Perioperative treatment of hemophilia A patients: blood group O patients are at risk of bleeding complications

ESSENTIALS: Targeting of factor VIII values is a challenge during perioperative replacement therapy in hemophilia. This study aims to identify the extent and predictors of factor VIII underdosing and overdosing. Blood group O predicts underdosing and is associated with perioperative bleeding. To increase quality of care and cost-effectiveness of treatment, refining of dosing is obligatory.

SUMMARY

BACKGROUND

Perioperative administration of factor VIII (FVIII) concentrate in hemophilia A may result in both underdosing and overdosing, leading to respectively a risk of bleeding complications and unnecessary costs.

OBJECTIVES

This retrospective observational study aims to identify the extent and predictors of underdosing and overdosing in perioperative hemophilia A patients (FVIII levels < 0.05 IU mL(-1)).

PATIENTS AND METHODS

One hundred nineteen patients undergoing 198 elective, minor, or major surgical procedures were included (median age 40 years, median body weight 75 kg). Perioperative management was evaluated by quantification of perioperative infusion of FVIII concentrate and achieved FVIII levels. Predictors of underdosing and (excessive) overdosing were analyzed by logistic regression analysis. Excessive overdosing was defined as upper target level plus ≥ 0.20 IU mL(-1).

RESULTS

Depending on postoperative day, 7-45% of achieved FVIII levels were under and 33-75% were above predefined target ranges as stated by national guidelines. A potential reduction of FVIII consumption of 44% would have been attained if FVIII levels had been maintained within target ranges. Blood group O and major surgery were predictive of underdosing (odds ratio [OR] 6.3, 95% confidence interval [CI] 2.7-14.9; OR 3.3, 95% CI 1.4-7.9). Blood group O patients had more bleeding complications in comparison to patients with blood group non-O (OR 2.02, 95% CI 1.00-4.09). Patients with blood group non-O were at higher risk of overdosing (OR 1.5, 95% CI 1.1-1.9). Additionally, patients treated with bolus infusions were at higher risk of excessive overdosing (OR 1.8, 95% CI 1.3-2.4).

CONCLUSION

Quality of care and cost-effectiveness can be improved by refining of dosing strategies based on individual patient characteristics such as blood group and mode of infusion.

Efficacy, Safety, and Pharmacokinetics of Beroctocog Alfa in Patients Previously Treated for Hemophilia A

PURPOSE

Beroctocog alfa is a second generation recombinant factor VIII manufactured by removing the B-domain from factor VIII. This prospective clinical trial was conducted to evaluate the efficacy, safety, and pharmacokinetics of beroctocog alfa in patients of ages ≥12 years previously treated for severe hemophilia A.

MATERIALS AND METHODS

Seventy subjects received beroctocog alfa as an on-demand treatment for acute hemorrhage.

RESULTS

The final hemostatic effect was excellent in 35 subjects (50%) and good in 26 subjects (37.1%). The drug showed an overall efficacy rate of 87.1%. The majority of acute hemorrhages was treated by administering the study drug once (86.2%) or twice (10.0%), and the mean dose administered per single infusion was 28.55±6.53 IU/kg. Ten subjects underwent 12 surgical procedures, and hemostatic efficacy was excellent in seven cases (58.3%) and good in five cases (41.7%), showing a 100% efficacy rate. A total of 52 of 88 subjects (59.0%) experienced 168 adverse events. There were 18 serious adverse events (10.7%) in 11 subjects, and two (mild dyspnea and facial edema) in one subject were related to the study drug. Only one subject formed a de novo factor VIII inhibitor, for an occurrence rate of 1.4% (one-sided 95% upper confidence limit: 3.85%). The final elimination half-life was 13.3 h and 12.6 h at baseline and 6 months after administration, respectively.

CONCLUSION

Our results suggest that beroctocog alfa is safe and efficacious as either an on-demand treatment for acute hemorrhage or a surgical prophylaxis in patients with hemophilia A.

Recombinant factor VIII Fc fusion protein for the prevention and treatment of bleeding in children with severe hemophilia A

BACKGROUND

Prophylactic factor replacement, which prevents hemarthroses and thereby reduces the musculoskeletal disease burden in children with hemophilia A, requires frequent intravenous infusions (three to four times weekly).

OBJECTIVE

Kids A-LONG was a phase 3 open-label study evaluating the safety, efficacy and pharmacokinetics of a longer-acting factor, recombinant factor VIII Fc fusion protein (rFVIIIFc), in previously treated children with severe hemophilia A (endogenous FVIII level of < 1 IU dL(-1) [< 1%]).

METHODS

The study enrolled 71 subjects. The starting rFVIIIFc regimen was twice-weekly prophylaxis (Day 1, 25 IU kg(-1) ; Day 4, 50 IU kg(-1) ); dose (≤ 80 IU kg(-1) ) and dosing interval (≥ 2 days) were adjusted as needed. A subset of subjects had sequential pharmacokinetic evaluations of FVIII and rFVIIIFc. The primary endpoint was development of inhibitors (neutralizing antibodies). Secondary endpoints included pharmacokinetics, annualized bleeding rate (ABR), and number of infusions required to control a bleed.

RESULTS

No subject developed an inhibitor to rFVIIIFc. Adverse events were typical of a pediatric hemophilic population. The rFVIIIFc half-life was prolonged relative to that of FVIII, consistent with observations in adults and adolescents. The median ABR was 1.96 overall, and 0.00 for spontaneous bleeds; 46.4% of subjects reported no bleeding episodes on study. Ninety-three per cent of bleeding episodes were controlled with one to two infusions. The median average weekly rFVIIIFc prophylactic dose was 88.11 IU kg(-1) . At study end, 62 of 69 subjects (90%) were infusing twice weekly. Among subjects who had been previously receiving FVIII prophylaxis, 74% reduced their dosing frequency with rFVIIIFc.

CONCLUSION

Twice-weekly infusions with rFVIIIFc were well tolerated and yielded low bleeding rates in children with severe hemophilia A.

Half-life extended factor VIII for the treatment of hemophilia A

Prophylactic infusion of factor VIII (FVIII) prevents joint bleeding and other hemorrhages in patients with hemophilia A. Conventional FVIII concentrates have a short half-life, with an average of about 12 h in adults, ranging in individual patients between 6 and 24 h, and even shorter in younger children. Therefore, effective prophylaxis requires frequent intravenous injection, usually three times per week or every other day. Several technologies are currently under investigation to extend the half-life of FVIII, including Fc fusion (Eloctate, Elocta, efmoroctocog alfa), addition of polyethylene glycol (turoctocog alfa pegol [N8-GP], BAY 94-9027, BAX 855), and a single-chain construct (CSL627). This review summarizes characteristics of products in clinical development and discusses their potential benefits.

Anti-A2 and anti-A1 domain antibodies are potential predictors of immune tolerance induction outcome in children with hemophilia A

BACKGROUND

Hemophilia A (HA) is a congenital bleeding disorder resulting from factor VIII deficiency. The most serious complication of HA management is the appearance of inhibitory antibodies (Abs) against injected FVIII concentrates. To eradicate inhibitors, immune tolerance induction (ITI) is usually attempted, but it fails in up to 30% of cases. Currently, no undisputed predictive marker of ITI outcome is available to facilitate the clinical decision.

OBJECTIVES

To identify predictive markers of ITI efficacy.

METHODS

The isotypic and epitopic repertoires of inhibitory Abs were analyzed in plasma samples collected before ITI initiation from 15 children with severe HA and high-titer inhibitors, and their levels were compared in the two outcome groups (ITI success [n = 7] and ITI failure [n = 8]). The predictive value of these candidate biomarkers and of the currently used indicators (inhibitor titer and age at ITI initiation, highest inhibitor titer before ITI, and interval between inhibitor diagnosis and ITI initiation) was then compared by statistical analysis (Wilcoxon test and receiver receiver operating characteristic [ROC] curve analysis).

RESULTS

Whereas current indicators seemed to fail in discriminating patients in the two outcome groups (ITI success or failure), anti-A1 and anti-A2 Ab levels before ITI initiation appeared to be good potential predictive markers of ITI outcome (P < 0.018). ROC analysis showed that anti-A1 and anti-A2 Abs were the best at discriminating between outcome groups (area under the ROC curve of > 0.875).

CONCLUSION

Anti-A1 and anti-A2 Abs could represent new promising tools for the development of ITI outcome prediction tests for children with severe HA.

The pharmacokinetics of a B-domain truncated recombinant factor VIII, turoctocog alfa (NovoEight®), in patients with hemophilia A

BACKGROUND

Turoctocog alfa (NovoEight(®)) is a human recombinant coagulation factor VIII (rFVIII) for the treatment of patients with hemophilia A.

OBJECTIVES

To evaluate the pharmacokinetics of turoctocog alfa in all age groups across clinical trials.

PATIENTS/METHODS

Data from previously treated patients with severe hemophilia A (FVIII activity level of ≤ 1%) with no history of FVIII inhibitors, in a non-bleeding state, were included. The pharmacokinetics were assessed following a wash-out period and a subsequent single intravenous 50 IU kg(-1) dose of turoctocog alfa. Blood was sampled during a 48-h period postdose. Standard pharmacokinetic (PK) parameters were estimated on the basis of plasma FVIII activity vs. time (PK profiles) with non-compartmental methods. Furthermore, a population PK analysis was conducted.

RESULTS

Data from 76 patients (aged 1-60 years) enrolled globally across six clinical trials were included, totaling 105 turoctocog alfa PK profiles. Single-dose PK results 3-6 months after the first dose of turoctocog alfa were comparable with the results obtained after the first dose. Similar PK characteristics were shown for different lots and strengths of the drug product. Overall, area under the plasma concentration (activity) curve from administration to infinity (AUC) and t1(/2) tended to increase with increasing age, with lower AUC and shorter t(1/2) being seen in children than in adolescents and adults. The PK profiles of turoctocog alfa and other commercially available plasma-derived FVIII and rFVIII products were similar in all age groups.

CONCLUSIONS

The PK characteristics of turoctocog alfa have been thoroughly studied, and shown to be consistent over time, reproducible between different lots and strengths of drug product, and similar to those observed for other FVIII products.

Prophylaxis vs. on-demand treatment with BAY 81-8973, a full-length plasma protein-free recombinant factor VIII product: results from a randomized trial (LEOPOLD II)

BACKGROUND

BAY 81-8973 is a new full-length human recombinant factor VIII product manufactured with technologies to improve consistency in glycosylation and expression to optimize clinical performance.

OBJECTIVES

To demonstrate superiority of prophylaxis vs. on demand therapy with BAY 81-8973 in patients with severe hemophilia A.

PATIENTS/METHODS

In this multinational,randomized, open-label crossover study (LEOPOLD II;ClinicalTrials.gov identifier: NCT01233258), males aged 12–65 years with severe hemophilia A were randomized to twice-weekly prophylaxis (20-30 IU kg(-1)), 3-times-weekly prophylaxis (30-40 IU kg(-1)), or on-demand treatment with BAY 81-8973. Potency labeling for BAY 81-8973 was based on the chromogenic substrate assay or adjusted to the one-stage assay. Primary efficacy endpoint was annualized number of all bleeds (ABR). Adverse events (AEs)and immunogenicity were also assessed.

RESULTS

Eighty patients (on demand, n = 21; twice-weekly prophylaxis, n = 28; 3-times-weekly prophylaxis, n = 31) were treated and analyzed. Mean ± SD ABR was significantly lower with prophylaxis (twice-weekly, 5.7 ± 7.2; 3-times-weekly, 4.3 ± 6.5; combined, 4.9 ± 6.8) vs. on-demand treatment (57.7 ± 24.6; P < 0.0001, ANOVA). Median ABR was reduced by 97% with prophylaxis (twice-weekly, 4.0;3-times-weekly, 2.0; combined, 2.0) vs. on-demand treatment (60.0). Median ABR was higher with twice-weekly vs. 3-times-weekly prophylaxis during the first 6-month treatment period (4.1 vs. 2.0) but was comparable in the second 6-month period (1.1 vs. 2.0). Few patients reported treatment-related AEs (4%); no treatment-related serious AEs or inhibitors were reported.

CONCLUSIONS

Twice weekly or 3-times-weekly prophylaxis with BAY 81-8973 reduced median ABR by 97% compared with on-demand therapy, confirming the superiority of prophylaxis. Treatment with BAY 81-8973 was well tolerated.

Simple estimation procedures for regression analysis of interval-censored failure time data under the proportional hazards model

Interval-censored failure time data occur in many fields including epidemiological and medical studies as well as financial and sociological studies, and many authors have investigated their analysis (Sun, The statistical analysis of interval-censored failure time data, 2006; Zhang, Stat Modeling 9:321-343, 2009). In particular, a number of procedures have been developed for regression analysis of interval-censored data arising from the proportional hazards model (Finkelstein, Biometrics 42:845-854, 1986; Huang, Ann Stat 24:540-568, 1996; Pan, Biometrics 56:199-203, 2000). For most of these procedures, however, one drawback is that they involve estimation of both regression parameters and baseline cumulative hazard function. In this paper, we propose two simple estimation approaches that do not need estimation of the baseline cumulative hazard function. The asymptotic properties of the resulting estimates are given, and an extensive simulation study is conducted and indicates that they work well for practical situations.

Cryoprecipitate therapy

Cryoprecipitate, originally developed as a therapy for patients with antihaemophilic factor deficiency, or haemophilia A, has been in use for almost 50 yr. However, cryoprecipitate is no longer administered according to its original purpose, and is now most commonly used to replenish fibrinogen levels in patients with acquired coagulopathy, such as in clinical settings with haemorrhage including cardiac surgery, trauma, liver transplantation (LT), or obstetric haemorrhage. Cryoprecipitate is a pooled product that does not undergo pathogen inactivation, and its administration has been associated with a number of adverse events, particularly transmission of blood-borne pathogens and transfusion-related acute lung injury. As a result of these safety concerns, along with emerging availability of alternative fibrinogen preparations, cryoprecipitate has been withdrawn from use in a number of European countries. Compared with the plasma from which it is prepared, cryoprecipitate contains a high concentration of coagulation factor VIII, coagulation factor XIII, and fibrinogen. Cryoprecipitate is usually licensed by regulatory authorities for the treatment of hypofibrinogenaemia, and recommended for supplementation when plasma fibrinogen levels decrease below 1 g litre(-1); however, this threshold is empiric and is not based on solid clinical evidence. Consequently, there is uncertainty over the appropriate dosing and optimal administration of cryoprecipitate, with some guidelines from professional societies to guide clinical practice. Randomized, controlled trials are needed to determine the clinical efficacy of cryoprecipitate, compared with the efficacy of alternative preparations. These trials will allow the development of evidence-based guidelines in order to inform physicians and guide clinical practice.

Recombinant factor VIII Fc fusion protein: extended-interval dosing maintains low bleeding rates and correlates with von Willebrand factor levels

BACKGROUND

Routine prophylaxis with replacement factor VIII (FVIII) - the standard of care for severe hemophilia A - often requires frequent intravenous infusions (three or four times weekly). An FVIII molecule with an extended half-life could reduce infusion frequency. The A-LONG study established the safety, efficacy and prolonged pharmacokinetics of recombinant FVIII Fc fusion protein (rFVIIIFc) in previously treated adolescents and adults with severe hemophilia A.

OBJECTIVE

In this post hoc analysis, we investigated the relationship between subjects' prestudy (FVIII) and on-study (rFVIIIFc) regimens.

METHODS

We analyzed two subgroups of subjects: prior prophylaxis and on-study individualized prophylaxis (n = 80), and prior episodic treatment and on-study weekly prophylaxis (n = 16). Subjects' prestudy dosing regimens and bleeding rates were compared with their final rFVIIIFc regimens and annualized bleeding rates (ABRs) in the last 3 months on-study. Dosing regimen simulations based on population pharmacokinetics models for rFVIII and rFVIIIFc were performed.

RESULTS

As compared with their prestudy regimen, 79 of 80 (98.8%) subjects on individualized rFVIIIFc prophylaxis decreased their infusion frequency. Overall ABRs were low, with comparable factor consumption. Longer dosing intervals, including 5-day dosing, were associated with higher baseline von Willebrand factor antigen levels. Simulated dosing regimens predicted a greater proportion of subjects with steady-state FVIII activity trough levels of ≥ 1 IU dL(-1) (1%) with rFVIIIFc than with equivalent rFVIII regimens.

CONCLUSION

These results suggest that patients on rFVIIIFc prophylaxis can reduce their infusion frequency as compared with their prior FVIII regimen while maintaining low bleeding rates, affording more patients trough levels of ≥ 1 IU dL(-1) than with rFVIII products requiring more frequent dosing regimens.

Enhancing the pharmacokinetic properties of recombinant factor VIII: first-in-human trial of glycoPEGylated recombinant factor VIII in patients with hemophilia A

BACKGROUND

N8-GP is a recombinant factor VIII (FVIII) with a site-directed glycoPEGylation for the purpose of half-life prolongation.

OBJECTIVES

To evaluate the safety and pharmacokinetic profiles of N8-GP in comparison with those of the patients' previous FVIII products.

PATIENTS/METHODS

This dose-escalation trial included previously treated patients with severe hemophilia A who received one of three dose levels (25, 50 or 75 U kg(-1) ) of N8-GP and FVIII product. Each dose escalation was preceded by safety and pharmacokinetic assessment. The trial was registered at www.clinicaltrials.gov (NCT01205724).

RESULTS

Twenty-six patients each received one dose of their previous FVIII product followed by the same, single dose of N8-GP. N8-GP, at any tested dose, was well tolerated, with a low frequency of adverse events. No new inhibitors against FVIII or N8-GP and no binding antibodies against N8-GP developed during the trial. The pharmacokinetics of N8-GP were dose-linear. The incremental recovery of N8-GP was 0.025 [(U mL(-1) )/(U kg(-1) )]. The clearance was 1.79 mL(-1)  h(-1)  kg(-1) . The estimated time from dosing of 50 U kg(-1) N8-GP to a plasma activity of 1% was 6.5 days (range: 3.6-7.9 days). The mean terminal half-life of N8-GP was 19.0 h (range: 11.6-27.3 h), 1.6-fold longer than that of the patients' previous products.

CONCLUSIONS

A single dose of up to 75 U kg(-1) N8-GP was well tolerated in patients with hemophilia A, with no safety concerns. N8-GP had a prolonged half-life, and FVIII:C activity remained at > 1% for longer than the patient's previous product. These results indicate that N8-GP has the potential to reduce dosing frequency during prophylaxis.

Musculoskeletal health of subjects with hemophilia A treated with tailored prophylaxis: Canadian Hemophilia Primary Prophylaxis (CHPS) Study

BACKGROUND

Full-dose prophylaxis is very effective at minimizing joint damage but is costly. Tailored prophylaxis has been proposed as a way of reducing costs while still protecting joints.

OBJECTIVE

To report detailed findings in index joints of 56 subjects with severe hemophilia A entered into the Canadian Hemophilia Prophylaxis Study, and treated with tailored prophylaxis, after 13 years.

METHODS

Boys with severe hemophilia A (< 2% factor) and normal joints were enrolled between the ages of 1 and 2.5 years. Initial treatment consisted of once-weekly factor infusions, with the frequency escalating in a stepwise fashion when breakthrough bleeding occurred. During the first 5 years, subjects were examined every 3 months using the modified Colorado Physical Evaluation (PE) scale; subsequently, every 6 months. The Childhood Health Assessment Questionnaire (CHAQ) was administered at each visit.

RESULTS

Median age at study entry was 19 months (range 12-30 months); median follow-up was 92 months (range 2-156). The median PE score was 2, 3 and 3 at ages 3, 6 and 10 years. Persistent findings were related to swelling, muscle atrophy and loss of range of motion. The median score for each of these items (for the six index joints) was 0 at ages 3, 6 and 10 years. The median overall CHAQ score was 0 at ages 3, 6 and 10 years, indicating excellent function.

CONCLUSIONS

Canadian boys treated with tailored primary prophylaxis exhibit minimal joint change on physical examination and minimal functional disability.

Source and purity of factor VIII products as risk factors for inhibitor development in patients with hemophilia A

BACKGROUND

Inhibitor development is influenced by several factors and the type of factor VIII (FVIII) products may play a role.

OBJECTIVES

In order to explore such a role, we designed a cohort study whose novelty resides in the classification of products not only according to the source of FVIII (plasmatic, pd, or recombinant, r) but also to their degree of purity (expressed as specific activity).

PATIENTS/METHODS

Treatment data up to inhibitor development or 150 exposure days were collected in 377 patients with hemophilia A.

RESULTS

Inhibitors developed in 111 patients (29%; 96 high-responders, 25%). The cumulative incidence was progressively higher from patients treated with low/intermediate-purity pdFVIII compared with those treated with high-purity pd and rFVIII. The adjusted hazard ratio of inhibitor development was 4.9 with rFVIII and 2.0 with high-purity pdFVIII (95% CI, 2.9-8.3 and 1.1-4.0), taking as reference low/intermediate-purity pdFVIII. There was no difference in the frequency of inhibitor testing between treatment groups. Sensitivity analyses (in patients who never switched product type, previously untreated patients, those treated on-demand and those with high-risk F8 mutations) confirmed an increased inhibitor risk with rFVIII and high-purity pdFVIII.

CONCLUSIONS

This study shows that the degree of purity of FVIII products influences inhibitor development independently from other risk factors, and emphasizes that differences exist within pdFVIII products.

A randomized comparison of two prophylaxis regimens and a paired comparison of on-demand and prophylaxis treatments in hemophilia A management

BACKGROUND

Prophylaxis with factor (F)VIII is considered the optimal treatment for managing hemophilia A patients without inhibitors.

OBJECTIVES

To compare the efficacy of two prophylaxis regimens (primary outcome) and of on-demand and prophylaxis treatments (secondary outcome), and to continue the evaluation of immunogenicity and overall safety of the ADVATE Antihemophilic Factor (Recombinant), Plasma/Albumin Free Method (rAHF-PFM).

PATIENTS/METHODS

Previously on-demand-treated patients aged 7-59 years (n = 66) with FVIII levels ≤ 2% received 6 months of on-demand treatment and then were randomized to 12 months of either standard (20-40 IU kg(-1) every other day) or pharmacokinetic (PK)-tailored (20-80 IU kg(-1) every third day) prophylaxis, both regimens intended to maintain FVIII trough levels at or above 1%. Efficacy was evaluated in terms of annualized bleeding rates (ABRs). As subjects were first treated on-demand and then on prophylaxis, statistical comparisons between these treatments were paired.

RESULTS

Twenty-two (33.3%) subjects on prophylaxis experienced no bleeding episodes, whereas none treated on-demand were free from an episode of bleeding. ABRs for the two prophylaxis regimens were comparable, whereas differences between on-demand and either prophylaxis were statistically significant (P < 0.0001): median (interquartile range [IQR]) ABRs were 43.9 (21.9), 1.0 (3.5), 2.0 (6.9) and 1.1 (4.9) during on-demand treatment, standard, PK-tailored and any prophylaxis, respectively. There were no differences in FVIII consumption or adverse event rates between prophylaxis regimens. No subject developed FVIII inhibitors.

CONCLUSIONS

The present study demonstrates comparable safety and effectiveness for two prophylaxis regimens and that prophylaxis significantly reduces bleeding compared with on-demand treatment. PK-tailored prophylaxis offers an alternative to standard prophylaxis for the prevention of bleeding.

Providing ABO-identical platelets and cryoprecipitate to (almost) all patients: approach, logistics, and associated decreases in transfusion reaction and red blood cell alloimmunization incidence

BACKGROUND

There are multiple benefits to transfusing only ABO-identical blood components. Historically our institution routinely transfused ABO-nonidentical platelets (PLTs) and cryoprecipitate to surgical patients. In April 2005, we implemented a policy of transfusing only ABO-identical components whenever feasible, regardless of outdating or logistic considerations.

STUDY DESIGN AND METHODS

Technical staff closely monitored product usage and adjusted blood center orders based on recent utilization and planned transfusions. When unable to provide ABO-identical PLTs, ABO-compatible PLTs were washed to remove incompatible plasma. Data on outdating were collected for 18 months before and after implementation. We compared transfusion reaction and red blood cell (RBC) alloimmunization incidence for 4 years preceding (2001-2004) and subsequent (2006-2009) to implementation.

RESULTS

In the year after implementation, only 11 of 410 surgical patients received ABO-nonidentical PLTs (2.7%). There was a 5.6% increase in outdating of PLTs. Transfusing ABO-identical components was associated with significant reductions in febrile (-46%; 8.0 to 4.3 per 10,000 components; p < 0.0001) and allergic transfusion reactions (-23%; from 7.0 to 5.4 per 10,000 components; p = 0.025). A progressive reduction in de novo RBC alloimmunization incidence also occurred (-50% by 2009; p = 0.03).

CONCLUSIONS

Providing ABO-identical PLTs to almost all patients was feasible in our setting by changing ordering and inventorying procedures and making the ABO-identical policy a staff priority. Unexpected and striking reductions in febrile and allergic reactions and RBC alloimmunization were observed, of uncertain causal relationship to this ABO policy change, which will require further study.

Successful immune tolerance induction by FVIII in hemophilia A patients with inhibitor may occur without deletion of FVIII-specific T cells

BACKGROUND

 The development of an inhibitor is the major complication facing patients with hemophilia A treated by administration of factor (F) VIII concentrates. Restoration of tolerance to FVIII can be achieved by prolonged administration of FVIII (immune tolerance induction, ITI). Although ITI has been used for more than 30years in patients with hemophilia A and inhibitor, its mechanism of action is still poorly understood.

OBJECTIVES

 As administration of high doses of antigen can induce the apoptosis of the T cells recognizing the antigen, a potential mechanism of action of ITI may be the deletion of FVIII-specific T cells.

PATIENTS/METHODS

 We studied the CD4+ T-cell response to FVIII in five (one mild, one moderate and three severe) patients successfully desensitized by administration of FVIII and in control subjects.

RESULTS

 Following repeated stimulation with autologous dendritic cells loaded with FVIII, FVIII-specific T oligoclonal cell lines were expanded from the blood of one of the successfully desensitized patients. The FVIII-specific T cells produced IL-5, IL-13 and IL-2. By contrast, FVIII-specific T-cell lines could not be derived from three patients with mild hemophilia A without inhibitor or from four normal control subjects.

CONCLUSIONS

 These data represent the first analysis of the cellular mechanisms regulating the induction of tolerance to FVIII. They demonstrate that successful tolerance induction may occur without deletion of FVIII-specific T cells.

Harmonization of clinical trial guidelines for assessing the risk of inhibitor development in hemophilia A treatment

At the present time, the most significant complication of hemophilia therapy is the development of neutralizing antibodies (inhibitors) to factor (F) VIII, which adds greatly to the difficulty and expense of preventing and treating bleeding episodes. Both patient-related and therapy-related variables contribute to the development of inhibitors. The multifactorial nature of inhibitor development and the relatively small numbers of patients that participate in clinical trials make it difficult to accurately assess the risk of inhibitor development. Adding to that challenge is the lack of a uniform standard of design for conducting clinical trials to evaluate the safety of FVIII products. This hinders the comparison of products and is an obstacle to the meta-analysis necessary to make statistically valid assessments of inhibitor risk. This article reviews similarities and differences in clinical trial guidelines of European and US regulatory agencies and discusses the need for their harmonization to facilitate the assessment of FVIII products.

[Inhibitor development against FVIII in previously treated patients with haemophilia A. A retrospective data collection]

In a retrospective study 118 haemophilia A patients from two treatment centres (Berlin and Muenster) were evaluated with respect to safety, i. e. inhibitor development, and efficacy of bleeding control of recombinant FVIII products. During approx. 57 thousand injections with more than 87 million I.U. rFVIII no de novo inhibitor was observed in patients previously treated with pFVIII after switch to a recombinant product. A total of 75 thousand injections with more than 111 million I.U. FVIII had been applied during the investigation period of 14 years. Before as well as after switch of the product type bleeding episodes could be controlled with one to two injections per bleed.

CONCLUSION

According to our results equal safety and efficacy of plasma derived and recombinant FVIII products can be assumed.

Efficacy and safety of secondary prophylactic vs. on-demand sucrose-formulated recombinant factor VIII treatment in adults with severe hemophilia A: results from a 13-month crossover study

BACKGROUND

Hemarthroses in severe hemophilia precipitate physical, psychosocial and financial difficulties.

OBJECTIVE

To compare the effects of secondary prophylaxis with on-demand sucrose-formulated recombinant factor VIII (rFVIII-FS) therapy in severe hemophilia A.

PATIENTS AND METHODS

This open-label study included patients aged 30-45 years with factor VIII (FVIII) coagulant activity < 1 IU dL(-1) who were using on-demand FVIII treatment. Patients were treated with rFVIII-FS on demand for 6 months, followed by 7 months prophylaxis (20-40 IU kg(-1), three times per week, with the first month considered a run-in). The primary endpoint was the number of hemarthroses.

RESULTS

Twenty patients were enrolled (n = 19 completed); the mean age was 36.4 years, and 16 had target joints. The median (25-75%) number of joint bleeds decreased significantly with prophylaxis [0 (0-3)] vs. on-demand [15 (11-26); P < 0.001] therapy. The number of all bleeds was 0 (0-3) vs. 20.5 (14-37; P < 0.001), respectively. Median (range) total Gilbert scores improved after prophylaxis [18 (3-39)] compared with on-demand [25 (4-46)] therapy, predominantly reflecting the improved bleeding score. Median time from last prophylactic infusion to bleed was 2 days; 82.5% of bleeds occurred 2-3 days after the last infusion. Median 48-h and 72-h FVIII trough levels measured during months 10 and 13 were consistently > 6 and > 4 IU dL(-1), respectively. Treatment was well tolerated, and no inhibitor formation was observed.

CONCLUSION

Secondary prophylaxis with rFVIII-FS significantly reduced the frequency of hemarthroses compared with on-demand therapy in adult patients with severe hemophilia A.

[Personification of the standard treatment of patients with hemophilia A (results of a multicenter Russian open-labeled prospective study evaluating the use of haemoctin)]

AIM

To evaluate the clinical efficiency, tolerability, safety, and immunogenicity of replacement therapy with haemoctin SDH (Biotest Pharma GmbH, Germany) in pretreated patients with hemophilia A (HA).

SUBJECTS AND METHODS

The pretreated patients (n = 140) with varying GA from 12 regions of the Russian Federation received haemoctin replacement therapy (for prophylaxis and if needed) during a year. The levels of coagulation factor VIII, its inhibitor, HIV-1/HIV-2, the markers of hepatic and renal diseases, clinical blood test were determined and a virological study was made thrice during this period at an interval of 6 months. The therapy was considered to be effective if the pain syndrome regressed within 24 hours after the last administration of the drug and/or bleeding stopped. The results of a one-year follow-up of 106 patients receiving haemoctin monotherapy were analyzed.

RESULTS

The history data suggest that there are problems in the diagnosis of hereditary coagulopathies (the mean age of diagnosis verification of 3.5 years; no family history data in 67% of cases), there is a need for the guaranteed provision of patients with adequate quantities of the drug due to the fact that a third of patients had life-threatening bleedings/hemorrhages and that the patients (46%) need additional examination and treatment for comorbidity according to the standards of therapy. Compliance of haemoctin doses and regimens with their timely individual correction ensures a 3-fold reduction on average in the incidence of the hemorrhagic syndrome, an increase in quality of life, and a decrease in the frequency of analgesic use (from 21% to 0). Treatment is satisfactorily tolerated. There is evidence for the safety and low immunogenicity of the drug.

CONCLUSION

To enhance the efficiency of therapeutic-and-prophylactic care to patients with GA and to optimize their quality of life, a personification approach to treatment is recommended, by individually choosing drugs, their doses and regimens.

Therapeutic properties and safety of recombinant factor VIII and factor IX

Advances in hemophilia management in the 20th century enabled effective and early treatment of joint and other bleeds typical of this disease, also in a home setting. Prophylaxis became available as the optimal approach to prevent hemophilic arthropathy and improve patients' quality of life. To increase treatment safety, lyophilized plasma-derived factor VIII and IX concentrates were subjected to numerous procedures designed to decrease the risk of transmission of known and unknown pathogens. During the following years, recombinant factor VIII and factor IX preparations were developed to completely eliminate the risk. Recombinant factor concentrates were extensively studied in terms of their therapeutic properties, safety, and immunogenicity. This article reviews the current knowledge on efficacy and safety of recombinant factors VIII and IX.

Chronic hepatitis in hemophilia

The relationship of chronic hepatitis B and/or liver dysfunction to treatment in 113 hemophiliacs was evaluated by the enzyme tests, SGOT and SGPT, and by the presence of circulating hepatis B surface antigen (HbsAg) or antibody (anti-Hbs). The hemophiliacs were divided into three groups according to treatment pattern. Individuals who had received multiple doses of plasma fractions, derived from four or more commercial lots were placed in tgroup I "large Exposure". Group II "Small Exposure" had been treated with fractions from three or fewer lots and Group III "Cryo" had never received commercial fractions, but had been treated with cryoprecipitate. Abnormal liver function tests (LFT's) were found in 87% of Group I and 76% of Group II, but in only 16% of the "Cryo" group. Differences in LFT's were not great between treated VIII and IX deficient patients. All patients treated with 100,000 units or more showed either persistent or intermittent abnormalities. In the high exposure group, this history of past, overt hepatitis had no influence on observed LFT's. The sera of all patients in the high exposure and all, except one, in the low exposure groups were positive for HbsAg or anti-Hbs by RIA. Splenomegaly was found in 13% of fraction-treated patients. We conclude that there is biochemical evidence of liver disease following large exposure to commercial VIII or IX fractions, which should temper the physician's decision to start treatment with these fractions. On the other hand, evidence that their continued use produces mounting liver dysfunction is insufficient to withdraw this very effective and life-changing treatment from these individuals.

Side effects of antihemophilic concentrates

Liver disease and thromboembolism are the most frequent and severe side effects associated with the use of clotting-factor concentrates in haemophiliacs. Knowledge and careful evaluation of the risk factors related to their development appear to be the most reasonable policy for prevention. themolysis due to significant isoantibody infusion and bleeding associated to abnormal platelet function occur more rarely during intensive replacement therapy with clotting factor concentrates. Finally, abnormalities of renal function have been observed in a number of patients, though they seem to be of minor clinical importance. These complications do not justify withdrawal or limitation of the very effective and life-changing use of concentrates. However, awareness of their occurrence and of their danger requires that specialized hemophilia centres carry out, at frequent intervals, clinical and laboratory testing of the target organs to allow an early detection.

Alteration of primary hemostasis in hemophiliacs after treatment with lyophilized antihemophilic globulin

Seven patients with classic hemophilia A had alteration of primary hemostasis after treatment with lyophilized antihemophilic globulin (LAHG). The following test results, which were normal before treatment, became abnormal after treatment: bleeding time, bleeding intensity, and platelet adhesiveness. In two patients, the fibrin-fibrinogen-degradation products increased to more than 40 microgram/ml. In three patients, the bleeding symptoms became worse with LAHG therapy although no inhibitor against Factor VIII was demonstrated. In one of these patients, the bleedings symptoms disappeared when the use of LAHG was discontinued and prednisone was given; at the same time, the altered primary hemostasis returned to normal. In the remaining two patients, prednisone did not have any effect. In these two patients, however, the bleeding stopped, and the bleeding time became normal immediately after freshly prepared blood-group compatible cryoprecipitate was given.

Liver dysfunction in patients with hemophilia

The incidence of post-transfusion hepatitis and liver dysfunction is presented in fifty-four patients with classical hemophilia who received episodic and/or prophylactic Factor VIII concentrate. 42.5% had persistent biochemical evidence of liver dysfunction with elevated SGOT and SGPT; 3.8% have persistent (HBs) antigenicity and 90% have (HBsAb) antibodies. The results are the same for those who were treated episodically and received an average of 753 units Factor VIII per week as those treated prophylactically who received an average of 686 Factor VIII units per week. The incidence of clinical and/or subclinical disease is unaffected by the transfusion regimen or the amount of concentrate used. The necessity for close follow is emphasized for determination of chronic liver disease and its further therapy.

Acute myocardial infarction in a patient with hemophilia A and factor V Leiden mutation

Factor VIII:C, epsilon amino-caproic acid or tranexamic acid are prophylactic agents used in preventing hemorrhage pre-operatively in patients with hemophilia A. Although hemophilia A seems to be a factor that avoids the development of acute myocardial infarction (AMI) as it tends to be associated with increased bleeding, it should be kept in mind that prothrombotic agents used pre-operatively for prophylaxis may increase the risk for AMI in the presence of the factor V Leiden mutation. In this report, we discuss the development of AMI following the use of recombinant factor VIII and tranexamic acid for prophylaxis in a patient with known hemophilia before a tooth extraction in conjunction with the relevant literature.

Plasma and albumin-free recombinant factor VIII: pharmacokinetics, efficacy and safety in previously treated pediatric patients

BACKGROUND

The pharmacokinetics of factor VIII replacement therapy in preschool previously treated patients (PTPs) with hemophilia A have not been well characterized.

OBJECTIVES

To assess the pharmacokinetics, efficacy and safety of a plasma-free recombinant FVIII concentrate, ADVATE [Antihemophilic Factor (Recombinant), Plasma/Albumin-Free Method, rAHF-PFM], in children < 6 years of age with severe hemophilia.

PATIENTS/METHODS

Fifty-two boys, one girl, mean (+/- SD) age 3.1 +/- 1.5 years and >or= 50 days of prior FVIII exposure, were enrolled in a prospective study of ADVATE rAHF-PFM at 23 centers.

RESULTS

The mean terminal phase half-life (t(1/2)) was 9.88 +/- 1.89 h, and the mean adjusted in vivo recovery (IVR) was 1.90 +/- 0.43 IU dL(-1) (IU kg(-1))(-1). Over the 1-6-year age range, t(1/2) of rAHF-PFM increased by 0.40 h year(-1). IVR increased by 0.095IU dL(-1)(IU kg(-1))(-1) (kg m(-2))(-1) in relation to body mass index (BMI). Patients primarily received prophylaxis. Median (range) annual joint bleeds were 0.0 (0.0-5.8), 0.0 (0.0-6.1) and 14.2 (0.0-34.5) for standard prophylaxis, modified prophylaxis and on-demand treatment, respectively. Bleeds were managed in 90% (319/354) of episodes with one or two rAHF-PFM infusions; response was rated excellent/good in 93.8% of episodes. Over a median 156 exposure days, no FVIII inhibitors were detected and no related severe adverse events or unusual non-serious adverse events were seen.

CONCLUSIONS

Children < 6 years of age appear to have shorter FVIII t(1/2) and lower IVR values than older subjects. However, these parameters increased with age (t(1/2)) and BMI (adjusted IVR), respectively. rAHF-PFM was clinically effective and well tolerated, with no signs of increased immunogenicity in previously treated young children with hemophilia A.

Surgical evaluation of a recombinant factor VIII prepared using a plasma/albumin-free method: efficacy and safety of Advate in previously treated patients

Evaluation of factor F(V)III replacement in patients with haemophilia A undergoing surgery is critical for FVIII concentrates, yet large scale, multi-center prospective studies, particularly using continuous infusion, are generally lacking for new products. This study evaluated efficacy and safety of a newly developed recombinant FVIII (rAHF-PFM) administered by bolus or continuous infusion in haemophilia A patients undergoing surgery. Subjects > or =5 years of age with baseline FVIII:C < or =2%, and > or =150 prior FVIII exposure days were included in this prospective, international, open-label, uncontrolled clinical trial. rAHF-PFM was administered perioperatively by bolus infusion (BI) or continuous infusion (CI) according to the standard use at the center to prevent bleeding complication. Both the surgeon and haematologist rated efficacy during hospitalization. Fifty-eight subjects underwent 65 surgical procedures (22 major haemorrhagic risk; 35 minor, 8 dental procedures). Bolus infusion was used exclusively in 47 procedures and continuous infusion, with or without supplemental bolus infusions, in 18. Haemostatic efficacy was assessed as excellent or good for 100% of intraoperative ratings (17 CI, 44 BI, 61 total procedures), and 100% of postoperative ratings performed at time of discharge (18 CI, 44 BI, 62 total procedures). Median total consumption of rAHF-PFM during hospitalization was 822 IU/kg/surgery with CI and 910 IU/kg/surgery with BI. Overall rAHF-PFM was well tolerated, and FVIII inhibitors were not detected. In conclusion, rAHF-PFM administered via continuous infusion or bolus injections is safe, non-immunogenic, and effective for perioperative hemostatic management in previously treated haemophilia A patients.

[Diagnostic image (379). A confused man with tetraparesis and haemophilia]

A 77-year-old haemophilic man presented with confusion, somnolence and tetraparesis due to massive bilateral subdural haematomas.

Pharmacokinetics, efficacy and safety of IMMUNATE solvent/detergent (IMMUNATE S/D) in previously treated patients with severe hemophilia A: results of a prospective, multicenter, open-label phase III study

BACKGROUND

IMMUNATE Solvent/Detergent (S/D) is a plasma-derived, human factor VIII (FVIII)/von Willebrand factor (VWF) complex subjected to S/D and vapor heat treatment.

METHODS

This prospective clinical study evaluated the pharmacokinetics (PK) (compared to IMMUNATE), efficacy and safety of IMMUNATE S/D in 56 previously treated patients with severe hemophilia A. Subjects received IMMUNATE S/D either on-demand (47/56), as a prophylactic regimen (49/56), or both (40/56).

RESULTS

IMMUNATE and IMMUNATES/D were equivalent with respect to the FVIII and VWF PK parameters assessed. Bleeding episodes (623) were reported in 47/56 subjects. For 89% of episodes, subjects required only 1 infusion with a mean dose of 29.6 IU/kg and 96% of episodes had an excellent or good response. The duration of prophylaxis ranged from 0.1 to 5.2 months. The median number of bleeds per month in subjects on prophylaxis was 0 (range 0-10). No FVIII inhibitory antibodies were observed in 56 subjects after 2,646 treatment exposure days. No related serious adverse events were reported.

CONCLUSION

The introduction of S/D treatment did not alter the PK characteristics and function of VWF and FVIII molecules in IMMUNATE S/D which is effective and safe for treatment of bleeding episodes, management of surgical procedures and prophylaxis.

Safety and pharmacokinetics of a recombinant factor VIII with pegylated liposomes in severe hemophilia A

BACKGROUND

BAY 79-4980 is a sucrose-formulated recombinant factor VIII (rFVIII-FS) combined with pegylated liposomes to prolong activity.

OBJECTIVES

To investigate the safety, tolerability, bioavailability, pharmacokinetics and pharmacodynamics of a single administration of BAY 79-4980 compared with standard rFVIII-FS in patients with severe hemophilia A.

METHODS

This randomized, double-blind study consisted of two crossover substudies comparing two doses of liposomal rFVIII-FS with standard rFVIII-FS. Males (12-60 years) with severe hemophilia A received a single infusion of standard rFVIII-FS (35 IU kg(-1)) followed by a single infusion of BAY 79-4980 (13 or 22 mg kg(-1) pegylated liposomes) or vice versa, with 12 observation days and a 2-day washout period between treatments.

RESULTS

Twenty-six subjects were enrolled at two centers. No serious adverse events were reported. Transient increases in complement C3a, but not CH50, were seen in subjects receiving both the low- and high-liposome-dose BAY 79-4980. Mild transient elevations of total and low-density lipoprotein cholesterol were observed. There were no clinically significant differences in clotting or laboratory parameters or in pharmacokinetic behavior between BAY 79-4980 and standard rFVIII-FS. The number of subjects with spontaneous bleeds on days 1-14 postinfusion was low, and group comparisons were inconclusive.

CONCLUSIONS

Single-dose administration of BAY 79-4980 is well tolerated in patients with severe hemophilia A. Plasma pharmacokinetics of FVIII cannot explain the extended protection from bleeding observed previously with BAY 79-4980. Further studies of efficacy and long-term safety of chronic administration are planned.

Safety and efficacy of a sucrose-formulated recombinant factor VIII product for the treatment of previously treated patients with haemophilia A in China

The use of plasma-derived products has contributed to a high rate of blood-borne infections among haemophilia patients in China. Recombinant factor VIII (rFVIII) products that are manufactured without human or bovine albumin and include dedicated viral inactivation steps, hold a significant safety advantage over plasma products. However, there is little information published on the use of rFVIII products in non-caucasian populations. This is the first reported evaluation of the efficacy and safety of a rFVIII product in Chinese haemophiliacs. An open-label, non-randomized, prospective, multicentre trial enroled previously treated Chinese patients with haemophilia A. All treatments were administered using a sucrose-formulated rFVIII-FS (Kogenate((R))). Forty-nine patients received totals of 291 infusions (mean, 5.94/patient) and 742 140 IU rFVIII-FS (mean, 2550.3 IU/infusion). Of the 60 acute bleeding episodes that were treated, 90% were successfully managed with only one (81.7%) infusion or two (8.3%) infusions. Physicians reported haemostasis control for acute bleeds to be 'Excellent' or 'Improved' with rFVIII-FS therapy. No FVIII inhibitors were detected in any patient. Only one treatment-related adverse event was reported, which was mild dizziness that resolved spontaneously. rFVIII-FS was efficacious, safe and well tolerated in the treatment of previously treated patients with haemophilia A in China.

Treatment characteristics and the risk of inhibitor development: a multicenter cohort study among previously untreated patients with severe hemophilia A

CONTEXT

The development of inhibitory antibodies against infused factor (F) VIII is a major complication of treatment of patients with severe hemophilia A.

OBJECTIVE

This study was set up to examine the effects of treatment-related factors on inhibitor development among previously untreated patients with severe hemophilia A.

DESIGN, SETTING AND PATIENTS

In this multicenter cohort study, we combined individual patient data obtained from four recombinant FVIII product registration studies (Kogenate, Kogenate Bayer, Recombinate, ReFacto) that were performed between 1989 and 2001. From the databases we selected all 236 previously untreated patients with severe hemophilia A who were subsequently treated with FVIII on at least 50 days.

MAIN OUTCOME MEASURES

Clinically relevant inhibitor development, defined as the occurrence of at least two positive inhibitor titers and a decreased recovery.

RESULTS

67 patients (28%) developed clinically relevant inhibitors (44 high-titer) at a median of ten exposure days. Age at first exposure was not associated with inhibitor development. Peak treatment moments and surgical procedures were related to an increased inhibitor risk [adjusted relative risk 1.6 (95% confidence interval 1.0-2.6) and 2.7 (95% confidence interval 1.3-5.7), respectively]. A shorter duration between exposure days was associated with an increased risk of inhibitor development. There was a possible association between dosing of FVIII and inhibitor development, which largely disappeared after adjustment for confounding factors.

INTERPRETATION

These findings show that intensive treatment periods are associated with an increased risk of inhibitor development in previously untreated patients with severe hemophilia A. Our results do not support the notion that age at first exposure is associated with the risk of developing inhibitors.

von Willebrand factor/factor VIII concentrate (Haemate P) dosing based on pharmacokinetics: a prospective multicenter trial in elective surgery

BACKGROUND

While plasma-derived concentrates containing large amounts of von Willebrand factor (VWF) are effective in treating von Willebrand disease (VWD), optimal dosing remains to be fully characterized.

OBJECTIVES

To determine the feasibility of dosing Haemate P VWF/factor VIII (FVIII) concentrate based on pharmacokinetics (PK) in the management of surgical subjects with VWD.

METHODS

VWD subjects scheduled for elective surgery were enrolled in a prospective multicenter open-label cohort study. A pre-operative loading dose of VWF/FVIII concentrate based upon prior individual subject PK analysis was administered followed by postoperative therapeutic/maintenance infusions.

RESULTS

Twenty-eight subjects with types 1, 2A or 3 VWD and one with type 2 M were enrolled. Median in vivo recovery of VWF ristocetin cofactor (VWF:RCo) was 1.9 IU dL(-1) (IU kg(-1))(-1) with an interquartile range (IQR) of 1.6-2.5 IU dL(-1) (IU kg(-1))(-1). Median response, half-life and clearance were 74.0% (IQR, 55.5-100%), 15.6 h (IQR, 9.0-28.4 h) and 3.26 mL kg(-1) h(-1) (IQR, 2.29-5.21 mL kg(-1) h(-1)), respectively. A PK-guided median VWF:RCo loading dose of 62.4 IU kg(-1) (IQR, 50.1-87.0 IU kg(-1)) was administered. Postoperative mean trough VWF:RCo levels of 62-73 IU dL(-1) were sufficient to prevent bleeding. Investigators rated hemostasis excellent or good in 96.3% of subjects on the day of surgery and 100% on the next day and on day 14. A subject with multiple risk factors developed pulmonary embolism, which resolved without sequelae.

CONCLUSIONS

Haemate P provided effective and safe hemostasis in VWD subjects undergoing elective surgery. Selection of Haemate P loading dose on the basis of VWF PK proved feasible.

Treatment of severe von Willebrand disease with a high-purity von Willebrand factor concentrate (Wilfactin): a prospective study of 50 patients

BACKGROUND AND OBJECTIVES

A plasma-derived von Willebrand factor (VWF) concentrate with low factor VIII (FVIII) content was specifically developed to treat von Willebrand disease (VWD). Efficacy and safety were investigated by merging the results of two comparable protocols conducted prospectively in 5 European and 12 French centers.

METHODS AND RESULTS

Fifty patients with clinically severe VWD (72% had VWF ristocetin cofactor activity less than 10 IU dL(-1) and 46% had FVIII < 20 IU dL(-1)) were treated with the concentrate as the only therapy, except for clinical situations requiring a priming dose of FVIII to rapidly correct an intrinsic coagulation defect. A total of 139 spontaneous bleeding episodes were treated; only 53 (38%) needed a concomitant FVIII dose. Outcome was excellent or good in 89% of the episodes. Forty-four patients underwent 108 surgical or invasive procedures. Outcome was excellent or good in 95 scheduled procedures (only VWF was infused) and 13 emergency procedures (a priming FVIII dose was co-administered with the first VWF infusion). There were no thrombotic complications and none of the 18 patients with type 3 VWD developed anti-VWF or anti-FVIII antibodies.

CONCLUSIONS

This concentrate safely and effectively provides hemostasis in patients with clinically severe VWD.

Comparison of the pharmacokinetics of two von Willebrand factor concentrates [Biostate and AHF (High Purity)] in people with von Willebrand disorder. A randomised cross-over, multi-centre study

Plasma-derived factor concentrates are important in the management of von Willebrand disorder (VWD). In our geographic locality, a single viral inactivation step concentrate (AHF [High Purity]), has been replaced with one using a double viral inactivation step (Biostate). The aim of this study was to compare the pharmacokinetics of von Willebrand factor (VWF) and factor VIII (FVIII) after administration of AHF (High Purity) and Biostate. This study was a single-blind, randomised cross-over, multi-centre investigation in twelve people with VWD, comprising four type 3, two type 2B, one type 2M and five type 1 VWD. The subjects received a single infusion of 60 IU/kg ristocetin cofactor activity (VWF:RCo) of either AHF (High Purity) or Biostate, and after a minimum 15-day wash-out period they received the alternative product. Blood samples were collected for up to 48 hours after each dose for assay of FVIII coagulant activity (FVIII:C) and VWF by VWF:RCo, collagen binding capacity (VWF:CB) and antigen (VWF:Ag). As a measure of delivered VWF 'functionality' we calculated the area-under-the-concentration-time-curve (AUC) ratios of VWF:RCo to VWF:Ag and VWF:CB to VWF:Ag. The effect on platelet adhesiveness by PFA-100 closure times (CTs) was measured prior to and 30 minutes post infusion. VWF multimers were also assessed pre and post infusion. Pharmacokinetic parameters after AHF (High Purity) and Biostate were in close agreement for VWF:RCo (confirming dosing equivalence). Parameters for other study markers were also similar, although Biostate tended to yield relatively lower VWF:Ag and higher VWF:CB levels. Although AHF (High Purity) and Biostate resulted in similar levels of high-molecular-weight (HMW) multimers post-infusion, the relative level of HMW to low-molecular-weight (LMW) multimers were determined to be higher following Biostate. The relative levels of functional VWF (i.e. VWF:CB and VWF:RCo) to VWF:Ag were also higher in Biostate compared to AHF (High Purity). With both study products, PFA-100 CTs 30 minutes post infusion showed minor improvement for only some subjects. In conclusion, the pharmacokinetics of FVIII:C and VWF are not significantly different after administration of AHF (High Purity) and Biostate. Study parameters considered as 'in-vitro' markers of VWF 'functionality' or potential clinical efficacy (i.e. VWF:CB and VWF:RCo relative to VWF:Ag, level of HMW VWF relative to LMW-VWF) were determined to be higher for Biostate than AHF (High Purity). PFA-100 CTs did not adequately reflect changes in these VWF parameters. Based on these results, one would expect Biostate to be at least as effective, if not superior to AHF (High Purity) for the treatment of VWD.