Mepolizumab (Nucala) is a humanised IgG1 monoclonal antibody that acts as an IL-5 antagonist. It has been shown to be highly effective in treating severe asthma. It is hypothesised that it will be effective for patients with recalcitrant CRSwNP. This is the first paper to assess the impact of mepolizumab on patients with allergic fungal rhinosinusitis (AFRS). It is interesting that the treatment caused a significant reduction in eosinophil levels and an improvement in endoscopic evaluation scores, particularly for those with severe disease at the outset, but less so if the disease load at the outset was minimal. There was little difference between the two groups in the need for a prednisolone rescue pack. Most importantly, patient symptoms scores also improved with treatment, particularly within the disease-specific sub-scores. Whilst currently this medication is not widely available, I think the increasing body of evidence that patients with recalcitrant disease will benefit from monoclonal antibody treatments is supported by this paper.