This is a Phase 1, randomized, open label, 4-period, 6-sequence, partial cross-over, single-dose study to evaluate the PK of age-appropriate tofacitinib MR formulations (release rates: MR-Slow, MR-Moderate, and MR-Fast) compared to tofacitinib IR solution under fasting conditions. The effect of food on the PK of MR-Slow and MR-Fast will also be assessed.

Inclusion Criteria:

• Healthy male and or female subjects of non-childbearing potential between the ages of 18 and 55 years, inclusive.

• Female subjects of nonchildbearing potential must meet at least 1 of the following criteria:

  1. Achieved postmenopausal status, defined as: cessation of regular menses for at least 12 consecutive months with no alternative pathological or physiological cause; and have a serum follicle stimulating hormone (FSH) level confirming the postmenopausal state;
  2. Have undergone a documented hysterectomy and/or bilateral oophorectomy;
  3. Have medically confirmed ovarian failure. All other female subjects (including female subjects with tubal ligations) are considered to be of childbearing potential.

• Body Mass Index (BMI) of 17.5 to 30.5 kg per m2; and a total body weight above 50 kg (110 lbs) for males and above 45 kg (99 lbs) for females.

• No evidence of active or latent or inadequately treated infection with Mycobacterium tuberculosis (TB)

Exclusion Criteria:

• Evidence or history of clinically significant hematological, renal, endocrine, pulmonary, gastrointestinal, cardiovascular, hepatic, psychiatric, neurologic, or allergic disease (including drug allergies, but excluding untreated, asymptomatic, seasonal allergies at the time of dosing).
• Clinically significant infections within the past 3 months, evidence of any infection within the past 7 days, history of disseminated herpes simplex infection or recurrent (>1 episode) herpes zoster or disseminated herpes zoster.
• Absolute lymphocyte count at Screening or Baseline less than the lower limit of the reference range for the local laboratory
• Evidence or history of cyclic neutropenia.
• Personal or family history of hereditary immunodeficiency
• Vaccination with live or attenuated vaccines within the 6 weeks of dosing, or is to be vaccinated with these vaccines at any time during study treatment or within 6 weeks following discontinuation of dosing.
• Any condition possibly affecting drug absorption (eg, gastrectomy, colon resection, etc.).
• History of, or current positive results for any of the following serological tests: human immunodeficiency virus (HIV), hepatitis B, or hepatitis C;
• Malignancy or a history of malignancy, with the exception of adequately treated or excised non-metastatic basal cell or squamous cell cancer of the skin or cervical carcinoma in situ.
• Positive urine drug test.
• History of regular alcohol consumption
• Use of tobacco- or nicotine-containing products in excess of the equivalent of 5 cigarettes per day.
• Treatment with an investigational drug within 30 days (or as determined by the local requirement ) or 5 half-lives preceding the first dose of investigational product (whichever is longer).
• Nursing females or females of childbearing potential. Male subjects who are unwilling or unable to use a condom plus a highly effective method of contraception as outlined in this protocol for the duration of the study and for at least 28 days after the last dose of investigational product.
• Use of prescription or nonprescription drugs and dietary supplements within 7 days or 5 half-lives (whichever is longer) prior to the first dose of investigational product.

Herbal supplements and hormone replacement therapy must be discontinued at least 28 days prior to the first dose of investigational product.

• Use of CYP3A4 inhibitors or inducers within 14 days or 5 half-lives (whichever is longer) prior to dosing.
• Consumption of grapefruit or grapefruit-related citrus fruits (eg, Seville oranges, pomelos) or juices within 7 days prior to dosing.
• Blood donation (excluding plasma donations) of approximately 1 pint (500 mL) or more within 60 days prior to dosing.
• History of sensitivity to heparin or heparin-induced thrombocytopenia.

Information relating to our policy on data sharing and the process for requesting data can be found at the following link: http://www.pfizer.com/research/clinical\_trials/trial\_data\_and\_results/data\_requests