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Clinical pharmacokinetic and pharmacodynamic studies with the nonclassical antifolate thymidylate synthase inhibitor 3,4-dihydro-2-amino-6-methyl-4-oxo-5-(4-pyridplthio)-quinazolone dihydrochloride (AG337) given by 24-hour continuous intravenous infusion

Lookup NU author(s): Gordon Taylor, Professor Alan Boddy, Professor Alan Calvert, Andrew Johnston, Professor Herbie Newell


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3,4-Dihydro-2-amino-6-methyl-4-oxo-5-(4-pyridylthio)-quinazolone dihydrochloride (AG337) is a nonclassical inhibitor of thymidylate synthase (TS) designed to avoid potential resistance mechanisms that can limit the activity of classical antifolate antimetabolites, A clinical pharmacokinetic and pharmacodynamic study of AG337 given as a 24-h i,v, infusion was performed, Thirteen patients received 27 courses over the dose range 75-1350 mg/m(2), Plasma AG337 concentrations were achieved which, in preclinical models, were associated with antitumor effects, AG337 clearance was saturable, and the pharmacokinetics of the drug at doses above 300 mg/m(2) was best described by a one-compartment model with saturable elimination (median K-m = 6.5 mu g/ml; range, 4.1-13 mu g/ml; median V-max = 2.0 mu g/ml/ h/m(2); range, 0.96-5.6 mu g/ml/h/m(2)), Following the end of the infusion, AG337 was cleared rapidly (t(1/2), 53-193 min), and levels were less than 0.2 mu g/ml in all patients by 48 h, Plasma protein binding was 96-98%, and the urinary excretion of AG337 as unchanged drug did not exceed 30% of the dose administered, Measurements of plasma deoxyuridine (dUrd) concentrations showed that doses of 600 mg/m(2) and above of AG337 produced a consistent elevation in plasma dUrd levels (60-290%), suggesting that TS inhibition was being achieved in patients, However, in all cases dUrd concentrations had returned to pretreatment levels 24 h after the end of the infusion, suggesting that TS inhibition was not maintained, Local toxicity, probably due to the infusate pH, was the only significant adverse effect observed, These studies have shown that cytotoxic AG337 plasma concentrations can be readily achieved without acute toxicity and that these concentrations are associated with elevations in plasma dUrd levels, The lack of prolonged dUrd elevations indicates that extended administration should be explored using central line or p.o. administration to avoid local toxicity.

Publication metadata

Author(s): Rafi, I., Taylor, G. A., Calvete, J. A., Boddy, A. V., Balmanno, K., Bailey, N., Lind, M., Calvert, A. H., Webber, S., Jackson, R. C., Johnston, A., Clendeninn, N., Newell, D. R.

Publication type: Article

Publication status: Published

Journal: Clinical Cancer Research

Year: 1995

Volume: 1

Issue: 11

Pages: 1275-1284

Print publication date: 01/11/1995

ISSN (print): 1078-0432

ISSN (electronic): 1557-3265


PubMed id: 9815922