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Hanania NA, Fortis S, Haselkorn T, Gupta S, Mumneh N, Yoo B, Holweg CTJ, Chipps BE. Omalizumab in Asthma with Fixed Airway Obstruction: Post Hoc Analysis of EXTRA. The journal of allergy and clinical immunology. In practice. 2022 Jan 1; 10(1):222-228.
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 ß-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) after bronchodilator administration, respectively. FAO presence (+)/absence (-) were defined as baseline postbronchodilator FEV/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, 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 compared with placebo in the FAO-, high BDR subgroup (FEV 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.