The future of siRNA-mediated approaches to treat von Willebrand disease

Abstract

Introduction: The clinical management of the inherited bleeding disorder von Willebrand disease (VWD) focuses on normalizing circulating levels of von Willebrand factor (VWF) and factor VIII (FVIII) to prevent or control bleeding events. The heterogeneous nature of VWD, however, complicates effective disease management and development of universal treatment guidelines.

Areas covered: The current treatment modalities of VWD and their limitations are described and why this prompts the development of new treatment approaches. In particular, RNA-based therapeutics have gained significant interest because of their ability to reversibly alter gene expression with long-term efficacy. In the field of VWD, small-interfering RNAs (siRNAs) have been explored through various strategies to improve disease phenotypes. These different approaches are discussed as well as their potential impact on reshaping the future therapeutic landscape.

Expert opinion: Current treatments for VWD often require frequent intravenous administration of VWF concentrates or desmopressin, with only short-term benefits. Moreover, remaining circulating mutant VWF can cause detrimental effects. Allele-selective siRNA-based therapies could provide more reliable and long-term disease correction by specifically targeting mutant VWF. This approach could be applied to a large part of the population aligning with the growing emphasis on personalized treatment and patient-centered care in VWD management.

Keywords: RNA therapy; siRNA; treatment; von Willebrand disease; von Willebrand factor.

Figure 1.

Schematic overview of VWF protein structure and characteristics of types of VWD. a. Domain structure of a VWF monomer including the signal peptide (SP), propeptide, the C-terminal cystine knot (CK) and important binding sites for FVIII, GPIb, collagen and ADAMTS13. VWF monomers dimerize at the CK domain and further assemble into multimers at the D3 domain. In physiological situations, VWF circulates as multimers with bound FVIII. As a result of dominant-negative missense variants, mutant VWF remains in the circulation, resulting in the competition between mutant and normal VWF and continuous secretion of functionally defective VWF multimers. These functionally defective VWF multimers can cause detrimental effects, despite the presence of normal VWF. b. Quantitative defects in VWF can result in VWD types 1 and 3 whereas qualitative defects lead to VWD type 2 which is categorized into four subtypes. VWD type 1 caused by missense variants and VWD types 2A, 2B and 2 M would be suitable for an allele-selective siRNA approach. Figure created with BioRender.

Figure 2.

Schematic overview of an allele-selective SNP-based siRNA approach for VWD. a Overview of the distribution of SNPs within the two VWF alleles of an example patient with VWD type 2B. On the left is a representation of the normal VWF allele of the patient, and on the right, an example of the mutant allele carrying the c.3946 G>A variant (p.Val1316Met), which causes VWD type 2B. This variant is in linkage with the SNP allele c.1451A, which can be used as an siRNA target. b Schematic overview of allele-selective SNP-based siRNA approach, where an siRNA specifically targets the SNP allele that is in linkage with the VWD-causing variant. The siRNAs are encapsulated within endothelial-specific lipid nanoparticles (LNPs) for targeted delivery to VWF-producing endothelial cells. The siRNA exhibits full complementarity with the mutant VWF messenger RNA (mRNA) resulting in degradation of the mutant mRNA and inhibition of translation into mutant VWF protein. The siRNA is not complimentary to the normal VWF mRNA resulting in translation of the mRNA into normal VWF protein and assembly into multimers. Figure created with BioRender.

Figure 3.

Workflow for future allele-selective siRNA research. This figure outlines the key steps involved in developing an allele-selective siRNA therapeutic for VWD. The process begins with the selection of an appropriate siRNA target. In this example, this target is the SNP allele c.1451A (orange target) that is in linkage with a vwd-causing variant (red). Following target selection, the design of a lead siRNA and its corresponding delivery vehicle should be explored. This phase incorporates in silico predictions and chemical modifications to enhance the siRNA’s effectiveness. Optimization of the siRNA and delivery vehicle is performed through testing in preclinical models, including in vitro and ex vivo cell systems, as well as in in vivo small animal models. The insights gained from these optimizations may lead to the development of additional lead siRNAs with improved selectivity for inhibiting mutant VWF. The ultimate goal is to advance these allele-selective siRNA candidates from preclinical to clinical studies. Achieving this will require focusing on the use of human-specific siRNAs in humanized experimental models, ensuring that the therapeutic approach is both safe and effective for human applications. Figure created with BioRender.