Antithrombotic effect of SP-8008, a benzoic acid derivative, through the selective inhibition of shear stress-induced platelet aggregation.

Background and Purpose Bleeding is one of the most critical adverse effects of antithrombotic drugs, and many efforts have been made to discover novel antiplatelet agents without bleeding complications. Shear stress-induced platelet aggregation (SIPA), where the interaction of von Willebrand factor (vWF) and platelet glycoprotein (GP) Ib constitutes the initial step, is a promising target to overcome bleeding problems, as SIPA occurs only in pathological conditions. Here, we describe SP-8008, a novel modulator of vWF-GP Ib interactions and evaluated its antiplatelet/antithrombotic effects. Experimental Approach Newly synthesized compounds were screened for antiplatelet effects in vitro, using human platelets exposed to high shear stress. Aggregation, intracellular calcium level, granule secretion, and integrin activation were assessed. Molecular modelling using virtual docking and flow cytometry were used to evaluate effects on vWF-GP Ib interactions. Antithrombotic effects in vivo were determined in rats, using arterial thrombosis and shear stress-specific thrombosis. Transection tail bleeding time was used to evaluate adverse effects. Key Results SP-8008 was a potent inhibitor of SIPA, with IC50 of 1.44 +/- 0.09 mu M. SP-8008 effectively and broadly blocked shear stress-induced platelet activation events, without any significant toxicity. Importantly, SP-8008 was highly selective against SIPA, effectively interfering with vWF-GP Ib engagement. Most importantly, SP-8008 exerted significant antithrombotic effects in vivo in both shear stress-specific and arterial thrombosis, without prolonging bleeding time. Conclusions and Implications Our results demonstrated that SP-8008 can be a novel selective antiplatelet agent with improved safety profile.