Pharmacokinetic and pharmacodynamic assessments of the dipeptidyl peptidase-4 inhibitor PHX1149: double-blind, placebo-controlled, single- and multiple-dose studies in healthy subjects.

Background: PHX1149 is a dipeptidyl peptidase-4 (DPP4) inhibitor that is currently in clinical development for the treatment of type 2 diabetes mellitus. PHX1149 is a small (molecular weight = 241.16 Da), highly water-soluble (>2 g/mL), orally active molecule with a selectivity index of 15- to 319-fold relative to those of other members of the DPP family. The biochemical median inhibitory concentration of DPP4 is 2.5 nmol/L.

Objective: The aim of these 2 double-blind, randomized, placebo-controlled studies was to examine the pharmacokinetic (PK) parameters and pharmacodynamic (PD) properties and tolerability of single and multiple ascending doses of PHX1149 in healthy human subjects.

Methods: Healthy men and women aged 18 to 60 years were recruited to participate in a single- or a multiple-dose study in which sequential dose escalation paradigm was used. In the single-dose study, subjects were given a single oral dose of PHX1149 50 to 500 mg or placebo; in the multiple-dose study, subjects were given PHX1149 at doses from 50 to 400 mg or placebo QD for 13 days. There was no intrasubject dose escalation. Blood samples were collected from each subject at a series of time points ranging from 1 hour before to 24 hours after dosing on day 1 in the single- dose study and on days 1, 7, and 13 in the multiple-dose study. PK and PD analyses were performed in plasma samples to determine Cmax, Tmax, AUC0-t, AUC0-infinity, and DPP4 enzymatic activity. The drug accumulation index was also calculated for each dose of PHX1149 in the multiple-dose study. Adverse events (AEs) were monitored in both studies through physical examinations, including measurement of vital signs, and clinical laboratory testing. In both studies, electrocardiography was performed.

Results: The single- and multiple-dose studies enrolled 30 and 28 subjects, respectively, for a total enrollment in the 2 studies of 58 healthy adult subjects. The distribution of male and female subjects was 14 (47%) and 16 (53%), respectively, in the single- dose study and 16 (57%) and 12 (43%) in the multiple- dose study. In the single-dose study, 28 (93%) subjects were white; in the multidose study, all subjects were white. The mean (SD) ages in the 2 studies were 51 (10) and 51 (12) years, respectively; and mean (SD) body weights were 89.0 (10.8) and 81.1 (10.9) kg, respectively. PHX1149 exhibited dose-proportional increases in mean Cmax AUC0-t, and AUC0-infinity across the evaluated dose ranges. Tmax ranged from 2 to 4 hours, and t1/2 ranged from approximately 10 to 13 hours. No drug accumulation was observed. Plasma DPP4 inhibition at 24 hours was >or=50% in the multiple-dose study for doses of >or=100 mg. PHX1149 400 mg achieved approximately 90% 24-hour plasma DPP4 inhibition in the multiple-dose study. All AEs were characterized as mild, with the exception of 1 case of moderate edema, which occurred 17 days after the end of dosing in the multiple-dose study (50-mg dose group) and was considered unrelated to the study drug. Adverse events were experienced by 47% of all subjects studied in the single-dose study and 93% of subjects in the multiple-dose study. The rates of AEs were comparable between the study and placebo groups.

Conclusions: The PK parameters and PD properties of PHX1149 were suitable (eg, tl/2, DPP4 inhibition) for once-daily dosing in this group of 58 healthy subjects. All doses were well tolerated.