The goal of this study is to learn whether or not the drug PTG-100 can reduce or prevent inflammatory injury to the small intestine that occurs when people with celiac disease eat food products containing gluten.

This is a clinical research study to determine the safety and efficacy of PTG-100 in preventing gluten-induced inflammatory injury to the small intestine in patients with celiac disease. 30 patients will receive either placebo (fake drug) or PTG-100 (real drug) in capsule form twice daily for 42 days. They will also receive a gluten challenge twice daily in the form of a cookie or equivalent. An upper gastrointestinal endoscopy and exam including small bowel mucosa biopsy will be performed at the start of the treatment period and again at the end. Blood samples will be routinely taken to evaluate safety and the drug's mechanism of action throughout the study, and symptoms will be recorded using the celiac symptoms index (CSI) survey.

Inclusion Criteria:

• Diagnosis of celiac disease

Exclusion Criteria:

• Active GI disease or history of clinically significant diseases
• Diagnosis of Crohn's disease or ulcerative colitis.

Double-blind