Mepolizumab for eosinophilic chronic obstructive pulmonary disease

Mepolizumab is a monoclonal antibody that interferes with interleukin-5 signalling to reduce blood eosinophil level and is licenced for use in severe refractory eosinophilic asthma. The clinical relevance of eosinophilic inflammation in chronic obstructive pulmonary disease (COPD) is being increasingly recognised. Pavord et al (NEJM 2017;377:1613–1629) describe the METREX and METREO trials, which evaluated the effect of mepolizumab in frequent exacerbator phenotype patients with COPD. METREX and METREO were international, phase 3, double-blinded, randomised clinical trials. Patients with COPD on triple inhaled therapy who had had at least two moderate or one severe exacerbation in the preceding year were recruited and stratified by blood eosinophil level. Non-eosinophilic patients were excluded from METREO. Eight hundred and thirty-seven (METREX) and 675 (METREO) patients were randomised to receive 4 weekly mepolizumab (METREX: 100 mg, METREO: 100 mg or 300 mg assigned 1:1) or placebo as add on to their COPD therapy for 52 weeks. The primary end point of both studies was annual rate of moderate or severe exacerbations. Secondary end points included time to first exacerbation, frequency of hospital attendance and changes to patient-reported outcomes. The data were analysed in a modified intention-to-treat population. In METREX, exacerbation frequency and time to first exacerbation …