An Open-label, Randomized, Active-controlled Study to Compare the Effect of 16 Weeks Treatment With Vildagliptin to Pioglitazone as add-on Therapy to Metformin in Type 2 Diabetic Patients Inadequately Controlled With Metformin Monotherapy

Type 2 diabetes mellitus (T2DM) is a chronic progressive disease characterized by hyperglycemia that result from pancreatic islet dysfunction. Presently available oral antihypoglycemic drug improves glycemic control over the short term, none has been shown to stop the progressive decline in beta cell function which contributes to the deterioration of glycemic control over time.

Pathophysiology of T2DM is known as tissue resistance for insulin and progressive beta cell failure. Which one attributes first is unclear, but non-obese T2DM patients often show normal fasting plasma glucose (FPG) but postprandial plasma glucose (PPG) level is high and reduced or lacking normal compensatory insulin secretion. In Korea, more than 80% of T2DM are non-obese type (BMI >= 27 ) and it was observed that basal insulin level and compensatory insulin secretion reaction were reduced in normal healthy population. Based on that, metformin is an established first line treatment for type 2 diabetes, acting primarily to enhance hepatic and peripheral insulin sensitivity. However, it has become increasingly apparent that many patients require a combination of agents to attain optimal glycemic control.

Better understanding of incretin effect on the pathophysiology of T2DM has recently led to development of new oral hypoglycemic agents. Vildagliptin is a potent and highly selective dipeptidyl peptidase (DPP)-IV inhibitor that improves islet function by increasing pancreatic alpha and beta cell responsiveness to glucose. Studies in patients with T2DM have shown that vildagliptin significantly reduced HbA1c and FPG level from baseline and did not induce weight gain and the incidence of hypoglycemia was low. In addition, studies in rodents support an effort of vildagliptin on beta cell remodeling.

The thiazolidinediones are effective in reducing HbA1C in obese T2DM patients and it is known that only thiazolidinedione can delay the beta cell failure . But recently, thiazolidinediones were found to be associated with a decrease in bone mineral density and to raise the risk of myocardial infarct and cardiovascular related mortality. Thus, there is a need for new classes of blood glucose lowering drug which has the potential to delay or prevent the progression of T2DM.