• Pasquale Comberiati, Katherine McCormack, Jonathan Malka-Rais, and Joseph D Spahn.
• Department of Clinical and Experimental Medicine, Section of Pediatrics, University of Pisa, Pisa, Italy; Department of Clinical Immunology and Allergology, I.M. Sechenov First Moscow State Medical University, Moscow, Russia; Allergy and Immunology Department, Children's Hospital Colorado, Aurora, Colo.
• J Allergy Clin Immunol Pract. 2019 Nov 1; 7 (8): 2689-2696.e2.

BackgroundMepolizumab is an anti-IL-5 antibody approved for the treatment of severe eosinophilic asthma. However, the prevalence of patients with severe asthma eligible for mepolizumab remains unknown, especially among children.ObjectiveTo determine, in a population of patients with severe asthma from a tertiary referral center, the proportion of patients with an eosinophilic phenotype who would be eligible for mepolizumab, when stratified for the age of onset of asthma, and the prevalence of phenotypic features that favor mepolizumab therapy.MethodsAn extensive database of 245 adults and children referred for severe asthma was used. The prevalence of severe asthma was estimated by using the European Respiratory Society/American Thoracic Society criteria. Patients with an eosinophilic uncontrolled phenotype qualified for mepolizumab.ResultsIn our cohort, 216 (88%) had severe asthma. Based on blood eosinophils of either greater than or equal to 150 cells/μL or greater than or equal to 300 cells/μL, 61%/41% had an eosinophilic phenotype, while 49%/34% were eligible for mepolizumab therapy. A greater percentage of adults (60%/47% of adults with asthma onset in adulthood [AoA] and 48%/26% adults with childhood-onset asthma [<18 years, CoA]) were eligible compared with children (33%/24%), for eosinophil counts of ≥150 and ≥300 cells/μL, respectively; P < .05. Compared with adults, children had a similar number of exacerbations while having better lung function (P < .05). Among adults, those with AoA were older, were more likely to have nasal polyps (28% vs 5%; P < .05), and had higher blood eosinophil counts (272 vs 150 cells/μL; P < .05) compared with those with CoA, with no difference in lung function noted between the 2 groups. Subjects showing greater than or equal to 500 eosinophils/μL, a strong indicator for mepolizumab therapy, had more nasal polyps, higher inhaled steroid dose, lower lung function, and AoA predominance than did those with less than 500 eosinophils/μL (P < .05).ConclusionsA smaller percentage of children with severe asthma were eligible for mepolizumab compared with their adult peers. Severe AoA has distinct phenotypic features that favor treatment with mepolizumab, including greater eosinophilia and nasal polyposis, in contrast to CoA, which appears to have fewer features of type 2 mucosal inflammation.Copyright © 2019 American Academy of Allergy, Asthma & Immunology. Published by Elsevier Inc. All rights reserved.

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