Hirudins: from leeches to man.

Hirudins are a group of highly homologous polypeptides from the medicinal leech, Hirudo medicinalis. They have an extremely high and specific affinity for thrombin and are consequently potent anticoagulants. They inhibit platelet aggregation induced by thrombin and efficiently inhibit thrombin when it is bound to a fibrin clot. Recombinant hirudins have now been produced and have been used to show a wide range of effects on thrombosis in animal models. They are particularly effective against venous-type thrombi and have greater effects than heparins on the platelet-rich thrombi in arteries. Recombinant hirudins are currently undergoing clinical trails in deep venous thrombosis and acute coronary syndrome and as an adjunct to thrombolysis in myocardial infarction. Results from pilot trials indicate promising advantages over the currently used antithrombotic agents. Larger clinical trails have been initiated and we await with great interest their imminent publication.