Efficacy and Safety of the Factor VIII/von Willebrand Factor Concentrate, Haemate-P/Humate-P: Ristocetin Cofactor Unit Dosing in Patients with von Willebrand Disease

Neurological Complications Associated with Hereditary Bleeding Disorders

PURPOSE OF REVIEW

Hereditary bleeding disorders may have a wide variety of clinical presentations ranging from mild mucosal and joint bleeding to severe central nervous system (CNS) bleeding, of which intracranial hemorrhage (ICH) is the most dreaded complication. In this review, we will discuss the pathophysiology of specific hereditary bleeding disorders, namely, hemophilia A, hemophilia B, and von Willebrand disease (vWD); their clinical manifestations with a particular emphasis on neurological complications; a brief overview of management strategies pertaining to neurological complications; and a review of literature guiding treatment strategies.

RECENT FINDINGS

ICH is the most significant cause of morbidity and mortality in patients with hemophilia. Adequate control of bleeding with the administration of specific factors or blood products, identification of risk factors for bleeding, and maintaining optimal coagulant activity are essential for appropriately managing CNS bleeding complications in these patients. The administration of specific recombinant factors is tailored to a patient's pharmacokinetics and steady-state levels. During acute bleeding episodes, initial factor activity should be maintained between 80 and 100%. Availability of monoclonal antibody Emicizumab has revolutionized prophylactic therapies in patients with hemophilia. Management of ICH in patients with vWD involves using plasma-derived factor concentrates, recombinant von Willebrand factor, and supportive antifibrinolytic agents individualized to the type and severity of vWD. Hemophilia and vWD are the most common hereditary bleeding disorders that can predispose patients to life-threatening CNS complications-intracranial bleeds, intraspinal bleeding, and peripheral nerve syndromes. Early care coordination with a hematologist can help develop an effective prophylactic regimen to avoid life-threatening bleeding complications in these patients. Further research is needed to evaluate using emicizumab as an on-demand treatment option for acute bleeding episodes in patients with hemophilia.

Targeting von Willebrand disease: the current status and future directions of management therapies

INTRODUCTION

von Willebrand disease (VWD) is the commonest inherited bleeding disorder, and is typically caused by deficits in the quantity or quality of von Willebrand factor (VWF).

AREAS COVERED

This review describes the main clinical, diagnostic, and therapeutic aspects of VWD, with particular attention to its management. In addition, standard and avant-garde replacement therapies based on the use of VWF are discussed.

EXPERT OPINION

The goal of treatment for VWD is to reverse the double hemostatic defect resulting from the abnormal or reduced expression of VWF and the concomitant factor VIII (FVIII) deficiency. Treatment consists of managing any bleeds and both short-term prophylaxis (i.e. for surgery or invasive procedures) and long-term prophylaxis. While desmopressin is suitable for most patients with type 1 VWD, VWF/FVIII concentrates are the treatment of choice for the other types of VWD. Beside plasma-derived VWF/FVIII concentrates, whose safety and efficacy have been demonstrated by several clinical trials, products containing only VWF, obtained by plasma fractionation and recombinant DNA technology, have become available and marketed more recently. The clinical use of these VWF-only products is particularly attractive in the setting of surgery and long-term prophylaxis, such as the prevention of recurrent gastrointestinal bleeding in cases of angiodysplasia.

Recombinant von Willebrand factor prophylaxis in patients with severe von Willebrand disease: phase 3 study results

International guidelines conditionally recommend long-term prophylaxis in patients with von Willebrand disease (VWD) and severe and frequent bleeding. As recombinant von Willebrand factor (rVWF; vonicog alfa) may reduce the frequency of treated spontaneous bleeding events (BEs), we investigated the efficacy and safety of rVWF prophylaxis in adults with severe VWD. Patients with BEs requiring VWF therapy in the past year (on-demand VWF therapy [prior on-demand group] or plasma-derived VWF prophylaxis [pdVWF; switch group]) were enrolled in a prospective, open-label, nonrandomized, phase 3 study. The planned duration of rVWF prophylaxis was 12 months; starting rVWF dose was 50 ± 10 VWF: ristocetin cofactor (VWF:RCo) IU/kg twice weekly (prior on-demand group) or based on prior pdVWF weekly dose/dosing frequency (switch group). The primary endpoint was annualized bleeding rate (ABR) of treated spontaneous BEs (sABR) during rVWF prophylaxis. Over the 12-month study period, treated sABR decreased by 91.5% on-study vs historical sABR in 13 patients in the prior on-demand group, and by 45.0% in 10 patients in the switch group (model-based analysis ratio, 0.085; 95% confidence interval [CI], 0.021-0.346 and 0.550; 95% CI, 0.086-3.523, respectively). 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. Findings suggest that rVWF prophylaxis can reduce treated spontaneous BEs in patients previously receiving on-demand VWF therapy and maintains at least the same level of hemostatic control in patients who switch from prophylaxis with pdVWF to rVWF, with a favorable safety profile. This trial was registered at www.clinicaltrials.gov (#NCT02973087) and www.clinicaltrialsregister.eu (#EudraCT 2016-001478-14).

Outcomes of long-term von Willebrand factor prophylaxis use in von Willebrand disease: A systematic literature review

BACKGROUND

Von Willebrand Disease (VWD) is a common inherited bleeding disorder. Patients with VWD suffering from severe bleeding may benefit from the use of secondary long-term prophylaxis.

AIM

Systematically summarize the evidence on the clinical outcomes of secondary long-term prophylaxis in patients with VWD and severe recurrent bleedings.

METHODS

We searched Medline and EMBASE through October 2019 for relevant randomized clinical trials (RCTs) and comparative observational studies (OS) assessing the effects of secondary long-term prophylaxis in patients with VWD. We used Cochrane Risk of Bias (RoB) tool and the RoB for Non-Randomized Studies of interventions (ROBINS-I) tool to assess the quality of the included studies. We conducted random-effects meta-analyses and assessed the certainty of the evidence using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) approach.

RESULTS

We included 12 studies. Evidence from one placebo controlled RCT suggested that VWD prophylaxis as compared to no prophylaxis reduced the rate of bleeding episodes (Rate ratio [RR], .24; 95% confidence interval [CI], .17-.35; low certainty evidence), and of epistaxis (RR, .38; 95%CI, .21-.67; moderate certainty evidence), and may increase serious adverse events RR 2.73 (95%CI .12-59.57; low certainty). Evidence from four before-and-after studies in which researchers reported comparative data suggested that VWD prophylaxis reduced the rate of bleeding (RR .34; 95%CI, .25-.46; very low certainty evidence).

CONCLUSION

VWD prophylaxis treatment seems to reduce the risk of spontaneous bleeding, epistaxis, and hospitalizations. More RCTs should be conducted to increase the certainty in these benefits.

Clinical Efficacy and Safety of Fanhdi®, a Plasma-Derived VWF/Factor VIII Concentrate, in von Willebrand Disease in Spain: A Retrospective Study

Objective

To evaluate the efficacy and safety of a plasma-derived factor VIII concentrate containing von Willebrand Factor (pdVWF/FVIII) in standard clinical practice in von Willebrand Disease (VWD) patients.

Methods

A retrospective, multicentric, observational study of VWD patients treated with Fanhdi^®, a pdVWF/FVIII concentrate, from January 2011 to December 2017 was conducted at 14 centers in Spain. Efficacy and safety were evaluated for acute bleeding episodes, for prevention of bleeding in surgeries, and for secondary long-term prophylaxis.

Results

Seventy-two eligible patients, type 1, 2, 3 VWD (25%/38.9%/36.1%) were treated for spontaneous and traumatic bleeding (140 episodes, n = 41 patients), to prevent surgical bleeding (69 episodes, n = 43 patients); and for secondary long-term prophylaxis (18 programs, n = 13 patients). Replacement therapy with pdVWF/FVIII showed an excellent to good clinical efficacy in 96.7% of the bleeding episodes, 100% during surgical procedures and 100% during prophylaxis. No adverse events (AEs), nor serious AEs related to the product were observed.

Conclusions

Fanhdi^® was effective, safe and well tolerated in the management of bleeding episodes, the prevention of bleeding during surgeries, and for secondary long-term prophylaxis in VWD patients.

Prophylactic management of patients with von Willebrand disease

Von Willebrand disease, the most common inherited bleeding disorder that affects both males and females, is due to quantitative or qualitative defects of the multimeric glycoprotein von Willebrand factor, which cause mucous membrane bleeding but also soft tissue bleeding owing to the secondary deficiency of factor VIII. The aim of treatment is to correct this dual defect of hemostasis. In addition to the episodic management of bleeding episodes, therapy includes their short- or long-term prevention. Short-term prophylaxis is mainly warranted in order to provide effective hemostatic coverage to patients undergoing surgery or invasive procedures and to affected women at the time of delivery or during menstruations associated with excessive bleeding. The aim of long-term prophylaxis is to prevent bleeding in particular categories of patients at increased risk of frequent and spontaneous bleeding in the joints, nose, and gastrointestinal tract.

Gene Therapy for Inherited Bleeding Disorders

Decades of preclinical and clinical studies developing gene therapy for hemophilia are poised to bear fruit with current promising pivotal studies likely to lead to regulatory approval. However, this recent success should not obscure the multiple challenges that were overcome to reach this destination. Gene therapy for hemophilia A and B benefited from advancements in the general gene therapy field, such as the development of adeno-associated viral vectors, as well as disease-specific breakthroughs, like the identification of B-domain deleted factor VIII and hyperactive factor IX Padua. The gene therapy field has also benefited from hemophilia B clinical studies, which revealed for the first time critical safety concerns related to immune responses to the vector capsid not anticipated in preclinical models. Preclinical studies have also investigated gene transfer approaches for other rare inherited bleeding disorders, including factor VII deficiency, von Willebrand disease, and Glanzmann thrombasthenia. Here we review the successful gene therapy journey for hemophilia and pose some unanswered questions. We then discuss the current state of gene therapy for these other rare inherited bleeding disorders and how the lessons of hemophilia gene therapy may guide clinical development.

ASH ISTH NHF WFH 2021 guidelines on the management of von Willebrand disease

BACKGROUND

von Willebrand disease (VWD) is a common inherited bleeding disorder. Significant variability exists in management options offered to patients.

OBJECTIVE

These evidence-based guidelines from the American Society of Hematology (ASH), the International Society on Thrombosis and Haemostasis (ISTH), the National Hemophilia Foundation (NHF), and the World Federation of Hemophilia (WFH) are intended to support patients, clinicians, and health care professionals in their decisions about management of VWD.

METHODS

ASH, ISTH, NHF, and WFH formed a multidisciplinary guideline panel. Three patient representatives were included. The panel was balanced to minimize potential bias from conflicts of interest. The University of Kansas Outcomes and Implementation Research Unit and the McMaster Grading of Recommendations Assessment, Development and Evaluation (GRADE) Centre supported the guideline development process, including performing and updating systematic evidence reviews (through November 2019). The panel prioritized clinical questions and outcomes according to their importance to clinicians and patients. The panel used the GRADE approach, including GRADE Evidence-to-Decision frameworks, to assess evidence and make recommendations, which were subject to public comment.

RESULTS

The panel agreed on 12 recommendations and outlined future research priorities.

CONCLUSIONS

These guidelines make key recommendations regarding prophylaxis for frequent recurrent bleeding, desmopressin trials to determine therapy, use of antiplatelet agents and anticoagulant therapy, target VWF and factor VIII activity levels for major surgery, strategies to reduce bleeding during minor surgery or invasive procedures, management options for heavy menstrual bleeding, management of VWD in the context of neuraxial anesthesia during labor and delivery, and management in the postpartum setting.

Analysis of current perioperative management with Haemate® P/Humate P® in von Willebrand disease: Identifying the need for personalized treatment

INTRODUCTION

Patients with Von Willebrand disease (VWD) are regularly treated with VWF-containing concentrates in case of acute bleeding, trauma and dental or surgical procedures.

AIM

In this multicentre retrospective study, current perioperative management with a von Willebrand factor (VWF)/Factor VIII (FVIII) concentrate (Haemate^® P) in patients with VWD was evaluated.

PATIENTS/METHODS

Patients with VWD undergoing minor or major surgery between 2000 and 2015, requiring treatment with a VWF/FVIII concentrate (Haemate^® P), were included. Achieved VWF activity (VWF:Act) and FVIII during FVIII-based treatment regimens were compared to predefined target levels in national guidelines.

RESULTS

In total, 103 patients with VWD (148 surgeries) were included: 54 type 1 (73 surgeries), 43 type 2 (67 surgeries) and 6 type 3 (8 surgeries). Overall, treatment resulted in high VWF:Act and FVIII levels, defined as ≥0.20 IU/mL above predefined levels. In patients with type 1 VWD, respectively, 65% and 91% of trough VWF:Act and FVIII levels were higher than target levels. In patients with type 2 and type 3 VWD, respectively, 53% and 57% of trough VWF:Act and 72% and 73% of trough FVIII levels were higher than target level. Furthermore, FVIII accumulation over time was observed, while VWF:Act showed a declining trend, leading to significantly higher levels of FVIII than VWF:Act.

CONCLUSION

High VWF:Act and accumulation of FVIII were observed after perioperative FVIII-based replacement therapy in patients with VWD, both underlining the necessity of personalization of dosing regimens to optimize perioperative treatment.

Haemophilia B: impact on patients and economic burden of disease

Worldwide, haemophilia is the most common hereditary bleeding disorder. The incidence of haemophilia B, however, is considerably less than haemophilia A and consequently appears to have received less attention in the research literature. This article aims to summarise the available evidence documenting the patient and economic burden associated with haemophilia B and current methods of disease management. Both the immediate and long-term clinical consequences of haemophilia B can have significant implications for patients in terms of functional limitations and diminished health-related quality of life (HRQOL). Evidence demonstrates that primary prophylaxis is the optimal strategy for replacing missing clotting factor IX (FIX) and managing haemophilia B. Use of recombinant FIX (rFIX) over plasma-derived FIX (pd-FIX) is also generally preferred for safety reasons. Prophylaxis using currently available rFIX products, however, requires a demanding regimen of intravenous infusions 2–3 times a week which may have significant implications for adherence and ultimately the long-term efficacy of such regimens. Only limited assessments of the cost-effectiveness of prophylactic versus on-demand FIX treatment regimens have been conducted to date. Prophylaxis, however, is generally more costly as greater quantities of FIX are consumed. Any reduction in FIX replacement dosing frequency is expected to improve patient adherence and contribute to improved clinical outcomes, further supporting the costeffectiveness of such interventions. Although a rare disease, as economic constraints for healthcare increase, generating further information regarding the key clinical, patient and economic outcomes associated with haemophilia B will be essential for supporting improvements in care for people with haemophilia B.

Safety of a pasteurized plasma-derived Factor VIII and von Willebrand factor concentrate: analysis of 33 years of pharmacovigilance data

BACKGROUND

Haemate-P/Humate-P (Humate-P) is a pasteurized human plasma-derived concentrate containing both Factor VIII and von Willebrand factor for treatment of hemophilia A and von Willebrand disease (VWD).

STUDY DESIGN AND METHODS

We analyzed the safety of Humate-P based on more than 33 years of postmarketing pharmacovigilance data, representing an estimated exposure of approximately 25,000 patient-years. The analysis comprises reports of potential adverse drug reactions (ADRs) from all sources, reported as part of routine pharmacovigilance at CSL Behring. ADRs considered clinically relevant or potential risks of Humate-P were identified based on defined and standardized Medical Dictionary for Regulatory Activities queries. Recognizing the limitations of spontaneous reporting, we also reviewed the literature, including clinical trials with mandatory reporting.

RESULTS

From 1982 to 2015, a total of 670 postmarketing cases had been reported via pharmacovigilance, for an overall reporting rate of approximately one ADR per 3900 administered standard doses. Of these cases, 343 involved ADRs considered clinically relevant risks (33 thromboembolic complications, 97 inhibitor formation, 110 hypersensitivity or allergic reactions) or potential risks (103 suspected virus transmissions) for Humate-P. Most thromboembolic complications occurred in patients undergoing surgery or with other known risk factors. Inhibitor formation occurred mostly in patients with hemophilia A (24 cases were high titer). Most patients with hypersensitivity or allergic reactions had VWD. None of the reported suspected virus transmission cases were confirmed to be associated with Humate-P. Reported results of company-sponsored studies showed a low incidence of adverse events possibly or probably related to Humate-P.

CONCLUSIONS

More than 33 years of pharmacovigilance data continue to support the safety of Humate-P.

Feasibility of the Von Willebrand disease PREVENT trial

BACKGROUND

Despite treatment, women with von Willebrand disease (VWD) have lower von Willebrand factor (VWF) levels and greater blood loss at delivery than controls. Current weight-based dosing does not account for the ~1.5-fold increase in blood volume in pregnancy.

METHODS

To evaluate the feasibility of a trial to prevent postpartum hemorrhage (PPH), we reviewed pre-pregnancy and 8th month VWF levels in women with VWD with and without PPH following vaginal delivery, assessed VWF concentrate use at delivery by U.S. hemophilia treatment center physician survey, and reviewed thrombosis risk with VWF concentrate by literature review. We determined trial interest and acceptability by structured interviews of physicians and patients. Analysis was by Student's t-test for continuous data, and chi-square or Fisher's exact test for discrete data.

RESULTS

PPH was associated with lower pre-pregnancy VWF:RCo, p<0.005; higher pre-pregnancy, 8th and 9th-month weight, each p<0.001; a family bleeding history, p=0.036; and VWF concentrate treatment, p=0.005. Surveyed physicians reported first-line therapy at delivery was VWF concentrate, at a mean dose 50IU/kg. A trial of a 1.5-fold volume-based dose increase was acceptable to physicians and patients, if it is safe and if costs and visits are minimized. A literature review determined thrombosis risk with VWF concentrate is low, 0.4%.

CONCLUSIONS

This study suggests pre-pregnancy VWF:RCo may predict PPH, but 50-80IU/kg VWF concentrate dosing may not prevent PPH. If pharmacokinetic modeling confirms volume-based dosing achieves VWF levels comparable to pregnant controls, it may be possible to determine if volume-modified VWF concentrate dosing will reduce PPH in VWD.

von Willebrand Disease: A Concise Review and Update for the Practicing Physician

von Willebrand disease (vWD) is the most common inherited disorder of hemostasis and comprises a spectrum of heterogeneous subtypes. Significant advances have been made in understanding von Willebrand factor ( vWF) gene mutations, resultant physiologic deficits in the vWF peptide, and their correlation to clinical presentation. Diagnostic tests for this disorder are complex, and interpretation requires a thorough understanding of the underlying pathophysiology by the practicing physician. The objective of this review is to summarize our current understanding of pathophysiology, laboratory investigations, and evolving treatment paradigm of vWD with the availability of recombinant von Willebrand factor.

Practical aspects of factor concentrate use in patients with von Willebrand disease undergoing invasive procedures: a European survey

INTRODUCTION

The bleeding propensity in von Willebrand disease (VWD) is usually moderate or mild and patients with VWD do not need continuous treatment, but do require extra increased haemostatic cover when undergoing dental or surgical procedures. Desmopressin can be effective in certain patient groups and this has been considered in a previous publication.

AIM

This paper now seeks to evaluate current knowledge and practice in the use of factor concentrate in the management of VWD patients undergoing invasive procedures.

METHODS

A literature search was performed on the use of factor concentrates to cover invasive procedures and a survey of current practice in a number of specialist haematology centres across Europe represented by the European Haemophilia Strategy Board was conducted.

RESULTS

Our review of the literature and the results of the survey showed considerable heterogeneity in treatment regimens, and a lack of consistency in reporting of the variables that determine factor concentrate dosing and monitoring.

CONCLUSION

By analysing the literature, examining guidelines and using consensus deliberation, this survey allowed the group to develop recommendations for management of VWD patients undergoing invasive procedures.

Hemostatic efficacy, safety, and pharmacokinetics of a recombinant von Willebrand factor in severe von Willebrand disease

This phase 3 trial evaluated the safety and hemostatic efficacy of a recombinant von Willebrand factor (rVWF) for treatment of bleeds in severe von Willebrand disease (VWD). rVWF was initially administered together with recombinant factor VIII (rFVIII) and subsequently alone, as long as hemostatic factor VIII activity (FVIII : C) levels were maintained. Pharmacokinetics (PK) were evaluated in a randomized cross-over design (rVWF vs rVWF:rFVIII at 50 IU VWF:ristocetin cofactor activity [RCo]/kg). Bleed control for all treated bleeds (N = 192 bleeds in 22 subjects) was rated good or excellent (96.9% excellent; 119 of 122 minor, 59 of 61 moderate, and 6 of 7 major bleeds) on a 4-point scale (4 = none to 1 = excellent). A single infusion was effective in 81.8% of bleeds. Treatment success, defined as the number of subjects with a mean efficacy rating of <2.5, was 100%. The PK profile of rVWF was not influenced by rFVIII (mean VWF:RCo terminal half-life: 21.9 hours for rVWF and 19.6 hours for rVWF:rFVIII). FVIII : C levels increased rapidly after rVWF alone, with hemostatic levels achieved within 6 hours and sustained through 72 hours after infusion. Eight adverse events (AEs; 6 nonserious AEs in 4 subjects and 2 serious AEs [chest discomfort and increased heart rate, without cardiac symptomatology] concurrently in 1 subject) were associated with rVWF. There were no thrombotic events or severe allergic reactions. No VWF or FVIII inhibitors, anti-VWF binding antibodies, or antibodies against host cell proteins were detected. These results show that rVWF was safe and effective in treating bleeds in VWD patients and stabilizes endogenous FVIII : C, which may eliminate the need for rFVIII after the first infusion. This trial was registered at www.clinicaltrials.gov as #NCT01410227.

Successful aortic aneurysm repair in a woman with severe von Willebrand (type 3) disease

von Willebrand disease type 3 (VWD3) is a rare but the most severe form of von Willebrand disease; it is due to almost complete lack of von Willebrand factor activity (VWF:RCo). It is inherited as autosomal recessive trait; whilst heterozygote carriers have mild, or no symptoms, patients with VWD3 show severe bleeding symptoms. In the laboratory, this is characterised by undetectable VWF:Ag, VWF:RCo, and reduced levels of factor VIII < 0.02 IU/dL. The bleeding is managed with von Willebrand/FVIII factor concentrate replacement therapy. In this rare but challenging case we report on the successful excision and repair of an ascending aortic aneurysm following adequate VWF/FVIII factor concentrate replacement using Haemate-P.

An update on type 2B von Willebrand disease

Type 2B von Willebrand disease (VWD) accounts for fewer than 5% of all VWD patients. In this disease, mutations in the A1 domain result in increased von Willebrand factor (VWF) binding to platelet GPIbα receptors, causing increased platelet clearance and preferential loss of high molecular weight VWF multimers. Diagnosis is complicated because of significant clinical variations even among patients with identical mutations. Platelet transfusion often provides suboptimal results since transfused platelets may be aggregated by the patients' abnormal VWF. Desmopressin may cause a transient decrease in platelet count that could lead to an increased risk of bleeding. Replacement therapy with factor VIII/VWF concentrates is the most effective approach to prevention and treatment of bleeding in type 2B VWD.

Efficacy and safety of Wilate in paediatric VWD patients under 6 years of age - results of a prospective multicentre clinical study including recovery information

Treatment with exogenous von Willebrand factor (VWF) is indicated in patients with von Willebrand disease (VWD) in whom treatment with 1-deamino-8-d-arginine vasopressin/desmopressin is contraindicated. Wilate is a new generation plasma-derived concentrate of native VWF and coagulation factor VIII (FVIII) (in a physiological 1:1 ratio) developed for the treatment of VWD. This is the first study to report safety, efficacy and in vivo recovery (IVR) data from 15 paediatric patients less than 6 years of age who received Wilate for either prophylaxis, on-demand treatment or for treatment in surgical procedures during a prospective open-label trial (VWD type 1: 5, type 2A: 1, type 2B: 2, type 3: 6, unknown type: 1 patients). Analysis of IVR for VWF and FVIII suggested an appropriate and consistent rise in coagulation activity after Wilate administration. Overall efficacy was rated as excellent or good for 99.7% [prophylactic infusions] and 100% [bleeding episodes/surgical procedures]. More than 82% of bleeding episodes resolved after 1 day of treatment, and a Wilate dosage of 20-50 IU kg(-1) was sufficient to achieve haemostasis in 97% of bleeding episodes. All surgical procedures were successfully managed with Wilate. No thromboembolic events were observed during the study, and no patient developed anti-VWF antibodies or FVIII inhibitors. In conclusion, this study confirms both the expected IVR profile in paediatric patients and the excellent efficacy, tolerability and safety profile of Wilate observed previously in adults. Wilate showed excellent efficacy in the treatment of bleeding when used prophylactically or on-demand, and in the treatment of surgical procedures.

Presurgical pharmacokinetic analysis of a von Willebrand factor/factor VIII (VWF/FVIII) concentrate in patients with von Willebrand's disease (VWD) has limited value in dosing for surgery

Optimal doses of von Willebrand Factor/Factor VIII (VWF/FVIII) concentrates for surgical procedures in patients with VWD need to be determined. A prospective, multicenter study was performed that included an initial pharmacokinetic (PK) assessment following a standard dose of VWF/FVIII concentrate (Humate-P®) to determine individual PK parameters and guide therapeutic dosing during surgery. Forty one subjects received 60 IU kg⁻¹ VWF: RCo. Median plasma levels, half-life, mean change from baseline and in vivo recovery (IVR) values were determined for VWF:RCo, VWF:Ag, and FVIII: C, and area under the plasma time-concentration curve (AUC), mean residence time (MRT), clearance, volume of distribution and dose linearity were also assessed for VWF:RCo at various time points. Median baseline VWF:RCo level was 13 IU dL⁻¹ (range, 6-124); with a mean change from baseline >100 IU dL⁻¹ immediately after the infusion, decreasing to 10 IU dL⁻¹ at 48 h postinfusion. The group median incremental in vivo recovery (IVR) for VWF:RCo was 2.4 IU dL⁻¹ per IU kg⁻¹, for VWF:Ag 2.3 IU dL⁻¹ kg⁻¹ and for FVIII:C was 2.7 IU dL⁻¹ per IU kg⁻¹. When analysing individual recovery values on repeated infusions, a very weak correlation was observed between presurgery IVR and IVR for both VWF:RCo and FVIII, measured at various times just prior to and after the surgical procedure. Although group median values were fairly consistent among repeated IVR measurements, the intra-individual IVR values for FVIII and VWF:RCo with repeated infusions showed a large degree of variability. IVR values obtained from pharmacokinetic analyses performed in advance of anticipated surgery do not reliably predict postinfusion circulating levels of VWF:RCo or FVIII attained preoperatively or with subsequent peri-operative infusions.

Von Willebrand factor/factor VIII concentrates in the treatment of von Willebrand disease

Therapy for von Willebrand disease (VWD) aims to restore the hemostatic function conferred by von Willebrand factor (VWF), which facilitates platelet adhesion and aggregation, and serves to increase potentially low coagulation factor VIII (FVIII) in plasma. In patients unresponsive to desmopressin (DDAVP), the preferred treatment is with plasma-derived VWF-containing FVIII concentrates. Only a few of the available VWF/FVIII concentrates have been licensed for use in VWD based on prospective studies. The efficacy of VWF/FVIII concentrates depends on the content and quality of VWF and FVIII. Several studies have demonstrated the variability of the VWF contents, as well as the differences in the VWF multimer patterns (including the high molecular weight VWF multimers that are most effective in restoring hemostasis), among these concentrates. Treating physicians should be aware of these disparities and the potential clinical implications for patients with different VWD subtypes. Dosing has traditionally been calculated based on the FVIII content of the products, although dosing based on VWF functional activity [e.g., VWF ristocetin cofactor activity (VWF:RCo)] addresses the primary protein deficiency in VWD patients. Several clinical studies have demonstrated the efficacy of concentrates dosed according to VWF:RCo. Dosing is generally consistent across VWD subtypes, although patients with severe phenotypes or undergoing major procedures may require more infusions or longer treatment duration. Other considerations for the use of VWF-containing concentrates include laboratory monitoring of efficacy and safety issues such as thrombosis risk and thromboprophylaxis.

Treatment and prevention of acute bleedings in von Willebrand disease--efficacy and safety of Wilate, a new generation von Willebrand factor/factor VIII concentrate

For many patients with von Willebrand disease (VWD), the replacement therapy with von Willebrand factor (VWF)/factor VIII (FVIII) concentrates is the treatment of choice. To evaluate clinical efficacy, safety and tolerability of Wilate, an albumin-free VWF/FVIII concentrate with a ratio of the two haemostatic moieties of approximately 1 to 1, a prospective clinical programme has been designed. The dataset on the treatment and prevention of bleedings is derived from 44 patients (20 males and 24 females) of all VWD types. Thousand and ninety five bleeding episodes were treated with an overall efficacy rating of excellent or good in 96%. The median dose per treatment day was 26 IU FVIII:C per kg. Eighty-one per cent of bleeds were stopped within 1 or 2 days. Gastrointestinal (GI) bleeds needed higher doses (mean 44 IU kg(-1)) and longer treatment (mean 4 days). Efficacy and dosing data from eight children of 12 or less years of age did not differ significantly from the overall study population. Nineteen patients, including six children, were treated prophylactically for more than 3 months (mean 14.8, range 3-46) with a mean prophylactic dose of 27.4 IU kg(-1) and a mean frequency of 1.9 infusions per week. A drop of bleeding frequency from a mean of 4.5 to 1.4 bleeds per month was observed. The overall tolerability was very good. Adverse drug reactions were rare and were mild or moderate in their intensity. The large prospective clinical dataset shows that Wilate is efficacious and safe in the treatment and prevention of haemorrhages in all VWD types in both adult and paediatric patients.

Haemate P von Willebrand factor/factor VIII concentrate: 25 years of clinical experience

Although von Willebrand disease (VWD) has a very long history, our understanding and treatment of the bleeding disorder has only evolved during the past 50 years or so. It was not until the 1920s that VWD was first recognized as a disease separate from that of classical haemophilia. It then took another 30 years before the first effective treatment was developed. Since then, the medical management of VWD has evolved considerably, but not without its ups and downs. One of the key milestones in the evolution of the treatment of VWD was the development of Haemate P/Humate-P (CSL Behring) - the first virus-inactivated factor VIII plasma product. For 25 years, this concentrate has demonstrated excellent clinical efficacy and safety for patients with VWD and for those with haemophilia. This article provides an historical overview of the early landmark efforts to ensure a safe plasma-derived replacement product and outlines the clinical evolution in the use of Haemate P.

Prophylaxis in von Willebrand disease

This paper reviews current issues regarding short-term (i.e. for surgery and invasive procedures) and long-term (i.e. regular infusions to prevent bleeding on a permanent or temporary basis) prophylaxis treatment using replacement concentrates for patients with von Willebrand disease (VWD) who do not respond satisfactorily to desmopressin. The standard treatment of these patients is with factor concentrates containing von Willebrand factor (VWF) and factor VIII (FVIII). When dosing these concentrates, the broad variations in content and quality of VWF as well as the FVIII content in the products should be considered. Peri-operative management strategies will depend on the VWD subtype, baseline VWF and FVIII levels, and size of procedure. FVIII level and VWF ristocetin cofactor activity may both be used to determine concentrate potency and to monitor treatment. Long-term prophylaxis, which has become a state-of-the-art approach in haemophilia, is not very common in VWD. However, more recent data suggest that a substantial number of VWD patients could benefit from prophylactic treatment with VWF-containing concentrates. For example, 35 Swedish VWD patients who required prophylaxis (mainly because of nose/mouth bleeds and joint bleeds) showed a substantial overall reduction in bleeding episodes and there were no signs of arthropathy in children who began prophylaxis before the age of 5 years since initiation of treatment with Haemate P/Humate-P. Studies of prophylaxis in VWD are urgently needed to develop evidence-based guidelines for this approach; the VWD International Prophylaxis study, for example, has commenced by the VWD Prophylaxis Network.

Von Willebrand disease

von Willebrand disease is a common inherited bleeding disorder and many cases are diagnosed in childhood. It has a negative impact on the quality of life of affected individuals; therefore, it is important that the condition be recognized and diagnosed. This article reviews the pathophysiology of the condition, the current classification scheme, and the available treatments, highlighting issues specific to the pediatric population.

Use of Recombinant Factor VIIa in Inherited and Acquired von Willebrand Disease

Recombinant factor VIIa (rFVIIa) is increasingly used outside the labeled indications for the treatment of life-threatening bleeding episodes after failure of respective standard therapy. In this article, the authors focus on the use of the agent in patients with inherited or acquired von Willebrand disease (vWD). Although the current experience is sparse, published cases indicate the high efficacy of rFVIIa for the treatment of patients refractory to conventional treatment. The agent may be used in patients with congenital vWD complicated by alloantibodies directed against substituted von Willebrand factor or in the presence of concomitant hemostatic defects as well as acquired vWD with hitherto limited therapeutic options. Controlled clinical studies are necessary to define the use of rFVIIa in this clinical setting.

Treatment of urgent bleeding in von Willebrand disease

von Willebrand factor (VWF) is a complex plasma protein that promotes platelet adhesion to the subendothelial matrix of injured blood vessels and provides stability to factor VIII in the circulation. von Willebrand disease (VWD) is a haemorrhagic disorder of highly variable severity caused by qualitative and quantitative abnormalities of VWF. The approach to treating urgent bleeding in patients with VWD is dependent on an accurate diagnosis of the patient's type of VWD and knowledge of the expected responses to treatment modalities. These include administration of desmopressin (DDAVP), a vasopressin analogue that promotes the release of VWF and factor VIII (FVIII) from storage sites, and replacement therapy with a viral-inactivated concentrate containing normal VWF and FVIII. Monitoring of an individual's response in the non-bleeding state is required to determine the response to desmopressin that may be achieved and to determine the individual pharmacokinetics of infused VWF and FVIII. In this article, specific approaches to the choice of treatment modalities, calculation of dosages, monitoring of therapy, possible side effects and complications of the treatment of the various types of VWD will be discussed.

Human Plasma von Willebrand Factor/Factor VIII Complex (Haemate?? P/Humate-P??)

Haemate P/Humate-P is a pasteurised human plasma-derived concentrate containing coagulation factor VIII and a near-normal spectrum of von Willebrand factor multimers, including high-molecular weight multimers, for intravenous use in patients with von Willebrand disease or haemophilia A. Extensive clinical experience over the past 25 years has shown that Haemate P/Humate-P provides effective haemostatic control for the prevention and treatment of bleeds in patients with these conditions, with no confirmed cases of viral or prion transmission occurring during this time. In small prospective and retrospective noncomparative studies, Haemate P/Humate-P provided effective haemostatic control for the prevention and treatment of bleeding episodes in the vast majority of paediatric and adult patients with von Willebrand disease. Haemate P/Humate-P was generally well tolerated in patients with von Willebrand disease or haemophilia A.

Management of von Willebrand disease with factor VIII/von Willebrand factor concentrates: results from current studies and surveys

Until the mid 1980s, cryoprecipitate had been the mainstay of treatment of patients with von Willebrand disease (VWD) who were unresponsive to desmopressin. The advent of virally inactivated factor VIII/von Willebrand factor (FVIII/VWF) concentrates, originally developed for the treatment of patients with hemophilia, provided improved therapy for VWD. These products were therefore introduced in clinical practice in most European hemophilia centers; one concentrate (Humate-P) was approved for management of VWD in the USA. The 1980s saw the first clinical studies of FVIII/VWF concentrates in patients with VWD, but a standardized procedure for ex vivo effects of these virus-inactivated plasma concentrates in VWD patients became available only in 1992. Study results have shown that the commercially available VWF-containing concentrates are effective in clinical practice (bleeding and surgery), producing responses that may differ depending on the patient's VWD subtype; infusion results in correction of factor VIII activity (FVIII:C) and ristocetin cofactor activity of VWF (VWF:RCo), whereas bleeding time is not consistently corrected. Several studies have demonstrated that FVIII/VWF concentrates have variable VWF multimer patterns relative to normal human plasma. New products should be validated by current methodologies before introduction in clinical practice. Data on several intermediate-purity and high-purity FVIII/VWF concentrates have been reported, and a large prospective study of an intermediate-purity FVIII/VWF concentrate (Haemate P/Humate-P) is currently in progress. In the latter study, for the first time, the appropriate dosage to prevent bleeding during surgery is being calculated on the basis of scheduled pharmacokinetic assessments in each patient. Although thrombotic events are rare in patients with VWD receiving repeated infusions of FVIII/VWF concentrates, there is some concern that sustained high concentrations of FVIII:C may increase the risk of postoperative venous thromboembolism. On the basis of these observations, the dosage and timing of FVIII/VWF administration should be planned to keep FVIII:C concentrations between 50 U/dl and 150 U/dl in the postoperative period.

Pharmacokinetic studies on Wilfactin, a von Willebrand factor concentrate with a low factor VIII content treated with three virus-inactivation/removal methods

OBJECTIVE

In order to correct the primary von Willebrand factor (VWF) defect and avoid supra-physiologic plasma levels of factor VIII, a pure VWF concentrate almost devoid of FVIII was developed and used in France since 1989.

METHODS

The pharmacokinetic (PK) profile of the most recent version of this concentrate (Wilfactin; LFB, Les Ulis, France), treated with three virus-inactivation/removal methods (solvent/detergent, 35 nm filtration, dry heat treatment), was investigated in 25 patients. Seventeen patients with various types of clinically severe von Willebrand disease (VWD) were included in a crossover, randomized trial carried out in five European centers and comparing Wilfactin with concentrates containing both FVIII and VWF (FVIII/VWF). Eight type 3 VWD patients were included in another trial carried out in six French centers comparing Wilfactin with its previous version (Facteur Willebrand-LFB; LFB) that adopted one virus-inactivation method only.

RESULTS

For both the measurements evaluated in this study (VWF antigen, VWF:Ag; and VWF ristocetin co-factor activity, VWF:RCo), Wilfactin had a PK profile similar to that of the FVIII/VWF concentrates and of Facteur Willebrand-LFB. VWF:RCo and VWF:Ag recoveries were 2.1 +/- 0.3 and 1.8 +/- 0.3 per IU kg(-1), respectively, and the half-lives were 12.4 +/- 1.8 and 15.9 +/- 1.5 h. The FVIII synthesis rate was 5.8 +/- 1.0 IU dL(-1) h(-1), with a half-life of 15.8 +/- 2.4 h.

CONCLUSION

The PK of VWF and FVIII have not been altered by the three virus-inactivation/removal steps during the manufacturing of Wilfactin.

Treatment of von Willebrand disease

The bleeding tendency in von Willebrand disease (VWD) is heterogeneous and some patients with the mildest form of the disease have no significant bleeding symptoms throughout their lives. In some cases, the most difficult task for a clinician is to decide whether any treatment is actually required. However, cases with moderate to severe factor VIII (FVIII) and von Willebrand factor (VWF) deficiency usually require treatment to stop or prevent bleeding. Increasing autologous FVIII/VWF by desmopressin administration or providing normal allogeneic VWF through the infusion of plasma-derived concentrates can correct FVIII and VWF deficiencies and normalize or shorten bleeding time (BT). FVIII levels are the best predictors of soft tissue or surgical bleeding, while BT normalization, reflecting the correction of platelet-dependent functions of VWF, is considered a reliable indicator of an effective treatment of mucosal bleeding. Recombinant concentrates of FVIII are not indicated (apart from cases with alloantibodies against exogenous VWF), since they are devoid of VWF and lack its stabilizing effect on circulating FVIII. A very-high-purity concentrate of VWF has recently been made available, but its advantages over conventional concentrates containing both FVIII and VWF moieties are not obvious. The best way to select the appropriate treatment is to perform a test infusion with desmopressin in any patient with clinically significant VWD, provided that he/she has no contraindication to the compound or belongs to subtype with an anticipated lack of response (for example, type 3 VWD with FVIII/VWF lower than 5%).

Diagnosis and treatment of von Willebrand disease

Von Willebrand disease (VWD) is the most common bleeding disorder; it is believed to occur in approximately 1% to 2% of the population. Mucocutaneous and surgical hemorrhage in affected individuals is caused by quantitative and qualitative defects in von Willebrand factor (VWF), a large, multimeric protein that supports platelet adhesion and aggregation in the initiation of hemostasis at the time of vascular injury and functions as a carrier protein for factor VIII in the circulation. Advances in cellular and molecular biology have led to improved understanding of the pathophysiology of the disorder and development of a classification scheme that is based on quantitative and qualitative defects. Effective treatment is dependent on an accurate diagnosis using specific assays of VWF that define the various defects.