Efficacy and safety of vildagliptin, sitagliptin, and linagliptin as add-on therapy in Chinese patients with T2DM inadequately controlled with dual combination of insulin and traditional oral hypoglycemic agent

Objective: We aimed to evaluate the efficacy and safety of the three dipeptidyl peptidase 4 (DPP-4) inhibitors (vildagliptin, sitagliptin, and linagliptin) as add-on therapy in Chinese patients with type 2 diabetes mellitus (T2DM) inadequately controlled on dual combination of insulin and metformin or acarbose. Methods: A total of 535 T2DM patients who failed to achieve glycemic control with insulin and a traditional oral hypoglycemic agent were randomized to receive vildagliptin, sitagliptin, or linagliptin. Body mass index, glycosylated hemoglobin (HbA1c), fasting and postprandial plasma glucose (FPG and PPG), insulin dose, and adverse events were evaluated during the study. Results: The baseline HbA1c was 9.59 +/- 1.84 % (vildagliptin group), 9.22 +/- 1.60 % (sitagliptin group), and 9.58 +/- 1.80 % (linagliptin group). At week 12 it was 8.16 +/- 1.29 % (vildagliptin), 8.56 +/- 1.96 % (linagliptin), and 8.26 +/- 1.10 % (sitagliptin). The changes in HbA1c from baseline were -1.33 +/- 0.11 % (vildagliptin), -0.84 +/- 0.08 % (sitagliptin) and -0.81 +/- 0.08 % (linagliptin), the vildagliptin group had the greatest reduction in HbA1c (P < 0.05). The proportions of patients that reached target HbA1c were 66.27 % (vildagliptin), 52.73 % (sitagliptin), and 55.49 % (linagliptin), the vildagliptin group had the highest one (P < 0.05). The baseline FPG and PPG values in the three groups were at the same level. At week 12, mean FPG levels in the vildagliptin (7.31 +/- 1.50 mmol/L) and linagliptin (6.90 +/- 1.55 mmol/L) groups were significantly lower than in the sitagliptin group (8.02 +/- 4.48 mmol/L; P < 0.05); the linagliptin group had the lowest mean PPG followed by the vildagliptin group which was also significant lower (P = 0.000) than the sitagliptin group. Additionally, the required insulin dosage in the vildagliptin group was the lowest among the groups at weeks 6 and 12. Only mild AEs were reported during the study. Conclusion: The three DPP-4 inhibitors appear to be effective and safe as add-on therapy for T2DM patients on dual combination of insulin and a traditional OHA. Vildagliptin was more effective in decreasing insulin requirement and achieving glycemic control when compared to the other two.