Prevention of arterial thrombosis using a novel heparin with enhanced antiplatelet activity and reduced anticoagulant activity.

PURPOSE: Thrombosis after arterial injury is often initiated by von Willebrand factor (vWF)-dependent platelet accumulation. A promising antithrombotic strategy is the interruption of platelet/vWF interactions. Previously, we demonstrated how chemical and affinity modification can enhance heparin's anti-vWF activity while reducing conventional anticoagulation. Here, we investigated whether a modified heparin can block platelet-dominated arterial thrombosis. METHODS: Standard heparin was oxidized with periodate, refined to have high vWF affinity and inhibitory potency, and tested in a guinea pig model of platelet-dependent arterial thrombosis. In this model, a controlled mechanical arterial injury yields cyclic flow variations (CFVs) caused by recurrent accumulation of platelet thrombi. RESULTS: All six control animals developed CFVs (mean, 10.4 +/- 2.6 CFVs), and six of seven animals treated with standard heparin also developed CFVs (mean, 7.6 +/- 4.6). Only one of six animals treated with the anti-vWF heparin and one of six treated with AJvW-2 (an anti-vWF antibody) developed CFVs (mean, 2.0 +/- 4.9 and 0.5 +/- 1.2, respectively). Thus both the modified heparin and AJvW-2 were more effective than standard heparin (p < 0.03). Bleeding times and platelet counts were unaffected. A modified activated partial thromboplastin time was less prolonged by the modified high-affinity heparin (91 +/- 17) seconds) than by standard heparin (144 +/- 30 seconds; p < 0.01). CONCLUSIONS: The modified heparin with high vWF affinity was a more effective arterial antithrombotic agent, with fewer conventional anticoagulant effects than standard heparin. Interruption of the vWF/platelet interaction is a promising antithrombotic strategy that may be met by novel heparin-based antithrombotic drugs.