Small airways function: evaluation in a population of adult patients with severe asthma and potential use as a response biomarker for anti-IL5 therapy

Background: Asthma is a disease characterized by heterogeneity in clinical presentation and pathophysiological mechanisms. A novel element of new studies is the role of the involvement of the small airways function (SAF) in asthma severity and in response to therapy. Anti-interleukin 5 monoclonal antibody mepolizumab therapy in patients with severe eosinophilic asthma significantly reduces exacerbations frequency, with modest improvement in symptom control and FEV1, but the effects of this drug on spirometric parameters of small airway functionality are currently poorly characterized. Aim: to measure SAF using the spirometric parameter FEF25-75 in adult patients with severe eosinophilic asthma treated with mepolizumab. To describe the variations of this parameter in response to treatment and correlate it with other clinical and spirometric features. Population & Methods: 42 adult severe asthmatic patients in treatment with the biological drug mepolizumab for a period of 12 months. Evaluation of clinical parameters [Asthma Control Test, number of exacerbations and oral corticosteroid dose] and spirometry were carried out at time 0 before the start of therapy and after 6 and 12 months. Results & Conclusions: An overall improvement in functional parameters was observed at the six-month follow-up which remained stable at 12 months of treatment. FEF25-75 value improved, at 6 months (p=0.0003), and at 12 months of treatment (p=0.003). Anti IL-5 treatment with mepolizumab produces significant effects on lung function in patients with severe asthma, in particular biologic therapy determined a relevant improvement in SAF.