This 4 arm study will evaluate the pharmacokinetics, pharmacodynamics, safety and tolerability of multiple ascending doses of R1511 compared to placebo in patients with type 2 diabetes mellitus. The starting dose of R1511 will be 100mg po bid for 5 1/2 days; this dose will be escalated in subsequent groups of patients to a potential maximum of 1200mg po bid for 5 1/2 days after a satisfactory assessment of blinded safety, tolerability, pharmacokinetic and pharmacodynamic data of the previous dose. The anticipated time on study treatment is <3 months, and the target sample size is <100 individuals.