Tissue distribution, pharmacokinetics and identification of roscovitine metabolites in rat.

The pharmacokinetics, biodistribution and the metabolic pathway of roscovitine were investigated in Sprague-Dawley rats after a single intravenous dose of 25 mg/kg. Blood, lungs, kidney, liver, testis, adipose tissue, spleen and brain were removed at different time-points. Plasma and tissue samples were analyzed using high performance liquid chromatography. The metabolites were identified using liquid chromatography/tandem mass spectrometry and nuclear magnetic resonance spectroscopy. Roscovitine (MW=354) was cleared rapidly from circulation and highly distributed to the tissues. The elimination half-life of roscovitine in plasma and tissues was short (<30 min). A major metabolite (M1) was observed mainly in plasma and in lower levels in all other tissues. M1 was identified as conversion of the hydroxyl-group at C2 to carboxylic acid (MW=368). A second metabolite (M2) was observed mainly in liver and kidney and identified as a hydroxylation product of the C8 of the purine-ring (MW=370). A third metabolite (M3) was found in several organs and corresponded to N-dealkylation of the N9-isopropyl side-chain (MW=312). Roscovitine concentrations in the brain were 30% of that observed in plasma, however no metabolites were detected in brain. In this investigation, three major metabolites of roscovitine were isolated and identified. Also, it was shown that roscovitine eliminates rapidly from both blood and tissues.

Analysis of roscovitine using novel high performance liquid chromatography and UV-detection method: pharmacokinetics of roscovitine in rat.

Roscovitine (2-(R)-(1-ethyl-2-hydroxyethylamino)-6-benzylamino-9-isopropylpurine, is a potent and selective inhibitor of cyclin-dependent kinases (CDKs). It inhibits cdc2, cdk2, cdk5 and erk 1 and 2 by competing for the ATP binding domain of the kinases. It inhibits cell proliferation; induces DNA fragmentation and causes cell cycle arrest in S phase. Its stability and toxicity are not fully known. A liquid chromatography method was developed to measure roscovitine in human and rat plasma. The lower limit of quantitation (LLOQ) was 100ng/ml; the intra- and inter-day precision was below 10% at all control levels. Likewise, the accuracy between and within days was lower than 6% at all levels. The drug was stable at room temperature. Twenty-four hours at room temperature has result in a decrease of only 9% of the drug. The recovery of roscovitine from plasma was 84% at 750ng/ml. The present method was used to study the pharmacokinetics of the drug in a rat model. The present investigation, to the authors' knowledge, is the first analytical method reported and the first pharmacokinetics investigation of roscovitine in rat. Roscovitine was administered as a bolus injection (25mg/kg body weight). The pharmacokinetic analysis showed that roscovitine is fitted to a two-compartment open-mode with a biphasic elimination half-life (6 and 26min, respectively). The distribution volume was determined to 3.5l/kg and the clearance (Cl) was 29.5ml/min.