Synergistic inhibition of both P2Y₁ and P2Y₁₂ adenosine diphosphate receptors as novel approach to rapidly attenuate platelet-mediated thrombosis

Objective - Unlike currently approved adenosine diphosphate receptor antagonists, the new diadenosine tetraphosphate derivative GLS-409 targets not only P2Y₁₂ but also the second human platelet adenosine diphosphate receptor P2Y₁ and may, therefore, be a promising antiplatelet drug candidate. The current study is the first to investigate the in vivo antithrombotic effects of GLS-409. Approach and Results - We studied (1) the in vivo effects of GLS-409 on agonist-stimulated platelet aggregation in anesthetized rats, (2) the antithrombotic activity of GLS-409 and the associated effect on the bleeding time in a canine model of platelet-mediated coronary artery thrombosis, and (3) the inhibition of agonist-stimulated platelet aggregation by GLS-409 versus selective P2Y₁ and P2Y₁₂ inhibition in vitro in samples from healthy human subjects before and 2 hours after aspirin intake. In vivo treatment with GLS-409 significantly inhibited adenosine diphosphate- and collagen-stimulated platelet aggregation in rats. Further, GLS-409 attenuated cyclic flow variation, that is, platelet-mediated thrombosis, in vivo in our canine model of unstable angina. The improvement in coronary patency was accompanied by a nonsignificant 30% increase in bleeding time. Of note, GLS-409 exerted its effects without affecting rat and canine hemodynamics. Finally, in vitro treatment with GLS-409 showed effects similar to that of cangrelor and the combination of cangrelor with the selective P2Y₁ inhibitor MRS 2179 on agonist-stimulated platelet aggregation in human platelet-rich plasma and whole blood before and 2 hours after aspirin intake. Conclusions - Synergistic inhibition of both P2Y₁ and P2Y₁₂ adenosine diphosphate receptors by GLS-409 immediately attenuates platelet-mediated thrombosis and effectively blocks agonist-stimulated platelet aggregation irrespective of concomitant aspirin therapy.