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Estrogen receptor alpha (ERα) plays a critical role in breast cancer (BC) progression, with endocrine therapy being a key treatment for ERα + BC. However, resistance often arises due to somatic mutations in the ERα ligand-binding domain (LBD). Lasofoxifene, a third-generation selective estrogen receptor modulator, has shown promise against Y537S and D538G mutations. However, the emergence of a novel F404 mutation in patients with pre-existing LBD mutations raises concerns about its impact on lasofoxifene efficacy. This study investigates the impact of the dual Y537S and F404V mutations on lasofoxifene's efficacy. Using molecular dynamics simulations and molecular mechanics/Poisson-Boltzmann surface area (MM-PBSA) free energy calculations, we found that the dual mutation reduces lasofoxifene binding affinity and binding free energy, disrupts crucial protein-ligand interactions, and induces significant conformational changes in the ligand-binding pocket. These alterations are likely due to the loss of the pi-pi stacking interaction in the F404V mutation. These findings suggest a potential reduction in lasofoxifene efficacy due to the dual mutation. Further experimental validation is required to confirm these results and fully understand the impact of dual mutations on lasofoxifene's effectiveness in ERα + metastatic BC. [ABSTRACT FROM AUTHOR]

Abstract Background Breast cancers treated with aromatase inhibitors (AIs) can develop AI resistance, which is often driven by estrogen receptor-alpha (ERα/ESR1) activating mutations, as well as by ER-independent signaling pathways. The breast ER antagonist lasofoxifene, alone or combined with palbociclib, elicited antitumor activities in a xenograft model of ER + metastatic breast cancer (mBC) harboring ESR1 mutations. The current study investigated the activity of LAS in a letrozole-resistant breast tumor model that does not have ESR1 mutations. Methods Letrozole-resistant, MCF7 LTLT cells tagged with luciferase-GFP were injected into the mammary duct inguinal glands of NSG mice (MIND model; 6 mice/group). Mice were randomized to vehicle, lasofoxifene ± palbociclib, fulvestrant ± palbociclib, or palbociclib alone 2–3 weeks after cell injections. Tumor growth and metastases were monitored with in vivo and ex vivo luminescence imaging, terminal tumor weight measurements, and histological analysis. The experiment was repeated with the same design and 8–9 mice in each treatment group. Results Western blot analysis showed that the MCF7 LTLT cells had lower ERα and higher HER2 expressions compared with normal MCF7 cells. Lasofoxifene ± palbociclib, but not fulvestrant, significantly reduced primary tumor growth versus vehicle as assessed by in vivo imaging of tumors at study ends. Percent tumor area in excised mammary glands was significantly lower for lasofoxifene plus palbociclib versus vehicle. Ki67 staining showed decreased overall tumor cell proliferation with lasofoxifene ± palbociclib. The lasofoxifene + palbociclib combination was also associated with significantly fewer bone metastases compared with vehicle. Similar results were observed in the repeat experiment. Conclusions In a mouse model of letrozole-resistant breast cancer with no ESR1 mutations, reduced levels of ERα, and overexpression of HER2, lasofoxifene alone or combined with palbociclib inhibited primary tumor growth more effectively than fulvestrant. Lasofoxifene plus palbociclib also reduced bone metastases. These results suggest that lasofoxifene alone or combined with a CDK4/6 inhibitor may offer benefits to patients who have ER-low and HER2-positive, AI-resistant breast cancer, independent of ESR1 mutations.

Background: Breast cancers treated with aromatase inhibitors (AIs) can develop AI resistance, which is often driven by estrogen receptor-alpha (ERα/ESR1) activating mutations, as well as by ER-independent signaling pathways. The breast ER antagonist lasofoxifene, alone or combined with palbociclib, elicited antitumor activities in a xenograft model of ER + metastatic breast cancer (mBC) harboring ESR1 mutations. The current study investigated the activity of LAS in a letrozole-resistant breast tumor model that does not have ESR1 mutations. Methods: Letrozole-resistant, MCF7 LTLT cells tagged with luciferase-GFP were injected into the mammary duct inguinal glands of NSG mice (MIND model; 6 mice/group). Mice were randomized to vehicle, lasofoxifene ± palbociclib, fulvestrant ± palbociclib, or palbociclib alone 2–3 weeks after cell injections. Tumor growth and metastases were monitored with in vivo and ex vivo luminescence imaging, terminal tumor weight measurements, and histological analysis. The experiment was repeated with the same design and 8–9 mice in each treatment group. Results: Western blot analysis showed that the MCF7 LTLT cells had lower ERα and higher HER2 expressions compared with normal MCF7 cells. Lasofoxifene ± palbociclib, but not fulvestrant, significantly reduced primary tumor growth versus vehicle as assessed by in vivo imaging of tumors at study ends. Percent tumor area in excised mammary glands was significantly lower for lasofoxifene plus palbociclib versus vehicle. Ki67 staining showed decreased overall tumor cell proliferation with lasofoxifene ± palbociclib. The lasofoxifene + palbociclib combination was also associated with significantly fewer bone metastases compared with vehicle. Similar results were observed in the repeat experiment. Conclusions: In a mouse model of letrozole-resistant breast cancer with no ESR1 mutations, reduced levels of ERα, and overexpression of HER2, lasofoxifene alone or combined with palbociclib inhibited primary tumor growth more effectively than fulvestrant. Lasofoxifene plus palbociclib also reduced bone metastases. These results suggest that lasofoxifene alone or combined with a CDK4/6 inhibitor may offer benefits to patients who have ER-low and HER2-positive, AI-resistant breast cancer, independent of ESR1 mutations. [ABSTRACT FROM AUTHOR]

Acquired estrogen receptor alpha (ER/ ESR1) mutations commonly cause endocrine resistance in ER+ metastatic breast cancer (mBC). Lasofoxifene, a novel selective ER modulator, stabilizes an antagonist conformation of wild-type and ESR1 -mutated ER-ligand binding domains, and has antitumor activity in ESR1 -mutated xenografts. In this open-label, randomized, phase II, multicenter, ELAINE 1 study (NCT03781063), we randomized women with ESR1 -mutated, ER+/human epidermal growth factor receptor 2 negative (HER2−) mBC that had progressed on an aromatase inhibitor (AI) plus a cyclin-dependent kinase 4/6 inhibitor (CDK4/6i) to oral lasofoxifene 5 mg daily or IM fulvestrant 500 mg (days 1, 15, and 29, and then every 4 weeks) until disease progression/toxicity. The primary endpoint was progression-free survival (PFS); secondary endpoints were safety/tolerability. A total of 103 patients received lasofoxifene (n = 52) or fulvestrant (n = 51). The most current efficacy analysis showed that lasofoxifene did not significantly prolong median PFS compared with fulvestrant: 24.2 weeks (∼5.6 months) versus 16.2 weeks (∼3.7 months; P = 0.138); hazard ratio 0.699 (95% confidence interval 0.434-1.125). However, PFS and other clinical endpoints numerically favored lasofoxifene: clinical benefit rate (36.5% versus 21.6%; P = 0.117), objective response rate [13.2% (including a complete response in one lasofoxifene-treated patient) versus 2.9%; P = 0.124], and 6-month (53.4% versus 37.9%) and 12-month (30.7% versus 14.1%) PFS rates. Most common treatment-emergent adverse events with lasofoxifene were nausea, fatigue, arthralgia, and hot flushes. One death occurred in the fulvestrant arm. Circulating tumor DNA ESR1 mutant allele fraction (MAF) decreased from baseline to week 8 in 82.9% of evaluable lasofoxifene-treated versus 61.5% of fulvestrant-treated patients. Lasofoxifene demonstrated encouraging antitumor activity versus fulvestrant and was well tolerated in patients with ESR1 -mutated, endocrine-resistant mBC following progression on AI plus CDK4/6i. Consistent with target engagement, lasofoxifene reduced ESR1 MAF, and to a greater extent than fulvestrant. Lasofoxifene may be a promising targeted treatment for patients with ESR1 -mutated mBC and warrants further investigation. • Lasofoxifene showed antitumor activity in patients with ESR1 -mutated mBC that progressed on an AI plus a CDK4/6i. • Lasofoxifene numerically improved PFS (5.6 versus 3.7 months) and clinical benefit rate (37% versus 22%) versus fulvestrant. • Lasofoxifene was well-tolerated with no unexpected safety signals. • Lasofoxifene reduced ESR1 MAF, including Y537S MAF, in more patients than fulvestrant, exhibiting target engagement. • Lasofoxifene may be a promising endocrine therapy backbone for ESR1 -mutated mBC in a post-CDK4/6i setting. [ABSTRACT FROM AUTHOR]

Acquired ESR1 mutations in estrogen receptor-positive (ER+) metastatic breast cancer (mBC) drive treatment resistance and tumor progression; new treatment strategies are needed. Lasofoxifene, a next-generation, oral, endocrine therapy and tissue-specific ER antagonist, provided preclinical antitumor activity, alone or combined with a cyclin-dependent kinase 4/6 inhibitor (CDK4/6i) in ESR1 -mutated mBC. In the open-label, phase II, ELAINE 2 trial (NCT04432454), women with ESR1 -mutated, ER+/human epidermal growth factor receptor 2-negative (HER2−) mBC who progressed on prior therapies (including CDK4/6i) received lasofoxifene 5 mg/day and abemaciclib 150 mg b.i.d until disease progression/toxicity. The primary endpoint was safety/tolerability. Secondary endpoints included progression-free survival (PFS), clinical benefit rate (CBR), and objective response rate (ORR). Twenty-nine women (median age 60 years) participated; all but one were previously treated with a CDK4/6i (median duration 2 years). The lasofoxifene–abemaciclib combination was well tolerated with primarily grade 1/2 treatment-emergent adverse events (TEAEs), most commonly diarrhea, nausea, fatigue, and vomiting. One patient (with no prior CDK4/6i) discontinued treatment due to grade 2 diarrhea. No deaths occurred during the study. Median PFS was 56.0 weeks [95% confidence interval (CI) 31.9 weeks-not estimable; ∼13 months]; PFS rates at 6, 12, and 18 months were 76.1%, 56.1%, and 38.8%, respectively. CBR at 24 weeks was 65.5% (95% CI 47.3% to 80.1%). In 18 patients with measurable lesions, ORR was 55.6% (95% CI 33.7% to 75.4%). ESR1 -mutant circulating tumor DNA (ctDNA) allele fraction decreased from baseline to week 4 in 21/26 (80.8%) patients. Lasofoxifene plus abemaciclib had an acceptable safety profile, was well tolerated, and exhibited meaningful antitumor activity in women with ESR1 -mutated, ER+/HER2− mBC after disease progression on prior CDK4/6i. Observed decreases in ESR1 -mutant ctDNA with lasofoxifene concordant with clinical response suggest target engagement. If the ELAINE 2 findings are confirmed in the initiated, phase III, ELAINE 3 trial, these data could be practice-changing and help address a critical unmet need. • Lasofoxifene–abemaciclib led to meaningful PFS (∼13 months), ORR (56%), and CBR (66%) in ESR1 -mutant mBC. • Lasofoxifene–abemaciclib was active for ESR1 -mutated breast tumors that progressed with endocrine therapy and CDK4/6is. • Lasofoxifene–abemaciclib was well tolerated with a manageable safety profile. • ESR1 mutant allele fractions were reduced/undetected with lasofoxifene–abemaciclib, consistent with target engagement. • Lasofoxifene–abemaciclib may become a promising therapy for ESR1 -mutant mBC after CDK4/6i treatment. [ABSTRACT FROM AUTHOR]

Abstract Background Endocrine therapy remains the mainstay of treatment for estrogen receptor-positive (ER+) breast cancer. Constitutively active mutations in the ligand binding domain of ERα render tumors resistant to endocrine agents. Breast cancers with the two most common ERα mutations, Y537S and D538G, have low sensitivity to fulvestrant inhibition, a typical second-line endocrine therapy. Lasofoxifene is a selective estrogen receptor modulator with benefits on bone health and breast cancer prevention potential. This study investigated the anti-tumor activity of lasofoxifene in breast cancer xenografts expressing Y537S and D538G ERα mutants. The combination of lasofoxifene with palbociclib, a CDK4/6 inhibitor, was also evaluated. Methods Luciferase-GFP tagged MCF7 cells bearing wild-type, Y537S, or D538G ERα were injected into the mammary ducts of NSG mice (MIND model), which were subsequently treated with lasofoxifene or fulvestrant as single agents or in combination with palbociclib. Tumor growth and metastasis were monitored with in vivo and ex vivo luminescence imaging, terminal tumor weight measurements, and histological analysis. Results As a monotherapy, lasofoxifene was more effective than fulvestrant at inhibiting primary tumor growth and reducing metastases. Adding palbociclib improved the effectiveness of both lasofoxifene and fulvestrant for tumor suppression and metastasis prevention at four distal sites (lung, liver, bone, and brain), with the combination of lasofoxifene/palbociclib being generally more potent than that of fulvestrant/palbociclib. X-ray crystallography of the ERα ligand binding domain (LBD) shows that lasofoxifene stabilizes an antagonist conformation of both wild-type and Y537S LBD. The ability of lasofoxifene to promote an antagonist conformation of Y537S, combined with its long half-life and bioavailability, likely contributes to the observed potent inhibition of primary tumor growth and metastasis of MCF7 Y537S cells. Conclusions We report for the first time the anti-tumor activity of lasofoxifene in mouse models of endocrine therapy-resistant breast cancer. The results demonstrate the potential of using lasofoxifene as an effective therapy for women with advanced or metastatic ER+ breast cancers expressing the most common constitutively active ERα mutations.

The coronavirus disease-2019 (COVID-19) was first recognized in Wuhan, China, and quickly spread worldwide. Between all proposed research guidelines, inhibition of the main protease (Mpro) protein of the virus will be one of the main strategies for COVID-19 treatment. The present work was aimed to perform a computational study on FDA-approved drugs, similar to piperine scaffold, to find possible Mpro inhibitors. Firstly, virtual screening studies were performed on a library of FDA-approved drugs (43 medicinal compounds, similar to piperine scaffold). Among imported 43 drugs to virtual screening, 34 compounds were extracted. Four top-ranked drugs in terms of the highest interactions and the lowest binding energy were selected for the IFD study. Among these selections, lasofoxifene showed the lowest IFD score (-691.743 kcal mol-1). The stability of lasofoxifene in the COVID-19 Mpro protein active site was confirmed with 100 ns MD simulation. Lasofoxifene binding free energy was obtained -107.09 and -173.97 kcal mol-1, using Prime MM-GBSA and g_mmpbsa methods, respectively. The identified lasofoxifene by the presented computational approaches could be a suitable lead for inhibiting Mpro protein and COVID-19 treatment. [ABSTRACT FROM AUTHOR]

Selective estrogen receptor modulators (SERMs) or estrogen agonists/antagonists have shown promise in osteoporosis in that they have the potential to reduce the risk of fracture, and also reduce the risk of breast cancer. SERMs maybe classified according to their core structure, which is typically a variation of the 17 beta-estradiol template and subclassified according to the side chain at the helix 12 affector region. The best known are the triphenylethylenes such as tamoxifen, used in the management of breast cancer. However, the clinical application of this class of SERMs has been limited due to endometrial stimulation. A second class is the benzothiophenes such as raloxifene and arzoxifene, which have skeletal benefit with little, if any, uterine stimulation. Indole-based SERMs such as bazedoxifene have a 2-phenyl ring system that serves as a core binding unit. Other classes include benzopyrans and naphthalenes (eg, lasofoxifene). In this review article, I will discuss raloxifene and three new SERMs—arzoxifene, bazedoxifene, and lasofoxifene—that have been recently studied. I will discuss their effect on bone, breast, and the cardiovascular system, as well as on safety.

Selective estrogen receptor modulators (SERMs) represent a class of drugs that act as agonist or antagonist for estrogen receptor in a tissue-specific manner. The SERMs drugs are initially used for the prevention and treatment of osteoporosis in postmenopausal women. Bone health in prostate cancer patients has become a significant concern, whereby patients undergo androgen deprivation therapy is often associated with deleterious effects on bone. Previous preclinical and epidemiological findings showed that estrogens play a dominant role in improving bone health as compared to testosterone in men. Therefore, this evidence-based review aims to assess the available evidence derived from animal and human studies on the effects of SERMs on the male skeletal system. The effects of SERMs on bone mineral density (BMD)/content (BMC), bone histomorphometry, bone turnover, bone strength and fracture risk have been summarized in this review. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Estrogen typically inhibits Runx2 in osteoblast progenitors. • Estrogen does not inhibit Runx2 at particular genes and concentrations. • Bimodal effect of increasing estrogen concentrations on osteoblast differentiation. • SERMs poorly mimic the bimodal effect of estrogen in pre-osteoblasts. • SERMs closely mimic estrogen in pre-osteoclasts. Abstract Estrogens attenuate bone turnover by inhibiting both osteoclasts and osteoblasts, in part through antagonizing Runx2. Apparently conflicting, stimulatory effects in osteoblast lineage cells, however, sway the balance between bone resorption and bone formation in favor of the latter. Consistent with this dualism, 17ß-estradiol (E2) both stimulates and inhibits Runx2 in a locus-specific manner, and here we provide evidence for such locus-specific regulation of Runx2 by E2 in vivo. We also demonstrate dual, negative and positive, regulation of Runx2-driven alkaline phosphatase (ALP) activity by increasing E2 concentrations in ST2 osteoblast progenitor cells. We further compared the effects of E2 to those of the Selective Estrogen Receptor Modulators (SERMs) raloxifene (ral) and lasofoxifene (las) and the phytoestrogen puerarin. We found that E2 at the physiological concentrations of 0.1–1 nM, as well as ral and las, but not puerarin, antagonize Runx2-driven ALP activity. At ≥10 nM, E2 and puerarin, but not ral or las, stimulate ALP relative to the activity measured at 0.1–1 nM. Contrasting the difference between E2 and SERMs in ST2 cells, they all shared a similar dose-response profile when inhibiting pre-osteoclast proliferation. That ral and las poorly mimic the locus- and concentration-dependent effects of E2 in mesenchymal progenitor cells may help explain their limited clinical efficacy. [ABSTRACT FROM AUTHOR]

There is a need for the development of new drugs to prevent osteoporosis-related fractures. Fractures are projected to increase and the present drugs have modest efficacy, significant side-effects and poor compliance. To illustrate the difficulties in the development of new drugs, the author reviews the fate of several drugs that have failed to gain regulatory approval. These drugs include arzoxifene, lasofoxifene, MK-5442, roncalceret and odanacatib. Romosozumab and abaloparatide are the only new drugs presently in phase-3 development. It is anticipated that ongoing studies of the mechanisms and signaling pathways involved in the regulation of bone remodeling will open up new opportunities for targeted pharmacological interventions to increase bone strength. However, the perfect drug is still a long way off and will face many obstacles before approval. [ABSTRACT FROM PUBLISHER]

A Lewis acid-mediated three-component coupling reaction was successfully applied for the synthesis of lasofoxifene (1), nafoxidine (2), and their positional isomers, inv-lasofoxifene (3) and inv-nafoxidine (4). In the presence of HfCl4, the desired one-pot coupling reaction among 4-pivaloyloxybenzaldehyde (5), cinnamyltrimethylsilane (6), and anisole proceeded to afford the corresponding 3,4,4-triaryl-1-butene 7 in high yield. The iodocarbocyclization of the coupling product and the successive elimination of hydrogen iodide forming the olefin part, followed by the migration of the double-bond afforded the common synthetic intermediate of lasofoxifene (1) and nafoxidine (2) via a very concise procedure. Additionally, the syntheses of their positional isomers inv-lasofoxifene (3) and inv-nafoxidine (4) were also achieved through very convenient protocols.

Albright was the first of many to show that loss of bone mass due to estrogen deficiency is an important part of the pathogenesis of postmenopausal osteoporosis. This led to the use of estrogen therapy which was shown to prevent bone loss at menopause and to reduce the risk of important fragility fractures. Selective estrogen receptor modulators (SERMs), with salutary estrogen-like skeletal effects and with protection from breast cancer, have important roles in the management of young postmenopausal women. New members of the SERM family may approach the effectiveness of estrogen in preventing bone loss and reducing fracture risk. When combined with estrogen, new SERMs prevent endometrial hyperplasia, and that combination reduces menopausal symptoms and prevents bone loss. Drugs that reduce bone turnover or stimulate bone formation by non-estrogen pathways have also been developed to treat osteoporosis. Emerging therapies, with unique mechanisms of action, may provide improved efficacy in treating women who already have osteoporosis. [ABSTRACT FROM PUBLISHER]

A novel brief process for the synthesis of nafoxidene has been developed. The epoxidation of 6-methoxy-1-{4-[2-(pyrrolin-1-yl)ethoxy)]phenyl}-3,4-dihydronaphthalene by m-CPBA directly gave the ketone 6-methoxy-1-[4-(2-(pyrrolidin-1-yl)ethoxy)phenyl]-3,4-dihydronaphthalen-2(1H)-one, which was subject to phenyl magnesium bromide/cerium chloride and subsequently treated with an acid to yield nafoxidene. In addition, the preparation of the starting naphthalene was also optimized by replacing the aromatic lithium at low temperature with its Grignard reagent at refluxing THF. This mild process, without the use of toxic or noble metals, was more cost-efficient and easily worked up. [ABSTRACT FROM AUTHOR]

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Highlights: [•] CB2 was discovered to be a novel target for bazedoxifene and lasofoxifene. [•] Bazdoxifene and lasofoxifene behaved as novel CB2 inverse agonists. [•] Our discovery provides insights into repurposing bazedoxifene and lasofoxifene. [•] Our data suggests new mechanisms of actions for bazedoxifene and lasofoxifene. [ABSTRACT FROM AUTHOR]

Selective estrogen receptor modulators (SERMs), which exhibit estrogen receptor agonist or antagonist activity based on the target tissue, have evolved through multiple generations for the prevention and/or treatment of postmenopausal osteoporosis. An ideal SERM would protect bone without stimulating the breast or endometrium. Raloxifene, lasofoxifene, and bazedoxifene have demonstrated unique preclinical profiles. Raloxifene, lasofoxifene, and bazedoxifene have shown significant reduction in the risk of vertebral fracture and improvement in bone mineral density versus placebo in postmenopausal women with osteoporosis. Raloxifene has been shown to reduce the risk of non-vertebral fractures in women with severe prevalent fractures at baseline. Lasofoxifene 0.5 mg, but not lasofoxifene 0.25 mg, has shown reduction in the incidence of non-vertebral fractures. Bazedoxifene 20 mg has been associated with a significant reduction in the risk of non-vertebral fracture versus placebo and raloxifene 60 mg in women at higher baseline fracture risk. Neither raloxifene, lasofoxifene, nor bazedoxifene has shown an increase in the incidence of endometrial hyperplasia or carcinoma. All SERMs have been associated with increased venous thromboembolic events and hot flushes. SERMs are effective alternatives for women who cannot tolerate or are unwilling to take bisphosphonates and may be appropriate for women at higher risk of fracture, particularly younger women who expect to remain on therapy for many years and are concerned about the long-term safety of bisphosphonates. [ABSTRACT FROM AUTHOR]

Abstract: 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. [Copyright &y& Elsevier]

Abstract: Osteoporosis and the resulting fractures are major public health issues as the world population is ageing. Various therapies such as bisphosphonates, strontium ranelate and more recently denosumab are available. This clinical guide provides the evidence for the clinical use of selective estrogen modulators (SERMs) in the management of osteoporosis in postmenopausal women. [Copyright &y& Elsevier]

Selective estrogen-receptor modulators (SERMs), which have estrogen-like effects on bone and 'antiestrogen effects' on other tissues, have been in development for osteoporosis prevention and treatment in postmenopausal women as a safer alternative to long-term estrogen. We conducted a literature review of the skeletal and extraskeletal effects of lasofoxifene, a new generation SERM approved by the European Commission for osteoporosis treatment. Published data on the effects of lasofoxifene are based on 23 clinical pharmacology studies with over 10,000 participants from 17 phase 2 and 3 randomized controlled trials (RCTs). In RCTs, lasofoxifene decreases bone turnover markers (BTMs), increases bone mineral density (BMD) at the spine and hip, and decreases the incidence of vertebral and nonvertebral nonhip fractures compared with placebo. Compared with raloxifene, lasofoxifene gave greater decreases in BTMs, and greater increases in lumbar spine BMD. Lasofoxifene also decreased the risk of breast cancer, major coronary heart disease events, and stroke, but-similar to raloxifene-there was an increased risk of venous thromboembolism. In one trial, endometrial hypertrophy and uterine polyps were more common with lasofoxifene than with placebo, but endometrial cancer and hyperplasia were not. Lasofoxifene is probably most appropriate for use among women in their early or middle menopausal years (age 55-65) who have, or are at risk of developing, osteoporosis and in particular vertebral fractures. At the time of publication, lasofoxifene is not approved for use by the US Food and Drug Administration, and as such is not used in North America. [ABSTRACT FROM AUTHOR]

A Lewis acid-mediated three-component coupling reaction was successfully applied for the synthesis of lasofoxifene (1), nafoxidine (2), and their positional isomers, inv-lasofoxifene (3) and inv-nafoxidine (4). In the presence of HfCl4, the desired one-pot coupling reaction among 4-pivaloyloxybenzaldehyde (5), cinnamyltrimethylsilane (6), and anisole proceeded to afford the corresponding 3,4,4-triaryl-1-butene 7 in high yield. The iodocarbocyclization of the coupling product and the successive elimination of hydrogen iodide forming the olefin part, followed by the migration of the double-bond afforded the common synthetic intermediate of lasofoxifene (1) and nafoxidine (2) via a very concise procedure. Additionally, the syntheses of their positional isomers inv-lasofoxifene (3) and inv-nafoxidine (4) were also achieved through very convenient protocols. [ABSTRACT FROM AUTHOR]

Abstract: Lasofoxifene is a novel selective estrogen receptor modulator that is being developed for the treatment of postmenopausal osteoporosis. Bone mineral density (BMD) measured by dual-energy X-ray absorptiometry (DXA) is currently used to diagnose osteoporosis. BMD response to therapy, however, is often not apparent until at least one year following start of treatment. Biochemical markers of bone turnover may provide an early indication of BMD response in individual patients. The aims of the study were: 1) to determine the variability in bone turnover markers (BTM) to estimate a value for least significant change (LSC); 2) to determine the number of subjects with a response to lasofoxifene greater than LSC; 3) to determine the number of subjects whose bone turnover is decreased to the lower half of the reference range and 4) to evaluate the use of bone turnover markers to predict the change in bone density in response to lasofoxifene. Fifty-one postmenopausal osteopenic women, ages 55 to 77 (mean 63.7) years, were recruited with 44 women completing the 2 year follow up. Participants received either lasofoxifene (0.25 mg/d) or placebo, in a 1:1 ratio. Duplicate measurements of BTM (bone alkaline phosphatase (bone ALP), N-terminal propeptide of type I collagen (PINP), serum β crosslinked C-telopeptides of type I collagen (sβ-CTX), urinary crosslinked N-telopeptides of type I collagen (U-NTX)) were made at baseline and 6 months with single measurements at 4, 8 and 12 weeks. Duplicate measurements of BMD at the lumbar spine (LS), total hip (TH) and distal forearm (DF) were made by DXA at baseline, one and two years in all subjects. Almost all women (92 to 96%), treated with lasofoxifene, had a reduction in serum-based bone turnover markers greater than LSC, and 52 to 80% had serum-based bone turnover markers in the lower half of the reference range, by six months of lasofoxifene therapy. The change in mean LSBMD from baseline, was significantly greater in the lasofoxifene group compared to placebo at 1 and 2 years (+2.5% and +3.4%, respectively, P <0.0001). Change in PINP and U-NTX at 6 months correlated inversely with change in LS and TH BMD at one and two years. The use of lasofoxifene therapy leads to significant decreases in bone turnover by 4 weeks of lasofoxifene therapy as a group, with a decrease in BTM greater than LSC occurring in almost all women taking lasofoxifene by 6 months. By this time, in over half of women taking lasofoxifene, BTM reached the lower half of the reference range. Our results suggest that bone turnover markers are useful for monitoring response to lasofoxifene. Changes occur early and relate to the BMD response. [Copyright &y& Elsevier]

Introduction: Osteoporosis is a skeletal disorder characterized by compromised bone strength and increased risk of fracture. It is a common disorder in elderly subjects and represents a major public health problem, affecting up to 40% postmenopausal women and 15% of men. Among the several therapeutical interventions, hormone replacement therapy (HRT) was traditionally seen as the gold standard for preventing osteoporotic fractures in postmenopausal women, as well as for the management of menopausal symptoms. However HRT, especially if administered long-term, may lead to an increased risk of breast and, when unopposed by progestins, endometrial cancers. Alternative therapies include bisphosphonates and raloxifene, a selective estrogen receptor modulator (SERM). While the former have been associated with suboptimal adherence, the latter was considerably less potent than estrogen and its effect in the prevention of nonvertebral fractures remain uncertain. Aims: The purpose of this article is to review the clinical trials of lasofoxifene, a new SERM for the treatment of postmenopausal osteoporosis. The medical literature was reviewed for appropriate articles containing the terms "lasofoxifene" and SERMs". Evidence review: There are three (phase II or phase III) clinical trials that clearly demonstrate efficacy and safety of this new SERM in the suppression of bone loss and the prevention of vertebral and nonvertebral fractures. Moreover, lasofoxifene treatment also reduced breast cancer risk and the occurrence of vaginal atrophy. Place in therapy: With its increased potency and efficacy on the prevention of nonvertebral fractures lasofoxifene may be an alternative and cost-effective therapy for osteoporosis in postmenopausal women. [ABSTRACT FROM AUTHOR]

Abstract: Selective estrogen receptor modulators (SERMs) have the unique potential to provide estrogenic effects in the skeletal and cardiovascular system, while minimizing/eliminating side effects on reproductive organs. However, despite the unifying characteristic of mixed estrogen receptor (ER) agonist/antagonist activity, compounds within this class are not interchangeable. In order to define and compare the effects of SERMs on different hormone-responsive tissues, we evaluated effects of bazedoxifene acetate (BZA), lasofoxifene (LAS) and raloxifene (RAL) in the mammary gland and uterus of the ovariectomized mouse. Endpoints measured included those regulated by estradiol alone (uterine wet weight, uterine G protein-coupled receptor 105 (GPR105) mRNA expression and mammary gland indoleamine-pyrrole 2,3 dioxygenase (INDO) mRNA expression) as well as others that required the combination of estradiol and progesterone (uterine serine protease inhibitor Kazal type 3 (Spink3) mRNA expression, mammary gland morphology and mammary gland defensin β1 (Defβ1) mRNA expression). The three SERMs tested had variable agonist and antagonist activity on these endpoints. In the uterus, the SERMs were mixed agonists/antagonists on estradiol-induced wet weight increase, whereas all three SERMs were estrogen receptor antagonists on GPR105 mRNA expression. However, in the presence of progesterone, BZA and RAL were agonists on Spink3 expression, while LAS was primarily an antagonist. In the mammary gland, BZA and RAL were predominantly agonists on the endpoint of mammary morphology and all three SERMs were clear agonists on Defβ1 mRNA expression, an E+P-dependent marker. Finally, LAS and RAL had mixed agonist/antagonist activity on INDO mRNA expression, while BZA had only antagonist activity. These results demonstrate that compounds with small structural differences can elicit distinct biological responses, and that in general, SERMs tended to behave more as antagonists on endpoints requiring estrogen alone and agonists on endpoints requiring the combination of estrogen and progesterone. [Copyright &y& Elsevier]

Aims Two studies were conduced to assess the effects of ketoconazole, a CYP3A4/5 inhibitor; fluconazole, a CYP2C9 inhibitor; and paroxetine, a CYP2D6 inhibitor, on lasofoxifene pharmacokinetics. Methods The first parallel group study was conducted in 45 healthy postmenopausal women (15 per group) to compare the pharmacokinetics of a single dose of lasofoxifene (0.25 mg) administered alone and in combination with ketoconazole (400 mg daily × 20 days) or fluconazole (400 mg daily × 20 days). Lasofoxifene was administered on day 2 and blood samples were collected serially for up to 456 h postdose (20 days). The second study enrolled 20 healthy postmenopausal women (10 per group) to compare the pharmacokinetics of a single dose of lasofoxifene (0.25 mg) alone and in combination with paroxetine (30 mg qd × 21 days). Lasofoxifene was given on day 8 of paroxetine treatment and blood samples were collected serially for up to 336 h postdose. Results All subjects completed the study and the treatments were well tolerated. Lasofoxifene Cmax and AUC ratios [90% confidence interval (CI)] with/without ketoconazole were 111% (98.4, 127) and 120% (105, 136), respectively, and were 91.3% (80.3, 104) and 104% (91.4, 118), respectively, with/without fluconazole. Lasofoxifene Cmax and AUC ratios (90% CI) with/without paroxetine were 118% (95.4, 146) and 135% (120, 152), respectively. Conclusions Coadministration of potent inhibitors of CYP3A4/5 and CYP2D6, but not CYP2C9, resulted in a moderate increase in lasofoxifene exposure. No dosage adjustment should be required when lasofoxifene is coadministered with ketoconazole, fluconazole, paroxetine or other agents that inhibit these CYP enzymes. [ABSTRACT FROM AUTHOR]

Aim To investigate the effect of steady-state lasofoxifene on the pharmacokinetics and pharmacodynamics of warfarin. Methods Twelve healthy postmenopausal women received warfarin (single 20-mg dose) alone and during lasofoxifene. R- and S-warfarin concentrations, prothrombin time (PT) and international normalized ratio (INR) were determined with each treatment. Results Lasofoxifene had no clinically meaningful effect on R- or S-warfarin pharmacokinetics. The S-warfarin area under the plasma concentration–time curve (AUC) was 23% and 67% larger in subjects with *1/*2 and *1/*3 heterozygous mutations, relative to *1/*1, respectively. The mean PT AUC and Cmax ratio (90% confidence interval) was 91.9 (89.6, 94.2) and 84.2 (80.6, 87.8), respectively. INR results were similar. Conclusions Lasofoxifene has no clinically meaningful effect on the pharmacokinetics of warfarin. Although the decrease in PT/INR may not be clinically meaningful, more frequent INR monitoring may be considered during lasofoxifene introduction and discontinuation, consistent with warfarin’s label. [ABSTRACT FROM AUTHOR]

Lasofoxifene, a next-generation selective estrogen receptor modulator, is undergoing phase 3 clinical development for osteoporosis. This study evaluated daily lasofoxifene for 14 days in healthy postmenopausal women. A loading dose of 5 times the daily dose was followed by daily doses of 0.01 mg (n = 8), 0.03mg(n = 8), 0.1mg (n = 16), 0.3mg(n = 9), 1mg (n = 8), or placebo (n = 16). Samples were collected for pharmacokinetic and pharmacodynamic assessments. Lasofoxifene was well tolerated; study drug–associated adverse events were mild and unrelated to dose. There was a predictable increase in plasma concentrations of lasofoxifene with dose. Pharmacokinetic parameters included-mean half-life of 165 hours, mean area under the plasma concentration-time curve from time 0 to 24 hours ranging from 1.67 ng•h/mL to 137 ng• h/mL, and mean maximum observed plasma concentration ranging from 0.09 ng/mL to 6.43 ng/mL. Lasofoxifene partially suppressed luteinizing hormone, follicle-stimulating hormone, lowdensity lipoprotein, and N-telopeptide. [ABSTRACT FROM PUBLISHER]

Lasofoxifene, a selective estrogen receptor modulator for osteoporosis management, is metabolized primarily by hepatic oxidation and conjugation. This study compared the pharmacokinetics of 0.25 mg lasofoxifene in subjects with mild (Child-Pugh grade A, n = 6) or moderate (Child-Pugh grade B, n = 6) hepatic impairment and healthy volunteers (n = 6). Analysis of variance was used to calculate 90% confidence intervals for the ratios (impaired/healthy) of least squares mean log maximum plasma concentration (Cmax) and area under the curve (AUC) values. Lasofoxifene pharmacokinetics was similar between healthy and mild hepatic impairment subjects: ratios of C max and AUC from 0 to infinity (AUC[ 0-8]) were 101% (75.0-138) and 95.5% (77.9-117), respectively. In subjects with moderate hepatic impairment, ratios of C max and AUC [0-8] were 121% (89.6-165) and 138% (112-169), respectively; mean terminal half-life was 252 hr compared to 193 hr in healthy subjects. Dose adjustment should not be required for subjects withmild to moderate hepatic impairment. [ABSTRACT FROM PUBLISHER]

Lasofoxifene is in late-stage development for the prevention and treatment of osteoporosis. Digoxin is commonly prescribed for arrhythmias and congestive heart failure, has a narrow therapeutic index, and may be coadministered with lasofoxifene. This study was conducted to determine the effect of lasofoxifene (4-mg loading dose on day 11 followed by 0.5 mg/d on days 12-20) on the steady-state pharmacokinetics of digoxin (0.25 mg/d on days 1-20) in 12 healthy post-menopausal women. On days 10 and 20, blood and urine samples were collected for 24 hours to determine digoxin concentrations. The 90% confidence interval (CI) of least squares mean ratio for maximum concentration (Cmax)and area under the plasma concentration-time curve (AUC) was calculated. Lasofoxifene had no effect on digoxin plasma pharmacokinetics with a ratio (90% CI) of 95.4% (84.6%-107%) and 103% (97.7%-108%) for Cmaxand AUC0-24, respectively. The ratio of the percentage of dose eliminated unchanged in urine in 24 hours was 127% (116% to 142%). Coadministration of lasofoxifene had no effect on the steady-state pharmacokinetics of digoxin. [ABSTRACT FROM PUBLISHER]

Lasofoxifene [CP 336156] is a potent, nonsteroidal, tissue-selective estrogen receptor modulator (SERM). It has the bone-sparing and cardioprotective effects of estrogen, but lacks estrogen's uterine cancer risk. Lasofoxifene is under development with Ligand Pharmaceuticals and Pfizer (formerly Parke-Davis) for the prevention of postmenopausal osteoporosis and breast cancer. In June 2000, Parke-Davis' parent company, Warner-Lambert, merged with Pfizer. The resulting company retained the Pfizer name and Parke-Davis was integrated into Pfizer Global Research and Development. The discovery of lasofoxifene resulted from a research collaboration between Pfizer and Ligand Pharmaceuticals. There was a contract dispute between the two companies relating to their research agreement. Under a settlement of litigation, Ligand is entitled to milestone and royalty payments. If Pfizer is successful in developing the drug through to regulatory approval in the US, Ligand could receive royalty revenues from lasofoxifene as early as 2003–2004. The royalties will be equal to 6% of net sales and will be in addition to milestone payments for continuing development of the drug. However, on 6 March 2002, Ligand Pharmaceutical announced an agreement with Royalty Pharma in which the latter purchased the rights to a share of these future payments. Under the agreement, Ligand received $US6 million from Royalty Pharma in exchange for a 0.25% stake in net sales of three SERM products (lasofoxifene, bazedoxifene and bazedoxifene/Premarin®) for a period of 10 years. Royalty Pharma retains the option to purchase, at escalating prices, additional rights (subject to timing restrictions) to extend this stake up to 1.0%, for a total of $US56 million. In April 2002, Royalty Pharma exercised its first option to purchase an additional 0.125% of potential future sales of the three SERMS in exchange for $US3 million. Subsequently, in December 2002, Royalty Pharma exercised an expanded option and agreed to pay Ligand $US6.775 million for 0.1875% of potential future sales of SERM products. Royalty Pharma and Ligand Pharmaceutical amended their royalty agreement in October 2003 for the three SERM products. Under the amended agreement, Royalty Pharma exercised an option to pay Ligand $US12.5 million, plus cumulative milestones of up to $US2.5 million upon the launches of the three SERMs (provided they are approved by 30 September 2005), in exchange for 0.7% of potential future sales of the products for 10 years. In November 2004, Ligand Pharmaceuticals and Royalty Pharma further amended their existing royalty agreement for the three SERM products. Under the terms of the revised agreement, Royalty Pharma will purchase an additional 1.625% of the SERM products' net sales for $US32.5 million, which represents an acceleration of the previous option timetable and an increase in the royalty amount as well as aggregate purchase price. Consequently, Royalty Pharma increased its rights to a total of 3.0125% of net sales of each SERM product for 10 years following the first commercial sale of each product and has no further options. Ligand retains an approximately equal portion of lasofoxifene and other SERM's net sales going forward and for periods that could exceed 10 years. The royalty rates owed to Royalty Pharma for the royalties just purchased could be reduced by one-third if product sales exceed certain thresholds. Payments from the royalty purchase are non-refundable, regardless of whether the products ever become successfully launched or not. Milestone payments owed by Ligand's partners as products achieve development and regulatory targets will be paid to Ligand as earned and are not included in this amended agreement. In September 2004, Ligand Pharmaceuticals earned a milestone payment of approximately $US2 million from Pfizer, payable in 181 818 shares of Ligand stock held by Pfizer. The payment was triggered by Pfizer's NDA submission for lasofoxifene in August 2004. Under the terms of the agreement between Ligand and Pfizer, Ligand is entitled to receive an additional milestone upon successful approval of lasofoxifene. On 19 August 2004, Pfizer filed an NDA with the US FDA for lasofoxifene for the prevention of osteoporosis in postmenopausal women. Product launch is forecasted to occur in 2006–2007. Ligand reported in January 2004 at the 22nd Annual JP Morgan Healthcare Conference that it anticipated the availability of phase III data and NDA filing sometime in 2004. Lasofoxifene has undergone two phase III studies with Pfizer in the US as an orally administered therapy for postmenopausal osteoporosis. In June 2003, Pfizer reported that enrolment was completed in a trial evaluating lasofoxifene in the prevention of bone loss. The trial also evaluated lasofoxifene's effect on lipid levels. The trial enrolled ≊2000 postmenopausal women. Another trial was conducted among 8500 patients to investigate lasofoxifene in the treatment of fractures. In addition, Pfizer began a third worldwide phase III trial to evaluate whether lasofoxifene reduced the risk of vertebral fractures, breast cancer and cardiovascular disease. At the 10th Annual Meeting of the Biotechnology Industry Organization (BIO-2003), Ligand also confirmed that lasofoxifene was in phase III development for breast cancer. Lasofoxifene is under clinical evaluation as a treatment for vaginal atrophy. According to Pfizer's pipeline in November 2004, the company anticipates regulatory submission for vaginal atrophy by the end of 2004. In June 2002, Ligand estimated that lasofoxifene has the potential to reach sales of $US1–2 billion, pending approval. [ABSTRACT FROM AUTHOR]

Neuroprotective effects of estradiol are well characterized in animal experimental models. However, in humans, the outcome of estrogen treatment for cognitive function and neurological diseases is very controversial. Selective estrogen receptor modulators (SERMs) may represent an alternative to estrogen for the treatment or the prevention of neurodegenerative disorders. SERMs interact with the estrogen receptors and have tissue-specific effects distinct from those of estradiol, acting as estrogen agonists in some tissues and as antagonists in others. In this study we have assessed the effect of tamoxifen, raloxifene, lasofoxifene (CP-336,156), bazedoxifene (TSE-424), and 17β-estradiol on the hippocampus of adult ovariectomized rats, after the administration of the excitotoxin kainic acid. Administration of kainic acid induced the expression of vimentin in reactive astroglia and a significant neuronal loss in the hilus. SERMs did not affect vimentin immunoreactivity in the hilus, while 17β-estradiol significantly reduced the surface density of vimentin immunoreactive profiles. Estradiol, tamoxifen (0.4-2 mg/kg), raloxifene (0.4-2 mg/kg), and bazedoxifene (2 mg/kg) prevented neuronal loss in the hilus after the administration of kainic acid. Lasofoxifene (0.4-2 mg/kg) was not neuroprotective. These findings indicate that SERMs present different dose-dependent neuroprotective effects. Furthermore, the mechanisms of neuroprotection by SERMs and estradiol are not identical, because SERMs do not significantly affect reactive gliosis while neuroprotection by estradiol is associated with a strong down-regulation of reactive astroglia. © 2004 Wiley Periodicals, Inc. J Neurobiol, 2004 [ABSTRACT FROM AUTHOR]

Selective estrogen receptor modulators (SERMs) are estrogen receptor (ER) ligands that function as antagonists in some tissues, but have either partial or full agonist activity in others. SERMs often display variable partial agonist activity in uterine tissues and this activity can be displayed in uterine cell lines such as the human Ishikawa endometrial adenocarcinoma cell line. In this study, we compared the effects of several ER ligands including some SERMs on alkaline phosphatase (AP) activity and the expression of an ER target gene, the progesterone receptor (PR), in Ishikawa cells. As expected, estradiol (E2) was a potent and efficacious activator of both AP activity and PR mRNA expression. 4-Hydroxytamoxifen (4OHT) stimulated AP activity to a level 47% of that of E2 (100 nM), while CP 336156 (lasofoxifene) increased AP activity 18%. A benzothiophene, such as LY 117018, a raloxifene analog, stimulated AP even less with values approximately 11% of E2-stimulated levels. A pure antiestrogen, ICI 182,780 did not stimulate AP activity. Interestingly, when we examined the ability of these compounds to increase the expression of the ER target gene, PR, a different rank order of efficacy was detected. After E2, CP 336156 was the most efficacious in increasing PR mRNA with a maximal stimulation of 20% of E2 levels, while 4OHT stimulated only 17%. LY 117018 increased PR mRNA expression 8% while ICI 182,780 did not increase PR mRNA expression at all. These data illustrate the target specificity that a SERM is able to display within a single cell type independent of “tissue specificity” and differential levels of expression of various cofactors. While 4OHT is 160% more active than CP 336156 in terms of inducing AP activity in the Ishikawa cells, CP 336156 has equivalent activity as 4OHT when one examines the ability of these SERMs to induce PR mRNA expression. Since the stimulation of Ishikawa cells by ER ligands is often used to assess the potential in vivo uterotrophic activity, these data indicate that examination of several endpoints in these cells may be necessary in order to fully characterize the activity of SERMs. [Copyright &y& Elsevier]