Population Pharmacokinetics of the Novel Adenosine A Antagonist/Inverse Agonist KW-6356 and Its Active Metabolite Following Single and Multiple Oral Administration in Healthy Individuals and Patients with Parkinson's Disease.

KW-6356 is a selective antagonist and inverse agonist of the adenosine A receptor. The primary aim of the present analysis was to characterize the pharmacokinetics (PK) of KW-6356 and its active metabolite M6 in healthy subjects and patients with Parkinson's disease (PD). We pooled concentration-time data from healthy subjects and patients with PD who were administered KW-6356. Using these data, we developed a population PK model by sequentially fitting the KW-6356 parameters followed by the M6 parameters. A first-order absorption with a 1-compartment model for KW-6356 and a 1-compartment model for M6 best described the profiles. The covariates included in the final models were food status (fed/fasted/unknown) on first-order absorption rate constant, baseline serum albumin level on apparent clearance of KW-6356, and baseline body weight on apparent volume of distribution of KW-6356 and apparent clearance of M6. No covariate had a clinically meaningful impact on KW-6356 or M6 exposure.