title: In vitro antiplatelet profile of FR171113, a novel non-peptide thrombin receptor antagonist.
abstract: Synthetic peptides (5 to 14 amino acids), identical in sequence to the new amino-terminus of the thrombin receptor generated following cleavage by thrombin, act as thrombin receptor agonist peptides. Whilst thrombin receptor antagonist peptides are known, non-peptide thrombin receptor antagonists have yet to be described. In the present study, we compared the antiplatelet effects of 3-(4-chlorophenyl)-2-(2,4-dichlorobenzoylimino)-5-(methoxycarbonyl methylene)-1,3-thiazolidin-4-one (FR171113), a novel non-peptide thrombin receptor antagonist, with the known thrombin receptor antagonist 3-mercapto-propionyl-Phe-Cha-Cha-Arg-Asn-Pro-Asn-Asp-Lys-Tyr-OH (C186-65), and argatroban, a specific protease inhibitor of thrombin. FR171113 and C186-65 inhibited thrombin-induced platelet aggregation (IC(50)=0.29 microM and 15 microM, respectively) and Ser-Phe-Leu-Leu-Arg-Asn-NH(2) [a synthetic thrombin receptor agonist peptide (TRAP-6)] induced platelet aggregation (0.15 microM and 20 microM, respectively) in human washed platelets. Argatroban potently inhibited thrombin-induced platelet aggregation (IC(50)=3.5 nM), but did not inhibit TRAP-6-induced aggregation even at 100 microM. In contrast, these compounds did not show inhibitory effects on ADP- and collagen-induced aggregation in human platelet-rich plasma even at 100 microM. FR171113 caused a parallel shift to the right of the concentration-response curve describing aggregation induced by TRAP-6. The Schild plot of the data had a slope of -0.840 (r=0.98) and the pA(2) was 7.29. In protease activity studies using a chromogenic substrate, argatroban inhibited thrombin protease activity in a dose-dependent manner, whereas FR171113 and C186-65 were inactive, even at 100 microM. Additionally, only argatroban displayed dose-dependent prolongation of thrombin time, activated partial thromboplastin time and prothrombin time. FR171113 and C186-65 showed no effects, even at a concentration of 100 microM. These results suggest that FR171113 has a similar mode of action to C186-65, but with more potent antiplatelet activity. In conclusion, FR171113 is suggested to be the first example of a non-peptide thrombin receptor antagonist.
authors.affiliation: Medicinal Biology Research Laboratories, Fujisawa Pharmaceutical, 1-6, 2-chome, Kashima, Yodogawa-ku, Osaka, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Kato
authors.forename: Y
authors.initials: Y
authors.lastname: Kita
authors.forename: M
authors.initials: M
authors.lastname: Nishio
authors.forename: Y
authors.initials: Y
authors.lastname: Hirasawa
authors.forename: K
authors.initials: K
authors.lastname: Ito
authors.forename: T
authors.initials: T
authors.lastname: Yamanaka
authors.forename: Y
authors.initials: Y
authors.lastname: Motoyama
authors.forename: J
authors.initials: J
authors.lastname: Seki
mesh_terms: D001120:Arginine / Q000031:analogs & derivatives; D001241:Aspirin / Q000494:pharmacology; D001549:Benzamides / Q000494:pharmacology*; D004151:Dipeptides / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D006801:Humans; D009842:Oligopeptides / Q000494:pharmacology; D010446:Peptide Fragments / Q000494:pharmacology; D010875:Pipecolic Acids / Q000494:pharmacology; D010974:Platelet Aggregation / Q000187:drug effects; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology*; D018179:Receptors, Thrombin / Q000037:antagonists & inhibitors*; D012697:Serine Endopeptidases / Q000378:metabolism; D013449:Sulfonamides; D013844:Thiazoles / Q000494:pharmacology*; D053778:Thiazolidines; D013917:Thrombin / Q000378:metabolism / Q000494:pharmacology
chemical_list: D001549:Benzamides; C090291:C186 65; D004151:Dipeptides; C403255:FR 171113; D009842:Oligopeptides; D010446:Peptide Fragments; D010875:Pipecolic Acids; D010975:Platelet Aggregation Inhibitors; D018179:Receptors, Thrombin; D013449:Sulfonamides; D013844:Thiazoles; D053778:Thiazolidines; C082835:thrombin receptor peptide (42-47); C021129:S 2238; D001120:Arginine; C046617:arginyl-glycyl-aspartyl-serine; D012697:Serine Endopeptidases; D013917:Thrombin; C031942:argatroban; D001241:Aspirin