Study to compare PK of a new 120mg tablet with two 60mg tablets. This is required because we plan to have only single tablets administered in the later phase clinical trials but we have not had a 120mg strength before. As this is a new previously untested strength we need to ensure that the PK is similar to that achieved using 2x60mg before we start a large manufacturing campaign and before we administer to a large number of patients. The study is planned to consist of a single part, with two dosing periods, periods 1 and 2 consisting of 18 subjects. There will be 20 days washout between each dose. Initially 4 subjects will be given a single oral dose of 120 mg SB-773812 and 2 will be given placebo. If 120mg SB-773812 is well tolerated in the first four volunteers, the remaining 12 subjects will be dosed. If the 120mg single oral dose in the first 4 subjects is poorly tolerated, the study will be stopped. Subjects will return to the centre for follow-up 14 to 21 days after the final dose.It is expected that the total duration of the study should be approximately 11 weeks.