Background: There is limited understanding of the impact of anti-IL5 treatment on nasal polyp tissue biology in chronic rhinosinusitis with nasal polyps (CRSwNP). The aim of this study was to determine the effect of the nasal polyp tissue cellular proteome and transcriptome in response to six months of anti-IL5 treatment with mepolizumab in CRSwNP utilising high-plex spatial profiling. Methods: GeoMx™ Digital Spatial Profiling (DSP) of 80 proteins and 1,833 mRNA targets in the polyp stroma and of the whole transcriptome (18,815 mRNA targets) in polyp epithelia was undertaken on formalin-fixed paraffin embedded slides of sinonasal biopsies collected before and after 16 and 24 weeks of treatment with mepolizumab. Results: Anti-IL5 therapy with mepolizumab in patients with eosinophilic CRSwNP had significant tissue biological impact. Treatment-related changes in proteins within immune checkpoint inhibition, neutrophil degranulation and the innate immune system were key biological mechanisms identified in a protein interaction network. Transcriptionally, there were significant reductions in gene sets associated with the reactome terms innate and adaptive immune system, neutrophil degranulation and TGFβ receptor signalling in epithelial to mesenchymal transition within polyp stroma, as well as enhancing antioxidant pathways. In polyp epithelia, increases in gene sets associated with the reactome-terms cilium assembly and keratinisation and a reduction in the regulation of KIT signalling were observed with treatment. Conclusions: Spatial profiling technology demonstrates that the effects of anti-IL5 treatment within nasal polyp tissue extend well beyond simple eosinophil reduction to broader regulation of innate and adaptive immune cells and in improving the epithelial barrier biology.

Background: Eosinophilic chronic rhinosinusitis is an often treatment-resistant inflammatory disease mediated by type-2 cytokines, including interleukin (IL)-5. Mepolizumab, a monoclonal antibody drug targeting IL-5, has demonstrated efficacy and safety in inflammatory airway disease, but there is negligible evidence on direct tissue response. The study aim was to determine the local effect of mepolizumab on inflammatory biomarkers in sinonasal tissue of eosinophilic chronic rhinosinusitis patients. Methods: Adult patients with eosinophilic chronic rhinosinusitis received 100mg mepolizumab subcutaneously at four-weekly intervals for 24 weeks in this prospective phase 2 clinical trial. Tissue eosinophil counts, eosinophil degranulation (assessed as submucosal eosinophil peroxidase deposition by immunohistochemistry) and cytokine levels (measured in homogenates by immunoassay) were evaluated in ethmoid sinus tissue biopsies collected at baseline and at weeks 4, 8, 16 and 24. Results: Twenty patients (47.7±11.7 years, 50% female) were included. Sinonasal tissue eosinophil counts decreased after 24 weeks of treatment with mepolizumab (101.64±93.80 vs 41.74±53.76 cells per 0.1mm 2; p=0.035), eosinophil degranulation remained unchanged (5.79±2.08 vs 6.07±1.20, p=0.662), and type-2 cytokine levels increased in sinonasal tissue for IL-5 (10.84±18.65 vs 63.98±50.66, p=0.001), IL-4 (4.48±3.77 vs 9.38±7.56, p=0.004), IL-13 (4.02±2.57 vs 6.46±3.99, p=0.024) and GM-CSF (1.51±1.74 vs 4.50±2.97, p=0.001). Conclusions: Mepolizumab reduced eosinophils in sinonasal tissue, demonstrating that antagonism of IL-5 suppresses eosinophil trafficking. With reduced tissue eosinophils, a local type-2 inflammatory feedback loop may occur. The study exposes mechanistic factors which may explain incomplete treatment response.