Gluten ingestion in patients with celiac disease can lead to gastrointestinal symptoms and small intestinal mucosal injury. This gluten challenge phase 2 trial was double blind and placebo controlled, and it assessed the efficacy and safety of a 1200-mg dose of IMGX003 in patients with celiac disease exposed to 2 g of gluten per day for 6 weeks. The change in the ratio of villus height to crypt depth was the primary endpoint. Secondary endpoints included density of intraepithelial lymphocytes and symptom severity. These endpoints were evaluated by analysis of covariance. Additional endpoints included serology and gluten-immunogenic peptides in urine. Fifty patients were randomized, and 43 patients completed the study (IMGX003, n= 21; placebo, n= 22). The mean change in the ratio of villus height to crypt depth (primary endpoint) for IMGX003 vs placebo was -0.04 vs -0.35 (P= .057). The mean change in the density of intraepithelial lymphocytes (secondary endpoint) for IMGX003 vs placebo was 9.8 vs 24.8 cells/mm epithelium (P= .018). The mean change (worsening) in symptom severity in relative units (secondary endpoint) for IMGX003 vs placebo was 0.22 vs 1.63 (abdominal pain, P= .231), 0.96 vs 3.29 (bloating, P= .204), and 0.02 vs 3.20 (tiredness, P= .113). The 3× 2-week trend line significance values for these symptoms, respectively, were P= .014, .030, and .002. IMGX003 reduced gluten-induced intestinal mucosal damageand symptom severity. (ClinicalTrials.gov, Number: NCT03585478).