TNK-Tissue Plasminogen Activator in Acute Myocardial Infarction

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Abstract
TNK-tissue plasminogen activator (TNK-TPA) is a genetically engineered variant of TPA, which in experimental models has a slower plasma clearance and greater fibrin specificity and is 80-fold more resistant to plasminogen activator inhibitor-1 than alteplase TPA. The thrombolysis in Myocardial Infarction (TIMI) 10A trial was a Phase 1, dose-ranging pilot trial designed to evaluate the pharmacokinetics, safety, and efficacy of TNK-TPA in patients with acute myocardial infarction. One hundred thirteen patients with acute ST-segment elevation myocardial infarction presenting within 12 hours and without contraindications to thrombolysis were enrolled and treated with a single bolus of TNK-TPA over 5 to 10 seconds with doses ranging from 5 to 50 mg. TNK-TPA demonstrated a plasma clearance of 151 +/- 55 mL/min and a half-life of 17 +/- 7 minutes. Comparable values for wild-type TPA are 572 +/- 132 mL/min and 3.5 +/- 1.4 minutes, respectively. Systemic fibrinogen and plasminogen levels fell by only 3% and 13%, respectively, at 1 hour after TNK-TPA administration. TIMI grade 3 flow at 90 minutes was achieved in 57% to 64% of patients at the 30- to 50-mg doses. Seven patients (6.2%) experienced a major hemorrhage, which occurred at a vascular access site in six patients. TNK-TPA has a prolonged half-life so it can be administered as a single bolus. TNK-TPA appears to be very fibrin specific, and the initial patency and safety profiles are encouraging. Further study of this new thrombolytic agent is ongoing.

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