Background: Biotherapies targeting IL-5 allow a tangible improvement of asthma but all patients do not respond the same way to these treatments. Even if high blood eosinophil counts (BEC) appear associated with a reduction in exacerbations, we lack biomarkers for the prediction of remission after these very expensive treatments.
Goal: The purpose of this study is to find biomarkers of remission after therapy targeting IL-5 in the sputum of severe eosinophilic asthmatics.
Methods: This observational study included 52 severe asthmatics initiated with an anti-IL-5. Remission was defined after one year as : no oral corticosteroids, no exacerbation, asthma control questionnaire < 1.5 and/or asthma control test > 19, a forced expiration volume in 1s (FEV1) ? 80% predicted and/or improvement ? 10%, and a BEC < 300 cells/ml. Sputum eosinophil peroxidase (EPX), Immunoglobulin E (IgE), IL-3, IL-4, IL-5, IL-13, IL-25, IL-33, granulocyte-macrophage colony-stimulating factor (GM-CSF), thymic stromal lymphopoietin (TSLP) and eotaxin-1 levels were measured before anti IL-5 treatment.
Results: Among the 52 patients, 11 were classified in remission. They were characterized by higher sputum eosinophil, macrophage and lymphocyte counts while the sputum neutrophil percentage was lower than in the non-remission group. In addition, the sputum eotaxin-1, TSLP, IL-5, EPX and IgE protein levels were higher at baseline in the remission group compared to the other. 
Conclusion: Sputum type-2 (T2) markers appeared to be potentially predictive of remission after anti IL-5 in a cohort of severe eosinophilic asthmatic patients. These results need validation on a larger cohort.