title: Evaluation of a low molecular weight modulator of human plasminogen activator inhibitor-1 activity.
abstract: A critical component in the regulation of thrombus formation and clearance is the balance between tissue plasminogen activator (tPA) and plasminogen activator inhibitor type-1 (PAI-1). An increase in the plasma concentration of PAI-1 has been proposed as a risk factor in thrombotic disease. Inhibition of PAI-1 activity may have utility in the treatment of thromboembolic disease. We report here the evaluation of three diketopiperazine-based low molecular weight inhibitors of PAI-1 activity (XR334, XR1853 and XR5082). In vitro these compounds reversed the inhibitory effects of PAI-1 against both tPA and urokinase (UK) (IC50: 5 to 80 muM). In contrast, other serpin-serine protease interactions, including alpha 1-antitrypsin-trypsin, alpha 2-antiplasmin- plasmin and antithrombin-thrombin, were not affected, neither did these inhibitors affect global tests of haemostasis. In the light of this promising in vitro profile these compounds were evaluated in a standard radioisotopic assay of clot lysis in whole rat blood following intravenous administration. In this assay these compounds dose-dependently enhanced fibrinolysis ex vivo. After intravenous bolus administration XR334, XR1853 and XR5082 at 5 mg/kg increased clot lysis by 32.0 +/- 5.1% SEM (n = 25, p < 0.01), 36.7 +/- 3.5% SEM (n = 36, p < 0.01) and 60.0 +/- 2.8% SEM (n = 17, p < 0.01) respectively compared to vehicle. Intravenous infusion of these compounds (1 mg/kg/min for 20 min) significantly prolonged (approximately twofold) the time to blood vessel occlusion in the rat electrically-stimulated carotid artery thrombosis model. Thus, these low molecular weight inhibitors of PAI-1 activity enhanced fibrinolysis ex vivo and protected against thrombus formation in the rat.
authors.affiliation: Xenova Limited, Slough, Berkshire, UK.
authors.forename: P A
authors.initials: PA
authors.lastname: Charlton
authors.forename: R W
authors.initials: RW
authors.lastname: Faint
authors.forename: F
authors.initials: F
authors.lastname: Bent
authors.forename: J
authors.initials: J
authors.lastname: Bryans
authors.forename: I
authors.initials: I
authors.lastname: Chicarelli-Robinson
authors.forename: I
authors.initials: I
authors.lastname: Mackie
authors.forename: S
authors.initials: S
authors.lastname: Machin
authors.forename: P
authors.initials: P
authors.lastname: Bevan
mesh_terms: D000818:Animals; D006801:Humans; D008297:Male; D010455:Peptides / Q000302:isolation & purification* / Q000378:metabolism; D010879:Piperazines / Q000302:isolation & purification*; D017395:Plasminogen Activator Inhibitor 1 / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D011994:Recombinant Proteins / Q000378:metabolism; D010959:Tissue Plasminogen Activator / Q000378:metabolism
chemical_list: D010455:Peptides; D010879:Piperazines; D017395:Plasminogen Activator Inhibitor 1; D011994:Recombinant Proteins; C102986:XR 1853; C102987:XR 5082; C102985:XR 334; D010959:Tissue Plasminogen Activator