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.