Supplementary Material for: Case report: Successful treatment with tezepelumab for an adult with refractory and severe fibrostenotic eosinophilia esophagitis

Introduction: Non-response to treatment in eosinophilic esophagitis (EoE) is common, and the approach to treatment-refractory patients with EoE is challenging. With increasing knowledge of EoE pathogenesis, mechanisms can be targeted by medications that are approved for other atopic diseases with a similar pathophysiology. Case presentation: We present an adult with EoE who had longstanding symptoms prior to diagnosis, developed severe fibrostenosis with the narrow caliber phenotype requiring multiple esophageal dilations, and was previously non-responsive to proton pump inhibitors (PPIs), topical corticosteroids (tCS), and food elimination diets (FED). Because of his concomitant severe asthma, he was treated with the eosinophil-depleting biologics mepolizumab and benralizumab. These reduced eosinophil counts on esophageal biopsy, but did not improve symptoms, endoscopic features, or other histologic findings. He continued to require esophageal dilation for symptom control. His asthma control also remained suboptimal, prompting a trial of tezepelumab, an antibody against thymic stromal lymphopoietin (TSLP). In addition to controlling asthma, he improved across EoE symptom, endoscopic, and histologic metrics over a year of follow-up, including improvements in the EoE Endoscopic Reference Score, esophageal caliber, and basal zone hyperplasia, dilated intercellular spaces, and lamina propria fibrosis as measured by the EoE Histologic Scoring System. Conclusion: This patient, who did not respond to PPI, FED, tCS, mepolizumab, or benralizumab, ultimately had response to tezepelumab across multiple outcome domains of EoE. This demonstrates proof-of-concept that targeting TSLP may be a promising modality in EoE and supports further study of this mechanism for treatment of EoE.