 This is a single-center, randomized, two part, open-label, crossover study in healthy adult subjects to assess the effect of up to three formulations on the relative bioavailability of GSK2248761 100mg administered with and without food. Part A will evaluate two new formulations compared to the current formulation. Part B will evaluate one additional formulation if the bioavailability of the two formulations in Part A do not meet pre-specified criteria. Safety evaluations and serial PK samples will be collected during each treatment period. A follow-up visit will occur 7-10 days after the last dose of study drug. 