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The development of mepolizumab, an anti-IL-5 monoclonal antibody for the treatment of severe eosinophilic asthma, is an example of a clinical development program that evolved over time based on sound, basic scientific principles. Initial clinical data on the effects of mepolizumab on lung function in a general asthmatic population were disappointing. However, it became clear that mepolizumab may be more effective against other clinical endpoints, particularly asthma exacerbations, in patients with more severe disease. Furthermore, a developing understanding of asthma disease pathobiology led to the identification of an appropriate target population and predictive biomarker for mepolizumab treatment: patients with severe eosinophilic asthma and blood eosinophil count. Mepolizumab use provides clinically meaningful benefits in this target population, fulfilling an unmet need. This Clinical Commentary Review describes the clinical development of mepolizumab and details of how this program informed the development of other biologic therapies in patients with severe asthma. This account highlights how a personalized approach toward treatment of patients with severe eosinophilic asthma, supported by a large body of scientific evidence, ultimately led to new and effective treatments and improved patient outcomes.

Original publication




Journal article


The journal of allergy and clinical immunology. In practice

Publication Date



Nuffield Department of Medicine and Oxford Respiratory NIHR BRC, University of Oxford, Oxford, United Kingdom.