Pharmacokinetic properties and effects of PT302 after repeated oral glucose loading tests in a dose-escalating study

PT302 is a sustained-release exenatide under clinical development for the treatment of type 2 diabetes mellitus.

The aim of this study was to evaluate the pharmacokinetic properties, pharmacodynamic properties, and tolerability of PT302 after a single subcutaneous injection in healthy individuals.

A dose-block randomized, double-blind, placebo-controlled, dose-escalating study (0.5, 1, 2, and 4 mg) was performed in 34 healthy individuals. The plasma concentrations of exenatide in serial blood samples were quantified for 56 days after dosing with an exendin-4 fluorescent immunoassay kit. Noncompartmental analysis was performed to assess the pharmacokinetic characteristics of PT302. Oral glucose tolerance tests were repeated weekly until day 42; the concentrations of serum glucose, serum C-peptide, plasma insulin, and plasma glucagon were measured for 2 hours to evaluate the pharmacodynamic characteristics of PT302. Clinical laboratory tests, vital signs, physical examinations, 12-lead ECGs, and adverse events were monitored to evaluate the safety profile and tolerability.

PT302 exhibits a biphasic pharmacokinetic profile, with the initial peak occurring 2 hours after administration. PT302 was quantifiable in the plasma until days 23, 30, 32, and 55 (median) in the 0.5-mg, 1-mg, 2-mg, and 4-mg dosage groups of PT302, respectively. Systemic exposure increased proportionally to the dose during the entire dose range investigated. The pharmacodynamic effect of PT302 on the postprandial response of insulin and C-peptide was significant on days 21 to 28 at the 4-mg dose and was positively correlated with plasma exenatide concentrations, whereas the correlations with glucose and glucagon were not significant. The fasting levels of these pharmacodynamic biomarkers were not altered by PT302. The most common adverse events were injection site induration and pruritus related to inflammatory foreign body reaction, which were mild and spontaneously resolved within several weeks.

The pharmacokinetic characteristics of PT302 were biphasic and dose proportional. A single 4-mg dose of PT302 significantly increased the insulin and C-peptide response to oral glucose loading and was well tolerated in healthy individuals.