Abstract
BackgroundSZ-123, a murine monoclonal antibody that targets the human von Willebrand factor (VWF) A3 domain and blocks the binding of collagen, is a powerful antithrombotic. In a Rhesus monkey model of thrombosis, SZ-123 had no side effects, such as bleeding or thrombocytopenia.MethodsThe mouse/human chimeric version of SZ-123, MHCSZ-123, was developed and maintained inhibitory capacities in vitro and ex vivo after injection into monkeys. CHO-S cells were selected for stable expression of MHCSZ-123. Cell clones with high levels of MHCSZ-123 expression were screened with G418 then adapted to serum-free suspension culture. The antithrombotic effect of MHCSZ-123 on acute platelet-mediated thrombosis was studied in monkeys where thrombus formation was induced by injury and stenosis of the femoral artery, which allowed for cyclic flow reductions (CFRs). CFRs were measured in the femoral artery of anesthetized Rhesus monkeys before and after intravenous administration of MHCSZ-123. Ex vivo VWF binding to collagen, platelet aggregation, platelet counts, and template bleeding time were used as measurements of antithrombotic activity. In addition, plasma VWF and VWF occupancy were measured by ELISA.ResultsInjection of 0.1, 0.3, and 0.6 mg/kg MHCSZ-123 significantly reduced CFRs by 29.4%, 57.9%, and 73.1%, respectively. When 0.3 and 0.6 mg/kg MHCSZ-123 were administered, 46.6%–65.8% inhibition of ristocetin-induced platelet aggregation was observed between 15 and 30 min after injection. We observed minimal effects on bleeding time, minimal blood loss, and no spontaneous bleeding or thrombocytopenia.ConclusionsThe VWF-A3 inhibitor MHCSZ-123 significantly reduced thrombosis in Rhesus monkeys and appeared to be safe and well tolerated.
Highlights
SZ-123, a murine monoclonal antibody that targets the human von Willebrand factor (VWF) A3 domain and blocks the binding of collagen, is a powerful antithrombotic
The interaction between von Willebrand factor (VWF), and platelet glycoprotein (GP) Ibα is the key for initiating the response to vascular injury that leads to hemostasis or, under pathological conditions, thrombosis [1,2,3]
VWF occupancy VWF occupied by MHCSZ-123 was estimated using a competition Enzyme-linked immunosorbent assay (ELISA) assay with a fixed concentration of biotinylated SZ-123 (Bio-SZ-123) in combination with streptavidin-horseradish peroxidase (HRP) (Thermo)
Summary
SZ-123, a murine monoclonal antibody that targets the human von Willebrand factor (VWF) A3 domain and blocks the binding of collagen, is a powerful antithrombotic. The interaction between von Willebrand factor (VWF), and platelet glycoprotein (GP) Ibα is the key for initiating the response to vascular injury that leads to hemostasis or, under pathological conditions, thrombosis [1,2,3]. Many different components have been identified that contribute to thrombosis, and several therapeutic approaches have been developed for this severe clinical complication. While these treatments have been effective in the clinical setting, they have a limited therapeutic window and are associated with clinically significant bleeding, when high doses of the drugs are used [4, 5]. Its levels are heightened in patients, who experienced adverse cardiac events that are linked to a poorer prognosis [19,20,21]
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