Pharmacokinetics and hemostatic effect of different factor VIII/von Willebrand factor concentrates in von Willebrand's disease type III

Characterization of protein unable to bind von Willebrand factor in recombinant factor VIII products

BACKGROUND

Therapeutic products with coagulation factor VIII (FVIII) have a wide range of specific activities, implying presence of protein with altered structure. Previous studies showed that recombinant FVIII products (rFVIII) contain a fraction (FVIIIFT ) unable to bind von Willebrand factor (VWF) and reported to lack activity. Because of loss of function(s), FVIIIFT can be defined as a product-related impurity, whose properties and levels in rFVIII products should be investigated.

OBJECTIVE

To isolate and characterize the FVIIIFT fraction in rFVIII products.

METHODS

Protein fractions unable (FVIIIFT ) and able (FVIIIEL ) to bind VWF were isolated from rFVIII products using immobilized VWF affinity chromatography (IVAC) and characterized by gel electrophoresis, immunoblotting, FVIII activity test, surface plasmon resonance, mass spectrometry, and for plasma clearance in mice.

RESULTS AND CONCLUSIONS

A robust IVAC methodology was developed and applied for analysis of 10 rFVIII products marketed in the United States. FVIIIFT was found at various contents (0.4%-21.5%) in all products. Compared with FVIIIEL , FVIIIFT had similar patterns of polypeptide bands by gel electrophoresis, but lower functional activity. In several representative products, FVIIIFT was found to have reduced sulfation at Tyr1680, important for VWF binding, decreased interaction with a low-density lipoprotein receptor-related protein 1 fragment, and faster plasma clearance in mice. These findings provide basic characterization of FVIIIFT and demonstrate a potential for IVAC to control this impurity in rFVIII products to improve their efficacy in therapy of hemophilia A.

Simoctocog alfa for the treatment of hemophilia A

INTRODUCTION

Hemophilia A is the most frequent inherited bleeding disorder and most challenging coagulation disorder. To combat this, a number of new improved rFVIII/IX concentrates have recently been approved. Some of them are derived from protein fusion biotechnology or pegylation to extend their half-life (HL). However, prophylaxis has become a standard of care to prevent arthropathy in hemophiliacs though the need of frequent venipunctures is a major obstacle to primary prophylaxis. The new Extended Half-Life (EHL) rFIX concentrates allow increased intervals, while the improved HL of new rFVIII was moderate. rFVIII Simoctocog alfa is produced in Human Embryonic Kidney (HEK) cells and the post-translational modifications performed by HEK cells are very similar to those occurring in the native FVIII. Areas covered: Herein, the author provides a review of simoctocog alfa with its contents including information on simoctocog alfa's manufacturing, clinical trials, safety and tolerability. They also give their expert opinion and future perspectives on this therapy. Expert opinion: An important advantage of simoctocog alfa is the possibility to omit at least 30% of venipunctures with prophylaxis. Consequently, the standard three times weekly bolus administrations may be reduced to twice weekly, meaning approximately 50 fewer venipunctures per year. This may be particularly helpful to children.

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.

The History of Clotting Factor Concentrates Pharmacokinetics

Clotting factor concentrates (CFCs) underwent tremendous modifications during the last forty years. Plasma-derived concentrates made the replacement therapy feasible not only in the hospital but also at patients’ home by on-demand or prophylactic regimen. Virucidal methods, implemented soon after hepatitis and AIDS outbreak, and purification by Mabs made the plasma-derived concentrates safer and purer. CFCs were considered equivalent to the other drugs and general rules and methods of pharmacokinetics (PK) were applied to their study. After the first attempts by graphical methods and calculation of In Vivo Recovery, compartment and non-compartment methods were applied also to the study of PK of CFCs. The bioequivalence of the new concentrates produced by means of recombinant DNA biotechnology was evaluated in head-to-head PK studies. Since the beginning, the large inter-patient variability of dose/response of replacement therapy was realized. PK allowed tailoring haemophilia therapy and PK driven prophylaxis resulted more cost effective. Unfortunately, the need of several blood samples and logistic difficulties made the PK studies very demanding. Recently, population PK (PopPK) has been applied to the prediction of CFCs dosing by Bayesian methodology. By PopPK also sparse data may allow evaluating the appropriateness of replacement therapy.

Pharmacokinetics of plasma-derived vs. recombinant FVIII concentrates: a comparative study

Only very few pharmacokinetic (PK) studies comparing plasma derived FVIII (pd-FVIII) against recombinant FVIII (rFVIII) concentrates are available. The studies have been generally conducted to demonstrate the bioequivalence of a new product with an old one. The switch from a plasma-derived FVIII (pd-FVIII) to a rFVIII concentrate is a good moment to enrol the patients in a comparative PK study. To achieve information on the PK characteristics of two different classes of FVIII concentrates, according to two different designs: a 10 FVIII concentration/time point design and a reduced 4-point design. A single dose PK comparing pd- and rFVIII concentrates has been performed in four Haemophilia Centres of Italy. Seventeen haemophilia A patients underwent two subsequent single dose PK studies at the moment of switching. Two-compartment- and Non-compartment-analysis did not show significant differences between the outcomes of PK of pd-FVIII and rFVIII, due to inter-patient variability. In vivo recovery (IVR) of rFVIII was slightly higher than that of pd-FVIII and rFVIII/pd-FVIII AUC ratio was 1.37 in 11/17 patients. The difference is only due to the initial distribution phase because after the first 10 h from the end of the infusion, the two decay curves are overlapping. The elimination half-life of the concentrates was very similar even though a complete bioequivalence was not demonstrated because of a higher AUC of rFVIII concentrates, limited to the distribution phase. The higher Cmax and IVR of rFVIII may be due to the presence of heterodimers activated forms of the recombinant molecules.

Von Willebrand disease: an update in the Aland islands

In the past decades von Willebrand disease (vWD) has, in several respects, fallen into the shadow of classical haemophilia due to all problems that have faced those dealing with congenital bleeding disorders, not least regarding blood-borne diseases. The time has come to revisit and refocus on vWD, probably the most common bleeding disorder. Accordingly, a number of Nordic physicians and scientists working in this field organized a meeting on the ferry boat from Stockholm to Mariehamn, in the Aland islands, the home of the index families with this disease, as described by Erik von Willebrand in 1926. The objective of the meeting was to make a comprehensive survey of vWD as seen from the situation in the Nordic countries. In order to achieve all goals some scientists of note from countries outside the Nordic area were invited as well. This paper gives a summary of the symposium, mainly based on the separate papers published in this issue.

Von Willebrand disease

Long-term prophylaxis is not as well known in Von Willebrand disease (VWD) as in hemophilia but attempts to evaluate prophylaxis scientifically in VWD have started. A few cohort studies have been reported. In an international effort the Von Willebrand disease prophylaxis network (VWD PN) has been formed to investigate the role of prophylaxis in clinically severe VWD (e.g., patients with type 3 VWD) that is nonresponsive to other treatments. Findings from the VWD PN studies will hopefully provide more robust evidence for which patients might best benefit from prophylaxis and for appropriate dosing regimens for prophylaxis in patients with VWD.

von Willebrand's disease: a report from a meeting in the Åland islands

von Willebrand's disease (VWD) is probably the most common bleeding disorder, with some studies indicating that up to 1% of the population may have the condition. Over recent years interest in VWD has fallen compared to that of haemophilia, partly the result of focus on blood-borne diseases such as HIV and hepatitis. Now the time has come to revisit VWD, and in view of this some 60 international physicians with clinical and scientific interest in VWD met over 4 days in 2010 in the Åland islands to discuss state-of-the-art issues in the disease. The Åland islands are where Erik von Willebrand had first observed a bleeding disorder in a number of members of a family from Föglö, and 2010 was also the 140th anniversary of his birth. This report summarizes the main papers presented at the symposium; topics ranged from genetics and biochemistry through to classification of VWD, pharmacokinetics and laboratory assays used in the diagnosis of the disease, inhibitors, treatment guidelines in different age groups including the elderly who often have comorbid conditions that present challenges, and prophylaxis. Other topics included managing surgeries in patients with VWD and the role of FVIII in VWF replacement, a controversial subject.

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.

A systematic overview of the first pasteurised VWF/FVIII medicinal product, Haemate P/ Humate -P: history and clinical performance

Patients with von Willebrand disease (VWD) and haemophilia A (HA) lack, to varying degrees, the von Willebrand factor (VWF) and coagulation factor VIII (FVIII) that are critical for normal haemostasis. These conditions in turn make patients prone to uncontrolled bleeding. Historically, patients with severe forms of VWD or HA were crippled before adulthood and their life expectancy was significantly reduced. Over the past decades, specific coagulation factor replacement therapies including Haemate P, have been developed to help patients achieve and maintain normal haemostasis. Haemate P is a human, plasma-derived VWF/FVIII medicinal product, which was first licensed in Germany in 1981 for the treatment of HA-associated bleeding. It has since then come to be accepted as the gold standard for both the treatment and prophylaxis of bleeding in VWD, especially in cases where desmopressin [1-deamino-8-D-arginine vasopressin (DDAVP)] has been ineffective. Haemate P was the first effectively virus-inactivated (pasteurisation: 60 degrees C for 10 h in aqueous solution) FVIII product, whereby the risk of potentially threatening infective complications of plasma-derived products was reduced. Haemate P was also shown to have a VWF multimer profile remarkably close to that of normal plasma. This bibliographic review presents previously unpublished clinical data of Haemate P, based upon internal clinical study reports of the proprietor, CSL Behring, in addition to data already presented in other publications. The data demonstrate a predictable and well-characterised pharmacokinetic profile, and a proven record of short- and long-term safety, while effectively correcting the haemostatic defects in VWD and HA. Recently available data have also shown Haemate P to be of haemostatic value in exceptional clinical circumstances including surgical interventions. By virtue of its plasma-derived combination of VWF and FVIII, in addition to its high VWF:FVIII content ratio (2.4:1), Haemate P is also associated with successful immune tolerance induction in those patients developing inhibitor antibodies. Although the theoretical risk of thromboembolic complications does exist while receiving Haemate P, as it does with any FVIII replacement therapy, the incidence of such complications has remained notably low. Given the robust data that have accumulated for the use of Haemate P, dosing recommendations are also described in this review; the recommendations are tailored to patient-specific contexts including baseline VWF and FVIII levels in plasma and the type of surgical intervention being undertaken. A wide variety of studies have also provided data on paediatric and geriatric populations, all of which have suggested that Haemate P can be safely and effectively used in a wide variety of clinical circumstances.

Clinical efficacy in bleeding and surgery in von Willebrand patients treated with Fanhdi a highly purified, doubly inactivated FVIII/VWF concentrate

Therapy with factor VIII/von Willebrand factor (FVIII/VWF) concentrate is the mainstay therapy in patients with von Willebrand disease (VWD) unresponsive to desmopressin. There are several commercially available FVIII/VWF concentrates that have been tested in VWD patients. We retrospectively analized the clinical efficacy in bleeding episodes and surgery of a highly purified FVIII/VWF complex with two inactivation steps (Fanhdi) in VWD patients. Sixty patients were included in the study. Treatment schedule consisted of one or more doses (standard dose 40 IU/kg body weight of FVIII) of Fanhdi. One hundred and fifty bleeding episodes were treated. These were: 28 serious bleedings; 92 moderate and 30 mild. An excellent clinical efficacy in almost 95% of cases was observed. Fanhdi was administered during 66 surgical procedures (38 major and 28 minor) with an overall efficacy of 98%. Fanhdi a highly purified, doubly virus-inactivated FVIII/VWF concentrate, with a high content of active VWF and an excellent record of clinical safety, is a valid choice in treating VWD.

Intravenous DDAVP and factor VIII-von Willebrand factor concentrate for the treatment and prophylaxis of bleedings in patients With von Willebrand disease type 1, 2 and 3

The current standard set of von Willebrand factor (VWF) parameters used to differentiate type 1 from type 2 VWD include bleeding times (BTs), factor VIII coagulant activity (FVIII:C), VWF antigen (VWF:Ag), VWF ristocetine cofactor activity (VWF:RCo), VWF collagen binding activity (VWF:CB), ristocetine induced platelet aggregation (RIPA), and analysis of VWF multimers in low and high resolution agarose gels and the response to DDAVP. The BTs and RIPA are normal in asymptomatic carriers of a mutant VWF allele, in dominant type 1, and in recessive type 2N VWD, and this category has a normal response of VWF parameters to DDAVP. The response of FVIII:C is compromised in type 2N VWD. The BTs and RIPA are usually normal in type Vicenza and mild type 2A VWD, and these two VWD variants show a transiently good response of BT and VWF parameters followed by short in vivo half life times of VWF parameters. The BTS are strongly prolonged and RIPA typically absent in recessive severe type 1 and 3 VWD, in dominant type 2A and in recessive type 2C (very likely also 2D) VWD and consequently associated with low or absent platelet VWF, and no or poor response of VWF parameters to DDAVP. The BTs are prolonged and RIPA increased in dominant type 2B VWD, that is featured by normal platelet VWF and a poor response of BT and functional VWF to DDAVP. The BTs are prolonged and RIPA decreased in dominant type 2A and 2U, that all have low VWF platelet, very low VWF:RCo values as compared to VWF:Ag, and a poor response of functional VWF to DDAVP. VWD type 2M is featured by the presence of all VWF multimers in a low resolution agarose gel, normal or slightly prolonged BT, decreased RIPA, a poor response of VWF:RCo and a good response of FVIII and VWF:CB to DDAVP and therefore clearly in between dominant type 1 and 2U. The existing recommendations for prophylaxis and treatment of bleedings in type 2 VWD patients with FVIII/VWF concentrates are mainly derived from pharmocokinetic studies in type 3 VWD patients. FVIII/VWF concentrates should be characterised by labelling with FVIII:C, VWF:RCo, VWF:CB and VWF multimeric pattern to determine their safety and efficacy in prospective management studies. As the bleeding tendency is moderate in type 2 and severe in type 3 VWD and the FVIII:C levels are near normal in type 2 and very low in type 3 VWD patients. Proper recommendations of FVIII/VWF concentrates using VWF:RCo unit dosing for the prophylaxis and treatment of bleeding episodes are proposed and has to be stratified for the severity of bleeding, the type of surgery either minor or major and for type 2 and type 3 VWD as well.

Recombinant versus plasma-derived factor VIII products and the development of inhibitors in previously untreated patients with severe hemophilia A: the CANAL cohort study

It has been suggested that plasma-derived factor VIII products induce fewer inhibitors than recombinant factor VIII products. We investigated the relationship of factor VIII product type and switching between factor VIII products with the risk to develop inhibitors. This multicenter retrospective cohort study included 316 patients with severe hemophilia A born between 1990 and 2000. The outcome was clinically relevant inhibitor development, defined as the occurrence of at least 2 positive inhibitor titers with decreased recovery. The risk of inhibitor development was not clearly lower in plasma-derived compared with recombinant factor VIII products (relative risk [RR], 0.8; 95% confidence interval [CI], 0.5-1.3). Among high-titer inhibitors, the possible reduction in risk was even less pronounced (RR, 0.9; CI, 0.5-1.5). Plasma-derived products with considerable quantities of von Willebrand factor (VWF) carried the same risk for inhibitor development as recombinant factor VIII products (RR, 1.0; CI, 0.6-1.6). Switching between factor VIII products did not increase the risk for inhibitors (RR, 1.1; CI, 0.6-1.8). In conclusion, our findings support neither the notion that plasma-derived factor VIII products with considerable concentrations of VWF confer a lower risk to develop inhibitory antibodies than recombinant factor VIII products, nor that switching between factor VIII product brands increases inhibitor risks in previously untreated patients with severe hemophilia A.

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.

Successful use of recombinant factor VIII devoid of von Willebrand factor during multiple teeth extractions in a patient with type 3 von Willebrand disease

We report a 55-year-old patient with type 3 von Willebrand disease who underwent multiple tooth extractions with successful hemostatic management using recombinant factor VIII. The patient was previously misdiagnosed and treated incorrectly then at 53 years old, he was diagnosed with type 3 von Willebrand disease. As he had avoided dental treatments for two decades due to severe bleeding after dental extraction, multiple severe caries and marginal periodontitis were revealed. The patient refused the use of blood products in hemostatic management because he was afraid of blood-borne diseases and development of anti-von Willebrand factor alloantibodies. After close consultation, we therefore decided to use recombinant factor VIII. Four teeth extraction procedures were executed twice. Before extraction, bolus recombinant factor VIII (50 IU/kg) was administered intravenously followed by continuous infusion (5-10 IU/kg per h) for approximately 48 h. The factor VIII:C level increased from about 1 to 20-32% 30 min after bolus infusion. During continuous infusion (10 IU/kg/h), factor VIII:C was maintained at more than 10%. Little bleeding occurred during and after the multiple teeth extractions and during suture removal. On frequent examinations during a 1-year follow-up, neither von Willebrand factor nor factor VIII inhibitors were detected.

Bleeding prophylaxis for major surgery in patients with type 2 von Willebrand disease with an intermediate purity factor VIII–von Willebrand factor concentrate (Haemate-P)

The parameters to diagnose von Willebrand disease (vWD) include factor VIII coagulant activity (FVIII:C), von Willebrand factor antigen (vWF:Ag), von Willebrand factor ristocetin cofactor activity (vWF:RCo), and von Willebrand factor collagen binding activity (vWF:CB). Type 2 vWD is associated with a moderate bleeding diathesis due to low levels of vWF:RCo and vWF:CB as compared with near normal or normal values for FVIII:C and vWF:Ag. As the factor VIII/von Willebrand factor (vWF) concentrate, Haemate-P, is featured by a vWF:RCo/FVIII:C ratio of about 2.2, the recommended loading dose of 50 U/kg FVIII:C followed by 25 U/kg FVIII:C every 12 h for several days for bleeding prophylaxis in type 2 vWD patients undergoing major surgery demonstrated a predicted significant over-treatment reaching vWF:RCo levels above 2 U/ml. Therefore, we restricted Haemate-P substitution for major surgery to one loading dose of 40-50 U/kg FVIII:C (88-110 U/kg vWF:RCo) followed by 15-20 U/kg FVIII:C (33-44 U/kg vWF:RCo) every 12 h for several days and evaluated this strategy in a prospective pharmacokinetic and efficacy study for bleeding prophylaxis in five type 2 vWD patients. Pre-treatment and peak levels (1 h after Haemate-P loading dose) rose from 0.43-0.66 to 1.5-2.5 U/ml for FVIII:C, from 0.23-0.45 to 1.5-2.5 U/ml for vWF:Ag, from 0.10-< 0.20 to 1.5-2.5 U/ml for vWF:RCo, and from < 0.05-0.10 to 1.0-2.0 U/ml for vWF:CB. Mean in vivo recoveries per transfused IU FVIII:C/kg body weight were 3.2% for FVIII:C, 3.9% for vWF:RCo, and 2.8% for vWF:CB. Mean in vivo recoveries per transfused IU vWF:RCo/kg were 1.45% for FVIII:C, 1.7% for vWF:RCo and 1.25% for vWF:CB. The biological half-life times after transfused Haemate-P were about 12 h for both vWF:RCo and vWF:CB. Based on these pharmacokinetic data, we propose to adapt the loading dose factor VIII/vWF concentrate (Haemate-P) to 60-80 U/kg vWF:RCo followed by 30-40 U/kg vWF:RCo every 12 h for no longer than several days (less than 1 week) for bleeding prophylaxis during major surgery or trauma, and to one loading dose of 40-60 U/kg vWF:RCo for minor surgery, trauma or mucotaneous bleedings in patients with type 2 vWD unresponsive to DDAVP.

A comparative in vitro evaluation of six von Willebrand factor concentrates

The efficacy of von Willebrand factor (VWF) concentrates for treatment of von Willebrand disease (VWD) is dependent on their content of VWF and factor VIII (FVIII).

STUDY OBJECTIVES

To measure the content and quality of VWF and FVIII in six VWF concentrates: Haemate-P (Aventis Behring), Immunate (Baxter Bioscience), Koate (Bayer Corp.), 8Y (BPL), Innobrand (LFB) and Facteur Willebrand (LFB).

METHODS

The VWF antigen content (VWF:Ag), ristocetin cofactor activity (VWF:RCo), collagen-binding activity (VWF:CB), VWF multimers with electrophoresis and densitometry, FVIII activity and total protein content.

RESULTS

Specific activity (VWF:RCo/total protein) varied considerably (4.7-129.5 IU mg(-1)). Activity measures, VWF:RCo and VWF:CB, correlated well, but we found no correlation between any of these and VWF:Ag. The content of high-molecular weight multimer (HMWM) was normal or close to normal in Haemate-P, Innobrand and Facteur Willebrand, moderately reduced in Koate and 8Y, and significantly reduced in Immunate. The HMWM content correlated significantly with the VWF:RCo/VWF:Ag ratio. Only Haemate-P, Innobrand and Facteur Willebrand had VWF:RCo/VWF:Ag ratios >0.7. We found large differences in the content of FVIII and in the FVIII/VWF:RCo ratio. Facteur Willebrand had the lowest (0.02) and Immunate the highest (6.00) ratio.

CONCLUSION

Treating physicians must be aware of the large differences between different VWF concentrates and the potential clinical implications. Concentrates lacking HMWM are probably less efficient for mucosal bleedings. FVIII is most important for surgical bleedings, but concentrates with high FVIII/VWF-ratio may induce very high FVIII levels with increased risk of thrombosis. A low FVIII content may be preferable except in case of acute surgery.

The future of recombinant coagulation factors

Hemophilias A and B are X chromosome-linked bleeding disorders, which are mainly treated by repeated infusions of factor (F)VIII or FIX, respectively. In the present review, we specify the limitations in expression of recombinant (r)FVIII and summarize the bioengineering strategies that are currently being explored for constructing novel rFVIII molecules characterized by high efficiency expression and improved functional properties. We present the strategy to prolong FVIII lifetime by disrupting FVIII interaction with its clearance receptors and demonstrate how construction of human-porcine FVIII hybrid molecules can reduce their reactivity towards inhibitory antibodies. While the progress in improving rFIX is impeded by low recovery rates, the authors are optimistic that the efforts of basic science may ultimately lead to higher efficiency of replacement therapy of both hemophilias A and B.

Clinical efficacy of highly purified, doubly virus-inactivated factor VIII/von Willebrand factor concentrate (Fanhdi) in the treatment of von Willebrand disease: a retrospective clinical study

The goal of therapy in patients with von Willebrand disease (vWD) is to correct the dual defect of primary haemostasis and intrinsic coagulation reflected by low levels of von Willebrand factor (vWF) and factor VIII coagulant activity (FVIII:C). Factor VIII/von Willebrand factor (FVIII/vWF) concentrates are currently the treatment of choice in vWD patients unresponsive to desmopressin (DDAVP). However, only few studies on their clinical use are available so far. The main objective of this study was to retrospectively evaluate the clinical efficacy of a highly purified, doubly virus-inactivated FVIII/vWF concentrate with a high content of FVIII/vWF (Fanhdi). Twenty-two patients with congenital vWD have been treated from 1999 to 2001 at eight specialized centres belonging to the Italian Association of Hemophilia Centers (AICE). Ten males and 12 females, median age 28.5 years, range 5-70 years) had type 3 vWD (six cases), DDAVP-unresponsive type 1 (nine cases) and type 2B (seven cases). The study drug was given to stop or prevent 12 bleeding episodes or to prevent excessive bleeding during 14 surgical or invasive procedures. Overall, replacement therapy with the concentrate showed an excellent to good clinical efficacy in 92% of bleeding episodes and in 93% of surgical procedures. No adverse events occurred during 1,601 infusions, accounting for a total of 304,500 IU of FVIII:C administered. These results confirm the efficacy and safety of this concentrate in the management of bleeding episodes and in the prevention of excessive bleeding during major and minor surgery.

Pharmacokinetics of coagulation factors: clinical relevance for patients with haemophilia

Haemophilia is a recessively inherited coagulation disorder, in which an X-chromosome mutation causes a deficiency of either coagulation factor VIII (FVIII) in haemophilia A, or factor IX (FIX) in haemophilia B. Intravenous administration of FVIII or FIX can be used to control a bleeding episode, to provide haemostasis during surgery or for long term prophylaxis of bleeding. In special cases, activated factor VII (FVIIa) may be used instead of FVIII or FIX. The aim of this work is to review the pharmacokinetics of FVIII, FIX and FVIIa and to give an outline of the use of pharmacokinetics to optimise the treatment of patients with haemophilia. The pharmacokinetics of FVIII are well characterised. The systemic clearance (CL) of FVIII is largely determined by the plasma level of von Willebrand factor (vWF), which protects FVIII from degradation. Typical average CL in patients with normal vWF levels is 3 ml/h/kg, with an apparent volume of distribution at steady state (Vss) that slightly exceeds the plasma volume of the patient, and the average elimination half-life (t1/2) is around 14 hours. There are still some discrepancies in the literature on the pharmacokinetics of FIX. The average CL of plasma-derived FIX seems to be 4 ml/h/kg, the Vss is 3 to 4 times the plasma volume and the elimination t1/2 often exceeds 30 hours. FVIIa has a much higher CL (average of 33 ml/h/kg), and a short terminal t1/2 (at 2 to 3 hours). The Vss is 2 to 3 times the plasma volume. Since the therapeutic levels of coagulation factors are well defined in most clinical situations, applied pharmacokinetics is an excellent tool to optimise therapy. Individual tailoring of administration in prophylaxis has been shown to considerably increase the cost effectiveness of the treatment. Dosage regimens for the treatment of bleeding episodes or for haemostasis during surgery are also designed using pharmacokinetic data, and the advantages of using a constant infusion instead of repeated bolus doses have been explored. The influence of antibodies (inhibitors) on the pharmacokinetics of FVIII and FIX is in part understood, and the doses of coagulation factor needed to treat a patient can tentatively be calculated from the antibody titre. In conclusion, therapeutic monitoring of coagulation factor levels and the use of clinical pharmacokinetics to aid therapy are well established in the treatment of patients with haemophilia.

Advances in the genetics and treatment of von Willebrand disease

von Willebrand disease (VWD) is a bleeding disorder caused by quantitative (type 1 and 3) or qualitative (type 2) defects of von Willebrand factor (VWF). The mechanisms of most inherited VWD types have been recently elucidated by genetic and molecular diagnosis, but the phenotypic tests based on measurements of plasma and platelet VWF, the ability of VWF to interact with its platelet receptor, and the analysis of the multimeric composition of VWF are always essential to identify patients with different VWD subtypes. The aim of treatment is to correct the dual defects of hemostasis, ie, abnormal coagulation expressed by low levels of factor VIII (FVIII) and abnormal platelet adhesion expressed by prolonged bleeding time (BT). Desmopressin is the treatment of choice in most patients with type 1 and type 2 VWD, who account for 60 to 70% of cases. In type 3 and in some severe forms of type 1 and type 2 VWD, desmopressin is not effective, and it is necessary to resort to plasma concentrates containing FVIII and VWF. Treated with virucidal methods, these concentrates are effective and currently safe, but they do not always correct the BT defect. Platelet concentrates or desmopressin can be used as adjunctive treatments when poor correction of the BT after concentrates is associated with continued bleeding.

Treatment of von Willebrand disease with a high-purity factor VIII/von Willebrand factor concentrate: a prospective, multicenter study

Among patients with von Willebrand disease (VWD) who are unresponsive to desmopressin therapy, replacement with plasma-derived concentrates is the treatment of choice. Because prospective studies are lacking, such treatment has been largely empirical. A multicenter, prospective study has been conducted in 81 patients with VWD (15 patients with type 1, 34 with type 2, and 32 with type 3 disease) to investigate the efficacy of a high-purity factor VIII/von Willebrand factor (FVIII/VWF) concentrate for treatment of bleeding and surgical prophylaxis. Two preparations of the concentrate-one virally inactivated with solvent detergent, the other with an additional heat-treatment step--were evaluated. Pharmacokinetic parameters were similar for both preparations. Using pre-established dosages based on the results of pharmacokinetic studies, 53 patients were administered either preparation for the treatment of 87 bleeding episodes, and 39 patients were treated prophylactically for 71 surgical or invasive procedures. Sixty-five (74.7%) and 10 (11.5%) of the bleeding episodes were controlled with 1 or 2 infusions, respectively. Patients with severe type 3 VWD typically required more infusions and higher doses, at shorter time intervals, than did patients with generally milder types 1 and 2. Among patients undergoing surgical procedures, blood loss was lower than that predicted prospectively, and losses exceeding the predicted value did not correlate with the postinfusion skin bleeding time. In conclusion, the concentrate effectively stopped active bleeding and provided adequate hemostasis for surgical or invasive procedures, even in the absence of bleeding time correction.

Cell surface heparan sulfate proteoglycans participate in factor VIII catabolism mediated by low density lipoprotein receptor-related protein

We have demonstrated previously that catabolism of a coagulation factor VIII (fVIII) from its complex with von Willebrand factor (vWf) is mediated by low density lipoprotein receptor-related protein (LRP) (Saenko, E. L., Yakhyaev, A. V., Mikhailenko, I., Strickland, D. K., and Sarafanov, A. G. (1999) J. Biol. Chem. 274, 37685-37692). In the present study, we found that this process is facilitated by cell surface heparan sulfate proteoglycans (HSPGs). This was demonstrated by simultaneous blocking of LRP and HSPGs in model cells, which completely prevented fVIII internalization and degradation from its complex with vWf. In contrast, the selective blocking of either receptor had a lesser effect. In vivo studies of clearance of (125)I-fVIII-vWf complex in mice also demonstrated that the simultaneous blocking of HSPGs and LRP led to a more significant prolongation of fVIII half-life (5.5-fold) than blocking of LRP alone (3.5-fold). The cell culture and in vivo experiments revealed that HSPGs are also involved in another, LRP-independent pathway of fVIII catabolism. In both pathways, HSPGs act as receptors providing the initial binding of fVIII-vWf complex to cells. We demonstrated that this binding occurs via the A2 domain of fVIII, since A2, but not other portions of fVIII or isolated vWf, strongly inhibited cell surface binding of fVIII-vWf complex, and the affinities of A2 and fVIII-vWf complex for the cells were similar. The A2 site involved in binding to heparin was localized to the region 558-565, based on the ability of the corresponding synthetic peptide to inhibit A2 binding to heparin, used as a model for HSPGs.

How I treat patients with von Willebrand disease

Von Willebrand disease (vWD) is a frequent inherited disorder of hemostasis that affects both sexes. Two abnormalities are characteristic of the disease, which is caused by a deficiency or a defect in the multimeric glycoprotein called von Willebrand factor: low platelet adhesion to injured blood vessels and defective intrinsic coagulation owing to low plasma levels of factor VIII. There are 2 main options available for the treatment of spontaneous bleeding episodes and for bleeding prophylaxis: desmopressin and transfusional therapy with plasma products. Desmopressin is the treatment of choice for most patients with type 1 vWD, who account for approximately 70% to 80% of cases. This nontransfusional hemostatic agent raises endogenous factor VIII and von Willebrand factor 3 to 5 times and thereby corrects both the intrinsic coagulation and the primary hemostasis defects. In patients with the more severe type 3 and in most patients with type 2 disease, desmopressin is ineffective or is contraindicated and it is usually necessary to resort to plasma concentrates containing both factor VIII and von Willebrand factor. Concentrates treated with virucidal methods should be preferred to cryoprecipitate because they are equally effective and are perceived as safer. (Blood. 2001;97:1915-1919)

Involvement of low-density lipoprotein receptor-related protein (LRP) in the clearance of factor VIII in von Willebrand factor–deficient mice

Factor VIII is tightly noncovalently linked to von Willebrand factor (vWF) in plasma with a stoichiometry of 1:50, and vWF deficiency results in secondary factor VIII deficiency, with accelerated clearance of factor VIII from the circulation. We used a murine model of severe von Willebrand disease (vWF knockout mice) to study the effect of a recombinant vWF/pro-vWF preparation (rpvWF) on factor VIII survival and to investigate whether low-density lipoprotein receptor-related protein (LRP) might be involved in the in vivo clearance of factor VIII in the absence of vWF. vWF-deficient mice received 70 U/kg rpvWF in the first series of experiments, and in a second series, 80 mg/kg receptor-associated protein (RAP) as a recombinant fusion protein to block the action of LRP. Factor VIII levels were measured at time 0, or 1 or 3 hours after administration of rpvWF or RAP. RAP induced a sustained rise in factor VIII levels comparable to that induced by rpvWF. In a third series, the preadministration of RAP resulted in a slower disappearance of factor VIII antigen (measured by an enzyme-linked immunosorbent assay specific for human factor VIII) after infusion of recombinant factor VIII. These findings suggest that the accelerated clearance of factor VIII seen in the absence of vWF may be a result of the involvement of LRP in factor VIII metabolism.

Role of the low density lipoprotein-related protein receptor in mediation of factor VIII catabolism

In the present study, we found that catabolism of coagulation factor VIII (fVIII) is mediated by the low density lipoprotein receptor-related protein (LPR), a liver multiligand endocytic receptor. In a solid phase assay, fVIII was shown to bind to LRP (K(d) 116 nM). The specificity was confirmed by a complete inhibition of fVIII/LRP binding by 39-kDa receptor-associated protein (RAP), an antagonist of all LRP ligands. The region of fVIII involved in its binding to LRP was localized within the A2 domain residues 484-509, based on the ability of the isolated A2 domain and the synthetic A2 domain peptide 484-509 to prevent fVIII interaction with LRP. Since vWf did not inhibit fVIII binding to LRP, we proposed that LRP receptor may internalize fVIII from its complex with vWf. Consistent with this hypothesis, mouse embryonic fibroblasts that express LRP, but not fibroblasts genetically deficient in LRP, were able to catabolize (125)I-fVIII complexed with vWf, which was not internalized by the cells. These processes could be inhibited by RAP and A2 subunit of fVIII, indicating that cellular internalization and degradation were mediated by interaction of the A2 domain of fVIII with LRP. In vivo studies of (125)I-fVIII.vWf complex clearance in mice demonstrated that RAP completely inhibited the fast phase of the biphasic (125)I-fVIII clearance that is responsible for removal of 60% of fVIII from circulation. Inhibition of the RAP-sensitive phase prolonged the half-life of (125)I-fVIII in circulation by 3.3-fold, indicating that LRP receptor plays an important role in fVIII clearance.

Pharmacokinetics of von Willebrand factor and factor VIII coagulant activity in patients with von Willebrand disease type 3 and type 2

Nine patients with von Willebrand disease type 3, six with type 2B, one with type 2A, and one patient with type 1/2N were infused with one dose of approximately 50 or 100 IU ristocetin cofactor activity (RCoF) per kg body weight of von Willebrand factor (vWF) (Human), a product with a very low content of factor VIII (FVIII). Blood samples were collected over 96 h. The data for RCoF and vWF antigen (vWF:Ag) were fitted to a 1-compartment model decay. The data for FVIII:C were fitted to a model with a linear time 'synthesis' term and a 1-compartment decay. Results in von Willebrand disease type 3 patients (nine patients; 10 infusions) indicated a volume of distribution of 39.9 and 39.8 mL kg-1 for RCoF and vWF:Ag, respectively. The FVIII:C rate of synthesis was 6.4 U dL-1 h-1 (range: 4.4-8.8). The decay rates for FVIII:C, RCoF, and vWF:Ag were 0.041 (h-1) [t1/2: 16.9 h]; 0.061 (h-1) [t1/2: 11.3 h] and 0.006 (h-1) [t1/2: 12.4 h], respectively. In patients with von Willebrand disease type 2 (n = 8) the RCoF mean volume of distribution was 46 mL kg-1. The factor VIIIC mean rate of synthesis was 5.5 U dL-1 h-1 and the decay rate 0.043 (h-1) [t1/2: 16.1 h]. The rate of decay for RCoF and vWF:Ag were 0.050 (h-1) [t1/2: 13.9 h] and 0.044 (h-1) [t1/2: 15.7 h], respectively.

von Willebrand disease: recent advances in pathophysiology and treatment

This review focuses on new developments in the pathophysiology and treatment of von Willebrand disease (vWd). New aspects of the cell biology, gene control, and structure-function correlates of von Willebrand factor (vWf) are reviewed. vWd is more prevalent than previously recognized, affecting up to 1% of the population; this is particularly evident in women's health. Blood group is an important determinant of von Willebrand factor levels; individuals of blood group O tend to have lower plasma levels of vWf than those in other blood groups. Currently available blood tests of vWf quantity and function are discussed, in addition to newer tests undergoing validation. Treatment of classical vWd with desmopressin acetate and plasma derivatives is discussed, as is the potential for intravenous immunoglobulin and corticosteroids in acquired vWd. Special situations, such as the management of vWd in pregnancy, are also discussed.

Why prescribe highly purified factor VIII and IX concentrates?

The aftermath of the HIV catastrophe and hepatitis virus transmission to hemophiliacs has been characterized by continuous efforts to improve the purity of factor VIII and factor IX concentrates, increasing sophistication of the virucidal methods used, and the introduction of recombinant factor VIII. The cost of hemophilia care is substantial and there is a large price difference between products depending on their purity; generally, the purer the concentrate, the higher the price. The use of expensive highly purified concentrates may be questioned if these products are not superior in terms of safety, efficacy or convenience. The properties of concentrates used in hemophilia care are discussed in this review, as are their safety and side effects. The available data do not clearly reveal any clinical difference between factor VIII concentrates, although the highly purified products may be of theoretical benefit. With regard to factor IX, purified products do not seem to carry any risk of the well-known thromboembolic complications which occur in certain situations after treatment with prothrombin complex concentrates.

Increased platelet retention in familial recurrent thrombotic thrombocytopenic purpura

We studied two brothers with recurrent thrombotic thrombocytopenic purpura (TTP). Platelet retention, measured with a modified Adeplat S glass-bead test, was found to be increased during acute episodes of TTP and during remissions. Values of platelet retention ranged between 57 to 95% (normal range 16 to 34%). The continually elevated values enabled us to investigate which fraction of the patients' blood was responsible for the increased platelet retention and to evaluate the effect of different treatments on this parameter. We found that the patients' plasma increased the retention of normal platelets and of platelets taken from a patient with von Willebrand's disease type III. This activity was located in the cryoprecipitate fraction of plasma. Unusually large von Willebrand factor (vWF) multimers were demonstrated in both children during remission and decreased during relapse. Both fresh frozen plasma (FFP) and a commercial factor VIII/vWF concentrate reduced platelet retention when tested during remission. Treatment of both siblings with FFP or factor VIII/vWF concentrate was beneficial during recurrences. We conclude that the elevated platelet retention is due to a factor in the cryoprecipitate of the childrens' plasma, and that both FFP and factor VIII/vWF concentrate are effective in decreasing platelet retention.

Pathogenesis, clinical picture and treatment of von Willebrand's disease

Von Willebrand's disease is probably the most common congenital bleeding disorder, with a prevalence close to 1% in some epidemiological studies. The disease is caused by a quantitative deficiency or a qualitative defect of the von Willebrand factor, which is a multimeric glycoprotein consisting of subunits of 2050 amino acids. The size of multimers ranges from approximately 500 kDa to 20 MDa. Each subunit consist of repeated domain structures. Several functional domains have been identified which can bind such structures as platelet receptors glycoprotein Ib or IIb/IIIA, heparin, collagen or factor VIII. The von Willebrand factor has two main functions in haemostasis, to promote normal platelet adhesion and to be a carrier protein for factor VIII. Von Willebrand's disease is divided into three major types and several subtypes depending on the quantity and quality of the von Willebrand factor in plasma and platelets. A new classification has recently been proposed. Typical symptoms are mucosal bleeding, easy bruising and increased bleeding tendency in connection with tooth extractions and other invasive procedures. Severe cases may have joint bleeding and other haemophilia-like bleeding. Desmopressin is the treatment of choice in mild cases, whereas more severe cases need treatment with factor VIII concentrates.