Anti-eosinophil activity and clinical efficacy of the CRTH2 antagonist OC000459 in eosinophilic esophagitis

Eosinophilic esophagitis: overview of clinical management

A validated disease-specific symptom-assessment tool for eosinophilic esophagitis (EoE) has yet to be approved by regulatory authorities for use in clinical trials. Relevant end points for daily practice include EoE-related symptoms and esophageal eosinophilic inflammation. Endoscopic features should also be taken into account when establishing a therapy plan. A reasonable clinical goal is to achieve a reduction in EoE-related symptoms and esophageal eosinophilic inflammation. Evidence is increasing to support an anti-inflammatory maintenance therapy, as this can reduce esophageal remodeling. In EoE patients in clinical remission, annual disease monitoring with symptom, endoscopic, and histologic assessments of sustained treatment response is recommended.

Eosinophilic esophagitis: historical perspective on an evolving disease

Initial case series describing children and adults with symptoms related to esophageal dysfunction and dense esophageal eosinophilia lead to recognition of a "new" disease, eosinophilic esophagitis (EoE). Clinical, basic, and translational studies have provided a deeper understanding of this somewhat enigmatic disease that mechanistically is defined as an antigen-driven condition limited to the esophagus. This article summarizes many of the key historical features of EoE and provides a glimpse of potential future developments.

Allergic mechanisms in eosinophilic esophagitis

Eosinophilic esophagitis is rapidly increasing in incidence. It is associated with food antigen-triggered, eosinophil-predominant inflammation, and the pathogenic mechanisms have many similarities to other chronic atopic diseases. Studies in animal models and from patients have suggested that allergic sensitization leads to food-specific IgE and T-helper lymphocyte type 2 cells, both of which seem to contribute to the pathogenesis along with basophils, mast cells, and antigen-presenting cells. In this review our current understandings of the allergic mechanisms that drive eosinophilic esophagitis are outlined, drawing from clinical and translational studies in humans as well as experimental animal models.

Clinical implications and pathogenesis of esophageal remodeling in eosinophilic esophagitis

In eosinophilic esophagitis (EoE), remodeling changes are manifest histologically in the epithelium and subepithelium where lamina propria fibrosis, expansion of the muscularis propria, and increased vascularity occur. The clinical symptoms and complications of EoE are largely consequences of esophageal remodeling. Available therapies have demonstrated variable ability to reverse existing remodeling changes of the esophagus. Systemic therapies have the potential of addressing subepithelial remodeling. Esophageal dilation remains a useful, adjunctive therapeutic maneuver in symptomatic adults with esophageal stricture. As novel treatments emerge, it is essential that therapeutic end points account for the fundamental contributions of esophageal remodeling to overall disease activity.

Eosinophilic esophagitis: emerging therapies and future perspectives

Twenty years have passed since eosinophilic esophagitis was first recognized as a new and distinct entity. Current treatment modalities for eosinophilic esophagitis include the "3 Ds": drugs, allergen avoidance with diet, and esophageal dilation. Drugs entail the limitation that only corticosteroids have a proven efficacy; most other compounds evoke only a minimal effect. Diets must be maintained continuously and they interfere markedly with the quality of life, possibly even involving some risk of malnutrition. A greater understanding of the immunopathogenesis, natural history, and disease spectrum will inevitably lead to improved therapeutic outcomes for this emerging entity.

Single- and multiple-dose tolerability and pharmacokinetics of the CRTH2 antagonist setipiprant in healthy male subjects

Chemoattractant receptor-homologous molecule expressed on T helper (Th) 2 cells (CRTH2) is a G-protein-coupled receptor for prostaglandin D2 (PGD2), a key mediator in inflammatory disorders such as asthma and allergic rhinitis. In this study, we investigated the single- and multiple-dose tolerability and pharmacokinetics (PKs) of setipiprant, an orally active, potent, and selective CRTH2 antagonist. This randomized, double-blind, placebo-controlled study was performed in two parts in healthy male subjects. In study Part A, single oral doses of up to 2000 mg setipiprant or placebo were given to sequential groups of eight subjects each. Additionally, the impact of food on the PKs was investigated in one-dose group. In study Part B, two groups of subjects received 500 or 1000 mg setipiprant or placebo b.i.d. during 5.5 days. At regular intervals, tolerability variables and plasma and urine levels of setipiprant were determined. Setipiprant was well tolerated after single- and multiple-dose administration. Headache was the most frequently reported adverse event. No treatment effect on tolerability variables was observed. After single- and multiple-dose administration, setipiprant was rapidly absorbed and followed a biphasic elimination pattern with an elimination half-life between 10 and 18 h. Steady-state conditions were reached after 2-3 days and setipiprant did not accumulate. Exposure to setipiprant was lower in the presence of food. Urinary excretion of unchanged setipiprant did not exceed 7% of the administered dose. In this entry-into-human study, setipiprant showed good tolerability and a favorable PK profile, thus warranting its development in the treatment of inflammatory disorders.

Biologic targeted therapy in allergic asthma

OBJECTIVE

To review the structure, function, clinical utility, and safety of current biologic targeted therapies being used for the treatment of asthma.

DATA SOURCES

Medical literature obtained from PubMed and OVID searches from June to November 2013.

STUDY SELECTIONS

Studies were selected based on article impact, relevance, and clinical significance. Particular emphasis was placed on articles discussing therapies targeted at IgE, interleukin (IL)-4, IL-4 receptor, IL-5, IL-13, tumor necrosis factor-α, CRTh2, and toll-like receptors 7 and 9.

RESULTS

Since the approval of omalizumab in 2003, the development of biologic asthma therapies has grown at a remarkable pace. With approximately 30 drugs currently in clinical trials and dozens more in development, the future of asthma biologic therapies is promising. Despite several well-publicized setbacks, researchers remain focused on elucidating the complex pathophysiology of asthma. The hope is that asthma biologic therapies will eventually be tailored to an individual's asthma phenotype. With more than 300 million people worldwide affected by asthma and with roughly 5% to 10% of this population living with severe, uncontrolled asthma, the need for new biologic therapies is great.

CONCLUSION

The introduction of each new biologic therapy into clinical trials has been associated with great anticipation, but the outcome of these trials, in many cases, has led to disappointment. Given the lack of overwhelming positive responses, these results have emphasized that asthma is a complex clinical syndrome with multiple underlying genotypes and clinical phenotypes. It has become abundantly clear that it is very unlikely that there is one "magic bullet" to cure all patients with asthma.

Eosinophilic oesophagitis: clinical presentation and pathogenesis

Eosinophilic oesophagitis (EoE) is an inflammatory disorder of the oesophagus which has become increasingly recognised over recent years, although it remains underdiagnosed in many centres. It is characterised histologically by a significant eosinophilic infiltration of the oesophageal mucosa (>15 eosinophils per high powered field), and clinically with features of oesophageal dysfunction such a dysphagia, food impaction, and proton pump inhibitor (PPI) resistant dyspepsia. Fibrosis and oesophageal remodelling may occur and lead to oesophageal strictures. An allergic predisposition is common in the EoE population, which appears to be primarily food antigen driven in children and aeroallergen driven in adults. Evidence suggests that the pathogenesis of EoE is due to a dysregulated immunological response to an environmental allergen, resulting in a T helper type 2 (Th2) inflammatory disease and remodelling of the oesophagus in genetically susceptible individuals. Allergen elimination and anti-inflammatory therapy with corticosteroids are currently the mainstay of treatment; however, an increasing number of studies are now focused on targeting different stages in the disease pathogenesis. A greater understanding of the underlying mechanisms resulting in EoE will allow us to improve the therapeutic options available.

Historical aspects of eosinophilic esophagitis: from case reports to clinical trials

Eosinophilic esophagitis (EoE) is a clinicopathological condition characterized clinically by symptoms of esophageal dysfunction in the absence of acid reflux, with typical endoscopic findings and eosinophilia on biopsy. This article looks into the historical clinical recognition and description of EoE, in particular clinical manifestations, natural history, and epidemiology. Additionally, the evolution of endoscopic recognition and development of clinical trials are described: EoE is an isolated disease of the esophagus, although it is associated with other antigen-driven diseases such as asthma, rhinitis, and atopic dermatitis. After initial case reports which were mostly not typical of the disease state now described, the first case series were described in 1993 and 1994 in adults, and 1995 in children. Although rarely seen before 2000, the disease is now commonly recognized. Randomized clinical trials have now been performed on topical steroids, and on biological agents targeted against IL-5, IL-13, and other mediators. Therapy with dilatation may be best guided by measures of compliance and distensibility. Work is needed on biomarkers of the disease's severity and progression, and predictive indexes of complications. EoE is a relatively new disease of increasing importance. It represents an important diagnosis in patients with upper gastrointestinal symptoms and must be considered in all patients with dysphagia where the diagnosis is not certain and in all patients who have an assumed diagnosis of reflux but are not responding to standard reflux therapy.

Emerging therapeutic strategies for eosinophilic esophagitis

OPINION STATEMENT

Eosinophilic esophagitis (EoE) is recognized as an increasingly common cause of chronic and recurrent esophageal symptoms that significantly impact quality of life and may occasionally result in severe complications in both pediatric and adult patients. The disease is triggered and maintained by exposure to food antigens in most patients, with an additional role proposed for airborne allergens. Different diet-based approaches focused on restricting potentially offending foods have proven to be effective long-term therapies for EoE. Dietary therapy is thus an attractive, yet challenging treatment option that should be considered for all pediatric and adult EoE patients. However, limitations related to food restriction, patient willingness to undergo repeated endoscopies and biopsies, and the variable results of allergy testing imply that dietary management is for the most part currently restricted to highly motivated healthcare providers treating highly motivated patients reluctant to utilize drug-based therapy on a chronic basis. Pharmacological therapies for EoE mainly comprise swallowed topical steroids, especially fluticasone propionate and budesonide, which were originally developed to treat bronchial asthma and are now extensively used "off label" in EoE patients. In fact, topical steroids currently constitute the prevailing therapeutic option and will probably continue to do so in the near future; indeed, several randomized clinical trials are currently underway to test these drugs for approval as the first pharmacological agents for EoE patients. Immunomodulators and several anti-allergic agents must be further assessed as therapeutic alternatives for refractory cases or patients with complications. Endoscopic dilation represents the third pillar in the therapeutic management of EoE patients, since they frequently present reductions in the esophageal caliber as a result of collagen deposition and a progressive fibrous remodeling process promoted by chronic eosinophilic infiltration. Dilation provides at least temporary symptom relief with similar complication rates to esophageal strictures from a different origin. However, although repeated endoscopic dilation has sometimes been used as the sole therapy for EoE, it best constitutes an adjuvant therapy along with dietary or pharmacological-based interventions, especially since dilation has no effect on the underlying esophageal inflammation. Current therapeutic management of EoE varies widely, with physician experience being a major explanatory factor. New evidence from ongoing research on EoE should thus seek to define a common treatment algorithm to optimize EoE patient management.

Th17 cells and tissue remodeling in atopic and contact dermatitis

BACKGROUND

Eczematous skin lesions of atopic dermatitis (AD) as well as allergic and irritant contact dermatitis (ACD, ICD) are characterized by the same typical clinical signs, although due to different causes. In both AD and ACD, the presence of T helper 17 cells which play an important role in host defense, has been reported. Furthermore, IL-17 is involved in tissue repair and remodeling. This study aimed to investigate IL-17 expression in acute eczematous skin lesions and correlate it with markers of remodeling in AD, ACD, and ICD.

METHODS

Skin specimens were taken from positive patch test reactions to aeroallergens, contact allergens, and irritants at days 2, 3, and 4. Inflammatory cells as well as the expression of cytokines and extracellular matrix proteins were evaluated by immunofluorescence staining and confocal microscopy.

RESULTS

Allergic contact dermatitis and ICD were characterized by IFN-γ expression, whereas in AD lesions, IL-13 expression and high numbers of eosinophils were the prominent phenotype. Expression of IL-17, but also IL-21 and IL-22, was observed in all eczema subtypes. The number of IL-22+ T cells correlated with the number of eosinophils. Markers of remodeling such as MMP-9, procollagen-3, and tenascin C were observed in all acute eczematous lesions, while a correlation of IL-17+ T cell numbers with tenascin C-expressing cells and MMP-9+ eosinophils was apparent.

CONCLUSION

The expression of IL-17 and related cytokines, such as IL-22, was demonstrated in acute eczematous lesions independent of their pathogenesis. Our results suggest a potential role for IL-17 in remodeling of the skin.

Mechanisms and potential therapeutic targets in allergic inflammation: recent insights

Deeper insight into pathogenetic pathways and into the biological effects of immunomodulatory agents will help to optimize or adopt therapeutic strategies for atopic disorders. In this article, we highlight selected findings of potential therapeutic relevance that emerged from recent mechanistic studies with focus on molecular and cellular aspects of allergic inflammation. Furthermore, the often complex mechanisms of action of pleiotropic immunomodulatory agents, such as glucocorticoids, vitamin D, or intravenous immunoglobulin (IVIG), are discussed, as their dissection might reveal targets for novel therapeutics or lead to a more rational use of these compounds. Besides reporting novel evidence, this article points to areas of current debate or uncertainty and aims at stimulating scientific discussion and experimental work.

Update on the status of DP2 receptor antagonists; from proof of concept through clinical failures to promising new drugs

INTRODUCTION

The identification of PGD2 as the cognate ligand for the DP2 (formerly CRTH2) receptor and the apparent role of that receptor in allergic disease has led to considerable interest in the development of DP2 receptor antagonists for the treatment of asthma. Around 20 DP2 receptor antagonists have progressed into development.

AREAS COVERED

The DP2 antagonists in clinical development and those whose development has been discontinued are discussed in detail. This article highlights the former and examines the available clinical data in respect of both groups of antagonists. It draws upon data that are available from clinical trial registries as well as data that have been presented.

EXPERT OPINION

The unpromising clinical outcomes obtained with setipiprant, vidupiprant and AZD-1981, and the reason why development of OC-459 appears stalled, are all considered. An assessment of the nine DP2 antagonists currently in clinical development highlights the apparent advantages of ADC-3680 and MK-1029. The scope for licensing opportunities in this field is also highlighted.

Lipid mediators and allergic diseases

OBJECTIVE

To review the basic science and translational relevance of lipid mediators in the pathobiology of allergic diseases.

DATA SOURCES

PubMed was searched for articles using the key terms lipid mediator, prostaglandin, prostanoid, leukotriene, thromboxane, asthma, and allergic inflammation.

STUDY SELECTIONS

Articles were selected based on their relevance to the goals of this review. Articles with a particular focus on clinical and translational aspects of basic science discoveries were emphasized.

RESULTS

Lipid mediators are bioactive molecules generated from cell membrane phospholipids. They play important roles in many disease states, particularly in inflammatory and immune responses. Lipid mediators and their receptors are potentially useful as diagnostic markers of disease and therapeutic targets.

CONCLUSIONS

Several useful therapeutic agents have been developed based on a growing understanding of the lipid mediator pathways in allergic disease, notably the cysteinyl leukotriene receptor type 1 antagonists and the 5-lipoxygenase inhibitor, zileuton. Additional receptor agonists and antagonists relevant to these pathways are in development, and it is likely that future pharmacologic treatments for allergic disease will become available as our understanding of these molecules continues to evolve.