title: Anticoagulant characteristics of HD1-22, a bivalent aptamer that specifically inhibits thrombin and prothrombinase.
abstract: BACKGROUND
  HD1-22 is a bivalent aptamer that binds to thrombin with high affinity (K(d) = 0.65 nm) and occupies both anion binding exosites without blocking the active centre of the enzyme. HD1-22 has been developed by connecting the exosite 1 binding aptamer HD1 and the exosite 2 binding aptamer HD22 through a poly-dA linker.
  
  
  OBJECTIVE
  To characterize the anticoagulant profile of HD1-22 in comparison to the clinically established direct acting thrombin inhibitors bivalirudin and argatroban, and to test the efficacy of antidote-oligodeoxynucleotides.
  
  
  RESULTS
  HD1-22 prolongs clotting times of the thrombin time, activated partial thromboplastin time, ecarin clotting time, and lag-time of the tissue factor triggered thrombin generation assay in a dose-dependent manner. On a molar basis, its anticoagulant activity was nearly identical to bivalirudin and superior to argatroban. Thrombin-induced platelet aggregation was more effectively inhibited by HD1-22 than by bivalirudin. The HD1-22 aptamer retains the ability of the HD1-moiety to bind to (pro)exosite 1 of prothrombin and inhibits the prothrombinase activity nearly 2-fold better than HD1. The anticoagulant activities of HD1-22 are fully reversed by addition of antidote-oligodeoxynucleotides.
  
  
  CONCLUSIONS
  The strong thrombin-inhibiting activity, together with the availability of a rapid acting antidote strategy, makes HD1-22 an interesting anticoagulant candidate, especially for use in clinical situations where effective anticoagulation and rapid reversal of the anticoagulant effect are required. The data obtained warrant further clinical studies.
authors.affiliation: Institute for Experimental Haematology and Transfusion Medicine, University Hospital Bonn, Germany.
authors.forename: J
authors.initials: J
authors.lastname: Müller
authors.forename: D
authors.initials: D
authors.lastname: Freitag
authors.forename: G
authors.initials: G
authors.lastname: Mayer
authors.forename: B
authors.initials: B
authors.lastname: Pötzsch
mesh_terms: D000925:Anticoagulants / Q000494:pharmacology*; D052157:Aptamers, Nucleotide / Q000494:pharmacology* / Q000627:therapeutic use; D001777:Blood Coagulation / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D006801:Humans; D010974:Platelet Aggregation / Q000187:drug effects; D013917:Thrombin / Q000037:antagonists & inhibitors*; D013925:Thromboplastin / Q000037:antagonists & inhibitors*
chemical_list: D000925:Anticoagulants; D052157:Aptamers, Nucleotide; D013925:Thromboplastin; D013917:Thrombin