This is a decentralized study to primarily explore a novel objective digital biomarker (i.e., Gluten Dependency Index) for celiac disease-related responses triggered by gluten exposure using a wearable biosensor. This study also explores a novel objective blood biomarker specific to celiac disease activity and evaluates participant symptoms, lifestyle and an objective comprehensive measurement (e.g., activity, stress and sleep) in celiac disease participants.

Approximately 170 well-controlled celiac disease participants (Cohort A) and 40 celiac disease participants with persistent symptoms (Cohort B) will be monitored for 13 and 8 weeks in the observation period, respectively, in a home-based setting using the wearable biosensor along with a mobile platform including some electronic questionnaires.

The wearable biosensor continuously records biosensor data. These data will be used to develop a new algorithm for Gluten Dependency Index and calculate the Gluten Dependency Index, Activity Value, Stress Value, or Sleep Time. Participants will report celiac disease-related symptoms, diet (including any accidental gluten exposures), exercise, menstruation questionnaires in CDSD and mobile platform questionnaire (MPFQ), which is originally designed by the Sponsor.

All participants both in Cohort A and B are required to maintain gluten-free diet throughout the study. Only participant who are enrolled in Cohort A will be required gluten challenge.

Inclusion Criteria:

[Cohort A and B]

• History of medically diagnosed celiac disease based on biopsies and positive celiac serology.
• Be on a GFD for at least 12 months
• Willing and able to adhere to use and management of the wearable device
• Willingness to comply with home-based approach and visits by a HN professional [Cohort A only]
• Experienced at most mild symptoms of celiac disease
• Willingness to consume food containing up to 6 g of gluten protein per challenge day and up to 18 g of gluten protein in total during the study [Cohort B only]
• Experienced at least 2 different gluten-related symptoms (e.g., diarrhea, abdominal pain, bloating, nausea, tiredness) or 1 gluten-related symptom occurred twice within the month before screening, and at screening were required to have a qualifying score as moderate or severe on at least one symptom on the CDSD in the 14 days recording period.
• Positive for any of the 3 serology tests, tissue - transglutaminase-2-IgA [tTG2-IgA] (≥4 U/mL), deamidated gliadin peptide-IgA [DGP-IgA] (≥20 U/mL), or deamidated gliadin peptide-IgG [DGP-IgG] (≥20U/mL)

Exclusion Criteria:

[Cohort A and B] Refractory celiac disease [Cohort A] Positive for any of the 3 serology tests

• Tissue transglutaminase-2 [tTG2-IgA] (≥10 U/mL; normal range: 0-3.99 U/mL) prior to the observation period, but weak positive (4-10 U/mL) can be enrolled in this study.
• Deamidated gliadin peptide-IgA [DGP-IgA], and deamidated gliadin peptide-IgG [DGP-IgG] prior to the observation period, but weak positive (20-30 U/mL) can be enrolled.

History of IgE-mediated reactions to wheat, barley, rye, or other ingredients in the gluten products used in the study

Cohort A: Well-controlled celiac disease participants who should be asymptomatic or mildly symptomatic Cohort B: Celiac disease participants with persistent symptoms who are known to be symptomatic and show positivity to serum auto-antibodies even though participants have been adhering to gluten-free diet

Qualified researchers may request access to individual patient level data through the clinical study data request platform. For further details on Chugai's Data Sharing Policy and how to request access to related clinical study documents, see here (www.chugai-pharm.co.jp/english/profile/rd/ctds\_request.html).