The integrin antagonist, cilengitide, is a weak inhibitor of αIIbβ3 mediated platelet activation and inhibits platelet adhesion under flow

Abstract

The RGD cyclic pentapetide, cilengitide, is a selective inhibitor of αvβ3 and αvβ5 integrins and was developed for antiangiogenic therapy. Since cilengitide interacts with platelet αIIbβ3 and platelets express αv integrins, the effect of cilengitide on platelet pro-coagulative response and adhesion is of interest. Flow-based adhesion assays were performed to evaluate platelet adhesion and rolling on von Willebrand factor (vWf), on fibrinogen and on human umbilical vein endothelial cells (HUVECs). Flow cytometry was used to detect platelet activation (PAC1) and secretion (CD62P) by cilengitide and light transmission aggregometry was used to detect cilengitide-dependent platelet aggregation. Cilengitide inhibited platelet adhesion to fibrinogen at concentrations above 250 µM [which is the C_max in human studies] and adhesion to vWf and HUVECs at higher concentrations under physiologic flow conditions. Platelet aggregation was already impaired at cilengitide concentrations >10 µM. Activation of αIIbβ3 integrin was inhibited by 250 µM cilengitide, whereas platelet secretion was unaffected by cilengitide. No evidence of cilengitide-induced platelet activation was found at all tested concentrations (0.01–1500 µM). At higher concentrations, platelet activation was inhibited, predominantly due to αIIbβ3 inhibition.

• Alpha-v beta-3 Integrin
• angiogenesis inhibitors
• cilengitide
• platelet membrane glycoproteins receptors
• thrombosis

Acknowledgements

The authors thank Simon Goodman for helpful hints, fruitful discussion and continuous support of the project.

Declaration of interest

This study has been supported by a grant from Merck KGaA. SH has received scientific grants from Merck KGaA and The Medicines Company and has received honoraria for lectures from Merck KGaA and LEO Pharmaceuticals. UK is employed by Merck KGaA. All other authors have no disclosures.