Can plasminogen activators be improved?

T he widespread application of plasminogen activators in the treatment of myocardial infarction has resulted in a significant reduction in mortality.",2 Most patients have been treated with two very different drugs: streptokinase, a bacterial protein that is the product of fermentation technology dating from the 1930s, and recombinant tissue-type plasminogen activator (rt-PA), a human protein that is one of the first widely used fruits of molecular biology. A recent study comparing streptokinase and rt-PA, presented by the Gruppo Italiano per lo Studio della Streptochinasi nell'Infarto Miocardico (GISSI) investigators at the 39th Annual Scientific Session of the American College of Cardiology (March 18-22, 1990, New Orleans, La.), showed little difference in the efficacy or major side effect profile of these two agents. (Elements of the trial's design, however, have been subjected to criticism.) Other plasminogen activators studied clinically include the human proteins urokinase and its zymogen, single-chain urokinase-type plasminogen