A Faster-Acting and More Potent Form of Tissue Plasminogen Activator

• Published in: Proceedings of the National Academy of Sciences - PNAS 1994-04, Vol.91 (9), p.3670-3674
• Main Authors: Keyt, Bruce A., Paoni, Nicholas F., Refino, Canio J., Berleau, Lea, Nguyen, Hung, Chow, Alice, Lai, Jadine, Pena, Luis, Pater, Cheryl, Ogez, John, Etcheverry, Tina, Botstein, David, Bennett, William F.
• Format: Article
• Language: English
• Subjects: Animals; Biochemistry; Biological and medical sciences; Blood; Blood plasma; Blood. Blood coagulation. Reticuloendothelial system; Boluses; Fibrin - metabolism; Fibrinogen - metabolism; Fibrinolysis; Fibrinolytic Agents - chemistry; Fibrinolytic Agents - metabolism; Fibrinolytic Agents - pharmacokinetics; Fibrinolytics; Genetic mutation; Humans; Intravenous injections; Kinetics; Medical sciences; Molecules; Mutagenesis; Mutagenesis, Site-Directed; Pharmacokinetics; Pharmacology. Drug treatments; Rabbits; Structure-Activity Relationship; Tissue Plasminogen Activator - antagonists & inhibitors; Tissue Plasminogen Activator - chemistry; Tissue Plasminogen Activator - genetics; Tissue Plasminogen Activator - pharmacokinetics
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.91.9.3670

Current treatment with tissue plasminogen activator (tPA) requires an intravenous infusion (1.5-3 h) because the clearance of tPA from the circulation is rapid (t1/2≈ 6 min). We have developed a tPA variant, T103N,N117Q, KHRR(296-299)AAAA (TNK-tPA) that has substantially slower in vivo clearance (1.9 vs. 16.1 ml per min per kg for tPA in rabbits) and near-normal fibrin binding and plasma clot lysis activity (87% and 82% compared with wild-type tPA). TNK-tPA exhibits 80-fold higher resistance to plasminogen activator inhibitor 1 than tPA and 14-fold enhanced relative fibrin specificity. In vitro, TNK-tPA is 10-fold more effective at conserving fibrinogen in plasma compared to tPA. Arterial venous shunt models of fibrinolysis in rabbits indicate that TNK-tPA (by bolus) induces 50% lysis in one-third the time required by tPA (by infusion). TNK-tPA is 8- and 13-fold more potent in rabbits than tPA toward whole blood clots and platelet-enriched clots, respectively. TNK-tPA conserves fibrinogen and, because of its slower clearance and normal clot lysis activity, is effective as a thrombolytic agent when given as a bolus at a relatively low dose.