Dual-target inhibitors based on ERα: Novel therapeutic approaches for endocrine resistant breast cancer.

Estrogen receptor alpha (ERα), a nuclear transcription factor, is a well-validated therapeutic target for more than 70% of all breast cancers (BCs). Antagonizing ERα either by selective estrogen receptor modulators (SERMs) or selective estrogen receptor degraders (SERDs) forms the foundation of endocrine therapy and has achieved great success in the treatment of ERα positive (ERα+) BCs. Unfortunately, despite initial effectiveness, endocrine resistance eventually emerges in up to 30% of ERα+ BC patients and remains a significant medical challenge. Several mechanisms implicated in endocrine resistance have been extensively studied, including aberrantly activated growth factor receptors and downstream signaling pathways. Hence, the crosstalk between ERα and another oncogenic signaling has led to surge of interest to develop combination therapies and dual-target single agents. This review briefly introduces the synergisms between ERα and another anticancer target and summarizes the recent advances of ERα-based dual-targeting inhibitors from a medicinal chemistry perspective. Accordingly, their rational design strategies, structure-activity relationships (SARs) and biological activities are also dissected to provide some perspectives on future directions for ERα-based dual target drug discovery in BC therapy.

Maternal immune activation and estrogen receptor modulation induce sex-specific dopamine-related behavioural and molecular alterations in adult rat offspring.

Dopamine dysregulation contributes to psychosis and cognitive deficits in schizophrenia that can be modelled in rodents by inducing maternal immune activation (MIA). The selective estrogen receptor (ER) modulator, raloxifene, can improve psychosis and cognition in men and women with schizophrenia. However, few studies have examined how raloxifene may exert its therapeutic effects in mammalian brain in both sexes during young adulthood (age relevant to most prevalent age at diagnosis). Here, we tested the extent to which raloxifene alters dopamine-related behaviours and brain transcripts in young adult rats, both control and MIA-exposed females and males. We found that raloxifene increased amphetamine (AMPH)-induced locomotor activity in female controls, and in contrast, raloxifene reduced AMPH-induced locomotor activity in male MIA offspring. We did not detect overt prepulse inhibition (PPI) deficits in female or male MIA offspring, yet raloxifene enhanced PPI in male MIA offspring. Whereas, raloxifene ameliorated increased startle responsivity in female MIA offspring. In the substantia nigra (SN), we found reduced Drd2s mRNA in raloxifene-treated female offspring with or without MIA, and increased Comt mRNA in placebo-treated male MIA offspring relative to placebo-treated controls. These data demonstrate an underlying dopamine dysregulation in MIA animals that can become more apparent with raloxifene treatment, and may involve selective alterations in dopamine receptor levels and dopamine breakdown processes in the SN. Our findings support sex-specific, differential behavioural responses to ER modulation in MIA compared to control offspring, with beneficial effects of raloxifene treatment on dopamine-related behaviours relevant to schizophrenia found in male MIA offspring only.

Pharmacological insights on novel oral selective estrogen receptor degraders in breast cancer.

The therapeutic landscape of estrogen receptor (ER)-positive breast cancer includes endocrine treatments with aromatase inhibitors (AIs), selective estrogen receptor modulators (SERMs), and selective estrogen receptor degraders (SERDs). Fulvestrant is the first approved SERD with proven efficacy and good tolerability in clinical practice. However, drug resistance, low receptor affinity, and parental administration stimulated the search for new oral SERDs opening a new therapeutic era in ER + breast cancer. Elacestrant is an orally bioavailable SERD that has been recently approved by the FDA for postmenopausal women with ER+, human epidermal growth factor receptor 2-negative (HER2-), estrogen receptor 1 (ESR1)-mutated advanced or metastatic breast cancer with disease progression following at least one line of endocrine therapy. Other molecules of the same class currently tested in clinical trials are amcenestrant, giredestrant, camizestrant, and imlunestrant. The current review article offers a detailed pharmacological perspective of this emerging drug class, which may help with their possible future clinical applications.

Investigation of the potential effects of estrogen receptor modulators on immune checkpoint molecules.

Immune checkpoints regulate the immune system response. Recent studies suggest that flavonoids, known as phytoestrogens, may inhibit the PD-1/PD-L1 axis. We explored the potential of estrogens and 17 Selective Estrogen Receptor Modulators (SERMs) as inhibiting ligands for immune checkpoint proteins (CTLA-4, PD-L1, PD-1, and CD80). Our docking studies revealed strong binding energy values for quinestrol, quercetin, and bazedoxifene, indicating their potential to inhibit PD-1 and CTLA-4. Quercetin and bazedoxifene, known to modulate EGFR and IL-6R alongside estrogen receptors, can influence the immune checkpoint functionality. We discuss the impact of SERMs on PD-1 and CTLA-4, suggesting that these SERMs could have therapeutic effects through immune checkpoint inhibition. This study highlights the potential of SERMs as inhibitory ligands for immune checkpoint proteins, emphasizing the importance of considering PD-1 and CTLA-4 inhibition when evaluating SERMs as therapeutic agents. Our findings open new avenues for cancer immunotherapy by exploring the interaction between various SERMs and immune checkpoint pathways.

A novel scaffold long-acting selective estrogen receptor antagonist and degrader with superior preclinical profile against ER+ breast cancer.

Breast cancer is one of the most common malignant tumors in women worldwide, with the majority of cases showing expression of estrogen receptors (ERs). Although drugs targeting ER have significantly improved survival rates in ER-positive patients, drug resistance remains an unmet clinical need. Fulvestrant, which overcomes selective estrogen receptor modulator (SERM) and AI (aromatase inhibitor) resistance, is currently the only long-acting selective estrogen receptor degrader (SERD) approved for both first and second-line settings. However, it fails to achieve satisfactory efficacy due to its poor solubility. Therefore, we designed and synthesized a series of novel scaffold (THC) derivatives, identifying their activities as ER antagonists and degraders. G-5b, the optimal compound, exhibited binding, antagonistic, degradation or anti-proliferative activities comparable to fulvestrant in ER+ wild type and mutants breast cancer cells. Notably, G-5b showed considerably improved stability and solubility. Research into the underlying mechanism indicated that G-5b engaged the proteasome pathway to degrade ER, subsequently inhibiting the ER signaling pathway and leading to the induction of apoptosis and cell cycle arrest events. Furthermore, G-5b displayed superior in vivo pharmacokinetics and pharmacodynamics properties, coupled with a favorable safety profile in the MCF-7 tamoxifen-resistant (MCF-7/TR) tumor xenograft model. Collectively, G-5b has emerged as a highly promising lead compound, offering potent antagonistic and degradation activities, positioning it as a novel long-acting SERD worthy of further refinement and optimization.

Design, synthesis, and in-silico study of novel triarylethylene analogs with dual anti-estrogenic and serotonergic activity.

Estrogen receptor is an important target in breast cancer. Serotonin receptors (5-HT2A and 5-HT2C , in particular) were investigated for a potential role in development and progression of breast cancer. Ligands that interact with estrogenic receptors influence the emotional state of females. Thus, designing selective estrogen receptor modulator (SERM) analogs with potential serotonergic activity is a plausible approach. The dual ligands can augment cytotoxic effect of SERMs, help in both physical and emotional menopausal symptom relief, enhance cognitive function and support bone health. Herein, we report triarylethylene analogs as potential candidates for treatment of breast cancer. Compound 2e showed (ERα relative ß- galactosidase activity = 0.70), 5-HT2A (Ki = 0.97 µM), and 5-HT2C (Ki = 3.86 µM). It was more potent on both MCF-7 (GI50 = 0.27 µM) and on MDA-MB-231 (GI50 = 1.86 µM) compared to tamoxifen (TAM). Compound 4e showed 40 times higher antiproliferative activity on MCF-7 and 15 times on MDA-MBA compared to TAM. Compound 4e had higher average potency than TAM on all nine tested cell line panels. Our in-silico model revealed the binding interactions of compounds 2 and 2e in the three receptors; further structural modifications are suggested to optimize binding to the ERα, 5-HT2A , and 5-HT2C .

Complete elimination of estrogen receptor α by PROTAC estrogen receptor α degrader ERD-148 in breast cancer cells.

PURPOSE: Estrogen Receptor α (ERα) is a well-established therapeutic target for Estrogen Receptor (ER)-positive breast cancers. Both Selective Estrogen Receptor Degraders (SERD) and PROTAC ER degraders are synthetic compounds suppressing the ER activity through the degradation of ER. However, the differences between SERD and PROTAC ER degraders are far from clear. METHODS: The effect of PROTAC ER degrader ERD-148 and SERD fulvestrant on protein degradation was evaluated by western blot analysis. The cell proliferation was tested by WST-8 assays and the gene expressions were assessed by gene microarray and real-time RT-PCR analysis after the compound treatment. RESULTS: ERD-148 is a potent and selective PROTAC ERα degrader. It degrades not only unphosphorylated ERα but also the phosphorylated ERα in the cells. In contrast, the SERD fulvestrant showed much-reduced degradation potency on the phosphorylated ERα. The more complete degradation of ERα by ERD-148 translates into a greater maximum cell growth inhibition. However, ERD-148 and fulvestrant share a similar gene regulation profile except for the variation of regulation potency. Further studies indicate that ERD-148 degrades the ERα in fulvestrant-resistant cells. CONCLUSION: PROTAC ER degrader has a different mechanism of action compared to SERD which may be used in treating fulvestrant-resistant cancers.

Research progress on tamoxifen and its analogs associated with nuclear receptors.

Tamoxifen, a triphenylethylene-based selective estrogen-receptor modulator, is a landmark drug for the treatment of breast cancer and is also used for treating liver cancer and osteoporosis. Structural studies of tamoxifen have led to the synthesis of more than 20 novel tamoxifen analogs as receptor modulators, including 16 ERα modulators 2-17, an ERRß inverse agonist 19 and six ERRγ inverse agonists 20-25. This paper summarizes the research progress and structure-activity relationships of tamoxifen analogs modulating these three nuclear receptors reported in the literature, and introduces the relationship between these three nuclear receptor-mediated diseases and tamoxifen analogs to guide the research of novel tamoxifen analogs.

The immune activity of selective estrogen receptor modulators is gene and macrophage subtype-specific yet converges on Il1b downregulation.

Raloxifene belongs to the family of Selective Estrogen Receptor Modulators (SERMs), which are drugs widely prescribed for Estrogen Receptor alpha (ERα)-related pathologies. Recently, SERMs are being tested in repurposing strategies for ERα-independent clinical indications, including a wide range of microbial infections. Macrophages are central in the fight against pathogen invasion. Despite estrogens have been shown to regulate macrophage phenotype, SERMs activity in these cells is still poorly defined. We investigated the activity of Raloxifene in comparison with another widely used SERM, Tamoxifen, on immune gene expression in macrophages obtained from mouse and human tissues, including mouse peritoneal macrophages, bone marrow-derived macrophages, microglia or human blood-derived macrophages, assaying for the involvement of the ERα, PI3K and NRF2 pathways also under inflammatory conditions. Our data demonstrate that Raloxifene acts by a dual mechanism, which entails ERα antagonism and off-target mediators. Moreover, micromolar concentrations of Raloxifene increase the expression of immune metabolic genes, such as Vegfa and Hmox1, through PI3K and NRF2 activation selectively in peritoneal macrophages. Conversely, Il1b mRNA down-regulation by SERMs is consistently observed in all macrophage subtypes and unrelated to the PI3K/NRF2 system. Importantly, the production of the inflammatory cytokine TNFα induced by the bacterial endotoxin, LPS, is potentiated by SERMs and paralleled by the cell subtype-specific increase in IL1ß secretion. This work extends our knowledge on the biological and molecular mechanisms of SERMs immune activity and indicate macrophages as a pharmacological target for the exploitation of the antimicrobial potential of these drugs.

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.

Targeting the Estrogen Receptor for the Treatment of Breast Cancer: Recent Advances and Challenges.

Estrogen receptor alpha (ERα) is a well-established therapeutic target for the treatment of ER-positive (ER+) breast cancers. Despite the tremendous successes achieved with tamoxifen, a selective ER modulator, and aromatase inhibitors (AIs), resistance to these therapies is a major clinical problem. Therefore, induced protein degradation and covalent inhibition have been pursued as new therapeutic approaches to target ERα. This Perspective summarizes recent progress in the discovery and development of oral selective ER degraders (SERDs), complete estrogen receptor antagonists (CERANs), selective estrogen receptor covalent antagonists (SERCAs), and proteolysis targeting chimera (PROTAC) ER degraders. We focus on those compounds which have been advanced into clinical development.

Cardioprotective effect of tamoxifen and raloxifene: Preventing proteoglycan synthesis by modulating non-canonical TGF-ß signalling through NADPH oxidase and ERK phosphorylation.

Atherosclerosis, a leading cause of cardiovascular disease, remains a significant global health concern. Tamoxifen and raloxifene, selective estrogen receptor modulators (SERMs), have demonstrated potential cardioprotective effects. However, the underlying molecular mechanisms by which these SERMs modulate Transforming Growth Factor-ß (TGF-ß) signaling in human vascular smooth muscle cells (VSMCs) remain largely unexplored. This study sought to investigate the impact of tamoxifen and raloxifene on TGF-ß-induced CHSY1 expression and Smad2 linker region phosphorylation in VSMCs and to elucidate the role of reactive oxygen species (ROS), NADPH oxidase (NOX), and kinase pathways in mediating these effects. Employing a comprehensive experimental strategy, VSMCs were treated with TGF-ß in the presence or absence of tamoxifen, raloxifene, and various pharmacological inhibitors. Subsequently, CHSY1 mRNA expression, Smad2C and Smad2L phosphorylation, ROS production, p47phox and ERK 1/2 phosphorylation were assessed. Our results revealed that tamoxifen and raloxifene significantly attenuated TGF-ß-mediated CHSY1 mRNA expression and Smad2 linker region phosphorylation, without affecting the canonical TGF-ß-Smad2C pathway. Furthermore, these compounds effectively inhibited ROS production, p47phox and ERK 1/2 phosphorylation, implicating the involvement of the TGF-ß-NOX-ERK-Smad2L signaling cascade in their cardioprotective properties. This study provides a comprehensive understanding of the molecular mechanisms underlying the cardioprotective effects of tamoxifen and raloxifene in VSMCs, offering valuable insights for the development of targeted therapeutic strategies aimed at atherosclerosis prevention and the promotion of cardiovascular health.

[Research Progress in the Role of Tamoxifen in Nervous System and Cognitive Function].

Neurological diseases include a variety of neurodegenerative diseases and other brain damage diseases.The treatment schemes for neurological diseases are still in research.The existing clinical and basic studies have confirmed that traditional estrogen therapy has certain protective effect on the nervous system,while it increases the risk of breast or endometrial cancer.The emergence of the selective estrogen receptor modulators (SERMs) can avoid the above mentioned problems.The available studies have confirmed the protective effect of tamoxifen as a SERM on the nervous system.This paper reviews the role and functioning mechanisms of tamoxifen in the nervous system and cognitive function,aiming to provide guidance for the future application of tamoxifen in the treatment of neurological diseases and the improvement of cognitive function.

Selective Estrogen receptor degraders (SERDs) for the treatment of breast cancer: An overview.

Discovery of SERDs has changed the direction of anticancer research, as more than 70% of breast cancer cases are estrogen receptor positive (ER+). Therapies such as selective estrogen receptor modulators (SERM) and aromatase inhibitors (AI's) have been effective, but due to endocrine resistance, SERDs are now considered essential therapeutics for the treatment of ER+ breast cancer. The present review deliberates the pathophysiology of SERDs from the literature covering various molecules in clinical trials. Estrogen receptors active sites distinguishing characteristics and interactions with currently available FDA-approved drugs have also been discussed. Designing strategy of previously reported SERDs, their SAR analysis, in silico, and the biological efficacy have also been summarized along with appropriate examples.

Bazedoxifene does not share estrogens effects on IgG sialylation.

The incidence of rheumatoid arthritis (RA) increases at the same time as menopause when estrogen level decreases. Estrogen treatment is known to reduce the IgG pathogenicity by increasing the sialylation grade on the terminal glycan chain of the Fc domain, inhibiting the binding ability to the Fc gamma receptor. Therefore, treatment with estrogen may be beneficial in pre-RA patients who have autoantibodies and are prone to get an autoimmune disease. However, estrogen treatment is associated with negative side effects, therefore selective estrogen receptor modulators (SERMs) have been developed that have estrogenic protective effects with minimal side effects. In the present study, we investigated the impact of the SERM bazedoxifene on IgG sialylation as well as on total serum protein sialylation. C57BL6 mice were ovariectomized to simulate postmenopausal status, followed by ovalbumin immunization, and then treated with estrogen (estradiol), bazedoxifene, or vehicle. We found that estrogen treatment enhanced IgG levels and had a limited effect on IgG sialylation. Treatment with bazedoxifene increased the sialic acids in plasma cells in a similar manner to E2 but did not reach statistical significance. However, we did not detect any alteration in IgG-sialylation with bazedoxifene treatment. Neither estrogen nor bazedoxifene showed any significant alteration in serum protein sialylation but had a minor effect on mRNA expression of glycosyltransferase in the bone marrow, gonadal fat, and liver.

Design, synthesis and biological evaluation of fluorinated selective estrogen receptor degraders (FSERDs) --- A promising strategy for advanced ER positive breast cancer.

Although endocrine therapies involving pharmaceuticals, such as tamoxifen and aromatase inhibitors, had initially demonstrated good responses in patients with estrogen receptor-positive (ER+) breast cancer, they often led to drug resistance. ER plays a vital role in the progression of metastatic diseases. Fulvestrant, a first generation selective estrogen receptor degrader (SERD), can effectively downregulate the ER protein and inhibit its downstream signaling pathways. However, as the drug needs to be intramuscularly injected, its widespread use is limited owing to poor patient compliance. Herein, we described a novel class of orally bioavailable fluorine-substituted SERDs that exhibit improved pharmacokinetic profiles. We substituted the hydroxyl group of clinical SERD candidate 6 with a fluorine atom to diminish phase II metabolism. The subsequent structure-activity relationship (SAR) investigation identified 22h and 27b, which can effectively degrade ER in a dose-dependent manner and exhibit considerable antiproliferative potency and efficacy in vitro and in vivo. The excellent pharmacokinetic profiles of 27b render it promising candidate of clinically useful oral SERD.

Statins synergize with phosphodiesterase type 5 inhibitors but not with selective estrogen receptor modulators to prevent myofibroblast transformation in an in vitro model of Peyronie's disease.

BACKGROUND: Peyronie's disease (PD) is a fibrotic disorder characterized by plaque formation in the tunica albuginea (TA) of the penis, and we have previously shown that inhibition of transformation of TA-derived fibroblasts to myofibroblasts using a combination phosphodiesterase type 5 (PDE5) inhibitors and selective estrogen receptor modulators (SERMs) is effective in slowing the progression of early PD. AIM: The study sought to investigate whether combinations of statins with PDE5 inhibitors or SERMs would affect myofibroblast transformation in vitro. METHODS: Primary fibroblasts were isolated from TA of patients with PD and stimulated with transforming growth factor ß1 in the absence and presence of a range of concentrations of statins, PDE5 inhibitors, SERMs, and their combinations for 72 hours before quantifying α-smooth muscle actin using in-cell enzyme-linked immunosorbent assay. OUTCOMES: The prevention of transforming growth factor ß1-induced transformation of TA-derived fibroblasts to myofibroblasts was measured in vitro. RESULTS: Statins (simvastatin, lovastatin) inhibited myofibroblast transformation in a concentration-dependent manner with half maximal inhibitory concentration values of 0.77 ± 0.07 µM and 0.8 ± 0.13 µM, respectively. Simvastatin inhibited myofibroblast transformation in a synergistic fashion when combined with vardenafil (a PDE5 inhibitor; log alpha >0). Combination of tamoxifen (a SERM) and simvastatin did not show synergy (log alpha <0). When 3 drugs (simvastatin, vardenafil, and tamoxifen) were combined, the effect was not synergistic, but rather was additive. CLINICAL IMPLICATIONS: A combination of a statin with a PDE5 inhibitor might be useful in the clinic to slow the progression of the disease in patients with early PD; however, caution should be taken with such a combination because of the reported myopathy as a side effect. STRENGTHS AND LIMITATIONS: The use of primary human cells from patients with PD is a strength of this study. The mechanisms by which these drug classes exert synergy when used in combination was not investigated. CONCLUSION: This is the first demonstration of an antifibrotic synergy between statins and PDE5 inhibitors.

Expert opinion on the treatment of vulvovaginal atrophy with ospemifene based on new evidence.

Vulvovaginal atrophy (VVA) is an underdiagnosed and undertreated chronic condition resulting in physiological and histological changes in the genitourinary tract of postmenopausal women. Treatment of moderate to severe VVA includes local estrogens, dehydroepiandrosterone (DHEA) and oral ospemifene, a third-generation selective estrogen receptor modulator (SERM). Due to venous thromboembolism (VTE) safety concerns classically associated with the SERM class, and as part of its original marketing authorization approval (MAA), the European Medicines Agency (EMA) requested the performance of a 5-year post-authorization safety study (PASS) to study the incidence rate of VTE among women receiving ospemifene. The results have led to important regulatory changes to ospemifene's labeling, extending its indication and eliminating concerted risk management measures. A panel of experts discussed and reached consensus on the impact of these regulatory changes on clinical practice, reflecting on the reassurance of ospemifene's benefit-risk balance and recommending its positioning as a first-line pharmacological treatment option for moderate to severe VVA together with local therapies. In a scenario where different treatments present similar efficacy and safety profiles, a shared decision between clinician and patient, according to her needs and preferences over time, is fundamental to improve adherence and persistence with sequential treatment, contributing to the achievement of health outcomes.

New developments in the management of vulvovaginal atrophy: a comprehensive overview.

INTRODUCTION: Proper recognition and individualized therapy of vulvovaginal atrophy (VVA) is paramount. AREAS COVERED: Assessment of VVA should be performed using several questionnaires in combination with wet mount microscopy to determine Vaginal Cell Maturation Index (VCMI) and infections. PubMed searches were carried out between 1 march 2022 and 15 October 2022.Low dose vaginal estriol seems safe, efficient, and could be used in patients with contraindications for steroid hormones such as women with a history of breast cancer, and should therefore be considered as first choice hormonal treatment, when non-hormonal treatments fail. New estrogens, androgens, and several Selective Estrogen Receptor Modulators (SERMs) are being developed and tested. Intravaginal Hyaluronic Acid (HA) or Vit D can help women who can't or don't want to use hormones. EXPERT OPINION: Proper treatment is not possible without a correct and full diagnosis, including microscopy of the vaginal fluid. Low dose vaginal estrogen treatment, especially with estriol, is very efficient and is preferred in most women with VVA. Oral ospemifene and vaginal dihydroepiandrosterone (DHEA) are now considered efficient and safe alternative therapies for VVA. More safety data are waited for several SERMs and for a newly introduced estrogen: estetrol (E4), although so far no major side effects were seen from these drugs. Indications for laser treatments are questionable.

Discovery of a Potent and Orally Bioavailable Zwitterionic Series of Selective Estrogen Receptor Degrader-Antagonists.

Herein, we report the optimization of a meta-substituted series of selective estrogen receptor degrader (SERD) antagonists for the treatment of ER+ breast cancer. Structure-based design together with the use of modeling and NMR to favor the bioactive conformation led to a highly potent series of basic SERDs with promising physicochemical properties. Issues with hERG activity resulted in a strategy of zwitterion formation and ultimately in the identification of 38. This compound was shown to be a highly potent SERD capable of effectively degrading ERα in both MCF-7 and CAMA-1 cell lines. The low lipophilicity and zwitterionic nature led to a SERD with a clean secondary pharmacology profile and no hERG activity. Favorable physicochemical properties resulted in good oral bioavailability in preclinical species and potent in vivo activity in a mouse xenograft model.