 After a one week washout, Cohort 3 subjects will receive a single oral dose of 15mg GW856553. Access to both IV and oral PK in the same individuals will permit calculation of absolute bioavailability for the oral dose. Subjects will be resident in the research unit from the morning prior to dosing until after the last PK blood sample is collected at 24 hours after the dose of study drug excluding any washout period. 