raloxifene decrease the inflammatory response caused by lipopolysaccharide, a bacterial endotoxin, in mouse and rat microglia cells in vitro. Tamoxifen and raloxifene are also able to reduce microglia activation in the brain of male and female rats in vivo after the peripheral administration of lipopolysaccharide. In addition, tamoxifen decreases the microglia inflammatory response induced by irradiation. Furthermore, treatment with tamoxifen and raloxifene resulted in a significant reduction of the number of reactive astrocytes in the hippocampus of young, middle-aged and older female rats after a stab wound injury. Tamoxifen, raloxifene and the new selective oestrogen receptor modulators ospemifene and bazedoxifene decrease the expression and release of interleukine-6 and interferon-γ inducible protein-10 in cultured astrocytes exposed to lipopolysaccharide. Ospemifene and bazedoxifene exert anti-inflammatory effects in astrocytes by a mechanism involving classical oestrogen receptors and the inhibition of nuclear factor-kappa B p65 transactivation. These data suggest that oestrogenic compounds are candidates to counteract brain inflammation under neurodegenerative conditions by targeting the production and release of pro-inflammatory molecules by glial cells.

Skeletal effects of bazedoxifene paired with conjugated estrogens in ovariectomized rats

A novel approach to menopausal therapy is the tissue selective estrogen complex (TSEC) that partners bazedoxifene (BZA) with conjugated estrogens (CE). We examined the effects of daily treatment with BZA 0.3mg/kg, CE 2.5mg/kg, or combined BZA/CE (BZA 0.1, 0.3, or 1.0mg/kg with CE 2.5mg/kg) over 12months on bone mass, bone architecture and strength, and biochemical markers of bone turnover in ovariectomized (OVX) female Sprague-Dawley rats vs OVX control rats. Total cholesterol and uterine weights were also evaluated. All BZA/CE dose combinations prevented ovariectomy-induced increases in bone turnover and significantly increased bone mineral density (BMD) at the lumbar spine, proximal femur, and tibia compared with OVX controls. All BZA/CE doses evaluated also prevented many of the ovariectomy-induced changes of the static and dynamic parameters of the cortical compartment of the tibia and the cancellous compartment of the L1 and L2 vertebrae. All BZA/CE doses increased biomechanical strength at the lumbar spine (L4) compared with OVX animals. The co-administration of BZA 0.3 and 1.0mg/kg/day with CE 2.5mg/kg/day showed a dose-dependent reduction in uterine wet weight compared with administration of CE alone. All BZA/CE doses significantly lowered total cholesterol levels compared with OVX controls. In conclusion, 12months of treatment with BZA/CE in OVX rats effectively maintained BMD, bone microstructure, and bone quality; and the pairing of BZA with CE prevented CE-induced uterine stimulation.

Combination of raloxifene, aspirin and estrogen as novel paradigm of hormone replacement therapy in rabbit model of menopause

AIM

To assess a novel hormone replacement therapy (HRT) paradigm using raloxifene, aspirin combined with estrogen in rabbit model of menopause.

METHODS

Female New Zealand white rabbits were ovariectomized or sham-operated. The ovariectomized rabbits were divided into 7 groups: estradiol valerate (E(2)), raloxifene, aspirin, E(2) /raloxifene, E(2)/aspirin, E(2) /raloxifene/aspirin and vehicle. Two weeks after the operation, the rabbits were administered the above drugs for 12 weeks. Then, the mammary glands were examined histologically, uterus was weighted, and blood sample was collected for analyzing the levels of estrogen, serum lipids and monocyte chemoattractant protein (MCP)-1, and platelet aggregation. The aortic tissue was examined morphometrically.

RESULTS

Compared with E(2) 0.1 mg·kg(-1)·d(-1) treatment alone, the pairing of raloxifene 10 mg·kg(-1)·d(-1) with E(2) significantly decreased the extent of mammary gland branches and ducts (5.53%±1.23% vs 15.4%±2.17%, P<0.01), as well as the uterine weight (2.16±0.35 g vs 4.91±0.75 g, P<0.01). However, E(2)/raloxifene or E(2) alone treatment significantly stimulated platelet aggregation relative to vehicle group. Addition of aspirin 5 mg·kg(-1)·d(-1) reduced platelet aggregation to almost the same level as the vehicle group. E(2) treatment exerted a positive effect on serum lipids and MCP-1, and a regression in aortic intimal plaque size compared to the vehicle. Raloxifene reinforced the positive effects of E(2).

CONCLUSION

The combination of raloxifene, aspirin and E(2) exhibits positive lipid, MCP-1 and atherosclerotic responses with minimal stimulation of breast and uterine tissues as well as platelet aggregation in a rabbit model of the menopause.

Estrogen receptor ligands counteract cognitive deficits caused by androgen deprivation in male rats

Androgen deprivation causes impairment of cognitive tasks in rodents and humans, and this deficit can be reverted by androgen replacement therapy. Part of the effects of androgens in the male may be mediated by their local metabolism to estradiol or 3-alpha androstanediol within the brain and the consequent activation of estrogen receptors. In this study we have assessed whether the administration of estradiol benzoate, the estrogen receptor β selective agonist diarylpropionitrile or the estrogen receptor α selective agonist propyl pyrazole triol affect performance of androgen-deprived male Wistar rats in the cross-maze test. In addition, we tested the effect of raloxifene and tamoxifen, two selective estrogen receptor modulators used in clinical practice. The behavior of the rats was assessed 2 weeks after orchidectomy or sham surgery. Orchidectomy impaired acquisition in the cross-maze test. Estradiol benzoate and the selective estrogen receptor β agonist significantly improved acquisition in the cross-maze test compared to orchidectomized animals injected with vehicle. Raloxifene and tamoxifen at a dose of 1mg/kg, but not at doses of 0.5 or 2mg/kg, also improved acquisition of orchidectomized animals. Our findings suggest that estrogenic compounds with affinity for estrogen receptor β and selective estrogen receptor modulators, such as raloxifene and tamoxifen, may represent good candidates to promote cognitive performance in androgen-deprived males.