The clinical benefit of mepolizumab replacing omalizumab in uncontrolled severe eosinophilic asthma

BACKGROUND: Mepolizumab and omalizumab are treatments for distinct but overlapping severe asthma phenotypes. OBJECTIVE: To assess if patients eligible for both biologics but not optimally controlled with omalizumab experience improved asthma control when switched directly to mepolizumab. METHODS: OSMO was a multicenter, open‐label, single‐arm, 32‐week trial in patients with ≥2 asthma exacerbations in the year prior to enrollment, despite receiving high‐dose inhaled corticosteroids and other controller(s), plus omalizumab (≥4 months). At baseline, patients with blood eosinophil counts ≥150 cells/µL (or ≥300 cells/µL in the prior year) and an Asthma Control Questionnaire (ACQ)‐5 score ≥1.5 discontinued omalizumab and immediately commenced mepolizumab 100 mg subcutaneously every 4 weeks. Endpoints included change from baseline in ACQ‐5 score (primary), St George's Respiratory Questionnaire (SGRQ) score and the proportions of ACQ‐5 and SGRQ responders, all at Week 32, and the annualized exacerbation rate over the study period. RESULTS: At Week 32 (intent‐to‐treat population [n = 145]), the least squares (LS) mean changes (standard error [SE]) in ACQ‐5 and SGRQ total scores were −1.45 (0.107) and −19.0 (1.64) points; with 77% and 79% of patients achieving the minimum clinically important differences (ACQ‐5: ≥0.5 points; SGRQ: ≥4 points), respectively. The annualized rate of clinically significant exacerbations was 1.18 events/year, a 64% reduction from 3.26 events/year during the previous year. Safety and immunogenicity profiles were consistent with previous trials. CONCLUSION: After directly switching from omalizumab to mepolizumab, patients with uncontrolled severe eosinophilic asthma experienced clinically significant improvements in asthma control, health status, and exacerbation rate, with no tolerability issues reported.