Bazedoxifene acetate: a selective estrogen receptor modulator with improved selectivity

Bazedoxifene attenuates dextran sodium sulfate-induced colitis in mice through gut microbiota modulation and inhibition of STAT3 and NF-κB pathways

Inflammatory bowel disease (IBD) is a chronic and relapsing inflammatory disorder of the gastrointestinal tract for which treatment options remain limited. In this study, we used a dual-luciferase-based screening of an FDA-approved drug library, identifying Bazedoxifene (BZA) as an inhibitor of the NF-κB pathway. We further investigated its therapeutic effects in a dextran sodium sulfate (DSS)-induced colitis model and explored its impact on gut microbiota regulation and the underlying molecular mechanisms. Our results showed that BZA significantly reduced DSS-induced colitis symptoms in mice, evidenced by decreased colon length shortening, lower histological scores, and increased expression of intestinal mucosal barrier-associated proteins, such as Claudin 1, Occludin, Zo-1, Mucin 2 (Muc2), and E-cadherin. Used independently, BZA showed therapeutic effects comparable to those of infliximab (IFX). In addition, BZA modulated the abundance of gut microbiota especially Bifidobacterium pseudolongum, and influenced microbial metabolite production. Crucially, BZA's alleviation of DSS-induced colitis in mice was linked to change in gut microbiota composition, as evidenced by in vivo gut microbiota depletion and fecal microbiota transplantation (FMT) mice model. Molecularly, BZA inhibited STAT3 and NF-κB activation in DSS-induced colitis in mice. In general, BZA significantly reduced DSS-induced colitis in mice through modulating the gut microbiota and inhibiting STAT3 and NF-κB activation, and its independent use demonstrated a therapeutic potential comparable to IFX. This study highlights gut microbiota's role in IBD drug development, offering insights for BZA's future development and its clinical applications.

Small molecule targeted therapies for endometrial cancer: progress, challenges, and opportunities

Endometrial cancer (EC) is a common malignancy among women worldwide, and its recurrence makes it a common cause of cancer-related death. Surgery and external radiation, chemotherapy, or a combination of strategies are the cornerstone of therapy for EC patients. However, adjuvant treatment strategies face certain drawbacks, such as resistance to chemotherapeutic drugs; therefore, it is imperative to explore innovative therapeutic strategies to improve the prognosis of EC. With the development of pathology and pathophysiology, several biological targets associated with EC have been identified, including PI3K/Akt/mTOR, PARP, GSK-3β, STAT-3, and VEGF. In this review, we summarize the progress of small molecule targeted therapies in terms of both basic research and clinical trials and provide cases of small molecules combined with fluorescence properties in the clinical applications of integrated diagnosis and treatment. We hope that this review will facilitate the further understanding of the regulatory mechanism governing the dysregulation of oncogenic signaling in EC and provide insights into the possible future directions of targeted therapeutic regimens for EC treatment by developing new agents with fluorescence properties for the clinical applications of integrated diagnosis and treatment.

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.

Nitro-Enabled Atroposelective Dynamic Kinetic Resolution of 2-Arylindoles by Phase-Transfer Catalysis

This study presents the atroposelective alkylation of 2-arylindoles catalyzed by a substituted cinchonium salt as a phase-transfer catalyst. Under the optimized reaction conditions, various substrates are employed to yield products with high enantioselectivity. The presence of an ortho-nitro group at the aromatic ring is essential for high atroposelectivity, because it facilitates favorable interactions between the catalyst and substrate. The origin of the enantioselectivity reveals favorable π-π interactions for both enantiomers and unfavorable steric strains for undesired enantiomers.

Estrogen and psychosis - a review and future directions

The link between sex hormones and schizophrenia has been suspected for over a century; however, scientific evidence supporting the pharmacotherapeutic effects of exogenous estrogen has only started to emerge during the past three decades. Accumulating evidence from epidemiological and basic research suggests that estrogen has a protective effect in women vulnerable to schizophrenia. Such evidence has led multiple researchers to investigate the role of estrogen in schizophrenia and its use in treatment. This narrative review provides an overview of the effects of estrogen as well as summarizes the recent work regarding estrogen as a treatment for schizophrenia, particularly the use of new-generation selective estrogen receptor modulators.

Genetic overlap for ten cardiovascular diseases: A comprehensive gene-centric pleiotropic association analysis and Mendelian randomization study

Recent studies suggest that pleiotropic effects may explain the genetic architecture of cardiovascular diseases (CVDs). We conducted a comprehensive gene-centric pleiotropic association analysis for ten CVDs using genome-wide association study (GWAS) summary statistics to identify pleiotropic genes and pathways that may underlie multiple CVDs. We found shared genetic mechanisms underlying the pathophysiology of CVDs, with over two-thirds of the diseases exhibiting common genes and single-nucleotide polymorphisms (SNPs). Significant positive genetic correlations were observed in more than half of paired CVDs. Additionally, we investigated the pleiotropic genes shared between different CVDs, as well as their functional pathways and distribution in different tissues. Moreover, six hub genes, including ALDH2, XPO1, HSPA1L, ESR2, WDR12, and RAB1A, as well as 26 targeted potential drugs, were identified. Our study provides further evidence for the pleiotropic effects of genetic variants on CVDs and highlights the importance of considering pleiotropy in genetic association studies.

Recent advance of small-molecule drugs for clinical treatment of osteoporosis: A review

Osteoporosis is a metabolic bone disorder typified by a reduction in bone mass and structural degradation of bone tissue, leading to heightened fragility and vulnerability to fractures. The incidence of osteoporosis increases with age, making it a significant public health challenge. The pathogenesis of osteoporosis involves an imbalance between osteoblast-mediated bone formation and resorption. The current treatment options for osteoporosis include bisphosphonates, hormone replacement therapy (HRT), selective estrogen receptor modulators (SERMs), and denosumab. The recent advances in small-molecule drugs for the clinical treatment of osteoporosis offer promising options for improving bone health and reducing fracture risk. This review aims to provide an overview of the clinical applications and synthetic routes of representative small-molecule drugs for the treatment of osteoporosis. A comprehensive understanding of the synthetic methods of drug molecules for osteoporosis may inspire the development of new, more effective, and practical synthetic techniques for treating this condition.

Palladium-catalyzed synthesis of 2,3-disubstituted indoles via arylation of ortho-alkynylanilines with arylsiloxanes

In this study, we report the electrophilic cyclization of N,N-dimethyl-o-alkynylanilines with arylsiloxanes in the presence of [Pd(OAc)2] and Ag2O catalytic system, which leads to the efficient synthesis of indoles, similar to the one that is obtained through Larock indole synthesis. A range of aryl(trimethoxy)silanes with EDGs and EWGs were successfully utilized for the synthesis of a diverse variety of substituted indoles via the cleavage of the C-Si bond. This protocol exhibits good functional group tolerance and wide substrate scope to provide 2,3-diaryl-N-methylindoles in 26-88% yields.

Membrane estrogen receptor α signaling modulates the sensitivity to estradiol treatment in a dose- and tissue- dependent manner

Estradiol (E2) affects both reproductive and non-reproductive tissues, and the sensitivity to different doses of E2 varies between tissues. Membrane estrogen receptor α (mERα)-initiated signaling plays a tissue-specific role in mediating E2 effects, however, it is unclear if mERα signaling modulates E2 sensitivity. To determine this, we treated ovariectomized C451A females, lacking mERα signaling, and wildtype (WT) littermates with physiological (0.05 μg/mouse/day (low); 0.6 μg/mouse/day (medium)) or supraphysiological (6 μg/mouse/day (high)) doses of E2 (17β-estradiol-3-benzoate) for three weeks. Low-dose treatment increased uterus weight in WT, but not C451A mice, while non-reproductive tissues (gonadal fat, thymus, trabecular and cortical bone) were unaffected in both genotypes. Medium-dose treatment increased uterus weight and bone mass and decreased thymus and gonadal fat weights in WT mice. Uterus weight was also increased in C451A mice, but the response was significantly attenuated (- 85%) compared to WT mice, and no effects were triggered in non-reproductive tissues. High-dose treatment effects in thymus and trabecular bone were significantly blunted (- 34% and - 64%, respectively) in C451A compared to WT mice, and responses in cortical bone and gonadal fat were similar between genotypes. Interestingly, the high dose effect in uterus was enhanced (+ 26%) in C451A compared to WT mice. In conclusion, loss of mERα signaling reduces the sensitivity to physiological E2 treatment in both non-reproductive tissues and uterus. Furthermore, the E2 effect after high-dose treatment in uterus is enhanced in the absence of mERα, suggesting a protective effect of mERα signaling in this tissue against supraphysiological E2 levels.

Understanding the mechanistic potential of plant based phytochemicals in management of postmenopausal osteoporosis

Postmenopausal osteoporosis, an epidemic disorder is defined as a loss in bone mineral density and a greater possibility of fractures in older women. It is a multifactorial disease under the control of various genetic, hormonal, and environmental factors. Insufficiency of estrogen hormone, leads to postmenopausal osteoporosis. Hormone replacement therapy (HRT), despite being the most effective treatment, it is associated with the risk of breast cancer and cardiovascular disorders. This review seeks to compile the most recent information on medicinal plants and natural compounds used to treat and prevent postmenopausal osteoporosis. Furthermore, the origin, chemical constituents and the molecular mechanisms responsible for this therapeutic and preventive effect are also discussed. Literature research was conducted using PubMed, Science direct, Scopus, Web of Science, and Google Scholar. Different plant extracts and pure compounds exerts their antiosteoporotic activity by inhibition of RANKL and upregulation of OPG. RANKL signaling regulates osteoclast formation, characterized by increased bone turnover and osteoprotegrin is a decoy receptor for RANKL thereby preventing bone loss from excessive resorption. In addition, this review also includes the chemical structure of bioactive compounds acting on NFκB, TNF α, RUNX2. In conclusion, we propose that postmenopausal osteoporosis could be prevented or treated with herbal products.

Biodegradable bilayer hydrogel membranes loaded with bazedoxifene attenuate blood-spinal cord barrier disruption via the NF-κB pathway after acute spinal cord injury

After spinal cord injury (SCI), blood-spinal cord barrier (BSCB) disruption and hemorrhage lead to blood cell infiltration and progressive secondary injuries. Therefore, early restoration of the BSCB represents a key step in the treatment of SCI. Bazedoxifene (BZA), a third-generation estrogen receptor modulator, has recently been reported to inhibit inflammation and alleviate blood-brain barrier disruption caused by traumatic brain injury, attracting great interest in the field of central nervous system injury and repair. However, whether BZA can attenuate BSCB disruption and contribute to SCI repair remains unknown. Here, we developed a new type of biomaterial carrier and constructed a BZA-loaded HSPT (hyaluronic acid (HA), sodium alginate (SA), polyvinyl alcohol (PVA), tetramethylpropane (TPA) material construction) (HSPT@Be) system to effectively deliver BZA to the site of SCI. We found that HSPT@Be could significantly reduce inflammation in the spinal cord in SCI rats and attenuate BSCB disruption by providing covering scaffold, inhibiting oxidative stress, and upregulating tight junction proteins, which was mediated by regulation of the NF-κB/MMP signaling pathway. Importantly, functional assessment showed the evident improvement of behavioral functions in the HSPT@Be-treated SCI rats. These results indicated that HSPT@Be can attenuate BSCB disruption via the NF-κB pathway after SCI, shedding light on its potential therapeutic benefit for SCI. STATEMENT OF SIGNIFICANCE: After spinal cord injury, blood-spinal cord barrier disruption and hemorrhage lead to blood cell infiltration and progressive secondary injuries. Bazedoxifene has recently been reported to inhibit inflammation and alleviate blood-brain barrier disruption caused by traumatic brain injury. However, whether BZA can attenuate BSCB disruption and contribute to SCI repair remains unknown. In this study, we developed a new type of biomaterial carrier and constructed a bazedoxifene-loaded HSPT (HSPT@Be) system to efficiently treat SCI. HSPT@Be could provide protective coverage, inhibit oxidative stress, and upregulate tight junction proteins through NF-κB/MMP pathway both in vivo and in vitro, therefore attenuating BSCB disruption. Our study fills the application gap of biomaterials in BSCB restoration.

Novel, highly sensitive, in vivo screening method detects estrogenic activity at low doses of bisphenol A

Low doses of bisphenol A (BPA), a typical endocrine-disrupting chemical (EDC), have been reported to exhibit estrogenic action in animals; however, the effects have not been fully clarified because of their non-reproducibility. Here, we developed a novel, short-term screening test for estrogen-like chemicals using in vivo bioluminescence imaging of estrogen-responsive reporter (E-Rep) mice. Comparative studies using 17α-ethinylestradiol and selective estrogen receptor modulators demonstrated that the method provides higher detection sensitivity and requires less time than the uterotrophic bioassay, a well-established, in vivo screening method for estrogen-like chemicals. Our method could detect the estrogenic effects of BPA at doses below tolerable daily intakes, whereas the uterotrophic bioassay could not. Our results indicated that in vivo bioluminescence imaging using E-Rep mice was extremely useful for screening estrogenic chemicals and detecting estrogenic effects at low doses of EDCs, including BPA. Our method should help resolve the controversy about low-dose effects of EDCs.

Polyunsaturated Fatty Acids Drive Lipid Peroxidation during Ferroptosis

Ferroptosis is a form of regulated cell death that is intricately linked to cellular metabolism. In the forefront of research on ferroptosis, the peroxidation of polyunsaturated fatty acids has emerged as a key driver of oxidative damage to cellular membranes leading to cell death. Here, we review the involvement of polyunsaturated fatty acids (PUFAs), monounsaturated fatty acids (MUFAs), lipid remodeling enzymes and lipid peroxidation in ferroptosis, highlighting studies revealing how using the multicellular model organism Caenorhabditis elegans contributes to the understanding of the roles of specific lipids and lipid mediators in ferroptosis.

The neuroprotective effects of estrogen and estrogenic compounds in spinal cord injury

Spinal cord injury (SCI) occurs when the spinal cord is damaged from either a traumatic event or disease. SCI is characterised by multiple injury phases that affect the transmission of sensory and motor signals and lead to temporary or long-term functional deficits. There are few treatments for SCI. Estrogens and estrogenic compounds, however, may effectively mitigate the effects of SCI and therefore represent viable treatment options. This review systematically examines the pre-clinical literature on estrogen and estrogenic compound neuroprotection after SCI. Several estrogens were examined by the included studies: estrogen, estradiol benzoate, Premarin, isopsoralen, genistein, and selective estrogen receptor modulators. Across these pharmacotherapies, we find significant evidence that estrogens indeed offer protection against myriad pathophysiological effects of SCI and lead to improvements in functional outcomes, including locomotion. A STRING functional network analysis of proteins modulated by estrogen after SCI demonstrated that estrogen simultaneously upregulates known neuroprotective pathways, such as HIF-1, and downregulates pro-inflammatory pathways, including IL-17. These findings highlight the strong therapeutic potential of estrogen and estrogenic compounds after SCI.

Pharmacokinetic Interactions Between Bazedoxifene and Cholecalciferol: An Open-Label, Randomized, Crossover Study in Healthy Male Volunteers

Purpose

The combined administration of bazedoxifene, a tissue-selective estrogen receptor modulator, and cholecalciferol can be a promising therapeutic option for postmenopausal osteoporosis patients. This study aimed to examine the pharmacokinetic interactions between these two drugs and the tolerability of their combined administration in healthy male subjects.

Patients and Methods

Thirty male volunteers were randomly assigned to one of the six sequences comprised of three treatments: bazedoxifene 20 mg monotherapy, cholecalciferol 1600 IU monotherapy, and combined bazedoxifene and cholecalciferol therapy. For each treatment, a single dose of the investigational drug(s) was administered orally, and serial blood samples were collected to measure the plasma concentrations of bazedoxifene and cholecalciferol. Pharmacokinetic parameters were calculated using the non-compartmental method. The point estimate and 90% confidence interval (CI) of the geometric mean ratio (GMR) were obtained to compare the exposures of combined therapy and monotherapy. The pharmacokinetic parameters compared were the maximum plasma concentration (C_max) and the area under the plasma concentration-time curve from time zero to the last quantifiable concentration (AUC_last). The safety and tolerability of the combined therapy were assessed in terms of the frequency and severity of adverse events (AEs).

Results

For bazedoxifene, the GMR (90% CI) of the combined therapy to monotherapy was 1.044 (0.9263-1.1765) for C_max and 1.1329 (1.0232-1.2544) for AUC_last. For baseline-adjusted cholecalciferol, the GMR (90% CI) of the combined therapy to monotherapy was 0.8543 (0.8005-0.9117) for C_max and 0.8056 (0.7445-0.8717) for AUC_last. The frequency of AEs observed was not significantly different between the combined therapy and monotherapy, and their severity was mild in all cases.

Conclusion

A mild degree of pharmacokinetic interaction was observed when bazedoxifene and cholecalciferol were administered concomitantly to healthy male volunteers. This combined therapy was well tolerated at the dose levels used in the present study.

Detection of bazedoxifene, a selective estrogen receptor modulator, in human urine by liquid chromatography-tandem mass spectrometry

Bazedoxifene, a selective estrogen receptor modulator, has been explicitly included in the prohibited list issued by the World Anti-Doping Agency (WADA) since January 2020. A high-resolution liquid chromatography-tandem mass spectrometric detection method was developed to identify bazedoxifene and its metabolites in human urine and to quantify bazedoxifene (free plus glucuronide) for doping control purposes. Bazedoxifene acetate (20 mg) was orally administered to seven male volunteers, and the urine samples collected were analyzed using the developed method. The linearity ranged from 0.5 to 200 ng/ml, and the limit of detection was <0.2 ng/ml. The interday precision (2.2% to 3.6%) and the interday accuracy (-10.0% to 1.9%) were adequate. Bazedoxifene, bazedoxifene-N-oxide, and bazedoxifene glucoconjugates were identified in the urine samples. The profiles of the urinary excretion indicated the presence of small amounts of free bazedoxifene and bazedoxifene-N-oxide, whereas bazedoxifene glucuronide was the predominant metabolite. The cumulative excretion amount of bazedoxifene (free form plus glucuronide conjugate) within 78 h after the administration was 0.7% to 1.3% of the total dose. In all subjects, bazedoxifene (free plus glucuronide) could be detected in urine up to 78 h after administration.

Accelerating drug development in breast cancer: New frontiers for ER inhibition

The estrogen receptor (ER) is an important driver in the proliferation, tumorigenesis, and progression of breast cancers, and targeting ER signaling at different levels is a successful strategy in the control of hormone receptor positive (HR+) breast cancer. Endocrine therapy has been the treatment of choice for HR+ breast cancer in the early and advanced stages with multiple agents, including selective estrogen receptor modulators (SERMS), selective estrogen receptor degraders (SERDs), and aromatase inhibitors (AIs), which vary in their mechanisms of action and pharmacokinetics. Combination strategies also employ cyclin dependent kinase 4 and 6 and phosphatidylinositol 3-kinase to maximize the benefits of endocrine therapy. This paper reviews the clinical development of SERDs and other novel ER inhibitors, as well as combination strategies to overcome mechanisms of ER pathway escape. It also assesses the advantages of newer oral ER inhibitors with increased bioavailability, improved therapeutic index, better administration, and increased efficacy, as well as discussing future directions in the field.

Phenols in Pharmaceuticals: Analysis of a Recurring Motif

Phenols and phenolic ethers are significant scaffolds recurring both in nature and among approved small-molecule pharmaceuticals. This compendium presents the first comprehensive compilation and analysis of the structures of U.S. FDA-approved molecules containing phenol or phenolic ether fragments. This dataset comprises 371 structures, which are strongly represented by natural products. A total of 55 of the compounds described here are on the World Health Organization's list of essential medicines. Structural analysis reveals significant differences in the physicochemical properties imparted by phenols versus phenol ethers, each having benefits and drawbacks for drug developability. Despite trends over the past decade to increase the fraction of sp³ centers in drug leads, thereby "escaping flatland", phenols and phenolic ethers are represented in 62% of small-molecule drugs approved in 2020, suggesting that this aromatic moiety holds a special place in drugs and natural products.

Combined inhibition of IL‑6 and IL‑8 pathways suppresses ovarian cancer cell viability and migration and tumor growth

Ovarian cancer is the most lethal gynecological cancer type in the United States. The success of current chemotherapies is limited by chemoresistance and side effects. Targeted therapy is a promising future direction for cancer therapy. In the present study, the efficacy of co‑targeting IL‑6 and IL‑8 in human ovarian cancer cells by bazedoxifene (Baze) + SCH527123 (SCH) treatment was examined. ELISA, cell viability, cell proliferation, cell migration, cell invasion, western blotting and peritoneal ovarian tumor mouse model analyses were performed to analyze the expression levels of IL‑6 and IL‑8, tumor growth, tumor migration and invasion, and the possible pathways of human ovarian cancer cell lines (SKOV3, CAOV3 and OVCAR3) and patient‑derived OV75 ovarian cancer cells. Each cell line was treated by monotherapy or combination therapy. The results demonstrated that IL‑6 and IL‑8 were secreted by human ovarian cancer cell lines. Compared with the DMSO control, the combination of IL‑6/glycoprotein 130 inhibitor Baze and IL‑8 inhibitor SCH synergistically inhibited cell viability in ovarian cancer cells. Baze + SCH also inhibited cell migration and invasion, suppressed ovarian tumor growth and inhibited STAT3 and AKT phosphorylation, as well as survivin expression. Therefore, co‑targeting the IL‑6 and IL‑8 signaling pathways may be an effective approach for ovarian cancer treatment.

Discovery and characterization of potent And-1 inhibitors for cancer treatment

Acidic nucleoplasmic DNA-binding protein 1 (And-1), an important factor for deoxyribonucleic acid (DNA) replication and repair, is overexpressed in many types of cancer but not in normal tissues. Although multiple independent studies have elucidated And-1 as a promising target gene for cancer therapy, an And-1 inhibitor has yet to be identified. Using an And-1 luciferase reporter assay to screen the Library of Pharmacologically Active Compounds (LOPAC) in a high throughput screening (HTS) platform, and then further screen the compound analog collection, we identified two potent And-1 inhibitors, bazedoxifene acetate (BZA) and an uncharacterized compound [(E)-5-(3,4-dichlorostyryl)benzo[c][1,2]oxaborol-1(3H)-ol] (CH3), which specifically inhibit And-1 by promoting its degradation. Specifically, through direct interaction with And-1 WD40 domain, CH3 interrupts the polymerization of And-1. Depolymerization of And-1 promotes its interaction with E3 ligase Cullin 4B (CUL4B), resulting in its ubiquitination and subsequent degradation. Furthermore, CH3 suppresses the growth of a broad range of cancers. Moreover, And-1 inhibitors re-sensitize platinum-resistant ovarian cancer cells to platinum drugs in vitro and in vivo. Since BZA is an FDA approved drug, we expect a clinical trial of BZA-mediated cancer therapy in the near future. Taken together, our findings suggest that targeting And-1 by its inhibitors is a potential broad-spectrum anti-cancer chemotherapy regimen.

Breast Cancer Treatments: Updates and New Challenges

Breast cancer (BC) is the most frequent cancer diagnosed in women worldwide. This heterogeneous disease can be classified into four molecular subtypes (luminal A, luminal B, HER2 and triple-negative breast cancer (TNBC)) according to the expression of the estrogen receptor (ER) and the progesterone receptor (PR), and the overexpression of the human epidermal growth factor receptor 2 (HER2). Current BC treatments target these receptors (endocrine and anti-HER2 therapies) as a personalized treatment. Along with chemotherapy and radiotherapy, these therapies can have severe adverse effects and patients can develop resistance to these agents. Moreover, TNBC do not have standardized treatments. Hence, a deeper understanding of the development of new treatments that are more specific and effective in treating each BC subgroup is key. New approaches have recently emerged such as immunotherapy, conjugated antibodies, and targeting other metabolic pathways. This review summarizes current BC treatments and explores the new treatment strategies from a personalized therapy perspective and the resulting challenges.

Current and emerging estrogen receptor-targeted therapies for the treatment of breast cancer

Nearly 80% of all breast cancers are estrogen receptor positive (ER+) and require the activity of this transcription factor for tumor growth and survival. Thus, endocrine therapies, which target the estrogen signaling axis, have and will continue to be the cornerstone of therapy for patients diagnosed with ER+ disease. Several inhibitors of ER activity exist, including aromatase inhibitors (AIs), selective estrogen receptor modulators (SERMs), selective estrogen receptor degraders/down-regulators (SERDs), and ER proteolysis-targeting chimeras (ER PROTACs); drugs which differ in the mechanism(s) by which they inhibit this signaling pathway. Notwithstanding their significant impact on the management of this disease, resistance to existing endocrine therapies remains a major impediment to durable clinical responses. Although the mechanisms of resistance are complex and varied, dependence on ER is typically retained after progression on SERMs and AIs, suggesting that ER remains a bona fide therapeutic target. The discovery and development of orally bioavailable drugs that eliminate ER expression (SERDs and ER PROTACs) will likely aid in treating this growing patient population. All of the existing endocrine therapies were developed with the intent of inhibiting the cancer cell intrinsic actions of ER and/or with the objective of achieving extreme estrogen deprivation and most achieve that goal. A longstanding question that remains to be addressed, however, is how actions of existing interventions extrinsic to the cancer cells influence tumor biology. We believe that these issues need to be addressed in the development of strategies to develop the next generation of ER-modulators optimized for positive activities in both cancer cells and other cells within the tumor microenvironment (TME).

Bioequivalence for a Fixed-Dose Combination Formulation of Bazedoxifene and Cholecalciferol Compared With the Corresponding Single Entities Given Together

A fixed-dose combination (FDC) formulation of bazedoxifene 20 mg and cholecalciferol 8 mg was developed to increase medication compliance and convenience for osteoporosis patients. This study was conducted to demonstrate bioequivalence by comparing the pharmacokinetic (PK) profiles and tolerability of an FDC tablet and the individual component tablets. A randomized, open-label, single-dosing, 2-treatment, 2-period, 2-sequence crossover study was conducted in 52 healthy subjects. All subjects were randomly assigned to 2 sequences, and they received FDC tablets of bazedoxifene and cholecalciferol and individual component tablets. Serial blood samples for PK evaluation were collected up to 24 hours predose and 120 hours postdose, and the PK parameters were estimated by noncompartmental methods. Throughout the study, tolerability was assessed based on adverse events, vital signs, and clinical laboratory tests. Of the enrolled 52 subjects, 47 subjects completed the study. The results, the geometric mean ratios (GMRs) and 90% confidence intervals (90%CIs), of bazedoxifene C_max and AUC_0-t for FDC to single entities given together were 0.98 (0.91-1.05) and 1.02 (0.97-1.07), respectively. The GMRs (90%CIs) of cholecalciferol C_max and AUC_0-t for FDC to single entities given together were 0.96 (0.91-1.00) and 0.94 (0.90-0.99), respectively. Overall, the GMRs (90%CIs) of the PK parameter of bazedoxifene and cholecalciferol fell within the conventional bioequivalence range of 0.8-1.25. There were no clinically significant differences in the safety profile between the 2 treatments. In conclusion, this study confirmed the development of a new FDC drug by demonstrating that the FDC formulation of bazedoxifene and cholecalciferol is biologically equivalent to the coadministered individual formulations.

A compendium of kinetic modulatory profiles identifies ferroptosis regulators

Cell death can be executed by regulated apoptotic and nonapoptotic pathways, including the iron-dependent process of ferroptosis. Small molecules are essential tools for studying the regulation of cell death. Using time-lapse imaging and a library of 1,833 bioactive compounds, we assembled a large compendium of kinetic cell death modulatory profiles for inducers of apoptosis and ferroptosis. From this dataset we identify dozens of ferroptosis suppressors, including numerous compounds that appear to act via cryptic off-target antioxidant or iron chelating activities. We show that the FDA-approved drug bazedoxifene acts as a potent radical trapping antioxidant inhibitor of ferroptosis both in vitro and in vivo. ATP-competitive mechanistic target of rapamycin (mTOR) inhibitors, by contrast, are on-target ferroptosis inhibitors. Further investigation revealed both mTOR-dependent and mTOR-independent mechanisms that link amino acid metabolism to ferroptosis sensitivity. These results highlight kinetic modulatory profiling as a useful tool to investigate cell death regulation.

Pharmacotherapeutic options for the treatment of menopausal symptoms

Introduction: Menopausal symptoms can be very overwhelming for women. Over the years, many pharmacotherapeutic options have been tested, and others are still being developed. Hormone therapy (HT) is the most efficient therapy for managing vasomotor symptoms and related disturbances. The term HT comprises estrogens and progestogens, androgens, tibolone, the tissue-selective estrogen complex (TSEC), a combination of bazedoxifene and conjugated estrogens, and the selective estrogen receptor modulators, such as ospemifene. Estrogens and progestogens and androgens may differ significantly for chemical structure and can be delivered through different routes, thereby displaying various pharmacological and clinical properties. Tibolone, TSEC and SERM also exhibit unique pharmacodynamics that can be exploited to obtain distinctive therapeutic effects. Non-hormonal options fall mainly into the selective serotonin reuptake inhibitor (SSRI) and selective noradrenergic reuptake inhibitor (SNRI), GABA-analogue drug classes.Areas covered: Herein, the authors describe the pharmacokinetics and pharmacodynamics of hormonal (androgens, estrogens, progestogens, tibolone, TSEC, SERMs) and non-hormonal (SSRIs, SNRIs, Gabapentin, Pregabalin, Oxybutynin, Neurokinin antagonists) treatments for menopausal symptoms and report essential clinical trial data in humans.Expert opinion: Patient tailoring of treatment is key to managing symptoms of menopause. Physicians must have in-depth knowledge of the pharmacology of compounds to tailor therapy to the individual patient's characteristics and needs.

Bispecific Estrogen Receptor α Degraders Incorporating Novel Binders Identified Using DNA-Encoded Chemical Library Screening

Bispecific degraders (PROTACs) of ERα are expected to be advantageous over current inhibitors of ERα signaling (aromatase inhibitors/SERMs/SERDs) used to treat ER+ breast cancer. Information from DNA-encoded chemical library (DECL) screening provides a method to identify novel PROTAC binding features as the linker positioning, and binding elements are determined directly from the screen. After screening ∼120 billion DNA-encoded molecules with ERα WT and 3 gain-of-function (GOF) mutants, with and without estradiol to identify features that enrich ERα competitively, the off-DNA synthesized small molecule exemplar 7 exhibited nanomolar ERα binding, antagonism, and degradation. Click chemistry synthesis on an alkyne E3 ligase engagers panel and an azide variant of 7 rapidly generated bispecific nanomolar degraders of ERα, with PROTACs 18 and 21 inhibiting ER+ MCF7 tumor growth in a mouse xenograft model of breast cancer. This study validates this approach toward identifying novel bispecific degrader leads from DECL screening with minimal optimization.

A comprehensive review on anticancer mechanism of bazedoxifene

Cancer is counted as a second leading cause of death among nontransmissible diseases. Identification of novel anticancer drugs is therefore necessary for the effective treatment of cancer. Conventional drug discovery is time consuming and expensive process. Unlike conventional drug discovery, drug repositioning offers a novel strategy for urgent drug discovery since it is a cost-effective and faster process. Bazedoxifene (BZA) is a synthetic selective estrogen receptor modulator, approved by the United States Food and Drug Administration for the treatment of osteoporosis in postmenopausal women. BZA is now being studied for its anticancer activity in various cancers including breast cancer, liver cancer, pancreatic cancer, colon cancer, head and neck cancer, medulloblastoma, brain cancer, and gastrointestinal cancer. Studies have reported that BZA is effective in reducing cancer progression through multiple mechanisms. BZA could effectively inhibit STAT3, PI3K/AKT, and MAPK signaling pathways and induce apoptosis. In addition to its anticancer activity as monotherapy, BZA has been shown to enhance the chemotherapeutic efficacy of clinical drugs such as paclitaxel, cisplatin, palbociclib, and oxaliplatin in multiple neoplasms. This review mainly focused on the anticancer activity, cellular targets, and anticancer mechanism of BZA, which may help the further design and conduct of research and repositioning it for oncological clinic trials.

Using in silico modelling and FRET-based assays in the discovery of novel FDA-approved drugs as inhibitors of MERS-CoV helicase

A Förster resonance energy transfer (FRET)-based assay was used to screen the FDA-approved compound library against the MERS-CoV helicase, an essential enzyme for virus replication within the host cell. Five compounds inhibited the helicase activity with submicromolar potencies (IC₅₀, 0.73-1.65 µM) and ten compounds inhibited the enzyme with micromolar potencies (IC₅₀, 19.6-502 µM). The molecular operating environment (MOE) was used to dock the identified inhibitors on the MERS-CoV helicase nucleotide binding. Strong inhibitors docked well in the nucleotide-binding site and established interactions with some of the essential residues. There was a reasonable correlation between the observed IC₅₀ values and the MOE docking scores of the strong inhibitors (r ² = 0.74), indicating the ability of the in silico docking model to predict the binding of strong inhibitors. In silico docking could be a useful complementary tool used with the FRET-based assay to predict new MERS-CoV helicase inhibitors. The identified inhibitors could potentially be used in the clinical development of new antiviral treatment for MERS-CoV and other coronavirus related diseases, including coronavirus disease 2019 (COVID-19).

The Role of Estradiol in Traumatic Brain Injury: Mechanism and Treatment Potential

Patients surviving traumatic brain injury (TBI) face numerous neurological and neuropsychological problems significantly affecting their quality of life. Extensive studies over the past decades have investigated pharmacological treatment options in different animal models, targeting various pathological consequences of TBI. Sex and gender are known to influence the outcome of TBI in animal models and in patients, respectively. Apart from its well-known effects on reproduction, 17β-estradiol (E2) has a neuroprotective role in brain injury. Hence, in this review, we focus on the effect of E2 in TBI in humans and animals. First, we discuss the clinical classification and pathomechanism of TBI, the research in animal models, and the neuroprotective role of E2. Based on the results of animal studies and clinical trials, we discuss possible E2 targets from early to late events in the pathomechanism of TBI, including neuroinflammation and possible disturbances of the endocrine system. Finally, the potential relevance of selective estrogenic compounds in the treatment of TBI will be discussed.

Bazedoxifene Plays a Protective Role against Inflammatory Injury of Endothelial Cells by Targeting CD40

The inflammatory response and oxidative stress play key roles in the formation and development of atherosclerosis. Bazedoxifene is a new IL6/GP130 inhibitor recommended by the FDA for clinical use as a selective estrogen receptor modulator. However, its role in cardiovascular diseases has been poorly studied. In our study, we explored the mechanism of bazedoxifene's protective effect against inflammatory injury of vascular endothelial cells (VECs) stimulated by TNF-α. Various methods were used to verify the effect of bazedoxifene on VECs, including a cell viability assay, a wound healing assay, immunofluorescence staining, and western blotting. Our results showed that TNF-α could induce inflammatory damage to VECs, which manifested as upregulated expression of CD40, increased production of ROS, enhanced adhesion of THP-1 cells to VECs, and impaired viability and migration of VECs, while bazedoxifene could significantly reduce the endothelial damage caused by TNF-α. In addition, we found that an siRNA targeting CD40 dramatically alleviated the VEC damage induced by TNF-α. Therefore, we explored the potential relationship between bazedoxifene and CD40. Our data suggest that bazedoxifene has a protective effect against VEC damage induced by TNF-α and that its underlying mechanism may be related to the regulation of CD40.

Design, synthesis, and biological evaluation of new raloxifene analogues of improved antagonist activity and endometrial safety

Raloxifene agonism of estrogen receptor (ER) in post-menopausal endometrium is not negligible. Based on a rational drug design workflow, we synthesized 14 analogues of raloxifene bearing a polar group in the aromatic ring of the basic side chain (BSC) and/or changes in the bulkiness of the BSC amino group. Analogues with a polar BSC aromatic ring and amino group substituents of increasing volume displayed increasing ER antagonism in Ishikawa cells. Analogues with cyclohexylaminoethoxy (13a) or adamantylaminoethoxy BSC (13b) lacking a polar aromatic ring displayed high ER-binding affinity and ER antagonism in Ishikawa cells higher than raloxifene and similar to fulvestrant (ICI182,780). The endometrial surface epithelium of immature female CD1 mice injected with 13b was comparable to that of vehicle-treated mice, while that of mice treated with estradiol, raloxifene or 13b in combination with estradiol was hyperplastic. These findings indicate that raloxifene analogues with a bulky BSC amino group could provide for higher endometrial safety treatment of the menopausal syndrome.

Bazedoxifene - a promising brain active SERM that crosses the blood brain barrier and enhances spatial memory

Over 20 years of accumulated evidence has shown that the major female sex hormone 17β-estradiol can enhance cognitive functioning. However, the utility of estradiol as a therapeutic cognitive enhancer is hindered by its unwanted peripheral effects (carcinogenic). Selective estrogen receptor modulators (SERMs) avoid the unwanted effects of estradiol by acting as estrogen receptor antagonists in some tissues such as breast and uterus, but as agonists in others such as bone, and are currently used for the treatment of osteoporosis. However, understanding of their actions in the brain are limited. The third generation SERM bazedoxifene has recently been FDA approved for clinical use with an improved biosafety profile. However, whether bazedoxifene can enter the brain and enhance cognition is unknown. Using mice, the current study aimed to explore if bazedoxifene can 1) cross the blood-brain barrier, 2) rescue ovariectomy-induced hippocampal-dependent spatial memory deficit, and 3) activate neural estrogen response element (ERE)-dependent gene transcription. Using liquid chromatography-mass spectrometry (LC-MS), we firstly demonstrate that a peripheral injection of bazedoxifene can enter the brain. Secondly, we show that an acute intraperitoneal injection of bazedoxifene can rescue ovariectomy-induced spatial memory deficits. And finally, using the ERE-luciferase reporter mouse, we show in vivo that bazedoxifene can activate the ERE in the brain. The evidence shown here suggest bazedoxifene could be a viable cognitive enhancer with promising clinical applicability.

Cobalt-catalyzed intramolecular decarbonylative coupling of acylindoles and diarylketones through the cleavage of C-C bonds

We report here cobalt-N-heterocyclic carbene catalytic systems for the intramolecular decarbonylative coupling through the chelation-assisted C-C bond cleavage of acylindoles and diarylketones. The reaction tolerates a wide range of functional groups such as alkyl, aryl, and heteroaryl groups, giving the decarbonylative products in moderate to excellent yields. This transformation involves the cleavage of two C-C bonds and formation of a new C-C bond without the use of noble metals, thus reinforcing the potential application of decarbonylation as an effective tool for C-C bond formation.

Screening and Reverse-Engineering of Estrogen Receptor Ligands as Potent Pan-Filovirus Inhibitors

Filoviridae, including Ebola (EBOV) and Marburg (MARV) viruses, are emerging pathogens that pose a serious threat to public health. No agents have been approved to treat filovirus infections, representing a major unmet medical need. The selective estrogen receptor modulator (SERM) toremifene was previously identified from a screen of FDA-approved drugs as a potent EBOV viral entry inhibitor, via binding to EBOV glycoprotein (GP). A focused screen of ER ligands identified ridaifen-B as a potent dual inhibitor of EBOV and MARV. Optimization and reverse-engineering to remove ER activity led to a novel compound 30 (XL-147) showing potent inhibition against infectious EBOV Zaire (0.09 μM) and MARV (0.64 μM). Mutagenesis studies confirmed that inhibition of EBOV viral entry is mediated by the direct interaction with GP. Importantly, compound 30 displayed a broad-spectrum antifilovirus activity against Bundibugyo, Tai Forest, Reston, and Měnglà viruses and is the first submicromolar antiviral agent reported for some of these strains, therefore warranting further development as a pan-filovirus inhibitor.

Monitoring ligand-mediated helix 12 transitions within the human estrogen receptor α using bipartite tetracysteine display

Estrogen receptor α ligand-binding domains (ERα-LBD) expressing tetracysteine motifs bind FlAsH-EDT₂ upon transition of helix 12 (H12) to a folded state. Changes in fluorescence intensity allowed surveillance of ligand-mediated H12 transitions and facilitated the determination of FlAsH association rates (k_on) and apparent equilibrium dissociation constants (K_app) to ERα-LBDs in the presence of estrogenic ligands.

Blocking IL-6/GP130 Signaling Inhibits Cell Viability/Proliferation, Glycolysis, and Colony Forming Activity in Human Pancreatic Cancer Cells

BACKGROUND

Elevated production of the pro-inflammatory cytokine interleukin-6 (IL-6) and dysfunction of IL-6 signaling promotes tumorigenesis and are associated with poor survival outcomes in multiple cancer types. Recent studies showed that the IL-6/GP130/STAT3 signaling pathway plays a pivotal role in pancreatic cancer development and maintenance.

OBJECTIVE

We aim to develop effective treatments through inhibition of IL-6/GP130 signaling in pancreatic cancer.

METHODS

The effects on cell viability and cell proliferation were measured by MTT and BrdU assays, respectively. The effects on glycolysis was determined by cell-based assays to measure lactate levels. Protein expression changes were evaluated by western blotting and immunoprecipitation. siRNA transfection was used to knock down estrogen receptor α gene expression. Colony forming ability was determined by colony forming cell assay.

RESULTS

We demonstrated that IL-6 can induce pancreatic cancer cell viability/proliferation and glycolysis. We also showed that a repurposing FDA-approved drug bazedoxifene could inhibit the IL-6/IL-6R/GP130 complexes. Bazedoxifene also inhibited JAK1 binding to IL-6/IL-6R/GP130 complexes and STAT3 phosphorylation. In addition, bazedoxifene impeded IL-6 mediated cell viability/ proliferation and glycolysis in pancreatic cancer cells. Consistently, other IL-6/GP130 inhibitors SC144 and evista showed similar inhibition of IL-6 stimulated cell viability, cell proliferation and glycolysis. Furthermore, all three IL-6/GP130 inhibitors reduced the colony forming ability in pancreatic cancer cells.

CONCLUSION

Our findings demonstrated that IL-6 stimulates pancreatic cancer cell proliferation, survival and glycolysis, and supported persistent IL-6 signaling is a viable therapeutic target for pancreatic cancer using IL-6/GP130 inhibitors.

Postmenopausal hormone therapy in BRCA gene mutation carriers: to whom and which?

INTRODUCTION

Risk-reducing-salpingo-oophorectomy (RRSO) inevitably leads BRCA mutation carriers to premature menopause.

AREAS COVERED

To evaluate the existing evidence for use of postmenopausal hormone therapy (HT) in BRCAmc, after RRSO or menopause occurring naturally, for both breast cancer (BC) survivors and those without BC.

EXPERT OPINION

All BC survivors are excluded from any HT treatment: in other BRCAmc, before 51 years of age the benefits of HT overcome the risks after RRSO and/or premature ovarian insufficiency (POF). After 51 years of age, it is important to treat only women with important vasomotor symptoms, after the failure of alternative therapies. Estrogens-only therapy plays a key role in hysterectomized women (HW). In the case of an intact uterus (UW), associations with the lowest dose of progestins/natural progesterone derivatives have to be preferred, as progestins has been shown to play an important role in BC transformation, especially in BRCA1mc. No studies have been performed in BRCAmc with regard to 'progestin-free' HT, in particular the old tibolone (both in HW and UW) and the new tissue-selective estrogen complex (in UW). However, preliminary data obtained from the general population are reassuring about the use of these 'progestin-free' preparations and BC safety.

Pharmacokinetic comparison of two bazedoxifene acetate 20 mg tablet formulations in healthy Korean male volunteers

Bazedoxifene, used as bazedoxifene acetate, is a selective estrogen receptor modulator that selectively affects the uterus, breast tissue, bone metabolism, and lipid metabolism by antagonizing or enhancing estrogens in the estrogen receptor in the tissue. This study was conducted as an open, randomized, two-period, two-treatment, crossover design to compare the pharmacokinetic (PK) characteristics and tolerability of two bazedoxifene tablets when administered to 50 healthy Korean male volunteers. Enrolled subjects were randomly allocated to 2 sequences of a single oral administration of a test drug and a reference drug, or vice versa with a 14-day washout period between the two doses. Serial blood samples were collected over 96 h for PK analysis. Plasma concentration of bazedoxifene was assayed using liquid chromatography-tandem spectrometry mass. Forty-five participants completed the study with no clinically relevant safety issues. The peak concentrations (C_max, mean ± strandard deviation) of reference drug and test drug were 3.191 ± 1.080 and 3.231 ± 1.346 ng/mL, respectively, and the areas under the plasma concentration‐time curve from 0 to the last measurable concentration (AUC_last) were 44.697 ± 21.168 ng∙h/mL and 45.902 ± 23.130 ng∙h/mL, respectively. The geometric mean ratios of test drug to reference drug and their 90% confidence intervals for C_max and AUC_last were 0.9913 (0.8828–1.1132) and 1.0106 (0.9345–1.0929), respectively. The incidence of adverse events between the two formulations was similar. The present study showed that PK and tolerability of two bazedoxifene tablet formulations were comparable when administered to healthy Korean male volunteers.

Computer-Aided Ligand Discovery for Estrogen Receptor Alpha

Breast cancer (BCa) is one of the most predominantly diagnosed cancers in women. Notably, 70% of BCa diagnoses are Estrogen Receptor α positive (ERα+) making it a critical therapeutic target. With that, the two subtypes of ER, ERα and ERβ, have contrasting effects on BCa cells. While ERα promotes cancerous activities, ERβ isoform exhibits inhibitory effects on the same. ER-directed small molecule drug discovery for BCa has provided the FDA approved drugs tamoxifen, toremifene, raloxifene and fulvestrant that all bind to the estrogen binding site of the receptor. These ER-directed inhibitors are non-selective in nature and may eventually induce resistance in BCa cells as well as increase the risk of endometrial cancer development. Thus, there is an urgent need to develop novel drugs with alternative ERα targeting mechanisms that can overcome the limitations of conventional anti-ERα therapies. Several functional sites on ERα, such as Activation Function-2 (AF2), DNA binding domain (DBD), and F-domain, have been recently considered as potential targets in the context of drug research and discovery. In this review, we summarize methods of computer-aided drug design (CADD) that have been employed to analyze and explore potential targetable sites on ERα, discuss recent advancement of ERα inhibitor development, and highlight the potential opportunities and challenges of future ERα-directed drug discovery.

Overcoming Endocrine Resistance in Breast Cancer

Estrogen receptor-positive (ER+) breast cancer is the most common breast cancer subtype. Treatment of ER+ breast cancer comprises interventions that suppress estrogen production and/or target the ER directly (overall labeled as endocrine therapy). While endocrine therapy has considerably reduced recurrence and mortality from breast cancer, de novo and acquired resistance to this treatment remains a major challenge. An increasing number of mechanisms of endocrine resistance have been reported, including somatic alterations, epigenetic changes, and changes in the tumor microenvironment. Here, we review recent advances in delineating mechanisms of resistance to endocrine therapies and potential strategies to overcome such resistance.

Bazedoxifene Suppresses Intracellular Mycobacterium tuberculosis Growth by Enhancing Autophagy

Since current strategies for the treatment of multidrug-resistant tuberculosis (MDR-TB) and extensively drug-resistant tuberculosis (XDR-TB) have low efficacy and highly negative side effects, research on new treatments including novel drugs is essential for curing drug-resistant tuberculosis. Host-directed therapy (HDT) has become a promising idea to modulate host cell responses to enhance protective immunity against pathogens. Bazedoxifene (BZA), which belongs to a new generation of SERMs, shows the ability to inhibit the growth of M. tuberculosis in macrophages and is associated with autophagy. Our findings reveal a previously unrecognized antibacterial function of BZA. We propose that the mechanism of SERMs action in macrophages may provide a new potential measure for host-directed therapies against TB.

Tuberculosis (TB) is still the leading killer caused by Mycobacterium tuberculosis infection. There is a clear need for new treatment strategy against TB. It has been reported that tamoxifen, known as a selective estrogen receptor modulator (SERM), exhibits antimycobacterial activity and inhibits M. tuberculosis growth in macrophages. However, it remains unknown whether such antimicrobial activity is a general property of all SERMs and how it works. In this study, we identified that bazedoxifene (BZA), a newer SERM, inhibits intracellular M. tuberculosis growth in macrophages. BZA treatment increases autophagosome formation and LC3B-II protein expression in M. tuberculosis-infected macrophages. We further demonstrated that the enhancement of autophagy by BZA is dependent on increased reactive oxygen species (ROS) production and associated with phosphorylation of Akt/mTOR signaling. In summary, our data reveal a previously unappreciated antimicrobial function of BZA and suggest that future investigation focusing on the mechanism of action of SERMs in macrophages may lead to new host-directed therapies against TB.

IMPORTANCE Since current strategies for the treatment of multidrug-resistant tuberculosis (MDR-TB) and extensively drug-resistant tuberculosis (XDR-TB) have low efficacy and highly negative side effects, research on new treatments including novel drugs is essential for curing drug-resistant tuberculosis. Host-directed therapy (HDT) has become a promising idea to modulate host cell responses to enhance protective immunity against pathogens. Bazedoxifene (BZA), which belongs to a new generation of SERMs, shows the ability to inhibit the growth of M. tuberculosis in macrophages and is associated with autophagy. Our findings reveal a previously unrecognized antibacterial function of BZA. We propose that the mechanism of SERMs action in macrophages may provide a new potential measure for host-directed therapies against TB.

Tissue selective estrogen complex (TSEC): a review

Objective:

This review describes historical development of selective estrogen receptor modulators (SERMs) and their combination with estrogens, termed a tissue selective estrogen complex (TSEC), and considers the potential for future TSEC development.

Methods:

This narrative review is based on literature identified on PubMed and the TSEC research and development experience of the authors.

Results:

SERMs have estrogenic and antiestrogenic effects in various tissues; however, no single agent has achieved an optimal balance of agonist and antagonist effects for the treatment of menopausal symptoms. Clinically, a number of SERMs protect against osteoporosis and breast cancer but can exacerbate vasomotor symptoms. Estrogens alleviate menopausal hot flushes and genitourinary symptoms as well as reduce bone loss, but the addition of a progestogen to menopausal hormone therapy to protect against endometrial cancer increases vaginal bleeding risk, breast tenderness, and potentially breast cancer. The search for an effective menopausal therapy with better tolerability led to the investigation of TSECs. Clinical development of a TSEC consisting of conjugated estrogens/bazedoxifene increased understanding of the importance of a careful consideration of the combination's components and their respective doses to balance safety and efficacy. Bazedoxifene is an estrogen receptor agonist in bone but an antagonist/degrader in the endometrium, which has contributed to its success as a TSEC component. Other oral TSEC combinations studied thus far have not demonstrated similar endometrial safety.

Conclusions:

Choice of SERM, selection of doses, and clinical trial data evaluating safety and efficacy are key to ensuring safety and adequate therapeutic effect of TSECs for addressing menopausal symptoms.

Bazedoxifene Ameliorates Homocysteine-Induced Apoptosis via NADPH Oxidase-Interleukin 1β and 6 Pathway in Osteocyte-like Cells

Homocysteine (Hcy) increases oxidation and inflammation; however, the mechanism of Hcy-induced bone fragility remains unclear. Because selective estrogen modulators (SERMs) have an anti-oxidative effect, SERMs may rescue the Hcy-induced bone fragility. We aimed to examine whether oxidative stress and pro-inflammatory cytokines such as interleukin (IL)-1β and IL-6 are involved in the Hcy-induced apoptosis of osteocytes and whether bazedoxifene (BZA) inhibits the detrimental effects of Hcy. We used mouse osteocyte-like cell lines MLO-Y4-A2 and Ocy454. Apoptosis was examined by DNA fragmentation ELISA and TUNEL staining, and gene expression was evaluated by real-time PCR. Hcy 5 mM significantly increased expressions of NADPH oxidase (Nox)1, Nox2, IL-1β, and IL-6 as well as apoptosis in MLO-Y4-A2 cells. Nox inhibitors, diphenyleneiodonium chloride and apocynin, significantly suppressed Hcy-induced IL-1β and IL-6 expressions. In contrast, an IL-1β receptor antagonist and an IL-6 receptor monoclonal antibody had no effects on Hcy-induced Nox1 and Nox2 expressions, but significantly rescued Hcy-induced apoptosis. BZA (1 nM-1 μM) and 17β estradiol 100 nM significantly rescued Hcy-induced apoptosis, while an estrogen receptor blocker ICI 182,780 reversed the effects of BZA and 17β estradiol. BZA also rescued Hcy-induced apoptosis of Ocy454 cell, and ICI canceled the effect of BZD. Moreover, BZA significantly ameliorated Hcy-induced expressions of Nox1, Nox2, IL-1β, and IL-6, and ICI canceled the effects of BZA on their expressions. Hcy increases apoptosis through stimulating Nox 1 and Nox 2-IL-1β and IL-6 expressions in osteocyte-like cells. BZA inhibits the detrimental effects of Hcy on osteocytes via estrogen receptor.

Initial investigation into the optimal dose ratio of conjugated estrogens and bazedoxifene: a double-blind, randomized, placebo-controlled phase 2 dose-finding study

OBJECTIVE

The aim of the study was to explore dose-related endometrial effects of conjugated estrogens/bazedoxifene (CE/BZA).

METHODS

In this randomized, double-blind, phase 2 study, 408 nonhysterectomized, symptomatic (with hot flushes [HFs]) postmenopausal women received ≥1 dose of CE 0.3 or 0.625 mg alone or with BZA 5, 10, or 20 mg/d; placebo; BZA 5 mg/d alone; or CE 0.625 mg with medroxyprogesterone acetate 2.5 mg/d for 84 days. The primary outcome was endometrial thickness on transvaginal ultrasound. HF frequency and severity based on diaries were key secondary outcomes.

RESULTS

CE 0.625 mg alone increased endometrial thickness compared with placebo (mean 5.5 vs 2.95 mm, P < 0.001); BZA countered this in a dose-related manner such that average thickness with the addition of BZA 5, 10, and 20 mg was 5.99, 4.33, and 3.54 mm, respectively. On average, endometrium was significantly less thick with CE 0.625 mg/BZA 20 mg than CE 0.625 mg (P < 0.001) and CE 0.3 mg/BZA 20 mg versus CE 0.3 mg (2.94 vs 3.92 mm, P < 0.05); endometrial thickness was similar to placebo with CE 0.625 mg/BZA 20 mg. Lower BZA doses failed to reduce endometrial thickness relative to the same dose of CE alone. Regimens containing CE 0.625 mg reduced HF frequency and severity versus placebo; CE 0.3 mg with BZA 10 or 20 mg was ineffective.

CONCLUSIONS

BZA ≥20 mg is needed to counter endometrial growth resulting from treatment with CE 0.3 or 0.625 mg. CE 0.3 mg inadequately controls HFs if given with BZA 20 mg.

Estrogen-SIRT1 Axis Plays a Pivotal Role in Protecting Arteries Against Menopause-Induced Senescence and Atherosclerosis

Aim: Menopause causes arterial senescence and atherosclerotic development through decrease of estrogen. Recently, histone deacetylase SIRT1 has been reported to have protective effects against arterial senescence and atherosclerosis. However, the relationship between estrogen and SIRT1 in the context of menopause-induced arterial senescence is not well understood. The present study aims to investigate whether SIRT1 is involved in the etiology of menopause-induced arterial senescence and atherosclerotic development.

Methods: Twelve-week old female apolipoprotein E-knockout (ApoE-KO) mice underwent ovariectomy (OVX) or sham surgery.

Results: SIRT1 expression and endothelial nitric oxide synthase (eNOS) activation in the aorta were significantly lower in OVX mice than they were in sham mice (OVX vs. sham, n = 5 per group). Senescence-associated β-galactosidase activity, protein expression of Ac-p53 and PAI-1, and aortic atherosclerosis lesions were significantly greater in OVX mice than they were in sham mice. Administration of 17β-estradiol (E2) for eight weeks to OVX mice restored aortic SIRT1 expression, activated eNOS, and retarded OVX-induced arterial senescence and atherosclerotic development (E2 vs. control, n = 5 per group). The effects of E2 on SIRT1 upregulation, anti-senescence and anti-atherosclerosis were attenuated by administration of a SIRT1 inhibitor, sirtinol. In vitro experiment using human endothelial cells demonstrated that E2 also increased SIRT1 expression and retarded oxidized low density lipoprotein-induced premature senescence, which were also abolished by sirtinol. These results suggested that estrogen modulated arterial senescence and atherosclerosis through SIRT1. Additionally a selective estrogen receptor modulator (SERM), bazedoxifene, also augmented SIRT1 and inhibited arterial senescence and atherosclerotic development (SERM vs. control, n = 3 per group).

Conclusions: Downregulation of SIRT1 causes OVX-induced arterial senescence and atherosclerosis in ApoE-KO mice. Administration of estrogen or SERM enables OVX mice to restore these alterations by SIRT1 induction.

Bazedoxifene for the treatment of osteoporosis

Introduction: Bazedoxifene (BZD) is a third-generation selective estrogen receptor modulator approved for the treatment of postmenopausal osteoporosis with additional favorable effects in lipids, uterine and breast tissue. Areas covered: In this review, the authors outline clinical data regarding the efficacy, safety, and tolerability of continuous BZD administration up to seven years in randomized, placebo-controlled, phase III clinical trials. Long-term treatment with BZD for postmenopausal osteoporosis is generally safe and well tolerated. BZD achieves small but significant increases in the bone mineral density of the lumbar spine but not the total hip. In addition, BZD reduces significantly the risk of vertebral fractures but not of non-vertebral and hip fractures, with the exception of high fracture risk postmenopausal women in whom BZD significantly reduces non-vertebral fractures. Expert opinion: BZD does not seem to offer significant advantages over the other available antiresorptive agents. However, considering the need for long-term management of osteoporosis, BZD may have a place in the long-term therapeutic planning of the disease.

Estrogen signaling: An emanating therapeutic target for breast cancer treatment

Breast cancer, a most common malignancy in women, was known to be associated with steroid hormone estrogen. The discovery of estrogen receptor (ER) gave us not only a powerful predictive and prognostic marker, but also an efficient target for the treatment of hormone-dependent breast cancer with various estrogen ligands. ER consists of two subtypes i.e. ERα and ERβ, that are mostly G-protein-coupled receptors and activated by estrogen, specially 17β-estradiol. The activation is followed by translocation into the nucleus and binding with DNA to modulate activities of different genes. ERs can manage synthesis of RNA through genomic actions without directly binding to DNA. Receptors are tethered by protein-protein interactions to a transcription factor complex to communicate with DNA. Estrogens also exhibit nongenomic actions, a characteristic feature of steroid hormones, which are so rapid to be considered by the activation of RNA and translation. These are habitually related to stimulation of different protein kinase cascades. Majority of post-menopausal breast cancer is estrogen dependent, mostly potent biological estrogen (E2) for continuous growth and proliferation. Estrogen helps in regulating the differentiation and proliferation of normal breast epithelial cells. In this review we have investigated the important role of ER in development and progression of breast cancer, which is complicated by receptor's interaction with co-regulatory proteins, cross-talk with other signal transduction pathways and development of treatment strategies viz. selective estrogen receptor modulators (SERMs), selective estrogen receptor down regulators (SERDs), aromatase and sulphatase inhibitors.

Identification of 10-dehydrooxyglycyuralin E as a selective human estrogen receptor alpha partial agonist

Selective estrogen receptor modulators (SERMs) act as either agonist or antagonist of estrogen receptor (ER) in a tissue selective manner and have been used in several diseases such as breast cancer, postmenopausal syndrome, osteoporosis, and cardiovascular diseases. However, current SERMs may also increase the risk of serious side effects and trigger drug resistance. Herein, a screening program, that was designed to search for novel SERMs, resulted in the identification of a series of 2-arylbenzofuran-containing compounds that are ligands for ERα, when applying the Gaussia-luciferase reporter assay. One of these compounds, 10-dehydrooxyglycyuralin E (T9) was chemically synthesized. T9 showed anti-estrogenic/proliferative activity in ERα-positive breast cancer cells. Pretreatment of T9 prevented the mRNA expression of GREB1, which is an estrogen response gene. Furthermore, by an in silico docking simulation study we demonstrated that T9 showed interactions directly to ERα. Taken together, these results demonstrated that T9 is a candidate of SERMs and a useful seed compound for the foundation of the selective activity of SERMs.

Current and emerging osteoporosis pharmacotherapy for women: state of the art therapies for preventing bone loss

INTRODUCTION

Pharmacological options to address the imbalance between bone resorption and accrual in osteoporosis include anti-resorptive and osteoanabolic agents. Unique biologic pathways such as the Wnt/β-catenin pathway have been targeted in the quest for new emerging therapeutic strategies.

AREAS COVERED

This review provides an overview of existing pharmacotherapy for osteoporosis in women and explore state-of-the-art and emerging therapies to prevent bone loss, with an emphasis on the mechanism of action, indications and side effects.

EXPERT OPINION

Bisphosphonates appear to be a reliable and cost-effective option, whereas denosumab has introduced a simpler dosing regimen and may achieve a linear increase in bone mineral density (BMD) with no plateau being observed, along with continuous anti-fracture efficacy. Abaloparatide, a parathyroid-hormone-related peptide (PTHrP)-analogue, approved by the FDA in April 2017, constitutes the first new anabolic osteoporosis drug in the US for nearly 15 years and has also proven its anti-fracture efficacy. Romosozumab, a sclerostin inhibitor, which induces bone formation and suppresses bone resorption, has also been developed and shown a significant reduction in fracture incidence; however, concerns have arisen with regard to increased cardiovascular risk.