This open-label, randomized, 5-period crossover study will be completed in a single cohort of subjects, with an interim analysis after completion of Treatment Period 4. During Treatment Periods 1 to 4, subjects will be randomized to receive GSK1325756 50 mg IR in the fed state, GSK1325756 50 mg IR in the fasted state, GSK1325756 Bioenhanced Formulation 1 in the fasted state, and GSK1325756 Bioenhanced Formulation 2 in the fasted state. Progression to Treatment Period 5 and the choice of bioenhanced formulation for dosing in this treatment period will be dependent on the findings of an interim analysis of the pharmacokinetic profile and relative bioavailability of each formulation following completion of Treatment Periods 1 to 4. In Treatment Period 5, subjects will receive the selected GSK1325756 bioenhanced formulation in the fed state.