Biochemical and pharmacological effects of the direct thrombin inhibitor AR-H067637.
AZD0837 is in development as a new oral anticoagulant for use in thromboembolic disorders. In vivo, AZD0837 is converted to AR-H067637, a selective and reversible direct thrombin inhibitor. Established biochemical methods were used to assess and measure the biochemical and pharmacological properties of AR-H067637. Both direct Biacore binding studies of AR-H067637 with immobilised alpha-thrombin and inhibition studies using pre-steady state kinetics with thrombin in the fluid phase confirmed that AR-H067637 is a rapid-binding, reversible and potent (inhibition constant K(i) = 2-4 nM), competitive inhibitor of thrombin, as well as of thrombin bound to fibrin (clot-bound thrombin) or to thrombomodulin. The total amount of free thrombin generated in platelet-poor clotting plasma was inhibited concentration-dependently by AR-H067637, with a concentration giving half maximal inhibition (IC(50)) of 0.6 microM. Moreover, AR-H067637 is, with the exception of trypsin, a selective inhibitor for thrombin without inhibiting other serine proteases involved in haemostasis. Furthermore, no anticoagulant effect of the prodrug was found. AR-H067637 prolonged the clotting time concentration-dependently in a range of plasma coagulation assays including activated partial thromboplastin time, prothrombin time, prothrombinase-induced clotting time, thrombin time and ecarin clotting time. The two latter assays were found to be most sensitive for assessing the anticoagulant effect of AR-H067637 (plasma IC(50) 93 and 220 nM, respectively). AR-H067637 also inhibited thrombin-induced platelet activation (by glycoprotein IIb/IIIa exposure, IC(50) 8.4 nM) and aggregation (IC(50) 0.9 nM). In conclusion, AR-H067637 is a selective, reversible, competitive inhibitor of alpha-thrombin, with a predictable anticoagulant effect demonstrated in plasma coagulation assays.
Deinum
Johanna
J
AstraZeneca R&D, Bioscience, SE 431 83 Mölndal, Sweden. Johanna.Deinum@astrazeneca.com
Mattsson
Christer
C
Inghardt
Tord
T
Elg
Margareta
M
D000578:Amidines / Q000493:pharmacokinetics / Q000494:pharmacology; D000925:Anticoagulants / Q000494:pharmacology*; D001384:Azetidines / Q000493:pharmacokinetics / Q000494:pharmacology; D001667:Binding, Competitive; D001777:Blood Coagulation / Q000187:drug effects*; D001779:Blood Coagulation Factors / Q000378:metabolism; D001792:Blood Platelets / Q000201:enzymology*; D004305:Dose-Response Relationship, Drug; D004353:Drug Evaluation, Preclinical; D005260:Female; D006801:Humans; D020128:Inhibitory Concentration 50; D008297:Male; D015539:Platelet Activation / Q000187:drug effects*; D011485:Protein Binding; D013917:Thrombin / Q000037:antagonists & inhibitors*; D014914:Whole Blood Coagulation Time
C552153:AR-H067637; C551586:AZD 0837; D000578:Amidines; D000925:Anticoagulants; D001384:Azetidines; D001779:Blood Coagulation Factors; D013917:Thrombin