Study of DONQ52 in Active Celiac Disease

Inclusion Criteria:

• Body mass index (BMI) of 18 to 40 (kg/m2) at screening.

• Willingness to ingest a gluten-free product and Simulated Inadvertent GlutenExposure (SIGE) products as per the study protocol.

• History of medically diagnosed, and adequately documented (i.e., included in theparticipant's medical records), CeD

• Attempting a GFD for at least 12 months prior to the screening visit.

• The participants should be instructed not to alter dietary habits including a GFDduring the study period.

• Valid results from central testing of blood documenting a positive result for theHLA DQ2.5 genotype (HLA-DQA105 and HLA-DQB102) (homozygous or heterozygous).

• Experienced at least 2 gluten-related symptom events (i.e., 2 differentgluten-related symptoms which are diarrhea, abdominal pain, bloating, nausea,tiredness or 1 gluten-related symptom occurred twice) within a month before thescreening.

• Willingness to undergo 2 on-study upper gastrointestinal endoscopies with duodenalbiopsies.

• Presence of ongoing duodenal mucosal damage defined as Vh:Cd of 2.5 or less

Exclusion Criteria:

• Participants with documented history (i.e., included in the participant's medicalrecords) of medically diagnosed Refractory Celiac Disease (RCD) or suspected RCD bythe investigator.

• History of IgE-mediated reactions to wheat, barley, rye, or other ingredients ingluten-free and SIGE products used in this study (i.e., methylcellulose, andgelatin).

• History of cancer, including hematological malignancy and solid tumors, within 5years prior to the screening visit, or history of T cell lymphoma or B cell lymphomaever.

• History of hypersensitivity reactions including anaphylaxis to a biological medicalproduct or any of the excipients.

• Participants who carry the HLA-DQ8 (HLA-DQA103 and DQB10302) genotype (homozygousor heterozygous).

• Any other chronic, active gastrointestinal disease (e.g., inflammatory boweldisease, microscopic colitis, eosinophilic esophagitis, peptic ulcer,gastroesophageal reflux disease, functional dyspepsia, or irritable bowel syndrome)that might in the investigator's opinion, interfere with the assessment of GIsymptoms or small intestinal histology.

• Helicobacter pylori tests that indicate current infection.

• Positive either human immunodeficiency virus (HIV) antigen or antibody test atscreening.

• Positive hepatitis B surface antigen (HBsAg) test or total hepatitis B core (HBc)antibody test at screening.

• Positive hepatitis C virus (HCV) antibody test at screening, except in participantswho have negative results for HCV ribonucleic acid (RNA) test at screening.

• Positive for QuantiFERON-TB Gold test at screening that indicates activetuberculosis (TB) at screening.