Allele-selective von Willebrand factor silencing.

A State-of-the-Art lecture entitled "Allele-selective von Willebrand Factor (VWF) silencing" was presented at the International Society on Thrombosis and Haemostasis (ISTH) congress in 2025. The concept, potential applications, and feasibility of allele-selective VWF inhibition will be discussed in detail in this review. VWF plays a crucial role in supporting hemostasis, which is important in bleeding as well as thrombotic disorders. Decreased or functionally defective VWF results in von Willebrand disease (VWD), whereas high VWF levels have been associated with thrombotic risk. By silencing the synthesis of VWF from the mutant VWF gene in VWD, one might eliminate the production of mutant VWF and thereby normalize multimer composition and increase the levels of functional VWF. This would lead to phenotypic improvement in VWD. In the context of high plasma VWF levels and thrombotic disorders, silencing of one VWF allele will lower VWF in the circulation and endothelial cells, but at the same time, allele-selective silencing prevents an excessive reduction in VWF levels. Limited VWF reduction will reduce thrombosis risk without inducing bleeding. Selectively silencing the expression of one VWF allele, based on a single nucleotide difference between the 2 alleles, using small interfering RNAs has proven to be successful. This approach resulted in phenotypic improvement for VWD in vitro as well as in vivo. Preliminary data in the context of thrombotic risk indicated that silencing one VWF allele reduced thrombosis development without increasing bleeding. Finally, we summarize relevant new data on other new treatments for VWD presented during the 2025 ISTH Congress.