title: Heparin-triggered release of camouflaged tissue plasminogen activator for targeted thrombolysis.
abstract: A targetable, heparin-triggered release system for tissue plasminogen activator (tPA) was designed to prevent the excessive 'lytic' state associated with the current tPA therapy for acute thrombotic conditions, such as myocardial infarction (MI). The strategy is, upon target accumulation, to trigger tPA release from a prodrug construct by a usual heparin dose. A relatively inactive form of tPA was constructed by conjugating tPA with low-molecular weight heparin followed by complexation with albumin-protamine conjugate, termed 'camouflage'. The modified tPA was ~97% as active as native tPA. The prodrug construct of tPA significantly masked the enzymatic activity, which was fully recovered upon heparin addition. The camouflaged tPA was stable in human blood for at least 30min and was able to trigger enzyme activation in vitro at heparin level of 0.4U/mL. In vivo studies on jugular vein rat thrombosis model showed that the clot lysis of the heparin-triggered camouflaged tPA group was equivalent to the tPA+heparin group without prolongation of activated partial thromboplastin time (aPTT) before and after the treatment. This proof-of-principle study suggests that the activity of the tPA prodrug construct can be triggered at the thrombus site at therapeutic heparin concentration conjunctively used for MI with reduced bleeding risk.
authors.affiliation: School of Pharmacy, Texas Tech University Health Sciences Center, 1300 Coulter St., Amarillo, TX 79106, USA.
authors.forename: Shahriar
authors.initials: S
authors.lastname: Absar
authors.forename: Suna
authors.initials: S
authors.lastname: Choi
authors.forename: Victor C
authors.initials: VC
authors.lastname: Yang
authors.forename: Young M
authors.initials: YM
authors.lastname: Kwon
mesh_terms: D000818:Animals; D003692:Delayed-Action Preparations / Q000008:administration & dosage / Q000138:chemical synthesis; D016503:Drug Delivery Systems / Q000379:methods*; D006493:Heparin / Q000008:administration & dosage* / Q000097:blood / Q000138:chemical synthesis; D006801:Humans; D051381:Rats; D015912:Thrombolytic Therapy / Q000379:methods*; D010959:Tissue Plasminogen Activator / Q000008:administration & dosage* / Q000097:blood / Q000138:chemical synthesis; D020246:Venous Thrombosis / Q000097:blood / Q000188:drug therapy*
chemical_list: D003692:Delayed-Action Preparations; D006493:Heparin; D010959:Tissue Plasminogen Activator