Egaptivon pegol

A DNA aptamer to the von Willebrand factor (VWF) A1 domain, TAGX-0004, inhibits the binding of VWF to platelets. Nucleic acid aptamers are single-stranded DNA or RNA molecule forming three-dimensional structures that are capable of specifically binding to proteins and are expected to contribute to alternative medicine. ARC1779, an aptamer targeting the VWF A1 domain, had been evaluated in a phase II clinical trial of patients with acquired thrombotic thrombocytopenic purpura (aTTP); however, its development was terminated. Caplacizumab, an anti-VWF A1 domain nanobody, is now increasingly employed as first-line therapy for the treatment of aTTP in Western countries. However, there have been reports regarding adverse bleeding events and the high cost of the treatment. In this study, the inhibitory effects of TAGX-0004 were compared with those of ARC1779 and caplacizumab on in vitro platelet aggregation and thrombus formation. TAGX-0004 had an excellent high affinity to the VWF A1 domain and superior efficacy, such as its potent inhibitory activity in in vitro platelet aggregation and thrombus formation. Therefore, it can potentially overcome the problems associated with caplacizumab and can be developed as a promising drug not only for aTTP treatment but also for the treatment of the various VWF-mediated thrombotic disorders.

Here, we propose a new approach for quantitative estimation of von Willebrand factor (vWF) exposed on the surface of endothelial cells (ECs) using the ARC1779 aptamer that interacts with the vWF A1 domain. To visualize complex formation between vWF and the aptamer, the latter was conjugated with the Cy5 fluorescent label. Cultured human umbilical vein endothelial cells (HUVEC) were stained with the ARC1779-Cy5 conjugate and imaged with a fluorescence microscope. The images were analyzed with the CellProfiler software. vWF released from the Weibel–Palade bodies was observed as bright dot-like structures of round and irregular shape, the number of which increased several times after HUVEC exposure to histamine or thrombin. Staining with ARC1779-Cy5 also revealed long filamentous vWF structures on the surface of activated HUVEC. vWF secretion by ECs is activated by the second messengers cAMP and Ca2+. There is evidence that hydrogen peroxide also acts as a second messenger in ECs. In addition, exogenous H2O2formed in leukocytes can enter ECs. The aim of our study was to determine the effect of H2O2on the vWF exposure at the surface of HUVEC using the proposed method. It was shown that hydrogen peroxide at concentration 100 µM, which is lower than the cytotoxicity threshold of H2O2for cultured HUVEC, increased several times the number of dot-like structures and total amount of vWF exposed on plasma membrane of HUVEC, which suggest that H2O2acts as a mediator that activates exocytosis of Weibel–Palade bodies and vWF secretion in the vascular endothelium during inflammation and upon elevated generation of endogenous reactive oxygen species in ECs.