Efficacy and Safety of Vildagliptin Compared to Placebo on the Incretin Effect in Patients With Type 2 Diabetes Treated With Metformin

Inclusion Criteria: * Patients with type 2 diabetes on metformin for at least 3 months and have been on a stable dose of at least 1500 mg daily for a minimum of 4 weeks * Agreement to maintain the same dose of metformin throughout the study * Body mass index (BMI) in the range of 22-35 kg/m2 * HbA1c in the range of 7.0 to 9.0% * FPG \<200 mg/dl (11.1 mmol/L) * Agreement to maintain prior diet and exercise habits during the full course of the study * Ability to comply with all study requirements and signed informed consent to participate in the study Exclusion Criteria: * A history of type 1 diabetes * A history of acute metabolic diabetic complications * Evidence of significant diabetic complications * Insulin treatment for longer than 10 days within the past 6 months * Treatment with any oral anti-diabetic other than metformin within 3 months prior to visit 1 Other protocol-defined inclusion/exclusion criteria may apply