Exenatide, an incretin mimetic for adjunctive treatment of type 2 diabetes (T2DM), reduced hemoglobin A(1c) (A1C) and weight in clinical trials. The objective of this study was to evaluate the effects of > or = 3 years exenatide therapy on glycemic control, body weight, cardiometabolic markers, and safety. Patients from three placebo-controlled trials and their open-label extensions were enrolled into one open-ended, open-label clinical trial. Patients were randomized to twice daily (BID) placebo, 5 mug exenatide, or 10 mug exenatide for 30 weeks, followed by 5 mug exenatide BID for 4 weeks, then 10 mug exenatide BID for > or = 3 years of exenatide exposure. Patients continued metformin and/or sulfonylureas. 217 patients (64% male, age 58 +/- 10 years, weight 99 +/- 18 kg, BMI 34 +/- 5 kg/m(2), A1C 8.2 +/- 1.0% [mean +/- SD]) completed 3 years of exenatide exposure. Reductions in A1C from baseline to week 12 (-1.1 +/- 0.1% [mean +/- SEM]) were sustained to 3 years (-1.0 +/- 0.1%; p or = 3 years in T2DM patients resulted in sustained improvements in glycemic control, cardiovascular risk factors, and hepatic biomarkers, coupled with progressive weight reduction.