But, there have been few studies about the glucose lowering effect of DPP-IV inhibitors (vildagliptin) in Type 2 diabetes patients on the dual combination therapy with a sulfonylurea agent and metformin.The researchers hypothesized that DPP-IV inhibitor as add-on therapy to combination of a sulfonylurea agent and metformin have favorable glucose lowering effect in type 2 diabetic patients. The researchers plan to investigate the change in HbA1C and fasting glucose of 24 weeks treatment with vildagliptin (DPP-IV inhibitor) in combination with a sulfonylurea agent and metformin in type 2 diabetic patients.