Aim:  The aim of this study was to compare the efficacy and safety of once-daily human glucagon-like peptide-1 analogue liraglutide with dipeptidyl peptidase-4 inhibitor sitagliptin, each added to metformin, over 52 weeks in individuals with type 2 diabetes.

Methods:  In an open-label, parallel-group trial, metformin-treated participants were randomised to liraglutide 1.2 mg/day (= 225), liraglutide 1.8 mg/day (= 221) or sitagliptin 100 mg/day (= 219) for 26 weeks (main phase). Participants continued the same treatment in a 26-week extension.

Results:  Liraglutide (1.2 or 1.8 mg) was superior to sitagliptin for reducing HbA1c from baseline (8.4–8.5%) to 52 weeks: −1.29% and −1.51% vs. −0.88% respectively. Estimated mean treatment differences between liraglutide and sitagliptin were as follows: −0.40% (95% confidence interval −0.59 to −0.22) for 1.2 mg and −0.63% (−0.81 to −0.44) for 1.8 mg (both p < 0.0001). Weight loss was greater with liraglutide 1.2 mg (−2.78 kg) and 1.8 mg (−3.68 kg) than sitagliptin (−1.16 kg) (both p < 0.0001). Diabetes Treatment Satisfaction Questionnaire scores increased significantly more with liraglutide 1.8 mg than with sitagliptin (p = 0.03). Proportions of participants reporting adverse events were generally comparable; minor hypoglycaemia was 8.1%, 8.3% and 6.4% for liraglutide 1.2 mg, 1.8 mg and sitagliptin respectively. Gastrointestinal side effects, mainly nausea, initially occurred more frequently with liraglutide, but declined after several weeks.

Conclusion:  Liraglutide provides greater sustained glycaemic control and body weight reduction over 52 weeks. Treatment satisfaction was significantly greater with 1.8 mg liraglutide, similar to 26-week results. The safety profiles of liraglutide and sitagliptin are consistent with previous reports.