BACKGROUND: Recombinant staphylokinase (STAR) was shown recently to offer promise for coronary arterial thrombolysis in patients with evolving myocardial infarction. The present multicenter randomized open trial was designed to assess the thrombolytic efficacy, safety, and fibrin specificity of STAR relative to accelerated alteplase (recombinant tissue-type plasminogen activator [RTPA]). METHODS AND RESULTS: One hundred patients with evolving myocardial infarction of < 6 hours' duration and with ST-segment elevation were allocated to accelerated and weight-adjusted RTPA over 90 minutes (52 patients) or to STAR (the first 25 patients to 10 mg and the next 23 patients to 20 mg given intravenously over 30 minutes). All patients received aspirin and intravenous heparin. The main end points were coronary artery patency and plasma fibrinogen levels at 90 minutes. Thrombolysis in Myocardial Infarction (TIMI) perfusion grade 3 at 90 minutes was achieved in 62% of STAR patients versus 58% of RTPA patients (risk ratio, 1.1; 95% CI, 0.76 to 1.5). With 10 mg STAR, TIMI grade 3 patency was 50% (risk ratio, 0.86; 95% CI, 0.54 to 1.4 versus RTPA); with 20 mg STAR, it was 74% (risk ratio, 1.3; 95% CI, 0.90 to 1.8 versus RTPA). Residual fibrinogen levels at 90 minutes were 118 +/- 47% (mean +/- SD) of baseline with STAR and 68 +/- 42% with RTPA (P < .0005). STAR therapy was not associated with an excess mortality or electric, hemorrhagic, mechanical, or allergic complications. However, patients developed antibody-mediated STAR-neutralizing activity from the second week after STAR treatment. As an addendum to the randomized study, 5 patients were given 40 mg STAR over 30 minutes, resulting in TIMI perfusion grade 3 at 90 minutes in 4 patients without fibrinogen breakdown (residual levels at 90 minutes of 105 +/- 8% of baseline). CONCLUSIONS: STAR appears to be at least as effective for early coronary recanalization as and significantly more fibrin-specific than accelerated RTPA in patients with evolving myocardial infarction.