Anti–IL-5 for hypereosinophilia

Abstract

Hypereosinophilic syndromes are a group of disorders characterized by severely elevated levels of one type of white blood cell, the eosinophils. In these diseases, eosinophils grow in an uncontrolled manner and can attack numerous parts of the body, such as the heart, lung, gastrointestinal tract, and skin. Over the last decade, physicians have noted an increasing number of cases of these medical problems, especially in patients with gastrointestinal symptoms. In this issue of the Journal, Garrett et al (p 115) tested anti–IL-5 (mepolizumab), which blocks the eosinophil growth factor IL-5. This drug was originally developed for the treatment of asthma and is under clinical trials for this condition. IL-5 is a cytokine critically involved in regulating several aspects of eosinophils, including their production, activation, and tissue recruitment. Accordingly, the research team, led by Dr Marc E. Rothenberg, aimed to assess the safety and efficacy of the new drug in patients with several forms of hypereosinophilic syndromes. Four patients, previously dependent on or refractory to toxic medication used to partially treat these disorders, were treated with 3 intravenous doses of anti–IL-5 administered at 4-week intervals. The researchers found that anti–IL-5 was well tolerated in all patients and lowered eosinophil counts despite ongoing systemic steroid therapy. Amazingly, the decline in eosinophil counts was sustained for at least 12 weeks after the last dose of anti–IL-5. Most important, anti–IL-5 improved clinical and quality-of-life measurements. For example, one patient who had not been able to eat any solid foods for many years (because his disease involved the narrowing of his esophagus) stopped his regular vomiting and was finally able to begin swallowing solid foods. Other patients reported improved respiratory symptoms and began assuming more normal lifestyles. Although this is a preliminary study, the results suggest that anti–IL-5 might be very useful for a variety of problems associated with hypereosinophilic syndromes.