Efficacy and safety of combination therapy with vildagliptin and metformin vs, metformin monotherapy for Type 2 Diabetes Mellitus therapy: a meta-analysis

OBJECTIVE: The aim is to assess the comparative efficacy and safety of combination therapy with vildagliptin and metformin vs. metformin monotherapy in the treatment of type 2 diabetes mellitus (T2DM). MATERIALS AND METHODS: We searched on PubMed, Cochrane Library, Web of Science, and Embase databases for randomized controlled trials (RCTs) of combination therapy with vildagliptin and metformin vs. metformin monotherapy in patients with T2DM published up to 30 February 2021. The Cochrane tool and Revman 5.3 software was used to assess the risk of bias and conducted the meta-analysis in the included RCTs. Evidence level was assessed by the Grades of Recommendation, Assessment, Development and Evaluation (GRADE) approach. RESULTS: A total of 11 RCTs and 8533 patients were included. For the efficacy, we found that combination therapy with vildagliptin and metformin (dose of metformin >= 1500mg/d) had a significantly higher reduction in hemoglobin A1c (HbA1c) [mean differences (MD)= -0.59, 95% CI (-0.28, -0.16), p<0.00001] and fasting plasma glucose (FPG) level [MD= -0.82, 95% CI (-1.09, -0.56), p<0.00001] than combination therapy with vildagliptin and metformin (dose of metformin <1500 mg/d). Vildagliptin plus metformin as combination therapy reduced body weight loss ratio [MD=0.22, 95% CI (0.17, 0.27), p<0.00001 ] when compared with metformin monotherapy. In terms of safety, the vildagliptin plus metformin as combination therapy did not increase risk of total adverse events (AEs) [RR=0.98, 95% CI (0.94,1.02), p=0.29], however there were significant statistical difference and did not increase the risk of diarrhea [RR=0.55, 95% CI (0.40, 0.76), p=0.0003] and Gastrointestinal (GI) disorders [RR=0.72, 95% CI (0.58, 0.91), p=0.006], but significantly increased risk of dizziness [RR=1.41, 95% CI (1.06, 1.88), p=0.02] when compared with metformin monotherapy. CONCLUSIONS: Compared with metformin, vildagliptin combined with metformin could significantly reduce FPG, HbA1c and body weight. When the dose of metformin in the combination group of vildagliptin and metformin is >= 1500mg/d, the results showed significant reduction in HbA1c and FPG. In addition, it had no risk of increase in total AEs, diarrhea, and GI disorders, but had significant risk of increase in dizziness. GRADE showed that the quality of evidence had high certainty in FPG and moderate certainty in HbA1c, body weight and all AEs.