Efficacy and safety of initial combination therapy with sitagliptin and metformin in patients with type 2 diabetes: a 54-week study

Objective: To assess the 54-week efficacy and safety of initial combination therapy with sitagliptin and metformin in patients with type 2 diabetes and inadequate glycemic control (HbA(1c) 7.5-11%) on diet and exercise. Methods and materials: This was multinational study conducted at 140 clinical sites in 18 countries. Following an initial 24-week, double-blind, placebo-controlled period, patients entered a double-blind continuation period for an additional 30 weeks. Following the week 24 evaluation, patients remained on their previously assigned active, oral treatments: sitagliptin 50 mg b.i.d. + metformin 1000 mg b.i.d. (S100 + M2000), sitagliptin 50 mg b.i.d. + metformin 500 mg b.i.d. (S100 + M1000), metformin 1000 mg b.i.d. (M2000), metformin 500 mg b.i.d. (M1000), and sitagliptin 100 mg q.d. (S100). Patients initially randomized to placebo were switched to M2000 (designated PBO/M2000) at week 24. This report summarizes the overall safety and tolerability data for the 54-week study and presents efficacy results for patients randomized to continuous treatments who entered the 30-week continuation period. Results: Of the 1091 randomized patients, 906 completed the 24-week placebo-controlled phase and 885 patients continued into the 30-week continuation period (S100 + M2000 n = 161, S100 + M1000 n = 160, M2000 n = 153, M1000 n = 147, S100 n = 141, PBO/M2000 n = 123). At baseline, patients included in the efficacy analysis had mean age of 54 years, mean BMI of 32 kg/m(2), mean HbA(1c) of 8.7% (8.5-8.8% across groups), and mean duration of type 2 diabetes of 4 years. At week 54, in the all-patients-treated analysis of continuing patients, leasts-squares (LS) mean changes in HbA(1c) from baseline were -1.8% (S100 + M2000), -1.4% (S100 + M1000), -1.3% (M2000), -1.0% (M1000), and -0.8% (S100). The proportions of continuing patients with an HbA(1c) < 7% at week 54 were 67% (S100 + M2000), 48% (S100 + M1000), 44% (M2000), 25% (M1000), and 23% (S100). For the patients completing treatment through week 54, LS mean changes in HbA(1c) from baseline were -1.9% (S100 + M2000), -1.7% (S100 + M1000), -1.6% (M2000), -1.2% (M1000), and -1.4% (S100). Glycemic response was generally durable over time across treatments. All treatments improved measures of beta-cell function (e. g., HOMA-beta, proinsulin/insulin ratio). Mean body weight decreased from baseline in the combination and metformin monotherapy groups and was unchanged from baseline in the sitagliptin monotherapy group. The incidence of hypoglycemia was low (1-3%) across treatment groups. The incidence of gastrointestinal adverse experiences with the co-administration of sitagliptin and metformin was similar to that observed with metformin alone. Limitations: The patient population evaluated in the 54-week efficacy analysis was a population of patients who entered the continuation period without receiving glycemic rescue therapy in the 24-week placebo-controlled period. Because the baseline HbA1c inclusion criteria ranged from 7.5 to 11% and the glycemic rescue criterion was an HbA(1c) > 8% after week 24, there was a greater likelihood of glycemic rescue in the monotherapy groups; this led to more missing data in the continuation all-patients-treated population(CAPT) analysis and fewer patients contributing to the completers analysis in the monotherapy groups. Conclusions: In this study, initial treatment with sitagliptin, metformin, or the combination therapy of sitagliptin and metformin provided substantial and durable glycemic control, improved markers of beta-cell function, and was generally well-tolerated over 54 weeks in patients with type 2 diabetes.