Efficacy and safety of sitagliptin added to ongoing metformin therapy in patients with type 2 diabetes

Objective: The purpose of this study was to evaluate the efficacy and safety of sitagliptin as an add-on to metformin therapy in patients with moderately severe (hemoglobin A(1c) >= 8.0% and <= 11.0%) type 2 diabetes mellitus (T2DM). Research design and methods: This was a multinational, randomized, placebo-controlled, parallel-group, double-blind study conducted in 190 patients with T2DM. After >= 6 weeks of stable metformin monotherapy (>= 1500 mg/day), patients were randomized to either the addition of sitagliptin 100 mg once daily or placebo to ongoing metformin for 30 weeks. Main outcome measures: The primary efficacy endpoint was reduction in hemoglobin A(1c) (HbA(1c)) measured after 18 weeks of sitagliptin treatment. Key secondary endpoints included reduction in fasting plasma glucose (FPG) and 2-hour (2-h) postprandial plasma glucose (PPG) at 18 weeks, and HbA(1c) at 30 weeks. The proportion of patients meeting the goal of HbA(1c) <7.0% was also analyzed. Results: Sitagliptin significantly reduced HbA(1c), FPG, and 2-h PPG, compared with placebo (all p < 0.001). The net improvement in HbA(1c) was -1.0% at both 18 and 30 weeks, and a significantly greater proportion of patients treated with sitagliptin achieved HbA(1c) < 7.0% by the end of the study (22.1% vs. 3.3%, p < 0.001). Sitagliptin was well-tolerated. Compared with placebo, sitagliptin had a neutral effect on body weight and did not significantly increase the risk of hypoglycemia or gastrointestinal adverse events. Conclusions: Addition of sitagliptin 100 mg once daily to ongoing metformin therapy was well-tolerated and resulted in significant glycemic improvement in patients with moderately severe T2DM who were treated for 30 weeks.