Pharmacokinetic, pharmacodynamic, and tolerability profiles of the dipeptidyl peptidase-4 inhibitor linagliptin: a 4-week multicenter, randomized, double-blind, placebo-controlled phase IIa study in Japanese type 2 diabetes patients.
BACKGROUND
The dipeptidyl-peptidase-4 (DPP-4) inhibitor linagliptin is under clinical development for treatment of type 2 diabetes mellitus (T2DM). In previous studies in white populations it showed potential as a once-daily oral antidiabetic drug.


OBJECTIVES
In compliance with regulatory requirements for new drugs intended for use in the Japanese population, this study investigated the pharmacokinetics, pharmacodynamics, and tolerability of multiple oral doses of linagliptin in Japanese patients with T2DM.


METHODS
In this randomized, double-blind, placebo-controlled multiple dose study, 72 Japanese patients with T2DM were assigned to receive oral doses of linagliptin 0.5, 2.5, or 10 mg or placebo (1:1:1:1 ratio) once daily for 28 days. For analysis of pharmacokinetic properties, linagliptin concentrations were determined from plasma and urinary samples obtained throughout the treatment phase, with more intensive samplings on days 1 and 28. DPP-4 inhibition, glycosylated hemoglobin A1c (HbA(1c)) levels, and plasma glucose and glucagon-like peptide-1 (GLP-1) levels were compared by mixed effect model. Tolerability was assessed throughout the study by physical examination, including blood pressure and pulse rate measurements, 12-lead ECG, and laboratory analysis.


RESULTS
Baseline demographic characteristics were well balanced across the 4 treatment groups (mean [SD] age, 59.7 [6.4] years in the placebo group, 60.8 [9.2] years in the 0.5 mg group, 60.2 [6.4] years in the 2.5 mg group, and 59.1 [8.6] years in the 10 mg group; mean [SD] weight, 67.2 [10.0] kg in the placebo group, 64.5 [9.0] kg in the 0.5 mg group, 69.6 [9.4] kg in the 2.5 mg group, and 63.5 [12.2] kg in the 10 mg group; mean [SD] duration of T2DM diagnosis, 5.1 [4.2] years in the placebo group, 5.2 [4.7] years in the 0.5 mg group, 5.9 [4.8] years in the 2.5 mg group, and 2.6 [2.3] years in the 10 mg group). The majority of the patients treated were male (76.4%). Use of previous antidiabetic medication was more common in the 2.5 mg linagliptin group (44%) than in the 0.5 or 10 mg linagliptin (15.8% and 22.2%, respectively) or placebo groups (35.3%). Total systemic exposure in terms of linagliptin AUC and C(max) (which occurred at 1.25-1.5 hours) increased in a less than dose-proportional manner. The terminal half-life was long (223-260 hours) but did not reflect the accumulation half-life (10.0-38.5 hours), resulting in a moderate accumulation ratio of <2.9 that decreased with increasing dose. Urinary excretion increased with linagliptin doses but was <7% at steady state for all dose groups. Inhibition of plasma DPP-4 at 24 hours after the last dose on day 28 was approximately 45.8%, 77.8%, and 89.7% after linagliptin 0.5, 2.5, and 10 mg, respectively. At steady state, linagliptin was associated with dose-dependent increases in plasma GLP-1 levels, and the postprandial GLP-1 response was enhanced. Statistically significant dose-dependent reductions were observed in fasting plasma glucose levels at day 29 for all linagliptin groups (-11.5, -13.6, and -25.0 mg/dL for the 0.5, 2.5, and 10 mg groups, respectively; P < 0.05 for all linagliptin groups). Linagliptin also produced statistically significant dose-dependent reductions from baseline for glucose area under the effect curve over 3 hours after meal tolerance tests (-29.0 to -68.1 mg × h/dL; P < 0.05 for all 3 linagliptin groups). For the 0.5 and 10 mg linagliptin-treated groups, there were statistically significant reductions in HbA(1c) from baseline compared with placebo, despite the relatively low baseline HbA(1c) (7.2%) and small sample size (P < 0.01 for both groups). The greatest reduction in HbA(1c) (-0.44%) was seen in the highest linagliptin dose group (10 mg). On dosing for up to 28 days, linagliptin was well tolerated with no reported serious adverse events or symptoms suggestive of hypoglycemia. Overall, fewer adverse events were reported by patients after linagliptin than after placebo (11 of 55 [20%] vs 6 of 17 [35%]).


CONCLUSIONS
Linagliptin demonstrated a nonlinear pharmacokinetic profile in these Japanese patients with T2DM consistent with the findings of previous studies in healthy Japanese and white patients. Linagliptin treatment resulted in statistically significant and clinically relevant reductions in HbA(1c) as soon as 4 weeks after starting therapy in these Japanese patients with T2DM, suggesting that clinical studies of longer duration in Japanese T2DM patients are warranted.