Discovery of potent, nonsteroidal, and highly selective glucocorticoid receptor antagonists

Brønsted Base-Catalyzed Enantioselective α-Functionalization of Carbonyl Compounds Involving π-Extended Enolates

Chiral Brønsted base (BB) catalyzed asymmetric transformations constitute an important tool for synthesis. A meaningful fraction of these transformations proceeds through transiently generated enolate intermediates, which display quite versatile reactivity against a variety of electrophiles. Some years ago, our group became interested in developing BB-catalyzed asymmetric reactions of enolizable carbonyl substrates that involve π-extended enolates in which, besides control of reaction diastereo and enantioselectivity, the site-selectivity control is an additional issue in most cases. In the examples covered in this account the opportunities deployed, and the challenges posed, by these methods are illustrated, with a focus on the generation of quaternary carbon stereocenters. In the way, new bifunctional BB catalysts as well as achiral templates were developed that may find further applications.

Physiological concentrations of glucocorticoids induce pathological DNA double-strand breaks

Steroid hormones induce the transcription of target genes by activating nuclear receptors. Early transcriptional response to various stimuli, including hormones, involves the active catalysis of topoisomerase II (TOP2) at transcription regulatory sequences. TOP2 untangles DNAs by transiently generating double-strand breaks (DSBs), where TOP2 covalently binds to DSB ends. When TOP2 fails to rejoin, called "abortive" catalysis, the resulting DSBs are repaired by tyrosyl-DNA phosphodiesterase 2 (TDP2) and non-homologous end-joining (NHEJ). A steroid, cortisol, is the most important glucocorticoid, and dexamethasone (Dex), a synthetic glucocorticoid, is widely used for suppressing inflammation in clinics. We here revealed that clinically relevant concentrations of Dex and physiological concentrations of cortisol efficiently induce DSBs in G1 phase cells deficient in TDP2 and NHEJ. The DSB induction depends on glucocorticoid receptor (GR) and TOP2. Considering the specific role of TDP2 in removing TOP2 adducts from DSB ends, induced DSBs most likely represent stalled TOP2-DSB complexes. Inhibition of RNA polymerase II suppressed the DSBs formation only modestly in the G1 phase. We propose that cortisol and Dex frequently generate DSBs through the abortive catalysis of TOP2 at transcriptional regulatory sequences, including promoters or enhancers, where active TOP2 catalysis occurs during early transcriptional response.

Antagonizing the Glucocorticoid Receptor Impairs Explant-Induced Reactivation in Mice Latently Infected with Herpes Simplex Virus 1

Herpes simplex virus 1 (HSV-1) establishes lifelong latent infections in neurons. Reactivation from latency can lead to serious recurrent disease, including stromal keratitis, corneal scarring, blindness, and encephalitis. Although numerous studies link stress to an increase in the incidence of reactivation from latency and recurrent disease, the mechanism of action is not well understood. We hypothesized that stress, via corticosteroid-mediated activation of the glucocorticoid receptor (GR), stimulates viral gene expression and productive infection during reactivation from latency. Consequently, we tested whether GR activation by the synthetic corticosteroid dexamethasone influenced virus shedding during reactivation from latency using trigeminal ganglion (TG) explants from Swiss Webster mice latently infected with HSV-1, strain McKrae. TG explants from the latently infected mice shed significantly higher levels of virus when treated with dexamethasone. Conversely, virus shedding from TG explants was significantly impaired when they were incubated with medium containing a GR-specific antagonist (CORT-108297) or stripped fetal bovine serum, which lacks nuclear hormones and other growth factors. TG explants from latently infected, but not uninfected, TG contained significantly more GR-positive neurons following explant when treated with dexamethasone. Strikingly, VP16 protein expression was detected in TG neurons at 8 hours after explant whereas infected-cell protein 0 (ICP0) and ICP4 protein expression was not readily detected until 16 hours after explant. Expression of all three viral regulatory proteins was stimulated by dexamethasone. These studies indicated corticosteroid-mediated GR activation increased the number of TG neurons expressing viral regulatory proteins, which enhanced virus shedding during explant-induced reactivation from latency.IMPORTANCE Herpes simplex virus 1 (HSV-1) establishes lifelong latent infections in neurons within trigeminal ganglia (TG); periodically, reactivation from latency occurs, leading to virus transmission and recurrent disease. Chronic or acute stress increases the frequency of reactivation from latency; how this occurs is not well understood. Here, we demonstrate that the synthetic corticosteroid dexamethasone stimulated explant-induced reactivation from latency. Conversely, a glucocorticoid receptor (GR) antagonist significantly impaired reactivation from latency, indicating that GR activation stimulated explant-induced reactivation. The viral regulatory protein VP16 was readily detected in TG neurons prior to infected-cell protein 0 (ICP0) and ICP4 during explant-induced reactivation. Dexamethasone induced expression of all three viral regulatory proteins following TG explant. Whereas the immunosuppressive properties of corticosteroids would facilitate viral spread during reactivation from latency, these studies indicate GR activation increases the number of TG neurons that express viral regulatory proteins during early stages of explant-induced reactivation.

The Glucocorticoid Receptor (GR) Stimulates Herpes Simplex Virus 1 Productive Infection, in Part Because the Infected Cell Protein 0 (ICP0) Promoter Is Cooperatively Transactivated by the GR and Krüppel-Like Transcription Factor 15

Following acute infection, herpes simplex virus 1 (HSV-1) establishes lifelong latency in neurons. Physical, emotional, and chemical stresses are linked to increasing the incidence of reactivation from latency, but the mechanism of action is not well understood. In general, stress increases corticosteroid levels, leading to activation of the glucocorticoid receptor (GR), a pioneer transcription factor. Consequently, we hypothesized that stress-mediated activation of the GR can stimulate productive infection and viral gene expression. New studies demonstrated that the GR-specific antagonist (CORT-108297) significantly reduced HSV-1 productive infection in mouse neuroblastoma cells (Neuro-2A). Additional studies demonstrated that the activated GR and Krüppel-like transcription factor 15 (KLF15) cooperatively transactivated the infected cell protein 0 (ICP0) promoter, a crucial viral regulatory protein. Interestingly, the synthetic corticosteroid dexamethasone and GR or KLF15 alone had little effect on ICP0 promoter activity in transfected Neuro-2A or Vero cells. Chromatin immunoprecipitation (ChIP) studies revealed that the GR and KLF15 occupied ICP0 promoter sequences important for transactivation at 2 and 4 h after infection; however, binding was not readily detected at 6 h after infection. Similar results were obtained for cells transfected with the full-length ICP0 promoter. ICP0 promoter sequences lack a consensus "whole" GR response element (GRE) but contain putative half-GREs that were important for dexamethasone induced promoter activity. The activated GR stimulates expression of, and interacts with, KLF15; consequently, these data suggest KLF15 and the GR form a feed-forward loop that activates viral gene expression and productive infection following stressful stimuli.IMPORTANCE The ability of herpes simplex virus 1 (HSV-1) to periodically reactivate from latency results in virus transmission and recurrent disease. The incidence of reactivation from latency is increased by chronic or acute stress. Stress increases the levels of corticosteroids, which bind and activate the glucocorticoid receptor (GR). Since GR activation is an immediate early response to stress, we tested whether the GR influences productive infection and the promoter that drives infected cell protein 0 (ICP0) expression. Pretreatment of cells with a GR-specific antagonist (CORT-108297) significantly reduced virus replication. Although the GR had little effect on ICP0 promoter activity alone, the Krüppel-like transcription factor 15 (KLF15) cooperated with the GR to stimulate promoter activity in transfected cells. In transfected or infected cells, the GR and KLF15 occupied ICP0 sequences important for transactivation. Collectively, these studies provide insight into how stress can directly stimulate productive infection and viral gene expression.

Drug design strategies for Cushing's syndrome

INTRODUCTION

Cushing's syndrome (CS) is a metabolic disorder caused by chronic hypercortisolism. CS is associated with cardiovascular, metabolic, skeletal and psychological dysfunctions and can be fatal if left untreated. The first-line treatment for all forms of CS is a surgery. However, medical therapy has to be chosen if surgical resection is not an option or is deemed ineffective. Currently available therapeutics are either not selective and have side effects or are only available as an injection (pasireotide). Areas covered: The authors discuss the recent drug developments for the medical treatment of CS through two validated molecular targets. Specifically, the authors look at selective inhibitors of CYP11B1 that reduce cortisol production by inhibiting steroid 11beta-hydroxylase and glucocorticoid receptor (GR) antagonists that interrupt cortisol-mediating transcriptional regulation of related genes. Expert opinion: Patients with CS have limited treatment options; indeed, there is an unmet need for new compounds that target CYP11B1 selectively versus several steroidogenic enzymes and/or GR-signaling pathways. The complexity of steroid biosynthesis and signaling requires the application of structure-based drug discovery techniques that use molecular targets and highly similar off-targets. Significant differences in steroidogenesis between humans and other species necessitates caution over the choice of in vivo model for the preclinical evaluation of future potential compounds.

Facile synthesis of fused polycyclic compounds via intramolecular oxidative cyclization/aromatization of β-tetralone or β-tetralone oximes

A mild and efficient NBS promoted intramolecular oxidative cyclization/aromatization of β-tetralone oximes has been explored. Under the optimized conditions, fused α-carbolines containing pentacyclic rings were obtained in moderate to good yields. Furthermore, various benzo[5,6]chromeno[2,3-b]indoles were successfully synthesized in moderate yields from β-tetralones using slightly modified conditions. We proposed a possible reaction pathway based on the experimental results.

Manganese-catalysed benzylic C(sp3)-H amination for late-stage functionalization

Reactions that directly install nitrogen into C-H bonds of complex molecules are significant because of their potential to change the chemical and biological properties of a given compound. Although selective intramolecular C-H amination reactions are known, achieving high levels of reactivity while maintaining excellent site selectivity and functional-group tolerance remains a challenge for intermolecular C-H amination. Here, we report a manganese perchlorophthalocyanine catalyst [MnIII(ClPc)] for intermolecular benzylic C-H amination of bioactive molecules and natural products that proceeds with unprecedented levels of reactivity and site selectivity. In the presence of a Brønsted or Lewis acid, the [MnIII(ClPc)]-catalysed C-H amination demonstrates unique tolerance for tertiary amine, pyridine and benzimidazole functionalities. Mechanistic studies suggest that C-H amination likely proceeds through an electrophilic metallonitrene intermediate via a stepwise pathway where C-H cleavage is the rate-determining step of the reaction. Collectively, these mechanistic features contrast with previous base-metal-catalysed C-H aminations and provide new opportunities for tunable selectivities.

Imidazo[2,1-b]benzothiazol Derivatives as Potential Allosteric Inhibitors of the Glucocorticoid Receptor

Glucocorticoid receptor (GCR) transactivation reporter gene assays were used as an initial high-throughput screening on a diversified library of 1200 compounds for their evaluation as GCR antagonists. A class of imidazo[2,1-b]benzothiazole and imidazo[2,1-b]benzoimidazole derivatives were identified for their ability to modulate GCR transactivation and anti-inflammatory transrepression effects utilizing GCR and NF-κB specific reporter gene assays. Modeling studies on the crystallographic structure of the GCR ligand binding domain provided three new analogues bearing the tetrahydroimidazo[2,1-b]benzothiazole scaffold able to antagonize the GCR in the presence of dexamethasone (DEX) and also defined their putative binding into the GCR structure. Both mRNA level measures of GCR itself and its target gene GILZ, on cells treated with the new analogues, showed a GCR transactivation inhibition, thus suggesting a potential allosteric inhibition of the GCR.

Fragment-based Shape Signatures: a new tool for virtual screening and drug discovery

Since its introduction in 2003, the Shape Signatures method has been successfully applied in a number of drug design projects. Because it uses a ray-tracing approach to directly measure molecular shape and properties (as opposed to relying on chemical structure), it excels at scaffold hopping, and is extraordinarily easy to use. Despite its advantages, a significant drawback of the method has hampered its application to certain classes of problems; namely, when the chemical structures considered are large and contain heterogeneous ring-systems, the method produces descriptors that tend to merely measure the overall size of the molecule, and begin to lose selective power. To remedy this, the approach has been reformulated to automatically decompose compounds into fragments using ring systems as anchors, and to likewise partition the ray-trace in accordance with the fragment assignments. Subsequently, descriptors are generated that are fragment-based, and query and target molecules are compared by mapping query fragments onto target fragments in all ways consistent with the underlying chemical connectivity. This has proven to greatly extend the selective power of the method, while maintaining the ease of use and scaffold-hopping capabilities that characterized the original implementation. In this work, we provide a full conceptual description of the next generation Shape Signatures, and we underline the advantages of the method by discussing its practical applications to ligand-based virtual screening. The new approach can also be applied in receptor-based mode, where protein-binding sites (partitioned into subsites) can be matched against the new fragment-based Shape Signatures descriptors of library compounds.

Noncanonical mechanisms to regulate nuclear receptor signaling

Nuclear receptor (NR)-targeted therapies comprise a large class of clinically employed drugs. A number of drugs currently being used against this protein class were designed as structural analogs of the endogenous ligand of these receptors. In recent years, there has been significant interest in developing newer strategies to target NRs, especially those that rely on mechanistic pathways of NR function. Prominent among these are noncanonical means of targeting NRs, which include selective NR modulation, NR coactivator interaction inhibition, inhibition of NR DNA binding, modulation of NR cellular localization, modulation of NR ligand biosynthesis and downregulation of NR levels in target tissues. This article reviews each of these promising emerging strategies for NR drug development and highlights some of most significant successes achieved in using them.

Discovery of a novel non-steroidal GR antagonist with in vivo efficacy in the olanzapine-induced weight gain model in the rat

We report the optimization of a series of non-steroidal GR antagonists that led to the identification of compound 7. This compound is efficacious when dosed orally in an olanzapine-induced weight gain model in rats.

Non-steroidal Dissociated Glucocorticoid Receptor Agonists

Synthetic glucocorticoids, such as dexamethasone and prednisolone, are amongst the most commonly used drugs due to their potent and efficacious anti-inflammatory and immunosuppressive properties. However, their long-term and/or high-dose administration is limited by a number of deleterious side-effects, including glucocorticoid-induced diabetes and osteoporosis. Glucocorticoids exert their effects through binding to the glucocorticoid receptor. Since the discovery of multiple differentiated down-stream functions of the glucocorticoid-bound receptor, such as gene transrepression and transactivation, researchers in academia and industry have been on a quest to discover novel glucocorticoids that achieve functional selectivity, hence dissociating the desired anti-inflammatory from the undesired side-effects. This review describes the current state of discovery and development of non-steroidal glucocorticoid receptor agonists. Several small-molecule drug candidates have advanced into clinical trials, and have shown promising early biomarker data, as well as beneficial effects in topical applications. However, a clinically efficacious and systemically available glucocorticoid with significantly reduced side-effects as compared to current steroidal drugs, the “Holy Grail” in immunology, is still elusive.

Administration of a selective glucocorticoid antagonist attenuates electroconvulsive shock-induced retrograde amnesia

Mifepristone, a glucocorticoid and progesterone receptor antagonist, has been shown to attenuate retrograde amnesia induced by repeated electroconvulsive shocks (ECS). We examined the efficacy of CORT 108297, a selective glucocorticoid antagonist, in this regard. Adult, male, Wistar rats (n = 69) received either vehicle or CORT 108297 (1 mg/kg) 2 h before each of 5 once-daily true or sham 30 mC ECS. Recall of previous exposure to a noxious stimulus in a passive avoidance (step-through) paradigm was tested 1 day after the 5-ECS course. Analyses were conducted using recall operationalized in different ways: using the absolute final latency scores; defining adequate recall as a final latency of 30 s or greater; defining perfect recall as a final latency of 180 s; and using visual, subjective assessments of animal behavior. ECS was associated with significant impairment of recall, and this impairment was significantly attenuated by CORT 108297 on all outcome measures (with the exception of the perfect recall analyses, where outcomes narrowly missed statistical significance). In conclusion, these findings strengthen previous data from our laboratory implicating glucocorticoid mechanisms in ECS-induced retrograde amnesia. We suggest that the administration of a selective glucocorticoid receptor antagonist shortly before electroconvulsive therapy (ECT) treatments may attenuate the deleterious effect of ECT-induced acute hypercortisolemia on neural mechanisms involved in learning and memory.

Steroidal C-21 mercapto derivatives as dissociated steroids: discovery of an inhaled dissociated steroid

A series of C-21 mercapto derivatives of hydrocortisone have been synthesized and evaluated in cell based transrepression and transactivation assays. The benzothiazole derivative, compound 6 not only showed a dissociated profile in vitro functional assays but also a pharmacological profile in a Brown-Norway rat therapeutic index model of asthma that dissociated side effects (thymolysis) while maintaining efficacy against pulmonary inflammation and lung function.

The antagonists but not partial agonists of glucocorticoid receptor ligands show substantial side effect dissociation

A synthetic glucocorticoid receptor (GR) ligand with the efficacy of a glucocorticoid, but without the accompanying side effects, would meet an unmet medical need for the treatment of inflammatory diseases. It was hypothesized that a GR ligand that shifted helix 12 in a manner distinct from an agonist and an antagonist would confer a distinct GR conformation, resulting in differential gene expression and, ultimately, dissociation of antiinflammatory activity from side effects. A structural feature expected to interfere with helix 12 was incorporated into a nonsteroidal, tricyclic scaffold to create novel, high-affinity, and selective GR ligands that manifested a dual function in cellular assays, partial but robust agonist activity for inflammatory cytokine inhibition, and full antagonist activity for reporter gene activation. In contrast, analogs not likely to hinder helix 12 exhibited partial agonist activity for reporter gene activation. The requirement of full antagonist activity for substantial side effect dissociation was demonstrated in primary human preadipocytes, hepatocytes, and osteoblasts in which effects on adipogenesis, key genes involved in gluconeogenesis, and genes important for bone formation were examined, respectively. The dissociated GR ligands, despite lacking significant reporter gene activation, weakly recruit a limited number of coactivators such as peroxisomal proliferator-activated receptor-γ coactivator 1α. Transcriptional activation was sensitive to both peroxisomal proliferator-activated receptor-γ coactivator 1α and GR levels, providing a basis for cell-selective modulation of gene expression. The antiinflammatory activity of the dissociated ligands was further demonstrated in mouse models of inflammation. Together these results suggest that these ligands are promising candidates with robust antiinflammatory activity and likely dissociation against glucocorticoid-induced side effects.

Rational ligand-based virtual screening and structure-activity relationship studies in the ligand-binding domain of the glucocorticoid receptor-α

The interest in developing synthetic glucocorticoids (GCs) arises from the utility of endogenous steroids as potent anti-inflammatory and immunosuppressant agents. The first GCs to be discovered, such as cortisol or dexamethasone, still represent the main treatment for conditions of the inflammatory process, despite the fact that they carry a significant risk of side effects. Hence, there is a continuing need to find drugs that preserve the immune effects of GCs without the side effects, such as those on metabolism (diabetes), bone tissue (osteoporosis), muscles (myopathy), eyes and skin. In this review, we focus on the recent use of ligand-based computational approaches in glucocorticoid receptor (GR) drug-design efforts for the determination of novel GR ligands. We examine a number of ligand-based (similarity searches, pharmacophore screens and quantitative structure-activity relationships) approaches that have been implemented in recent years. A recent virtual high-throughput screening similarity search was successful in developing a novel series of nonsteroidal GR antagonists. Additionally, there has been considerable success in ligand-based structure-analysis relationship generation and lead optimization studies for the GR. Future trends toward integrated GR ligand design incorporating ligand- and structure-based methodologies are inevitable.

Recent advances in the development of novel glucocorticoid receptor modulators

IMPORTANCE OF THE FIELD

The glucocorticoid receptor plays a number of fundamental roles in human physiology. Glucocorticosteroids are the ultimate anti-inflammatory and immunosuppressive agents highly efficacious in the treatment of serious diseases, but also associated with serious side effects. Improvement in the therapeutic profiles of drugs, acting at the glucocorticoid receptor, is highly desired and may potentially arise from the separation of their gene transactivating and gene transrepressing properties.

AREAS COVERED IN THIS REVIEW

The review summarizes progress towards novel glucocorticoid drug candidates as indicated by the patent applications over the last 2 years (2008 - 2009). A brief discussion of glucocorticoid receptor biology and previous drug candidates is included.

WHAT THE READER WILL GAIN

The understanding of the structural scope and biological profiles of the glucocorticoid receptor modulators, currently in preclinical and clinical development, based on the review of approximately 180 composition-of-matter and method-of-use patent applications.

TAKE HOME MESSAGE

The information on the good chemotypical diversity of glucocorticoid receptor modulators needs to be supplemented by the clinical data - presumably, soon to become available - to allow a look into a possible improvement in therapeutic index over the classic glucocorticosteroids.

Virtual screening for the identification of novel nonsteroidal glucocorticoid modulators

In this work, we describe the first application of ligand-based drug design (LBDD) to the derivation of a predictive pharmacophore for the human glucocorticoid receptor (hGR). Creation of a four feature pharmacophore in Catalyst was subsequently validated through a virtual screen of 264000 commercially available compounds. From a selected hit list of 11 diverse compounds, two nonsteroidal molecules demonstrated low micromolar activity against hGR as validated through fluorescence polarization competitive assay. Additionally, these compounds were tested for their trans-repression potential by their ability to inhibit IL-1 induced, IL-6 expression in the human A549 lung epithelial cell line. Co-treatment of A549 with 21 (MDG169) (10 microM) in combination with dexamethasone showed an improved inhibitory effect when compared to dexamethasone alone with the cooperative effect being dependent on the dexamethasone dose. Putative binding orientations in the hGR ligand binding domain crystal structure are presented. These compounds represent novel nonsteroidal hGR modulating scaffolds, rationally identified through ligand-focused computational modeling.

Role of prefrontal dopaminergic neurotransmission in glucocorticoid receptor-mediated modulation of methamphetamine-induced hyperactivity

Glucocorticoids are involved in psychostimulant-induced hyperactivity, but the exact mechanism is not known. This study used the selective glucocorticoid receptor antagonist, RU-43044, to determine whether prefrontal neurotransmission is involved in glucocorticoid-mediated modulation of methamphetamine (METH)-induced hyperactivity in mice. Pretreatment with RU-43044 (10-30 mg/kg) attenuated the increased spontaneous locomotor activity induced by METH (1-2 mg/kg). The psychostimulant effect of METH was also attenuated by adrenalectomy. RU-43044 inhibited METH-induced increases in extracellular dopamine (DA), but not serotonin (5-HT), levels in the prefrontal cortex, but did not affect METH-induced increases in extracellular DA levels in the nucleus accumbens shell, although it inhibited increases in extracellular 5-HT levels. Adrenalectomy also attenuated the METH-induced increases in extracellular DA levels in the prefrontal cortex. RU-43044 did not affect METH-induced increases in plasma corticosterone levels. These findings suggest that glucocorticoid receptors are involved in METH-induced hyperactivity, and that prefrontal dopaminergic neurotransmission plays a role in glucocorticoid-mediated modulation of METH-induced behavioral changes.

Antidepressant-like effects of the glucocorticoid receptor antagonist RU-43044 are associated with changes in prefrontal dopamine in mouse models of depression

Chronic corticosterone and isolation rearing paradigms may provide reliable mouse models of depression. Using these models, the present study examined if the specific glucocorticoid receptor antagonist, RU-43044, has an antidepressant-like effect, and studied the possible role of prefrontal neurotransmission on the behavioral effects. Chronic administration of corticosterone and isolation rearing increased the immobility time in the forced swim and tail suspension tests. Subchronic treatment with RU-43044 decreased the immobility time in the forced swim test in chronic corticosterone-treated and isolation-reared mice, but not the control mice. Chronic corticosterone decreased the levels of cortical glucocorticoid receptors and stress-induced increases in plasma corticosterone levels, and blocked the response of plasma corticosterone to dexamethasone, while isolation rearing did not cause any changes in the glucocorticoid receptor system. Both chronic corticosterone and isolation rearing markedly increased high K+ -induced dopamine release, but not serotonin release, in the prefrontal cortex. Subchronic RU-43044 reversed the enhanced release of dopamine in the prefrontal cortex of chronic corticosterone-treated and isolation-reared mice. These results suggest that chronic corticosterone and isolation rearing increase the depressive-like behavior in glucocorticoid receptor-dependent and independent manners, respectively, and that RU-43044 shows an antidepressant-like effect, probably via an inhibition of enhanced prefrontal dopaminergic neurotransmission in these mouse models.

Selective transrepression versus transactivation mechanisms by glucocorticoid receptor modulators in stress and immune systems

Glucocorticoids control immune homeostasis and regulate stress responses in the human body to a large extent via the glucocorticoid receptor. This transcription factor can modulate gene expression either through direct DNA binding (mainly resulting in transactivation) or independent of DNA binding (in the majority of cases resulting in transrepression). The aim of this review is to discuss the mechanistic basis and applicability of different glucocorticoid receptor modulators in various affections, ranging from immune disorders to mental dysfunctions.

1H-Pyrazolo[3,4-g]hexahydro-isoquinolines as selective glucocorticoid receptor antagonists with high functional activity

Addition of the 4-fluorophenylpyrazole group to the previously described 2-azadecalin glucocorticoid receptor (GR) antagonist 1 resulted in significantly enhanced functional activity. SAR of the bridgehead substituent indicated that whereas groups as small as methyl afforded high GR binding, GR functional activity was enhanced by larger groups such as benzyl, substituted ethers, and aminoalkyl derivatives. GR antagonists with binding and functional activity comparable to mifepristone were discovered (e.g., 52: GR binding K(i) 0.7 nM; GR reporter gene functional K(i) 0.6 nM) and found to be highly selective over other steroid receptors. Analogues 43 and 45 had >50% oral bioavailability in the dog.

Modulation of glucocorticoid action and the treatment of type-2 diabetes

The global epidemic of obesity and type-2 diabetes has heightened the need to understand the mechanisms that contribute to its pathogenesis and also to design and trial novel treatments. Patients with glucocorticoid (GC) excess--'Cushing's syndrome'--are phenotypically similar to patients with simple obesity. As such, much research has focused on the manipulation of local GC action as a therapeutic strategy. The majority of the classical actions of GCs are mediated via activation of the glucocorticoid receptor (GR). 11beta-Hydroxysteroid dehydrogenase type 1 (11beta-HSD1) converts inactive cortisone to cortisol and therefore amplifies local GC action. There is now a wealth of data from rodent and clinical studies implicating this conversion in the pathogenesis of obesity, type-2 diabetes, and the metabolic syndrome. Selective 11beta-HSD1 inhibitors (selective in that they block the activity of 11beta-HSD1 and not 11beta-HSD2 which inactivates cortisone to cortisol in mineralocorticoid target tissues) are currently in development although not yet available for use in clinical studies. Rodent studies utilizing these compounds have shown dramatic improvements in insulin sensitivity as well as improvements in lipid profiles and atherogenesis. A further experimental approach has been to design drugs that antagonize GR activation, and again these compounds appear to improve insulin sensitivity and lower glucose production rates. The key test for both of these research strategies is whether they will translate into clinical studies, and results from these trials are now eagerly awaited.

2-Benzenesulfonyl-8a-benzyl-hexahydro-2H-isoquinolin-6-ones as selective glucocorticoid receptor antagonists

The 2-azadecalin ring system was evaluated as a scaffold for the preparation of glucocorticoid receptor (GR) antagonists. High affinity, selective GR antagonists were discovered based on a hypothetical binding mode related to the steroidal GR antagonist RU-43044. 2-Benzenesulfonyl substituted 8a-benzyl-hexahydro-2H-isoquinolin-6-ones exemplified by (R)-37 had low nanomolar affinity for GR with moderate functional activity (200 nM) in a reporter gene assay. These compounds were devoid of affinity for other steroidal receptors (ER, AR, MR, and PR). Analogues based on an alternative putative binding mode (CP-like) were found to be inactive.

Discovery and optimization of novel, non-steroidal glucocorticoid receptor modulators

A virtual screening approach comprising a 3-D similarity search based on known GR modulators was used to identify a novel series of non-steroidal glucocorticoid receptor (GR) antagonists. Optimization of the initial hit to provide potent compounds which exhibit good selectivity against other steroidal nuclear hormone receptors is described.

Discovery of novel phosphorus-containing steroids as selective glucocorticoid receptor antagonist

Mifepristone is a non-selective antagonist of 3-oxosteroid receptors with both abortifacient and anti-diabetic activities. For glucocorticoid receptor (GR) program, we sought an unexplored, synthetically accessible phosphorus-containing steroidal mimetic of mifepristone, suitable for parallel synthesis of analogues. One compound 4a, with high oral bioavailability (59%) in rat, exhibited functional antagonism of GR in oral glucose tolerance test (OGTT). Thus this series of compounds might be potentially useful for the treatment of type II diabetes.

Discovery of 6-N,N-Bis(2,2,2-trifluoroethyl)amino- 4-trifluoromethylquinolin-2(1H)-one as a Novel Selective Androgen Receptor Modulator

The androgen receptor is a member of the extended family of nuclear receptors and is widely distributed throughout the body. Androgen therapy is used to compensate for low levels of the natural hormones testosterone (T) and dihydrotestosterone and consists of administration of T, prodrugs thereof, or synthetic androgens. However, currently available androgens have many drawbacks. We identified 6-dialkylamino-4-trifluoromethylquinolin-2(1H)-ones as orally available tissue-selective androgen receptor modulators.

Cholesterol Surrogates Incorporating a Benzophenone as Part of the Sterol Tetracycle

Photoactivatable analogues 4-6 of cholesterol (1), having their cross-linking site in the ring D sterol region, have been synthesized starting from bromotetralone 14 via enantioselective Robinson annulation to enone 13 and Suzuki carbonylative coupling to the appropriate phenylboronic acid. Each of 4-6 was shown to substitute successfully for 1 in an assay of apo A-I-induced cellular cholesterol efflux, indicating that these analogues equilibrated with 1 in all major cellular pools.

Classification and comparison of ligand-binding sites derived from grid-mapped knowledge-based potentials

We describe the application of knowledge-based potentials implemented in the MOE program to compare the ligand-binding sites of several proteins. The binding probabilities for a polar and a hydrophobic probe are calculated on a grid to allow easy comparison of binding sites of superimposed related proteins. The method is fast and simple enough to simultaneously use structural information of multiple proteins of a target family. The method can be used to rapidly cluster proteins into subfamilies according to the similarity of hydrophobic and polar fields of their ligand-binding sites. Regions of the binding site which are common within a protein family can be identified and analysed for the design of family-targeted libraries or those which differ for improvement of ligand selectivity. The field-based hierarchical clustering is demonstrated for three protein families: the ligand-binding domains of nuclear receptors, the ATP-binding sites of protein kinases and the substrate binding sites of proteases. More detailed comparisons are presented for serine proteases of the chymotrypsin family, for the peroxisome proliferator-activated receptor subfamily of nuclear receptors and for progesterone and androgen receptor. The results are in good accordance with structure-based analysis and highlight important differences of the binding sites, which have been also described in the literature.

Antidiabetic activity of passive nonsteroidal glucocorticoid receptor modulators

Much has been learned about the consequences of glucocorticoid receptor antagonism by studying steroidal active antagonists such as RU-38486 (1). In the liver glucocorticoid receptor antagonism suppresses hepatic glucose production decreasing plasma glucose levels; however, extrahepatic antagonism produces several undesirable side effects including activation of the hypothalamic pituitary adrenal axis. A series of nonsteroidal passive N-(3-dibenzylamino-2-alkyl-phenyl)-methanesulfonamide glucocorticoid receptor modulators was discovered. Liver selective and systemically available members of this series were found and characterized in diabetes and side effect rodent models. A highly liver selective member of this series, acid 14, shows efficacy in the ob/ob model of diabetes. It lowers plasma glucose, cholesterol, and free fatty acid concentrations and reduces the rate of body weight gain. The structurally related systemically available passive modulator 12 lowers glucose, HbA(1c), triglyceride, free fatty acid, and cholesterol levels. Interestingly, it did not acutely activate the hypothalamic pituitary adrenal axis in unstressed CD-1 mice or have the abortive effects observed with 1. These results indicate that passive GR antagonists may have utility as antidiabetic agents.

Reduction of hepatic and adipose tissue glucocorticoid receptor expression with antisense oligonucleotides improves hyperglycemia and hyperlipidemia in diabetic rodents without causing systemic glucocorticoid antagonism

Glucocorticoids (GCs) increase hepatic gluconeogenesis and play an important role in the regulation of hepatic glucose output. Whereas systemic GC inhibition can alleviate hyperglycemia in rodents and humans, it results in adrenal insufficiency and stimulation of the hypothalamic-pituitary-adrenal axis. In the present study, we used optimized antisense oligonucleotides (ASOs) to cause selective reduction of the glucocorticoid receptor (GCCR) in liver and white adipose tissue (WAT) and evaluated the resultant changes in glucose and lipid metabolism in several rodent models of diabetes. Treatment of ob/ob mice with GCCR ASOs for 4 weeks resulted in approximately 75 and approximately 40% reduction in GCCR mRNA expression in liver and WAT, respectively. This was accompanied by approximately 65% decrease in fed and approximately 30% decrease in fasted glucose levels, a 60% decrease in plasma insulin concentration, and approximately 20 and 35% decrease in plasma resistin and tumor necrosis factor-alpha levels, respectively. Furthermore, GCCR ASO reduced hepatic glucose production and inhibited hepatic gluconeogenesis in liver slices from basal and dexamethasone-treated animals. In db/db mice, a similar reduction in GCCR expression caused approximately 40% decrease in fed and fasted glucose levels and approximately 50% reduction in plasma triglycerides. In ZDF and high-fat diet-fed streptozotocin-treated (HFD-STZ) rats, GCCR ASO treatment caused approximately 60% reduction in GCCR expression in the liver and WAT, which was accompanied by a 40-70% decrease in fasted glucose levels and a robust reduction in plasma triglyceride, cholesterol, and free fatty acids. No change in circulating corticosterone levels was seen in any model after GCCR ASO treatment. To further demonstrate that GCCR ASO does not cause systemic GC antagonism, normal Sprague-Dawley rats were challenged with dexamethasone after treating with GCCR ASO. Dexamethasone increased the expression of GC-responsive genes such as PEPCK in the liver and decreased circulating lymphocytes. GCCR ASO treatment completely inhibited the increase in dexamethasone-induced PEPCK expression in the liver without causing any change in the dexamethasone-induced lymphopenia. These studies demonstrate that tissue-selective GCCR antagonism with ASOs may be a viable therapeutic strategy for the treatment of the metabolic syndrome.

Selective glucocorticoid receptor nonsteroidal ligands completely antagonize the dexamethasone mediated induction of enzymes involved in gluconeogenesis and glutamine metabolism

Glucocorticoids (GCs) are vital multi-faceted hormones with recognized effects on carbohydrate, protein and lipid metabolism. Previous studies with the steroid antagonist, RU486 have underscored the essential role of GCs in the regulation of these metabolic pathways. This article describes the discovery and characterization of novel GRalpha selective nonsteroidal antagonists (NSGCAs). NSGCAs 2 and 3 are spirocyclic dihydropyridine derivatives that selectively bind the GRalpha with IC(50s) of 2 and 1.5 nM, respectively. Importantly, these compounds are full antagonists of the induction by dexamethasone (Dex) of marker genes for glucose and glutamine metabolism; the tyrosine amino transferase (TAT) and glutamine synthetase (GS) enzymes, respectively. In contrast, GC-dependent transcriptional repression of the collagenase 1 (MMP-1) enzyme, an established GRalpha responsive proinflammatory gene; is poorly antagonized by these compounds. These NSGCAs might have useful applications as tools in metabolic research and drug discovery.

The glucocorticoid receptor antagonist mifepristone reduces ethanol intake in rats under limited access conditions

There is a substantial amount of evidence indicating control over ethanol intake by steroid hormones, particularly adrenal glucocorticoids. Thus far, however, studies employing pharmacological methods have failed to find effects of glucocorticoid receptor blockade on voluntary ethanol consumption. Since length of ethanol access period can influence ethanol consumption levels as well as potential pharmacological effects in such studies, the present study was conducted to determine the effects of acute administration of the glucocorticoid receptor (GR) antagonist mifepristone on voluntary ethanol intake under limited access conditions. Rats were fluid restricted and given concurrent access to 10% ethanol and water in a two-bottle choice paradigm for 1 h/day, 5 days a week. Both fluids were available ad libitum during the remaining 2 days per week. Administration of mifepristone (1, 5 and 20 mg/kg i.p.) immediately prior to the limited access two-bottle access period dose-dependently suppressed ethanol intake (maximum 40% at 20 mg/kg). The mineralcorticoid receptor (MR) antagonist spironolactone (10, 25 and 50 mg/kg i.p.) was without effect on ethanol intake, and neither compound had an effect on water intake. These data confirm an active role of GRs in modulating voluntary ethanol consumption, particularly under conditions of limited access.

Synthesis, activity, metabolic stability, and pharmacokinetics of glucocorticoid receptor modulator–statin hybrids

The synthesis, activity, metabolic stability, and pharmacokinetics of steroidal and nonsteroidal glucocorticoid receptor modulator-statin hybrids is reported. Potent steroidal antagonist-statin hybrids like 22 (h-GR binding IC(50)=7 nM) and nonsteroidal modulator hybrids like 16 (h-GR binding IC(50)=2 nM) were discovered. Appending a 'statin'-like diol-acid group to the modulators dramatically improved metabolic stability (and in some cases hepatocyte activity), but did not impart hepatoselectivity.

Synthesis and biological evaluation of novel, selective, nonsteroidal glucocorticoid receptor antagonists

We report the discovery of a novel class of glucocorticoid receptor (GR) antagonists based on the chromene molecular scaffold. The compounds exhibit good functional potency and an improved receptor selectivity profile for GR over other steroid receptors when compared to the classical steroidal GR-antagonist, RU-486.