Impact of baseline characteristics on glycemic effects of add‐on saxagliptin or acarbose to metformin therapy: Subgroup analysis of the SMART study in Chinese patients with type 2 diabetes mellitus

AIMS/INTRODUCTION: This secondary analysis of the 24‐week SMART study examined the efficacy of add‐on saxagliptin or acarbose to metformin across different patient subgroups with type 2 diabetes mellitus, based on baseline characteristics. MATERIALS AND METHODS: Randomized patients (n = 481) were classified into subgroups based on their baseline age (<65, ≥65 years), body mass index (BMI; <24, 24–<28, ≥28 kg/m(2)), glycated hemoglobin (HbA1c; <8%, 8–<9%, 9–<10%, ≥10%) and renal function (creatinine clearance 50–<80, ≥80 mL/min). Treatment effects on primary outcome (HbA1c) and key secondary outcomes of fasting plasma glucose (FPG), 2‐h postprandial glucose and homeostatic model assessment of β‐cell function were assessed across patient subgroups. RESULTS: For saxagliptin, reductions in HbA1c from baseline to week 24 were consistent across different subgroups regardless of baseline age, body mass index, HbA1c and renal function (range −0.66 to −1.16%). Saxagliptin was associated with consistent reductions in FPG (−0.60 to −1.33 mmol/L) and 2‐h postprandial glucose (−0.48 to −1.95 mmol/L) across the majority of subgroups studied. The efficacy of acarbose on FPG attenuated progressively with increasing baseline HbA1c (+0.86 to −1.43 mmol/L); an increase from baseline FPG was observed in patients with HbA1c >9%. The effect of acarbose on postprandial glucose was also variable (+0.23 to −3.38 mmol/L). CONCLUSIONS: As add‐on to metformin, both saxagliptin and acarbose reduced HbA1c regardless of baseline HbA1c, age, body mass index and renal function; however, only saxagliptin was effective at a stable glycemic control (FPG and PPG). The efficacy of acarbose on FPG and PPG was significantly attenuated in patients with higher baseline HbA1c (≥8%).