Enhancement of fibrinolysis by EF6265 [(S)-7-amino-2-[[[(R)-2-methyl-1-(3-phenylpropanoylamino)propyl]hydroxyphosphinoyl] methyl]heptanoic acid], a specific inhibitor of plasma carboxypeptidase B.
Plasma procarboxypeptidase B, also known as thrombin-activatable fibrinolysis inhibitor (TAFI), is converted by thrombin into the active enzyme, carboxypeptidase B (CPB)/activated TAFI. Plasma CPB down-regulates fibrinolysis by removing carboxy-terminal lysines, the ligands for plasminogen and tissue-type plasminogen activator (tPA), from partially degraded fibrin. To target thrombosis in a new way, we have identified and optimized a phosphinic acid-containing inhibitor of CPB, EF6265 [(S)-7-amino-2-[[[(R)-2-methyl-1-(3-phenylpropanoylamino) propyl]hydroxyphosphinoyl]methyl]heptanoic acid] and determined both the pharmacological profile and pathophysiological role of CPB in rat thrombolysis. EF6265 specifically inhibited plasma CPB activity with an IC(50) (50% inhibitory concentration) of 8.3 nM and enhanced tPA-mediated clot lysis in a concentration-dependent manner. EF6265 decreased detectable thrombi (percentage of glomerular fibrin deposition; control, 98 +/- 1.1; EF6265, 0.1 mg/kg, 27 +/- 9.1) that had been generated by tissue factor in a rat microthrombosis model with concomitant increases in plasma D-dimer concentration (control, <0.5 microg/ml; EF6265, 0.1 mg/kg, 15 +/- 3.5 microg/ml). EF6265 reduced plasma alpha2-antiplasmin activity to a lesser extent than tPA. In an arteriovenous shunt model, EF6265 (1 mg/kg) enhanced exogenous tPA-mediated thrombolysis under the same conditions that neither EF6265 nor tPA (600 kIU/kg) alone reduced thrombi. EF6265 (1 and 30 mg/kg) did not affect the bleeding time in rats. Moreover, it did not prolong the bleeding time evoked by tPA (600 kIU/kg). These results confirm that circulating procarboxypeptidase B functions as a fibrinolysis inhibitor's zymogen and validates the use of CPB inhibitors as both an enhancer of physiological fibrinolysis in microcirculation and as a novel adjunctive agent to tPA for thromboembolic diseases while maintaining a small effect on primary hemostasis.
Suzuki
Kokichi
K
Pharmaceutical Research Center, Meiji Seika Kaisha, Ltd., Yokohama, Japan. kokichi_suzuki@meiji.co.jp
Muto
Yuko
Y
Fushihara
Kenichi
K
Kanemoto
Ken-ichi
K
Iida
Hiroyuki
H
Sato
Eriko
E
Kikuchi
Chika
C
Matsushima
Tetsuya
T
Kato
Emiko
E
Nomoto
Masahiro
M
Yoshioka
Shin
S
Ishii
Hidemi
H
D000596:Amino Acids / Q000493:pharmacokinetics / Q000494:pharmacology* / Q000627:therapeutic use; D000818:Animals; D001166:Arteriovenous Shunt, Surgical; D001760:Bleeding Time; D025901:Carboxypeptidase B2 / Q000037:antagonists & inhibitors* / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000493:pharmacokinetics / Q000494:pharmacology* / Q000627:therapeutic use; D005342:Fibrinolysis / Q000187:drug effects*; D006801:Humans; D007275:Injections, Intravenous; D008297:Male; D008954:Models, Biological; D010721:Phosphinic Acids / Q000493:pharmacokinetics / Q000494:pharmacology* / Q000627:therapeutic use; D051381:Rats; D017208:Rats, Wistar; D013925:Thromboplastin; D013927:Thrombosis / Q000139:chemically induced / Q000188:drug therapy
C487111:7-amino-2-(((2-methyl-1-(3-phenylpropanoylamino)propyl)hydroxyphosphinoyl)methyl)heptanoic acid; D000596:Amino Acids; D004791:Enzyme Inhibitors; D010721:Phosphinic Acids; D013925:Thromboplastin; D025901:Carboxypeptidase B2