Airway hyperresponsiveness (AHR) and eosinophilia are hallmarks of persistent asthma.

We investigated whether eosinophil depletion with benralizumab might attenuate indirect mannitol AHR in severe uncontrolled asthma using a pragmatic open-label design.

After a 4-week run-in period with provision of usual inhaled corticosteroids and/or long-acting β-agonist (baseline), adults with mannitol-responsive uncontrolled severe eosinophilic asthma received 3 doses of open-label benralizumab 30 mg every 4 weeks, followed by 16 weeks’ washout after the last dose. The primary outcome was doubling difference (DD) in provocative dose of mannitol required to decrease FEV₁ by 10% (PD₁₀) at the end point after 12 weeks, powered at 90% with 18 patients required to detect 1 DD. Secondary outcomes included measures assessed by the asthma control questionnaire and mini-asthma quality of life questionnaire.

Twenty-one patients completed 12 weeks’ benralizumab therapy at the end point at week 12. Mean (SEM) age was 53 (4) years, and FEV₁ 80.2% (4.1%) inhaled corticosteroid dose was 1895 (59) μg, with 12 receiving long-acting muscarinic antagonist and 13 leukotriene receptor antagonists. Improvement in AHR was significant by 8 weeks, with a mean 2.1 DD (95% confidence interval 1.0, 3.3; P < .01) change in PD₁₀ at week 12, while mean changes in asthma control questionnaire and mini-asthma quality of life questionnaire were significant by week 2 and sustained over 12 weeks, both exceeding the minimal important difference. Peripheral blood eosinophils were depleted by 2 weeks (439 to 6 cells/μL). No significant improvement occurred in lung function after 12 weeks. Domiciliary peak flow and symptoms also improved with benralizumab.

Eosinophil depletion results in clinically meaningful attenuated AHR in severe uncontrolled asthma patients.