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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↗

[Next generation selective estrogen receptor modulators].

Selective estrogen receptor modulators (SERMs) have the potential to provide the skeletal benefits of estrogen without the increased risk of uterine and breast cancer. Raloxifene, second generation SERM has been approved for the prevention and treatment of osteoporosis. Lasofoxifene (LAS) and bazedoxifene (BZA, TSE-424), novel SERMs, act as a tissue selective estrogen antagonist or agonist. These novel SERMs inhibited bone turnover and prevented bone loss caused estrogen deficiency. Furthermore, these SERMs did not affect the uterine endometrial thickness and reduced serum cholesterol. These date suggest that LAS and TSE-424 are novel potential therapy for the prevention of osteoporosis in postmenopausal women.

Animals↗

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↗

Pharmacokinetics of selective estrogen receptor modulators.

Selective estrogen receptor modulators (SERMs) are a class of compounds used to treat and prevent breast cancer and osteoporosis. SERMs currently approved for use in patients include tamoxifen, toremifene and raloxifene. These compounds are well tolerated in patients, and the most common adverse effects experienced in patients undergoing SERM therapy include vasomotor symptoms such as hot flashes and vaginal discharge. New SERMs currently under development for use in the treatment and prevention of osteoporosis and breast cancer include ospemifene, a derivative of toremifene, and arzoxifene, a compound very similar in structure to raloxifene. SERMs are administered orally at doses ranging from 20 to 60 mg/day. Tamoxifen and toremifene have a bioavailability of approximately 100%, whereas that of raloxifene is only 2%. SERMs are very highly bound to plasma proteins (>95%). Tamoxifen and toremifene are metabolised by the cytochrome p450 enzyme system, and raloxifene is metabolised by glucuronide conjugation. The terminal elimination half-lives of these drugs range from 27.7 hours to 7 days. The pharmacokinetics of these compounds are affected in hepatically impaired patients, but not in renally impaired patients. SERMs have several potential drug interactions with other agents, such as warfarin, rifampicin (rifampin), cholestyramine and aromatase inhibitors.

Age Factors↗

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↗

[The future of SERM (selective estrogen receptor modulator)].

Selective estrogen receptor modulator (SERM) is a kind of drug that has agonistic and antagonistic effects of estrogen in different tissues. MORE study has shown that raloxyfene reduces osteoporotic vertebral fractures and serum cholesterol levels in postmenopausal women, while it does not stimulate the endometrium and decreases the breast cancer occurrence. There are more to be investigated like developing newer SERMs, a combination therapy with estrogen or the elucidation of mechanisms of estrogen effects.

English Abstract↗

Estrogen to antiestrogen with a single methylene group resulting in an unusual steroidal selective estrogen receptor modulator.

Selective estrogen receptor (ER) modulators (SERMs) are important therapeutic agents for breast cancer prevention and treatment. We have synthesized two analogs, E11-2,1 [methyl-(3,17beta-dihydroxyestra-1,3,5(10)-triene-11beta-yl)acetate] and E11-2,2 [ethyl-(3,17beta-dihydroxyestra-1,3,5(10)-triene-11beta-yl)acetate], the methyl and ethyl esters of an estradiol analog, substituted in the B ring at C-11beta with a carboxymethyl group. The shorter methyl ester, E11-2,1, has high ER affinity and high estrogenic potency in the Ishikawa estrogen cell bioassay, whereas the longer ethyl ester, E11-2,2, has even higher ER affinity, but little or no estrogenic activity. We found that this minor change of one methylene group transforms a potent estrogenic agonist into an antagonist in vitro with either ER alpha or beta. In the rat, E11-2,2 acts as a SERM in the uterus, where it inhibits estradiol-induced proliferation, and as an estrogen agonist in the liver and skeleton, where it decreases plasma cholesterol and increases bone growth. The characteristic feature of antiestrogens, including SERMs, is a long and polar side-chain that prevents agonist-induced conformation of helix 12 of ER. E11-2,2 with its short, nonpolar side-chain, lacks this critical structure, presenting the possibility that it might act through a unique mechanism.

Animals↗

The use of selective estrogen receptor modulators and selective estrogen receptor down-regulators in breast cancer.

Tamoxifen is one of the most effective treatments for breast cancer through its ability to antagonize estrogen-dependent growth by binding estrogen receptors (ERs) and inhibiting proliferation of breast epithelial cells. However, tamoxifen has estrogenic agonist effects in other tissues such as bone and endometrium due to liganded ER activating target genes in these different types of cell. Several novel anti-estrogen compounds have been developed which have a reduced agonist profile on breast and gynaecological tissues. These compounds offer the potential for enhanced efficacy and reduced toxicity compared with tamoxifen. In advanced breast cancer clinical data exist for two groups of agents: the selective estrogen receptor modulators (SERMs), further divided into "tamoxifen-like" (e.g. toremifene, droloxifene and idoxifene) and "fixed ring" compounds (e.g. raloxifene, arzoxifene and EM-800), and the selective estrogen receptor down-regulators (SERDs; e.g. fulvestrant (ICI 182780), SR 16234 and ZK 191703) also termed "pure anti-estrogens". In phase II trials in tamoxifen-resistant metastatic breast cancer the SERMs show low objective response rates (range 0-15%), suggesting cross resistance with tamoxifen. Randomized phase III trials for toremifene and idoxifene in over 1500 patients showed no significant difference compared with tamoxifen. Fewer clinical data exist for the "fixed ring" SERMs and it remains unclear whether any clinical advantage exists for the "fixed ring" SERMs over tamoxifen as first-line therapy. The main advantage for SERMs such as tamoxifen and raloxifene probably remains in early-stage disease (adjuvant therapy or prevention). Fulvestrant and the other SERDs have a high affinity for the estrogen receptor (ER) compared to tamoxifen, but none of its agonist activities. Of the SERDs, only fulvestrant has entered the clinic and this new agent is showing promising clinical activity in the treatment of advanced breast cancer. Recently published phase III studies have shown fulvestrant to be at least as effective as the third-generation aromatase inhibitor anastrozole in patients whose disease has relapsed or progressed on prior endocrine therapy. Surprisingly, however, in a phase III trial versus tamoxifen for the first-line therapy of advanced breast cancer fulvestrant did not attain the requirements for equivalence to tamoxifen, and in terms of time-to-treatment failure was inferior (5.9 versus 7.8 months for fulvestrant and tamoxifen, respectively; P=0.029). Future clinical studies will evaluate fulvestrant in the neoadjuvant setting together with its optimal sequencing in relation to tamoxifen and other endocrine therapies in advanced disease.

Antineoplastic Agents, Hormonal↗

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↗

Estrogens, selective estrogen receptor modulators, and a selective estrogen receptor down-regulator inhibit endothelial production of tissue factor pathway inhibitor 1.

BACKGROUND: Hormone therapy, oral contraceptives, and tamoxifen increase the risk of thrombotic disease. These compounds also reduce plasma content of tissue factor pathway inhibitor-1 (TFPI), which is the physiological inhibitor of the tissue factor pathway of coagulation. The current aim was to study if estrogens and estrogen receptor (ER) modulators may inhibit TFPI production in cultured endothelial cells and, if so, identify possible mechanisms involved. METHODS: Human endothelial cell cultures were treated with 17beta-estradiol (E2), 17alpha-ethinylestradiol (EE2), tamoxifen, raloxifene, or fulvestrant. Protein levels of TFPI in cell media and cell lysates were measured by an enzyme-linked immunosorbent assay, and TFPI mRNA levels were assessed by quantitative PCR. Expression of ERalpha was analysed by immunostaining. RESULTS: All compounds (each in a concentration of 10 nM) reduced TFPI in cell medium, by 34% (E2), 21% (EE2), 16% (tamoxifen), and 28% (raloxifene), respectively, with identical inhibitory effects on cellular TFPI levels. Expression of TFPI mRNA was principally unchanged. Treatment with fulvestrant, which was also associated with down-regulation of secreted TFPI (9% with 10 nM and 26% with 1000 nM), abolished the TFPI-inhibiting effect of raloxifene, but not of the other compounds. Notably, the combination of 1000 nM fulvestrant and 10 nM raloxifene increased TFPI secretion, and, conversely, 10 nM of either tamoxifen or raloxifene seemed to partly (tamoxifen) or fully (raloxifene) counteract the inhibitory effect of 1000 nM fulvestrant. The cells did not express the regular nuclear 66 kDa ERalpha, but instead a 45 kDa ERalpha, which was not regulated by estrogens or ER modulators. CONCLUSION: E2, EE2, tamoxifen, raloxifene, and fulvestrant inhibited endothelial production of TFPI by a mechanism apparently independent of TFPI transcription.

Cells, Cultured↗

[Selective estrogen receptor modulators (SERMs)].

Selective estrogen receptor modulators (SERMs) bind to estrogen receptor (ER) and develop tissue-selective actions as estrogen agonists or antagonists. As such, SERMs have been developed to exert estrogen-like beneficial effects against some disorders including osteoporosis, while reducing estrogen-related risks, including breast cancer. Prevention of vertebral fractures by a SERM, raloxifene (RLX), in osteoporotic postmenopausal women has been well established. RLX does not increase or decrease cardiovascular events, overall mortality, cardiovascular mortality or the overall number of strokes, but there appears to be a small increase in stroke mortality. Both RLX and tamoxifen similarly reduce the risk of ER-positive invasive breast cancer. At the same time, RLX treatment is associated with 36% fewer uterine cancer incidence and 29% less thromboembolic events. Keeping these results in mind, it is our responsibility to critically evaluate and decide timing and length of treatment, as well as subjects with benefits or risks for the treatment of osteoporosis by SERMs.

Breast Neoplasms↗

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 modulator].

SERMs (selective estrogen-receptor modulators) selectively act on various target tissues under estrogen influence as estrogen-agonists or antagonists. Following publication of an interim report from the Women's Health Initiative (WHI) randomized trial, SERMs have drawn considerable attention as agents of interest, in that they allow almost all beneficial effects of estrogen to be retained while at the same time avoiding the harmful side effects associated with HRT. In this regard, raloxifene is reported to act on bone as an estrogen-agonist as does HRT thereby contributing to a significant decrease in the incidence of osteoporotic fractures, while, in contrast, acting on the breast as an estrogen-antagonist unlike HRT to reduce the incidence of breast cancer, and its further role is expected in the treatment of coronary heart disease. Thus, SERMs are emerging as a class of versatile agents with great potential, and their indications are expected to widen with further research evidence.

Female↗

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↗

Chemical modification modulates estrogenic activity, oxidative reactivity, and metabolic stability in 4'F-DMA, a new benzothiophene selective estrogen receptor modulator.

The benzothiophene selective estrogen receptor modulators (SERMs), raloxifene and arzoxifene, in the clinic or clinical trials for treatment of breast cancer and postmenopausal symptoms, are highly susceptible to oxidative metabolism and formation of electrophilic metabolites. 4'F-DMA, fluoro-substituted desmethyl arzoxifene (DMA), showed attenuated oxidation to quinoids in incubation with rat hepatocytes as well as in rat and human liver microsomes. Incubations of 4'F-DMA with hepatocytes yielded only one glucuronide conjugate and no GSH conjugates, whereas DMA underwent greater metabolism giving two glucuronide conjugates, one sulfate conjugate, and two GSH conjugates. Phase I and phase II metabolism were further evaluated in human small intestine microsomes and in human intestinal Caco-2 cells. In comparison to DMA, 4'F-DMA formed significantly less glucuronide and sulfate conjugates. The formation of quinoids was further explored in hepatocytes in which DMA was observed to give concentration- and time-dependent depletion of GSH accompanied by damage to DNA, which showed inverse dependence on GSH; in contrast, GSH depletion and DNA damage were almost completely abrogated in incubations with 4'F-DMA. 4'F-DMA shows ligand binding affinity to estrogen receptor (ER)alpha and ERbeta with similarity to both raloxifene and to DMA. ER-mediated biological activity was measured with the ERE-luciferase reporter system in transfected MCF-7 cells and Ishikawa cells, and in MCF-7 cells, proliferation was measured. In all systems, 4'F-DMA exhibited anitestrogenic activity of comparable potency to raloxifene but did not manifest estrogenic properties, mirroring previous results on inhibition of estradiol-mediated induction of alkaline phosphatase activity in Ishikawa cells. These results suggest that 4'F-DMA might be an improved benzothiophene SERM with similar antiestrogenic activity to raloxifene but improved metabolic stability and attenuated toxicity, showing that simple chemical modification can abrogate oxidative bioactivation to potentially toxic metabolites without loss of activity.

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↗