Outcomes after biologic initiation among patients with severe asthma and normal lung function in the CHRONICLE study

A subset of patients with severe asthma (SA) has normal lung function, defined by a pre-bronchodilator (BD) forced expiratory volume in 1 second (FEV₁) of ≥80% of predicted normal value. The effect of biologic treatments on patients with SA and normal lung function is not well understood. This analysis assessed the effectiveness of biologics among adults with SA and normal lung function using data from CHRONICLE (NCT03373045), a real-world observational study of United States patients with SA. Among the 233 patients in this analysis, 28.8% (n=67) had normal lung function, whereas 71.2% (n=166) had reduced lung function (pre-BD FEV₁ <80% of predicted normal). In the 12 months before initiating biologic treatment, annualized exacerbation rates were 1.19 (95% confidence interval [CI]: 0.95-1.49) in patients with normal lung function and 1.42 (95% CI: 1.24-1.61) in those with reduced lung function. Exacerbation rates were reduced by 50% (p<0.0001) and by 59% (p<0.0001) among those with normal and reduced lung function, respectively. Rates of exacerbation-related emergency department (ED) visits in the 12 months before initiating biologic treatment in patients with normal lung function and reduced lung function were 0.18 (95% CI: 0.09-0.31) and 0.38 (95% CI: 0.29-0.49), respectively. The rate of exacerbation-related ED visits was reduced by 44% (p=0.03) and 63% (p<0.0001) among those with normal and reduced lung function, respectively. Biologic treatments showed similar effectiveness in reducing exacerbations and exacerbation-related ED visits in patients with SA and normal lung function compared with patients with reduced lung function.Clinical trial registration ClinicalTrials.gov identifier: NCT03373045.