Immunomodulatory therapy of eosinophil-associated gastrointestinal diseases

Eosinophil-associated gastrointestinal disorders (EGIDs), including eosinophilic esophagitis (EE) and eosinophilic gastroenteritis (EG), are a spectrum of increasingly recognized inflammatory diseases characterized by gastrointestinal symptoms and eosinophilic infiltration of the gastrointestinal tract. Significant morbidity is associated with the development of esophageal strictures in some patients. Immune-mediated reactions to food allergens appear to drive the inflammation in a subset of patients, especially those with solitary EE, but dietary interventions remain difficult in EE and are less effective in EG. Despite the increasing incidence of these disorders and their increased recognition by physicians, there are currently no medications that either United States or European Union regulatory agencies have specifically approved for use in EGIDs. This lack of safe and effective therapies for EGIDs is a major obstacle in the care of these patients and underscores the need for new therapeutic approaches. This review briefly discusses the currently available 'off label' drug treatments for EGIDs, most notably topical and systemic corticosteroids. Pathogenesis studies of EGIDs suggest possible therapeutic targets, and conversely, clinical trials of mechanistically-targeted therapeutics give insight into disease pathogenesis. Thus, EGID pathogenesis is discussed as an introduction to mechanistically-targeted immunotherapeutics. The two biologic categories that have been used in EGIDs, anti-IgE (omalizumab) and anti-IL-5 (SCH55700/reslizumab and mepolizumab), are discussed. Because there are similarities in the pathogenesis of EGIDs with asthma and atopic dermatitis, biologic therapeutics currently in early trials for asthma management are also briefly discussed as potential therapeutic agents for EGIDs. Given the deficiencies of current therapeutics and the rapidly advancing knowledge of the pathogenesis of these disorders, EGIDs are an ideal model for translating recent advances in understanding immunopathogenesis into mechanistically-based therapeutics. Further understanding of the early events in pathogenesis is also needed to develop preventive and disease-modifying treatments.