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Selective estrogen receptor modulators.

Selective estrogen receptor modulators are a growing class of nonsteroidal compounds with estrogen-like actions in bone, lipid metabolism, and antiestrogenic actions in the breast. Tamoxifen and its derivatives have a weak estrogenic action in the uterus and are responsible for endometrial hyperplasia. Raloxifene does not stimulate endometrial growth but is less effective than tamoxifen for the treatment of patients with breast cancer. The duality of selective estrogen receptor modulators and 1 7B-estradiol actions is explained by several hypotheses referring to the molecular biology of estrogen receptor. Clinical trials are conducted with raloxifene in post-menopausal women. The results show a significant decrease in vertebral fracture risk and a decrease of low-density lipoprotein cholesterol, with no change in triglyceride levels. Endometrial thickness does not change. Interestingly, the risk for newly diagnosed breast cancer decreases significantly with no change in risk for estrogen receptor-negative tumors. Selective estrogen receptor modulators might change the way we manage hormone replacement therapy of postmenopausal women.

Bone Density↗

Clinical use of selective estrogen receptor modulators.

Selective estrogen receptor modulators (SERMs) are an exciting category of drugs for physicians providing healthcare to women. This article explores their pharmacology, effects on target organs and clinical effectiveness.

Breast Neoplasms↗

In search of optimal long-term female hormone replacement: the potential of selective estrogen receptor modulators.

Selective estrogen receptor modulators (SERMs) comprise a group of structurally diverse compounds which are distinguished from estrogens by their ability to interact with the estrogen receptor but to act as either an estrogen agonist or antagonist depending on the target tissue and hormonal milieu. The mechanisms by which SERMs elicit tissue-specific responses are being intensively investigated, and recently a novel pathway for estrogen receptor-mediated gene activation by the SERM raloxifene has been demonstrated. The tissue-specific activity of SERMs suggests that they may be clinically useful as, for example, potential substitutes for long-term female hormone replacement therapy. Large-scale clinical testing currently in progress for raloxifene, and soon to begin for other SERMs, will evaluate this important potential.

Aged↗

Selective estrogen receptor modulation: the search for an ideal hormonal therapy for breast cancer.

Female hormones, especially estrogens, play an important role in the pathogenesis of breast neoplasms and are a principal determinant of their biological behavior. Endocrine manipulation through medical or surgical means can often lead to objective shrinkage of breast tumors. Tamoxifen, a triphenylethylene estrogen receptor modulator, is currently the most widely used hormonal treatment for breast cancer. It has been conclusively demonstrated to reduce the risk of relapse following definitive local therapy (and systemic chemotherapy, when indicated) of invasive or noninvasive breast cancer. Recently, it has also been shown to reduce the incidence of breast cancer in healthy women who are at high risk of developing the disease. In addition, it can prevent osteoporosis and reduce the risk of fractures in postmenopausal women. However, its use is also complicated by an increased incidence of endometrial hyperplasia/carcinoma, venous thromboembolism, cataracts, and in some cases, emergence of tamoxifen-dependent clones of breast cancer. These side effects (except cataracts) are believed to be related to estrogen-agonist effects of tamoxifen. Newer drugs, which are "pure antiestrogens" or inhibitors of estrogen biosynthesis, are devoid of such estrogen-agonist activity and may not have the liability of many of these side effects. However, these agents would also be expected to lack the potentially beneficial effects of tamoxifen on lipids and skeletal system. The ability of tamoxifen to act as an estrogen-agonist or estrogen-antagonist in a tissue-specific fashion has led to the concept of selective estrogen-receptor modulation. Selective estrogen receptor modulators (SERMs), which are devoid of estrogen-agonist effects on the uterus or breast cancer cells but retain potentially beneficial effects on bones and lipids, have been described as "ideal" SERMs. A number of such compounds are currently being tested. Raloxifene is already approved for prevention of osteoporosis and has potential efficacy for prevention and treatment of breast cancer. An analogue of raloxifene, LY353381, is currently in Phase II clinical trials for treatment of breast cancer, with promising early results. EM800 and CP336156 are other promising ideal SERMs in clinical trials. These compounds may provide better treatment and chemoprevention alternatives for breast cancer as compared to tamoxifen, aromatase inhibitors, and pure antiestrogens. In addition, they may also prove to be useful for the treatment and prevention of prostate cancer as well as for treating benign gynecological diseases such as fibroids and endometriosis. Future laboratory efforts should focus on further broadening the efficacy profile of SERMs (e.g., prevention of Alzheimer's disease and elevation of high-density lipoproteins to improve the likelihood of cardiovascular benefit) and narrowing their side-effect profile (e.g., risk of thromboembolism and hot flashes).

Antineoplastic Agents, Hormonal↗

Photochemical synthesis of N-arylbenzophenanthridine selective estrogen receptor modulators (serms).

Selective estrogen receptor modulators are an emerging class of pharmaceutically important molecules. Many compounds in this class contain an aminoethoxyaryl moiety attached to a polycyclic framework at an asymmetric carbon atom. To assess whether this carbon atom can be replaced by nitrogen, we have employed a Ninomiya enamide photocyclization for the rapid synthesis of a novel N-arylbenzophenanthridine framework, 4. Further elaboration of 4 into a new structural class of achiral, nonsteroidal estrogen receptor modulators is described.

Animals↗

Selective estrogen receptor modulators: tissue selectivity and differential uterine effects.

Selective estrogen receptor modulators (SERMs) are compounds that bind to estrogen receptors and produce estrogen-like (agonist) effects in some tissues and estrogen-blocking (antagonist) effects in other tissues. One of the goals of SERM research has been to develop compounds that provide the potential benefits of estrogen in the skeleton and cardiovascular system, but avoid the negative effects of estrogen in other tissues. Estrogen therapy has been consistently associated with endometrial stimulation, including glandular proliferation, hyperplasia and cancer. In contrast, the presence or degree of endometrial stimulation observed with SERMs varies by compound. The purpose of this review is to differentiate the endometrial effects of compounds that display a SERM-like profile. Molecular mechanisms involving SERM binding to estrogen receptors, preclinical uterine effects in both tissue culture and animal models, and endometrial findings in clinical experience are discussed. There are several SERMs commercially available or in development. The favorable safety profile of raloxifene in the uterus differentiates it from the others. Future SERM development will continue to focus on finding compounds that exhibit minimal endometrial stimulation.

Animals↗

Elucidation of the molecular mechanism of action of selective estrogen receptor modulators.

The term selective estrogen receptor modulator (SERM) describes a group of pharmaceuticals that manifest estrogen receptor (ER) agonist activity in some tissues but opposes estrogen action in others. Although the name describing this class of drugs is new, the concept is not, as compounds exhibiting tissue-selective ER agonist/antagonist properties have been available for nearly 40 years. What is new is the idea that it may be possible to capitalize on the paradoxical activities of SERMs and develop them as target organ-selective ER agonists for the treatment of osteoporosis and other estrogenopathies. This realization has provided the impetus for research in this area, the progress of which is described in this review.

Estradiol↗

Definition of the molecular and cellular mechanisms underlying the tissue-selective agonist/antagonist activities of selective estrogen receptor modulators.

The term selective estrogen receptor modulators describes a group of pharmaceuticals that function as estrogen receptor (ER) agonists in some tissues but that oppose estrogen action in others. Although the name for this class of drugs has been adopted only recently, the concept is not new, as compounds exhibiting tissue-selective ER agonist/antagonist properties have been around for nearly 40 years. What is new is the idea that it may be possible to capitalize on the paradoxical activities of these drugs and develop them as target organ-selective ER agonists for the treatment of osteoporosis and other estrogenopathies. This realization has provided the impetus for research in this area, the progress of which is discussed in this review.

Animals↗

The past, present, and future of selective estrogen receptor modulation.

The recognition of selective estrogen receptor modulation in the mid-1980s provided a unique opportunity to develop multifunctional drugs. Tamoxifen, the first selective estrogen receptor modulator (SERM), is the first antiestrogen to be tested successfully for the prevention of breast cancer in high-risk women. However, the recognition that SERMs maintain bone density and lower circulating cholesterol suggested that the prevention of osteoporosis and coronary heart disease would be beneficial side effects of tamoxifen treatment. This hypothesis has not been pursued in clinical trial, but an alternate hypothesis, that SERMs could be developed to prevent osteoporosis and potentially reduce the risk of breast cancer, has been pursued with raloxifene. Current molecule modeling of the SERM-ER complex has identified the reason for the promiscuous estrogen-like actions of tamoxifen compared with raloxifene. Future studies of the signal transduction pathways of the ER alpha (alpha)- and beta (beta)-SERM complexes hold the promise of new drug discoveries and a menu of preventive medicine in clinical practice.

Animals↗

Selective estrogen receptor modulators: a look ahead.

Selective estrogen receptor modulators (SERMs) are structurally diverse compounds that bind to estrogen receptors (ER) and elicit agonist or antagonist responses depending on the target tissue and hormonal milieu. They are being evaluated primarily for conditions associated with aging, including hormone-responsive cancer, osteoporosis and cardiovascular disease. Several SERMs are marketed or are in clinical development, including triphenylethylenes (tamoxifen and its derivatives: toremifene, droloxifene and idoxifene), chromans (levormeloxifene), benzothiophenes (raloxifene, LY353381) and naphthalenes (CP336,156). Tamoxifen and toremifene, both used to treat advanced breast cancer, also have beneficial effects on bone mineral density and serum lipids in postmenopausal women. Tamoxifen was recently shown to decrease the risk of invasive breast cancer in women at high risk. Unfortunately, both drugs also have stimulatory effects on the endometrium. Raloxifene, used for prevention of postmenopausal osteoporosis and fragility fractures, also has favourable effects on bone mineral density, serum lipids and the incidence of invasive breast cancer in postmenopausal women but does not stimulate the endometrium. Like replacement estrogens, SERMs increase the risk of venous thromboembolism. SERMs offer post-menopausal women many of the advantages of estrogen replacement while mitigating some of the disadvantages, particularly the concern over breast cancer. Newer SERMs, exemplified by raloxifene, also eliminate the concerns over endometrial stimulation that were not addressed by first generation SERMs. The clinical success of SERMs has set the stage for a variety of drug therapies based on selective modulation of nuclear receptor activity.

Estrogen Antagonists↗

[Clinical results of selective estrogen receptor modulators (SERM)].

The SERMs (selective estrogen receptor modulators) are a new class of molecules that bind to the estrogen receptor, resulting in an estradiol agonist or antagonist response according to the target tissue. Raloxifene, a new SERM, has been shown to prevent postmenopausal bone loss, to reduce the risk of vertebral fractures in osteoporotic women, to decrease serum cholesterol and its LDL fraction, and to reduce significantly the risk of breat cancer. Raloxifene is available in France for the prevention of post-menopausal osteoporosis.

Bone and Bones↗

Inhibition of intimal hyperplasia using the selective estrogen receptor modulator raloxifene.

HYPOTHESIS: The selective estrogen receptor modulator raloxifene hydrochloride inhibits intimal hyperplasia. DESIGN: Controlled laboratory experiment. SETTING: Experimental animal model. INTERVENTION AND MAIN OUTCOME MEASURES: Forty-three senile female sheep were randomized to sham operation, ovariectomy, or ovariectomy followed by treatment with 17beta-estradiol or raloxifene. Six months after initial operation, we performed necropsy with histological assessment of the aortic bifurcation and bone mineral densitometry and assayed serum lipids. RESULTS: After 6 months, serum triglyceride and total and high-density lipoprotein cholesterol levels were similar among groups and within the reference range. Ovarian ablation alone resulted in intimal hyperplasia, which was attenuated with estradiol and raloxifene therapy. Furthermore, estradiol and raloxifene therapy reversed ovariectomy-induced decreases in bone mineral density measured using spine morphometry. CONCLUSIONS: Raloxifene attenuates ovariectomy-induced aortic intimal hyperplasia independent of serum lipid levels. These data suggest that raloxifene, in addition to its beneficial influence on bone density, has direct, beneficial cardiovascular effects.

Animals↗

Future use of selective estrogen receptor modulators and aromatase inhibitors.

Selective estrogen receptor modulators (SERMs) may act as estrogens or antiestrogens depending on the cell and tissue targets. The triphenylethylene SERMs are represented by tamoxifen and toremifene and a new agent with a novel carboxylic acid side chain (GW5638). Because of isomerization in the triphenylethylene molecule, "fixed ring" SERMs were introduced. The major one in development is the benzothiophene arzoxiphene (LY353381), which is now in Phase III clinical trial versus tamoxifen. A fourth group of SERMs is based on the estrogen molecule and comprises the so-called "pure" antiestrogen ICI 182,780 (fulvestrant, Faslodex) and a new oral analogue just entering trials, SR16234. The steroidal aromatase inhibitors [AIs (40H androstenedione 'and exemestane)] inactivate aromatase, whereas the triazole AIs (anastrozole and letrozole) inhibit the enzyme via the heme prosthetic group. Thus, there are two groups of AIs that show relative non-cross-resistance in advanced breast cancer and four groups of SERMs that also show a high degree of non-cross-resistance. With six different treatments and six or more clinical situations (prevention, neoadjuvant, adjuvant, and first- and second-line treatments for advanced disease) in which they may be used, the possible combinations of treatment are enormous. At present, we have few clinical pointers to optimal sequence of treatments. Now that most of the appropriate comparative trials have been performed, it may be the time to initiate novel approaches. These include alternating and sequential treatments, preferably with treatments changed before overt progression occurs.

Aromatase Inhibitors↗

Raloxifene: a selective estrogen receptor modulator.

Raloxifene is a selective estrogen receptor modulator that produces both estrogen-agonistic effects on bone and lipid metabolism and estrogen-antagonistic effects on uterine endometrium and breast tissue. Because of its tissue selectivity, raloxifene may have fewer side effects than are typically observed with estrogen therapy. The most common adverse effects of raloxifene are hot flushes and leg cramps. The drug is also associated with an increased risk of thromboembolic events. The beneficial estrogenic activities of raloxifene include a lowering of total and low-density lipoprotein cholesterol levels and an augmentation of bone mineral density. Raloxifene has been labeled by the U.S. Food and Drug Administration for the prevention of osteoporosis. However, its effects on fracture risk and its ability to protect against cardiovascular disease have yet to be determined. Studies are also being conducted to determine its impact on breast and endometrial cancer reduction.

Bone and Bones↗

Clinical use of selective estrogen receptor modulators.

The concept of selective estrogen receptor modulators (SERMs) is derived from the observation that tamoxifen, an effective adjuvant therapy of breast cancer that has an antiestrogenic effect on breast tissue, has estrogen-like effects on the skeleton and on plasma lipoproteins. Raloxifene is a SERM that has undergone extensive clinical investigation in the prevention and treatment of postmenopausal osteoporosis. It prevents bone loss at all skeletal sites, and in a large trial in osteoporotic women, the incidence of vertebral fractures was significantly decreased (relative risk 0.64) after up to 4 years of treatment with raloxifene 60 mg. The decrease of nonvertebral fractures did not reach the level of significance. Raloxifene decreased significantly the incidence of breast cancer (relative risk 0.28) and has no effect on the risk of endometrial cancer. SERMs are likely to play an important role in the management of postmenopausal women.

Bone Density↗

[Selective estrogen receptor modulators (SERMs) in the practice].

Selective estrogen receptor modulators (SERMs) represent a growing class of compounds that act as either estrogen receptor gonists or ntagonists in tissue-selective manner. SERMs with the appropriate selectivity profile offer the opportunity to dissociate the favorable bone and cardio-vascular effects of estrogen from its unfavorable stimulatory effects on the breast and uterus. The triphenylethylene drug tamoxifen proved to be invaluable to treat and protect against breast cancer and bone loss, probably reduces cardiovascular risk, but had side effects on uterus similar to natural estrogens. The tamoxifen derivate toremifene is also used to treat breast cancer, but has less effect on bone. The non-steroidal benzothiophene derivate, raloxifene, is the best SERM available thus far. It has the potential to prevent breast cancer (like tamoxifen), but has better profile in its actions on bone and cardiovascular system (produces a rapid reduction of serum cholesterol, decreases fibrinogen and lipoprotein, improves the vascular epithelial function, attenuates vascular intimal thickening, etc.). It does not increase the incidence of endometrial cancer. Compounds of this class are the first step in developing the perfect hormone replacement and other multitargeted therapy. This review summarizes the recent important knowledge about SERMs.

Breast Neoplasms↗

Cardiovascular effects of droloxifene, a new selective estrogen receptor modulator, in healthy postmenopausal women.

Selective estrogen receptor modulators, like tamoxifen and related compounds, have mixed estrogen agonistic/antagonistic effects. Tamoxifen may confer significant cardiovascular benefits without the estrogen-associated risks of endometrial and breast cancer. Droloxifene, a structural analogue of tamoxifen, has estrogen agonistic effects on bone and antagonistic effects on endometrial and breast tissue. Its cardiovascular effects in women are unknown. We enrolled 24 healthy postmenopausal women in a randomized, double-blind, 2-period crossover trial comparing the effects of droloxifene (60 mg/d) with conjugated estrogen (0.625 mg/d). Plasma lipids, coagulation and fibrinolytic factors, and brachial flow-mediated vasodilator responses were measured at the beginning and end of each treatment period. Droloxifene and estrogen resulted in 16.6% and 12.0% reductions, respectively, in low density lipoprotein cholesterol (P<0.001) and 13.2% and 9.5% reductions, respectively, in lipoprotein(a) (P<0.05). In contrast, estrogen, but not droloxifene, increased high density lipoprotein (18.5%, P<0.001). Droloxifene also reduced fibrinogen by 17.8% versus a 7.3% reduction with estrogen (P=0.004) but produced no estrogen-like changes in plasminogen, plasminogen activator inhibitor-1, or tissue plasminogen activator. Droloxifene and estrogen produced 36.4% and 27.3% increases, respectively, in flow-mediated vasodilation (percent change from baseline, P<0.05 for both). Droloxifene has estrogen agonistic properties regarding low density lipoprotein and lipoprotein(a) metabolism, certain coagulation factors, and endothelium-dependent vasodilation but, unlike estrogen, has no effect on high density lipoprotein/triglyceride metabolism and the fibrinolytic cascade. It remains unknown whether droloxifene can confer a true cardiovascular benefit.

Aged↗