 This study is the first administration of GSK2890457 in humans. The study will be conducted in 3 parts: - Part A conducted at a single investigative site will determine the safety and tolerability of GSK2890457 alone in healthy subjects during six weeks of dosing, as well as evaluating the potential for a pharmacokinetic interaction with metformin. Part A consists of Screening, Treatment 6 weeks and Follow-up periods. - Part B conducted at multiple sites will determine safety, tolerability, and pharmacodynamics PD in subjects with Type 2 diabetes T2D when co-dosed for six weeks with liraglutide Victoza. Part B consists of Screening, Run-in 1 week, Stabilization 12 weeks, Treatment 6 weeks and Follow-up periods. - Part C conducted at multiple sites will determine safety, tolerability, and PD in subjects with T2D when co-dosed for 6 weeks with metformin. Part C consists of Screening, Run-in 1 week, Stabilization 12 weeks, Treatment 6 weeks and Follow-up periods. 