The Food and Drug Administration (FDA) has approved Nucala (mepolizumab) as an add-on maintenance treatment for chronic rhinosinusitis with nasal polyps (CRSwNP) in adult patients 18 years of age and older with inadequate response to nasal corticosteroids.

The approval was based on data from the randomized, double-blind, parallel group phase 3 SYNAPSE study ( Identifier: NCT03085797), which evaluated the efficacy and safety of mepolizumab, an interleukin-5 antagonist monoclonal antibody, as an add-on maintenance treatment in over 400 adults with CRSwNP.

All patients had a history of prior surgery and were in need of further surgery due to severe symptoms and increased size of their polyps. Patients were randomly assigned to receive mepolizumab 100mg subcutaneously every 4 weeks or placebo for 52 weeks, in addition to standard of care (eg, mometasone furoate nasal spray).

The co-primary endpoints were change from baseline to week 52 in total endoscopic nasal polyp score (NPS; 0-8 scale) as graded by independent blinded assessors and change from baseline in nasal obstruction visual analog scale (VAS) score (0-10 scale) during weeks 49 to 52.

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At the end of the 52 week treatment period, patients treated with mepolizumab had a statistically significant improvement in bilateral NPS at week 52 (mean difference vs placebo, -0.93 [95{d847ba2f23daf15c773bda6cb71ac33aa9166b9578a171d654c6e3c528a0b6bc} CI, -1.31, -0.55]) and nasal obstruction VAS score from weeks 49 to 52 (mean difference vs placebo, -1.86 [95{d847ba2f23daf15c773bda6cb71ac33aa9166b9578a171d654c6e3c528a0b6bc} CI, -2.53, -1.19]).

Moreover, the proportion of patients who had surgery was significantly reduced by 57{d847ba2f23daf15c773bda6cb71ac33aa9166b9578a171d654c6e3c528a0b6bc} (hazard ratio, 0.43; 95{d847ba2f23daf15c773bda6cb71ac33aa9166b9578a171d654c6e3c528a0b6bc} CI, 0.25-0.76) in the group treated with mepolizumab vs placebo. Mepolizumab treatment was also associated with statistically significant improvement in loss of smell and with reduced need for systemic corticosteroids.

As for safety, the most common adverse reactions reported in the study were oropharyngeal pain and arthralgia.

“More than 5 million people in the US suffer with chronic rhinosinusitis with nasal polyps and today’s approval provides these patients with the first anti-IL-5 treatment option and an alternative to surgery to help reduce symptoms of this disease,” said Dr Hal Barron, Chief Scientific Officer and President R&D, GlaxoSmithKline.

Nucala is already approved for the treatment of eosinophilic granulomatosis with polyangiitis (EGPA), hypereosinophilic syndrome (HES), and as an add-on maintenance treatment for severe asthma and with an eosinophilic phenotype.


  1. GSK announces FDA approval for Nucala (mepolizumab) for use in adults with chronic rhinosinusitis with nasal polyps. News release. GlaxoSmithKline plc. Accessed July 29, 2021. 
  2. Nucala [package insert]. Research Triangle Park, NC: GlaxoSmithKline. 2021.

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