A novel inhibitor of plasminogen activator inhibitor-1 provides antithrombotic benefits devoid of bleeding effect in nonhuman primates

Abstract

Inhibition of plasminogen activator inhibitor (PAI)-1 is useful to treat several disorders including thrombosis. An inhibitor of PAI-1 (TM5275) was newly identified by an extensive study of structure-activity relationship based on a lead compound (TM5007) which was obtained through virtual screening by docking simulations. Its antithrombotic efficacy and adverse effects were tested in vivo in rats and nonhuman primates (cynomolgus monkey). TM5275, administered orally in rats (1 to 10 mg/kg), has an antithrombotic effect equivalent to that of ticlopidine (500 mg/kg) in an arterial venous shunt thrombosis model and to that of clopidogrel (3 mg/kg) in a ferric chloride-treated carotid artery thrombosis model. TM5275 does not modify activated partial thromboplastin time and prothrombin time or platelet activity and does not prolong bleeding time. Combined with tissue plasminogen activator, TM5275 improves the latter's therapeutic efficacy and reduces its adverse effect. Administered to a monkey model of photochemical induced arterial thrombosis, TM5275 (10 mg/kg) has the same antithrombotic effect as clopidogrel (10 mg/kg), without enhanced bleeding. This study documents the antithrombotic benefits of a novel, more powerful, PAI-1 inhibitor in rats and, for the first time, in nonhuman primates. These effects are obtained without adverse effect on bleeding time.

Figure 1

Chemical structures of TM5007 (A) and TM5275 (B). Molecular weights for TM5007 and TM5275 are 560.02 and 543.97, respectively. On SDS-PAGE (C), PAI-1 formed a covalent complex with tPA, whereas no PAI-1/tPA complex formation was observed when PAI-1 was preincubated with TM5275.

Figure 2

The binding modes of TM5007 (cyan) and TM5275 (pink) obtained by docking simulations are shown. Figures were drawn by a software PyMOL version 0.97 (DeLano Scientific LLC, San Carlo, CA, USA).

Figure 3

Effects of TM5275 and clopidogrel on primary occlusion time (open circles) and bleeding time (closed circles) in the rat FeCl₃-induced thrombosis model. ^*P<0.05, ^†P<0.01, ^‡P<0.001 versus vehicle. n=8, each group.

Figure 4

Effect of combination of TM5275 and tPA on primary occlusion time (left panel) and bleeding time (right panel) in the rat FeCl₃-induced thrombosis model. ^*P<0.05, ^†P<0.01, ^‡P<0.001 versus vehicle, ^§P<0.05 versus tPA (0.3 mg/kg) alone. n=10, each group.