Efficacy and safety of sitagliptin and metformin as initial combination therapy and as monotherapy over 2 years in patients with type 2 diabetes

Aim: To assess the 104‐week efficacy and safety of sitagliptin and metformin as initial combination therapy and as monotherapy in patients with type 2 diabetes and inadequate glycaemic control (HbA_1c 7.5–11%) on diet and exercise. Methods: This study was a 50‐week, double‐blind extension of a 54‐week, randomized, double‐blind, factorial study of the initial combination of sitagliptin and metformin, metformin monotherapy and sitagliptin monotherapy (104 weeks total duration). Patients assigned to active therapy in the 54‐week base study remained on those treatments in the extension study: sitagliptin 50 mg b.i.d. + metformin 1000 mg b.i.d. (higher dose combination), sitagliptin 50 mg b.i.d. + metformin 500 mg b.i.d. (lower dose combination), metformin 1000 mg b.i.d. (higher dose), metformin 500 mg b.i.d. (lower dose) and sitagliptin 100 mg q.d. Patients randomized to receive the sequence of placebo/metformin were switched, in a blinded manner, from placebo to metformin monotherapy uptitrated to 1000 mg b.i.d. beginning at week 24 and remained on higher dose metformin through the extension. Results: Amongst patients who entered the extension study without having initiated glycaemic rescue therapy, least‐squares mean changes in HbA_1c from baseline at week 104 were ?1.7% (higher dose combination), ?1.4% (lower dose combination), ?1.3% (higher dose), ?1.1% (lower dose) and ?1.2% (sitagliptin). The proportions of patients with an HbA_1c <7% at week 104 were 60% (higher dose combination), 45% (lower dose combination), 45% (higher dose), 28% (lower dose) and 32% (sitagliptin). Fasting and postmeal measures of glycaemic control and β‐cell function improved in all groups, with glycaemic responses generally maintained over the 104‐week treatment period. The incidence of hypoglycaemia was low across all groups. The incidences of gastrointestinal adverse experiences were generally lower in the sitagliptin group and similar between the metformin monotherapy and combination groups. Conclusions: Initial combination therapy with sitagliptin and metformin and monotherapy with either drug alone provided substantial and sustained glycaemic improvements and were well tolerated over 104 weeks in patients with type 2 diabetes.