An inhibitor of the plasmin activating enzymes streptokinase fibrinokinase and urokinase (IC50s ~8 M for all in an enzyme assay) selective for plasmin activating enzymes over trypsin (IC50 500 M) inhibits in vitro plasmin activation and fibrinolysis in a dose-dependent manner reduces ex vivo fibrinolysis in dog plasma following i.p. administration at doses ranging from 20-100 mg/kg