Small molecular anti-cytokine agents

The role of evolutionarily conserved signalling systems in Echinococcus multilocularis development and host-parasite interaction

Alveolar echinococcosis, one of the most serious and life-threatening zoonoses in the world, is caused by the metacestode larval stage of the fox-tapeworm Echinococcus multilocularis. Mostly due to its accessibility to in vitro cultivation, this parasite has recently evolved into an experimental model system to study larval cestode development and associated host-parasite interaction mechanisms. Respective advances include the establishment of axenic in vitro cultivation systems for parasite larvae as well as culture systems by which the early development of metacestode vesicles from totipotent parasite stem cells can be reconstituted under controlled laboratory conditions. A series of evolutionarily conserved signalling molecules of the insulin, epidermal growth factor and transforming growth factor-beta pathways that are able to functionally interact with corresponding host cytokines have been described in E. multilocularis and most likely play a crucial role in parasite development within the liver of the intermediate host. Furthermore, a whole genome sequencing project has been initiated by which a comprehensive picture on E. multilocularis cell-cell communication systems will be available in due time, including information on parasite cytokines that are secreted towards host tissue and thus might affect the immune response. In this article, an overview of our current picture on Echinococcus signalling systems will be given, and the potential to exploit these pathways as targets for anti-parasitic chemotherapy will be discussed.

"Go upstream, young man": lessons learned from the p38 saga

Despite the success of biological therapies in rheumatoid arthritis (RA), orally active small-molecule drugs are desirable. Signal transduction inhibitors have been the focus of intense efforts, with some recent notable successes and failures. p38alpha is a signalling molecule that regulates proinflammatory cytokines, which makes it a logical target for RA. Unfortunately, selective p38alpha inhibitors have limited efficacy. An attempt is made here to put these studies into perspective and offer possible explanations for the failure of p38alpha blockers. Alternative strategies, such as targeting kinases higher in the signalling cascade or using less selective compounds, might be more successful as suggested by the efficacy seen with Syk and JAK inhibitors.

Modulation of TNFalpha, IL-10 and IL-12p40 levels by a ceramide-1-phosphate analog, PCERA-1, in vivo and ex vivo in primary macrophages

Phospho-ceramide analog-1 (PCERA-1) has been described as a potent in vivo suppressor of the pro-inflammatory cytokine tumor necrosis factor alpha (TNFalpha), and thus as a putative drug for the treatment of inflammatory diseases. However, the in vivo cell target of PCERA-1 has not been identified, and its in vivo effect on secretion of other relevant cytokines has not been reported. We have previously shown that PCERA-1 suppresses lipopolysaccharide (LPS)-induced TNFalpha production in RAW264.7 macrophages in vitro. We therefore hypothesized that PCERA-1 targets TNFalpha production by primary macrophages. In this study we thus investigated the effect of PCERA-1 on LPS-induced release of TNFalpha, interleukin (IL)-10 and IL-12p40, in vivo, and ex vivo. We found that PCERA-1 suppressed production of the pro-inflammatory cytokines, TNFalpha and IL-12p40, and increased production of the anti-inflammatory cytokine, IL-10, in LPS-challenged mice, and in primary peritoneal macrophages as well as bone marrow-derived macrophages (BMDM) stimulated with LPS and interferon (IFN)-gamma. These activities of PCERA-1 were independent of each other. In contrast, PCREA-1 only slightly affected TNFalpha production in the whole blood assay, where LPS-induced cytokines are mainly produced by monocytes. Moreover, isolated blood monocytes were inert to PCERA-1, but acquired responsiveness to PCERA-1 upon macrophage colony stimulating factor (M-CSF)-induced differentiation into macrophages. Pharmacokinetic analysis in mice showed that while the volume of distribution of PCERA-1 is low, the drug was rapidly exchanged between the peritoneum and the systemic circulation. Together, these results suggest that sensitivity to PCERA-1 increases upon differentiation of blood monocytes into tissue macrophages, and imply a mechanistic role for peritoneal macrophages in the in vivo anti-inflammatory activity of PCERA-1. Finally, we show that the mechanism of activity of PCERA-1 and prostaglandin E2 (PGE2) is distinct, and that PCERA-1 signaling is not mediated by EP2, a PGE2 receptor which is also activated by oxidized phospholipids. The independent and reciprocal modulation of production of TNFalpha and IL-12p40, vs. IL-10, suggests that PCERA-1 may be a candidate drug for the treatment of inflammation-linked diseases.

Investigations of SCIO-469-like compounds for the inhibition of p38 MAP kinase

The p38 MAP kinase is implicated in the release of the pro-inflammatory cytokines TNFalpha and IL-1b. Inhibition of cytokine release may be a useful treatment for inflammatory conditions such as rheumatoid arthritis and Crohn's disease. A new lead structure for p38 MAP kinase inhibition was identified. Herein, we report the SAR of this new class of p38 inhibitors.

Targeting the ribose and phosphate binding site of p38 mitogen-activated protein (MAP) kinase: synthesis and biological testing of 2-alkylsulfanyl-, 4(5)-aryl-, 5(4)-heteroaryl-substituted imidazoles

Three series of substituted 2-alkylsulfanyl-4-(4-fluorophenyl)imidazoles, 5-pyridinyl-, 1-methyl-5-pyridinyl-, and 5-(2-aminopyridin-4-yl)-imidazoles, were prepared and tested for their ability to inhibit p38 MAP kinase and TNF-alpha release. These compounds were prepared by using different synthetic routes. They were tested by applying a nonradioactive p38 MAP kinase assay and by measurement of TNF-alpha release in human whole blood. Potent inhibitors (IC50 values in the low nanomolar range, as low as 2 nM in the enzyme assay and 37 nM in the human whole blood test) were identified by variation of substituents at the imidazole- C2-thio position as well as at the 2-aminopyridinyl functionality. In contrast to other known kinase inhibitors, these novel imidazole derivatives with the substituents at the imidazole-C2-thio position may interact with the ribose as well as with the phosphate binding site of the p38 MAP kinase.

The identification of pyrazolo[1,5-a]pyridines as potent p38 kinase inhibitors

A series of pyrazolo[1,5-a]pyridine derivatives was designed and synthesized as novel potent p38 kinase inhibitors. Our approaches towards improving in vitro metabolism and in vivo pharmacokinetic properties of the series are described.

Computational structure-activity relationship analysis of non-peptide inducers of macrophage tumor necrosis factor-alpha production

Previously, we screened a series of arylcarboxylic acid hydrazide derivatives for their ability to induce macrophage tumor necrosis factor alpha (TNF-alpha) production and identified 16 such compounds. In the present study, we evaluated 23 additional arylcarboxylic acid hydrazides and found that seven of these compounds also induced macrophage TNF-alpha production, representing novel compounds with this activity. The total set of active compounds was then used for computational structure-activity relationship (SAR) analysis to further optimize lead molecules. A sequence of (1) linear discriminant analysis, (2) classification tree analysis with linear combination, and (3) univariate splits based on atom pair descriptors led to the derivation of SAR rule-based algorithms with fitting accuracy of 96.5%, 91.9%, and 84.9%, respectively. The SAR rules obtained from classification tree analysis with univariate splits, which was based on three atom pair descriptors only, revealed that the main factors influencing agonist activity of arylcarboxylic acid hydrazide derivatives were the presence of a methyl or trifluoromethyl group in the benzene ring attached to the furan moiety, an alkoxy group in the aromatic ring near the methylenehydrazide linker, and two or more halogen atoms (chlorine or bromine) on one side of the dumbbell-shaped hydrazide molecule opposed by an aromatic moiety on the opposite side of the molecule. Thus, these rules represent a relatively simple classification approach for de novo design of small-molecule inducers of macrophage TNF-alpha production.

Mechanisms modulating inflammatory osteolysis: a review with insights into therapeutic targets

Inflammatory osteolysis is a relatively frequent and incapacitating complication of rheumatoid arthritis and multiple other inflammation-associated bone diseases. It is thought to operate through an ultimate common pathway of accelerated osteoclast recruitment and activation under the control of cytokines produced in the inflammatory environment. Over the past decade, there have been major advances in our understanding of the mechanisms of osteoclastogenesis. It is now clear that the interaction of receptor activator NF-kappaB (RANK) and its ligand, RANKL, plays a central role in osteoclast formation and activity. Therefore, understanding osteoclastogenesis offers new pathways for potential therapeutic intervention in inflammatory osteolysis. The success of anti-tumor necrosis factor-alpha and interleukin-1 therapy highlights the central role that these specific cytokines play in this disease. This review outlines our current understanding of the mechanisms mediating inflammatory osteolysis and highlights potential therapeutic strategies.

Characterization and inhibition of a p38-like mitogen-activated protein kinase (MAPK) from Echinococcus multilocularis: antiparasitic activities of p38 MAPK inhibitors

Alveolar echinococcosis (AE), caused by the metacestode larval stage of the fox-tapeworm Echinococcus multilocularis, is a life-threatening disease with very limited treatment options. In search for novel drug targets, we concentrate on factors of the cellular signaling machinery and report herein the characterization of a novel gene, Emmpk2, which is expressed in the parasite's larval stage and which codes for a member of the mitogen-activated protein kinase (MAPK) family. On the amino acid sequence level, the encoded protein, EmMPK2, shares considerable homologies with p38 MAPKs from a wide variety of animal organisms but also displays several distinct differences, particularly in amino acid residues known to be involved in the regulation of enzyme activity. Upon heterologous expression in Escherichia coli, purified EmMPK2 showed prominent autophosphorylation activity and strongly elevated basal activity towards a MAPK substrate, when compared to the closest human orthologue, p38-alpha. EmMPK2 activity could be effectively inhibited in the presence of ML3403 and SB202190, two ATP-competitive pyridinyl imidazole inhibitors of p38 MAPKs, in a concentration-dependent manner. When added to in vitro cultivated metacestode vesicles, SB202190 and particularly ML3403 led to dephosphorylation of EmMPK2 in the parasite and effectively killed parasite vesicles at concentrations that did not affect cultivated mammalian cells. Taken together, these results identify pyridinyl imidazoles as a novel class of anti-Echinococcus compounds and EmMPK2 as a promising target for the development of drugs against alveolar echinococcosis.

Are MAP kinases drug targets? Yes, but difficult ones

Pharmaceutical companies are facing an increasing interest in new target identification and validation. In particular, extensive efforts are being made in the field of protein kinase inhibitors research and development, and the past ten years of effort in this field have altered our perception of the potential of kinases as drug targets. Therefore, in the drug discovery process, the selection of relevant, susceptible protein kinase targets combined with searches for leads and candidates have become a crucial approach. The success of recent launches of protein kinase inhibitors (Gleevec, Imatinib, Sutent, Iressa, Nexavar, Sprycel) gave another push to this field. Numerous other kinase inhibitors are currently undergoing clinical trials or clinical development. Some questions are nevertheless unanswered, mostly related to the great number of known kinases in the human genome, to their similarity with each other, to the existence of functionally redundant kinases for specific pathways, and also because the connection between particular pathways and diseases is not always clear. The review is leading the reader through a panoramic view of protein kinase inhibition with a major focus on MAPK, successful examples and clinical candidates.

Methyl 4-[5-(4-fluorophenyl)-4-(pyridin-4-yl)-1H-imidazol-2-ylsulfanyl]butanoate

The title compound, C₁₉H₁₈FN₃O₂S, was synthesized in the course of studies on 2-alkyl­sufanylimidazoles as p38 mitogen-activated protein kinase inhibitors. The synthesis was achieved by nucleophilic substitution of 4-(4-fluoro­phen­yl)-5-(pyridin-4-yl)-1,3-dihydro­imidazole-2-thione with methyl 4-bromo­butanoate. The five-membered heterocycle makes dihedral angles of 32.4 (2) and 18.3 (2)° with the fluoro­phenyl and pyridinyl rings, respectively, indicating a low degree of conjugation between these rings. Intra­molecular C—H⋯N and inter­molecular N—H⋯N hydrogen bonds as well as C—H⋯π inter­actions seem to be effective in stabilization of the crystal structure.

Pyrazolo-pyrimidines: a novel heterocyclic scaffold for potent and selective p38 alpha inhibitors

The synthesis and structure-activity relationships (SAR) of p38 alpha MAP kinase inhibitors based on a pyrazolo-pyrimidine scaffold are described. These studies led to the identification of compound 2x as a potent and selective inhibitor of p38 alpha MAP kinase with excellent cellular potency toward the inhibition of TNFalpha production. Compound 2x was highly efficacious in vivo in inhibiting TNFalpha production in an acute murine model of TNFalpha production. X-ray co-crystallography of a pyrazolo-pyrimidine analog 2b bound to unphosphorylated p38 alpha is also disclosed.

Synthesis and SAR of new pyrrolo[2,1-f][1,2,4]triazines as potent p38 alpha MAP kinase inhibitors

A novel series of compounds based on the pyrrolo[2,1-f][1,2,4]triazine ring system have been identified as potent p38 alpha MAP kinase inhibitors. The synthesis, structure-activity relationships (SAR), and in vivo activity of selected analogs from this class of inhibitors are reported. Additional studies based on X-ray co-crystallography have revealed that one of the potent inhibitors from this series binds to the DFG-out conformation of the p38 alpha enzyme.

Drugs and their molecular targets: an updated overview

About 330 targets bind approved drugs, 270 encoded by the human genome and 60 belonging to pathogenic organisms. A large number of druggable targets have been recently proposed from preclinical and first clinical data, but a huge reservoir of putative drug targets, possibly several thousands, remains to be explored. This overview considers the different types of ligands and their selectivity in the main superfamilies of drug targets, enzymes, membrane transporters and ion channels, and the various classes of membrane and nuclear receptors with their signalling pathway. Recently approved drugs such as monoclonal antibodies, tyrosine kinase and proteasome inhibitors, and major drugs under clinical studies are reviewed with their molecular target and therapeutic interest. The druggability of emerging targets is discussed, such as multidrug resistance transporters and cystic fibrosis transmembrane conductance regulator (CFTR), hyperpolarization-activated cyclic nucleotides-gated (HCN), cyclic nucleotide-gated (CNG) and transient receptor potential (TRP) ion channels, tumour necrosis factor (TNF) and receptor activator of NFkappaB (RANK) receptors, integrins, and orphan or recently deorphanized G-protein-coupled and nuclear receptors. Large advances have been made in the therapeutical use of recombinant cytokines and growth factors (i.e. tasonermin, TNFalpha-1a; becaplermin, platelet-derived growth factor (PDGF); dibotermin-alpha, bone morphogenetic proteins (BMP)2; anakinra, interleukin-1 receptor antagonist protein (IRAP), and in enzyme replacement therapy, i.e. algasidase (alpha-galactosidase) and laronidase (alpha-l-iduronidase). New receptor classes are emerging, e.g. membrane aminopeptidases, and novel concepts are stimulating drug research, e.g. epigenetic therapy, but the molecular target of some approved drugs, such as paracetamol and imidazolines, still need to be identified.

The discovery of (R)-2-(sec-butylamino)-N-(2-methyl-5-(methylcarbamoyl)phenyl) thiazole-5-carboxamide (BMS-640994)-A potent and efficacious p38alpha MAP kinase inhibitor

A novel structural class of p38alpha MAP kinase inhibitors has been identified via iterative SAR studies of a focused deck screen hit. Optimization of the lead series generated 6e, BMS-640994, a potent and selective p38alpha inhibitor that is orally efficacious in rodent models of acute and chronic inflammation.

Pyrazinoindolone inhibitors of MAPKAP-K2

Optimization of pyrazinoindolone inhibitors of MAPKAP-K2 (MK2) provides a reasonable balance of cellular potency and physicochemical properties. Mechanistic studies support the inhibition of MK2 which is responsible for the sub-micromolar cellular efficacy.

Synthesis and SAR of p38α MAP kinase inhibitors based on heterobicyclic scaffolds

The synthesis and structure-activity relationships (SAR) of p38alpha MAP kinase inhibitors based on heterobicyclic scaffolds are described. This effort led to the identification of compound (21) as a potent inhibitor of p38alpha MAP kinase with good cellular potency toward the inhibition of TNF-alpha production. X-ray co-crystallography of an oxalamide analog (24) bound to unphosphorylated p38alpha is also disclosed.

Emerging targets of biologic therapies for rheumatoid arthritis

Advances in molecular biology and the clinical success of strategies that target tumor necrosis factor (TNF) have led to further research into the pathophysiology of human rheumatoid arthritis. Several novel therapeutic targets have emerged from these efforts, including not only molecules that regulate TNF (e.g. TNF-alpha converting enzyme), the complex cytokine network (e.g. interleukin [IL]-6, IL-15, IL-17) and several adipokines, but also targets that originate from cellular and subcellular components of the disease. Strategies that aim at cellular targets include antibodies to CD20 or BLyS (also known as TNF ligand family member 13b), which deplete or inhibit B cells, as well as approaches that interfere with membrane-derived microparticles. Components of subcellular pathways, which are predominantly upstream of the central regulator of transcription nuclear factor kappaB, have also been studied. Of these, strategies that target mitogen-activated protein kinases have a leading role and are on the verge of clinical use; approaches that target specific molecules such as Janus kinases, signal transducer and activator of transcription proteins, and suppressor of cytokine signaling proteins also seem to show promise and might have a clinical application in the future.

In vitro, ex vivo and in vivo immunopharmacological activities of the isoxazoline compound VGX-1027: Modulation of cytokine synthesis and prevention of both organ-specific and systemic autoimmune diseases in murine models

We have presently studied the in vitro, ex vivo and in vivo immunopharmacological effects of VGX-1027 [(S,R)-3-phenyl-4,5-dihydro-5-isoxasole acetic acid]. This compound reduced the secretion of IL-1beta, TNF-alpha and IL-10 from purified murine macrophages stimulated "in vitro" with lipopolysaccharide (LPS), and it also modified the signaling pathways induced in these cells by LPS entailing reduced activation of NF-kappaB and p38 MAP kinase pathways along with up-regulation of ERK pathways. VGX-1027 appeared to spare T cell function as it was unable to modify the proliferation and/or secretion of IL-2, IFN-gamma and IL-4 induced in purified murine CD4+ T cells from stimulation with either CD3+CD28 or ConA. These effects on macrophages may account for the capacity of VGX-1027 to markedly ameliorate the course of both acute and chronic immunoinflammatory diseases in mice such as carrageenan-induced pleurisy, LPS-induced lethality and type II collagen-induced arthritis. Acute and subacute toxicological studies show that the drug is not toxic at the doses that exert biological effects in these preclinical models. These data warrant additional studies for the potential use of VGX-1027 in the clinical setting.

Pharmacokinetics of ML3403 ({4-[5-(4-Fluorophenyl)-2-methylsulfanyl-3H-imidazol-4-yl]-pyridin-2-yl}-(1-phenylethyl)-amine), a 4-Pyridinylimidazole-Type p38 Mitogen-Activated Protein Kinase Inhibitor

The p38 mitogen-activated protein kinase (MAPK) is a key mediator in cytokine-induced signaling events that are activated in response to a variety of extracellular stimuli such as stress factors, apoptosis, and proliferation. Therefore, the MAPK family plays an integral role in disease states including oncogenesis, autoimmune diseases, and inflammatory processes. Inhibition of these protein kinases represents an attractive strategy for therapeutic intervention. In particular, one class of p38 MAP kinase inhibitors, the pyridinyl imidazole derivatives, is intensely investigated by several industrial groups, but so far no studies concerning the metabolism of these structurally related substances seem to be available. The objective of our examinations was the preclinical characterization of ML3403, {4-[5-(4-fluorophenyl)-2-methylsulfanyl-3H-imidazol-4-yl]-pyridin-2-yl}-(1-phenylethyl)-amine, a potent inhibitor of p38 MAP kinase, comprising the basic pyridinyl imidazole structure. In human hepatic microsomal incubations, the sulfoxidation to ML3603 ({4-[5-(4-fluorophenyl)-2-methylsulfinyl-3H-imidazol-4-yl]-pyridin-2-yl}-(1-phenylethyl)-amine) and M-sulfone ({4-[5-(4-fluorophenyl)-2-methylsulfonyl-3H-imidazol-4-yl]-pyridin-2-yl}-(1-phenylethyl)-amine) was found to be the predominant metabolic transformation. In addition, oxidative removal of the phenylethyl moiety, pyridine N-oxidation, and hydroxylation reactions were observed. Incubations were carried out with hepatic microsomes from various species and with recombinant human cytochrome P450 isoenzymes, showing that CYP1A2, CYP2C19, CYP2D6, and CYP3A4 are the prominent enzymes in the metabolism of ML3403. Michaelis-Menten kinetics of ML3603 formation by these recombinant isoenzymes showed that CYP3A4 plays a pivotal role in the sulfoxidation reaction. In addition, pharmacokinetics of ML3403 were evaluated in male and female Wistar rats after oral gavage, showing a fast and high conversion to its active sulfoxide metabolite ML3603. A remarkable gender-specific difference in the systemic exposure to ML3403 and ML3603 was found in rats. No gender-specific difference was detected in incubations with human liver microsomes.

From five- to six-membered rings: 3,4-diarylquinolinone as lead for novel p38MAP kinase inhibitors

In this study we describe the design, synthesis, and biological evaluation of 3-(4-fluorophenyl)-4-pyridin-4-ylquinoline-2(1H)-one (5) as a new inhibitor of MAPK with a p38alphaMAPK IC50 of 1.8 muM. By keeping the common vicinal pyridine/4-F-phenyl pharmacophore, such as in prototypical imidazole 20 or isoxazole 13 but in 5 connected to the six-membered quinoline core, we were particularly interested in comparing biological activity, details of molecular geometry, and different binding modes of these compounds. Compounds 20 and 13 were active both in the p38alpha- and JNK3-assay, whereas 5 was selective for p38alpha, with no JNK3 inhibition. By comparing the X-ray structures of the compounds, we found a significantly larger distance between the pyridine and the 4-F-phenyl moiety in five-membered core structures relevant for ligand-protein interactions. Molecular modeling studies support the results based on differences in the ATP pockets of p38alpha and JNK3. Because most five-membered core based p38alpha inhibitors show also activity for JNK3, compound 5 is an interesting lead for selective p38alpha inhibitors.

Anti-tumour necrosis factor-alpha therapy in heart failure: future directions

The elevated level of tumour necrosis factor-alpha (TNF-alpha) in patients with heart failure has triggered interest in investigating the role of TNF-alpha in the pathogenesis of heart failure. Both clinical and experimental evidence has suggested that high levels of TNF-alpha occur in heart failure and lead to progression of left ventricular dysfunction. In addition, it has been documented that inhibition of TNF-alpha reverses its deleterious effects in heart failure. A number of clinical trials have been initiated to investigate the effect of anti-TNF-alpha therapy in patients with heart failure. The discouraging results of recent clinical trials of anti-TNF-alpha therapy in patients with heart failure have raised a number of questions about the role of TNF-alpha in heart failure. The present review critically analyzes the reasons of failure of anti-TNF-alpha therapy in heart failure. Moreover the potential approaches for the development of new anti-TNF-alpha therapy has been discussed which may open new vista of the management of heart failure.

p38 MAPK as a potential therapeutic target for inflammatory osteolysis

Inflammatory osteolysis is a relatively frequent and incapacitating complication of rheumatoid arthritis and other inflammatory diseases, and is induced by accelerated osteoclast recruitment and activation in bone under the aegis of cytokines produced in the inflammatory environment. The success of antitumor necrosis factor-alpha and interleukin-1 therapy in correcting this condition highlights the central role of these cytokines in this process. Recent years have witnessed a revolution in understanding the molecular mechanism and pathogenesis of this family of diseases. It is now clear that p38 mitogen-activated protein kinase plays an essential role in the production of proinflammatory cytokines and cytokine-induced osteoclastogenesis, thus providing a potential therapeutic target for prevention of pathologic bone loss.

Inflammatory factors in age-related muscle wasting

PURPOSE OF REVIEW

This review focuses on recent evidence pointing to the importance of inflammatory factors in the onset and progression of age-related muscle wasting, also known as sarcopenia, and discusses critical areas of uncertainty within the literature that require further development in order to identify novel therapeutics.

RECENT FINDINGS

The research performed in recent years has only strengthened the evidence that inflammatory factors are important in the progression of a catabolic state in muscle wasting. Interactions among various inflammatory cytokines and anabolic factors have been observed, with the balance skewed in favor of catabolism in sarcopenia. Adiposity appears to play an important role in the inflammatory process and possibly the onset of sarcopenia. Inflammatory factors are likely to play an important role in the increased activity of the ubiquitin proteasome, which we argue should be a primary target for the development of molecular therapeutics.

SUMMARY

Future research will need to delve into the molecular interactions that link inflammatory factors and the imbalance between muscle anabolism and catabolism that develops with aging. Identification of specific pathways of importance to sarcopenia will have relevance to a wide range of wasting disorders.

Emerging drugs for psoriasis

Psoriasis is a chronic immune-mediated inflammatory skin disease characterised by abnormal keratinocyte differentiation and proliferation. The immunopathogenesis is complex and novel evidence shows the involvement of both innate and adaptive immune response. Type 1 T cells and their effector cytokines play a pivotal role. Several drugs under preclinical and clinical development for psoriasis are directed against the immune response, targeting activation or proliferation of T cells, their trafficking and skin-homing, or effector cytokines. Among these, great attention has been given to TNF-alpha, following the demonstration of effectiveness of anti-TNF-alpha biologicals, and to IFN-gamma inducers. Another appealing approach concerns drugs capable of inducing immunological tolerance. Progress made in the recognition of intracellular events has prompted the development of small molecules and oligonucleotides that can inhibit specific molecular targets. There is, however, a plethora of other emerging drugs, clearly suggestive of the current interest for psoriasis, which are briefly described in this paper.

Preclinical pharmacokinetics and metabolism of 6-(4-(2,5-difluorophenyl)oxazol-5-yl)-3-isopropyl-[1,2,4]-triazolo[4,3-a]pyridine, a novel and selective p38α inhibitor: identification of an active metabolite in preclinical species and human liver microsomes

The disposition of 6-(4-(2,5-difluorophenyl)oxazol-5-yl)-3-isopropyl-[1,2,4]-triazolo[4,3-a]pyridine (1), a potent and selective inhibitor of mitogen activated protein (MAP) kinase p38alpha, was characterized in several animal species in support of its selection for preclinical safety studies and potential clinical development. 1 demonstrated generally favorable pharmacokinetic properties in all species examined. Following intravenous (i.v.) administration, 1 exhibited low volumes of distribution at steady state (Vd(ss)) ranging from 0.4-1.3 l/kg (2.4-26 l/m(2)) in the rat, dog and monkey. Systemic plasma clearance was low in cynomolgus monkeys (6.00 ml/min/kg, 72.0 ml/min/m(2)) and Sprague-Dawley rats (7.65+/-1.08 ml/min/kg, 45.9+/-6.48 ml/min/m(2) in male rats and 3.15+/-0.27 ml/min/kg, 18.9+/-1.62 ml/min/m(2) in female rats) and moderate in beagle dogs (12.3+/-5.1 ml/min/kg, 246+/-102 ml/min/m(2)) resulting in plasma half-lives ranging from 1 to 5 h in preclinical species. Moderate to high bioavailability of 1 was observed in rats (30-65%), dogs (87%) and monkeys (40%) after oral (p.o.) dosing consistent with the in vitro absorption profile of 1 in the Caco-2 permeability assay. In rats, the oral pharmacokinetics were dose dependent over the dose range studied (5, 50 and 100 mg/kg). The principal route of clearance of 1 in rat, dog, monkey and human liver microsomes and in vivo in preclinical species involved oxidative metabolism mediated by cytochrome P450 enzymes. The major metabolic fate of 1 in preclinical species and humans involved hydroxylation on the isopropyl group to yield the tertiary alcohol metabolite 2. In human liver microsomes, this transformation was catalysed by CYP3A4 as judged from reaction phenotyping analysis using isozyme-specific inhibitors and recombinant CYP enzymes. Metabolite 2 was also shown to possess inhibitory potency against p38alpha in a variety of in vitro assays. 1 as well as the active metabolite 2 were moderately to highly bound to plasma proteins (f(u) approximately 0.1-0.33) in rat, mouse, dog, monkey and human. 1 as well as the active metabolite 2 did not exhibit competitive inhibition of the five major cytochrome P450 enzymes namely CYP1A2, 2C9, 2C19, 2D6 and 3A4 (IC(50)>50 microM). Overall, these results indicate that the absorption, distribution, metabolism and excretion (ADME) profile of 1 is relatively consistent across preclinical species and predict potentially favorable pharmacokinetic properties in humans, supporting its selection for toxicity/safety assessment studies and possible investigations in humans as an anti-inflammatory agent.