Effects of ospemifene and raloxifene on hormonal status, lipids, genital tract, and tolerability in postmenopausal women

Serendipity in the search for "morning-after pills" led to clomiphene for the induction of ovulation

The approval of the oral contraceptive on June 23, 1960, by the United States Food and Drug Administration (FDA), changed society forever. For the first time, a pill designed and tested by men, supported by influential women, allowed women to control their fertility. For the first time, the FDA approved a medicine to be taken by humans without a disease. The chance discovery of a new group of medicines called nonsteroidal antiestrogens, created an opportunity for the pharmaceutical industry. These compounds were shown to be postcoital antifertility agents in rats and mice. In the 1960s, the development of a "morning-after pill" would have had an enormous market. Numerous companies focused discovery efforts to evaluate the development of their patented nonsteroidal antiestrogens: Merrell (clomiphene), Upjohn (U-11,100A), and ICI Pharmaceutical Division (ICI46,474). However, the antifertility effects of antiestrogens in rats and mice does not mean that the new medicine would be an antifertility agent in women. In this case, clomiphene did exactly the opposite of what it was predicted to prevent. Clomiphene became the first medicine to induce ovulation in subfertile women. This article describes the twists and turns of drug discovery and development over the past half century. The conclusion emphasizes the evolution of drug development over decades, based on fashions in medical research and discoveries in clinical pharmacology. As a result, new uses for old molecules, that started life as "nonsteroidal antiestrogens," have revolutionized women's health as members of the new group of medicines called selective estrogen receptor modulators.

Managing Genitourinary Syndrome of Menopause in Breast Cancer Survivors Receiving Endocrine Therapy

Patients with breast cancer receiving antiestrogen therapy, specifically aromatase inhibitors, often suffer from vaginal dryness, itching, irritation, dyspareunia, and dysuria, collectively known as genitourinary syndrome of menopause (GSM). GSM can decrease quality of life and is undertreated by oncologists because of fear of cancer recurrence, specifically when considering treatment with vaginal estrogen therapy because of unknown levels of systemic absorption of estradiol. In this article, we review the available literature for treatment of GSM in patients with breast cancer and survivors, including nonhormonal, vaginal hormonal, and systemic hormonal therapy options. First-line treatment includes nonhormonal therapy with vaginal moisturizers, lubricants, and gels. Although initial studies showed significant improvement in symptoms, the US Food and Drug Administration recently issued a warning against CO2 laser therapy for treatment of GSM until additional studies are conducted. In severe or refractory GSM, after discussing risks and benefits of vaginal hormonal therapy, the low-dose 10-μg estradiol-releasing intravaginal tablet or lower-dose 4 μg estrogen vaginal insert and intravaginal dehydroepiandrosterone (prasterone) are options for treatment, because studies show minimal elevation in serum estradiol levels and significant improvement in symptoms. The decision to offer vaginal estrogen therapy must be individualized and made jointly with the patient and her oncologist.

Ospemifene's effects on lipids and coagulation factors: a post hoc analysis of phase 2 and 3 clinical trial data

Objective:

To evaluate the effect of ospemifene 60 mg on the lipid and coagulation parameters of postmenopausal women using data from five phase 2 and 3 clinical trials.

Methods:

Data for lipids and coagulation factors for 2,166 postmenopausal women were pooled from five randomized, placebo-controlled studies. Lipid and coagulation parameters included in this analysis were total cholesterol, high-density lipoproteins (HDL), low-density lipoproteins (LDL), triglycerides, activated partial thromboplastin time (aPTT), fibrinogen, antithrombin antigen, protein C Ag, and protein S Ag free.

Results:

Mean percent changes in HDL and LDL were significantly greater with ospemifene versus placebo at month 3 (HDL: 4.4% vs 0.2%; LDL: −5.2% vs 2.4%), month 6 (HDL: 5.1% vs 1.5%; LDL: −6.7% vs 2.4%), and month 12 (HDL: 2.3% vs −1.9%; LDL: −7.0% vs −2.1%; P < 0.05, for all comparisons). Ospemifene significantly reduced total cholesterol at 6 months (−1.8% vs 1.6%; P = 0.0345 versus placebo), and changes in triglycerides with ospemifene were similar to placebo at all three time points. In subgroup analyses based on age, body mass index, and baseline triglyceride level, ospemifene increased HDL and decreased LDL, but had no significant effect on total cholesterol and triglycerides relative to placebo. Ospemifene significantly improved fibrinogen and protein C antigen levels relative to placebo at months 3 (−8.7% vs −0.8% and −2.7% vs 0.5%, respectively), 6 (−6.0% vs 6.7% and −3.6 vs 8.0%), and 12 (−8.7% vs 7.3% and −4.5% vs 6.6%; P < 0.01, for all). The levels of all coagulation factors remained within the normal range throughout the studies.

Conclusion:

Ospemifene 60 mg does not have a detrimental effect on lipid and coagulation parameters of postmenopausal women with up to 12 months of use.

Effects of vaginal conjugated equine estrogens and ospemifene on the rat vaginal wall and lower urinary tract

Although the positive effects of vaginal estrogens and the selective estrogen receptor modulator, ospemifene (OS), on the vaginal epithelium are well recognized, less is known regarding the effects of these therapies on the lower urinary tract or vaginal muscularis. Clinical evidence suggests that vaginally administered estrogen may improve overactive bladder-related symptoms. The objective of this study was to compare the effects of OS, vaginal conjugated equine estrogens (CEE), or both on the vaginal wall and lower urinary tract in a rat model of menopause. Contractile force of the bladder neck, dome, and external urethral sphincter at optimal field stimulation did not differ significantly among treatment groups. Pharmacologic responses to atropine, carbachol, and potassium chloride were similar among groups. Vaginal epithelial thickness and differentiation were differentially regulated by CEE or OS. Ospemifene altered epithelial differentiation pathways in vaginal epithelium in a unique way, and these effects were additive with local CEE. Unless contraindicated, the beneficial effects of vaginal CEE on the vaginal wall outweigh those of OS.

Ospemifene: A Novel Option for the Treatment of Vulvovaginal Atrophy

Ospemifene—a third-generation selective estrogen receptor modulator approved by the Food and Drug Administration in 2013—is an oral medication for the treatment of dyspareunia. In postmenopausal women with vulvovaginal atrophy, ospemifene significantly improves the structure and pH levels of the vagina, reducing dyspareunia. It is available as a 60-mg tablet; hence, women who may have had prior difficulty with vaginal administration or on-demand use of nonprescription lubricants and moisturizers would likely prefer this form of treatment. Preclinical studies demonstrated that ospemifene has an estrogen agonist action on the bone, reducing the cell proliferation of ductal carcinoma in an in situ model. Studies evaluating the safety of treatment for up to 52 weeks have shown that ospemifene is a safe medication with minimal impact on the endometrium. Further studies with larger number of subjects are necessary to better conclude its effects and long-term safety.

Not lost in translation: Emerging clinical importance of the G protein-coupled estrogen receptor GPER

It has been 20years that the G protein-coupled estrogen receptor (GPER) was cloned as the orphan receptor GPR30 from multiple cellular sources, including vascular endothelial cells. Here, I will provide an overview of estrogen biology and the historical background leading to the discovery of rapid vascular estrogen signaling. I will also review the recent advances in the understanding of the mechanisms underlying GPER function, its role in physiology and disease, some of the currently available GPER-targeting drugs approved for clinical use such as SERMs (selective estrogen receptor modulators) and SERDs (selective estrogen receptor downregulators). Many of currently used drugs such as tamoxifen, raloxifene, or faslodex™/fulvestrant were discovered targeting GPER many years after they had been introduced to the clinics for entirely different purposes. This has important implications for the clinical use of these drugs and their modes of action, which I have termed 'reverse translational medicine'. In addition, environmental pollutants known as 'endocrine disruptors' have been found to bind to GPER. This article also discusses recent evidence in these areas as well as opportunities in translational clinical medicine and GPER research, including medical genetics, personalized medicine, prevention, and its theranostic use.

Effects of ospemifene on the female reproductive and urinary tracts: translation from preclinical models into clinical evidence

Objective

Treatment of menopausal symptoms by compounds with tissue-selective estrogen agonist/antagonist effects, often called selective estrogen receptor modulators, has been researched as an alternative to the use of estrogen therapy. These structurally diverse molecules elicit tissue-dependent responses in hormone-responsive tissues and organs, exhibiting variations in estrogenic activity in preclinical models of postmenopausal reproductive tissues that may improve postmenopausal women’s health (eg, prevention and treatment of breast cancer, osteoporosis, and vulvar and vaginal atrophy).

Methods

This literature review investigates whether preclinical data predicted the clinical effects of ospemifene on female reproductive and urinary tract tissues and compares these findings with the specific vaginal effects of other estrogen receptor agonists/antagonists (tamoxifen, raloxifene, and bazedoxifene) in preclinical and clinical studies. Lasofoxifene, although not currently available, is included because of its unique effects on vaginal tissue.

Results

The response of endometrial and vaginal tissues to estrogen receptor agonists/antagonists can be differentiated using transvaginal ultrasound, endometrial histopathology, cytologic examination of vaginal smears, assessment of physical changes in the vagina, and relief of symptoms associated with vulvar and vaginal atrophy (such as dyspareunia).

Conclusions

Available evidence indicates that ospemifene has unique effects on tissue, leading to a favorable long-term profile for the relief of vulvar and vaginal atrophy compared with other estrogen receptor agonists/antagonists (eg, tamoxifen, raloxifene, and bazedoxifene) with no short-term concerns about endometrial safety (based on endometrial hyperplasia, carcinoma, endometrial spotting, and endometrial bleeding).

Atrophic vaginitis in breast cancer survivors: a difficult survivorship issue

Management of breast cancer includes systematic therapies including chemotherapy and endocrine therapy can lead to a variety of symptoms that can impair the quality of life of many breast cancer survivors. Atrophic vaginitis, caused by decreased levels of circulating estrogen to urinary and vaginal receptors, is commonly experienced by this group. Chemotherapy induced ovarian failure and endocrine therapies including aromatase inhibitors and selective estrogen receptor modulators can trigger the onset of atrophic vaginitis or exacerbate existing symptoms. Symptoms of atrophic vaginitis include vaginal dryness, dyspareunia, and irritation of genital skin, pruritus, burning, vaginal discharge, and soreness. The diagnosis of atrophic vaginitis is confirmed through patient-reported symptoms and gynecological examination of external structures, introitus, and vaginal mucosa. Lifestyle modifications can be helpful but are usually insufficient to significantly improve symptoms. Non-hormonal vaginal therapies may provide additional relief by increasing vaginal moisture and fluid. Systemic estrogen therapy is contraindicated in breast cancer survivors. Continued investigations of various treatments for atrophic vaginitis are necessary. Local estrogen-based therapies, DHEA, testosterone, and pH-balanced gels continue to be evaluated in ongoing studies. Definitive results are needed pertaining to the safety of topical estrogens in breast cancer survivors.

Safety and efficacy of ospemifene for the treatment of dyspareunia associated with vulvar and vaginal atrophy due to menopause

During the menopausal transition, women experience a number of symptoms due to declining estrogen levels, including vasomotor symptoms and vulvar and vaginal atrophy (VVA). Unlike vasomotor symptoms, vaginal dryness and dyspareunia, the main symptoms of VVA, typically worsen without treatment and can significantly impact the quality of life. Up to 60% of postmenopausal women may be affected by VVA, but many women unfortunately do not seek treatment due to embarrassment or other factors. After 20+ years in development, ospemifene (Osphena™) was approved by the US Food and Drug Administration in 2013 for treatment of moderate-to-severe dyspareunia associated with VVA due to menopause. As the first non-hormonal alternative to estrogen-based products for this indication, the approval of ospemifene represents a significant milestone in postmenopausal women’s health. Ospemifene is a non-steroidal estrogen receptor agonist/antagonist, also known as a selective estrogen receptor modulator (SERM), from the same chemical class as the breast cancer drugs tamoxifen and toremifene. Unlike other selective estrogen receptor modulators, ospemifene exerts a strong, nearly full estrogen agonist effect in the vaginal epithelium, making it well suited for the treatment of dyspareunia in postmenopausal women. Results of Phase III clinical trials showed that ospemifene significantly improved the vaginal maturation index (decreased parabasal cells and increased superficial cells), decreased vaginal pH, and decreased severity of the self-identified most bothersome symptom (dyspareunia or vaginal dryness) compared to placebo. Long-term safety studies revealed that 60 mg ospemifene given daily for 52 weeks was well tolerated and was not associated with any endometrium or breast-related safety concerns. This review discusses the preclinical and clinical data supporting the use of ospemifene for the treatment of dyspareunia associated with VVA due to menopause and provides an overview of its clinical safety.

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.

Ospemifene: a first-in-class, non-hormonal selective estrogen receptor modulator approved for the treatment of dyspareunia associated with vulvar and vaginal atrophy

Ospemifene is a selective estrogen receptor modulator (SERM) approved for the treatment of dyspareunia associated with vulvar and vaginal atrophy (VVA) due to menopause. As the first non-hormonal treatment for this indication, the approval of ospemifene represents a significant milestone in postmenopausal women's health. Ospemifene is a triphenylethylene similar in chemical structure to tamoxifen and toremifene. Consistent with other SERMs such as tamoxifen, toremifene, and raloxifene, ospemifene possesses a distinctive mix of estrogenic and antiestrogenic tissue-specific effects in bone, breast tissue, serum lipids, and the vagina. Among the approved SERMs, ospemifene is the only agent with a nearly full estrogen agonist effect on the vaginal epithelium while having neutral to slight estrogenic effects in the endometrium, making ospemifene uniquely suited for the treatment of dyspareunia associated with VVA, also known as atrophic vaginitis, which affects up to 50% of postmenopausal women. This review begins with a brief history of the discovery of ospemifene, its mechanism of action, and its preclinical development, with an emphasis on its tissue-specific effects on bone, breast, uterus and endometrium, serum lipids and vagina. A brief discussion on the genotoxicity of ospemifene compared to tamoxifen and toremifene is included. The focus then shifts to the clinical development of ospemifene from Phase I through Phase III. We will close with the FDA approval of ospemifene and a justification of the future clinical evaluation of ospemifene as a potential breast cancer chemopreventive agent, where several preclinical studies in different rodent breast cancer models strongly suggest ospemifene is as effective as tamoxifen.

Ospemifene: a novel selective estrogen receptor modulator for treatment of dyspareunia

Ospemifene is a novel, oral selective estrogen receptor modulator that has been approved in the USA for treatment of dyspareunia. The decline in estrogen during menopause creates vulvovaginal changes that can cause symptoms that adversely impact women psychosexually. Many women are reluctant to discuss painful sex and providers must proactively inquire about sexuality issues. Ospemifene has been shown to reverse changes associated with vulvovaginal atrophy and relieve symptoms of dyspareunia. Safety studies of treatment up to 52 weeks have shown ospemifene to be safe with no impact on endometrial hyperplasia/carcinoma, venous thrombotic events or pelvic organ prolapse. Further studies are needed to evaluate its role in bone and breast health.

An overview of current and emerging SERMs

Selective estrogen receptor modulators (SERMs) are compounds that exhibit tissue-specific estrogen receptor (ER) agonist or antagonist activity, and are used for various indications, including treatment of breast cancer, osteoporosis, and menopausal symptoms. Endometrial safety has been a key differentiator between SERMs in clinical practice. For example, tamoxifen exhibits ER agonist activity in the uterus, resulting in an increased risk of endometrial hyperplasia and malignancy, whereas raloxifene and bazedoxifene have neutral effects on the uterus. Based on their efficacy and long-term safety, SERMs are increasingly being prescribed for women who cannot tolerate other treatment options and for younger women at an increased risk of fracture who may remain on therapy for long periods of time. Continuing advances in the understanding of SERM mechanisms of action and structural interactions with the ER may lead to the development of new agents and combinations of agents to provide optimal treatments to meet the varying needs of postmenopausal women. One such example is the tissue selective estrogen complex, which partners a SERM with 1 or more estrogens, with the aim of blending the desired estrogen-receptor agonist activities of estrogens on vasomotor symptoms, vulvar-vaginal atrophy, and loss of bone mass with the tissue selectivity of a SERM.

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'.

Ospemifene, a novel selective estrogen receptor modulator for treating dyspareunia associated with postmenopausal vulvar and vaginal atrophy

OBJECTIVE

The aim of this work was to study the role of ospemifene, a novel selective estrogen receptor modulator, in the treatment of vulvar and vaginal atrophy in postmenopausal women with moderate to severe dyspareunia and physiological vaginal changes.

METHODS

This multicenter phase 3 study used a randomized, double-blind, parallel-group design to compare the efficacy, safety, and tolerability of oral ospemifene 60 mg/day versus placebo. A total of 605 women aged 40 to 80 years who self-reported a most bothersome symptom of dyspareunia and had a diagnosis of vulvar and vaginal atrophy were randomized to take a once-daily dose of ospemifene (n = 303) or placebo (n = 302) for 12 weeks.

RESULTS

Analysis of the intent-to-treat (n = 605) population found the efficacy of ospemifene to be significantly greater than that of placebo for each of the following coprimary endpoints: percentages of parabasal and superficial cells, vaginal pH, and severity of dyspareunia. With ospemifene, the percentage of parabasal cells and vaginal pH significantly decreased; the percentage of superficial cells significantly increased; and dyspareunia was significantly reduced versus placebo (all P < 0.0001, except for dyspareunia: P = 0.0001). Among the randomized women, 186 (61.4%) in the ospemifene group and 154 (51.0%) in the placebo group reported at least one treatment-emergent adverse event. Hot flushes were the most frequently reported treatment-related adverse event (ospemifene 6.6% vs placebo 3.6%); only one participant discontinued in each group. As determined by the investigators, no serious adverse events related to the study drug were reported.

CONCLUSIONS

In this study, once-daily oral ospemifene 60 mg was effective for the treatment of vulvar and vaginal atrophy in postmenopausal women with dyspareunia.

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.

Tissue selectivity of ospemifene: pharmacologic profile and clinical implications

The multifactorial consequences of menopausal estrogen deficiency affect numerous tissues throughout the body. Supplemental hormonal therapies carry the burden of a risk/benefit ratio that must be highly individualized. Selective estrogen receptor modulators (SERMs) are estrogen receptor (ER) agonist/antagonists designed to induce benefits comparable with estrogen while minimizing adverse effects. Here, we review the estrogen agonist/antagonist profile of ospemifene, a novel triphenylethylene derivative recently approved to treat dyspareunia, a symptom of vulvar and vaginal atrophy (VVA) due to menopause, both preclinically and clinically. Ospemifene binds ERα and ERβ with approximately equal affinities. In preclinical models, ospemifene increased vaginal and uterine epithelial thickness and mucification to the same extent as estrogen. Ospemifene did not induce endometrial hyperplasia in animal models; there also was no stimulatory effect on endometrial cells. In rat and human mammary cells in vitro, ospemifene evokes a dose-dependent inhibition on estrogen-induced cell responses and cell proliferation, supporting an antiestrogenic effect in breast. In contrast, ospemifene has an estrogenic effect on bone, as seen by improved bone mineral density, strength, mass, and histomorphometry in preclinical models, consistent with improvements in markers of bone resorption and formation in postmenopausal women. Based on the preclinical evidence, ospemifene has beneficial estrogen-like effects on the vaginal epithelium, preliminary evidence to support a neutral endometrial profile, antiproliferative effects in breast, and estrogenic effects in bone. Taken together, especially regarding estrogen-like effects on the vaginal epithelium, ospemifene presents a profile of tissue-specific effects that appear novel among available SERMs and well-suited for the treatment of VVA.

Vaginal effects of ospemifene in the ovariectomized rat preclinical model of menopause

Ospemifene is a unique tissue-selective estrogen agonist/antagonist (also known as a selective estrogen receptor modulator [SERM]) with demonstrated efficacy in Phase 3 studies of postmenopausal women with vulvar and vaginal atrophy (VVA). This report describes preclinical studies on the effects of ospemifene in the ovariectomized (OVX) rat model of menopause. Ospemifene (10mg/kg/day) and the SERM comparator, raloxifene (10mg/kg/day) were administered for 2 weeks and both increased vaginal weight; ospemifene was more effective than raloxifene. In addition, ospemifene had a greater effect on increasing vaginal epithelial height compared with raloxifene. The effect on uterine weight was less pronounced for both ospemifene and raloxifene. The ED50 of ospemifene on vaginal epithelial height was 0.39mg/kg/day and the magnitude was nearly the same as was seen with the positive control, 17α-ethinyl estradiol (EE2). In a histological analysis of ospemifene-treated rat vaginas, basal cells were overlaid by 2 to 3 cell layers of thickened goblet-like mucified cells apically; however, the cornification observed with EE2 was absent. Estrogenic activity of ospemifene was confirmed by upregulation of progesterone receptors in vaginal epithelium and stroma. Ospemifene showed similar affinity for estrogen receptor (ER)-α and ER-β, but an overall lower affinity than estradiol. Ospemifene antagonized estrogen response element (ERE)-mediated transactivation on MCF-7 cells, confirming its anti-estrogenic activity in breast cancer cells. The dose response for ospemifene in the rat is consistent with that observed in clinical studies of ospemifene 30 and 60mg, showing that the OVX rat is a highly predictive model of SERM activity in postmenopausal VVA.

Ospemifene for the treatment of dyspareunia associated with vulvar and vaginal atrophy: potential benefits in bone and breast

Ospemifene is a selective estrogen receptor modulator (SERM), or estrogen receptor agonist/antagonist, that was recently approved by the US Food and Drug Administration for the treatment of dyspareunia associated with vulvar and vaginal atrophy, a chronic condition that affects up to 60% of postmenopausal women. Ospemifene is the first and only nonestrogen compound approved for this indication. Compared with other approved SERMs, such as tamoxifen, toremifene, bazedoxifene, and raloxifene, the estrogen-like effects of ospemifene in the vaginal epithelium are unique. This review first discusses the rationale for developing ospemifene, including its mechanism of action, and then focuses on the clinical development of ospemifene for the treatment of dyspareunia associated with vulvar and vaginal atrophy. Included are discussions of the effects of ospemifene on the endometrium, serum lipids, coagulation markers, bone, and breast cancer. In conclusion, ospemifene is a SERM with a unique estrogen agonist/antagonist tissue profile that was recently approved in the US for the treatment of dyspareunia associated with vulvar and vaginal atrophy in postmenopausal women. Ospemifene warrants further clinical investigation for the treatment and prevention of osteoporosis and breast cancer.

Effects of ospemifene on drug metabolism mediated by cytochrome P450 enzymes in humans in vitro and in vivo

The objective of these investigations was to determine the possible effects of the novel selective estrogen receptor modulator, ospemifene, on cytochrome P450 (CYP)-mediated drug metabolism. Ospemifene underwent testing for possible effects on CYP enzyme activity in human liver microsomes and in isolated human hepatocytes. Based on the results obtained in vitro, three Phase 1 crossover pharmacokinetic studies were conducted in healthy postmenopausal women to assess the in vivo effects of ospemifene on CYP-mediated drug metabolism. Ospemifene and its main metabolites 4-hydroxyospemifene and 4′-hydroxyospemifene weakly inhibited a number of CYPs (CYP2B6, CYP2C9, CYP2C19, CYP2C8, and CYP2D6) in vitro. However, only CYP2C9 activity was inhibited by 4-hydroxyospemifene at clinically relevant concentrations. Induction of CYPs by ospemifene in cultured human hepatocytes was 2.4-fold or less. The in vivo studies showed that ospemifene did not have significant effects on the areas under the plasma concentration-time curves of the tested CYP substrates warfarin (CYP2C9), bupropion (CYP2B6) and omeprazole (CYP2C19), demonstrating that pretreatment with ospemifene did not alter their metabolism. Therefore, the risk that ospemifene will affect the pharmacokinetics of drugs that are substrates for CYP enzymes is low.

The discovery and development of selective estrogen receptor modulators (SERMs) for clinical practice

Selective estrogen receptor modulators (SERMs) are structurally different compounds that interact with intracellular estrogen receptors in target organs as estrogen receptor agonists or antagonists. These drugs have been intensively studied over the past decade and have proven to be a highly versatile group for the treatment of different conditions associated with postmenopausal women's health, including hormone responsive cancer and osteoporosis. Tamoxifen, a failed contraceptive is currently used to treat all stages of breast cancer, chemoprevention in women at high risk for breast cancer and also has beneficial effects on bone mineral density and serum lipids in postmenopausal women. Raloxifene, a failed breast cancer drug, is the only SERM approved internationally for the prevention and treatment of postmenopausal osteoporosis and vertebral fractures. However, although these SERMs have many benefits, they also have some potentially serious adverse effects, such as thromboembolic disorders and, in the case of tamoxifen, uterine cancer. These adverse effects represent a major concern given that long-term therapy is required to prevent osteoporosis or prevent and treat breast cancer. The search for the 'ideal' SERM, which would have estrogenic effects on bone and serum lipids, neutral effects on the uterus, and antiestrogenic effects on breast tissue, but none of the adverse effects associated with current therapies, is currently under way. Ospemifene, lasofoxifene, bazedoxifene and arzoxifene, which are new SERM molecules with potentially greater efficacy and potency than previous SERMs, have been investigated for use in the treatment and prevention of osteoporosis. These drugs have been shown to be comparably effective to conventional hormone replacement therapy in animal models, with potential indications for an improved safety profile. Clinical efficacy data from ongoing phase III trials are available or are awaited for each SERM so that a true understanding of the therapeutic potential of these compounds can be obtained. In this article, we describe the discovery and development of the group of medicines called SERMs. The newer SERMs in late development: ospemifene, lasofoxifene, bazedoxifene, are arzoxifene are described in detail.

Ospemifene, vulvovaginal atrophy, and breast cancer

The incidence and severity of vulvovaginal atrophy (VVA) in postmenopausal breast cancer patients has a significant impact on quality of life. While the etiology of VVA is primarily related to low estrogen levels seen in menopause, women with breast cancer have an added risk of VVA induced by a combination of chemotherapy, hormonal therapy, and menopause. Ospemifene is a new, non-hormonal selective estrogen receptor modulator (SERM) triphenylethylene derivative that is effective in treating VVA in postmenopausal women. Although other SERMs have antagonistic effects on the vagina, ospemifene exerts an estrogen-like effect on the vaginal epithelium. This review will focus on data demonstrating the antiestrogenic activity of ospemifene in several unique breast cancer animal models, and the implications for utilizing ospemifene in patients with breast cancer suffering from VVA. Additional research addressing the expanded use of ospemifene in breast cancer patients is also warranted.

Ospemifene and 4-hydroxyospemifene effectively prevent and treat breast cancer in the MTag.Tg transgenic mouse model

OBJECTIVE

Ospemifene, a new drug indicated for the treatment of vulvovaginal atrophy, has completed phase III clinical trials. A condition affecting millions of women worldwide, vulvovaginal atrophy has long been treated with estrogen therapy. Estrogen treatment carries with it risks of thromboembolism, endometrial proliferative effects, and breast cancer promotion. In this study, we test the effects of three dosing levels of ospemifene in both the prevention and treatment of breast cancer in the MTag.Tg mouse model.

METHODS

The polyomavirus middle-T transgenic mouse model (MTag.Tg), which produces synchronized, multifocal mammary tumors in the immunologically intact C57BL/6 background, was used to examine the impact of ospemifene treatment. First, a cell line derived from an MTag.Tg mouse tumor (MTag 34) was treated in vitro with ospemifene and its major metabolite, 4-hydroxyospemifene (4-OH ospemifene). MTag.Tg mice were treated daily by gavage with three different doses of ospemifene (5, 25, and 50 mg/kg) before or after the development of mammary tumors. Survival and tumor development results were used to determine the effect of ospemifene treatment on mammary tumors in both the preventive and treatment settings.

RESULTS

Tumors and the MTag 34 cell line were positive for estrogen receptor expression. The MTag 34 line was not stimulated by ospemifene or its major, active metabolite 4-OH ospemifene in vitro. Ospemifene increased survival time and exerted an antitumor effect on the development and growth of estrogen receptor-positive mammary tumors in the MTag.Tg mouse model at the 50-mg/kg dose. The levels of ospemifene and 4-OH ospemifene in both the tumors and plasma of mice confirmed the dosing. Ospemifene did not exert an estrogenic effect in the breast tissue at doses equivalent to human dosing.

CONCLUSIONS

Ospemifene prevents and treats estrogen receptor-positive MTag.Tg mammary tumors in this immune-intact mouse model in a dose-dependent fashion. Ospemifene drug levels in the plasma of treated mice were comparable with those found in humans. Combined with our previous data, ospemifene does not seem to pose a breast cancer risk in animals and slows down cancer development and progression in the MTag.Tg model.

An update on selective estrogen receptor modulators for the prevention and treatment of osteoporosis

Several selective estrogen receptor modulators are in clinical development for postmenopausal osteoporosis. Bazedoxifene has shown significant reductions in vertebral and non-vertebral (in higher-risk women) fracture risk, with no evidence of breast or endometrial stimulation. Lasofoxifene has demonstrated significant reductions in vertebral and non-vertebral fracture risk, but has been associated with endometrial/uterine effects. Both selective estrogen receptor modulators were generally safe and well tolerated but have been associated with some "class effects" (e.g., hot flushes, venous thromboembolic events). A tissue selective estrogen complex partnering bazedoxifene with conjugated estrogens is under clinical investigation for the treatment of menopausal symptoms and osteoporosis prevention. Future directions in selective estrogen receptor modulator research include ospemifene and RAD 1901.

What is the best balance of benefits and risks among anti-resorptive therapies for postmenopausal osteoporosis?

Pharmacologic osteoporosis therapy, particularly anti-resorptives, is recommended in postmenopausal women with clinical risk factors for fracture. Treatment decisions should be made based on the relative benefit-risk profile in different patient populations. Emerging options [e.g., selective estrogen receptor modulators (SERMs) and denosumab] may hold promise for providing protection from bone loss and for fracture risk reduction.Osteoporosis, the most common clinical disorder of bone metabolism, is characterized by low bone mineral density, deterioration of microarchitecture, and a consequent increase in bone fragility and risk of fracture. Pharmacologic therapy is recommended in postmenopausal women with clinical risk factors for fracture and includes anti-resorptive agents such as bisphosphonates, hormone therapy, SERMs, and calcitonin. The anabolic agent teriparatide (parathyroid hormone) is usually reserved for high-risk patients or those with glucocorticoid-induced osteoporosis. Strontium ranelate, available outside the USA, has both anti-resorptive and anabolic properties. Supplementation with calcium and vitamin D is recommended for all women aged 50 years and older. Bisphosphonates are often considered first-line therapy for osteoporosis and have the largest base of clinical trial data showing efficacy for global fracture risk reduction. Low-dose hormone therapy is appropriate for younger women who are experiencing other menopausal symptoms. In women for whom bisphosphonates are not appropriate or not tolerated or in younger postmenopausal women who have a low risk for hip fracture, SERMs are a suitable treatment option. Calcitonin is designated for patients who are unable or unwilling to tolerate other osteoporosis agents. Emerging options, including newer SERMs (e.g., bazedoxifene and lasofoxifene) and the monoclonal antibody denosumab, may hold promise for providing protection from bone loss and for fracture risk reduction. Because no single agent is appropriate for all patients, treatment decisions should be made on an individual basis, taking into account the relative benefits and risks in different patient populations.

Endometrial safety: a key hurdle for selective estrogen receptor modulators in development

Selective estrogen receptor modulators (SERMs) have the ability to provide mixed functional estrogen receptor (ER) agonist or antagonist activity, depending on the target tissue. Tamoxifen, the first SERM available for clinical use, is regarded as a highly effective agent for the prevention and treatment of breast cancer. However, tamoxifen exhibits ER agonist activity in the uterus and is associated with an increased risk of endometrial hyperplasia and malignancy. Endometrial safety has been an important consideration in the clinical development of SERMs, with improved benefit-risk profiles. Raloxifene, which is currently approved for the prevention and treatment of postmenopausal osteoporosis and for the prevention of breast cancer, seems to have neutral effects on the uterus. Promising results have been observed with the targeted development of newer and more tissue-specific SERMs, many of which are under investigation for postmenopausal osteoporosis. Of the newer SERMs in development, lasofoxifene has been shown to reduce fracture risk and decrease the incidence of breast cancer but has been associated with an increased incidence of vaginal bleeding, endometrial thickening, and endometrial polyps. Lasofoxifene and ospemifene have shown beneficial effects on the vaginal epithelium. Phase 3 clinical data have shown that bazedoxifene is effective in preventing and treating postmenopausal osteoporosis, without adverse effects on the endometrium or breast. Arzoxifene has been evaluated in phase 3 trials for postmenopausal osteoporosis and has been studied for the treatment of uterine malignancies but is no longer in clinical development. Further investigation of newer SERMs is warranted to more clearly define the endometrial safety of these agents.

Ospemifene effectively treats vulvovaginal atrophy in postmenopausal women: results from a pivotal phase 3 study

OBJECTIVE

The aim of this study was to study the efficacy and safety of ospemifene, a new selective estrogen receptor modulator, in the treatment of vulvovaginal atrophy in postmenopausal women.

METHODS

A randomized, double-blind phase 3 study in which 826 postmenopausal women were randomized 1:1:1 to receive treatment with ospemifene 30 or 60 mg/day or placebo orally for 12 weeks was conducted. The primary inclusion criteria were having 5% or less superficial cells on the vaginal smear (maturation index), vaginal pH greater than 5.0, and at least one moderate or severe symptom of vulvovaginal atrophy. The four coprimary endpoints were the change from baseline to 12 weeks in the percentage of superficial and parabasal cells on the vaginal smear, change in vaginal pH, and change in severity of most bothersome symptom (vaginal dryness or dyspareunia) compared with placebo. All participants were given a nonhormonal vaginal lubricant for use as needed.

RESULTS

Ospemifene was statistically significantly superior to placebo in each of the coprimary endpoints at the 60-mg dose. Statistically significant results were achieved for all coprimary endpoints with the 30-mg dose except for dyspareunia. Ospemifene was well tolerated at both doses and demonstrated a favorable safety profile.

CONCLUSIONS

Ospemifene was shown to be effective and well tolerated for the treatment of the symptoms of vaginal dryness and dyspareunia associated with vulvovaginal atrophy over and above the use of provided lubricants.

SERMs in the prevention and treatment of postmenopausal osteoporosis: an update

Selective estrogen receptor modulators (SERMs) have the ability to bind the estrogen receptor (ER) and are known to confer ER agonist or antagonist effects depending on the target tissue. A number of newer SERMs, including bazedoxifene, lasofoxifene and ospemifene, are currently under clinical development for the prevention and treatment of postmenopausal osteoporosis and for other indications. Although the possibility of developing a single agent that has all of the desired characteristics of an ideal SERM seems to be unlikely, progress in the clinical development of SERMs targeted to the ER suggests that these newer compounds may have attributes that represent an improvement relative to existing SERMs. A new approach to menopausal therapy is the tissue selective estrogen complex or the pairing of a selective estrogen receptor modulator with estrogens. Further investigation will help to clarify relative benefits/risks of novel SERMs in development within specific indications.

Effect of toremifene and ospemifene, compared to acolbifene, on estrogen-sensitive parameters in rat and human uterine tissues

BACKGROUND

Although the first generation selective estrogen receptor modulator (SERM) tamoxifen (TAM) is well known for its uterotrophic activity, this study compares the stimulatory effect of the TAM derivatives toremifene (TORE) and ospemifene (OSPE) on estrogen-sensitive parameters in rat and human uterine tissues.

MATERIAL AND METHODS

Ovariectomized female rats were treated daily orally for 10 days with 0.75 mg/rat of TORE, OSPE or acolbifene (ACOL, a pure estrogen antagonist in the uterus and mammary gland), which was used for comparison. Human endometrial carcinoma Ishikawa cells were incubated for 5 days with increasing doses of compounds, in the absence or presence of 1 nM estradiol (E2).

RESULTS

TORE and OSPE revealed 52% and 56% increases, respectively, in uterine weight, whereas ACOL had no effect. Similar effects were observed on vaginal weight. Endometrial epithelial height increased from 15.82±0.20 to 48.94± 2.12 and 42.14±1.95 μm with TORE and OSPE, respectively, whereas ACOL had no effect. Alkaline phosphatase activity, an estrogen-sensitive parameter in Ishikawa cells, was increased by 144% and 135% with OH-TORE and OH-OSPE, respectively. Owing to their intrinsic estrogenic activity, at maximal concentrations, OH-TORE and OH-OSPE blocked the stimulatory effect of E2 by only 89% compared to 100% with ACOL.

CONCLUSIONS

The present in vitro and in vivo data show similar stimulatory effects of 4-hydroxytoremifene (OH-TORE) and OH-OSPE on estrogen-sensitive parameters. ACOL, a third generation SERM, has no effect on any of these parameters. Such data add to the potential uterine safety limitations of triphenylethylene-derived SERMs for long-term use in humans.

Polymorphism of human cytochrome P450 enzymes and its clinical impact

Pharmacogenetics is the study of how interindividual variations in the DNA sequence of specific genes affect drug response. This article highlights current pharmacogenetic knowledge on important human drug-metabolizing cytochrome P450s (CYPs) to understand the large interindividual variability in drug clearance and responses in clinical practice. The human CYP superfamily contains 57 functional genes and 58 pseudogenes, with members of the 1, 2, and 3 families playing an important role in the metabolism of therapeutic drugs, other xenobiotics, and some endogenous compounds. Polymorphisms in the CYP family may have had the most impact on the fate of therapeutic drugs. CYP2D6, 2C19, and 2C9 polymorphisms account for the most frequent variations in phase I metabolism of drugs, since almost 80% of drugs in use today are metabolized by these enzymes. Approximately 5-14% of Caucasians, 0-5% Africans, and 0-1% of Asians lack CYP2D6 activity, and these individuals are known as poor metabolizers. CYP2C9 is another clinically significant enzyme that demonstrates multiple genetic variants with a potentially functional impact on the efficacy and adverse effects of drugs that are mainly eliminated by this enzyme. Studies into the CYP2C9 polymorphism have highlighted the importance of the CYP2C9*2 and *3 alleles. Extensive polymorphism also occurs in other CYP genes, such as CYP1A1, 2A6, 2A13, 2C8, 3A4, and 3A5. Since several of these CYPs (e.g., CYP1A1 and 1A2) play a role in the bioactivation of many procarcinogens, polymorphisms of these enzymes may contribute to the variable susceptibility to carcinogenesis. The distribution of the common variant alleles of CYP genes varies among different ethnic populations. Pharmacogenetics has the potential to achieve optimal quality use of medicines, and to improve the efficacy and safety of both prospective and currently available drugs. Further studies are warranted to explore the gene-dose, gene-concentration, and gene-response relationships for these important drug-metabolizing CYPs.

Designing the ideal selective estrogen receptor modulator--an achievable goal?

Selective estrogen receptor modulators (SERMs), which lack the estrogen steroid moiety yet retain the ability to bind the estrogen receptor (ER), are known to confer mixed ER agonist or antagonist effects depending on the target tissue. The tissue-selective effects of SERMs have led to considerations in the clinical profile of an ideal SERM, which would have ER agonist activity in tissues where mimicking the action of estrogens is desirable, and ER neutral or antagonist activity in tissues estrogens have been shown to adversely stimulate. A number of newer SERMs, including bazedoxifene, lasofoxifene, ospemifene, and arzoxifene, are currently in clinical development for the prevention and treatment of postmenopausal osteoporosis and for other indications. Although the possibility of developing a single agent that has all of the desired characteristics of an ideal SERM seems to be unlikely, progress in the clinical development of SERMs targeted to the ER suggests that these newer compounds may have attributes that represent an improvement relative to existing SERMs. Further clinical investigation will help to clarify the relative benefits and risks of novel SERMs in development within specific indications.