Nasal IL-5 levels determine the response to anti–IL-5 treatment in patients with nasal polyps

Chronic rhinosinusitis with nasal polyps is characterized by an eosinophilic inflammation and high IL-5 levels.Antagonizing the effect of IL-5 is a potential new treatment strategy in patients with nasal polyps.In a double-blind, placebo-controlled, randomized, 2-center safety and pharmacokinetic study, 24 subjects with bilateral nasal polyps were randomized to receive a single intravenous infusion of reslizumab, a humanized anti-human IL-5 mAb, at 3 mg/kg or 1 mg/kg or placebo. We evaluated the safety and pharmacokinetics of reslizumab, and biologic activity was assessed by means of endoscopic evaluation of polyp size, symptoms, peripheral eosinophil counts, peripheral and local IL-5 levels, eotaxin levels, and eosinophil cationic protein levels.We demonstrated that a single injection of reslizumab up to 3 mg/kg is safe and well tolerated. Blood eosinophil numbers and concentrations of eosinophil cationic protein were reduced up to 8 weeks after treatment in serum and nasal secretions. Individual nasal polyp scores improved only in half of the treated patients for 4 weeks. Responders had increased IL-5 concentrations in nasal secretions at baseline compared with nonresponders, and logistic regression analysis revealed that increased nasal IL-5 levels (>40 pg/mL) predict the response to anti-IL-5 treatment.A single injection of anti-IL-5 reduces the size of nasal polyps for 4 weeks in half of the patients, and nasal IL-5 levels predict the response to anti-IL-5 treatment.Intravenous administration of a humanized anti-human IL-5 mAb is safe and reduces the size of nasal polyps in half of the patients.