Drug – bio-affecting and body treating compositions – Designated organic active ingredient containing – Peptide containing doai
Patent
1996-06-28
2000-10-03
Celsa, Bennett
Drug, bio-affecting and body treating compositions
Designated organic active ingredient containing
Peptide containing doai
514 14, 514 15, 514 16, 530326, 530327, 530328, 530329, A61K 3803, C07K 700
Patent
active
061273376
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
Thrombin plays a central role in the coagulation cascade of higher animals. The primary function of thrombin is to activate fibrinogen to fibrin and generate an insoluble fibrin clot. It also serves regulatory functions in coagulopathy by activating several participating cofactors and proteases such as factor V, factor VIII, factor XIII and protein C. In a pathologic state, thrombin promotes coagulopathy, activates platelets and causes secretion of granular substances that exacerbate the condition. Thrombin's interaction with endothelial cells, smooth muscle cells, fibroblasts, and monocytes/macrophages contribute further to the inflammatory process in thrombotic events. An acute blockage of a coronary artery by a thrombus causes a myocardial infarction. In its early stages, the condition may be alleviated with thrombolytic therapy. However, typical thrombolysis with tissue plasminogen activator, urokinase or streptokinase is problematic. Acute thrombotic reocclusion often occurs after initial successful thrombolysis using these agents. Although the mechanism of reocclusion has not been clearly elucidated, thrombus-bound thrombin may contribute to this problem. Potent and specific agents that neutralize thrombus-bound thrombin would be desirable.
Thrombin is a member of the trypsin family of serine proteases. In addition to the catalytic triad (Asp 102, His 57 and Ser 195) a feature common to the active site of all serine proteases, asp 189 in the primary substrate binding site (S1) of the trypsin family plays an important role in the recognition and binding of substrates and inhibitors.
A natural anticoagulant, heparin inhibits thrombin through a mechanism requiring a heparin-antithrombin III compounds. Heparin is known to be poorly accessible to thrombus-bound thrombin. Furthermore, heparin often causes bleeding when used therapeutically and is unable to prevent the occlusive complications in atherosclerotic vascular diseases or reocclusion following successful thrombolysis.
Another agent known to be effective for the inhibition of thrombus-bound thrombin is hirudin. Hirudin is produced by the salivary glands of the European medicinal leech Hirudo medicinalis and is a small protein of 65 amino acid residues. It has several potential advantages over other antithrombotics. It is the most potent and specific thrombin inhibitor known having a K.sub.i value of 2.2.times.10.sup.-14 M. Hirudin blocks the active site (AS) and the fibrinogen recognition exosite (FRE) of thrombin simultaneously. Hirudin also inhibits thrombus-bound thrombin as well as circulating thrombin and it has a long half-life of 30-60 minutes when given intravenously or subcutaneously, depending on the species. Hirudin has very weak antigenicity, and it has no reported acute side effects following intravenous or subcutaneous administration.
Synthetic thrombin inhibitors based on the hirudin sequence offer an advantage over native hirudin. They mimic the distinctive mechanism of hirudin and are more readily available through chemical synthesis. The crystal structure of the human a-thrombin/hirudin complex reveals that hirudin interacts with the enzyme through an active site inhibitor domain (hirudin.sup.1-48), a FRE inhibitor segment (hirudin.sup.55-65), and a linker segment (hirudin.sup.49-54) which connects these binding components.
The bulky active site inhibitor segment, hirudin .sup.1-48, is sufficiently large and serves to obstruct the enzyme surface. This action has been shown to be simulated when hirudin .sup.1-48 is replaced by a small active site inhibitor segment, D-Phe-Pro-Arg-Pro, with some loss in inhibitory potency (Maraganore, J. M., Bourdon, P., Jablonsky, J., Ramachandran, K. L., & Fenton, J. W. 11 (1990) Biochemistry 29, 7095-7101; DiMaio, J., Gibbs, B., Munn, D., Lefebvre, J. Ni, F., and Konishi, Y., (1990) J.Biol.Chem 265, 21698-21703; Bourdon, P., Jablonski, J. -A., Chao, B. H., and Maraganore, J. M., 9, (1991) (FEBS Lett. 294, 163-166).
Investigators have focused on the use of D-Phe-Pro-Arg
REFERENCES:
patent: 3978045 (1976-08-01), Okamoto et al.
patent: 4173630 (1979-11-01), Okamoto et al.
patent: 5196404 (1993-03-01), Maraganore et al.
Brandstetter et al., J. Mol. Biol. (1992) 226 1085-99.
Szewczuk et al. Biochem (1993) 32 3396-3404.
Krstenansky et al., Titromb. & Hafm. 63(2) 208-14 (1990).
Konishi Yasuo
Szewczuk Zbigniew
Tsuda Yuko
Anderson J. Wayne
Celsa Bennett
National Research Council of Canada
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