A Study to Evaluate the Pharmacokinetics, Safety and Tolerability of PF-06651600 in Subjects With Hepatic Impairment and Healthy Volunteers

Inclusion Criteria: * Willing and able to comply with all scheduled visits, treatment plan, laboratory tests, lifestyle considerations and other study procedures * Body mass index (BMI) of 17.5 to 40 kg/m2; and a total body weight \>50 kg (110 lb) Additional Inclusion Criteria for Participants with Normal Hepatic Function: * Healthy male or female participants * No known or suspected hepatic disease Additional Inclusion Criteria for Participants with Impaired Hepatic Function: * Stable hepatic impairment, defined as no clinically significant change in disease status within the last 30 days prior to the Screening visit * No other ongoing clinically significant abnormalities based on medical history, physical examination, vital signs, 12-lead ECG, and clinical laboratory tests except for the abnormal findings that are related to the participant's hepatic impairment. * Satisfy the criteria for Class A or Class B of the Child-Pugh classification (mild: Child-Pugh Scores 5-6 points, and moderate: Child Pugh Scores 7-9 points), within 28 days of investigational product administration. Exclusion Criteria: * Has active acute or chronic infection requiring treatment or history of systemic infection requiring hospitalization, incl. herpes zoster, herpes simplex, tuberculosis * Infection with hepatitis B, hepatitis C or HIV * Any condition affecting drug absorption, distribution, metabolism and excretion (eg, status post porta-caval shunt surgery, prior bariatric surgery, gastrectomy, ileal resection) * Has malignancy, lymphoproliferative disorder, surgery or other condition not allowed per protocol Additional Exclusion Criteria for Participants with Normal Hepatic Function: \- Evidence or history of clinically significant hematological, renal, endocrine, pulmonary, gastrointestinal, cardiovascular, hepatic, psychiatric, neurological, gynecologic or allergic disease Additional Exclusion Criteria for Participants with Impaired Hepatic Function: \- Has encephalopathy, severe ascites and/or pleural effusion, Child-Pugh score \>9 or medical conditions (like hepatorenal syndrome, gastrointestinal hemorrhage, etc.) excluded per protocol