Serum C-peptide to plasma glucose ratio may be associated with efficacy of vildagliptin in Japanese patients with type 2 diabetes mellitus

Aim: This retrospective study was undertaken to clarify the characteristics of patients in whom vildagliptin exerts its HbA1c-lowering effect fully. The safety of vildagliptin was also examined. Methods: Vildagliptin was administered as initial, additive, or exchange medication to 139 type 2 diabetic patients. Patients were excluded if they had a change in another oral hypoglycemic agent within 24 weeks after starting vildagliptin. The primary efficacy endpoint was the percentage of patients who attained HbA1c level <7 % at week 24. Results: Vildagliptin significantly increased the percentage of patients who attained HbA1c level <7 %. It was significantly higher in patients with lower baseline HbA1c, higher C-peptide immunoreactivity (CPR) index [plasma CPR (ng/ml)/glucose (mg/dl) × 100], and in patients whose CPR index increased after the administration of vildagliptin. Categorical analyses by age, gender, and body mass index showed no significant differences among categories. There was no significant difference in HbA1c-lowering effect in the categories of oral hypoglycemic agents used concomitantly with vildagliptin, nor of hypoglycemic agents switched to vildagliptin. Logistic regression analyses indicated that the only factor contributing to the glucose-lowering effect of vildagliptin was baseline HbA1c. There were no changes in clinical parameters thought to be adverse events. Conclusions: Administration of vildagliptin provided a significant and clinically relevant HbA1c-lowering effect irrespective of age, gender, BMI, and concomitantly or previously used hypoglycemic agents. Furthermore, not only high baseline CPR index, but also the increase in CPR index may be associated with the efficacy of this medication.