Mepo for Eosinophilic Esophagitis (EoE) Study

This is a multi-center, randomized, double blind, parallel-arm, placebo controlled trial of mepolizumab. After the first 3 month blinded phase, there will be a second 3 month blinded phase where all patients receive active medication, but the dose will be lower in the subjects initially randomized to the placebo arm. In the first arm, subjects will receive mepolizumab 300 mg SQ monthly for 3 months. In the second arm, subjects will receive a placebo SQ injection monthly for 3 months. Both groups will have the injection administered under direct observation in a Clinical \& Translational Research Center (CTRC) or other clinic to ensure proper administration and compliance. Each visit will also provide an opportunity for symptom questionnaires to be completed and for blood samples to be drawn. After 3 months (the time point where the primary outcome is assessed), all subjects initially randomized to active treatment will continue with mepolizumab dosing 300 mg SQ monthly, and will remain blinded. All subjects initially randomized to placebo will receive mepolizumab 100mg SQ monthly, and will remain blinded. Of note, no dietary changes, changes in baseline Proton Pump Inhibitor (PPI) medication dose, changes in inhaled or intranasal steroid doses, or administration or oral, topical/swallowed, or systemic steroids will be allowed during the study period. Subjects will undergo endoscopy after the first blinded phase (at 3 months) and after the second blinded phase (after 6 months).