Stopping versus continuing long-term mepolizumab treatment in severe eosinophilic asthma (COMET study)

BACKGROUND: The long-term efficacy and safety of mepolizumab for treatment of severe eosinophilic asthma are well established. Here, we examine the clinical impact of stopping mepolizumab after long-term use. METHODS: COMET (NCT02555371) was a randomised, double-blind, placebo-controlled, parallel-group, multicentre study. Patients who had completed COLUMBA (NCT01691859) or COSMEX (NCT02135692) and received continuous mepolizumab treatment for ≥3 years were randomised 1:1 to stop (switch to placebo) or continue subcutaneous mepolizumab 100 mg every 4 weeks for 52 weeks. Primary end-point: time to first clinically significant exacerbation; secondary end-points: time to first exacerbation requiring hospitalisation/emergency department visit, time to decrease in asthma control (≥0.5-point increase in Asthma Control Questionnaire-5 score from COMET baseline) and blood eosinophil count ratio to COMET baseline. Safety was assessed. RESULTS: Patients stopping (n=151) versus continuing (n=144) mepolizumab had significantly shorter times to first clinically significant exacerbation (hazard ratio 1.61, 95% CI 1.17–2.22; p=0.004) and decrease in asthma control (hazard ratio 1.52, 95% CI 1.13–2.02; p=0.005), and higher blood eosinophil counts at week 52 (270 versus 40 cells·µL(−1); ratio (stopping versus continuing) 6.19, 95% CI 4.89–7.83; p<0.001). Differences in efficacy outcomes between groups were observed when assessed from week 12 (16 weeks after last mepolizumab dose). Exacerbations requiring hospitalisation/emergency department visit were rare. Adverse events in patients continuing mepolizumab were consistent with previous studies. For patients who stopped mepolizumab, the safety profile was consistent with other eosinophilic asthma populations. CONCLUSION: Patients who stopped mepolizumab had an increase in exacerbations and reduced asthma control versus those who continued.