OBJECTIVE: AC2993 (synthetic exendin-4; exenatide) is a peptide that enhances glucose-dependent insulin secretion, suppresses inappropriately elevated glucagon secretion, and slows gastric emptying. AC2993 also promotes beta-cell proliferation and neogenesis in vitro and in animal models. This study examines the activity and safety of subcutaneously injected AC2993 in patients with type 2 diabetes currently treated with diet and/or oral antidiabetic agents (OAAs). RESEARCH DESIGN AND METHODS: A total of 109 patients treated with diet and a sulfonylurea and/or metformin were enrolled in a blinded study. Patients were randomly assigned to one of three subcutaneously (SC) injected regimens of AC2993 (0.08 micro g/kg) or placebo for 28 days. RESULTS: All three AC2993 regimens led to significant reductions in serum fructosamine relative to placebo (P <or= 0.004). Mean reductions ranged from 39 to 46 micro mol/l. All AC2993 groups had reductions in HbA(1c) ranging from 0.7 to 1.1% (P <or= 0.006). An end-of-study HbA(1c) <7% was achieved by 15% of AC2993 patients versus 4% of placebo patients, confirming AC2993 effects on fasting and postprandial glycemia. On days 14 and 28, the beta-cell index (homeostasis model assessment) for patients treated with AC2993 was 50-100% higher than baseline, contrasting with unchanged levels for placebo. The most common adverse event was transient mild-to-moderate nausea. CONCLUSIONS: AC2993 is a promising therapeutic for patients with type 2 diabetes. In this study, it had significant effects on HbA(1c) levels in patients not currently achieving optimal glucose control with diet and/or OAAs.