Pharmacokinetics and Metabolism of MZPES, a Novel Lipophilic Antifolate

Abstract

m-Azidopyrimethamine ethanesulphonate salt (MZPES) is a new potent dihydrofolate reductase inhibitor designed to be both lipophilic and rapidly biodegradable. The drug is active against some methotrexate-refractory cell lines and against a broad spectrum of malignant cells in murine models. The pharmacokinetics of the drug were evaluated in the mouse, rat and man. A specific analytical method was developed to allow determination of MZP (the free base of MZPES) and its putative metabolite m-amino-pyrimethamine (MAP) in plasma, urine, faeces and tissues. Analytical methodology involved solvent extraction followed by reversed-phase ion-pair high pressure liquid chromatography. Mice were dosed at 10 and 20 mg/kg IP and 10 mg/kg PO. Absorption was rapid from both sites with a mean plasma elimination half-life of 4 hours. Oral bio-availability, relative to intraperitoneal injection, exceeded 95% in the mouse. MZP attained concentrations in mouse tissues 4 to 14 fold greater than those found in plasma and penetrated the blood-brain barrier effectively. Following intraperitoneal administration of MZP to the rat, the recovery of MZP and MAP in urine and faeces was 14% during 72 hours. MZPES was formulated for a phase I clinical evaluation as a 1% w/v aqueous solution and was administered by IV infusion in 5% dextrose over 1 hour. The drug obeyed 2-compartment kinetics with a central compartment volume of 27 litres and a volume of distribution of 118 litres. Plasma distribution and elimination half-lives were 0.27 and 34 hours respectively and plasma clearance was 7.5 L/hr. MZP was removed from plasma more rapidly than the prototypic lipophilic dihydrofolate reductase inhibitor metoprine (half-life 216 hours). The pharmacokinetics of MZPES showed no dose-dependency over the dose-range studied (27 to 460 mg/m2). The dose-limiting toxicity was nausea and vomiting. The short half-life of the drug should allow easy assessment of the optimum dose and schedule of administration.

Divisions: College of Health & Life Sciences
Additional Information: Copyright © STEPHEN GEORGE HENRY PASHLEY, 1987. STEPHEN GEORGE HENRY PASHLEY asserts their moral right to be identified as the author of this thesis. This copy of the thesis has been supplied on condition that anyone who consults it is understood to recognise that its copyright rests with its author and that no quotation from the thesis and no information derived from it may be published without appropriate permission or acknowledgement. If you have discovered material in Aston Publications Explorer which is unlawful e.g. breaches copyright, (either yours or that of a third party) or any other law, including but not limited to those relating to patent, trademark, confidentiality, data protection, obscenity, defamation, libel, then please read our Takedown Policy and contact the service immediately.
Institution: Aston University
Uncontrolled Keywords: pharmacokinetics,metabolism,MZPES,lipophilic antifolate,cancer
Last Modified: 25 Apr 2024 13:02
Date Deposited: 24 Jan 2011 11:28
Completed Date: 1987
Authors: Pashley, Stephen G.H.

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