Anti-IL-5 monoclonal antibodies, such as mepolizumab and reslizumab, have been approved for second-line treatment of SEA in the clinics by decreasing the level of eosinophils in the blood/sputum through neutralization of IL-5, and inhibition of eosinophil differentiation and activation to eventually reduce the exacerbation frequency in asthma patients18–20. This evidence concerns the gene IL5 and asthma.