Raloxifene for older women: a review of the literature

Modulation of Estrogen Receptor Alpha (ERα) and Tumor Suppressor Gene BRCA1 in Breast Cancer Cells by Bazedoxifene Acetate (BZA)

Selective estrogen receptor modulators (SERMs) are steroid analogs with dual functionality, acting as partial estrogen receptor agonists to preserve postmenopausal bone density and as estrogen receptor antagonists in breast tissue. Bazedoxifene acetate (BZA) is an FDA-approved, third-generation SERM used in the treatment of osteoporosis in women. It demonstrates potential as a therapeutic option for breast cancer patients undergoing endocrine therapy. Our study aimed to assess BZA's effects on Estrogen Receptor Alpha (ERα) and tumor suppressor gene BRCA1 in T-47D and MCF-7 breast cancer cells, using Western blots, cellular viability, apoptosis assays, and RT-qPCR. Cells were cultured in 5% charcoal-stripped fetal bovine serum for six days to deplete endogenous steroids. Following a 24 h exposure to 2 µM BZA (optimal concentration determined from 1 nM-2 µM studies), Western blot analyses revealed reduced ERα and BRCA1 protein levels in both cell lines. ERα decreased by 48-63% and BRCA1 by 61-64%, indicating sensitivity to antiestrogens. Cytolocalization of ERα and BRCA1 remained unchanged after BZA and 17-β-estradiol (E2) treatment. ESR1 mRNA expression correlated with Western blot findings. Image cytometric analysis using the stain, propidium iodide, detected decreased cellular proliferation in T-47D and MCF-7 cells following a 6-day treatment ranging from 1 nM to 2 µM BZA. BZA treatment alone led to a tenfold reduction in cellular proliferation compared to estrogen-treated cells, suggesting antiproliferative effects. Understanding BZA's modulation of BRCA1 and ERα, along with their mechanistic interactions, is vital for comprehending its impact on breast cancer tumor suppressors and hormone receptors.

Immune mechanism of low bone mineral density caused by ankylosing spondylitis based on bioinformatics and machine learning

Background and Objective: This study aims to find the key immune genes and mechanisms of low bone mineral density (LBMD) in ankylosing spondylitis (AS) patients. Methods: AS and LBMD datasets were downloaded from the GEO database, and differential expression gene analysis was performed to obtain DEGs. Immune-related genes (IRGs) were obtained from ImmPort. Overlapping DEGs and IRGs got I-DEGs. Pearson coefficients were used to calculate DEGs and IRGs correlations in the AS and LBMD datasets. Louvain community discovery was used to cluster the co-expression network to get gene modules. The module most related to the immune module was defined as the key module. Metascape was used for enrichment analysis of key modules. Further, I-DEGs with the same trend in AS and LBMD were considered key I-DEGs. Multiple machine learning methods were used to construct diagnostic models based on key I-DEGs. IID database was used to find the context of I-DEGs, especially in the skeletal system. Gene-biological process and gene-pathway networks were constructed based on key I-DEGs. In addition, immune infiltration was analyzed on the AS dataset using the CIBERSORT algorithm. Results: A total of 19 genes were identified I-DEGs, of which IFNAR1, PIK3CG, PTGER2, TNF, and CCL3 were considered the key I-DEGs. These key I-DEGs had a good relationship with the hub genes of key modules. Multiple machine learning showed that key I-DEGs, as a signature, had an excellent diagnostic performance in both AS and LBMD, and the SVM model had the highest AUC value. Key I-DEGs were closely linked through bridge genes, especially in the skeletal system. Pathway analysis showed that PIK3CG, IFNAR1, CCL3, and TNF participated in NETs formation through pathways such as the MAPK signaling pathway. Immune infiltration analysis showed neutrophils had the most significant differences between case and control groups and a good correlation with key I-DEG. Conclusion: The key I-DEGs, TNF, CCL3, PIK3CG, PTGER2, and IFNAR1, can be utilized as biomarkers to determine the risk of LBMD in AS patients. They may affect neutrophil infiltration and NETs formation to influence the bone remodeling process in AS.

Contemporaneous Insufficiency Fractures of Bilateral Femoral Necks in an Older Patient Taking Bisphosphonate: A Case Report and Literature Review

We report, to the best of our knowledge, the first case of simultaneous insufficiency fracture of the bilateral femoral neck in an older patient taking bisphosphonate. Femoral neck fractures frequently occur in older individuals because of traumatic incidents, such as a fall. A 74-year-old woman with osteoporosis was taking raloxifene hydrochloride and bisphosphonate for approximately 5 and 3 years, respectively. Despite no history of falls or any other traumatic incidence, the patient reported cooccurrence of pain on both sides of the hip. Imaging revealed bilateral femoral neck fractures. Bipolar hemiarthroplasty and internal fixation were conducted on the right and left hips, respectively. At 6 months postoperatively, the patient reported gradual disappearance of left hip pain, and a radiograph revealed that the fracture had healed. Overall, clinical and histological findings suggested an atypical fracture, thereby proving that this type of fracture can occur in areas other than the femoral shaft.

Combination therapy of calcitriol inhibits the proliferation of breast cancer cells: new concept of nonclassical function of calcitriol

OBJECTIVES

To evaluate the anticancer effects of calcitriol and cholecalciferol against different cell lines of breast cancer in monotherapy settings and in combination with raloxifene.

METHODS

The antiproliferative, anti-migratory, and apoptotic induction effects were assessed by MTT, wound healing, and flow cytometry assays, respectively.

RESULTS

Calcitriol and cholecalciferol exhibited antiproliferative effects against T47D, MCF-7, and MDA-MB-231 in a time and concentration-dependent manner. The IC₅₀ values of calcitriol were in the range of 0.05-0.25 μM while that for cholecalciferol were in the range of 3-100 μM. Furthermore, the results showed that calcitriol and cholecalciferol exhibited anti-migratory effects on MDA-MB-231, an apoptotic induction effect on MCF-7 cells, and a synergistic effect when combined with raloxifene.

CONCLUSIONS

Calcitriol and cholecalciferol exhibited anticancer effects and may be used as chemosensitizers.

Estrogenic hormones receptors in Alzheimer's disease

Estrogens are hormones that play a critical role during development and growth for the adequate functioning of the reproductive system of women, as well as for maintaining bones, metabolism, and cognition. During menopause, the levels of estrogens are decreased, altering their signaling mediated by their intracellular receptors such as estrogen receptor alpha and beta (ERα and ERβ), and G protein-coupled estrogen receptor (GPER). In the brain, the reduction of molecular pathways mediated by estrogenic receptors seems to favor the progression of Alzheimer's disease (AD) in postmenopausal women. In this review, we investigate the participation of estrogen receptors in AD in women during aging.

Formulation and evaluation of raloxifene hydrochloride dry emulsion tablet using solid carrier adsorption technique

Aim: The present study focused on the development of a dry emulsion tablet of raloxifene hydrochloride (RXF) using a solid carrier adsorption technique to enhance oral bioavailability. Methods: An oil-in-water emulsion was formulated and converted into dry powder using HPMC K4M plus Aerosil 200, then compressed into tablets. Results: The prepared emulsion was evaluated for globule size, drug content and zeta potential. In vitro release study revealed significantly higher release from emulsion. The prepared tablets possessed acceptable hardness, friability, weight variation, disintegration time, thickness, etc. In vivo pharmacokinetic studies indicated a more than sevenfold increase in oral bioavailability. Stability studies indicated good physical and chemical stability of the developed formulation. Conclusion: The authors successfully formulated dry emulsion tablets with enhanced oral bioavailability.

Recent development of drugs for osteoporosis and anti-cancer agents: a patent analysis

Osteoporosis and cancer are becoming a major public health problem. Some studies have shown that osteoporosis drugs may have anti-cancer effects. To better understand the relationship between drugs for osteoporosis and antineoplastic agents, and to better demonstrate recent developments for patents concerning drugs for osteoporosis, we conducted an analysis of US patents. The results indicated that there was a good correlation between agents for osteoporosis and antineoplastic agents, which indicated that numerous anti-osteoporosis agents displayed antineoplastic activities. Our study was the first one to provide new evidence, through comprehensive analysis, for a correlation between anti-osteoporosis agents and anticancer agents. The present study may open new avenues for developing anticancer drugs and expanding the application role of anti-osteoporosis agents.

Raloxifene Prevents Early Periprosthetic Bone Loss for Postmenopausal Women after Uncemented Total Hip Arthroplasty: A Randomized Placebo-Controlled Clinical Trial

OBJECTIVE

To examine the results of raloxifene for prevention of periprosthetic bone loss around the femoral stem in patients undergoing total hip arthroplasty (THA).

METHODS

Between January 2015 and May 2017, 240 female patients between 55 and 80 years underwent primary THA and were randomly allocated to receive 60 mg raloxifene hydrochloride per day (treatment group, TG, n = 120) or placebo (control group, CG, n = 120) orally at bedtime using computer-generated randomization sequence generation. Baseline data, the Western Ontario McMaster Universities Osteoarthritis Index (WOMAC), women's quality of life (QoL) score, bone mineral density (BMD) around the prosthesis, and adverse events were compared between the two groups. The measuring range of BMD around the prosthesis was divided into seven regions of interest (ROI). The sample size was calculated to detect a mean difference in BMD of 0.15 g/cm² with a standard deviation (SD) of 0.3. The error was set at 0.05 and the power level at 90% with additional compensation for a possible dropout rate of 20%.

RESULTS

A total of 240 participants in the study up to 24 months after THA. There were no significant differences in the mean BMD of all the zones between groups before surgery (all P > 0.05). However, there were significant differences in the BMD of Gruen zones 4 and 7 between groups at 6 months postoperatively (both P < 0.05); there were significant differences in Gruen zones 1, 4, 6, and 7 at 12 months postoperatively (all P < 0.01); there were significant differences in Gruen zones 1, 2, 4, 6, and 7 at 24 months postoperatively (all P < 0.001). Patients taking raloxifene reported higher QoL scores, with better improvement in BMD in all areas except in zones 3 and 5 compared with the control group. There were no significant differences in WOMAC pain (P = 0.4045), WOMAC function (P = 0.4456) and women's QoL scores (P = 0.5983) between groups before surgery. However, WOMAC pain, WOMAC function and women's QoL score in the treatment group were significantly better at all time points (all P < 0.05). Patients in the treatment group showed no increased adverse events, including cardiac events, stroke, venous thromboembolism, and gynecological cancer (all P > 0.05), but did show decreased odds of breast cancer in comparison with those using a placebo (P = 0.0437).

CONCLUSION

Raloxifene can help inhibit bone loss around the prosthesis and improve the QoL of postmenopausal women after THA with no increased adverse events, and can even decrease the odds of breast cancer.

Pharmacotherapeutic approaches to treating depression during the perimenopause

Introduction: Although postnatal depression is now well recognized, there is also a risk of depressive symptoms during perimenopause. The mechanisms underlying perimenopausal depression are still poorly understood; however, there are available treatment options. Areas covered: This review describes: the current pharmacotherapeutic approaches for perimenopausal depression, their strengths and weakness, and provides recommendations on how current treatment can be improved in the future. An electronic search identified specific guidelines for the treatment of perimenopausal depression released in 2018, as well as recent clinical studies on the subject. Expert opinion: The 2018 guidelines recommend selective serotonin reuptake inhibitors (SSRIs) and serotonin and noradrenaline reuptake inhibitors (SNRIs) as front-line medications for perimenopausal depression, but SSRIs and SNRIs are not always effective. The efficacy of estrogen in perimenopausal depression is well documented, but estrogen is not FDA-approved to treat mood disturbances in perimenopausal women. Clinical practice guidelines currently recommend to restrict hormone therapy to the symptomatic treatment of menopause (not for the prevention of chronic diseases). Research with new estrogenic compounds is under way to improve their benefit/risk ratio in perimenopausal depression.

Peptide Conjugates with Small Molecules Designed to Enhance Efficacy and Safety

Peptides constitute molecular diversity with unique molecular mechanisms of action that are proven indispensable in the management of many human diseases, but of only a mere fraction relative to more traditional small molecule-based medicines. The integration of these two therapeutic modalities offers the potential to enhance and broaden pharmacology while minimizing dose-dependent toxicology. This review summarizes numerous advances in drug design, synthesis and development that provide direction for next-generation research endeavors in this field. Medicinal studies in this area have largely focused upon the application of peptides to selectively enhance small molecule cytotoxicity to more effectively treat multiple oncologic diseases. To a lesser and steadily emerging extent peptides are being therapeutically employed to complement and diversify the pharmacology of small molecule drugs in diseases other than just cancer. No matter the disease, the purpose of the molecular integration remains constant and it is to achieve superior therapeutic outcomes with diminished adverse effects. We review linker technology and conjugation chemistries that have enabled integrated and targeted pharmacology with controlled release. Finally, we offer our perspective on opportunities and obstacles in the field.

27-Hydroxycholesterol Is an Estrogen Receptor β-Selective Negative Allosteric Modifier of 17β-Estradiol Binding

Estrogens bind to two nuclear estrogen receptor (ER) subtypes, ERα and ERβ, which are expressed in differing amounts in various tissues. The endogenous estrogen, 17β-estradiol (E2), binds to both subtypes with nearly equal affinity and is the prototypical agonist. Selective estrogen receptor modulators (SERMs) may bind to both subtypes with equivalent affinities but have agonist activities in some tissues while having antagonist activities in others. In the present study, we demonstrate that the first reported endogenous SERM, 27-hydroxycholesterol (27-OHC), binds preferentially (>100-fold) to ERβ over ERα. Furthermore, 27-OHC is not able to fully compete with E2 binding, suggesting the two may bind at different sites. We provide an allosteric ternary complex model for the simultaneous binding of 27-OHC and E2 to ERβ, which accurately describes the binding data we have observed. We conclude that 27-OHC is a negative allosteric modifier of E2 binding, with an inhibitor constantof 50 nM and cooperativity factor (α) of 0.036. We also propose an in silico three-dimensional model of the simultaneous binding to guide future experiments. Further study of this unique binding model may allow for the discovery of novel ERβ-selective ligands and potentially explain the lack of effectiveness of ERβ-selective agonists in humans vs preclinical models.

Raloxifene Lowers Plasma Lipoprotein(a) Concentrations: a Systematic Review and Meta-analysis of Randomized Placebo-Controlled Trials

BACKGROUND AND AIMS

Lipoprotein(a) (Lp(a)) is a proatherogenic plasma lipoprotein and an independent risk factor for atherosclerotic cardiovascular disease. We investigated the effects of raloxifene, selective estrogen receptor modulator, on circulating Lp(a) levels in postmenopausal women using a systematic review and meta-analysis of randomized controlled trials (RCTs).

METHODS

To identify relevant studies, electronic databases (PUBMED, Scopus, Web of Science, and Google Scholar) were searched by up to May 2015 to find controlled trials exploring the effects of oral raloxifene treatment on plasma Lp(a) levels in postmenopausal women. A random-effects model and generic inverse variance method were used for quantitative data synthesis.

RESULTS

Overall, seven eligible RCTs with ten treatment arms were included in this meta-analysis. Meta-analysis suggested a significant reduction of Lp(a) levels after treatment with raloxifene (standardized mean difference (SMD) -0.42; 95% CI -0.65, -0.19; p < 0.001), which may be considered as a medium effect size. When the studies were categorized according to the administered dose, there was a significant effect in both subsets of studies with administered doses ≤60 mg/day (SMD -0.43; 95% CI -0.73, -0.13; p = 0.004) and >60 mg/day (SMD -0.36; 95% CI -0.68, -0.05; p = 0.025). No significant association between the changes in plasma concentrations of Lp(a) with dose and baseline Lp(a) levels was found in the random-effects meta-regression analysis. However, a significant inverse association was observed between the Lp(a)-lowering effect of raloxifene and duration of treatment (p = 0.001).

CONCLUSIONS

Results of the present meta-analysis showed a reduction in plasma Lp(a) concentrations of postmenopausal women with oral raloxifene treatment.

The Selective Estrogen Receptor Modulator Raloxifene Inhibits Neutrophil Extracellular Trap Formation

Raloxifene is a selective estrogen receptor modulator typically prescribed for the prevention/treatment of osteoporosis in postmenopausal women. Although raloxifene is known to have anti-inflammatory properties, its effects on human neutrophils, the primary phagocytic leukocytes of the immune system, remain poorly understood. Here, through a screen of pharmacologically active small molecules, we find that raloxifene prevents neutrophil cell death in response to the classical activator phorbol 12-myristate 13-acetate (PMA), a compound known to induce formation of DNA-based neutrophil extracellular traps (NETs). Inhibition of PMA-induced NET production by raloxifene was confirmed using quantitative and imaging-based assays. Human neutrophils from both male and female donors express the nuclear estrogen receptors ERα and ERβ, known targets of raloxifene. Similar to raloxifene, selective antagonists of these receptors inhibit PMA-induced NET production. Furthermore, raloxifene inhibited PMA-induced ERK phosphorylation, but not reactive oxygen species production, pathways known to be key modulators of NET production. Finally, we found that raloxifene inhibited PMA-induced, NET-based killing of the leading human bacterial pathogen, methicillin-resistant Staphylococcus aureus. Our results reveal that raloxifene is a potent modulator of neutrophil function and NET production.

Raloxifene glucuronidation in liver and intestinal microsomes of humans and monkeys: contribution of UGT1A1, UGT1A8 and UGT1A9

1. Raloxifene is an antiestrogen that has been marketed for the treatment of osteoporosis, and is metabolized into 6- and 4'-glucuronides by UDP-glucuronosyltransferase (UGT) enzymes. In this study, the in vitro glucuronidation of raloxifene in humans and monkeys was examined using liver and intestinal microsomes and recombinant UGT enzymes (UGT1A1, UGT1A8 and UGT1A9). 2. Although the K(m) and CL(int) values for the 6-glucuronidation of liver and intestinal microsomes were similar between humans and monkeys, and species differences in Vmax values (liver microsomes, humans > monkeys; intestinal microsomes, humans < monkeys) were observed, no significant differences were noted in the K(m) or S50, Vmax and CL(int) or CLmax values for the 4'-glucuronidation of liver and intestinal microsomes between humans and monkeys. 3. The activities of 6-glucuronidation in recombinant UGT enzymes were UGT1A1 > UGT1A8 >UGT1A9 for humans, and UGT1A8 > UGT1A1 > UGT1A9 for monkeys. The activities of 4'-glucuronidation were UGT1A8 > UGT1A1 > UGT1A9 in humans and monkeys. 4. These results demonstrated that the profiles for the hepatic and intestinal glucuronidation of raloxifene by microsomes were moderately different between humans and monkeys.

Raloxifene upregulated mesangial cell MMP-2 activity via ER-β through transcriptional regulation

Raloxifene, a second-generation selective estrogen receptor modulator, exerts estrogen-like effects in specific tissues. In this present study, we examined the effect of raloxifene on mesangial cell matrix metalloproteinase-2 (MMP-2) activity in streptozotocin-induced diabetic mice. Raloxifene increased the MMP-2 level in a dose-dependent and receptor-mediated manner. An antibody against estrogen receptor-β (ER-β) blocked the effect of raloxifene on MMP-2 expression, suggesting that the effect of raloxifene on MMP-2 activity was mediated by ER-β. In addition, the transcription factor AP-2, that plays an important role in MMP-2 gene transcription, was overexpressed under raloxifene simulation. The effect of MMP-2 was blocked by a selective inhibitor of the extracellular signal-regulated kinase/mitogen-activated protein kinase (ERK/MAPK) pathway, PD98059. Our results suggested that raloxifene-induced MMP-2 activity increases function through ERK/MAPK signaling via AP-2. In addition, we also found that the effect of raloxifene on MMP-2 expression was mediated via its binding to ER-β. However, at this stage of our investigation, (i) we could only show that both the binding to ER-β and the activation of the ERK/MAPK pathway impacted MMP-2 expression and (ii) we were unable to establish a relationship between ER-β binding and ERK/MAPK pathway activation.

Alendronate versus Raloxifene for Postmenopausal Women: A Meta-Analysis of Seven Head-to-Head Randomized Controlled Trials

Purpose. The aim of this study was to directly compare the efficacy and the safety of the two agents for postmenopausal women. Methods/Principal Findings. Electronic databases were searched for relevant articles that met our predefined inclusion criteria. Seven randomized controlled trials (RCTs) involving 4054 women were identified and included. Although Aln was more effective than Rlx in increasing bone mineral density (BMD), no statistical differences were observed in reducing the risk of neither vertebral fractures (P = 0.45) nor nonvertebral fractures (P = 0.87) up to two-year followup. Aln reduced the risk of vasomotor (P = 0.006) but increased the risk of diarrhea compared to Rlx (P = 0.01). Our subgroup analysis further indicated the difference between Aln and Rlx in fracture risk and was not materially altered by the administration pattern, the age. The weekly strategy of Aln would further reduce the upper gastrointestinal (GI) disorders and might gain more bone mass increment at lumbar spine compared to its daily treatment. Conclusion. There was no evidence of difference of fracture risk reduction between Aln and Rlx. In addition, age did not obviously influence their relative antifracture efficacy. For Aln the weekly strategy would further reduce the upper GI disorders and gain more bone mass increment compared to the daily treatment. During clinical decision making, the patients' adherence and the related side-effects associated with both drugs should also be taken into account.

[Pharmacologic treatment of osteoporosis--2011]

Osteoporosis affects approximately 9% of the population in Hungary resulting in about 100 000 osteoporotic fractures annually. Thirty-five percent of patients with hip fractures due to osteoporosis will die within 1 year. Direct costs of osteoporosis exceed 25 billion forints per year. Apparently, cost-effective reduction of bone loss and consequent fracture risk will add up to not only financial savings but improvement in quality of life, as well. A number of pharmacological modalities are available for this purpose. The mainstay of the treatment of osteoporosis is the bisphosphonate group that includes effective anti-resorptive compounds mitigating bone loss and fragility. The recently registered denosumab exhibits similar efficacy by neutralizing RANK ligand, however, marked differences can be observed between the two drug classes. Strontium has a unique mechanism of action by rebalancing bone turnover, and thus, providing an efficient treatment option for the not fast bone losers who are at high fracture risk. The purely anabolic teriparatide is available for the extremely severe osteoporotic patients and for those who do not respond to other types of therapy. Older treatment options such as hormone replacement therapy, raloxifene, tibolone or calcitonin may also have a restricted place in the management of osteoporosis.

The effects of selective estrogen receptor modulator treatment following hormone replacement therapy on elderly postmenopausal women with osteoporosis

OBJECTIVES

A comparison between the atheroprotective and osteoprotective effects of the selective estrogen receptor modulator (SERM) raloxifene and those of hormone replacement therapy (HRT) has not been made in elderly women.

METHODS

A randomized prospective controlled trial was performed in a cohort of 32 elderly Japanese women with osteoporosis receiving HRT (estriol plus medroxyprogesterone) for more than 1 year. In 16 randomly selected subjects, HRT was changed to raloxifene therapy (60mg/day, 71.4±3.4 years, SERM group). The other 16 patients were continued on HRT (71.8±2.9 years, HRT group). As a control group, 14 subjects were enrolled, did not take any medications and were age-matched to experimental patients (72.5±3.3 years, control group). Plasma lipids, TNFα, adiponectin, NO metabolites (NOx:NO2(-) and NO3(-)), cyclicGMP and bone-mineral density (BMD) were evaluated at baseline and at 26 and 52 weeks after enrollment.

RESULTS

SERM (Raloxifene) increased high-density-lipoprotein cholesterol levels and tended to decrease low-density-lipoprotein cholesterol levels (P=0.058) compared with baseline. Adiponectin, NOx and cGMP levels were significantly increased after 6 months compared with baseline or the HRT group. TNFα was decreased by raloxifene. In control subjects, no significant changes were observed in any of these markers. Bone-mineral density was higher at baseline in the raloxifene and HRT groups than in the control group, and BMD increased 12 months after baseline in the HRT and control group.

CONCLUSION

SERM improved BMD and endothelial function in elderly postmenopausal women with osteoporosis who had received HRT, and these effects were comparable to or slightly stronger than those of HRT. Changes in adiponectin and TNFα may underlie the improvements in endothelial function, such as NO signaling.

Cathepsin K inhibitors for osteoporosis and potential off-target effects

Cathepsin K is a highly potent collagenase and the predominant papain-like cysteine protease expressed in osteoclasts. Cathepsin K deficiencies in humans and mice have underlined the central role of this protease in bone resorption and, thus, have rendered the enzyme as an attractive target for anti-resorptive osteoporosis therapy. In the past decade, a lot of efforts have been made in developing highly potent, selective and orally applicable cathepsin K inhibitors. Some of these inhibitors have passed preclinical studies and are presently in clinical trials at different stages of advancement. The development of the inhibitors and preliminary results of the clinical trials revealed problems and lessons concerning the in situ specificity of the compounds and their tissue targeting. In this review, we briefly summarize the history of cathepsin K research and discuss the current development of cathepsin K inhibitors as novel anti-resorptives for the treatment of osteoporosis. We also discuss potential off-target effects of cathepsin K inhibition and alternative applications of cathepsin K inhibitors in arthritis, atherosclerosis, blood pressure regulation, obesity and cancer.

Differential biochemical and cellular actions of Premarin estrogens: distinct pharmacology of bazedoxifene-conjugated estrogens combination

The use of estrogen-based therapies and the selective estrogen receptor (ER) modulator (SERM), raloxifene, which are approved for postmenopausal osteoporosis, is associated with side effects such as uterine/breast hyperproliferation, thromboembolism, and hot flashes. A combination of a new SERM, bazedoxifene (BZA), and Premarin (conjugated estrogens; CE) is under investigation to mitigate the estrogen/SERM side effects with promising results in Phase III clinical trials. To explore the mechanism of BZA/CE action, we investigated the recruitment of cofactor peptides to ERalpha by components of CE and a mixture containing the 10 major components of CE with or without three different SERMs. Here, we demonstrate differential recruitment of cofactor peptides to ERalpha by the individual CE components using a multiplex nuclear receptor-cofactor peptide interaction assay. We show that estrone and equilin are partial agonists in comparison with 17beta-estradiol in recruiting cofactor peptides to ERalpha. Further, CE was more potent than 17beta-estradiol in mediating ERalpha interaction with cofactor peptides. Interestingly, BZA was less potent than other SERMs in antagonizing the CE-mediated cofactor peptide recruitment to ERalpha. Finally, in accordance with these biochemical findings, 17beta-estradiol and CE, as well as SERM/CE combinations, showed differential gene regulation patterns in MCF-7 cells. In addition, BZA showed antagonism of a unique set of CE-regulated genes and did not down-regulate the expression of a number of CE-regulated genes, the expression of which was effectively antagonized by the other two SERMs. These results indicate that SERMs in combination with CE exhibit differential pharmacology, and therefore, combinations of other SERMs and estrogen preparations may not yield the same beneficial effects that are observed in clinic by pairing BZA with CE.