Pharmacological Inhibition of Glycoprotein VI- and Integrin α2β1-Induced Thrombus Formation Modulated by the Collagen Type

Background In secondary cardiovascular disease prevention, treatments blocking platelet-derived secondary mediators pose a risk of bleeding. Pharmacological inter-ference of the interaction of platelets with exposed vascular collagens is an attractive alternative, with clinical trials ongoing. Antagonists of the collagen receptors, glyco-protein VI (GPVI), and integrin alpha 2131, include recombinant GPVI-Fc dimer construct Revacept, 9O12 mAb based on the GPVI-blocking reagent Glenzocimab, Syk tyrosine-kinase inhibitor PRT-060318, and anti-alpha 2131 mAb 6F1. No direct comparison has been made of the antithrombic potential of these drugs.Methods Using a multiparameter whole-blood microfluidic assay, we compared the effects of Revacept, 9O12-Fab, PRT-060318, or 6F1 mAb intervention with vascular collagens and collagen-related substrates with varying dependencies on GPVI and alpha 2131. To inform on Revacept binding to collagen, we used fluorescent-labelled anti-GPVI nanobody-28.Results and Conclusion In this first comparison of four inhibitors of platelet-collagen interactions with antithrombotic potential, we find that at arterial shear rate: (1) the thrombus-inhibiting effect of Revacept was restricted to highly GPVI-activating surfaces; (2) 9O12-Fab consistently but partly inhibited thrombus size on all surfaces; (3) effects of GPVI-directed interventions were surpassed by Syk inhibition; and (4) alpha 2131-directed intervention with 6F1 mAb was strongest for collagens where Revacept and 9O12-Fab were limitedly effective. Our data hence reveal a distinct pharma-cological profile for GPVI-bind ing competition (Revacept), GPVI receptor blockage (9O12-Fab), GPVI signaling (PRT-060318), and alpha 2 beta 1 blockage (6F1 mAb) in flow dependent thrombus formation, depending on the platelet-activating potential of the collagen substrate. This work thus points to additive antithrombotic action mechanisms of the investigated drugs.