Therapeutic efficacy of the platelet glycoprotein Ib antagonist anfibatide in murine models of thrombotic thrombocytopenic purpura

Abstract

Thrombotic thrombocytopenic purpura (TTP), a potentially fatal blood clot disorder, is primarily caused by severe deficiency of plasma ADAMTS13 activity resulting from acquired autoantibodies. Plasma exchange is the only effective initial therapy. However, the high mortality rate and the complications associated with plasma exchange therapy remain a major concern. To address unmet clinical needs, therapeutic efficacies of anfibatide, a snake venom-derived platelet glycoprotein Ib antagonist, in murine models of spontaneous thrombocytopenia and shigatoxin-induced TTP were determined. A light scattering platelet aggregometry, microfluidic shear-based assay, and murine models of TTP were used in the study. We showed that purified anfibatide inhibits ristocetin- or botrocetin-induced human or murine platelet agglutination in the presence of von Willebrand factor in a concentration-dependent manner. Anfibatide could also dramatically inhibit the adhesion and aggregation of murine and human platelets on a collagen surface under arterial shear stress, in the presence or absence of plasma ADAMTS13 activity. Most importantly, we demonstrated that an intraperitoneal administration of anfibatide at the dose of 60 ng/g body weight twice daily mitigated spontaneous thrombocytopenia and prevented shigatoxin-induced TTP in Adamts13−/− and disease-susceptible mice (CAST/Ei strain). Thus, we conclude that anfibatide, when administered at the optimal dosage, route, and interval, is efficacious in treating spontaneous and bacterial shigatoxin-induced TTP in the murine models. Our findings may provide the basis for further development of anfibatide for the treatment of acute TTP in humans.

Platelet Signaling and Disease: Targeted Therapy for Thrombosis and Other Related Diseases

“…Within 20 min (King et al, 2016) Within 20 min (King et al, 2016) Within 20 min (King et al, 2016) 2 h (Ungerer et al, 2011) .4 h (De Luca, 2012) .4 h (De Luca, 2012) 4-8 h (Topol, 1999;Vorchheimer et al, 1999) Half-life 10 h (Gregov et al, 1987) 10-11 h (Eikelboom et al, 2012) 24-36 h (Eikelboom et al, 2012) 20 min (Umemura and Iwaki, 2016) 30 min to 7.5 h (Umemura et al, 2016) 7-9 h (Teng and Butler, 2013) 3-5 min (Sible and Nawarskas, 2017) 5-7 h (murine) (Zheng et al, 2016) Prodrug No Yes (CYP3A5 and CYP2C19) (Yoo et al, 2009(Yoo et al, , 2010 Yes Yes…”

“…Interestingly, the utility of anfibatide has also been evaluated in preventing a fatal blood-clotting disorder, such as TTP. Intraperitoneal administration of anfibatide mitigated spontaneous thrombocytopenia and prevented a shigatoxin-induced TTP murine model (Zheng et al, 2016) (ADAMTS13-deficient mice). Although anfibatide has completed its clinical phase I for safety and efficacy in patients with non-ST elevation myocardial infarction, phase II has yet to commence.…”

Biomechanical thrombosis: the dark side of force and dawn of mechano-medicine

“…Notably, unpublished phase IIa human clinical trials have shown the promise of anfibatide as a novel antiplatelet agent without significantly affecting haemostasis in patients with non-ST segment elevation myocardial infarction (MI) 81. Additionally, anfibatide was also shown as a promising candidate to treat ischaemic stroke and spontaneous or bacterial shigatoxin-induced acquired thrombotic thrombocytopenic purpura (TTP) in experimental animal models 82 83…”

Beyond plasma exchange: novel therapies for thrombotic thrombocytopenic purpura

“…In a microfluidic shear model, anfibatide inhibited platelet adhesion, aggregation, and thrombosis formation under static and shear conditions and resulted in resolution of spontaneous thrombocytopenia in a Shiga toxin-induced murine TTP model. 43 However, the safety and efficacy of anfibatide for TTP treatment in human subjects requires further study in prospective clinical trials. Emerging data suggest that TTP may be associated with complement activation, perhaps through ultra-large VWFmediated effects, 44 and the successful use of the terminal complement inhibitor, eculizumab, in TTP has been reported.…”