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Abstract

Von Willebrand disease (VWD) is an inherited bleeding disorder resulting from a deficiency in von Willebrand factor (VWF), either quantitative or qualitative. Recombinant VWF (rVWF) presents a novel therapeutic option for patients with VWD. Produced in Chinese hamster ovary cells, rVWF is free of animal or human plasma proteins, thus eliminating the risk of pathogen transmission. It preserves the full range of VWF multimers, including ultra-large multimers, which are essential for hemostasis. Research indicates that rVWF demonstrates superior pharmacokinetics and pharmacodynamics compared to plasma-derived VWF, offering a longer terminal half-life, enhanced platelet adhesion and aggregation, and more robust factor VIII stabilization. These properties contribute to rVWF’s increased hemostatic efficacy in managing bleeding episodes and perioperative surgical bleeding in adults and children with VWD, as well as the routine prophylaxis for adults to reduce the frequency of bleeding episodes. Furthermore, rVWF is well-tolerated with a low thrombotic risk, making it a promising treatment option and addressing a significant clinical need globally.

Keywords

clinical application mechanism of action recombinant von Willebrand factor ultra-large multimers von Willebrand disease

Introduction

Von Willebrand disease (VWD) is an inherited bleeding disorder caused by either a quantitative or qualitative deficiency in von Willebrand factor (VWF).¹ The condition follows autosomal dominant (or incomplete dominant) or recessive inheritance.² VWF is a large multimeric glycoprotein synthesized by endothelial cells (ECs) and megakaryocytes. After post-translational modifications in the Golgi apparatus, up to 95% of VWF is constitutively secreted into plasma, with the remainder stored in EC Weibel-Palade bodies and the α-granules of megakaryocytes.³ VWF plays a pivotal role in hemostasis through two primary mechanisms: (1) mediating initial platelet adhesion and aggregation by bridging subendothelial collagen and platelet surface glycoproteins, and (2) stabilizing factor VIII (FVIII) in circulation as a carrier.^4,5 Plasma VWF circulates as multimers of varying sizes, with ultra-large multimers (ULMs) (>10,000 kDa, >20 mers) being secreted into the plasma in healthy individuals and rapidly degraded by the protease ADAMTS13 into smaller subunits.⁶

VWD is classified into three main types: types 1 and 3, which represent quantitative deficiencies of VWF, and type 2, which includes qualitative defects in VWF function. Type 1, characterized by a partial decrease in VWF levels, is the most common form, while type 3, marked by complete absence of VWF, is the rarest subtype.⁷ The prevalence of VWD is reported to range from 108.9 to 2200 per 100,000 in population-based studies, and from 0.3 to 16.5 per 100,000 in referral-based studies.⁸ For type 3 VWD, population-based estimates suggest a prevalence of 0.5 per 1,000,000.⁸ In China, a disease is considered rare if it meets any of the following criteria: neonatal incidence rate <1/10,000, prevalence <1/10,000, or the number of affected individuals <140,000. Accordingly, type 3 VWD is listed in the second edition of the National Rare Diseases List of China.⁹ Available data indicate that most VWD cases in China remain undiagnosed, highlighting a significant unmet need for treatment.

Current treatment guidelines for VWD include desmopressin 1-deamino-8-D-arginine vasopressin (DDAVP) and replacement therapy.^1,10 DDAVP increases plasma VWF levels by stimulating vascular ECs to release stored VWF. However, desmopressin is ineffective or contraindicated in severe VWD and certain subtypes and is associated with tachyphylaxis.¹¹ Replacement therapy aims to directly elevate plasma VWF levels using either VWF-containing concentrates derived from human plasma (plasma-derived VWF (pdVWF)) or recombinant VWF (rVWF). This approach is recommended for on-demand treatment and management of bleeding episodes, as well as perioperative care.^12,13 A major limitation of pdVWF is its lack of high and ULMs, which are essential for the hemostatic function of VWF. In contrast, rVWF includes the full spectrum of multimers.¹⁴ Vonicog alfa, the first and currently only available rVWF product, was officially approved by the National Medical Products Administration (NMPA) in August 2024 for on-demand (OD) treatment and control of bleeding events (BEs) in adult patients with VWD (aged 18 years and above), as well as for perioperative bleeding management. This article explores the mechanism of action of rVWF and its clinical application in patients with VWD. A narrative review was conducted by searching PubMed and Embase databases up to July 2025. Keywords used in the search included “von Willebrand disease,” “recombinant von Willebrand factor,” “VWD prophylaxis,” and “pediatric VWD.” Publications in English and Chinese were considered, with a particular focus on clinical trials, observational studies, and guideline documents.

Production of rVWF

rVWF is co-expressed with recombinant FVIII (rFVIII) in Chinese hamster ovary (CHO) cells. The material obtained from the column flow-through during the FVIII capture step, which contains pro-VWF, serves as the starting material for rVWF production.¹⁵ Since CHO cells produce partially processed rVWF, the material is then exposed to recombinant CHO-cell-derived furin to remove the VWF pro-peptide, yielding fully processed, mature rVWF.¹⁶ This exposure to rFurin in vitro transforms the heterogeneous multimer mixture of incompletely processed pro-VWF into highly homogeneous, structurally intact multimers. The fermentation process for both rVWF and furin, along with downstream processing, is carried out under serum-free and protein-free conditions. Following capture via an ion-exchange column, rVWF undergoes full processing to mature VWF by recombinant furin. After DNA removal, the product is treated with solvent-detergent (SD) and further purified through two additional chromatography steps. The resulting rVWF achieves a purity of >99%, representing almost pure VWF.¹⁵ In contrast, pdVWF concentrates, which are sourced from human plasma, exhibit variability in their VWF and FVIII content, depending on the source plasma and manufacturing process. Variations between batches of the same product have been noted, along with the presence of other extraneous plasma proteins that can cause allergic reactions.^13,17 This variability poses a potential risk of venous thromboembolism due to excessive FVIII levels.

The complexity of the manufacturing process and the high technical barriers involved in rVWF production confer several advantages. The absence of animal or human plasma proteins during manufacturing virtually eliminates the risk of transmitting hematogenous adventitious agents. Moreover, recombinant production addresses the limited availability of plasma-derived products. Importantly, rVWF retains intact VWF subunits, including ULMs, due to its non-exposure to ADAMTS13,¹⁵ which contributes to its enhanced functional properties.

Features of rVWF

VWF multimer composition analysis

Sodium dodecyl sulfate (SDS)-agarose gel electrophoresis (SDS-PAGE) using low-resolution 1% and high-resolution 2.5% SDS-agarose gels is commonly employed to visualize the multimerization level of VWF concentrates and assess the presence of satellite bands caused by ADAMTS13 cleavage.¹⁸

Turecek et al.^14,15 described the electrophoretic analysis of rVWF, showing that under reducing conditions in SDS-PAGE, rVWF appears as single bands, indicating homogeneity in multimer distribution. In contrast, pdVWF and pdVWF/FVIII contain additional proteins. Low-resolution SDS-PAGE confirmed that rVWF contains ULMs, which are absent in human plasma or pdVWF concentrates. High-resolution SDS-PAGE revealed a typical satellite band pattern in human plasma and pdVWF/FVIII, while no satellite bands were observed with rVWF, indicating that rVWF is not exposed to proteolytic processing by ADAMTS13. Consistent with these findings, Gritsch et al.¹⁹ reported similar observations when comparing the structure and function of rVWF with pdVWF and pdVWF/FVIII. This analysis confirmed that rVWF maintains a non-degraded VWF multimer pattern, including ULMs, which are absent in pdVWF concentrates. Additionally, pdVWF/FVIII concentrates exhibited multimeric patterns distinct from human plasma: the faster- and central-migrating bands were more intense, while the slower-migrating satellite band was notably faint. These results align with previous studies reporting variable VWF multimeric patterns compared to normal human plasma.²⁰ Overall, multimer analysis by SDS-PAGE demonstrates that rVWF retains the full spectrum of intact multimers, particularly ULMs, contributing to its higher functional activity compared to pdVWF.

Functional activity

VWF potency is assessed using multiple parameters, including VWF:platelet binding activity, VWF:collagen binding activity (VWF:CB), FVIII binding capacity, and VWF-mediated platelet adhesion under flow conditions.^1,12 VWF:platelet binding activity can be measured by various assays, such as the VWF ristocetin cofactor (VWF:RCo) assay, VWF glycoprotein Ib receptor binding assay (VWF:GPIbR), and VWF glycoprotein Ib mutant binding assay (VWF:GPIbM).²¹ To enable product comparison, specific VWF activity is calculated as the ratio relative to VWF antigen (VWF:Ag), while the FVIII binding capacity of rVWF is calculated relative to the reference standard, which is normal human plasma. Biochemical studies have shown that rVWF exhibits enhanced collagen binding and platelet binding capacity compared to pdVWF. These effects appear to correlate with multimer size and may be attributed to the presence of ULMs in rVWF. Please find the highlighted differences between rVWF and pdVWF (including brand name, generic name, raw material source, manufacturing process, presence of ULM, half-life of VWF, VWF:RCo/Ag, route of administration, and approved indications) in Table 1.

Table 1.

Comparison of recombinant VWF and plasma-derived VWF.

Dimension	Recombinant VWF	Plasma-derived VWF
		VWF:RCo/FVIII ratio ⩽ 1	VWF:RCo/FVIII ratio > 1 to <10	VWF:RCo/FVIII ratio ⩾ 10
Brand name	Vonvendi/Veyvondi²⁹	Wilate³⁰	Humate-P/Haemate-P³¹	Wilfactin/Willfact³²
Generic name	Vonicog alfa	Human von Willebrand factor/ coagulation factor VIII complex	Antihemophilic factor/von Willebrand factor complex (human)	Human von Willebrand factor
Raw material source	Recombinant, CHO cell; no human/animal proteins	Human plasma-derived VWF/FVIII complex	Human plasma-derived VWF/FVIII complex	Human plasma-derived VWF with very low FVIII
Manufacturing process	CHO cell expression, matured by cleavage with recombinant furin*; no ADAMTS13 exposure during production, multi-step purification, and viral safety steps	Adsorption treatment, dual chromatography purification, ultrafiltration/diafiltration, sterile filtration, and virus inactivation	Adsorption treatment, cryoprecipitation purification, ultrafiltration/diafiltration, sterile filtration, and virus inactivation	Cryoprecipitation, dual chromatography purification, nanofiltration, and virus inactivation
ULM	Present; full spectrum of HMW and ULM	Absent	Absent	Absent
Half-life of VWF	~22.6 h(adult), ~14.0 h(child)	15.8 h(adult), 8.3 h(child)	10–11 h	12.4 h (not disclosed on label, data from study³³)
VWF:RCo/Ag	⩾1	0.9	0.8	0.7
Route of Administration	Intravenous injection	Intravenous injection	Intravenous injection	Intravenous injection
Approved indications	US: Adults and pediatric patients for on-demand treatment and control of bleeding episodes and perioperative management of bleeding. Routine prophylaxis for adults is only to reduce the frequency of bleeding episodes.EU: Prevention and treatment of hemorrhage or surgical bleeding in adults (age 18 years and older) with VWD, when desmopressin (DDAVP) treatment alone is ineffective or contraindicatedChina: Adult patients for on-demand treatment and control of bleeding episodes and perioperative management of bleeding.	US: Adults and pediatric patients for on-demand treatment and control of bleeding episodes, perioperative management of bleeding, and routine prophylaxis.EU: Prophylaxis and treatment of hemorrhage or surgical bleeding when desmopressin is ineffective or contraindicated.China: NA	US: Adults and pediatric patients for treatment of spontaneous and trauma-induced bleeding episodes and prevention of excessive bleeding during and after surgery.EU: Prophylaxis and treatment of hemorrhage or surgical bleeding when desmopressin is ineffective or contraindicated.China: NA	US: NAEU: Prophylaxis and treatment of hemorrhage or surgical bleeding when desmopressin is ineffective or contraindicated.China: NA

Recombinant furin manufactured in CHO cells, grown in protein-free medium, and purified to a homogenous enzyme preparation (similar conditions as used to produce rVWF).

CHO, Chinese hamster ovary; FVIII, factor VIII; HMW, high molecular weight; RCo, ristocetin cofactor; rVWF, recombinant VWF; ULM, ultra-large multimer; VWD, von Willebrand disease; VWF, von Willebrand factor.

Binding to platelets

In normal human plasma, the ratio of VWF:RCo to VWF:Ag is close to 1. Several studies have consistently shown that rVWF exhibits VWF:RCo to VWF:Ag ratios approaching or even exceeding 1, while pdVWF concentrates typically show ratios below 1.^14,19,22 This finding aligns with the high multimer content of rVWF compared to normal plasma VWF, reflecting its higher potency. Additionally, VWF:GPIbM measurements have yielded higher ratios for rVWF than for pdVWF concentrates.¹⁹

Binding to collagen

VWF:CB activity, measured by ELISA to determine VWF binding to collagen types I and III relative to normal human plasma or chemiluminescence immunoassay (CLIA)-based assay, provides another metric of functional activity.²³ The specific binding activity was calculated as the ratio between VWF:CB and VWF:Ag.²¹ The results showed that the VWF:CB/VWF:Ag ratio was higher for rVWF than for pdVWF, indicating a higher specific activity of rVWF.^14,19

Binding to FVIII

The FVIII binding capacity of rVWF has been shown to be comparable to that of pdVWF (105% vs 109%,¹⁴ 106% vs 100%¹⁹). However, this capacity exceeds that of pdFVIII/VWF concentrates, which typically exhibit values below 100%.^14,15,19

VWF-mediated platelet adhesion to collagen under shear stress

Platelet adhesion to collagen under shear stress (flow conditions) has been assessed using a parallel-plate perfusion chamber.¹⁹ When human whole blood was supplemented with either pdVWF or rVWF to achieve a final VWF:Ag concentration of 1 IU/mL, a time-dependent increase in platelet adhesion to immobilized collagen was observed. Notably, rVWF demonstrated superior efficacy in mediating platelet adhesion to collagen compared to pdVWF concentrates.

Clinical efficacy of rVWF

Phase I studies

In 2013, a phase I, prospective, controlled, randomized, first-in-human clinical study (NCT00816660) was conducted to evaluate the pharmacokinetics (PK) and safety of rVWF in 32 patients with type 3 or severe type 1 VWD who had prior exposure to pdVWF products.²⁴ rVWF was administered at a fixed ratio (1.3:1) with rFVIII and compared with the licensed pdVWF/FVIII (Humate-P, Antihemophilic Factor/VWF Complex (Human)). Dosing for pdVWF-pdFVIII was based on published data, which typically contains a VWF:RCo to FVIII:C ratio of approximately 2:1. The results demonstrated that rVWF exhibited a longer terminal half-life (T_1/2) for both VWF:Ag (25.5 vs 17.9 h) and VWF:RCo (16.3 vs 14.4 h) compared to the plasma-derived product. No safety concerns, particularly regarding thrombotic events, were reported during the study. Furthermore, analysis of the area under the plasma concentration curve (AUC) indicated enhanced stabilization of endogenous FVIII following infusion of the rVWF/rFVIII combination. These findings suggest that rVWF may be administered as monotherapy after achieving therapeutic levels of endogenous FVIII through initial combination infusions. Importantly, in these patients with severe VWD, VWF cleavage products were detected as early as 15 min post-infusion, indicating rapid proteolysis of VWF multimers. However, ULMs, the most hemostatically active forms, were present in samples from rVWF-treated patients for up to 3 h post-infusion, whereas they were undetectable at any post-infusion timepoint in pdVWF-treated patients. This observation suggests that rVWF may provide meaningful primary hemostasis following a short period post-infusion. Overall, this study confirmed the safety and tolerability of rVWF, supporting its further clinical evaluation.

Phase III studies

On-demand setting

A phase III clinical study (NCT01410227)²⁵ was conducted to evaluate the PK, safety, and efficacy of rVWF in the treatment of bleeding episodes in patients with severe VWD. PK was assessed using a randomized cross-over design, aiming to determine the utility of rVWF without the co-administration of rFVIII, which had been required in the phase I study. Across 192 bleeding episodes in 22 patients, hemostatic efficacy was rated as excellent (96.9%) or good (3.1%). A single infusion of rVWF was sufficient to control 81.8% of bleeding episodes, yielding an overall treatment success rate of 100%. The median cumulative dose of rVWF per bleeding episode was 48.2 IU/kg. The PK profile of rVWF was unaffected by the co-administration of rFVIII, with a mean T_1/2 for VWF:RCo of 22.6 h for rVWF alone and 22.5 h for the rVWF:rFVIII combination. Furthermore, FVIII coagulant activity (FVIII:C) increased rapidly within 6 h post-infusion and remained elevated for up to 72 h, indicating that rVWF effectively stabilizes endogenous FVIII. These predictable responses demonstrated that additional rFVIII is generally unnecessary following the initial combined infusion. Notably, no thrombotic events or severe allergic reactions were reported, and no patients developed anti-VWF neutralizing or binding antibodies. These findings support the conclusion that rVWF is safe and effective in treating bleeding episodes in patients with VWD and stabilizes endogenous FVIII:C, potentially eliminating the need for rFVIII after the initial infusion.

Perioperative setting

The efficacy and safety of rVWF in the perioperative setting were evaluated in a phase III prospective, open-label, uncontrolled, non-randomized study involving patients with severe VWD undergoing elective surgery, with or without rFVIII (NCT02283268).²⁶ The study enrolled 15 adult patients: 10 underwent major surgeries, 4 underwent minor surgeries, and 1 underwent oral surgery. All patients had prior exposure to pdVWF. Patients received rVWF at a dose of 40–60 IU/kg 12–24 h before surgery to achieve endogenous FVIII:C levels of at least 30 or 60 IU/dL, depending on the type of surgery. If target FVIII:C levels were reached 3 h prior to surgery, rVWF was administered alone 1–2 h before the procedure. Otherwise, rVWF was co-administered with rFVIII. Excluding PK analyses, 104 surgical infusions were administered, with 89.4% of patients receiving rVWF alone and 10.6% (11 infusions) administered with rFVIII, across five patients. Among these, three patients had type 3 VWD, and two received rFVIII preoperatively despite having FVIII:C levels ⩾ 60 IU/dL. In other cases where rFVIII was administered perioperatively, subtherapeutic FVIII:C levels were not documented. Peak FVIII:C levels were observed within 24 h following rVWF infusion. Hemostatic FVIII:C levels were achieved by 6 h in patients with type 1 and 2 VWD and by 12 h in patients with type 3 VWD, with levels sustained for 72–96 h. Notably, 70% of patients undergoing major surgery received only a single perioperative dose of rVWF. Postoperatively, rVWF was administered as needed over 14 days to maintain target trough levels based on the type of surgery. Hemostatic efficacy, assessed using the same criteria as in the previous phase III trial, was rated as excellent in 73.3% (overall) and 86.7% (intraoperative) of cases, and good in 26.7% and 13.3%, respectively, across all surgical categories (major, minor, and oral). The safety profile was acceptable, with no severe allergic reactions or inhibitory antibodies reported. These findings support the conclusion that rVWF is both effective and well-tolerated in the perioperative management of patients with severe VWD undergoing elective surgery.

Prophylaxis setting

Patients with severe VWD may benefit from rVWF prophylaxis to reduce the frequency of spontaneous BEs requiring VWF treatment. Leebeek et al. conducted a phase III, prospective, open-label, nonrandomized, multi-center study to evaluate the use of rVWF for secondary long-term prophylaxis (NCT02973087).²⁷ All patients were ⩾18 years old and had a baseline VWF:RCo of <20 IU/dL. Patients with a body mass index (BMI) <15 or >40 kg/m² were excluded from the study. A total of 23 patients were enrolled, with 17 completing the study. The majority had type 3 VWD, with some patients having type 1 or type 2 VWD. The study had two arms: the first arm involved patients who were started on rVWF prophylaxis after previously being treated on an OD basis, while the second arm included patients who were switched from prophylaxis with a pdVWF-containing concentrate to rVWF prophylaxis. The starting dose for prophylaxis in patients previously treated on demand was 50 VWF:RCo IU/kg twice weekly. The starting dose for patients in the switch group was based on their prior prophylactic dose of pdVWF-containing concentrate.

The primary outcome measure was the annualized bleeding rate (ABR) for treated spontaneous/non-traumatic bleeding events (sABR). As expected, sABR was significantly reduced in patients previously treated on an OD basis compared to their historical sABR. For these patients, the model-based mean sABR was 6.54 bleeds per year, which decreased to 0.56 after starting twice-weekly rVWF prophylaxis. Remarkably, there was also a reduction in sABR for patients who switched from pdVWF-containing concentrate prophylaxis to rVWF prophylaxis compared to their historical sABR. For patients previously on pdVWF prophylaxis, the model-based mean sABR was 0.51, which decreased to 0.28 after switching to rVWF prophylaxis. In the prior OD group, treated sABR decreased by 91.5% compared to historical sABR, and by 45% in the switch group. No treated spontaneous BEs were recorded in 84.6% (11/13) and 70.0% (7/10) of patients, respectively. The safety profile of rVWF was consistent with the previously established profile, with no new adverse drug reactions identified. Importantly, no venous or arterial thrombotic events were recorded. The study concluded that rVWF prophylaxis effectively reduces treated spontaneous BEs in patients previously receiving OD VWF therapy and maintains at least the same level of hemostatic control in patients switching from pdVWF prophylaxis to rVWF, with a favorable safety profile. As a result of this trial, the U.S. Food and Drug Administration (FDA) approved rVWF for routine prophylaxis in patients with severe VWD.

A recent post hoc analysis of the aforementioned study focused on the efficacy and safety of rVWF prophylaxis in patients with type 3 VWD,²⁸ also incorporating PK and pharmacodynamic (PD) data. The analysis included 18 patients with type 3 VWD, with 10 patients in the prior OD group and 8 patients in the switch group. In the prior OD group, the mean sABR for treated BEs was reduced by 91.6% compared to the mean historical sABR. In the switch group, the mean sABR for treated BEs was reduced by 47%. Overall, the success rate for reducing treated spontaneous ABR in the prior OD group was 90.0%, while treated spontaneous ABR preservation success in the switch group was 87.5%. PK parameters indicated that VWF:RCo activity remained stable throughout the 12-month study period in both groups. In the prior OD group, FVIII:C trough levels increased fivefold from the initial to the final assessments, whereas in the switch group, they remained stable. The safety profile of rVWF prophylaxis in patients with type 3 VWD was consistent with previously reported data. This post hoc analysis demonstrates that rVWF prophylaxis effectively reduces bleeding rates in patients with type 3 VWD who were previously receiving OD VWF therapy and maintains a comparable level of hemostatic control in those who switch from pdVWF prophylaxis to rVWF. Additionally, the analysis provides novel insights into untreated BEs, suggesting the potential underreporting of untreated BEs in real-world settings.

Pediatric on-demand setting

NCT02932618 represents the first pediatric phase III study of rVWF, with the results recently presented at the 2025 International Society on Thrombosis and Haemostasis (ISTH) meeting.²⁹ An open-label study enrolled 25 patients who received at least one dose of rVWF. The cohort comprised 5 patients with Type 1 disease (20%), 9 with Type 2 (36%), and 11 with Type 3 (44%). rVWF was used to treat 104 BEs occurring in 18 patients, with successful outcomes in all participants. A single infusion proved sufficient for 82% of bleeds, while treatment efficacy was rated excellent in 99% of cases. The safety profile was consistent with those of previous reports, and there were no treatment discontinuations due to adverse events. These results suggest that OD treatment with rVWF, with or without additional rFVIII, is both effective and well-tolerated in children with VWD.

Discussion

rVWF is a highly purified therapeutic product produced by a genetically engineered CHO cell line. The cell culture medium used in rVWF production is free of animal or human-derived proteins, eliminating the risk of transmission of human blood-borne pathogens and avoiding the presence of co-purified plasma proteins. Importantly, rVWF is produced without ADAMTS13, the VWF-cleaving protease, making it the only preparation with a defined and consistent amount of intact VWF, including a full spectrum of multimers, such as ULMs. ULMs are the most functionally active forms of VWF, exhibiting superior binding affinity to platelets and subendothelial structures, thus being critical for primary hemostasis. Multimer analysis in several studies has confirmed that rVWF contains high and ULMs absent in human plasma or pdVWF-FVIII concentrates, as demonstrated by low-resolution SDS-PAGE. High-resolution SDS-PAGE further reveals the absence of ADAMTS13-mediated proteolytic fragments in rVWF. In ISTH 2020, Kragh et al. reported that rVWF shares structural and functional similarities with platelet VWF, including comparable activity parameters and multimeric profiles, potentially enhancing hemostatic efficacy compared to pdVWF.²² A comparative table (Table 1) highlights the differences between rVWF and pdVWF,^13,30
–34

Clinical studies, including phase I and phase III trials, consistently show that rVWF exhibits superior functional properties compared to pdVWF concentrates.^24
–28 These advantages appear to correlate with the multimer size, with patients benefiting from the presence of ULMs and the higher purity of rVWF. Biochemical studies have demonstrated that the VWF:RCo/VWF:Ag ratio is higher in rVWF than in pdVWF. No significant difference was observed between highly purified pdVWF control samples used in in vitro experiments and a licensed pdVWF/FVIII concentrate. This finding reflects the high molecular weight (HMW) multimers in rVWF, which bring its specific activity close to or even exceeding the theoretical value of one VWF:RCo/VWF:Ag. Turecek et al. used size-exclusion chromatography to fractionate rVWF by multimer size and demonstrated that VWF:RCo activity is directly dependent on multimeric composition.¹⁴

VWF:RCo assay which measures VWF activity by platelet aggregation in the presence of ristocetin, has been the most widely used functional assay in recent decades.³⁵ The ISTH panel suggests newer assays that measure the platelet-binding activity of VWF, such as VWF:GPIbM and VWF:GPIbR, over the VWF:RCo assay.³⁶ Since rVWF contains a higher proportion of HMW multimers and is the only product containing ULMs, it might be detected with higher sensitivity by the GPIbM reagent, as confirmed by Gritsch.¹⁹ Interestingly, the binding of FVIII to VWF is also influenced by multimer size. Previous research has shown a gradual decrease in FVIII binding capacity with successively smaller molecular weight multimers, with the VWF dimer, the smallest unit, retaining only 20% of the FVIII binding capacity relative to normal human plasma. Each VWF monomer contains one binding site for FVIII, suggesting that, theoretically, each monomer can bind one FVIII molecule,³⁷ meaning that larger multimers can bind more FVIII than smaller ones.

VWF circulates in an inactive globular form and requires sufficient shear force to change its conformation into an extended form, exposing domains critical for collagen and platelet receptor binding.^38,39 The presence of ULMs in rVWF enhances platelet binding under dynamic flow conditions, likely due to the increased number and accessibility of binding sites for collagen and GPIb in the multimers.⁴⁰ The contribution of VWF multimer size to in vitro platelet adhesion under shear force has also been confirmed using a perfusion chamber method, where the degree of platelet adhesion is expressed as a percentage of surface coverage. Results have demonstrated that platelet binding properties depend on the multimeric size of rVWF, with ULMs having a more pronounced effect.⁴¹

Beyond functional advantages, rVWF has demonstrated clinical efficacy with lower doses and fewer infusions. In phase III studies, a single infusion of rVWF effectively controlled 81.8% of bleeding episodes in the OD setting, and 89.4% of perioperative patients were treated successfully with rVWF alone. A French retrospective study showed that fewer infusions (median total infusions: 2 vs 6) and lower doses (overall median surgical dose: 63 vs 220 IU/kg) of rVWF than those used in the phase III trial were sufficient to prevent bleeding in 97% of procedures. However, this difference could be explained by a larger proportion of type 3 VWD in the phase III trial.^26,42 Two studies have shown that rVWF has a longer terminal half-life and slower clearance compared to pdVWF/FVIII.^24,25 A phase I study analyzed post-infusion cleavage of VWF subunits, where the appearance of rVWF fragments cleaved by ADAMTS13 was associated with a progressive decrease in VWF multimeric size.²⁴ Notably, the PK profile of rVWF across studies indicates that it is not influenced by co-administration of rFVIII and is effective in stabilizing endogenous FVIII. FVIII coagulant activity (FVIII:C) increased rapidly within 6 h after rVWF administration and was sustained for up to 72 h post-infusion. Median FVIII:C increased monotonically to a peak of 86.0 U/dL at 24 h after rVWF infusion alone. These predictable responses demonstrate that additional rFVIII is unnecessary in most cases following the initial infusion. As rVWF contains no FVIII, it is particularly valuable for patients with low VWF activity in combination with normal or elevated FVIII activity, where the therapeutic goal is to increase VWF activity without concurrently raising FVIII activity to supra-therapeutic levels.⁴³

Regarding safety, thromboembolic reactions could theoretically occur with rVWF, particularly in patients with thrombotic risk factors. However, clinical trial results suggest that the risk is low. A recent European chart review, which included 91 patients from 13 sites, found that rVWF did not result in any treatment-emergent AEs (including hypersensitivity, thrombotic events, VWF inhibitor development, or transfusion-related infections) in a real-world population, consistent with the safety profile observed in previous clinical trials.⁴⁴ The risk of thrombosis may be higher with pdVWF products because the exogenous FVIII in these products, in addition to the endogenous FVIII stabilized by VWF replacement, could lead to FVIII accumulation in plasma.⁴⁵

rVWF allows for individualized treatment based on patient type, bleeding severity, surgical context, and target factor level requirements. A UK real-world study demonstrated that clinicians were able to adjust doses flexibly according to bleeding severity, patient phenotype, and surgical setting, achieving complete control of all spontaneous or traumatic bleeding with below-label doses. Notably, 75% of cases required no additional FVIII supplementation.⁴⁶ With the accumulation of clinical experience with rVWF, future treatment of VWD is expected to become more precise, safe, and personalized, offering new hope for previously difficult-to-treat subtypes, such as types 2B, 2N, and 2M. In addition to rVWF, several novel therapies are under investigation, including efanesoctocog alfa, rondaptivon pegol, and VGA039.^47
–49

Although this review focuses on the specific challenges and opportunities of rVWF implementation in China, the evidence—drawn from international clinical trials and real-world studies—makes these findings relevant to other regions where rVWF adoption remains limited.

Limitations

Despite its purity advantage and potential for reducing blood-borne infection risks, rVWF has certain limitations in clinical application. First, no randomized controlled trials directly comparing rVWF with pdVWF have been conducted, similar to pdVWF, where head-to-head comparisons of different pdVWF and pdFVIII-VWF concentrates have also not been performed, and existing efficacy evidence is largely based on historical controls or non-comparative studies, like for pdVWF. Additionally, for patients with severe VWD accompanied by low FVIII levels, rVWF, which lacks FVIII, must be co-administered with FVIII during the first infusion. Although rVWF was approved in 2015, its clinical use has been relatively brief compared to pdVWF products, resulting in limited real-world data accumulation. Long-term safety, risk of inhibitor development, and efficacy variations across different VWD subtypes require continued monitoring. Its use in special populations, such as pregnant and lactating women, and its long-term efficacy and safety in children, remain under investigation. Regarding economic burden, although prophylactic treatment with rVWF may reduce lifetime treatment costs compared to pdVWF,⁵⁰ the higher per-dose cost of rVWF compared to pdVWF products may limit accessibility in China's healthcare system, where medical insurance coverage for rare disease therapies is limited. This may hinder the practical translation of its technical advantages.

Conclusion

Following the positive outcomes of phase I and III clinical trials, rVWF received FDA and EMA approval in the United States and Europe. rVWF represents a transformative advancement in VWD therapy, offering a recombinant product with preserved ULMs that deliver superior hemostatic potency and pathogen safety in clinical trials. The approval of rVWF for injection addresses a significant treatment gap in VWD care across the world.

Footnotes

Acknowledgements

Medical writing support for the development of this manuscript under the direction of the authors was provided by Jiaxing Ma from Shanghai Medical Telescope Network Technology Co., Ltd. and funded by Takeda (China) International Trade Co., Ltd. Takeda Pharmaceutical Company Limited provided scientific review of the manuscript.

Declarations

ORCID iD

Renchi Yang

References

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Recombinant von Willebrand factor for von Willebrand disease: mechanism of action and clinical application

Abstract

Keywords

Introduction

Production of rVWF

Features of rVWF

VWF multimer composition analysis

Functional activity

Binding to platelets

Binding to collagen

Binding to FVIII

VWF-mediated platelet adhesion to collagen under shear stress

Clinical efficacy of rVWF

Phase I studies

Phase III studies

On-demand setting

Perioperative setting

Prophylaxis setting

Pediatric on-demand setting

Discussion

Limitations

Conclusion

Footnotes

Acknowledgements

Declarations

ORCID iD

References