Children with severe asthma were less likely to be eligible for mepolizumab than adults with severe asthma, according to study results recently published in The Journal of Allergy and Clinical Immunology: In Practice. Mepolizumab is more likely to be indicated for severe adult-onset asthma because of distinct phenotypic features such as nasal polyposis and eosinophilia.
Researchers used a database of 245 adults and children referred for severe asthma. Of that number, 88% (n=216) had severe asthma; 59 were children (mean age, 11 years) and 157 were adults (mean age, 47 years). Criteria from the European Respiratory Society and American Thoracic Society were used to estimate the rate of severe asthma. Lung function was assessed using ≥3 methods. Mepolizumab was considered appropriate for any individuals with an eosinophilic uncontrolled phenotype.
The primary objective of the study was to examine the presence of eosinophilic phenotypes (defined as blood eosinophils ≥150 cells/μL or ≥300 cells/μL) in individuals with severe asthma and their consequent qualification for mepolizumab, stratified by the age of onset. Continuous variables were compared across groups using the Pearson’s chi-squared test and analysis of variance, while categorical measures were compared using the Fisher exact test.
An eosinophilic phenotype was identified in 61% of patients with ≥150 cells/μL and in 41% of those with ≥300 cells/μL; of these, 49% and 33% were eligible for mepolizumab, respectively. When analyzed by age at onset, 60% and 47% of adult-onset participants and 48% and 26% of those with childhood-onset asthma were eligible, respectively; of the children with severe asthma, 33% and 24% were eligible, respectively (P <.05 for all). Exacerbations and poor lung function were less likely among children than adults (P <.05). Compared with adults with childhood-onset asthma, adults with adult-onset asthma had higher blood eosinophils (272 vs 150; P <.01) and were likelier to report nasal polyps (28% vs 5%; P =.001), although the 2 groups did not differ significantly in terms of lung function. Compared with individuals with ≤500 eosinophils/μL, those with a significant indication for mepolizumab (≥500 eosinophils/μL) had worse lung function, a greater number of nasal polyps, a greater dose of inhaled steroid, and a higher rate of adult-onset asthma (P <.05 for all).
Limitations to this study included the retrospective design, the likelihood for recall bias in retrospective studies, the use of a <18-year cut-off point to define childhood-onset asthma instead of <12 years as in other studies, a lack of generalizability, and the inclusion of those previously treated with omalizumab.
The researchers concluded that “up to 60% of adults with [severe asthma] would be eligible for mepolizumab therapy with a smaller proportion of children with [severe asthma] being eligible. This discrepancy comes largely from the fact that mepolizumab is currently approved in the US only for use in children 12 years of age and older.”
Disclosures: Drs Spahn and Malka-Rais report financial associations with pharmaceutical companies.
Comberiati P, McCormack K, Malka-Rais J, Spahn JD. Proportion of severe asthma patients eligible for mepolizumab therapy by age and age of onset of asthma [published online June 13, 2019]. J Allergy Clin Immunol Pract. doi:10.1016/j.jaip.2019.05.053