LGD-5552, an antiinflammatory glucocorticoid receptor ligand with reduced side effects, in vivo

Drug repositioning to propose alternative modulators for glucocorticoid receptor through structure-based virtual screening

Drug repositioning has recently become one of the widely used drug design approaches in proposing alternative compounds with potentially fewer side effects. In this study, structure-based pharmacophore modelling and docking was used to screen existing drug molecules to bring forward potential modulators for ligand-binding domain of human glucocorticoid receptor (hGR). There exist several drug molecules targeting hGR, yet their apparent side effects still persist. Our goal was to disclose new compounds via screening existing drug compounds to bring forward fast and explicit solutions. The so-called shared pharmacophore model was created using the most persistent pharmacophore features shared by several crystal structures of the receptor. The shared model was first used to screen a small database of 75 agonists and 300 antagonists/decoys, and exhibited a successful outcome in its ability to distinguish agonists from antagonists/decoys. Then, it was used to screen a database of over 5000 molecules composed of FDA-approved, worldwide used and investigational drug compounds. A total of 110 compounds satisfying the pharmacophore requirements were subjected to different docking experiments for further assessment of their binding ability. In the final hit list of 54 compounds which fulfilled all scoring criteria, 19 of them were nonsteroidal and when further investigated, each presented a unique scaffold with little structural resemblance to any known nonsteroidal GR modulators. Independent 100 ns long MD simulations conducted on three selected drug candidates in complex with hGR displayed stable conformations incorporating several hydrogen bonds common to all three compounds and the reference molecule dexamethasone.Communicated by Ramaswamy H. Sarma.

Corticosteroid resistance in asthma: Cellular and molecular mechanisms

Inhaled glucocorticoids (GCs) are drugs widely used as treatment for asthma patients. They prevent the recruitment and activation of lung immune and inflammatory cells and, moreover, have profound effects on airway structural cells to reverse the effects of disease on airway inflammation. GCs bind to a specific receptor, the glucocorticoid receptor (GR), which is a member of the nuclear receptor superfamily and modulates pro- and anti-inflammatory gene transcription through a number of distinct and complementary mechanisms. Targets genes include many pro-inflammatory mediators such as chemokines, cytokines, growth factors and their receptors. Inhaled GCs are very effective for most asthma patients with little, if any, systemic side effects depending upon the dose. However, some patients show poor asthma control even after the administration of high doses of topical or even systemic GCs. Several mechanisms relating to inflammation have been considered to be responsible for the onset of the relative GC resistance observed in these patients. In these patients, the side-effect profile of GCs prevent continued use of high doses and new drugs are needed. Targeting the defective pathways associated with GC function in these patients may also reactivate GC responsiveness.

Discovery of novel non-steroidal selective glucocorticoid receptor modulators by structure- and IGN-based virtual screening, structural optimization, and biological evaluation

Glucocorticoids (GCs) are the most commonly used anti-inflammatory drugs. However, their excellent therapeutic effects are often accompanied by undesirable side effects. To discover selective glucocorticoid receptor modulators (SGRMs) that preferentially induce transrepression with little or no transactivation activity, a structure-based virtual screening by combining molecular docking and InteractionGraphNet (IGN) rescoring was performed, and compound HP210 was identified. HP210 did not induce the transactivation functions of GR while still acted on the NF-κB mediated tethered transrepression function (IC₅₀ = 2.32 μM), and suppressed the secretion of pro-inflammation cytokines IL-1β and IL-6. Compared with dexamethasone, HP210 showed no cross activities with phylogenetically related mineralcorticoid receptor and progesterone receptor and no significant effect on osteoprotegerin, exhibiting a reduced side-effect profile. Then, guided by the molecular dynamics simulations and binding free energy calculations, compound HP210_b4 with over two-fold higher transrepression activity (IC₅₀ = 0.99 μM) was discovered. This study reported a group of non-steroidal new-scaffold SGRMs, providing valuable clues for the development of novel anti-inflammatory drugs.

JTP-117968, a novel selective glucocorticoid receptor modulator, exhibits significant anti-inflammatory effect while maintaining bone mineral density in mice

Classic glucocorticoids have been prescribed for various inflammatory diseases, such as rheumatoid arthritis, due to their outstanding anti-inflammatory effects. However, glucocorticoids cause numerous unwanted side effects, including osteoporosis and diabetes. Hence, selective glucocorticoid receptor modulators (SGRMs), which retain anti-inflammatory effects with minimized side effects, are among the most anticipated drugs in the clinical field. The assumption is that there are two major mechanisms of action via glucocorticoid receptors, transrepression (TR) and transactivation (TA). In general, anti-inflammatory effects of glucocorticoids are largely due to TR, while the side effects associated with glucocorticoids are mostly mediated through TA. We previously reported that JTP-117968, a novel SGRM, maintained partial TR activity while remarkably reducing the TA activity. In this study, we investigated the anti-inflammatory effect of JTP-117968 on a lipopolysaccharide (LPS) challenge model and collagen-induced arthritis (CIA) model in mice. Meanwhile, we tested the effect of JTP-117968 on the bone mineral density (BMD) in mouse femur to evaluate the side effect. Based on the evaluation, JTP-117968 reduced the plasma levels of tumor necrosis factor α induced by LPS challenge in mice significantly. Remarkably, CIA development was suppressed by JTP-117968 comparably with prednisolone and PF-802, an active form of fosdagrocorat that has been developed clinically as an orally available SGRM. Strikingly, the side effect of JTP-117968 on mouse femoral BMD was much lower than those of PF-802 and prednisolone. Therefore, JTP-117968 has attractive potential as a new therapeutic option against inflammatory diseases with minimized side effects compared to classic glucocorticoids.

Improved Glucocorticoid Receptor Ligands: Fantastic Beasts, but How to Find Them?

Exogenous glucocorticoids are widely used in the clinic for the treatment of inflammatory disorders and hematological cancers. Unfortunately, their use is associated with debilitating side effects, including hyperglycemia, osteoporosis, mood swings, and weight gain. Despite the continued efforts of pharma as well as academia, the search for so-called selective glucocorticoid receptor modulators (SEGRMs), compounds with strong anti-inflammatory or anti-cancer properties but a reduced number or level of side effects, has had limited success so far. Although monoclonal antibody therapies have been successfully introduced for the treatment of certain disorders (such as anti-TNF for rheumatoid arthritis), glucocorticoids remain the first-in-line option for many other chronic diseases including asthma, multiple sclerosis, and multiple myeloma. This perspective offers our opinion on why a continued search for SEGRMs remains highly relevant in an era where small molecules are sometimes unrightfully considered old-fashioned. Besides a discussion on which bottlenecks and pitfalls might have been overlooked in the past, we elaborate on potential solutions and recent developments that may push future research in the right direction.

Neurovascular glucocorticoid receptors and glucocorticoids: implications in health, neurological disorders and drug therapy

Glucocorticoid receptors (GRs) are ubiquitous transcription factors widely studied for their role in controlling events related to inflammation, stress and homeostasis. Recently, GRs have reemerged as crucial targets of investigation in neurological disorders, with a focus on pharmacological strategies to direct complex mechanistic GR regulation and improve therapy. In the brain, GRs control functions necessary for neurovascular integrity, including responses to stress, neurological changes mediated by the hypothalamic-pituitary-adrenal axis and brain-specific responses to corticosteroids. Therefore, this review will examine GR regulation at the neurovascular interface in normal and pathological conditions, pharmacological GR modulation and glucocorticoid insensitivity in neurological disorders.

A General Introduction to Glucocorticoid Biology

Glucocorticoids (GCs) are steroid hormones widely used for the treatment of inflammation, autoimmune diseases, and cancer. To exert their broad physiological and therapeutic effects, GCs bind to the GC receptor (GR) which belongs to the nuclear receptor superfamily of transcription factors. Despite their success, GCs are hindered by the occurrence of side effects and glucocorticoid resistance (GCR). Increased knowledge on GC and GR biology together with a better understanding of the molecular mechanisms underlying the GC side effects and GCR are necessary for improved GC therapy development. We here provide a general overview on the current insights in GC biology with a focus on GC synthesis, regulation and physiology, role in inflammation inhibition, and on GR function and plasticity. Furthermore, novel and selective therapeutic strategies are proposed based on recently recognized distinct molecular mechanisms of the GR. We will explain the SEDIGRAM concept, which was launched based on our research results.

A screening assay for Selective Dimerizing Glucocorticoid Receptor Agonists and Modulators (SEDIGRAM) that are effective against acute inflammation

It has been suggested that glucocorticoid receptor (GR) agonists that promote GR homodimerization more than standard glucocorticoids such as Dexamethasone could be more effective anti-inflammatory molecules against acute and life-threatening inflammatory conditions. To test this hypothesis, we set up a screening pipeline aimed at discovering such Selective Dimerizing GR Agonists and Modulators (SEDIGRAM). The pipeline consists of a reporter gene assay based on a palindromic glucocorticoid responsive element (GRE). This assay represents GR dimerization in human A549 lung epithelial cells. In the pipeline, this is followed by analysis of endogenous GRE-driven gene expression, a FRET assay confirming dimerization, and monitoring of in vitro and in vivo anti-inflammatory activity. In a proof of principle experiment, starting from seven candidate compounds, we identified two potentially interesting compounds (Cortivazol and AZD2906) that confer strong protection in a mouse model of aggressive TNF-induced lethal inflammation. A screening pipeline for SEDIGRAM may assist the search for compounds that promote GR dimerization and limit overwhelming acute inflammatory responses.

An Approach to Greater Specificity for Glucocorticoids

Glucocorticoid steroids are among the most prescribed drugs each year. Nonetheless, the many undesirable side effects, and lack of selectivity, restrict their greater usage. Research to increase glucocorticoid specificity has spanned many years. These efforts have been hampered by the ability of glucocorticoids to both induce and repress gene transcription and also by the lack of success in defining any predictable properties that control glucocorticoid specificity. Correlations of transcriptional specificity have been observed with changes in steroid structure, receptor and chromatin conformation, DNA sequence for receptor binding, and associated cofactors. However, none of these studies have progressed to the point of being able to offer guidance for increased specificity. We summarize here a mathematical theory that allows a novel and quantifiable approach to increase selectivity. The theory applies to all three major actions of glucocorticoid receptors: induction by agonists, induction by antagonists, and repression by agonists. Simple graphical analysis of competition assays involving any two factors (steroid, chemical, peptide, protein, DNA, etc.) yields information (1) about the kinetically described mechanism of action for each factor at that step where the factor acts in the overall reaction sequence and (2) about the relative position of that step where each factor acts. These two pieces of information uniquely provide direction for increasing the specificity of glucocorticoid action. Consideration of all three modes of action indicate that the most promising approach for increased specificity is to vary the concentrations of those cofactors/pharmaceuticals that act closest to the observed end point. The potential for selectivity is even greater when varying cofactors/pharmaceuticals in conjunction with a select class of antagonists.

Efficacy and safety of selective glucocorticoid receptor modulators in comparison to glucocorticoids in arthritis, a systematic review

Background

Long-term treatment with glucocorticoids (GCs) plays an important role in the management of arthritis patients, although the efficacy/safety balance is unfavorable. Alternatives with less (severe) adverse effects but with good efficacy are needed. Selective GC receptor modulators (SGRMs) are designed to engage the GC receptor with dissociative characteristics: transactivation of genes, which is mainly responsible for unwanted effects, is less strong while trans-repression of genes, reducing inflammation, is maintained. It is expected that SGRMs thus have a better efficacy/safety balance than GCs. A systematic review providing an overview of the evidence in arthritis is lacking.

Objective

To systematically review the current literature on efficacy and safety of oral SGRMs in comparison to GCs in arthritis.

Methods

A search was performed in Medline, Embase and the Cochrane Library, from inception dates of databases until May 2017. Experimental studies involving animal arthritis models or human material of arthritis patients, as well as clinical studies in arthritis patients were included, provided they reported original data. All types of arthritis were included. Data was extracted on the SGRM studied and on the GC used as reference standard; the design or setting of the study was extracted as well as the efficacy and safety results.

Results

A total of 207 articles was retrieved of which 17 articles were eligible for our analysis. Two studies concerned randomized controlled trials (RCT), five studies were pre-clinical studies using human material, and 10 studies involved pre-clinical animal models (acute and/or chronic arthritis induced in mice or rats). PF-04171327, the only compound investigated in a clinical trial setting, had a better efficacy/safety balance compared to GCs: better clinical anti-inflammatory efficacy and similar safety.

Conclusion

Studies assessing both efficacy and safety of SGRMs are scarce. There is limited evidence for dissociation of anti-inflammatory and metabolic effects of the SGRMs studied. Development of many SGRMs is haltered in a preclinical phase. One SGRM showed a better clinical efficacy/safety balance.

Selective glucocorticoid receptor modulation inhibits cytokine responses in a canine model of mild endotoxemia

Selective glucocorticoid receptor modulators (GRMs) promise to reduce adverse events of glucocorticoids while maintaining anti-inflammatory potency. The present study tested the anti-inflammatory activity of two novel non-steroidal GRMs (GRM1: BI 607812 BS, GRM2: BI 653048 BS*H3PO4) in comparison to prednisolone in a canine model of low dose endotoxemia. This study compared the anti-inflammatory and pharmacokinetic profile of escalating daily oral doses of GRM1 (1, 2.5, 5 and 10mg/kg) and GRM2 (0.1, 0.25 and 1mg/kg) with prednisolone (0.25 and 0.5mg/kg) and placebo after intravenous infusion of endotoxin (0.1μg/kg) to Beagle dogs. This was followed by a 14-day evaluation study of safety and pharmacokinetics. Endotoxin challenge increased TNF-α ∼2000-fold and interleukin-6 (IL-6) 100-fold. Prednisolone and both GRMs suppressed peak TNF-α and IL-6 by 71-82% as compared with placebo. The highest doses of GRM1 and GRM2 reduced the mean body temperature increase by ∼30%. The endotoxin-induced rise in plasma cortisol was strongly suppressed in all treatment groups. Pharmacokinetics of both GRMs were non-linear. Adverse effects of endotoxemia such as vomiting were mitigated by GRM2 and prednisolone, indicating an antiemetic effect. During the 14-day treatment period, the adverse event profile of both GRMs appeared to be similar to prednisolone. Both GRMs had anti-inflammatory effects comparable to prednisolone and showed good safety profiles. Compounds targeting the glucocorticoid receptor selectively may provide an alternative to traditional glucocorticoids in the treatment of inflammatory disease.

JTP-117968, a novel selective glucocorticoid receptor modulator, exhibits improved transrepression/transactivation dissociation

Classic glucocorticoids that have outstanding anti-inflammatory effects are still widely prescribed for the treatment of various inflammatory and autoimmune diseases. Conversely, glucocorticoids cause numerous unwanted side effects, particularly systemically dosed glucocorticoids. Therefore, selective glucocorticoid receptor modulator (SGRM), which maintains beneficial anti-inflammatory effects while reducing the occurrence of side effects, is one of the most anticipated drugs. However, there have been no SGRMs marketed to date. The assumption is that there are two major mechanisms of action of glucocorticoids via glucocorticoid receptors, transrepression (TR) and transactivation (TA). In general, the anti-inflammatory effects of glucocorticoids are mostly mediated through TR, while the side effects associated with glucocorticoids are largely caused by TA. We started to evaluate novel orally available SGRMs that maintain anti-inflammatory effects while minimizing adverse effects by favoring TR over TA. Based on this evaluation, we discovered JTP-117968, (4b'S,7'R,8a'S)-4b'-benzyl-7'-hydroxy-N-(2-methylpyridin-3-yl)-7'-(trifluoromethyl)-4b',6',7',8',8a',10'-hexahydro-5'H-spiro[cyclopropane-1,9'-phenanthrene]-2'-carboxamide, a non-steroidal SGRM. JTP-117968 has partial TR activity, but exhibits extremely low TA activity. The maximum TR efficacy of JTP-117968 was comparable to its structural analogue, PF-802, (4bS,7R,8aR)-4b-Benzyl-7-hydroxy-N-(2-methylpyridin-3-yl)-7-(trifluoromethyl)-4b,5,6,7,8,8a,9,10-octahydrophenanthrene-2-carboxamide, which is the active form of Fosdagrocorat that has been developed clinically as a first-in-class orally available SGRM. Remarkably, the TA activity of JTP-117968 was much weaker than PF-802 not only in in vitro assays, but also in in vivo mice experiments. These findings indicate that JTP-117968 exhibits improved TR/TA dissociation because the compound has significantly lower TA activity compared with an already reported SGRM. Therefore, JTP-117968 is expected to be a useful compound for evaluating ideal SGRMs in the future.

Selective Activator of the Glucocorticoid Receptor Compound A Dissociates Therapeutic and Atrophogenic Effects of Glucocorticoid Receptor Signaling in Skin

Background:

Glucocorticoids are effective anti-inflammatory drugs widely used in dermatology and for the treatment of blood cancer patients. Unfortunately, chronic treatment with glucocorticoids results in serious metabolic and atrophogenic adverse effects including skin atrophy. Glucocorticoids act via the glucocorticoid receptor (GR), a transcription factor that causes either gene transactivation (TA) or transrepression (TR). Compound A (CpdA), a novel non-steroidal GR ligand, does not promote GR dimerization and TA, retains anti-inflammatory potential but induces fewer metabolic side effects compared to classical glucocorticoids when used systemically. As topical effects of CpdA have not been well studied, this work goal was to compare the anti-inflammatory and side effects of topical CpdA and glucocorticoids and to assess their effect on GR TA and TR in keratinocytes.

Methods:

We used murine immortalized keratinocytes and F1 C57BlxDBA mice. Effect of glucocorticoid fluocinolone acetonide (FA) and CpdA on gene expression in keratinocytes in vitro and in vivo was evaluated by reverse transcription-PCR. The anti-inflammatory effects were assessed in the model of tumor promoter 12-O-tertradecanoyl-acetate (TPA)-induced dermatitis and in croton oil-induced ear edema test. Skin atrophy was assessed by analysis of epidermal thickness, keratinocyte proliferation, subcutaneous adipose hypoplasia, and dermal changes after chronic treatment with FA and CpdA.

Results:

In mouse keratinocytes in vitro and in vivo, CpdA did not activate GR-dependent genes but mimicked closely the inhibitory effect of glucocorticoid FA on the expression of inflammatory cytokines and matrix metalloproteinases. When applied topically, CpdA inhibited TPA-induced skin inflammation and hyperplasia. Unlike glucocorticoids, CpdA itself did not induce skin atrophy which correlated with lack of induction of atrophogene regulated in development and DNA damage response 1 (REDD1) causatively involved in skin and muscle steroid-induced atrophy.

Conclusions:

Overall, our results suggest that CpdA and its derivatives represent novel promising class of anti-inflammatory compounds with reduced topical side effects.

Novel glucocorticoid receptor agonists in the treatment of asthma

INTRODUCTION

Inhaled corticosteroids are the only drugs that effectively suppress the airway inflammation, but they can induce considerable systemic and adverse effects when they are administered chronically at high doses. Consequently, the pharmaceutical industry is still searching for newer entities with an improved therapeutic index.

AREAS COVERED

Herein, the authors review the research in the glucocorticoid field to identify ligands of the glucocorticoid receptor (GR). These ligands preferentially induce transrepression with little or no transactivating activity, in order to have a potent anti-inflammatory action and a low side-effects profile.

EXPERT OPINION

Several agents have been synthesized, but few have been tested in experimental models of asthma. Furthermore, only three (BI-54903, GW870086X and AZD5423) have entered clinical development, although the development of at least one of them (BI-54903) was discontinued. The reason for the limited success so far obtained is that the model of transactivation versus transrepression is a too simplistic representation of GR activity. It is difficult to uncouple the therapeutic and harmful effects mediated by GR, but some useful information that might change the current perspective is appearing in the literature. The generation of gene expression 'fingerprints' produced by different GR agonists in target and off-target human tissues could be useful in identifying drug candidates with an improved therapeutic ratio.

Emerging corticosteroid agonists for the treatment of asthma

INTRODUCTION

Asthma is one of the most frequent chronic diseases worldwide. For decades, asthma has been treated with bronchodilators and inhaled corticosteroids (ICS). However, adverse effects of ICS and disease heterogeneity necessitate improvements in the existing treatment regimes. Recently approved ICS show improved pharmocodynamic properties. Nevertheless, emerging drugs acting on the same receptor as the ICS, glucocorticoid receptor agonists (GRAs), are under current research. These drugs exhibit selective action on the glucocorticoid receptor (GR), which may improve their adverse effect profile, compared to the currently approved ICS that act unselectively on the GR.

AREAS COVERED

The present article reviews emerging GRAs for the treatment of asthma. Furthermore, the more recently approved ICS with improved safety profiles are reviewed.

EXPERT OPINION

Compared with drugs acting on other pathological pathways, research in GRAs for asthma is sparse. However, a few promising agents acting selectively on the GR are currently under investigation and may reach approval for asthma treatment. These drugs exhibit improved pharmacodynamic properties due to selectivity in the mechanism of action, including promotion of transrepression and reduction of transactivation. However, competition from already approved ICS and other emerging treatment options may lead to cessation of development of the new GRAs.

Selective glucocorticoid receptor modulation: New directions with non-steroidal scaffolds

Glucocorticoids remain the frontline treatment for inflammatory disorders, yet represent a double-edged sword with beneficial therapeutic actions alongside adverse effects, mainly in metabolic regulation. Considerable efforts were made to improve this balance by attempting to amplify therapeutic beneficial anti-inflammatory actions and to minimize adverse metabolic actions. Most attention has focused on the development of novel compounds favoring the transrepressing actions of the glucocorticoid receptor, assumed to be important for anti-inflammatory actions, over the transactivating actions, assumed to underpin the undesirable actions. These compounds are classified as selective glucocorticoid receptor agonists (SEGRAs) or selective glucocorticoid receptor modulators (SEGRMs). The latter class is able to modulate the activity of a GR agonist and/or may not classically bind the glucocorticoid receptor ligand-binding pocket. SEGRAs and SEGRMs are collectively denominated SEGRAMs (selective glucocorticoid receptor agonists and modulators). Although this transrepression vs transactivation concept proved to be too simplistic, the developed SEGRAMs were helpful in elucidating various molecular actions of the glucocorticoid receptor, but have also raised many novel questions. We discuss lessons learned from recent mechanistic studies of selective glucocorticoid receptor modulators. This is approached by analyzing recent experimental insights in comparison with knowledge obtained using mutant GR research, thus clarifying the current view on the SEGRAM field. These insights also contribute to our understanding of the processes controlling glucocorticoid-mediated side effects as well as glucocorticoid resistance. Our perspective on non-steroidal SEGRAs and SEGRMs considers remaining opportunities to address research gaps in order to harness the potential for more safe and effective glucocorticoid receptor therapies.

Evaluation of the selective glucocorticoid receptor agonist compound A for ototoxic effects

OBJECTIVES/HYPOTHESIS

To evaluate the selective glucocorticoid receptor agonist (SEGRA) compound A, a potential novel therapeutic for inner ear disorders, for ototoxic effects.

STUDY DESIGN

Laboratory animal study.

METHODS

Experimental guinea pigs were grouped as follows: Systemic application of compound A (1.5 mg/kg and 4.5 mg/kg; n = 6/group) and intratympanic application of compound A (1 mM and 10 mM; n = 6/group). Contralateral ears in topically treated animals served as controls. Hearing thresholds were determined by auditory brainstem response before and directly after the application of compound A, as well as on days 3, 7, 14, 21, and 28. At the end of the experiments, temporal bones were harvested for histological evaluation.

RESULTS

Systemic administration of compound A (1.5 mg/kg and 4.5 mg/kg) did not cause hearing threshold shifts, whereas the intratympanic injection (1 mM and 10 mM) resulted in a hearing loss. Histological analysis of the middle and inner ears after topical compound A application showed alterations in the tympanic membranes, the auditory ossicles, and the round window membranes, whereas spiral ganglion cells and hair cells were not affected.

CONCLUSION

SEGRAs such as compound A could provide novel therapeutic options for the treatment of inner ear disorders and reduce metabolic side effects. Whereas the intratympanic application of compound A resulted in a hearing loss, the systemic application of compound A merits evaluation for otoprotective effects in trauma models.

Nuclear receptors and their selective pharmacologic modulators

Nuclear receptors are ligand-activated transcription factors and include the receptors for steroid hormones, lipophilic vitamins, sterols, and bile acids. These receptors serve as targets for development of myriad drugs that target a range of disorders. Classically defined ligands that bind to the ligand-binding domain of nuclear receptors, whether they are endogenous or synthetic, either activate receptor activity (agonists) or block activation (antagonists) and due to the ability to alter activity of the receptors are often termed receptor "modulators." The complex pharmacology of nuclear receptors has provided a class of ligands distinct from these simple modulators where ligands display agonist/partial agonist/antagonist function in a tissue or gene selective manner. This class of ligands is defined as selective modulators. Here, we review the development and pharmacology of a range of selective nuclear receptor modulators.

Design of small molecules targeting transcriptional activation by NF-κB: overview of recent advances

BACKGROUND

The transcription factor NF-κB plays a central role in immune signaling and the inflammatory response. It also activates transcription of antiapoptotic factors in tumor cells, leading to enhanced cell survival. Because of the importance of NF-κB in inflammation and cancer, there is considerable interest in development of drugs that inhibit NF-κB activation or NF-κB-directed transcription. Recent elucidation of the intracellular pathways that activate NF-κB and mechanisms for transcriptional regulation by NF-κB has identified molecular targets for rational design of such drugs.

OBJECTIVE

This review provides an update on NF-κB signaling and an overview of three classes of NF-κB inhibitors: i) inhibitors of IκB kinase-β (also called IKK2), an essential link in the inflammatory response; ii) agents that react with NF-κB and prevent its binding to DNA; and iii) ligands for nuclear receptors such as the glucocorticoid receptor, PPARs and liver X receptor, which interfere with NF-κB-mediated transcription through a mechanism termed ligand-dependent transrepression. Recent progress in development of glucocorticoid receptor, PPAR and liver X receptor ligands with dissociated activity, which retain transrepression but have reduced transactivation potency, is also described.

CONCLUSIONS

NF-κB inhibitors have yielded promising results in rodent models of inflammatory disease and cancer. Some of these are currently advancing into clinical trials.

Combination of a selective activator of the glucocorticoid receptor Compound A with a proteasome inhibitor as a novel strategy for chemotherapy of hematologic malignancies

Glucocorticoids are widely used for the treatment of hematological malignancies; however, their chronic use results in numerous metabolic side effects. Thus, the development of selective glucocorticoid receptor (GR) activators (SEGRA) with improved therapeutic index is important. GR regulates gene expression via (1) transactivation that requires GR homodimer binding to gene promoters and is linked to side effects and (2) transrepression-mediated via negative GR interaction with other transcription factors. Novel GR modulator Compound A (CpdA) prevents GR dimerization, retains glucocorticoid anti-inflammatory activity and has fewer side effects compared with glucocorticoids in vivo. Here we tested CpdA anticancer activity in human T- and B-lymphoma and multiple myeloma cells expressing GR and their counterparts with silenced GR. We found that CpdA in GR-dependent manner strongly inhibited growth and viability of human T-, B-lymphoma and multiple myeloma cells. Furthermore, primary leukemia cell cultures from T-ALL patients appeared to be equally sensitive to glucocorticoid dexamethasone and CpdA. It is known that GR expression is controlled by proteasome. We showed that pretreatment of lymphoma CEM and NCEB cells with proteasome-inhibitor Bortezomib resulted in GR accumulation and enhanced ligand properties of CpdA, shifting GR activity toward transrepression evaluated by inhibition of NFкB and AP-1 transcription factors. We also revealed remarkable GR-dependent cooperation between CpdA and Bortezomib in suppressing growth and survival of T- and B-lymphoma and multiple myeloma MM.1S cells. Overall, our data provide the rationale for novel GR-based therapy for hematological malignancies based on combination of SEGRA with proteasome inhibitors.

Anti-inflammatory effects of selective glucocorticoid receptor modulators are partially dependent on up-regulation of dual specificity phosphatase 1

BACKGROUND AND PURPOSE

It is thought that the anti-inflammatory effects of glucocorticoids (GCs) are largely due to GC receptor (GR)-mediated transrepression of NF-κB and other transcription factors, whereas side effects are caused by activation of gene expression (transactivation). Selective GR modulators (SGRMs) that preferentially promote transrepression should retain anti-inflammatory properties whilst causing fewer side effects. Contradicting this model, we found that anti-inflammatory effects of the classical GC dexamethasone were partly dependent on transactivation of the dual specificity phosphatase 1 (DUSP1) gene. We wished to determine whether anti-inflammatory effects of SGRMs are also mediated by DUSP1.

EXPERIMENTAL APPROACH

Dissociated properties of two SGRMs were confirmed using GR- and NF-κB-dependent reporters, and capacity to activate GC-responsive elements of the DUSP1 gene was tested. Effects of SGRMs on the expression of DUSP1 and pro-inflammatory gene products were assessed in various cell lines and in primary murine Dusp1(+/+) and Dusp1(-/-) macrophages.

KEY RESULTS

The SGRMs were able to up-regulate DUSP1 in several cell types, and this response correlated with the ability of the compounds to suppress COX-2 expression. Several anti-inflammatory effects of SGRMs were ablated or significantly impaired in Dusp1(-/-) macrophages.

CONCLUSIONS AND IMPLICATIONS

Like dexamethasone, SGRMs appear to exert anti-inflammatory effects partly via the up-regulation of DUSP1. This finding has implications for how potentially therapeutic novel GR ligands are identified and assessed.

Selective glucocorticoid receptor agonists for the treatment of inflammatory bowel disease: studies in mice with acute trinitrobenzene sulfonic acid colitis

Despite being a mainstay of inflammatory bowel disease (IBD) therapy, glucocorticoids (GCs) still carry significant risks with respect to unwanted side effects. Alternative drugs with a more favorable risk/benefit ratio than common GCs are thus highly desirable for the management of IBD. New and supposedly selective glucocorticoid receptor (GR) agonists (SEGRAs), with dissociated properties, have been described as promising candidates for circumventing therapeutic problems while still displaying full beneficial anti-inflammatory potency. Here, we report on compound A [CpdA; (2-((4-acetophenyl)-2-chloro-N-methyl)ethylammonium-chloride)] and N-(4-methyl-1-oxo-1H-2,3-benzoxazine-6-yl)-4-(2,3-dihydrobenzofuran-7-yl)-2-hydroxy-2-(trifluoromethyl)-4-methylpentanamide (ZK216348), two GR agonists for the treatment of experimental colitis. Their therapeutic and anti-inflammatory effects were tested in the acute trinitrobenzene sulfonic acid-mediated colitis model in mice against dexamethasone (Dex). In addition to their influence on immunological pathways, a set of possible side effects, including impact on glucose homeostasis, steroid resistance, and induction of apoptosis, was surveyed. Our results showed that, comparable with Dex, treatment with CpdA and ZK216348 reduced the severity of wasting disease, macroscopic and microscopic damage, and colonic inflammation. However, both SEGRAs exhibited no GC-associated diabetogenic effects, hypothalamic pituitary adrenal axis suppression, or development of glucocorticoid resistance. In addition, CpdA and ZK216348 showed fewer transactivating properties and successfully dampened T helper 1 immune response. Unlike ZK216348, the therapeutic benefit of CpdA was lost at higher doses because of toxic apoptotic effects. In conclusion, both SEGRAs acted as potent anti-inflammatory agents with a significantly improved profile compared with classic GCs. Although CpdA revealed a narrow therapeutic window, both GR agonists might be seen as a starting point for a future IBD treatment option.

Maps and legends: the quest for dissociated ligands of the glucocorticoid receptor

Glucocorticoids are steroid hormones that have pleiotropic effects on development, metabolism, cognitive function and other aspects of physiology. Since the demonstration more than sixty years ago of their capacity to suppress inflammation, synthetic glucocorticoids have been extremely widely used in the treatment of inflammatory diseases. However, their clinical use is limited by numerous, unpredictable and potentially serious side effects. Glucocorticoids regulate gene expression both positively and negatively. Both of these effects are mediated by the glucocorticoid receptor, a ligand-dependent transcription factor. It has become widely accepted that anti-inflammatory effects of glucocorticoids are mostly due to inhibition of transcription, whereas the activation of transcription by the glucocorticoid receptor accounts for the majority of side effects. This dogma (which we refer to as the "transrepression hypothesis") predicts the possibility of uncoupling therapeutic, anti-inflammatory effects from side effects by identifying novel, selective ligands of the glucocorticoid receptor, which preferentially mediate inhibition rather than activation of transcription. It is argued that such "dissociated" glucocorticoid receptor ligands should retain anti-inflammatory potency but cause fewer side effects. Here we critically re-examine the history and foundations of the transrepression hypothesis. We argue that it is incompatible with the complexity of gene regulation by glucocorticoids and poorly supported by experimental evidence; that it no longer aids clear thinking about the actions of the glucocorticoid receptor; and that it will not prove a fruitful basis for continued refinement and improvement of anti-inflammatory drugs that target the glucocorticoid receptor.

Beneficial pharmacological effects of selective glucocorticoid receptor agonist in external eye diseases

PURPOSE

Glucocorticoids exert their actions via the glucocorticoid receptor through at least 2 intracellular mechanisms, known as transrepression and transactivation. It has been hypothesized that transrepression is the basis of their anti-inflammatory effects, whereas transactivation has been assumed to cause their side effects. ZK209614, a recently identified, novel selective glucocorticoid receptor agonist, exerts strong transrepression and weak transactivation. The objective of this study was to determine whether its pharmacological effects can be dissociated from its side effects. For this, we employed in vitro assays and topical in vivo models.

METHODS

ZK209614 and dexamethasone were used in in vitro transrepression and transactivation assays. To evaluate anti-inflammatory and antiallergic activities in vivo, ZK209614 and betamethasone phosphate were tested in the carrageenan-induced conjunctivitis model and allergic conjunctivitis model in rats. To evaluate side effects in vivo, treatments with ZK209614 and betamethasone phosphate were tested for the ocular hypertensive effects in a feline model, each drug being administered topically.

RESULTS

ZK209614 showed strong transrepression and weak transactivation in the in vitro assays. When given as eyedrops, ZK209614 and betamethasone phosphate each had an inhibitory effect on edema weight in the rat carrageenan-induced conjunctivitis model. In the rat allergic conjunctivitis model, ZK209614 reduced the elevated vascular permeability at a concentration of 0.1%. In the feline intraocular pressure (IOP)-elevation experiment, topically administered betamethasone phosphate elevated IOP, but ZK209614 had no effect on IOP.

CONCLUSION

The present investigations suggest that ZK209614 eyedrops have both anti-inflammatory and antiallergic effects, but no unwanted IOP-elevating effect. On that basis, ZK209614 might be a promising candidate as an ophthalmic drug with a better therapeutic index than classic glucocorticoids.

Classic glucocorticoids versus non-steroidal glucocorticoid receptor modulators: survival of the fittest regulator of the immune system?

The search for novel glucocorticoid receptor (GR) modulators with similar anti-inflammatory properties as conventional steroids, but with a reduction in the number or severity of the side effects has been a long-standing goal, and still remains a challenge today. The quest for these so-called 'dissociated GR ligands' is mainly based on the hypothesis that the occurrence of undesirable side effects is mostly associated with GR-mediated transactivation, whereas transrepression of many pro-inflammatory genes (e.g. cytokines and enzymes involved in inflammatory processes) is more involved in GR-mediated anti-inflammatory effects. As glucocorticoids (GCs) can also enhance the transcription of anti-inflammatory genes, the GR-mediated activation-repression dissociation hypothesis has to be nuanced. However, an enhanced selectivity of GR-affected genes, while upholding the desired anti-inflammatory potential, is still believed to contribute to a more beneficial therapeutic profile with fewer side effects. The initial pharmacological focus on steroidal scaffolds as a basis to dissociate the functionalities of GR has, due to a lack of success, recently been shifted to a focus on non-steroidal ligands. The current work reviews recent advances on the characterization of a generation of novel non-steroidal GR ligands.

NF-kappaB signaling: multiple angles to target OA

In the context of OA disease, NF-kappaB transcription factors can be triggered by a host of stress-related stimuli including pro-inflammatory cytokines, excessive mechanical stress and ECM degradation products. Activated NF-kappaB regulates the expression of many cytokines and chemokines, adhesion molecules, inflammatory mediators, and several matrix degrading enzymes. NF-kappaB also influences the regulated accumulation and remodeling of ECM proteins and has indirect positive effects on downstream regulators of terminal chondrocyte differentiation (including beta-catenin and Runx2). Although driven partly by pro-inflammatory and stress-related factors, OA pathogenesis also involves a "loss of maturational arrest" that inappropriately pushes chondrocytes towards a more differentiated, hypertrophic-like state. Growing evidence points to NF-kappaB signaling as not only playing a central role in the pro-inflammatory stress-related responses of chondrocytes to extra- and intra-cellular insults, but also in the control of their differentiation program. Thus unlike other signaling pathways the NF-kappaB activating kinases are potential therapeutic OA targets for multiple reasons. Targeted strategies to prevent unwanted NF-kappaB activation in this context, which do not cause side effects on other proteins or signaling pathways, need to be focused on the use of highly specific drug modalities, siRNAs or other biological inhibitors that are targeted to the activating NF-kappaB kinases IKKalpha or IKKbeta or specific activating canonical NF-kappaB subunits. However, work remains in its infancy to evaluate the effects of efficacious, targeted NF-kappaB inhibitors in animal models of OA disease in vivo and to also target these strategies only to affected cartilage and joints to avoid other undesirable systemic effects.

Selective Glucocorticoid Receptor modulators

The ancient two-faced Roman god Janus is often used as a metaphor to describe the characteristics of the Glucocorticoid Receptor (NR3C1), which exhibits both a beneficial side, that serves to halt inflammation, and a detrimental side responsible for undesirable effects. However, recent developments suggest that the Glucocorticoid Receptor has many more faces with the potential to express a range of different functionalities, depending on factors that include the tissue type, ligand type, receptor variants, cofactor surroundings and target gene promoters. This behavior of the receptor has made the development of safer ligands, that trigger the expression program of only a desirable subset of genes, a real challenge. Thus more knowledge-based fundamental research is needed to ensure the design and development of selective Glucocorticoid Receptor modulators capable of reaching the clinic. Recent advances in the characterization of novel selective Glucocorticoid Receptor modulators, specifically in the context of anti-inflammatory strategies, will be described in this review.

Antiinflammatory properties of a plant-derived nonsteroidal, dissociated glucocorticoid receptor modulator in experimental autoimmune encephalomyelitis

Compound A (CpdA), a plant-derived phenyl aziridine precursor, was recently characterized as a fully dissociated nonsteroidal antiinflammatory agent, acting via activation of the glucocorticoid receptor, thereby down-modulating nuclear factor-kappaB-mediated transactivation, but not supporting glucocorticoid response element-driven gene expression. The present study demonstrates the effectiveness of CpdA in inhibiting the disease progress in experimental autoimmune encephalomyelitis (EAE), a well-characterized animal model of multiple sclerosis. CpdA treatment of mice, both early and at the peak of the disease, markedly suppressed the clinical symptoms of EAE induced by myelin oligodendrocyte glycoprotein peptide immunization. Attenuation of the clinical symptoms of EAE by CpdA was accompanied by reduced leukocyte infiltration in the spinal cord, reduced expression of inflammatory cytokines and chemokines, and reduced neuronal damage and demyelination. In vivo CpdA therapy suppressed the encephalogenicity of myelin oligodendrocyte glycoprotein peptide-specific T cells. Moreover, CpdA was able to inhibit TNF- and lipopolysaccharide-induced nuclear factor-kappaB activation in primary microglial cells in vitro, in a differential mechanistic manner as compared with dexamethasone. Finally, in EAE mice the therapeutic effect of CpdA, in contrast to that of dexamethasone, occurred in the absence of hyperinsulinemia and in the absence of a suppressive effect on the hypothalamic-pituitary-adrenal axis. Based on these results, we propose CpdA as a compound with promising antiinflammatory characteristics useful for therapeutic intervention in multiple sclerosis and other neuroinflammatory diseases.

Crosstalk in inflammation: the interplay of glucocorticoid receptor-based mechanisms and kinases and phosphatases

Glucocorticoids (GCs) are steroidal ligands for the GC receptor (GR), which can function as a ligand-activated transcription factor. These steroidal ligands and derivatives thereof are the first line of treatment in a vast array of inflammatory diseases. However, due to the general surge of side effects associated with long-term use of GCs and the potential problem of GC resistance in some patients, the scientific world continues to search for a better understanding of the GC-mediated antiinflammatory mechanisms. The reversible phosphomodification of various mediators in the inflammatory process plays a key role in modulating and fine-tuning the sensitivity, longevity, and intensity of the inflammatory response. As such, the antiinflammatory GCs can modulate the activity and/or expression of various kinases and phosphatases, thus affecting the signaling efficacy toward the propagation of proinflammatory gene expression and proinflammatory gene mRNA stability. Conversely, phosphorylation of GR can affect GR ligand- and DNA-binding affinity, mobility, and cofactor recruitment, culminating in altered transactivation and transrepression capabilities of GR, and consequently leading to a modified antiinflammatory potential. Recently, new roles for kinases and phosphatases have been described in GR-based antiinflammatory mechanisms. Moreover, kinase inhibitors have become increasingly important as antiinflammatory tools, not only for research but also for therapeutic purposes. In light of these developments, we aim to illuminate the integrated interplay between GR signaling and its correlating kinases and phosphatases in the context of the clinically important combat of inflammation, giving attention to implications on GC-mediated side effects and therapy resistance.

Minireview: live and let die: molecular effects of glucocorticoids on bone cells

Glucocorticoids (GCs) are efficient drugs that are used to treat various immune-mediated diseases, but their long-term administration is associated with multiple metabolic side effects, including osteoporosis. Molecular analyses of the mechanisms exerted by the GC receptor have resulted in the development of GC receptor agonists that selectively repress or activate GC target genes. This review summarizes the cellular and molecular effects of GCs on bone cells and highlights the critical signaling pathways that may evolve into future therapeutic strategies.

Characterization of ZK 245186, a novel, selective glucocorticoid receptor agonist for the topical treatment of inflammatory skin diseases

BACKGROUND AND PURPOSE

Glucocorticoids are highly effective in the therapy of inflammatory diseases. Their value, however, is limited by side effects. The discovery of the molecular mechanisms of the glucocorticoid receptor and the recognition that activation and repression of gene expression could be addressed separately opened the possibility of achieving improved safety profiles by the identification of ligands that predominantly induce repression. Here we report on ZK 245186, a novel, non-steroidal, low-molecular-weight, glucocorticoid receptor-selective agonist for the topical treatment of inflammatory dermatoses.

EXPERIMENTAL APPROACH

Pharmacological properties of ZK 245186 and reference compounds were studied in terms of their potential anti-inflammatory and side effects in functional bioassays in vitro and in rodent models in vivo.

KEY RESULTS

Anti-inflammatory activity of ZK 245186 was demonstrated in in vitro assays for inhibition of cytokine secretion and T cell proliferation. In vivo, using irritant contact dermatitis and T cell-mediated contact allergy models in mice and rats, ZK 245186 showed anti-inflammatory efficacy after topical application similar to the classical glucocorticoids, mometasone furoate and methylprednisolone aceponate. ZK 245186, however, exhibits a better safety profile with regard to growth inhibition and induction of skin atrophy after long-term topical application, thymocyte apoptosis, hyperglycaemia and hepatic tyrosine aminotransferase activity.

CONCLUSIONS AND IMPLICATIONS

ZK 245186 is a potent anti-inflammatory compound with a lower potential for side effects, compared with classical glucocorticoids. It represents a promising drug candidate and is currently in clinical trials.

Minireview: latest perspectives on antiinflammatory actions of glucocorticoids

Taking into consideration that glucocorticoid (GC) hormones have been used clinically for over half a century and that more than 20 yr have passed since the cloning of the GC receptor (GR), it is hard to imagine that novel aspects in the molecular mechanism by which GCs mediate their antiinflammatory actions are still being unveiled today. Partly, this is because almost on a daily basis, novel insights arise from parallel fields, e.g. nuclear receptor cofactor and chromatin regulation and their concomitant impact on gene transcription events, eventually leading to a revisitation or refinement of old hypotheses. On the other hand, it does remain striking and puzzling why GCs use different mechanisms in so many different cell types and on many different target genes to elicit an antiinflammatory effect. Meanwhile, the obvious question for the clinic remains: is the separation of GR functionalities through differential ligand design the strategy of choice to avoid most GC-mediated side effects? This minireview aims to highlight some of the latest findings on aspects of the antiinflammatory working mechanisms of GCs.

Genomic and nongenomic effects of glucocorticoids

The strong anti-inflammatory and immunosuppressive effects of glucocorticoids are mediated primarily by the cytosolic glucocorticoid receptors. These receptors are members of the steroid hormone receptor family, a superfamily of ligand-inducible transcription factors, and exert genomic effects that can result in increased expression of regulatory-including anti-inflammatory-proteins (transactivation), or decreased production of proinflammatory proteins (transrepression). Transactivation is thought to be responsible for numerous adverse effects of glucocorticoids; transrepression is thought to be responsible for many of the clinically desirable anti-inflammatory and immunosuppressive effects of glucocorticoids. Optimized glucocorticoids, such as selective glucocorticoid receptor agonists, are being developed to try to minimize the adverse effects many patients experience. Glucocorticoids also exert their effects via rapid, nongenomic mechanisms that can be classified as involving nonspecific interactions of glucocorticoids with cellular membranes, nongenomic effects that are mediated by cytosolic glucocorticoid receptors, or specific interactions with membrane-bound glucocorticoid receptors. Increased understanding of these mechanisms of glucocorticoid action could enable the development of novel drugs with which to treat patients with inflammatory and autoimmune disease.