The in vitro effect of the new antithrombotic drug candidate ALX-0081 on blood samples of patients undergoing percutaneous coronary intervention

Summary

Compound ALX-0081 is a bivalent humanised Nanobody^® that binds the A1-domain of von Willebrand factor (VWF) with high affinity. Consequently, it can block the interaction between VWF and its platelet-receptor- glycoprotein Ib, which leads inevitably to formation of arterial thrombi. It was the objective of this study to assess the in vitro effects of ALX-0081 on platelet adhesion and aggregation in coronary artery disease (CAD) patients to determine the optimal concentration of ALX-0081 and the effect of co-medication. We included nine CAD patients, who were scheduled for elective percutaneous coronary intervention (PCI), and 11 healthy volunteers. At admission all patients received aspirin, clopidogrel and heparin. Blood was drawn 24 hours (h) before and 1 h after start of the PCI procedure and was subsequently spiked with different concentrations of ALX-0081 or buffer. The efficacy of ALX-0081 was assessed by in vitro experiments: flow chamber experiments, ristocetin-induced platelet aggregation (RIPA), and the platelet function analyser (PFA-100^TM). VWF levels in CAD patients were significantly higher than in healthy controls. During PCI VWF levels did not rise. In all in vitro experiments, ALX-0081 led to complete inhibition of platelet adhesion and aggregation. However, the required effective concentration was higher in patients than in controls and was related to plasma VWF levels. In conclusion, ALX-0081 is able to completely inhibit in vitro platelet adhesion and aggregation in CAD patients scheduled for elective PCI. The efficacy of ALX-0081 is not influenced by PCI or co-medication. However, due to higher VWF levels in CAD patients a higher effective concentration of ALX-0081 was required than in healthy individuals.

ALX-0081 - antithrombotic drugs - von Willebrand Factor - PTCA

• References

• 1 Silber S. et al. Guidelines for percutaneous coronary interventions. The Task Force for Percutaneous Coronary Interventions of the European Society of Cardiology. Eur Heart J 2005; 26: 804-847.
• 2 The EPIC Investigation. Use of a monoclonal antibody directed against the platelet glycoprotein IIb/IIIa receptor in high-risk coronary angioplasty. N Engl J Med 1994; 330: 956-961.
• 3 Therapy EIESotPIIRwI. Novel dosing regimen of eptifibatide in planned coronary stent implantation (ESPRIT): a randomised, placebo-controlled trial. Lancet 2000; 356: 2037-2044.
• 4 Spiel AO. et al. von Willebrand factor in cardiovascular disease: focus on acute coronary syndromes. Circulation 2008; 117: 1449-1459.
• 5 Ruggeri ZM. Old concepts and new developments in the study of platelet aggregation. J Clin Invest 2000; 105: 699-701.
• 6 Ruggeri ZM, Ware J. von Willebrand factor. Faseb J 1993; 7: 308-316.
• 7 Lip GY, Blann A. von Willebrand factor: a marker of endothelial dysfunction in vascular disorders?. Cardiovasc Res 1997; 34: 255-265.
• 8 Martinelli I. von Willebrand factor and factor VIII as risk factors for arterial and venous thrombosis. Semin Hematol 2005; 42: 49-55.
• 9 Fuchs I. et al. Platelet function in patients with acute coronary syndrome (ACS) predicts recurrent ACS. J Thromb Haemost 2006; 4: 2547-2552.
• 10 Wiman B. et al. Plasma levels of tissue plasminogen activator/plasminogen activator inhibitor-1 complex and von Willebrand factor are significant risk markers for recurrent myocardial infarction in the Stockholm Heart Epidemiology Program (SHEEP) study. Arterioscler Thromb Vasc Biol 2000; 20: 2019-2023.
• 11 Holz J. ALX-0081 a novel anti-platelet thrombotic: first results of a multiple dose phase I study in patients with stable angina undergoing PCI. J Thromb Haemost 2009; 7 (Suppl. 02) 765.
• 12 Ulrichts H. Antithrombotic drug candidate ALX-0081 shows superior preclinical efficacy and safety compared to currently marketed antiplatelet drugs (abstract). Blood. 2011 epub.
• 13 Deckmyn H. et al. Development of antibodies that interfere with the collagen- VWF-GPIb axis as new antithrombotics. Verh K Acad Geneeskd Belg 2005; 67: 55-65.
• 14 De Vleeschauwer A, Devreese K. Comparison of a new automated von Willebrand factor activity assay with an aggregation von Willebrand ristocetin cofactor activity assay for the diagnosis of von Willebrand disease. Blood Coagul Fibrinolysis 2006; 17: 353-358.
• 15 Sucker C. et al. Determination of von Willebrand factor activity: evaluation of the HaemosIL assay in comparison with established procedures. Clin Appl Thromb Hemost 2006; 12: 305-310.
• 16 Sakariassen KS. et al. A perfusion chamber developed to investigate platelet interaction in flowing blood with human vessel wall cells, their extracellular matrix, and purified components. J Lab Clin Med 1983; 102: 522-535.
• 17 Dong JF. et al. Ristocetin-dependent, but not botrocetin-dependent, binding of von Willebrand factor to the platelet glycoprotein Ib-IX-V complex correlates with shear-dependent interactions. Blood 2001; 97: 162-168.
• 18 Mammen EF. et al. PFA-100 system: a new method for assessment of platelet dysfunction. Semin Thromb Hemost 1998; 24: 195-202.
• 19 Mega JL. et al. Cytochrome p-450 polymorphisms and response to clopidogrel. N Engl J Med 2009; 360: 354-362.
• 20 Simon T. et al. Genetic determinants of response to clopidogrel and cardiovascular events. N Engl J Med 2009; 360: 363-375.
• 21 Gurbel PA. et al. Clopidogrel for coronary stenting: response variability, drug resistance, and the effect of pretreatment platelet reactivity. Circulation 2003; 107: 2908-2913.
• 22 Jaremo P. et al. Individual variations of platelet inhibition after loading doses of clopidogrel. J Intern Med 2002; 252: 233-238.
• 23 Firbas C. et al. Targeting von Willebrand factor and platelet glycoprotein Ib receptor. Expert Rev Cardiovasc Ther 2010; 8: 1689-1701.
• 24 Gilbert JC. et al. First-in-human evaluation of anti von Willebrand factor therapeutic aptamer ARC1779 in healthy volunteers. Circulation 2007; 116: 2678-2686.
• 25 Spiel AO. et al. The aptamer ARC1779 is a potent and specific inhibitor of von Willebrand Factor mediated ex vivo platelet function in acute myocardial infarction. Platelets 2009; 20: 334-340.
• 26 Jilma B. et al. A randomised pilot trial of the anti-von Willebrand factor aptamer ARC1779 in patients with type 2b von Willebrand disease. Thromb Haemost 2010; 104: 563-570.
• 27 Jilma-Stohlawetz P. et al. Inhibition of von Willebrand factor by ARC1779 in patients with acute thrombotic thrombocytopenic purpura. Thromb Haemost 2011; 105: 545-552.
• 28 Lisman T. et al. Recombinant factor VIIa enhances deposition of platelets with congenital or acquired alpha IIb beta 3 deficiency to endothelial cell matrix and collagen under conditions of flow via tissue factor-independent thrombin generation. Blood 2003; 101: 1864-1870.
• 29 Lisman T. et al. Recombinant factor VIIa restores aggregation of alphaIIb- beta3-deficient platelets via tissue factor-independent fibrin generation. Blood 2004; 103: 1720-1727.
• 30 Frossard M. et al. Platelet function predicts myocardial damage in patients with acute myocardial infarction. Circulation 2004; 110: 1392-1397.
• 31 Campo G. et al. Value of platelet reactivity in predicting response to treatment and clinical outcome in patients undergoing primary coronary intervention: insights into the STRATEGY Study. J Am Coll Cardiol 2006; 48: 2178-2185.
• 32 Van der Planken MG. et al. Comparison of turbidimetric aggregation and in vitro bleeding time (PFA-100) for monitoring the platelet inhibitory profile of antiplatelet agents in patients undergoing stent implantation. Thromb Res 2003; 111: 159-164.
• 33 Peters AJ. et al. In vitro bleeding test with PFA-100-aspects of controlling individual acetylsalicylic acid induced platelet inhibition in patients with cardiovascular disease. J Thromb Thrombolysis 2001; 12: 263-272.
• 34 Favaloro EJ. Utility of the PFA-100 for assessing bleeding disorders and monitoring therapy: a review of analytical variables, benefits and limitations. Haemophilia 2001; 7: 170-179.