The purpose of this study was to design and evaluate
hirudin (HIR) derivatives with low
bleeding risk. In these derivatives, the factor (F) XIa, FXa, and
thrombin recognition
peptides (EPR, GVYAR, and LGPR, respectively) were linked to the N-terminus of HIR. The intact derivatives have no
anticoagulant activity because of the extension of the N-terminus of HIR. After cleavage by the corresponding
coagulation factor that occurs on the activation of the coagulation system and in the presence of the
thrombus, its activity is released. This limited the
anticoagulant activity of these derivatives to the vicinity of the
thrombus, and as a result, systemic
bleeding complications were avoided. The definite antithrombotic effect and low
bleeding parameters of these derivatives were investigated in rat carotid artery and inferior vena cava
thrombosis models. In both models, the three derivatives showed significant antithrombotic effects, indicating that
anticoagulant activity could be successfully released in vivo. Moreover, the
bleeding parameters of these derivatives were lower than that of HIR as indicated by the values of activated partial thromboplastin time (APTT) and thrombin time (TT). To further assess the safety of these derivatives, bleeding time was measured in a mouse tail-cut model. Although the derivatives had obvious effects on
bleeding at a dose of 6 mg/kg, the effect of these derivatives on
bleeding was significantly weaker than that of HIR at a dose of 1.5 mg/kg. Thus, the benefit-to-risk profiles of the derivatives were superior to that of HIR.