Effects of bazedoxifene on BMD and bone turnover in postmenopausal women: 2-yr results of a randomized, double-blind, placebo-, and active-controlled study

Regulation of bone metabolism by nuclear receptors

Bone tissue protects and supports soft organs and maintains calcium homeostasis. Steroid sex hormones and fat-soluble vitamins play a pivotal role in regulation of bone homeostasis, turnover and remodeling. These molecules act as ligands of nuclear receptors, through which they control gene expression in bone cells, namely bone-forming osteoblasts, bone-resorptive osteoclasts and osteocytes. Significant advances in our understanding of nuclear receptor physiology have been achieved due to development of novel genetic manipulation approaches and generation of experimental animal models in which nuclear receptor genes were mutated in specific cell types. In this review, we summarized some aspects of recent progress in studies on molecular mechanisms of cell-specific action of nuclear hormone receptors in bone tissue.

New therapies for osteoporosis: zoledronic acid, bazedoxifene, and denosumab

Intravenous (IV) zoledronic acid, a new once-yearly bisphosphonate therapy, is approved by the US Food and Drug Administration for treatment of postmenopausal osteoporosis, glucocorticoid-induced osteoporosis, and osteoporosis in men. IV zoledronic acid significantly reduced the risk of vertebral, nonvertebral, and hip fractures in postmenopausal women and decreased risk of clinical fracture and clinical vertebral fracture in men and women with hip fracture. Two promising new therapies are in late clinical development. Denosumab is a monoclonal receptor activator of nuclear factor- kappaB ligand (RANKL) antibody given by subcutaneous injection every 6 months that has been shown to significantly reduce risk of vertebral-, nonvertebral-, and hip fracture in postmenopausal women. Bazedoxifene, an estrogen agonist/antagonist, has significantly reduced the risk of vertebral fracture in postmenopausal women; a post hoc analysis showed reduction in risk of nonvertebral fracture in high-risk women.

Pharmacology and clinical applications of selective estrogen receptor modulators

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

Bazedoxifene/conjugated estrogens and quality of life in postmenopausal women

OBJECTIVE

To assess the effects of bazedoxifene/conjugated estrogens (BZA/CE) on sleep parameters and health-related quality of life (HR-QOL).

METHODS

This was a 12-week, multicenter, double-blind, placebo-controlled phase 3 study. Postmenopausal women with an intact uterus and experiencing >or=7 moderate-to-severe hot flushes daily were randomized to BZA 20 mg/CE 0.45 mg, BZA 20 mg/CE 0.625 mg, or placebo. In these secondary efficacy analyses, the Medical Outcomes Study (MOS) sleep scale and Menopause-Specific Quality of Life (MENQOL) questionnaires and the Menopause Symptoms Treatment Satisfaction Questionnaire (MS-TSQ) evaluated measures of sleep, menopausal symptoms, and satisfaction with treatment, respectively.

RESULTS

A total of 318 subjects (mean age, 53.4 years) received >or=1 dose of study drug. At Week 12, BZA 20 mg/CE 0.45 and 0.625 mg showed significant improvements over placebo in the MOS sleep scale for time to fall asleep, sleep adequacy, sleep disturbance, and sleep problems indexes I and II (P<0.001). A reduction in hot flush frequency was significantly associated with improvement in sleep parameters (P<0.05) based on linear regression and responder analyses. Both BZA/CE doses showed significantly greater improvements over placebo in vasomotor function and total MENQOL score (P<0.001). Results of the MS-TSQ showed that subjects treated with BZA/CE versus placebo reported significantly greater overall satisfaction with treatment (P<0.05), as well as greater satisfaction with sleep quality, ability to control hot flushes during the day and night, effect on mood/emotions, and tolerability.

CONCLUSION

Symptomatic postmenopausal women treated with BZA/CE experienced significant improvements in sleep parameters and overall HR-QOL.

Efficacy of tissue-selective estrogen complex of bazedoxifene/conjugated estrogens for osteoporosis prevention in at-risk postmenopausal women

OBJECTIVE

To evaluate the efficacy of the tissue-selective estrogen complex, bazedoxifene/conjugated estrogens (BZA/CE), for postmenopausal osteoporosis prevention.

DESIGN

Multicenter, randomized, double-blind, placebo- and active-controlled, phase 3 trial (Selective estrogen Menopause And Response to Therapy [SMART]-1).

SETTING

Outpatient clinical study.

PATIENT(S)

Women (n = 3,397) more than 5 years and 1-5 years postmenopause were enrolled in the Osteoporosis Prevention I and II Substudies, respectively.

INTERVENTION(S)

Single tablets of BZA (10, 20, or 40 mg) each with CE (0.625 or 0.45 mg), raloxifene (60 mg), or a placebo taken daily for 2 years.

MAIN OUTCOME MEASURE(S)

The primary outcome for both substudies was change in bone mineral density of the lumbar spine; bone mineral density was also measured at the hip.

RESULT(S)

In both substudies, bone mineral density increased significantly more with all BZA/CE doses compared with placebo at the lumbar spine and total hip, and for most BZA/CE doses compared with raloxifene at the lumbar spine. Osteocalcin and N-telopeptide significantly decreased with all BZA/CE doses vs. placebo and most BZA/CE doses vs. raloxifene.

CONCLUSION(S)

BZA/CE combinations decreased bone turnover and bone loss in postmenopausal women at increased risk for osteoporosis.

Evaluation of bazedoxifene/conjugated estrogens for the treatment of menopausal symptoms and effects on metabolic parameters and overall safety profile

OBJECTIVE

To evaluate the effects of a tissue-selective estrogen complex (TSEC) composed of bazedoxifene/conjugated estrogens (BZA/CE) on menopausal symptoms, metabolic parameters, and overall safety.

DESIGN

Multicenter, double-blind, placebo- and active-controlled phase 3 trial (Selective estrogens, Menopause, And Response to Therapy [SMART]-1).

SETTING

Outpatient clinical.

PATIENT(S)

Healthy, postmenopausal women (n = 3,397) age 40 to 75 with an intact uterus.

INTERVENTION(S)

Single tablets of BZA (10, 20, or 40 mg), each with CE (0.625 or 0.45 mg); raloxifene 60 mg; or placebo taken daily for 2 years.

MAIN OUTCOME MEASURE(S)

Hot flushes, breast pain, vaginal atrophy, metabolic parameters, and adverse events.

RESULT(S)

BZA (20 mg)/CE (0.625 or 0.45 mg) significantly reduced the frequency and severity of hot flushes and improved measures of vaginal atrophy compared with placebo. At week 12, the daily number of hot flushes decreased by 51.7% to 85.7% with all BZA/CE doses vs. 17.1% for placebo. BZA/CE improved lipid parameters and homocysteine levels, did not significantly change carbohydrate metabolism, and had only minor effects on some coagulation parameters. The incidences of breast pain and adverse events were similar between BZA/CE and placebo.

CONCLUSION

The TSEC composed of BZA (20 mg)/CE (0.625 or 0.45 mg) is an effective and safe treatment for menopausal symptoms.

Advances in the Treatment of Menopausal Symptoms

Vasomotor symptoms and vaginal atrophy are both common menopausal symptoms. Hormone therapy is currently the only FDA-approved treatment for hot flashes. Current recommendations are to use the lowest dose of hormone therapy for the shortest period that will allow treatment goals to be met. Although the reanalysis of the WHI in 2007 by Roussow et al. provided evidence of coronary heart safety for users of hormone therapy under the age of 60 years and within 10 years of the onset of menopause, not all women desire or are candidates for hormone therapy. In this review we present an evidence-based discussion considering the effectiveness of hormonal and nonhormonal therapies for the relief of vasomotor symptoms and vaginal atrophy. Concern exists regarding systemic absorption of vaginal estrogen and possible adverse effects on the breast and uterus. Selective estrogen receptor modulators and estrogen agonists offer benefits through targeted estrogen agonist/antagonistic effects and are being evaluated with and without estrogen for symptomatic menopausal women. Centrally acting nonhormonal therapies that are effective for the relief of vasomotor symptoms include various antidepressants, gabapentin and clonidine. A limited number of clinical trials have been conducted with nonprescription remedies, including paced respiration, yoga, acupuncture, exercise, homeopathy and magnet therapy, and some, but not all of these, have been found to be more effective than placebo. Dietary herbal supplements, such as soy and black cohosh, have demonstrated mixed and inconclusive results in placebo-controlled trials. Potential therapies for vasomotor symptoms and vaginal atrophy require randomized, placebo-controlled trials of sufficient duration to establish efficacy and safety. Agents under investigation for vasomotor symptoms relief include neuroactive agents, such as gabapentin and desvenlafaxine; an estrogen receptor-β-targeted herbal therapy, MF-101; and the selective estrogen receptor modulator, bazedoxifene, paired with estrogen.

Bazedoxifene reduces vertebral and clinical fractures in postmenopausal women at high risk assessed with FRAX

INTRODUCTION

Bazedoxifene has been shown to significantly decrease the risk of vertebral fractures in postmenopausal women. No significant effect was noted on the risk of clinical fractures, but fracture risk reduction was reported in a post hoc subgroup analysis in a high risk group categorised on the basis of BMD and prior fracture.

AIMS

The aim of this study was to re-evaluate the efficacy of bazedoxifene on fracture outcomes avoiding subgroup analysis by examining the efficacy of intervention as a function of fracture risk.

METHODS

The phase III study was a double-blind, randomised, placebo- and raloxifene-controlled randomised 3-year multinational study that enrolled 7492 osteoporotic women aged 55 years or more (mean age=66 years). For the present analysis, women taking raloxifene were excluded (n=1849), and we compared the effects of two doses of bazedoxifene (20 and 40 mg daily combined) with placebo on the risk of all clinical fractures as well as the risk of morphometric vertebral fracture. The risk of a major osteoporotic fracture was assessed using region specific FRAX algorithms, and the relationship between pre hoc 10-year fracture probabilities and efficacy examined by Poisson regression.

RESULTS

Overall, bazedoxifene was associated with a significant 39% decrease in incident morphometric vertebral fractures (hazard ratio HR=0.61; 95% CI=0.43-0.86; p=0.005) and a non-statistically significant 16% decrease in all clinical fractures (hazard ratio HR=0.84; 95% CI=0.67-1.06; p=0.14) compared to placebo. Hazard ratios for the effect of bazedoxifene on all clinical fractures decreased with increasing fracture probability. In patients with 10-year fracture probabilities at or above 16%, bazedoxifene was associated with a significant decrease in the risk of all clinical fractures. The 16% probability threshold corresponded to the 80th percentile of the study population. Hazard ratios for the effect of bazedoxifene on morphometric vertebral fractures also decreased with increasing fracture probability. In patients with 10-year fracture probabilities above 6.9% (corresponding to the 41st percentile), bazedoxifene was associated with a significant decrease in the risk of morphometric vertebral fractures. At equivalent fracture probability percentiles, the treatment effect of bazedoxifene was greater on vertebral fracture risk than on the risk of all clinical fractures. For example, at the 90th percentile of FRAX probability, bazedoxifene was associated with a relative risk reduction of 33% (95% CI=7-51%) for all clinical fractures and 51% reduction (95% CI=21-69%) for morphometric vertebral fractures. The findings were robust to several sensitivity analyses.

CONCLUSION

Bazedoxifene (20 and 40 mg doses combined) significantly decreased the risk of all clinical fractures and morphometric vertebral fractures in women at or above a FRAX based fracture probability threshold. These results, consistent with the previous subgroup analysis, suggest that bazedoxifene should be targeted preferentially to women at high fracture risk.

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.

Effects of various selective estrogen receptor modulators with or without conjugated estrogens on mouse mammary gland

Selective estrogen receptor modulators (SERMs) are small molecules that, depending on the end point measured, may either function as estrogen receptor (ER) agonists or antagonize estrogens' agonist activity. A key feature of SERMs is the inhibition of ER agonist action on the uterus and mammary gland, but the degree of antagonism varies among compounds and end points. Bazedoxifene is a SERM that is being clinically evaluated both as a monotherapy for the prevention and treatment of osteoporosis and in combination with conjugated estrogens (CEs) for the treatment of menopausal symptoms and prevention of osteoporosis. The studies reported here compare the relative ER agonist and antagonist effects of three pharmacologically distinct SERMs (bazedoxifene, raloxifene, and lasofoxifene) on the ovariectomized mouse when administered alone or as a tissue-selective estrogen complex, a term used to describe the partnering of a SERM and one or more estrogens. At the minimum dose required to maximally reduce CE-stimulated uterine wet weight increase for each SERM, the degree of inhibition varied among the SERMs, with a rank order of bazedoxifene approximately raloxifene > lasofoxifene, in which only bazedoxifene was statistically similar to vehicle. In the mammary gland, in which amphiregulin mRNA and morphological effects were measured, bazedoxifene generally exhibited less agonist activity and was a more effective antagonist of CE than raloxifene or lasofoxifene. In summary, in an animal model evaluating estrogen-modulated uterine effects and mammary gland development, bazedoxifene exhibited less ER agonist activity than raloxifene or lasofoxifene, and, as a tissue-selective estrogen complex, bazedoxifene/CE demonstrated less mammary gland stimulation than raloxifene/CE and lasofoxifene/CE.

Estrogen agonists/antagonists in combination with estrogen for prevention and treatment of menopause-associated signs and symptoms

For several decades, clinicians have been prescribing hormone therapy to postmenopausal women for approved indications, including the alleviation of vasomotor symptoms, relief of vaginal dryness and prevention of osteoporosis. Numerous publications have demonstrated that estrogen also induces favorable effects on lipids, the endothelium, cardiovascular outcomes, quality of life, cognition, skin and urinary incontinence. As a result of these findings, clinicians began adding each of these outcomes to their list of possible benefits of hormone therapy in postmenopausal women. Results from the Women's Health Initiative significantly changed this treatment paradigm and opened the door for new, innovative therapies for the prevention of clinical conditions encountered by women of menopausal age. One such treatment option is the estrogen agonist/antagonist. In this regard, investigators and clinicians alike seek a therapy that will act like estrogen in all the 'right' tissues and act as an estrogen antagonist in tissues in which estrogen action results in adverse events. This review describes the molecular actions of estrogen agonists/antagonists, discusses the current clinical data regarding the effect of these compounds on menopause-associated outcomes, and describes what is currently known about the effects of combining estrogen with an estrogen agonist/antagonist.

Bazedoxifene: a selective estrogen-receptor modulator

Bazedoxifene is a third-generation selective estrogen-receptor modulator being developed for use alone or in combination with estrogen for prevention and treatment of osteoporosis in postmenopausal women. Preliminary clinical trials are encouraging. Bazedoxifene has been found to be efficacious in reducing bone turnover without adverse effects of breast pain. In Phase III studies, bazedoxifene was found to increase vasomotor symptoms when compared with placebo. This effect is similar to that of raloxifene. Lack of endometrial stimulation is another advantage. Current literature suggests that bazedoxifene is likely to be safe, well tolerated and effective for the treatment of postmenopausal osteoporosis. However, completion of Phase III clinical trials will further elucidate its safety and efficacy, as well as its advantages in comparison with other selective estrogen-receptor modulators.

Efficacy of bazedoxifene in reducing new vertebral fracture risk in postmenopausal women with osteoporosis: results from a 3-year, randomized, placebo-, and active-controlled clinical trial

In this 3-yr, randomized, double-blind, placebo- and active-controlled study, healthy postmenopausal women with osteoporosis (55-85 yr of age) were treated with bazedoxifene 20 or 40 mg/d, raloxifene 60 mg/d, or placebo. The primary endpoint was incidence of new vertebral fractures after 36 mo; secondary endpoints included nonvertebral fractures, BMD, and bone turnover markers. Among 6847 subjects in the intent-to-treat population, the incidence of new vertebral fractures was significantly lower (p < 0.05) with bazedoxifene 20 mg (2.3%), bazedoxifene 40 mg (2.5%), and raloxifene 60 mg (2.3%) compared with placebo (4.1%), with relative risk reductions of 42%, 37%, and 42%, respectively. The treatment effect was similar among subjects with or without prevalent vertebral fracture (p = 0.89 for treatment by baseline fracture status interaction). The incidence of nonvertebral fractures with bazedoxifene or raloxifene was not significantly different from placebo. In a posthoc analysis of a subgroup of women at higher fracture risk (femoral neck T-score <or= -3.0 and/or >or=1 moderate or severe vertebral fracture or multiple mild vertebral fractures; n = 1772), bazedoxifene 20 mg showed a 50% and 44% reduction in nonvertebral fracture risk relative to placebo (p = 0.02) and raloxifene 60 mg (p = 0.05), respectively. Bazedoxifene significantly improved BMD and reduced bone marker levels (p < 0.001 versus placebo). The incidence of vasodilatation, leg cramps, and venous thromboembolic events was higher with bazedoxifene and raloxifene compared with placebo. In conclusion, bazedoxifene significantly reduced the risk of new vertebral fracture in postmenopausal women with osteoporosis and decreased the risk of nonvertebral fracture in subjects at higher fracture risk.

Bazedoxifene for the prevention of postmenopausal osteoporosis

Bazedoxifene acetate is a novel, chemically distinct selective estrogen receptor modulator (SERM) that has been specifically developed after a stringent preclinical screening in order to obtain favorable effects on the skeleton and lipid metabolism with the additional improvement of a neutral effect on hot flushes and without stimulating the uterus or the breast. In both preclinical and clinical studies this SERM was shown to maintain BMD, prevent fractures, and reduce total cholesterol. Moreover, bazedoxifene also showed an improved uterine profile and demonstrated estrogen antagonistic activity on the endometrium. Importantly, this latter capacity has led to the development of a novel class of menopausal therapy called tissue selective estrogen complex (TSEC), in which bazedoxifene is combined with conjugated estrogen. The rationale for selecting bazedoxifene as the SERM in this TSEC combination is that it may offset estrogen stimulation of endometrial and breast tissue, without the necessity of using a progestin in women with an intact uterus, without aggravating menopausal vasomotor symptoms, but with an additive effect on bone. Preliminary data from phase 3 clinical trials appear to confirm this hypothesis, showing a greater effect of bazedoxifene on BMD with respect to raloxifene, coupled with efficacy on menopausal vasomotor symptoms not achieved by SERM alone. These properties and the safety profile of this combination, if confirmed long-term in ongoing phase 3 trials, might significantly affect the way women and physicians approach menopause and its related disorders.