Background: To evaluate the safety of several doses of a new thrombolytic, TNK tissue-plasminogen activator (tPA), given as a single bolus to patients with acute myocardial infarction.
Methods and results: A total of 3235 patients were given TNK-tPA: 1705 received 30 mg, 1457 received 40 mg, and 73 received 50 mg. The 50-mg dose was discontinued and replaced by 40 mg because of increased bleeding observed in the Thrombolysis In Myocardial Infarction (TIMI)-10B study, the phase II angiographic efficacy trial conducted in parallel with this study. The total stroke rate at 30 days in the trial was 1.5%. An intracranial hemorrhage was observed in 25 patients (0.77%): 16 in the 30-mg group (0.94%) and 9 in the 40-mg group (0.62%). No strokes occurred in the 73 patients treated with 50 mg TNK-tPA. In patients treated within 6 hours after symptom onset the rates of intracranial hemorrhage were 0.56% (30 mg TNK-tPA) and 0.58 (40 mg TNK-tPA). Death, death or nonfatal stroke, or severe bleeding complications occurred in a low proportion of patients: 6.4%, 7.4%, and 2.8%, respectively, without significant differences among the treatment groups.
Conclusions: The overall safety profile of a single bolus of 30 to 50 mg TNK-tPA is comparable to that of accelerated r-tPA observed in other large trials. The safety data from this trial and the patency data of TIMI-10B were the basis for a decision to conduct a large phase III mortality trial comparing weight-adjusted single-bolus TNK-tPA with accelerated r-tPA (ASSENT-2).