RT Journal Article SR Electronic T1 Late Breaking Abstract - Add-on mepolizumab for chronic rhinosinusitis with nasal polyps: SYNAPSE study JF European Respiratory Journal JO Eur Respir J FD European Respiratory Society SP 4616 DO 10.1183/13993003.congress-2020.4616 VO 56 IS suppl 64 A1 Claire Hopkins A1 Claus Bachert A1 Wytske Fokkens A1 Martin Desrosiers A1 Martin Wagenmann A1 Stella Lee A1 Ana Sousa A1 Steven Smith A1 Neil Martin A1 Bhabita Mayer A1 Robert Chan A1 Joseph Han YR 2020 UL http://erj.ersjournals.com/content/56/suppl_64/4616.abstract AB Background: Chronic rhinosinusitis with nasal polyps (CRSwNP) is an inflammatory disease with recalcitrant symptoms. NP tissue eosinophils lead to recurrence, which often require repeat surgeries.1Aims: To assess the efficacy and safety of 4-weekly add-on mepolizumab 100 mg SC in adults with CRSwNP.Methods: SYNAPSE (NCT03085797), a randomised, double-blind, placebo-controlled, multicentre, 52-week study, included patients with severe bilateral NP, treated with intranasal corticosteroids; with a prior NP surgery and eligible for repeat surgery. Co-primary endpoints: changes in total endoscopic NP score (Week 52) and nasal obstruction VAS score (Weeks 49–52). Secondary endpoints: time to first NP surgery (key); overall VAS symptom score, Sinonasal Outcome Test-22 score; systemic corticosteroid (SCS) use, composite and loss of smell VAS scores. Safety was assessed.Results: Total endoscopic NP score and nasal obstruction VAS score significantly improved (p<0.001) with mepolizumab (n=206) vs placebo (n=201). Median change in endoscopic NP score showed a 1-point improvement with mepolizumab (adjusted: -0.73 [95% CI:-1.11,-0.34]); median change in nasal obstruction VAS score showed a >3-point improvement (adjusted: -3.14 [-4.09,-2.18]). All secondary endpoints significant. Mepolizumab reduced NP surgery by 57% (hazard ratio 0.43 [0.25,0.76];p=0.003), improved SNOT-22, VAS (overall, composite, loss of smell) and SCS use. No new safety issues with mepolizumab. Nasopharyngitis was the most common AE (23–25%).Conclusions: Mepolizumab improved NP size and sinonasal symptoms and reduced NP surgery and SCS use in adults with severe CRSwNP and may be a treatment option in this population.Funding: GSK [GSK ID:205687]FootnotesCite this article as: European Respiratory Journal 2020; 56: Suppl. 64, 4616.This abstract was presented at the 2020 ERS International Congress, in session “Respiratory viruses in the "pre COVID-19" era”.This is an ERS International Congress abstract. No full-text version is available. Further material to accompany this abstract may be available at www.ers-education.org (ERS member access only).