title: Anfibatide, a novel GPIb complex antagonist, inhibits platelet adhesion and thrombus formation in vitro and in vivo in murine models of thrombosis.
abstract: Platelet adhesion and aggregation at the sites of vascular injury are key events for thrombosis and haemostasis. It has been well demonstrated that interaction between glycoprotein (GP) Ibα and von Willebrand factor (VWF) initiates platelet adhesion and contributes to platelet aggregation, particularly at high shear. GPIb has long been suggested as a desirable antithrombotic target, but anti-GPIb therapy has never been successfully developed. Here, we evaluated the antithrombotic potential of Anfibatide, a novel snake venom-derived GPIb antagonist.We found Anfibatide inhibited washed murine platelet aggregation induced by ristocetin and recombinant murine VWF. It also blocked botrocetin-induced binding of murine plasma VWF to recombinant human GPIbα. Interestingly, Anfibatide did not inhibit botrocetin-induced aggregation of platelet-rich plasma, indicating that its binding site may differ from other snake venom-derived GPIb antagonists. Anfibatide strongly inhibited platelet adhesion, aggregation, and thrombus formation in perfusion chambers at high shear conditions and efficiently dissolved preformed thrombi. Anfibatide also inhibited thrombus growth at low shear conditions, though less than at high shear. Using intravital microscopy, we found that Anfibatide markedly inhibited thrombosis in laser-injured cremaster vessels and prevented vessel occlusion in FeCl3-injured mesenteric vessels. Importantly, Anfibatide further inhibited residual thrombosis in VWF-deficient mice, suggesting that Anfibatide has additional antithrombotic effect beyond its inhibitory role in GPIb-VWF interaction. Anfibatide did not significantly cause platelet activation, prolong tail bleeding time, or cause bleeding diathesis in mice. Thus, consistent with the data from an ongoing clinical trial, the data from this study suggests that Anfibatide is a potent and safe antithrombotic agent.
authors.forename: Xi
authors.initials: X
authors.lastname: Lei
authors.forename: Adili
authors.initials: A
authors.lastname: Reheman
authors.forename: Yan
authors.initials: Y
authors.lastname: Hou
authors.forename: Hui
authors.initials: H
authors.lastname: Zhou
authors.forename: Yiming
authors.initials: Y
authors.lastname: Wang
authors.forename: Alexandra H
authors.initials: AH
authors.lastname: Marshall
authors.forename: Chaofan
authors.initials: C
authors.lastname: Liang
authors.forename: Xiangrong
authors.initials: X
authors.lastname: Dai
authors.forename: Benjamin Xiaoyi
authors.initials: BX
authors.lastname: Li
authors.forename: Karen
authors.initials: K
authors.lastname: Vanhoorelbeke
authors.affiliation: Dr. Heyu Ni, MD, PhD, Canadian Blood Services and, Department of Laboratory Medicine and Pathobiology, St. Michael's Hospital, University of Toronto, Room 420, LKSKI - Keenan Research Center, 209 Victoria Street, Toronto, Ontario, M5B 1W8, Canada, Tel.: +1 416 847 1738, E-mail: nih@smh.ca.
authors.forename: Heyu
authors.initials: H
authors.lastname: Ni
mesh_terms: D000818:Animals; D001665:Binding Sites; D001792:Blood Platelets / Q000187:drug effects* / Q000378:metabolism; D002712:Chlorides; D003435:Crotalid Venoms / Q000494:pharmacology* / Q000633:toxicity; D004195:Disease Models, Animal; D005260:Female; D005290:Ferric Compounds; D005343:Fibrinolytic Agents / Q000494:pharmacology* / Q000633:toxicity; D006470:Hemorrhage / Q000139:chemically induced; D037181:Lectins, C-Type; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D010973:Platelet Adhesiveness / Q000187:drug effects*; D010974:Platelet Aggregation / Q000187:drug effects; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology* / Q000633:toxicity; D019038:Platelet Glycoprotein GPIb-IX Complex / Q000037:antagonists & inhibitors* / Q000378:metabolism; D011485:Protein Binding; D013927:Thrombosis / Q000097:blood / Q000209:etiology / Q000235:genetics / Q000517:prevention & control*; D013997:Time Factors; D057772:Vascular System Injuries / Q000150:complications; D014841:von Willebrand Factor / Q000235:genetics / Q000378:metabolism
chemical_list: D002712:Chlorides; D003435:Crotalid Venoms; D005290:Ferric Compounds; D005343:Fibrinolytic Agents; D037181:Lectins, C-Type; D010975:Platelet Aggregation Inhibitors; D019038:Platelet Glycoprotein GPIb-IX Complex; D014841:von Willebrand Factor; C000592236:agkisacucetin protein, Agkistrodon acutus; C024555:ferric chloride
keywords: Antithrombotic agent; glycoprotein Ib-IX-V complex; platelet inhibitor; snake venoms