Correction of VWF multimerization in type 2A/IIC von Willebrand disease by exogenous VWF propeptide supplementation.

Gene therapy remains the only cure for von Willebrand disease (VWD), but it is limited by the large von Willebrand factor (VWF) gene size. Variants affecting the VWF propeptide (VWFpp) impair multimerization, causing type 2A/IIC VWD. VWFpp serves as a pH-sensitive template for VWF multimer assembly, suggesting that in trans VWFpp supplementation may restore multimerization in VWF variants with defective propeptides. Co-expression of wild-type VWFpp with mutant full-length VWF in vitro led to modest yet consistent improvements in the VWF multimer profile across eight type 2A/IIC VWD-causing variants. Notably, variants with defect D2:D2 interface required lower levels of VWFpp for multimerization rescue, whereas those with intact D2:D2 interfaces exhibited a greater demand. Furthermore, a transgenic mouse model of type 2A/IIC VWD carrying the p.Tyr87Ser mutation was treated with an AAV9 vector encoding VWFpp under the control of endothelial-specific promoters. VWFpp administration remarkably restored VWF multimerization, increased VWF:CB levels from 15.8% ± 10.2% to 71.2% ± 12.7% for at least 16 weeks, corrected the bleeding tendency and improved platelet function. Both in vitro and in vivo findings demonstrate that in trans VWFpp supplementation can rectify defects in VWF multimerization caused by variants in VWFpp, offering a novel therapeutic strategy for type 2A/IIC VWD.