Comparative Efficacy of Adding Sitagliptin to Metformin, Sulfonylurea or Dual Therapy: A Propensity Score-Weighted Cohort Study

INTRODUCTION: The aim of this study was to assess the efficacy of co-administering sitagliptin to patients with inadequate glycemic control following treatment with metformin (MET), sulfonylurea (SU), or MET + SU. METHODS: A cohort of 25,386 patients with type 2 diabetes mellitus (hemoglobin A1c [HbA1C] >53 mmol/mol or 7%), newly treated with sitagliptin between 2007 and 2013, was sourced from UK general practices via The Health Improvement Network database. Among these, eligible patients were segregated into three groups: MET (n = 3364), SU (n = 509), or MET + SU therapy (n = 5929). The relative efficacy of sitagliptin added to SU or MET + SU compared with sitagliptin added to MET monotherapy was assessed with regards to HbA1c and body weight changes from baseline up to 52 weeks. The glycemic efficacy was a measure of average treatment effects obtained from multivariable linear regression models and propensity score-matching analysis. RESULTS: A total of 9802 patients were included in the study. Overall, addition of sitagliptin 100 mg once daily resulted in 5.5 mmol/mol (0.5%) HbA1c reduction (P < 0.001) and 0.8 kg weight reduction at 1 year (P < 0.001). Efficacy was similar across the treatment groups, but in patients with baseline HbA1c ≥9% adding sitagliptin to MET + SU produced a significantly smaller reduction in HbA1c when compared to the reference group MET (MET + SU vs. MET only: −0.5% vs. −0.7%, P < 0.001). The mean HbA1c reduction from baseline within this subgroup of patients was not significantly different between SU and MET monotherapies (−0.8% vs. −0.7%, respectively, P = 0.4). Across treatment groups, HbA1c reductions with add-on sitagliptin occurred after 24 weeks of treatment with a peak reduction occurring between 36 and 48 weeks, and receded after week 48. CONCLUSION: In a real-world general practice setting, sitagliptin was effective in patients with suboptimal glycemic control with MET, SU or dual therapy, maximum between 36 and 48 weeks, but in patients with HbA1c of >9% receiving MET + SU therapy, adding sitagliptin, as a third agent, conferred minimal benefit. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s13300-015-0110-6) contains supplementary material, which is available to authorized users.