Double Blind, Placebo-controlled Trial to Establish Safety and Efficacy of Ritlecitinib in Celiac Disease Patients in Remission

Inclusion Criteria:

1. Male and/or female subjects (including Women of Childbearing Potential (WOCBP)) ≥18years to ≤75 years of age at the time of informed consent

2. Have a body mass index ≥17 to <40 (and a body weight >45 kg at the Screening Visit).

3. Agree to make every effort to avoid pregnancy (see lifestyle outline below) from thetime of signing the informed consent throughout the duration of the trial, if thesubject is a woman of childbearing potential and sexually active with anon-sterilized male partner.

4. Have well controlled biopsy-proven CeD, compliant with a GFD for ≥6 months precedingScreening, with resolution of CeD symptoms, normalization of CeD serology (definedas </= 2 times the upper limit of normal), and (as determined at time of screeningendoscopy) negative histology (Marsh 0, 1 or 2).

5. Be HLA-DQ2.5 and/or HLA-DQ8 positive, as assessed at screening. If subjects havealready been genotyped, then results from previous testing may be used in lieu ofgenotyping at screening.

6. Must obtain negative SARS-CoV-2 test result (molecular diagnostic such as RT-PCR orRT-qPCR at the discretion of the investigator) at the screening visit and bothtimepoints prior to endoscopy (day 1 &15).

7. Evidence of a personally signed and dated informed consent document indicating thatthe subject has been informed of all pertinent aspects of the study.

8. Willing and able to comply with scheduled visits, treatment plan, laboratory tests,and other study procedures

9. Agree to avoid strenuous exercise during the study, especially within one week priorto the scheduled study visits and maintain adequate hydration (recommended)

10. Avoid consumption of grapefruit juice exceeding 8 ounces (~240 ml) total in a daywhile in the study (recommended)

11. Agree to the following contraception criteria:

• Subjects who are, in the opinion of the investigator, sexually active and atrisk for pregnancy with their partner(s) must agree to use 2 methods ofeffective contraception (at least 1 highly effective method) throughout thestudy and for at least 28 days after the last dose of investigational product.The investigator or his or her designee, in consultation with the subject, willconfirm that the subject has selected 2 appropriate methods of contraceptionfor the individual subject and his/her partner(s) from the list of permittedcontraception methods (see below) and will confirm that the subject has beeninstructed in their consistent and correct use. At time points indicated in theSchedule of Activities, the investigator or designee will inform the subject ofthe need to use 2 methods of effective contraception (at least 1 highlyeffective method) consistently and correctly and document the conversation, andthe subject's affirmation, in the subject's chart. In addition, theinvestigator or designee will instruct the subject to call immediately if 1 orboth selected contraception methods are discontinued or if pregnancy is knownor suspected in the subject or partner.

• Highly effective methods of contraception are those that, alone or incombination, result in a failure rate of less than 1% per year when usedconsistently and correctly (i.e., perfect use) and include the following:

• Implantable progestogen-only hormone contraception associated with inhibitionof ovulation.

• Intrauterine device (IUD).

• Intrauterine hormone-releasing system (IUS).

• Bilateral tubal occlusion or tubal ligation.

• Vasectomized partner: Vasectomized partner is a highly effective contraceptivemethod provided that the partner is the sole sexual partner of the WOCBP andthe absence of sperm has been confirmed. If not, an additional highly effectivemethod of contraception should be used. The spermatogenesis cycle isapproximately 90 days

• Combined (estrogen- and progestogen-containing) hormonal contraceptionassociated with inhibition of ovulation: oral; intravaginal; transdermal

• Progestogen-only hormone contraception associated with inhibition of ovulation:oral; injectable.

• Sexual abstinence: Sexual abstinence is considered a highly effective methodonly if defined as refraining from heterosexual intercourse during the entireperiod of risk associated with the study intervention. The reliability ofsexual abstinence needs to be evaluated in relation to the duration of thestudy and the preferred and usual lifestyle of the participant.

• Male condom or female condom: All sexually active male subjects must agree toprevent potential transfer to and exposure of partner(s) to drug throughejaculate by using a condom consistently and correctly, beginning with thefirst dose of investigational product and continuing for at least 28 days afterthe last dose of investigational product. Male subjects must refrain fromdonating sperm during the study and for 90 days after the last dose ofinvestigational product.

Exclusion Criteria:

1. Have a history of gluten triggered acute symptoms (≤24 hours after gluten exposure),and/or severe symptoms (abdominal pain interfering with daily activities, diarrheawith >5 stools/day), and/or prolonged symptoms (duration >7 days).

2. A history of any abdominal or pelvic surgery <3 months before trial enrollment;prior surgery abdominal or pelvic surgery (e.g., cholecystectomy, appendectomy, andhysterectomy) are permitted if performed >3 months before trial enrollment.

3. Subjects considered in imminent need for surgery or with elective surgery scheduledto occur during the study

4. Have a positive or borderline positive IgA anti-tissue transglutaminase serology atScreening (defined as >/= 2 times the upper limit of normal).

5. Have Marsh 3a-c determined by pathology at Screening Endoscopy

6. A diagnosis of any other inflammatory gastrointestinal disorder

7. Ongoing immunosuppression or receive any treatment within 3 months the starting ofthe trial that might alter T cell repertoire or phenotype.

8. Has a confirmed history of a SARS-CoV-2 infection within the previous 2 months ofthe screening visit.

9. Any history of either untreated or inadequately treated latent or active TBinfection by Interferon Gamma Release Assay during screening or within 12 weeksprior to randomization, current treatment for active or latent TB infection orevidence of currently active TB by chest x-ray, residing with or frequent closecontact with individual(s) with active TB.

10. Positive screening for HIV, Hepatitis B, Hepatitis C.