BACKGROUND: Approximately 85% of nasal polyps (NPs) in white subjects are 
characterized by prominent eosinophilia. IL-5 is the key driver of eosinophilic 
differentiation and survival.
OBJECTIVE: We sought to investigate the therapeutic potential of inhibiting IL-5 
with a humanized mAb as treatment for severe nasal polyposis.
METHODS: Thirty patients with severe nasal polyposis (grade 3 or 4 or recurrent 
after surgery) refractory to corticosteroid therapy were randomized in a 
double-blind fashion to receive either 2 single intravenous injections (28 days 
apart) of 750 mg of mepolizumab (n = 20) or placebo (n = 10). Change from 
baseline in NP score was assessed monthly until 1 month after the last dose 
(week 8). Computed tomographic scans were also performed at week 8.
RESULTS: Twelve of 20 patients receiving mepolizumab had a significantly 
improved NP score and computed tomographic scan score compared with 1 of 10 
patients receiving placebo at week 8 versus baseline.
CONCLUSION: Mepolizumab achieved a statistically significant reduction in NP 
size for at least 1 month after dosing in 12 of 20 patients. IL-5 inhibition is 
a potential novel therapeutic approach in patients with severe eosinophilic 
nasal polyposis.