A Study in Type 2 Diabetic Subjects on Stable Metformin Therapy to Investigate the Safety, Tolerability, Pharmacokinetics and Pharmacodynamics of Co-administering Single and Multiple Oral Doses of GSK1292263

This study will investigate the safety, tolerability, pharmacokinetics and pharmacodynamics of GSK1292263 when co-administered with metformin. The study will be in 2 parts. Part A will determine the PK of GSK1292263 following single day dosing of type 2 diabetes (T2DM) subjects on metformin. Part B will investigate the effects of 14d of co-dosing of GSK1292263 BID, 50mg BID of sitagliptin or placebo to 48 T2DM subjects taking metformin.