Omalizumab in Asthma with Fixed Airway Obstruction: Post Hoc Analysis of EXTRA

Abstract

Background Although asthma is typically characterized by bronchodilator responsiveness (BDR), fixed airflow obstruction (FAO) occurs in ∼50% of patients with severe asthma. Objective Do FAO/BDR associate with efficacy of omalizumab, a monoclonal antibody that targets IgE? Methods In EXTRA, patients aged 12-75 years with inadequately controlled severe allergic asthma despite high-dose inhaled corticosteroids plus long-acting β 2 -agonists were randomized to omalizumab (n = 427) or placebo (n = 423) for 48 weeks of treatment. In this post hoc analysis, high/low BDR were defined as ≥12%/<12% increases in baseline forced expiratory volume in 1 second (FEV 1 ) after bronchodilator administration, respectively. FAO presence (+)/absence (−) were defined as baseline postbronchodilator FEV 1 /forced vital capacity <70%/≥70%, respectively. Poisson regression/analysis of covariance models were used to estimate exacerbation relative rate reductions (RRRs)/least-squares mean changes in FEV 1 , respectively. Results In patients with high BDR, omalizumab reduced exacerbations more than placebo over the 48-week treatment period regardless of FAO status (RRR [95% confidence interval (CI)]: FAO+, 59.8% [17.7-80.4%]; FAO−, 44.3% [16.6-62.8%]). Omalizumab improved FEV 1 compared with placebo in the FAO−, high BDR subgroup (FEV 1 change from baseline [95% CI] for omalizumab vs placebo, 0.065 L [–0.071 to 0.201 L] to 0.236 L [0.112-0.359 L]) across 48 weeks. This was not observed in patients with low BDR, irrespective of FAO. Conclusion Omalizumab was more efficacious than placebo at reducing exacerbations in patients with high, but not low, BDR, regardless of the presence of FAO. Lung function improvement primarily occurred in FAO−, high BDR patients, suggesting that asthma with low BDR may represent a difficult-to-treat phenotype.

Topics & Concepts