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The effects of the new anti-platelet agent KBT-3022, ethyl 2-[4,5-bis(4-methoxyphenyl)-thiazol-2-yl]pyrrol-1-ylacetate, and its metabolite desethyl KBT-3022 on rabbit neutrophil function were investigated in comparison with the effects of acetylsalicylic acid (ASA), ticlopidine hydrochloride (TP), cilostazol (CIL) and indomethacin (IM). The adhesion and migration of neutrophils induced by formyl-methionyl-leucyl-phenylalanine (fMLP) were inhibited by all the compounds tested, their rank order of potency being KBT-3022 = desethyl KBT-3022 > TP = CIL = IM > ASA. KBT-3022, desethyl KBT-3022, CIL and IM all suppressed fMLP-induced increases in the intracellular free Ca2+ concentration ([Ca2+]i) in neutrophils, their potencies correlating with their inhibitory effects on fMLP-induced adhesion and migration. KBT-3022 (1 microM), desethyl KBT-3022 (1-10 microM) and CIL (10 microM) but not IM significantly inhibited both neutrophil migration and the increase in [Ca2+]i induced by leukotriene B4 (LTB4). KBT-3022 (1 microM) and desethyl KBT-3022 (1 microM) suppressed the increase in [Ca2+]i induced by complement C5a. Although KBT-3022 and desethyl KBT-3022 did not influence [3H]LTB4 and [125I]C5a specific binding, [3H]fMLP specific binding was inhibited by desethyl KBT-3022 (IC50: 1.9 microM). Neutrophil adhesion and superoxide anion production stimulated by phorbol 12-myristate 13-acetate were partially inhibited by KBT-3022 (1 microM) and desethyl KBT-3022 (1-10 microM). These results suggest that KBT-3022 and desethyl KBT-3022 have a wider spectrum of action and are more potent inhibitors of neutrophil activation than ASA, TP, CIL and IM.

The protective effect of KBT-3022 (ethyl 2-[4,5-bis-(4-methoxyphenyl)thiazol-2-yl]pyrrol-1-ylacetate), a new cyclooxygenase inhibitor, in cerebral hypoxia and ischemia was studied and compared with those of indomethacin and acetylsalicylic acid (ASA). Oral administration of KBT-3022 (3-100 mg/kg) and indomethacin (3 and 10 mg/kg) significantly prevented KCN-induced death in mice, while ASA (100mg/kg) had no effect. KBT-3022 (3 and 10 mg/kg, p.o.) and indomethacin (10 mg/kg, p.o.) significantly prolonged the survival time of mice subjected to normobaric hypoxia, while ASA (100 mg/kg, p.o.) had no effect. KBT-3022 (3-30 mg/kg, p.o.) and indomethacin (3 mg/kg, i.p.) significantly ameliorated delayed neuronal death in the gerbil hippocampal CA1 sector after occlusion of bilateral carotid arteries for 5 min, while ASA (300 mg/kg, p.o.) had no effect. KBT-3022 (10 mg/kg, p.o.) significantly inhibited ATP depletion in the gerbil hippocampus after a 1-min occlusion of bilateral carotid arteries, but had no effect on ATP depletion after a 5-min occlusion and the recovery during recirculation. These results show that KBT-3022 exerts protective effects against cerebral anoxia and hypoxia and ameliorates delayed neuronal death in the hippocampus. KBT-3022 may therefore be useful for prophylaxis of ischemic cerebrovascular disorders.

In this study, we investigated the effects of KBT-3022 (ethyl 2-[4,5-bis(4-methoxyphenyl)-thiazol-2-yl]pyrrol-1-ylacetate), a potent and long-lasting anti-platelet agent, in several experimental thrombosis models and compared them with those of other anti-platelet drugs. Oral administration of KBT-3022 prevented arachidonic acid-induced death due to pulmonary embolism in mice and rabbits with respective ED50 values of 0.29 and 0.12 mg/kg. The protective effect of acetylsalicylic acid (ASA) against mortality was weaker than that of KBT-3022, and ticlopidine hydrochloride (TP) showed no such effect in these models. In a guinea pig arterio-venous shunt model, the inhibition by KBT-3022 of thrombus formation on a silk thread inserted into the shunt was dose-dependent and 300 and 30 times more potent than the inhibition obtained with ASA and indomethacin, respectively. In a model of aortic thrombosis induced by perivascular application of 20% silver nitrate solution, KBT-3022 (1 mg/kg, p.o.) inhibited thrombus formation significantly, ASA (100 mg/kg, p.o.) tended to inhibit it, and TP had no effect. However, in a stasis-induced venous thrombosis model in guinea pigs, TP inhibited thrombus formation significantly, but KBT-3022 and ASA were ineffective. These results suggest that KBT-3022 may be a useful drug for the treatment and/or prophylaxis of thrombus formation in shunts and aortic thrombosis.

We devised a method for evaluating polymorphonuclear leukocyte (PMN) infiltration in vivo employing an air bleb technique combined with measurement of myeloperoxidase (MPO) activity, and the effects of some anti-platelet agents were evaluated. KBT-3022 (ethyl 2-[4,5-bis (4-methoxyphenyl)thiazol-2-yl] pyrrol-1-ylacet ate) and cilostazol inhibited the increase in MPO activity in the connective tissue around the air bleb induced by leukotriene B4 (LTB4) and formyl-methionyl-leucyl-phenylalanine (fMLP). Indomethacin inhibited only the fMLP-induced increase in MPO activity, but ticlopidine hydrochloride and acetylsalicylic acid had no effect. Histologic observation confirmed the inhibition of PMN infiltration by KBT-3022. These results indicate that KBT-3022 may be a potent inhibitor of both LTB4- and fMLP-induced infiltration of PMNs.

FUT-175 inhibited the zymosan-induced rat paw edema in a dose-dependent manner, while indomethacin exhibited no significant activites in this model. FUT-175 also inhibited the decrease in hemolytic complement (CH50) induced by zymosan in vitro, and indomethacin was inactive. These results suggest that FUT-175 has potent in vitro and in vivo nhibitory activity against the activation of the complement system induced by zymosan.

FUT-175, 6-amidino-2-naphthyl p-guanidinobenzoate dimethanesulfonate (nafamstat mesilate), a novel synthetic protease-inhibiting agent, was studied to determine its in vitro effects against various proteases and other enzymes, as well as to determine its in vivo protease inhibitory effects. FUT-175 was found to inhibit, in an intense, specific and reversible way, the enzyme activities of trypsin, C1r, C1s, thrombin, kallikrein and plasmin with IC50 values of the order of 10(-6)-10(-8) M. FUT-175 also inhibited complement-mediated hemolysis, including both classical and alternative pathways, sites of inhibition being on C1r and C1s as evidenced by the intermediate-cell technique. In animal model reactions in which the complement system is known to be involved as pathogenetic factors, e.g., Forssman shock, Forssman cutaneous vasculitis, zymosan-induced paw edema, endotoxin shock and local Shwartzman reaction, FUT-175 was highly effective in that, for example, intravenous dosing at 3 mg/kg could completely protect guinea pigs from the lethal Forssman shock. FUT-175 was also found to be effective in trypsin-induced shock in mice, in lethality due to thrombin-thrombosis in mice and in kinin formation in the inflammatory process in rats.

FUT-175 has been reported by S.Fujii et al.1) to inhibit strongly Clr, Cls, trypsin and thrombin as well as kallikrein and plasmin. In the present study, effects of FUT-175 on the complement and kallikrein system were investigated in vitro and in vivo. The in vitro complement-mediated hemolysis via classical pathway activation was performed as described by Mayer et al., and the systemic Forssman shock in guinea pigs was induced by the method of Glovsky et al. The in vitro kinin formation was performed with glass powder in rat plasma. The anti-inflammatory effects of FUT-175 were also studied on kaolin- and scald-induced edema of rat paws. FUT-175 markedly inhibited the complement-mediated hemolysis, the IC50 being 4.5 × 10−8 M, and protected the guinea pig from the systemic Forssman shock at doses of 0.3 - 3 mg/kg, i.v., in a dose-dependent manner. FUT-175 also inhibited the in vitro kinin formation with the IC50 of 1.1 × 10−7 M (glass powder) and reduced the kaolin- and scald-induced edema formation at doses of 30 - 300 mg/kg, p.o..