Introduction: In patients with severe asthma, causes of variation in response to anti-IL-5 therapies are not fully understood.  

Aim: This study evaluates the response to anti-IL-5 biologics and its effects on lung function in patients with severe asthma. 

Methods: 146 confirmed severe asthmatics were classified into no response, positive response and super-responders to therapy using previous criteria (Rupani & Hew, 2021, JACI,9). A positive response was deemed a 75% reduction in exacerbations from baseline stable over 12-months, and super-responders: a complete cessation of exacerbations and oral corticosteroids. Responders and non-responders were compared using Mann-U-Whitney or independent t-tests, with statistical significance accepted at an ?-level of p<0.05.   

Results: 128 (87.7%), 17 (11.6%) and 1 (0.7%) of the cohort were taking Mepolizumab, Benralizumab and Reslizumab, respectively. At 12 months, 58 were non-responders (39.7%), 52 responders (35.6%) and 36 super-responders (24.7%). Responders to anti-IL-5 therapies had significantly older age of onset (30.0 vs 10.5  years, p<0.001) and lower levels of forced expired volume in one second (FEV₁) at baseline (56.1 vs 73.0% predicted, p<0.001). At 12-month follow-up, responders showed greater mean improvements in FEV₁ (?+160 mL vs -40 mL, p=0.001,n=80) and asthma control questionnaire-7 score (?-0.8 vs -0.1, p=0.04) versus non-responders. No significant differences were identified in blood eosinophils and fraction of exhaled nitric oxide during follow-up.

Conclusions: In this study, 60.3% of severe asthmatics were responders to anti-IL-5 therapies. Responders showed greater improvements in FEV₁ and symptom scores at 12-month follow-up.