Asthma with eosinophilic inflammation in the airways and/or blood eosinophilia is associated with clinical severity including the risk of exacerbations and relevant comorbidities (e.g. nasal polyposis). Interleukin-5 (IL-5) is a cytokine essential for eosinophil trafficking and survival. Clinical trials of blocking IL-5 with anti-IL-5 antibodies (mepolizumab and reslizumab) in patients with uncontrolled eosinophilic asthma resulted in an improvement in exacerbation rate and oral corticosteroid use. In some studies with mepolizumab and reslizumab there was a beneficial effect on lung function (FEV1). In addition, many patients described a profound impact on asthma symptoms and quality of life in personal reports which is not uniformly reflected in clinical trials.