Anti-inflammatory effects of oral prednisolone at stable state in people treated with mepolizumab: a proteomic and bulk transcriptomics analysis

Mepolizumab is an anti-interleukin-5 monoclonal antibody treatment for severe eosinophilic asthma (SEA) that reduces asthma exacerbations. Residual airway inflammation on mepolizumab may lead to persistent exacerbations. Oral corticosteroids have broad anti-inflammatory effects and remain the main treatment for these residual exacerbations. Our study aimed to explore the nature and corticosteroid-responsiveness of airway inflammation after mepolizumab treatment to find potentially treatable inflammatory mechanisms. The MAPLE trial was a multi-centre, randomized, double-blind, placebo-controlled, crossover study of 2 weeks of high-dose oral prednisolone treatment at stable state in patients treated with mepolizumab for SEA. We analysed sputum and plasma samples from the MAPLE trial using high-throughput Olink proteomics. We also analysed plasma microRNA, sputum proteins using ELISA, and nasal mucosal bulk RNA sequencing. In patients receiving mepolizumab, prednisolone significantly downregulated sputum proteins related to type-2 inflammation and chemotaxis including IL-4, IL-5, IL-13, CCL24, CCL26, EDN, CCL17, CCL22, OX40 receptor, FCER2, and the ST2 receptor. Prednisolone also downregulated cell adhesion molecules, prostaglandin synthases, mast cell tryptases, MMP1, MMP12, and neuroimmune mediators. Tissue repair and neutrophilic pathways were upregulated. Type-2 proteins were also downregulated in plasma, combined with IL-12, IFN-γ, and IP-10. IL-10 and amphiregulin were upregulated. In the nasal transcriptome, prednisolone suppressed genes involved in leucocyte chemotaxis, mast cell tryptase, 15-lipoxygenase and MMP12. By contrast, mepolizumab differentially regulated only Galectin-10 in plasma and no sputum proteins, and in nasal tissue affected genes related to cilia, keratinisation, extracellular matrix formation, and IL-4/13 signalling. At stable state, prednisolone has broad anti-inflammatory effects on top of mepolizumab.