This study will evaluate the potential for a drug-drug interaction of PF-04937319 with ketoconazole, a potent inhibitor of the drug metabolizing enzyme CYP3A.

Inclusion Criteria:

• Healthy male and/or female subjects between the ages of 18 and 55 years, inclusive. Healthy is defined as no clinically relevant abnormalities identified by a detailed medical history, full physical examination, including blood pressure and pulse rate measurement, 12-lead ECG or clinical laboratory tests.
• Body Mass Index (BMI) of 17.5 to 29.9 kg/m2; and a total body weight >=50 kg (110 lbs).
• Subjects of childbearing potential must agree to use a highly effective method of contraception throughout the study and for at least 28-days after the last dose of treatment.

Exclusion Criteria:

• 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 study medication.
• Pregnant or nursing females; females of childbearing potential who are unwilling or unable to use an acceptable method of non-hormonal contraception
• Consumption of grapefruit-containing products within 7 days prior to the first dose of study medication and while in the study protocol from at least 14 days prior to the first dose of study medication and for at least 28 days after the last dose of study medication