Effective thrombolysis by a recombinant Escherichia coli-produced protease domain of tissue-type plasminogen activator in the rabbit model of jugular vein thrombosis

Abstract

The recombinant Escherichia coli-produced protease domain of human tissue-type plasminogen activator (t-PA) was evaluated in a rabbit model of jugular vein thrombosis. In parallel to dose-ranging experiments with the protease including pharmacokinetic analysis, the effects of the protease were compared with those of vehicle and the reference thrombolytic agents streptokinase, alteplase and reteplase. The main endpoints of the study were the extent of thrombolysis, the amount of blood lost from a fresh wound, and the degree of systemic lysis evidenced by fibrinogen reduction. The half-life of the protease domain was in the range of 11–19 min. All protease groups except one achieved higher (2P<0.05) thrombolysis rates (30.8±10.0 to 61.7±4.8%) than vehicle (11.5±2.1%). Lysis rates after single bolus injection and 90 min infusion of 2 mg/kg of the protease were not significantly different from those after streptokinase, alteplase and reteplase. The 2 mg/kg doses of the protease domain reduced fibrinogen more markedly (2P<0.01) than vehicle, alteplase and streptokinase and were associated with a systemic lytic state. However, after a single bolus of 2 mg/kg of the protease the blood loss from fresh wounds was lower (2P<0.05) than after 1.45 mg/kg of alteplase infused over 90 min (1439±390 vs 4651±1066 mg). In conclusion, the recombinant unglycosylated protease domain of human t-PA is an effective thrombolytic agent in the rabbit model of jugular vein thrombosis. Effective doses of the protease domain were associated with a systemic lytic state which does not seem to affect the potential for reduced rebleeding from fresh wounds after a single bolus injection of the protease as compared with alteplase infusion.