Double-blind, placebo controlled study of the efficacy, safety and tolerability of 6-weeks treatment of ALV003 in patients with well-controlled celiac disease. Approximately 110 biopsy proven celiac disease patients will be randomized to treatment with ALV003 or placebo in a 1:1 ratio. Patients will be required to have a pre-dose and a post-treatment intestinal biopsy, and also will be required to ingest a foodstuff that contains a specified amount of gluten during the active phase of the study along with the study treatment. Patients will return to the clinic weekly for the first two weeks, then every two weeks thereafter for safety visits. Patients will return to the clinic 28 days after completion of treatment for final safety and follow-up. Safety will be closely monitored throughout the study including laboratory parameters and clinical assessment of adverse events.