Naoko Nagaoka

Thrombolytic Properties of a Novel Modified Human Tissue-type Plasminogen Activator (e6010): A Bolus Injection of E6010 Has Equivalent Potency of Lysing Young and Aged Canine Coronary Thrombi

Summary: The thrombolytic properties of a novel modified human tissue plasminogen activator (E6010), in which cysteine 84 in the epidermal growth factor domain is replaced by serine and that has a prolonged biological half-life, were examined. The thrombolytic efficacies of E6010 and recombinant human tissue plasminogen activator (rt-PA) on the duration of coronary artery thrombus were evaluated in a canine model (123 anesthetized dogs) with copper coil–induced left anterior descending coronary artery thrombus. Thrombi established for periods of 1, 3, or 6 h, as documented by coronary arteriography, were employed. A single bolus i.v. injection of E6010 or rt-PA and an i.v. infusion of rt-PA over 60 min were compared (n = 6). Thrombolytic efficacy was evaluated by three criteria: time to reperfusion (TR), reperfusion rate at 60 min (RR), and reocclusion rate at 60 min after reperfusion (OR). With a bolus i.v. injection of E6010 at a dose of 0.2 mg/kg or an i.v. infusion of rt-PA at a dose of 0.6 mg/kg/h, these parameters were as follows: TR, 30.0 × 15.3 and 27.5 × 4.8 min; RR, 100 and 100%; OR, 17 and 33% for 1-h aged thrombi; TR, 30.0 × 9.5 and 35.0 × 8.2 min; RR, 83 and 50%; OR, 20 and 67% for 6-h aged thrombi. These data indicate that a bolus injection of E6010 is almost equally efficacious in lysing thrombi aged both 1 and 6 h. On the other hand, in the case of rt-PA, the thrombi aged 6 h were lysed significantly less than the thrombi aged 1 h. Plasma half-lives of E6010 were t1/2α, 4.8 × 0.95 (estimated by antigen level) and 3.0 × 0.78 min (estimated by activity), and t1/2β, 51 × 5.4 (antigen level) and 22 × 7.0 min (activity). The half-lives of rt-PA were t1/2α, 3.6 × 0.23 (antigen level) and 2.1 × 0.61 min (activity), and t1/2β, 36 × 2.3 (antigen level) and 7.0 × 3.5 min (activity). We conclude that a bolus injection of E6010 may have a more potent and longer-lasting effect than i.v.-infused rt-PA in clot lysis therapy.

Intracoronary infusion of E6010 has more potent thrombolytic activity than tissue plasminogen activator (t-PA) in dogs : a higher plasma level of E6010 than t-PA causes potent thrombolytic activity

Summary: We examined the thrombolytic properties of a novel modified human tissue plasminogen activator (PA) (E6010), in which cysteine 84 is replaced by serine, and which has a prolonged biologic half-life (t½). We compared the thrombolytic efficacy of continuous intracoronary (i.e.) infusion of E6010 with that of recombinant human tissue PA (rt-PA) in a canine model with copper coil-induced 1-h-old coronary artery thrombi and also compared the relation between thrombolytic efficacy and plasma clearance represented by pharmacokinetic parameters of i.e.-infused E6010 and rt-PA. Sixty-minute E6010 and rt-PA i.e. infusions were compared. The thrombolytic effects of i.e.-infused E6010 and rt-PA, represented by time to reperfusion (TR), reperfusion rate at 60 min (RR), and reocclusion rates at 60 min after reperfusion (OR) were as follows. E6010: Dose 0.06, 0.15, 0.3 (mg/kg/h); TR 25 ± 10, 15 ± 10, 13 ± 5 (min); RR 100, 100, 100 (%); and OR 0, 0, 17 (%), respectively. Recombinant t-PA: Dose 0.06, 0.15, 0.3 (mg/kg/h); TR 47 ± 12, 18 ± 17, 14 ± 4 (min); RR 50, 75, 100 (%); and OR 100, 33, 33 (%), respectively. These findings indicate that E6010 has more potent thrombolytic activity than rt-PA. After the i.e. infusion of E6010 and rt-PA at doses of 0.3 mg/ kg/h, the i.e. and peripheral venous (intravenous, i.v.) plasma clearances, represented by the area under the plasma concentration-time curve (AUC), were assessed by antigen and by activity: E6010 assessed by antigen, i.e. 200.1 ± 88.6, i.v. 70.0 ± 39.9 (µg · min/ml); assessed by activity, i.e. 142.5 ± 93.3, i.v. 23.5 ± 15.3 (µg · min/ ml); and rt-PA assessed by antigen, i.e. 81.4 ± 47.4, i.v. 14.1 ± 7.1 (µg · min/ml); and assessed by activity, i.e. 55.1 ± 23.0, i.v. 9.4 ± 5.0 (µg · min/ml). We conclude that the higher plasma level of the active form of E6010, especially its i.e. level, was responsible for its enhanced thrombolytic effect