Differential inhibition of human atherosclerotic plaque-induced platelet activation by dimeric GPVI-Fc and anti-GPVI antibodies: functional and imaging studies

Abstract

BACKGROUND Glycoprotein VI (GPVI) is the essential platelet collagen receptor in atherothrombosis, but its inhibition causes only a mild bleeding tendency. Thus, targeting this receptor has selective antithrombotic potential.

OBJECTIVES We compared compounds interfering with platelet PVI-atherosclerotic plaque interaction to improve current antiatherothrombotic therapy.

METHODS Human atherosclerotic plaque-induced platelet aggregation was measured in anticoagulated blood under static and arterial flow conditions (550/s, 1,100/s, and 1,500/s). Inhibition by dimeric GPVI-Fc masking GPVI binding sites on collagen was compared with that of 3 anti-GPVI antibodies: BLO8-1, a human domain antibody; 5C4, a fragment antigen-binding (Fab fragment) of monoclonal rat immunoglobulin G; and m-Fab-F, a human recombinant sFab against GPVI dimers.

RESULTS GPVI-Fc reduced plaque-triggered platelet aggregation in static blood by 51%, BLO8-1 by 88%, and 5C4 by 93%. Under arterial flow conditions BLO8-1 and 5C4 almost completely inhibited platelet aggregation, while preserving platelet adhesion on plaque. Inhibition by GPVI-Fc, even at high concentrations, was less marked but increased with shear rate. Advanced optical imaging revealed rapid persistent GPVI-Fc binding to collagen under low and high shear flow, upstream and downstream of plaque fragments. Particularly at low shear, platelets adhered in plaque flow niches to GPVI-Fc free segments of collagen fibers and recruited other platelets onto aggregates.

CONCLUSIONS Anti-GPVI antibodies inhibit atherosclerotic plaque-induced platelet aggregation under static and flow conditions more effectively than GPVI-Fc. However, potent platelet inhibition by GPVI-Fc at higher shear (1,500/s) suggests localized antithrombotic efficacy at denuded or fissured stenotic high-risk lesions without systemic bleeding. The compound-specific differences have relevance for clinical trials targeting GPVI-collagen interaction on top of established antiplatelet therapies in patients with spontaneous plaque rupture or intervention-associated plaque injury.