Saxagliptin Add-on Therapy to Insulin With or Without Metformin for Type 2 Diabetes Mellitus: 52-Week Safety and Efficacy

Achievement of glycemic control is an important objective in the management of type 2 diabetes mellitus (T2DM).

The objective of this study was to evaluate the safety and efficacy of the dipeptidyl peptidase-4 inhibitor saxagliptin versus placebo as add-on therapy in patients with T2DM inadequately controlled with insulin alone or insulin plus metformin.

This was a long-term (28-week) extension of a short-term (24-week), randomized, double-blind, parallel-group trial of saxagliptin 5 mg once daily versus placebo as add-on therapy to open-label insulin or insulin plus metformin therapy totaling 52 weeks of treatment. In contrast with the goal of maintaining a stable insulin dosage during the short-term phase, during the extension phase the insulin dosage was flexible and adjusted as deemed appropriate by the investigator. The study was conducted in a clinical practice setting, including family practice and hospital sites. Patients with T2DM aged 18–78 years with glycated hemoglobin (HbA_1c) 7.5–11 % on a stable insulin regimen (30–150 U/day with or without metformin) for ≥8 weeks at screening were included in the study. Patients were stratified by metformin use and randomly assigned 2:1 to oral saxagliptin 5 mg (n = 304) or placebo (n = 151) once daily. All patients who completed the initial 24 weeks of treatment were eligible to participate in the 28-week extension, regardless of whether they had required rescue treatment. The main outcome measure was change in HbA_1c from baseline to week 52.

In general, the outcomes achieved at week 24 were sustained to week 52. Adjusted mean change from baseline HbA_1c at week 52 was greater with saxagliptin (−0.75 %) versus placebo (−0.38 %); the adjusted between-group difference was −0.37 % (95 % CI −0.55 to −0.19); between-group differences were similar in patients treated with metformin (−0.37 % [95 % CI −0.59 to −0.15]) and without metformin (−0.37 % [95 % CI −0.69 to −0.04]). At week 52, a greater proportion of patients receiving saxagliptin achieved HbA_1c <7 % than those receiving placebo (21.3 vs. 8.7 %; between-group difference 12.6 % [95 % CI 6.1–19.1]). The increase from baseline in mean total daily insulin dose at week 52 was numerically smaller with saxagliptin (5.67 vs 6.67 U with placebo; difference, −1.01 U [95 % CI −3.24 to 1.22]). During the 52-week study period, the proportion of patients reporting ≥1 adverse event (AE) was 66.4 % with saxagliptin and 71.5 % with placebo, the majority being mild or moderate in intensity. The most common AEs (≥5 % with saxagliptin or placebo) were urinary tract infection, nasopharyngitis, upper respiratory tract infection, headache, influenza, and pain in extremity; the incidence of each AE was similar between treatment groups. In the saxagliptin and placebo groups, the incidence of reported hypoglycemia was 22.7 and 26.5 %, respectively; the incidence of confirmed hypoglycemia (fingerstick glucose ≤50 mg/dL [≤2.77 mmol/L] with characteristic symptoms) was 7.6 and 6.6 %, respectively. Adjusted mean change from baseline body weight was +0.8 kg with saxagliptin and +0.5 kg with placebo.

Saxagliptin 5 mg once daily as add-on to insulin, with or without concomitant metformin, produced a durable improvement in glycemic control and was well tolerated over 52 weeks of treatment.