Aggravated Airway Inflammation: Research on Biological Treatment (Mepolizumab)

Primary objective: to investigate the efficacy of Mepolizumab 100 milligram (mg) every month compared to placebo in reducing validated Sinonasal Outcome Test -22 score and on reducing endoscopic Nasal Polyp Score. The participants have a triad of chronic rhinosinusitis with nasal polyps (CRSwNP), asthma and non-steroidal anti-inflammatory drug exacerbated respiratory disease (NERD). The investigators will evaluate whether mepolizumab reduces the need for increased drug dosage (topical corticosteroid or bronchodilator dosage) and improves lung and nasal function more effectively than placebo. This first visit ensures the inclusion and exclusion criteria of the subject. If necessary, NERD will be verified by an ASA challenge test at a second additional visit. Participants have also 6 visits, on four of which subcutaneous injection of the study product is administered. During visits, a clinical examination, airway function tests, and nasal, blood, urine, and stool samples are also taken to elucidate predictive biomarkers of severely symptomatic NERD patients.