Efficacy and safety of linagliptin 2.5 mg twice daily versus 5 mg once daily in patients with type 2 diabetes inadequately controlled on metformin: a randomised, double-blind, placebo-controlled trial

Objective: Glycaemic control in patients with type 2 diabetes (T2DM) is often not achieved or not sustained using monotherapy such as metformin, necessitating the addition of other antihyperglycaemic agents. Linagliptin, a dipeptidyl peptidase-4 inhibitor, is licensed for 5 mg once-daily dosing. As metformin is administered twice daily, a fixed-dose combination of these compounds would require twice-daily administration of linagliptin. This study evaluated whether 2.5 mg twice-daily dosing of linagliptin has comparable efficacy and safety to 5 mg once-daily dosing when given in addition to metformin twice daily in patients with inadequate glycaemic control. Methods: A total of 491 T2DM patients with glycated haemoglobin (HbA1c) 7.0-10.0% were randomised (5:5:1) to double-blind treatment with linagliptin 2.5 mg twice daily, 5 mg once daily or placebo, respectively, in addition to continuing metformin twice daily (>= 1500 mg/day or maximally tolerated dose). The primary endpoint was change from baseline in HbA1c after 12 weeks. ClinicalTrials.gov, NCT01012037. Results: Mean baseline HbA1c for all patients was 7.97%. After 12 weeks, linagliptin 2.5 mg twice daily and 5 mg once daily both significantly reduced HbA1c (placebo-adjusted changes from baseline -0.74% (95% CI -0.97, -0.52) and -0.80% (95% CI -1.02, -0.58), respectively, both p<0.0001). The treatment difference (twice daily - once daily) between the linagliptin regimens was 0.06 (95% CI -0.07, 0.19), the upper bound of which was less than the predefined noninferiority margin (0.35%). The overall incidence of adverse events with linagliptin 2.5 mg twice daily, 5 mg once daily and placebo was 43.0%, 34.8%, and 38.6% respectively. Hypoglycaemia was rare (3.1% with linagliptin 2.5 mg twice daily, 0.9% with 5 mg once daily, 2.3% with placebo) with no severe episodes. Study limitations include duration, patient population (mainly white) and absence of postprandial glucose data. Conclusions: Linagliptin 2.5 mg twice daily had non-inferior HbA1c-lowering effects after 12 weeks compared to 5 mg once daily, with comparable safety and tolerability, in T2DM patients inadequately controlled with metformin.