To assess the efficacy and safety of vildagliptin add-on therapy to reduce HbA1c in patients with T2DM inadequately controlled by insulin, with or without concurrent metformin therapy.

Inclusion Criteria:

• Confirmed diagnosis of T2DM
• On a stable dose of insulin as defined by the protocol
• On a stable does of metformin (if applicable) as defined by the protocol
• Age 18 to 80 years
• HbA1c of 7.5 to 11.0%
• Body Mass Index (BMI) 22 to 40 kg/m2

Exclusion Criteria:

• Type 1 diabetes
• Short-acting or rapid-acting insulin
• Pregnancy or lactation
• Evidence of serious diabetic complications
• Evidence of serious cardiovascular complications
• Laboratory value abnormalities as defined by the protocol
• Other protocol-defined inclusion/exclusion criteria may apply