The purpose of this study is to learn about how different forms of the study medicine called ritlecitinib pass the intestines of healthy male adults when taken with or without food.

This study is seeking healthy participants who have:

• Aged 18 years or older;
• male who are healthy as determined by medical assessment;
• BMI of 16-32 kg/m2, and a total body weight >45 kg (99 lb).

All participants in this study will receive a ritlecitinib oral dose in two different forms (solution without food, capsule with or without food).

The study will take up to 3 months, including the screening period and follow-up phone call. Participants will have to stay at the study clinic for at least 11 days. There will be 3 periods in total, and a washout period of at least 3 days between dosings in Period 1 and Period 2, and at least 7 days between dosings in Period 2 and Period 3 for this study. On day 1 of each period, participants will take one form of Riltecitinib without food for the first two periods and with food for the last period. Participants will have blood samples taken both before and after taking ritlecitinib. A follow-up phone call will be made at 28 to 35 days after the last study period.

Inclusion Criteria:

1. Male and female participants aged 18 years or older (or the minimum age of consent in accordance with local regulations) at screening who are overtly healthy as determined by medical evaluation including medical history, physical examination, and laboratory tests.
2. BMI of 16-32 kg/m2, and a total body weight >45 kg (99 lb).
3. Participants who are willing and able to comply with all scheduled visits, treatment plan, laboratory tests, lifestyle considerations, and other study procedures.
4. Capable of giving signed informed consent

Exclusion Criteria:

1. Evidence or history of clinically significant hematological, renal, endocrine, pulmonary, gastrointestinal, cardiovascular, hepatic, psychiatric, neurological, or allergic disease (including drug allergies, but excluding untreated, asymptomatic, seasonal allergies at the time of dosing).
2. Participants with the acute or chronic infections or infection history
3. History of febrile illness within 5 days prior to the first dose of study intervention.
4. History of any lymphoproliferative disorder such as EBV related lymphoproliferative disorder, history of lymphoma, history of leukemia, or signs or symptoms suggestive of current lymphatic or lymphoid disease.
5. Known present or a history of malignancy other than a successfully treated or excised nonmetastatic basal cell or squamous cell cancer of the skin or cervical carcinoma in situ.
6. History of active or latent Mycobacterium TBA: participant who is currently being treated for active or latent Mycobacterium TB infection or has a history of Mycobacterium TB must be excluded from the study.
7. Any medical or psychiatric condition including recent (within the past year) or active suicidal ideation/behavior or laboratory abnormality or other conditions that may increase the risk of study participation or, in the investigator's judgment, make the participant inappropriate for the study.
8. Recent history of abnormal bowel movements, such as diarrhea, loose stools, or constipation, within 1 week prior to first dose.

Pfizer will provide access to individual de-identified participant data and related study documents (e.g. protocol, Statistical Analysis Plan (SAP), Clinical Study Report (CSR)) upon request from qualified researchers, and subject to certain criteria, conditions, and exceptions. Further details on Pfizer's data sharing criteria and process for requesting access can be found at: https://www.pfizer.com/science/clinical\_trials/trial\_data\_and\_results/data\_requests.