Selective Estrogen Receptor Modulators for Postmenopausal Osteoporosis

LC-MS/MS method for simultaneous estimation of raloxifene, cladrin in rat plasma: application in pharmacokinetic studies

Aim: A newer LC-MS/MS method was developed and validated for the simultaneous quantification of raloxifene (RL) and cladrin (CL). Methodology: Both drugs were resolved in RP-18 (4.6 × 50 mm, 5 μ) Xbridge Shield column using acetonitrile and 0.1% aqueous solution of formic acid (FA) (70:30% v/v) as mobile phase by using biological matrices in female Sprague-Dawley rats using-MS/MS. Results: The developed method was found to be linear over the concentration ranges of 1-600 ng/ml, and lower limit of quantification was 1 ng/ml for RL and CL, respectively. Pharmacokinetic results of RL+CL showed Cmax = 4.23 ± 0.61, 26.97 ± 1.14 ng/ml, at Tmax(h) 5.5 ± 1.00 and 3.5 ± 1.00, respectively. Conclusion: Pharmacokinetic study results will be useful in the future for the combined delivery of RL and CL for osteoporosis treatment.

Novel Advances in the Role of Selective Estrogen Receptor Modulators in Hormonal Replacement Therapy: A Paradigm Shift

Estrogen is a key regulatory hormone in the functioning of a female reproductive system. Estrogen hormone regulates many complex physiological processes, which has its role in reproduction and skeletal and cardiovascular systems by acting on estrogen receptors alpha (ERα) and beta (ERβ), which are nuclear transcription factors. Selective estrogen receptor modulators (SERMs) are now being used to treat bone loss, breast carcinoma, and menopausal symptoms, metabolic neurodegenerative because of their characteristics that allow them to function as both estrogen agonists and antagonists, depending on the target tissue. First-generation SERMs, such as Tamoxifen, are used in the management protocol for breast cancer, which is estrogen receptor (ER-positive). Raloxifene is a second-generation SERM that is a valuable adjunct used to treat and prevent osteoporosis in postmenopausal women and prevent compression fractures of the vertebral column. Novel SERM molecules are on the horizon, proven more potent and efficacious in preventing and treating osteoporosis. These include Ospemifene, lasofoxifene, bazedoxifene and arzoxifene. The benefits of Raloxifene versus that of Bazedoxifene are under trial. Despite their therapeutic benefits and actions, these medications are not without adverse effects, such as thromboembolic disorders. Increased risk of uterine cancer has been linked to Tamoxifen. This article delves into the world of SERMs, including their development and discovery. The newer SERMs in late development, ospemifene, lasofoxifene, bazedoxifene, and arzoxifene, are described in detail.

Repurpose dasatinib and quercetin: Targeting senescent cells ameliorates postmenopausal osteoporosis and rejuvenates bone regeneration

Clinical therapies developed for estrogen-deficiency-driven postmenopausal osteoporosis (PMO) and related diseases, such as bone degeneration, show multiple adverse effects nowadays. Targeting senescent cells (SnCs) and the consequent senescence-associated secretory phenotype (SASP) with a combination of dasatinib and quercetin (DQ) is a recently developed novel therapy for multiple age-related diseases. Herein, we found that estrogen deficiency induced-bone loss was attributed to a pro-inflammatory microenvironment with SASP secretions and accelerated SnC accumulation, especially senescent mesenchymal stem cells (MSCs) characterized by exhaustion and dysfunction in middle aged rats. Systematically targeting SnCs with DQ strikingly ameliorated PMO and restored MSC function. Local administration of DQ and bone morphogenetic protein 2 (BMP2) in combination promoted osteogenic differentiation of MSCs and rejuvenated osteoporotic bone regeneration. Our results repurposed DQ as an attractive therapy for treating PMO and related diseases.

Bone regeneration in osteoporosis: opportunities and challenges

Osteoporosis is a bone disorder characterised by low bone mineral density, reduced bone strength, increased bone fragility, and impaired mineralisation of bones causing an increased risk of bone fracture. Several therapies are available for treating osteoporosis which include bisphosphonates, anti-resorptive agents, oestrogen modulators, etc. These therapies primarily focus on decreasing bone resorption and do not assist in bone regeneration or offering permanent curative solutions. Additionally, these therapies are associated with severe adverse events like thromboembolism, increased risk of stroke, and hypocalcaemia. To overcome these limitations, bone regenerative pathways and approaches are now considered to manage osteoporosis. The bone regenerative pathways involved in bone regeneration include wingless-related integration site/β-catenin signalling pathway, notch signalling pathway, calcium signalling, etc. The various regenerative approaches which possess potential to heal and replace the bone defect site include scaffolds, cements, cell therapy, and other alternative medicines. The review focuses on describing the challenges and opportunities in bone regeneration for osteoporosis.

Dietary intervention with Tinospora cordifolia improved aging-related decline in locomotor coordination and cerebellar cell survival and plasticity in female rats

Reduced bone mineral density, and muscle strength are the hallmark of aging-related motor coordination deficits and related neuropathologies. Since cerebellum regulates motor movements and balance perception of our body, therefore it may be an important target to control the age-related progression of motor dysfunctions. Dry stem powder of Tinospora cordifolia (TCP) was tested as a food supplement to elucidate its activity to attenuate age-associated locomotor dysfunctions. Intact acyclic middle-aged female rats were used in this study as the model system of the transition phase from premenopause to menopause in women along with cycling young adult rats. Normal chow or 30% High Fat Diet (HFD), supplemented with or without TCP was fed to animals for 12 weeks and then tested for locomotor performance on rotarod followed by post-sacrifice protein expression studies. In comparison to young adults, middle-aged animals showed an increase in number of falls and lesser time spent in rotarod performance test, whereas, animals given TCP supplemented feed showed improvement in performance with more pronounced effects observed in normal chow than HFD fed middle-aged rats. Further, due to its multicomponent nature TCP was found to target the expression of various markers of neuroinflammation, apoptosis, cell survival, and synaptic plasticity in the cerebellum region. The current findings suggest that TCP supplementation in the diet may prove to be a potential interventional strategy for the management of frailty and fall-associated morbidities caused by aging-related deterioration of bone mineral density, and muscle strength.

StarGazer: A Hybrid Intelligence Platform for Drug Target Prioritization and Digital Drug Repositioning Using Streamlit

Target prioritization is essential for drug discovery and repositioning. Applying computational methods to analyze and process multi-omics data to find new drug targets is a practical approach for achieving this. Despite an increasing number of methods for generating datasets such as genomics, phenomics, and proteomics, attempts to integrate and mine such datasets remain limited in scope. Developing hybrid intelligence solutions that combine human intelligence in the scientific domain and disease biology with the ability to mine multiple databases simultaneously may help augment drug target discovery and identify novel drug-indication associations. We believe that integrating different data sources using a singular numerical scoring system in a hybrid intelligent framework could help to bridge these different omics layers and facilitate rapid drug target prioritization for studies in drug discovery, development or repositioning. Herein, we describe our prototype of the StarGazer pipeline which combines multi-source, multi-omics data with a novel target prioritization scoring system in an interactive Python-based Streamlit dashboard. StarGazer displays target prioritization scores for genes associated with 1844 phenotypic traits, and is available via https://github.com/AstraZeneca/StarGazer.

Drug Delivery to the Bone Microenvironment Mediated by Exosomes: An Axiom or Enigma

The increasing incidence of bone-related disorders is causing a burden on the clinical scenario. Even though bone is one of the tissues that possess tremendous regenerative potential, certain bone anomalies need therapeutic intervention through appropriate delivery of a drug. Among several nanosystems and biologics that offer the potential to contribute towards bone healing, the exosomes from the class of extracellular vesicles are outstanding. Exosomes are extracellular nanovesicles that, apart from the various advantages, are standing out of the crowd for their ability to conduct cellular communication. The internal cargo of the exosomes is leading to its potential use in therapeutics. Exosomes are being unraveled in terms of the mechanism as well as application in targeting various diseases and tissues. Through this review, we have tried to understand and review all that is already established and the gap areas that still exist in utilizing them as drug delivery vehicles targeting the bone. The review highlights the potential of the exosomes towards their contribution to the drug delivery scenario in the bone microenvironment. A comparison of the pros and cons of exosomes with other prevalent drug delivery systems is also done. A section on the patents that have been generated so far from this field is included.

Molecular Signaling Pathways and Essential Metabolic Elements in Bone Remodeling: An Implication of Therapeutic Targets for Bone Diseases

Bone is one of the dynamic tissues in the human body that undergoes continuous remodelling through subsequent actions of bone cells, osteoclasts, and osteoblasts. Several signal transduction pathways are involved in the transition of mesenchymal stem cells into osteoblasts. These primarily include Runx2, ATF4, Wnt signaling and sympathetic signalling. The differentiation of osteoclasts is controlled by M-CSF, RANKL, and costimulatory signalling. It is well known that bone remodelling is regulated through receptor activator of nuclear factor-kappa B ligand followed by binding to RANK, which eventually induces the differentiation of osteoclasts. The resorbing osteoclasts secrete TRAP, cathepsin K, MMP-9 and gelatinase to digest the proteinaceous matrix of type I collagen and form a saucer-shaped lacuna along with resorption tunnels in the trabecular bone. Osteoblasts secrete a soluble decoy receptor, osteoprotegerin that prevents the binding of RANK/RANKL and thus moderating osteoclastogenesis. Moreover, bone homeostasis is also regulated by several growth factors like, cytokines, calciotropic hormones, parathyroid hormone and sex steroids. The current review presents a correlation of the probable molecular targets underlying the regulation of bone mass and the role of essential metabolic elements in bone remodelling. Targeting these signaling pathways may help to design newer therapies for treating bone diseases.

Updates in epidemiology, pathophysiology and management strategies of glucocorticoid-induced osteoporosis

INTRODUCTION

Endogenous or exogenous (corticosteroid-induced) glucocorticoids (GCs) excess represents, together with diabetes, the most common cause of secondary osteoporosis.

AREAS COVERED

We present a comprehensive overview about the pathophysiology, clinical management and treatment of GCs induced osteoporosis (GIOP). According to PRISMA guidelines, a literature search identifying articles about bone and GCs was done.

EXPERT OPINION

Despite the progress over the years and the increase in therapeutic options, there still are controversial issues about the management of GIOP. These mainly include the failure of BMD or FRAX to completely account for the rapid increase in fracture risk of most GC-treated patients, the understanding about the independent contribution on bone fragility of the underlying disease requiring GCs therapy, and the necessity of clearer information about the anti-fracture efficacy and long term-safety of most therapeutic options. Moreover, there are no specific indications for the management of bone fragility in endogenous hypercortisolism. Notwithstanding the above limitations there is a general consensus to recommend an assessment of fracture risk in all individuals >40 years committed to receive (or continuing) high dose (>7.5 mg of prednisone equivalent) GCs for ≥3 months and in all patients with fragility fracture history.

Emerging therapeutic targets for osteoporosis

Introduction: Osteoporosis is a chronic, skeletal disorder characterized by compromised bone strength and increased fracture risk; it affects 50% of women and 20% of men. In the past two decades, there have been substantial improvements in the pharmacotherapy of osteoporosis which have yielded potent inhibitors of bone resorption or stimulators of bone formation.Areas covered: This review discusses newly identified targets and pathways and conceptual approaches to the prevention of multiple age-related disorders. Furthermore, it summarizes existing therapeutic strategies for osteoporosis.Expert opinion: Our enhanced understanding of bone biology and the reciprocal interactions between bone and other tissues have allowed the identification of new targets that may facilitate the development of novel drugs. These drugs will hopefully achieve the uncoupling of bone formation from resorption and possibly exert a dual anabolic and antiresorptive effect on bone. Alas, limitations regarding adherence, efficacy on nonvertebral fracture prevention and the long-term adverse events still exist for currently available therapeutics. Moreover, the efficacy of most agents is limited by the tight coupling of osteoblasts and osteoclasts; hence the reduction of bone resorption invariably reduces bone formation, and vice versa. This field is very much 'a work in progress.'

Treatment options for glucocorticoid-induced osteoporosis

INTRODUCTION

Glucocorticoid (GC) induced osteoporosis (GIOP) is the most common form of secondary osteoporosis. It develops in a dose and time dependent manner, due to a rapid and transient increase in bone resorption, followed by the inhibition of bone formation.

AREAS COVERED

In this review, the authors summarize the pathophysiology of GIOP and give discussion to the clinical management of patients taking GCs, focusing on the currently available drugs that have antiresorptive or anabolic activity on bone.

EXPERT OPINION

Despite the widespread use of GCs and their well-established detrimental skeletal effects, GIOP remains an under-diagnosed and under-treated condition. Indeed, the clinical management of GIOP is still debated, so that the recent guidelines differ in their indications for pharmacological intervention. Either bone mineral density (BMD) or algorithms such as FRAX do not completely account for the remarkable and rapid increase in fracture risk of most GC-treated patients. Moreover, while oral bisphosphonates remain the most used and cost-effective option, the potential increased benefits of more potent antiresorptive agents (e.g. denosumab and zoledronate) or anabolic compounds (e.g. teriparatide) warrant further investigation. Despite the above limitations, the assessment of fracture risk is recommended for all individuals committed to receiving oral GCs for 3 months or longer.

Estrogen receptor signaling mechanisms

The primary female sex hormones, estrogens, are responsible for the control of functions of the female reproductive system, as well as the development of secondary sexual characteristics that appear during puberty and sexual maturity. Estrogens exert their actions by binding to specific receptors, the estrogen receptors (ERs), which in turn activate transcriptional processes and/or signaling events that result in the control of gene expression. These actions can be mediated by direct binding of estrogen receptor complexes to specific sequences in gene promoters (genomic effects), or by mechanisms that do not involve direct binding to DNA (non-genomic effects). Whether acting via direct nuclear effects, indirect non-nuclear actions, or a combination of both, the effects of estrogens on gene expression are controlled by highly regulated complex mechanisms. In this chapter, we summarize the knowledge gained in the past 60years since the discovery of the estrogen receptors on the mechanisms governing estrogen-mediated gene expression. We provide an overview of estrogen biosynthesis, and we describe the main mechanisms by which the female sex hormone controls gene transcription in different tissues and cell types. Specifically, we address the molecular events governing regulation of gene expression via the nuclear estrogen receptors (ERα, and ERβ) and the membrane estrogen receptor (GPER1). We also describe mechanisms of cross-talk between signaling cascades activated by both nuclear and membrane estrogen receptors. Finally, we discuss natural compounds that are able to target specific estrogen receptors and their implications for human health and medical therapeutics.

Effects of the Hormone Replacement Therapy and of Soy Isoflavones on Bone Resorption in Postmenopause

Postmenopausal osteoporosis is the most common form of osteoporosis and one of the major public health problems in developed countries. The prevalence of this condition, associated with the physiological stage of menopause, is continuously increasing. This study evaluated the effectiveness of soy isoflavones as compared to hormone replacement therapy (HRT) in low doses, on the prevention of postmenopausal osteoporosis, by determining bone mineral density (BMD) and urinary deoxypyridinoline (D-pyr) in physiological postmenopausal women. The study was conducted over a period of 12 months, on three parallel groups, which included a total of 325 postmenopausal women (HRT group: n = 95; phytoestrogens group: n = 124; control group: n = 106). At the one-year evaluation, we observed T-score normalization in a small number of cases (5.26%, 2.42% and 0.00%, respectively). The average values of D-Pyr decreased by 11.38% in the group treated with phytoestrogens (p < 0.05) and by 15.32% in the group that followed HRT (p < 0.05); it increased by 4.38% in the control group (p > 0.05). Both therapies have beneficial effects on bone metabolism, leading to a significant decrease in the evolution of bone resorption and there are no major differences between the efficacy of HRT and phytoestrogens in terms of the effects on BMD and bone resorption.

Selective Estrogen Receptor Modulator and prostimulatory effects of phytoestrogen β-ecdysone in Tinospora cordifolia on osteoblast cells

BACKGROUND

Indian ethnomedicine acclaims Tinosporacordifolia as a bone strengthening agent and prescribes it for the treatment of bone fractures, gout and other inflammatory diseases of the bone.

OBJECTIVE

(a) To understand the potential of T. cordifolia to act as a Selective Estrogen Receptor Modulator (SERM) on in vitro models. (b) To understand the toxic effects (if any) of T. cordifolia in vivo. (c) To understand the effects of β-ecdysone (proposed osteoprotective principle of T. cordifolia) on the growth of human osteoblast-like cells MG-63 and rat primary culture of osteoblasts. (d) To conduct phytochemical analysis on T. cordifolia extract to confirm the presence of β-ecdysone.

MATERIALS AND METHODS

The role of T. cordifolia as SERM was analyzed by investigating the effect of the extract on the growth of MCF-7 and HeLa cells. The effects of T. cordifolia in vivo was studied by biochemical (Liver function and renal function tests) and histopathological (Hematoxylin/Eosin staining) analysis. Phytochemical analysis of T.cordifolia was carried out by performing FT-IR and LC-ESI-MS analysis.

RESULTS

(a) T. cordifolia extract exerted non-estrogenic effects on MCF-7 and HeLa cells implicating its role as SERM. (b) High doses of T. cordifolia extract (750 and 1000 mg/kg body wt.) showed impairment of hepatic and renal function, induced pathological alterations in hepatic and renal architecture in albino rats. (c) β-ecdysone an ecdysteroid proposed as the osteoprotective principle of T. cordifolia exhibited significant prostimulatory effects on osteoblast cells and rat primary osteoblasts. (d) Phytochemical analysis confirmed the presence of β-ecdysone in alcoholic extract of T. cordifolia extract substantiating its role as the osteoprotective principle of T. cordifolia.

CONCLUSION

(a) T. cordifolia could function as SERM and can have applications in the therapy of osteoporosis. (b) β-ecdysone is the osteoprotective principle of T. cordifolia.

Recent advances in models for screening potential osteoporosis drugs

INTRODUCTION

Osteoporosis is a growing health and health-economic problem due to the increased proportion of elderly people in the population. Basic and clinical advances in research over the past two decades have led to the development of different compounds with antiresorptive or anabolic activity on bone that improved substantially the management of patients with osteoporosis over calcitonin or estrogen replacement. New compounds are in preclinical and clinical development. Areas covered: In this review, the authors review the approaches for the preclinical and clinical development of antiresorptive and anabolic agents for osteoporosis, particularly focusing on the recent advances in technology and in the understanding of skeletal biology, together with their implications on novel osteoporosis drug discovery. Expert opinion: Based on the available evidence from the approved drugs for the treatment osteoporosis as well as from the different compounds under clinical development, it has become clear that long term nonclinical pharmacological studies with either bone quality and off-target effects as the main outcomes should be required for new drugs intended to treat osteoporosis. At the same time, basic and clinical advances in research have underlined the necessity to develop new technologies and new models for a thorough screening of the effects of new drugs on the different components of skeletal aging and bone fragility that cannot be assessed by bone mass measurement.

Development of concise two-step catalytic approach towards lasofoxifene precursor nafoxidine

We have elaborated a two-step catalytic approach to nafoxidine, a key precursor to lasofoxifene. Firstly, an efficient α-arylation of 6-methoxy-3,4-dihydronaphthalen-1(2H)-one with chlorobenzene was developed, which operates at low 0.1 mol% Pd-132 catalyst loading in the presence of 1.9 equivalents of sodium tert-butoxide at 60 °C in 1,4-dioxane and provides 6-methoxy-2-phenyl-3,4-dihydronaphthalen-1(2H)-one in 90% yield. Secondly, we have demonstrated that 6-methoxy-2-phenyl-3,4-dihydronaphthalen-1(2H)-one can be converted to nafoxidine in 61% yield via CeCl₃ promoted reaction with (4-(2-(pyrrolidin-1-yl)ethoxy)phenyl)lithium, which is formed in-situ from the corresponding arylbromide precursor and n-butyllithium. Altogether, the shortest two-step approach to nafoxidine from simple tetralone commodity starting material has been developed with overall 55% yield. The developed synthetic approach to nafoxidine has several beneficial aspects over the one used in the synthetic route primarily developed for the preparation of lasofoxifene.

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

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

Acid promoted Ir–P^N complex catalyzed hydrogenation of heavily hindered 3,4-diphenyl-1,2-dihydronaphthalenes: asymmetric synthesis of lasofoxifene tartrate

An asymmetric hydrogenation of minimally functionalized tetrasubstituted cyclic olefins has been developed using an Ir–P^N catalyst and an acid additive enabling the synthesis of lasofoxifene tartrate.

Pathway Analysis Revealed Potential Diverse Health Impacts of Flavonoids that Bind Estrogen Receptors

Flavonoids are frequently used as dietary supplements in the absence of research evidence regarding health benefits or toxicity. Furthermore, ingested doses could far exceed those received from diet in the course of normal living. Some flavonoids exhibit binding to estrogen receptors (ERs) with consequential vigilance by regulatory authorities at the U.S. EPA and FDA. Regulatory authorities must consider both beneficial claims and potential adverse effects, warranting the increases in research that has spanned almost two decades. Here, we report pathway enrichment of 14 targets from the Comparative Toxicogenomics Database (CTD) and the Herbal Ingredients’ Targets (HIT) database for 22 flavonoids that bind ERs. The selected flavonoids are confirmed ER binders from our earlier studies, and were here found in mainly involved in three types of biological processes, ER regulation, estrogen metabolism and synthesis, and apoptosis. Besides cancers, we conjecture that the flavonoids may affect several diseases via apoptosis pathways. Diseases such as amyotrophic lateral sclerosis, viral myocarditis and non-alcoholic fatty liver disease could be implicated. More generally, apoptosis processes may be importantly evolved biological functions of flavonoids that bind ERs and high dose ingestion of those flavonoids could adversely disrupt the cellular apoptosis process.

The Effect of Osteoporosis Treatments on Fatigue Properties of Cortical Bone Tissue

Bisphosphonates are commonly prescribed for treatment of osteoporosis. Long-term use of bisphosphonates has been correlated to atypical femoral fractures (AFF). AFFs arise from fatigue damage to bone tissue that cannot be repaired due to pharmacologic treatments. Despite fatigue being the primary damage mechanism of AFFs, the effects of osteoporosis treatments on fatigue properties of cortical bone are unknown. To examine if fatigue-life differences occur in bone tissue after different pharmacologic treatments for osteoporosis, we tested bone tissue from the femurs of sheep given a metabolic acidosis diet to induce osteoporosis, followed by treatment with a selective estrogen reception modulator (raloxifene), a bisphosphonate (alendronate or zoledronate), or parathyroid hormone (teriparatide, PTH). Beams of cortical bone tissue were created and tested in four-point bending fatigue to failure. Tissues treated with alendronate had reduced fatigue life and less modulus loss at failure compared to other treatments, while tissue treated with PTH had a prolonged fatigue life. No loss of fatigue life occurred with zoledronate treatment despite its greater binding affinity and potency compared to alendronate. Tissue mineralization measured by microCT did not explain the differences seen in fatigue behavior. Increased fatigue life with PTH suggests that current treatment methods for AFF could have beneficial effects for restoring fatigue life. These results indicate that fatigue life differs with each type of osteoporosis treatment.

Selective estrogen receptor modulators: tissue specificity and clinical utility

Selective estrogen receptor modulators (SERMs) are a diverse group of nonsteroidal compounds that function as agonists or antagonists for estrogen receptors (ERs) in a target gene-specific and tissue-specific fashion. SERM specificity involves tissue-specific expression of ER subtypes, differential expression of co-regulatory proteins in various tissues, and varying ER conformational changes induced by ligand binding. To date, the major clinical applications of SERMs are their use in the prevention and treatment of breast cancer, the prevention of osteoporosis, and the maintenance of beneficial serum lipid profiles in postmenopausal women. However, SERMs have also been found to promote adverse effects, including thromboembolic events and, in some cases, carcinogenesis, that have proven to be obstacles in their clinical utility. In this review, we discuss the mechanisms of SERM tissue specificity and highlight the therapeutic application of well-known and emergent SERMs.

Poly (ε-caprolactone) nanocapsules for oral delivery of raloxifene: process optimization by hybrid design approach, in vitro and in vivo evaluation

Raloxifene HCl (RLX), a selective oestrogen receptor modulator, has low oral bioavailability (<2%) in humans due to its poor aqueous solubility and extensive first-pass metabolism in gut. In this study, we optimised the method of preparation for poly (ε-caprolactone) (PCL) based nanocapsules of RLX by double emulsion method (w/o/w). A hybrid design approach, Plackett-Burman design followed by rotatable central composite design, was used to arrive at the optimised formulation. The optimised formulation was subjected to in vitro and in vivo evaluation. RLX loaded nanocapsules were spherical in shape with particle size less than 200 nm and high encapsulation efficiency (>80%). RLX-loaded nanocapsules showed 2.1-fold increase in oral bioavailability compared to free RLX. IV pharmacokinetic studies indicated that RLX loaded into nanocapsule had significantly low clearance in comparison with free RLX. Designed nanocapsules showed promise as delivery systems to enhance oral bioavailability and in reducing clearance of raloxifene.

Anatomical location and redistribution of G protein-coupled estrogen receptor-1 during the estrus cycle in mouse kidney and specific binding to estrogens but not aldosterone

Prior studies have linked renoprotective effects of estrogens to G-protein-coupled estrogen receptor-1 (GPER-1) and suggest that aldosterone may also activate GPER-1. Here, the role of GPER-1 in murine renal tissue was further evaluated by examining its anatomical distribution, subcellular distribution and steroid binding specificity. Dual immunofluorescent staining using position-specific markers showed that GPER-1 immunoreactivity primarily resides in distal convoluted tubules and the Loop of Henle (stained with Tamm-Horsfall Protein-1). Lower GPER-1 expression was observed in proximal convoluted tubules marked with megalin, and GPER-1 was not detected in collecting ducts. Plasma membrane fractions prepared from whole kidney tissue or HEK293 cells expressing recombinant human GPER-1 (HEK-GPER-1) displayed high-affinity, specific [(3)H]-17β-estradiol ([(3)H]-E2) binding, but no specific [(3)H]-aldosterone binding. In contrast, cytosolic preparations exhibited specific binding to [(3)H]-aldosterone but not to [(3)H]-E2, consistent with the subcellular distribution of GPER-1 and mineralocorticoid receptor (MR) in these preparations. Aldosterone and MR antagonists, spironolactone and eplerenone, failed to compete for specific [(3)H]-E2 binding to membranes of HEK-GPER-1 cells. Furthermore, aldosterone did not increase [(35)S]-GTP-γS binding to membranes of HEK-GPER-1 cells, indicating that it is not involved in G protein signaling mediated through GPER-1. During the secretory phases of the estrus cycle, GPER-1 is upregulated on cortical epithelia and localized to the basolateral surface during proestrus and redistributed intracellularly during estrus. GPER-1 is down-modulated during luteal phases of the estrus cycle with significantly less receptor on the surface of renal epithelia. Our results demonstrate that GPER-1 is associated with specific estrogen binding and not aldosterone binding and that GPER-1 expression is modulated during the estrus cycle which may suggest a physiological role for GPER-1 in the kidney during reproduction.

A double-blind, randomized, ascending, multiple-dose study of bazedoxifene in healthy postmenopausal women

Bazedoxifene is a novel selective estrogen receptor modulator in clinical development for the prevention and treatment of postmenopausal osteoporosis. This phase 1, double-blind, randomized, placebo-controlled study (N = 107) of healthy postmenopausal women examined the pharmacokinetics and safety/tolerability profile of multiple doses of bazedoxifene (1, 2.5, 5, 10, 20, 40, and 80 mg) administered orally once daily for 30 days. Bazedoxifene demonstrated a half-life of 25 to 30 hours, reached steady state within 7 days, and exhibited linear pharmacokinetics over a dose range of 5-80 mg. Fibrinogen levels decreased with bazedoxifene doses of 5 mg and greater; these changes were significant for bazedoxifene 20, 40, and 80 mg (P ≤ .05 vs placebo), but were not dose dependent. Bazedoxifene was associated with increased levels of sex hormone-binding globulin, thyroxine-binding globulin, and cortisol-binding globulin (CBG); only increases in the levels of CBG appeared to be dose related. Bazedoxifene was safe and well tolerated within the tested dose range. Bazedoxifene showed no differences from placebo in adverse event reports, vital sign measurements, or electrocardiogram findings.

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

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

CB1 and CB2 receptors are novel molecular targets for Tamoxifen and 4OH-Tamoxifen

Tamoxifen (Tam) is classified as a selective estrogen receptor modulator (SERM) and is used for treatment of patients with ER-positive breast cancer. However, it has been shown that Tam and its cytochrome P450-generated metabolite 4-hydroxy-Tam (4OH-Tam) also exhibit cytotoxic effects in ER-negative breast cancer cells. These observations suggest that Tam and 4OH-Tam can produce cytotoxicity via estrogen receptor (ER)-independent mechanism(s) of action. The molecular targets responsible for the ER-independent effects of Tam and its derivatives are poorly understood. Interestingly, similar to Tam and 4OH-Tam, cannabinoids have also been shown to exhibit anti-proliferative and apoptotic effects in ER-negative breast cancer cells, and estrogen can regulate expression levels of cannabinoid receptors (CBRs). Therefore, this study investigated whether CBRs might serve as novel molecular targets for Tam and 4OH-Tam. We report that both compounds bind to CB1 and CB2Rs with moderate affinity (0.9-3 μM). Furthermore, Tam and 4OH-Tam exhibit inverse activity at CB1 and CB2Rs in membrane preparations, reducing basal G-protein activity. Tam and 4OH-Tam also act as CB1/CB2R-inverse agonists to regulate the downstream intracellular effector adenylyl cyclase in intact cells, producing concentration-dependent increases in intracellular cAMP. These results suggest that CBRs are molecular targets for Tam and 4OH-Tam and may contribute to the ER-independent cytotoxic effects reported for these drugs. Importantly, these findings also indicate that Tam and 4OH-Tam might be used as structural scaffolds for development of novel, efficacious, non-toxic cancer drugs acting via CB1 and/or CB2Rs.

Loss of androgen receptor promotes adipogenesis but suppresses osteogenesis in bone marrow stromal cells

Gender differences have been described in osteoporosis with females having a higher risk of osteoporosis than males. The differentiation of bone marrow stromal cells (BMSCs) into bone or fat is a critical step for osteoporosis. Here we demonstrated that loss of the androgen receptor (AR) in BMSCs suppressed osteogenesis but promoted adipogenesis. The mechanism dissection studies revealed that AR deficiency suppressed osteogenesis-related genes to inhibit osteoblast differentiation from BMSCs. Knockout of AR promoted adipogenesis of BMSCs via Akt activation through IGFBP3-mediated IGF signaling, and the 5' promoter assay and chromatin immunoprecipitation assays further proved that AR could modulate IGFBP3 expression at the transcriptional level. Finally, addition of IGF inhibitors successfully masked the AR deficiency-induced Akt activation, and inhibitions of Akt, IGF1, and IGF2 pathways reversed the AR depletion effects on the adipogenesis process. These results suggested that AR-mediated changes in IGFBP3 might modulate the IGF-Akt axis to regulate adipogenesis in BMSCs.

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Pharmacokinetic evaluation of toremifene and its clinical implications for the treatment of osteoporosis

INTRODUCTION

Toremifene is a triphenylethylene selective estrogen receptor modulator (SERM) that differs from tamoxifen in a single chloride ion addition on a side chain, resulting in a potentially more favorable toxicity profile.

AREAS COVERED

This article reviews the pharmacokinetics of toremifene and its potential use for the treatment of osteoporosis. This article was based on articles found through a literature search containing the terms 'toremifene' and 'SERMs.'

EXPERT OPINION

Toremifene can be administered orally with an excellent bioavailability. The overall pharmacokinetic profile is remarkably similar to tamoxifen. Toremifene is highly metabolized in the liver and is eliminated primarily in the feces following enterohepatic circulation. Some of its metabolites retain biological activity. This SERM was approved by the FDA for the treatment of estrogen receptor-positive metastatic breast cancer and is under investigation for its potential skeletal benefits in men on androgen deprivation therapy. Despite the positive preclinical and clinical evidences for the prevention of bone loss and fractures, the chemopreventive effect on prostate cancer remains to be confirmed and an increased risk of venous thromboembolism was evidenced in a large Phase III trial. Thus, additional data are required to establish the full clinical profile of this compound and its potential advantages over antiresorptive agents commonly in use for the treatment of osteoporosis.

Validation of the adherence evaluation of osteoporosis treatment (ADEOS) questionnaire for osteoporotic post-menopausal women

SUMMARY

We developed and validated a specific 12-item questionnaire to evaluate adherence to oral antiresorptive medication by post-menopausal osteoporotic women in everyday practice. Over the following 9 months, an index of ≤16 was associated with an increase in the risk of treatment discontinuation of 1.69 and of 2.10 for new patients who had started treatment within the previous year.

INTRODUCTION

Adherence to medication in osteoporosis is poor. The goal of this study was to develop and validate a disease-specific questionnaire to evaluate adherence to treatment of women with post-menopausal osteoporosis taking oral antiresorptive medication.

METHODS

A prototype adherence questionnaire with 45 items developed from patient interview, literature review, and physician opinion was evaluated in a sample of 350 post-menopausal women with osteoporosis treated in primary care. Item responses were matched against scores on the Morisky Medication Adherence Scale (MMAS). The most discriminant items were retained in the final questionnaire. Concurrent and predictive validity were assessed.

RESULTS

Twelve items were associated with MMAS score at a probability level of 0.05. These were retained in the final questionnaire which provided an adherence index ranging from 0 to 22. An index of ≥20 was associated with a high probability of persistence and an index ≤ 16 with a high probability of treatment discontinuation in the following 9 months.

CONCLUSIONS

The ADEOS-12 is a simple patient-reported measure to determine adherence to osteoporosis treatments with good concurrent and discriminant validity. This is the first disease-specific adherence measure to have been developed for osteoporosis.

Bazedoxifene: a review of its use in the treatment of postmenopausal osteoporosis

Bazedoxifene (Conbriza®, Viviant®) is the first third-generation selective estrogen receptor modulator (SERM) and it is approved for the treatment of postmenopausal osteoporosis in the EU and Japan. Bazedoxifene contains an indole-based core binding domain that binds with high affinity to estrogen receptors and exhibits favourable effects on bone and lipid profiles, with no clinically relevant endometrial or breast stimulation. Oral bazedoxifene once daily reduced the incidence of new vertebral fractures in patients with postmenopausal osteoporosis in a large, well designed trial of 3 years' duration; both bazedoxifene and raloxifene were significantly more effective than placebo. Neither bazedoxifene nor raloxifene reduced the incidence of nonvertebral fractures in the overall study population; however, bazedoxifene, but not raloxifene, reduced the rate of nonvertebral fractures in high-risk patients. Moreover, data from patients who continued to receive the drug during a 2-year extension phase of this trial indicate that bazedoxifene continues to provide protection against new vertebral fractures for up to 5 years. Bazedoxifene also increases bone mineral density and reduces the levels of bone turnover markers. Bazedoxifene was generally well tolerated and did not detrimentally affect the reproductive tract or breast tissue in clinical trials, thereby demonstrating a favourable risk-benefit profile. A pharmacoeconomic analysis conducted from an EU perspective predicted bazedoxifene to be cost effective in some EU countries. Therefore, bazedoxifene presents another useful option for the treatment of postmenopausal osteoporosis, especially in those at high risk for osteoporotic fracture.

Diastereoselective Friedel-Crafts alkylation of hydronaphthalenes

An efficient and versatile synthesis of chiral tetralins has been developed using both inter- and intramolecular Friedel-Crafts alkylation as a key step. The readily available hydronaphthalene substrates were prepared via a highly enantioselective metal-catalyzed ring opening of meso-oxabicyclic alkenes followed by hydrogenation. A wide variety of complex tetracyclic compounds have been isolated with high levels of regio-, diastereo-, and enantioselectivity.

Minimal trauma fractures: lifting the specter of misconduct by identifying risk factors and planning for prevention

Minimal trauma fractures are an unfortunate, yet not uncommon, event for frail elderly individuals in long term care facilities. These fractures result in significant morbidity including pain and loss of function along with significantly increased mortality. Further concern exists for the medico-legal issues raised after a minimal trauma fracture is discovered. The controversy at hand is whether such fractures are primarily the result of inadequate, careless, or abusive care practices. We build a case to the contrary. Although the data regarding this condition are limited, there exists a reasonable evidence base to identify an at-risk patient population. We present a representative case and subsequent literature review of minimal trauma fractures to illustrate the condition, including risk factors, mode of presentation, and patient outcomes. No direct research has been conducted on the pathophysiology of these fractures. Extrapolating from other similar conditions and likely associated comorbid illnesses, we explore possible physiologic explanations for their occurrence. Again, no direct investigation into prevention or treatment of minimal trauma fractures has been published. Instead, we consider a variety of pharmacologic and nonpharmacologic interventions that may modify the risk for minimal trauma fractures considering the previously identified risk factors and probable pathophysiologic changes leading to fracture development. We propose that reducing minimal trauma fractures in the frail elderly nursing home population will require careful staff education, close attention to identify at-risk patients, and implementation of select interventions aimed at preventing such fractures.

Antiosteoporotic compounds from seeds of Cuscuta chinensis

ETHNOPHARMACOLOGICAL RELEVANCE

The seeds of Cuscuta chinensis (Tu-Si-Zi, TSZ) have long been used for the treatment of osteoporosis in China and some Asian countries. The compounds in TSZ responsible for the antiosteoporotic activity are still poorly understood.

AIM OF THE STUDY

The present study was designed to investigate the osteogenic compounds in TSZ, and to evaluate their antiosteoporotic effects in osteoblastic cells.

MATERIALS AND METHODS

Osteoblast-like UMR-106 cells were used for bioactivity-guided isolation of the active compounds. The activity of alkaline phosphatase (ALP) in UMR-106 cells was measured by p-nitrophenyl sodium phosphate assay. The proliferation of UMR-106 cells was assayed by Alamar-Blue method. Estrogenic activity of the extracts and isolated compounds was evaluated by activation of estrogen response element (ERE) luciferase reporter expression in HeLa cells co-transfected with human estrogen receptor subtypes (ERα or ERβ) expression vectors and 5×ERE luciferase reporter plasmid. Antiestrogenic activity of the extracts and isolated compounds were evaluated by activation of activator protein-1 (AP-1) luciferase reporter expression in HeLa cells co-transfected with human estrogen receptor subtypes (ERα or ERβ) expression vectors and 6×AP-1 luciferase reporter plasmid.

RESULTS

ALP-guided fractionation led to the isolation of five known flavonoids, quercetin, kaempferol, isorhamnetin, hyperoside and astragalin from the crude ethanolic extract of TSZ. Further study showed that kaempferol and hyperoside significantly increased the ALP activity in UMR-106 cells. Astragalin promoted the proliferation of UMR-106 cells whereas other compounds had no such effect. The isolated compounds showed estrogenic activity but quercetin, kaempferol and isorhamnetin showed more potent ERβ agonist activity. However, compared with their ER agonist activity, only quercetin and kaempferol showed potent ER antagonist activity by activating ERα/β-mediated AP-1 reporter expression.

CONCLUSIONS

Our findings validated the clinical use of TSZ in the treatment of osteoporosis, and demonstrated that kaempferol and hyperoside are the active compounds in TSZ for the osteogenic effect.

LC, a novel estrone-rhein hybrid compound, concurrently stimulates osteoprotegerin and inhibits receptor activator of NF-κB ligand (RANKL) and interleukin-6 production by human osteoblastic cells

Estrogen analogues are promising drugs for postmenopausal osteoporosis, but because of their possible side effects such as increased risk of cancer, estrogens which exert their estrogenic effects selectively on bone are desired. It has been shown that rhein inhibits osteoclast formation and bone resorption activity and has an antitumor role in several types of cancers. Having found that rhein had high affinity for the bone mineral, we synthesized estrone-rhein hybrid compounds and confirmed that one of these hybrid compounds, LC, exhibited a selective profile in the bone and prevented bone loss but had no effect on endometrium growth in ovariectomized rats. However, the mechanisms underlying its actions on human bone cells have not been well defined. Here we show that LC concurrently stimulates osteoprotegerin (OPG) and inhibits receptor activator of nuclear factor-κB ligand (RANKL) and Interleukin-6 (IL-6) production by human osteoblastic MG-63 cells containing two estrogen receptor (ER) isotypes. Treatment with the ER antagonist ICI 182,780 abrogates the above actions of LC on osteoblast-derived cells. Using small interfering double-stranded RNAs (siRNA) technology, we further demonstrate that the effects of LC on IL-6 production are mediated by both ERα and ERβ but those on OPG and RANKL expression primarily by ERα. Furthermore, we also demonstrate that LC functions at least partially through activation of the classic estrogen response element (ERE) pathway as well as Ras/MEK/ERK and PI3K/Akt signaling. The effect of LC on bone is due to not only its estrogenic activity but also action of its rhein moiety. Also, this compound shows much weaker effect on breast epithelial cell growth than that of estrone. Therefore, using rhein for conjugating compounds is a promising method of effectively targeting estrogens to the bone.

Anti-breast cancer potential of SS5020, a novel benzopyran antiestrogen

Treatment with tamoxifen (TAM) increases the risk of developing endometrial cancer in women. The carcinogenic effect is thought to involve initiation and/or promotion resulting from DNA damage induced by TAM as well as its estrogenic action. To minimize this serious side-effect while increasing the anti-breast cancer potential, a new benzopyran antiestrogen, 2E-3-{4-[(7-hydroxy-2-oxo-3-phenyl-2H-chromen-4-yl)-methyl]-phenyl}-acrylic acid (SS5020), was synthesized. Unlike TAM, SS5020 exhibits no genotoxic activity to damage DNA. Furthermore, SS5020 does not present significant uterotrophic potential in rats; in contrast, the structurally related compounds, TAM, toremifene, raloxifene (RAL) and SP500263 all have uterotrophic activity. At the human equivalent molar dose of TAM (0.33 or 1.0 mg/kg), SS5020 had much stronger antitumor potential than those same antiestrogens against 7,12-dimethylbenz(a)anthracene-induced mammary carcinoma in rats. The growth of human MCF-7 breast cancer xenograft implanted into athymic nude mice was also effectively suppressed by SS5020. SS5020, lacking genotoxic and estrogenic actions, could be a safer and stronger antiestrogen alternative to TAM and RAL for breast cancer therapy and prevention.

Arzoxifene for prevention of fractures and invasive breast cancer in postmenopausal women

Arzoxifene is a selective estrogen receptor modulator (SERM) that has been shown to be more potent in preclinical testing than currently available agents. Its effects on clinical outcomes are not known. In a randomized, blinded trial, women aged 60 to 85 years with osteoporosis, defined as a femoral neck or lumbar spine bone mineral density T-score of -2.5 or less or a vertebral fracture, and women with low bone mass, defined as a bone density T-score of -1.0 or less and above -2.5, were assigned to arzoxifene 20 mg or placebo daily. The primary endpoints were new vertebral fracture in those with osteoporosis and invasive breast cancer in the overall population. After 3 years, the cumulative incidence of vertebral fractures in patients with osteoporosis was 2.3% lower in the arzoxifene group than in the placebo group, a 41% relative risk reduction [95% confidence interval (CI) 0.45-0.77, p < .001]. In the overall population, the cumulative incidence of invasive breast cancer over 4 years was reduced by 1.3%, with a 56% relative reduction in risk (hazard ratio = 0.44, 95% CI 0.26-0.76, p < .001); there was no significant decrease in nonvertebral fracture risk. Arzoxifene increased the cumulative incidence of venous thromboembolic events by 0.7%, with a 2.3-fold relative increase (95% CI 1.5-3.7). Like other SERMs, arzoxifene decreased vertebral fractures and invasive breast cancer while the risk of venous thromboembolic events increased.