Research Communication: Mepolizumab Improves Histologic Severity as Measured by the <scp>EoEHSS</scp> in Adolescents and Adults With Eosinophilic Oesophagitis in a Multicenter, Randomised, Double‐Blind, Placebo‐Controlled Clinical Trial

Because the effect of mepolizumab on the eosinophilic oesophagitis (EoE) Histologic Scoring System (HSS) is unknown, we performed a secondary analysis of a clinical trial (NCT03656380) of mepolizumab 300 mg subcutaneously monthly versus placebo to comprehensively analyse HSS grade and stage scores. Mepolizumab had significantly lower HSS vs. placebo for both grade (0.39 ± 0.14 vs. 0.56 ± 0.21; p < 0.001) and stage (0.37 ± 0.14 vs. 0.53 ± 0.20; p < 0.001). HSS correlated with endoscopic severity for grade (R = 0.45, p < 0.001) and stage (R = 0.47, p < 0.001), but improvement was primarily limited to the eosinophil-dependent HSS features. Eosinophil-focused treatments alone may not provide comprehensive treatment response across multiple outcome domains in EoE.