Post hoc longitudinal assessment of the efficacy and safety of recombinant factor IX Fc fusion protein in hemophilia B

Long-term efficacy and safety of the extended half-life recombinant factor IX Fc fusion protein (rFIXFc) has been established among previously treated patients with severe hemophilia B in 2 phase 3 trials (B-LONG [#NCT01027364] and Kids B-LONG [#NCT01440946]) and a long-term extension study (B-YOND [#NCT01425723]). In this study, we report post hoc analyses of pooled longitudinal data for up to 6.5 years for rFIXFc prophylaxis. In the B-LONG study, subjects ≥12 years received weekly dose-adjusted prophylaxis (WP; starting dose, 50 IU/kg), individualized interval-adjusted prophylaxis (IP; initially, 100 IU/kg every 10 days), or on-demand dosing. In the Kids B-LONG study, subjects <12 years received 50 to 60 IU/kg every 7 days, adjusted as needed. In the B-YOND study, subjects received WP (20-100 IU/kg every 7 days), IP (100 IU/kg every 8-16 days), modified prophylaxis, or on-demand dosing; switching between treatment groups was permitted. A total of 123 subjects from B-LONG and 30 from Kids B-LONG study were included, of whom 93 and 27, respectively, enrolled in the B-YOND study. The median cumulative duration of treatment was 3.63 years (range, 0.003-6.48 years) in B-LONG/B-YOND and 2.88 years (range, 0.30-4.80 years) in Kids B-LONG/B-YOND group. Annualized bleed rates (ABRs) remained low, annualized factor consumption remained stable, and adherence remained high throughout treatment. Low ABRs were also maintained in subjects with dosing intervals ≥14 days or with target joints at baseline. Complete resolution of evaluable target joints and no recurrence in 90.2% of baseline target joints during follow-up were observed. rFIXFc prophylaxis was associated with sustained clinical benefits, including long-term bleed prevention and target joint resolution, for severe hemophilia B.

Gene Therapy with Etranacogene Dezaparvovec for Hemophilia B

BACKGROUND

Moderate-to-severe hemophilia B is treated with lifelong, continuous coagulation factor IX replacement to prevent bleeding. Gene therapy for hemophilia B aims to establish sustained factor IX activity, thereby protecting against bleeding without burdensome factor IX replacement.

METHODS

In this open-label, phase 3 study, after a lead-in period (≥6 months) of factor IX prophylaxis, we administered one infusion of adeno-associated virus 5 (AAV5) vector expressing the Padua factor IX variant (etranacogene dezaparvovec; 2×10¹³ genome copies per kilogram of body weight) to 54 men with hemophilia B (factor IX activity ≤2% of the normal value) regardless of preexisting AAV5 neutralizing antibodies. The primary end point was the annualized bleeding rate, evaluated in a noninferiority analysis comparing the rate during months 7 through 18 after etranacogene dezaparvovec treatment with the rate during the lead-in period. Noninferiority of etranacogene dezaparvovec was defined as an upper limit of the two-sided 95% Wald confidence interval of the annualized bleeding rate ratio that was less than the noninferiority margin of 1.8. Superiority, additional efficacy measures, and safety were also assessed.

RESULTS

The annualized bleeding rate decreased from 4.19 (95% confidence interval [CI], 3.22 to 5.45) during the lead-in period to 1.51 (95% CI, 0.81 to 2.82) during months 7 through 18 after treatment, for a rate ratio of 0.36 (95% Wald CI, 0.20 to 0.64; P<0.001), demonstrating noninferiority and superiority of etranacogene dezaparvovec as compared with factor IX prophylaxis. Factor IX activity had increased from baseline by a least-squares mean of 36.2 percentage points (95% CI, 31.4 to 41.0) at 6 months and 34.3 percentage points (95% CI, 29.5 to 39.1) at 18 months after treatment, and usage of factor IX concentrate decreased by a mean of 248,825 IU per year per participant in the post-treatment period (P<0.001 for all three comparisons). Benefits and safety were observed in participants with predose AAV5 neutralizing antibody titers of less than 700. No treatment-related serious adverse events occurred.

CONCLUSIONS

Etranacogene dezaparvovec gene therapy was superior to prophylactic factor IX with respect to the annualized bleeding rate, and it had a favorable safety profile. (Funded by uniQure and CSL Behring; HOPE-B ClinicalTrials.gov number, NCT03569891.).

Managing surgery in hemophilia with recombinant factor VIII Fc and factor IX Fc: Data on safety and effectiveness from phase 3 pivotal studies

Background

Surgical procedures impose hemostatic risk to people with hemophilia, which may be minimized by optimal factor (F) replacement therapy.

Methods

This analysis evaluates the efficacy and safety of extended half-life factor replacement recombinant FVIII and FIX Fc fusion proteins (rFVIIIFc and rFIXFc) during surgery in phase 3 pivotal (A-LONG/Kids A-LONG and B-LONG/Kids B-LONG) and extension (ASPIRE and B-YOND) studies. Dosing regimens were determined by investigators. Injection frequency, dosing, blood loss, transfusions, and hemostatic response were assessed.

Results

Forty-five major (n = 31 subjects) and 90 minor (n = 70 subjects) procedures were performed in hemophilia A; 35 major (n = 22) and 62 minor (n = 37) procedures were performed in hemophilia B. Unilateral knee arthroplasty was the most common major orthopedic procedure (hemophilia A: n = 15/34; hemophilia B: n = 8/24). On the day of surgery, median total dose in adults/adolescents was 81 IU/kg for rFVIIIFc and 144 IU/kg for rFIXFc; most major procedures required ≤2 injections (including loading dose). Through days 1-14, most major procedures had ≤1 injection/day. Hemostasis was rated excellent (rFVIIIFc: n = 39/42; rFIXFc: n = 29/33) or good (n = 3/42; n = 4/33) in evaluable major surgeries, with blood loss comparable with subjects without hemophilia. Most minor procedures in adults/adolescents required one injection on the day of surgery, including median loading dose of 51 IU/kg (rFVIIIFc) and 80 IU/kg (rFIXFc). No major treatment-related safety concerns were identified. No subjects developed inhibitors or serious vascular thromboembolic events.

Conclusions

rFVIIIFc and rFIXFc were efficacious and well tolerated for the management of perioperative hemostasis across a wide spectrum of major and minor surgeries in hemophilia.

Valoctocogene Roxaparvovec Gene Therapy for Hemophilia A

BACKGROUND

Valoctocogene roxaparvovec (AAV5-hFVIII-SQ) is an adeno-associated virus 5 (AAV5)-based gene-therapy vector containing a coagulation factor VIII complementary DNA driven by a liver-selective promoter. The efficacy and safety of the therapy were previously evaluated in men with severe hemophilia A in a phase 1-2 dose-escalation study.

METHODS

We conducted an open-label, single-group, multicenter, phase 3 study to evaluate the efficacy and safety of valoctocogene roxaparvovec in men with severe hemophilia A, defined as a factor VIII level of 1 IU per deciliter or lower. Participants who were at least 18 years of age and did not have preexisting anti-AAV5 antibodies or a history of development of factor VIII inhibitors and who had been receiving prophylaxis with factor VIII concentrate received a single infusion of 6×1013 vector genomes of valoctocogene roxaparvovec per kilogram of body weight. The primary end point was the change from baseline in factor VIII activity (measured with a chromogenic substrate assay) during weeks 49 through 52 after infusion. Secondary end points included the change in annualized factor VIII concentrate use and bleeding rates. Safety was assessed as adverse events and laboratory test results.

RESULTS

Overall, 134 participants received an infusion and completed more than 51 weeks of follow-up. Among the 132 human immunodeficiency virus-negative participants, the mean factor VIII activity level at weeks 49 through 52 had increased by 41.9 IU per deciliter (95% confidence interval [CI], 34.1 to 49.7; P<0.001; median change, 22.9 IU per deciliter; interquartile range, 10.9 to 61.3). Among the 112 participants enrolled from a prospective noninterventional study, the mean annualized rates of factor VIII concentrate use and treated bleeding after week 4 had decreased after infusion by 98.6% and 83.8%, respectively (P<0.001 for both comparisons). All the participants had at least one adverse event; 22 of 134 (16.4%) reported serious adverse events. Elevations in alanine aminotransferase levels occurred in 115 of 134 participants (85.8%) and were managed with immune suppressants. The other most common adverse events were headache (38.1%), nausea (37.3%), and elevations in aspartate aminotransferase levels (35.1%). No development of factor VIII inhibitors or thrombosis occurred in any of the participants.

CONCLUSIONS

In patients with severe hemophilia A, valoctocogene roxaparvovec treatment provided endogenous factor VIII production and significantly reduced bleeding and factor VIII concentrate use relative to factor VIII prophylaxis. (Funded by BioMarin Pharmaceutical; GENEr8-1 ClinicalTrials.gov number, NCT03370913.).

Persistence of haemostatic response following gene therapy with valoctocogene roxaparvovec in severe haemophilia A

Introduction

Valoctocogene roxaparvovec is an investigational AAV5‐based factor VIII (FVIII) gene therapy that has demonstrated sustained clinical benefit in people with severe haemophilia A.

Aim

To report safety, tolerability, efficacy, and quality of life (QOL) among participants who received valoctocogene roxaparvovec in a phase 1/2 clinical study (NCT02576795).

Methods

Men ≥18 years of age with severe haemophilia A (FVIII ≤1 IU/dl) without history of FVIII inhibitors or anti‐AAV5 antibodies received a single infusion of valoctocogene roxaparvovec and were followed for 5 years (6 × 10¹³ vg/kg dose, n = 7) and 4 years (4 × 10¹³ vg/kg dose, n = 6).

Results

Over the past 2 years, few adverse events and no FVIII inhibitors were reported. Per chromogenic substrate (CSA) assay at years 5 and 4, four of seven and three of six participants in the 6 × 10¹³ and 4 × 10¹³ vg/kg cohorts, respectively, maintained median FVIII levels >5 IU/dl, corresponding to mild haemophilia. By regression analysis, rate of change in FVIII activity was ‐0.14 (95% confidence interval [CI]: ‐.32 to .03) IU/dl/wk in the 6 × 10¹³ vg/kg cohort in year 5 and ‐.06 (95% CI: ‐.14 to .01) IU/dl/wk in the 4 × 10¹³ vg/kg cohort in year 4. No participants resumed FVIII prophylaxis, and eight of 13 participants reported zero bleeds in the past 2 years. Improved QOL from baseline persisted in the 6 × 10¹³ vg/kg cohort; all six Haemo‐QOL‐A domain scores increased. For the 4 × 10¹³ vg/kg cohort, high baseline Haemo‐QOL‐A scores persisted.

Conclusion

These results demonstrate transgene expression and haemostatic response for up to 5 years in individuals with haemophilia A.

Recombinant factor VIII Fc for the treatment of haemophilia A

Prophylaxis with factor VIII (FVIII) is the current therapeutic approach for people with haemophilia A. However, standard half-life (SHL) FVIII products must be injected frequently, imposing a substantial burden on the individual and making it difficult to tailor therapy according to patient need and lifestyle, which could impact adherence. Recombinant FVIII Fc fusion protein (rFVIIIFc; Elocta® , Sobi; Eloctate® , Sanofi) is a recombinant fusion protein that undergoes slower clearance from the body than SHL FVIII products. This pharmacokinetic property of rFVIIIFc allows prophylactic administration every 3-5 days, or once weekly in selected patients, with doses adjusted to patient needs and clinical outcomes. Higher FVIII levels can be achieved maintaining dosing frequency similar to that usually applied with SHL FVIII. This review provides a summary of recent data from the A-LONG, Kids A-LONG, ASPIRE and PUPs A-LONG studies and recently published real-world experience relevant to rFVIIIFc use in individualised regimens. The review also introduces ongoing studies of rFVIIIFc, including its use for induction of immune tolerance, and discusses some aspects to consider when switching patients to rFVIIIFc and managing ongoing treatment. In summary, rFVIIIFc is suitable for individualised prophylaxis regimens that can be tailored according to patient clinical needs and lifestyle.

Targeting of antithrombin in hemophilia A or B with investigational siRNA therapeutic fitusiran-Results of the phase 1 inhibitor cohort

BACKGROUND

Fitusiran, an investigational small interfering RNA therapy, reduces antithrombin production to rebalance hemostasis in people with hemophilia A or B, with or without inhibitors.

OBJECTIVES

To evaluate the safety and efficacy of fitusiran treatment for people with moderate/severe hemophilia A or B with inhibitors.

PATIENTS/METHODS

In this open-label phase 1, part D study, 17 males with hemophilia A or B with inhibitors received three once-monthly subcutaneous injections of fitusiran 50 mg (n = 6) or 80 mg (n = 11); followed for up to 112 days. Endpoints included safety (primary), pharmacokinetics/pharmacodynamics (secondary), annualized bleeding rate, and patient-reported outcomes (exploratory).

RESULTS

The most common adverse event was injection site erythema (n = 8). No thrombotic events were reported. At nadir, mean (standard error of the mean [SEM]) antithrombin activity decreased from baseline by 82.0% (2.2) and 87.4% (0.7) in the 50 mg and 80 mg groups, respectively. Antithrombin reduction was associated with increased thrombin generation. 11/17 (64.7%) participants had no bleeds during the observation period (mean [standard deviation] 69.4 [16.3] days). Mean (SEM) changes from baseline in Haemophilia Quality of Life Questionnaire for Adults total (-9.2 [2.9]) and physical health (-12.3 [3.9]) domain scores suggested clinically meaningful improvement.

CONCLUSIONS

Monthly fitusiran was generally well tolerated, lowered antithrombin levels from baseline, and resulted in improved thrombin generation. These preliminary results suggest that monthly fitusiran treatment may reduce bleeding episodes and improve quality of life in participants with hemophilia A or B with inhibitors.

Long-term safety and sustained efficacy for up to 5 years of treatment with recombinant factor IX Fc fusion protein in subjects with haemophilia B: Results from the B-YOND extension study

INTRODUCTION

Recombinant factor IX Fc fusion protein (rFIXFc) has demonstrated efficacy for treatment of haemophilia B in the Phase 3 B-LONG and Kids B-LONG studies. However, long-term rFIXFc safety and efficacy data have not yet been reported.

AIM

To report long-term rFIXFc safety and efficacy in subjects with haemophilia B.

METHODS

B-YOND (NCT01425723) was an open-label extension for eligibl previously treated subjects who completed B-LONG or Kids B-LONG. Subjects received ≥1 treatment regimen: weekly prophylaxis (WP), individualized interval prophylaxis (IP), modified prophylaxis or episodic treatment. Subjects could switch regimens at any time. The primary endpoint was inhibitor development.

RESULTS

Ninety-three subjects from B-LONG and 27 from Kids B-LONG (aged 3-63 years) were enrolled. Most subjects received WP (B-LONG: n = 51; Kids B-LONG: n = 23). For subjects from B-LONG, median (range) treatment duration was 4.0 (0.3-5.4) years and median (range) number of exposure days (EDs) was 146 (8-462) EDs. Corresponding values for paediatric subjects were 2.6 (0.2-3.9) years and 132 (50-256) EDs. No inhibitors were observed (0 per 1000 subject-years; 95% confidence interval, 0-8.9) and the overall rFIXFc safety profile was consistent with prior studies. Annualized bleed rates remained low and extended-dosing intervals were maintained for most subjects. Median dosing interval for the IP group was approximately 14 days for adults and adolescents (n = 31) and 10 days for paediatric subjects (n = 5).

CONCLUSIONS

B-YOND results confirm the long-term (up to 5 years, with cumulative duration up to 6.5 years) well-characterized safety and efficacy of rFIXFc treatment for haemophilia B.

Hemophilia gene therapy knowledge and perceptions: Results of an international survey

BACKGROUND

Hemophilia gene therapy is a rapidly evolving therapeutic approach in which a number of programs are approaching clinical development completion.

OBJECTIVE

The aim of this study was to evaluate knowledge and perceptions of a variety of health care practitioners and scientists about gene therapy for hemophilia.

METHODS

This survey study was conducted February 1 to 18, 2019. Survey participants were members of the ISTH, European Hemophilia Consortium, European Hematology Association, or European Association for Hemophilia and Allied Disorders with valid email contacts. The online survey consisted of 36 questions covering demographic information, perceptions and knowledge of gene therapy for hemophilia, and educational preferences. Survey results were summarized using descriptive statistics.

RESULTS

Of the 5117 survey recipients, 201 responded from 55 countries (4% response rate). Most respondents (66%) were physicians, and 59% were physicians directly involved in the care of people with hemophilia. Among physician respondents directly involved in hemophilia care, 35% lacked the ability to explain the science of adeno-associated viral gene therapy for hemophilia, and 40% indicated limited ability or lack of comfort answering patient questions about gene therapy for hemophilia based on clinical trial results to date. Overall, 75% of survey respondents answered 10 single-answer knowledge questions correctly, 13% incorrectly, and 12% were unsure of the correct answers.

CONCLUSIONS

This survey highlighted knowledge gaps and educational needs related to gene therapy for hemophilia and, along with other inputs, has informed the development of "Gene Therapy in Hemophilia: An ISTH Education Initiative."

Recombinant factor VIII Fc fusion protein for the treatment of severe haemophilia A: Final results from the ASPIRE extension study

Introduction

The efficacy and safety of recombinant factor VIII Fc fusion protein (rFVIIIFc) as an extended half‐life treatment for severe haemophilia A were demonstrated in the Phase 3 A‐LONG and Kids A‐LONG studies. Eligible subjects who completed A‐LONG and Kids A‐LONG could enrol in ASPIRE (NCT01454739), an open‐label extension study.

Aim

To report the long‐term safety and efficacy of rFVIIIFc in subjects with severe haemophilia A who enrolled in ASPIRE.

Methods

Previously treated subjects received one or more of the following regimens: individualized prophylaxis (IP), weekly prophylaxis, modified prophylaxis or episodic treatment. Subjects could switch treatment regimen at any time. The primary endpoint was inhibitor development.

Results

A total of 150 subjects from A‐LONG and 61 subjects from Kids A‐LONG enrolled in ASPIRE. Most subjects received the IP regimen (A‐LONG: n = 110; Kids A‐LONG: n = 59). Median (range) treatment duration in ASPIRE for subjects from A‐LONG and Kids A‐LONG was 3.9 (0.1‐5.3) years and 3.2 (0.3‐3.9) years, respectively. No inhibitors were observed (0 per 1000 subject‐years; 95% confidence interval, 0‐5.2) and the overall rFVIIIFc safety profile was consistent with prior studies. For subjects on the IP regimen, annualized bleed rates (ABR) remained low (median overall ABR for adults and adolescents was <1.0) and extended‐dosing intervals were maintained (median of 3.5 days) for the majority of subjects in ASPIRE.

Conclusion

ASPIRE results, which include up to 5 years of follow‐up data, confirm earlier reports on the consistent and well‐characterized safety and efficacy of rFVIIIFc treatment for severe haemophilia A.

Towards a global multidisciplinary consensus framework on haemophilia gene therapy: Report of the 2nd World Federation of Haemophilia Gene Therapy Round Table

INTRODUCTION

With approval of gene therapy for haemophilia likely in the near future, policy frameworks are needed to guide the path forward for this disruptive and novel therapeutic advance.

AIM

The WFH has initiated a series of multi-stakeholder Gene Therapy Round Tables (GTRT) to better understand where guidance is needed and develop initial consensus statements to inform policy.

METHODS

The first day of the 2nd GTRT was devoted to didactic presentations on models of access to gene therapy, payment and health technology assessment considerations, regulatory issues and the generation of evidence on safety and durable efficacy of gene therapy products. On the second day, participants were tasked with developing and voting on consensus statements that reflected the information presented and multi-stakeholder views expressed during discussions in the 1st and 2nd WFH GTRTs. The statements covered global access to gene therapy for all people with haemophilia (PWH), collection of long-term safety and efficacy data, ensuring gene therapy is available for all subgroups of PWH including those who have been largely excluded from clinical trials and characterizing acceptable and ideal factor expression levels for gene therapy products.

RESULTS

The first 3 statements achieved consensus (at least 80% agreement) by this group of experts. The statement on identifying an ideal and an acceptable factor level expression elicited a lively discussion but failed to achieve consensus by this group.

CONCLUSIONS

This issue of ideal and acceptable factor level expression and other unresolved issues will be brought to the 3rd WFH GTRT in 2020.

Multiyear Follow-up of AAV5-hFVIII-SQ Gene Therapy for Hemophilia A

BACKGROUND

Adeno-associated virus (AAV)-mediated gene therapy is under investigation as a therapeutic option for persons with hemophilia A. Efficacy and safety data include 3 years of follow-up after a single administration of AAV5-hFVIII-SQ.

METHODS

We report durable efficacy, long-term safety, and clinical and biologic results in 15 adults with severe hemophilia A (factor VIII level, ≤1 IU per deciliter) who had received a single infusion of AAV5-hFVIII-SQ at various dose levels. We evaluated the factor VIII level, annualized rate of bleeding events, use of factor VIII, safety, expression kinetics, and biologic markers of AAV transduction for up to 3 years.

RESULTS

Three years after infusion, two participants (one who had received 6×10¹² vector genomes [vg] per kilogram of body weight and one who had received 2×10¹³ vg per kilogram) had factor VIII expression of less than 1 IU per deciliter, as assessed on chromogenic assay. Seven participants (who had received 6×10¹³ vg per kilogram) had a median factor VIII expression of 20 IU per deciliter; the median number of annualized treated bleeding events was 0, and the median use of exogenous factor VIII was reduced from 138.5 infusions to 0 infusions per year. Bleeding in all target joints (major joints with ≥3 bleeding events within 6 months) in this cohort resolved (≤2 bleeding events within 12 months). Two years after infusion, six participants (who had received 4×10¹³ vg per kilogram) had a median factor VIII expression of 13 IU per deciliter; the median annualized rate of bleeding events was 0, and the median use of factor VIII was reduced from 155.5 infusions to 0.5 infusions per year. Bleeding in target joints resolved in five of six participants. The factor VIII pharmacodynamic profiles reflected cellular turnover in the blood and molecular events leading to episomal DNA stabilization for persistent expression, findings that are consistent with previous observations in two model systems. Transgene-derived human factor VIII (hFVIII) protein activity mirrored native hFVIII in hemostatic ability. No inhibitor development, thromboses, deaths, or persistent changes in liver-function tests were observed.

CONCLUSIONS

Gene therapy with AAV5-hFVIII-SQ vector in participants with hemophilia A resulted in sustained, clinically relevant benefit, as measured by a substantial reduction in annualized rates of bleeding events and complete cessation of prophylactic factor VIII use in all participants who had received 4×10¹³ vg per kilogram or 6×10¹³ vg per kilogram of the gene therapy. (Funded by BioMarin Pharmaceutical; ClinicalTrials.gov number, NCT02576795; EudraCT number, 2014-003880-38.).

Extending recombinant factor IX Fc fusion protein dosing interval to 14 or more days in patients with hemophilia B

BACKGROUND

In the phase 3 B-LONG study (NCT01027364), prophylaxis with recombinant factor IX Fc fusion protein (rFIXFc) every 7 to >14 days was associated with low annualized bleed rates (ABRs) in males aged ≥12 years with severe hemophilia B. The long-term safety and efficacy of rFIXFc prophylaxis was confirmed in the B-YOND study (NCT01425723), an extension of the B-LONG clinical trial.

OBJECTIVE

The aim of this post-hoc analysis was to evaluate the efficacy of a ≥14-day rFIXFc dosing interval in patients treated prophylactically during B-LONG or B-YOND.

METHODS

The analysis included 22 patients aged ≥12 years who received prophylactic rFIXFc with a ≥14-day dosing interval at any time during B-LONG or B-YOND up until the second interim analysis of B-YOND (September 2015).

RESULTS

The median (interquartile range [IQR]) rFIXFc exposure on the ≥14-day dosing interval was 3.4 (1.8-4) years. Patients treated with a ≥14-day dosing interval were well controlled with a median (IQR) overall ABR of 1.6 (0.6-2.7) and a median (IQR) spontaneous ABR of 0.7 (0.3-1.1) in 18 evaluable patients. A rFIXFc dosing interval of ≥14 days was well tolerated, with no new safety concerns identified.

CONCLUSION

Most patients on rFIXFc prophylaxis, with a dosing interval of ≥14 days, remained well controlled; ABRs were consistent with those reported in the overall study population. A ≥14-day dosing interval can be utilized in some well controlled individuals and reduces the burden imposed by frequent prophylactic injections while maintaining adequate bleed suppression.

von Willebrand Factor Activity Detected in a Monoclonal Antibody-based ELISA: an Alternative to the Ristocetin Cofactor Platelet Agglutination Assay for Diagnostic Use

The monoclonal antibody RFF-VIII:R/1 recognises an epitope on von Willebrand factor involved in its interaction with GPIbα. A two-site, solid phase ELISA has been established using RFF-VIII:R/1 as the solid-phase, capture antibody and an enzyme-conjugated, polyclonal antibody to human VWF, which provides an assay for VWF functional activity with a detection limit of 0.5 U/dl VWF and an interassay %CV<10. Plasma from 192 VWD patients (48 studied retrospectively; 144 prospectively) showed VWF levels of <50 U/dl in type 1 patients (n = 156), <25 U/dl in type 2A (n = 26) and <35 U/dl in type 2B (n = 8) which, in type 1 and 2A patients, correlated with RiCoF activity (r >0.82). In plasma from patients with type 1 VWD values of VWF in the Mab-based ELISA were similar to levels of VWF:Ag measured in a polyclonal antibody-based ELISA (r >0.87) but were significantly lower than VWF:Ag in type 2A and 2B plasmas (p <0.0005), allowing discrimination of variant VWD. The Mab-based ELISA has advantages of sensitivity and reproducibility over the RiCoF assay to measure VWF activity and can be used to analyse stored samples. In conjunction with an ELISA for VWF:Ag and VWF multimer analysis, it provides a reliable method, for the laboratory diagnosis of VWD.

Absence of Inhibitors in Previously Untreated Patients with Severe Haemophilia A after Exposure to a Single Intermediate Purity Factor VIII Product

Use of high purity and recombinant factor VIII (FVIII) concentrates has been thought to be associated with an increased incidence of FVIII inhibitors in patients with severe haemophilia A. Comparison with comparable historical control groups has suggested that the true incidence of inhibitors in patients with severe haemophilia A was ~20-25%, similar to the incidence seen with new high purity and recombinant FVIII products.

We have conducted a study of inhibitor development in a cohort of 37 boys with severe haemophilia A (VIII: C <2 u/dl) exposed only to a single FVIII concentrate (BPL 8Y) with no previous blood or blood product exposure. This factor VIII concentrate is an intermediate purity product with a specific activity of ~2 IU/mg protein and contains well preserved von Willebrand factor multimers. It is manufactured by conventional fractionation technologies and terminally dry heat treated at 80° C for 72 h.

AAV5-Factor VIII Gene Transfer in Severe Hemophilia A

BACKGROUND

Patients with hemophilia A rely on exogenous factor VIII to prevent bleeding in joints, soft tissue, and the central nervous system. Although successful gene transfer has been reported in patients with hemophilia B, the large size of the factor VIII coding region has precluded improved outcomes with gene therapy in patients with hemophilia A.

METHODS

We infused a single intravenous dose of a codon-optimized adeno-associated virus serotype 5 (AAV5) vector encoding a B-domain-deleted human factor VIII (AAV5-hFVIII-SQ) in nine men with severe hemophilia A. Participants were enrolled sequentially into one of three dose cohorts (low dose [one participant], intermediate dose [one participant], and high dose [seven participants]) and were followed through 52 weeks.

RESULTS

Factor VIII activity levels remained at 3 IU or less per deciliter in the recipients of the low or intermediate dose. In the high-dose cohort, the factor VIII activity level was more than 5 IU per deciliter between weeks 2 and 9 after gene transfer in all seven participants, and the level in six participants increased to a normal value (>50 IU per deciliter) that was maintained at 1 year after receipt of the dose. In the high-dose cohort, the median annualized bleeding rate among participants who had previously received prophylactic therapy decreased from 16 events before the study to 1 event after gene transfer, and factor VIII use for participant-reported bleeding ceased in all the participants in this cohort by week 22. The primary adverse event was an elevation in the serum alanine aminotransferase level to 1.5 times the upper limit of the normal range or less. Progression of preexisting chronic arthropathy in one participant was the only serious adverse event. No neutralizing antibodies to factor VIII were detected.

CONCLUSIONS

The infusion of AAV5-hFVIII-SQ was associated with the sustained normalization of factor VIII activity level over a period of 1 year in six of seven participants who received a high dose, with stabilization of hemostasis and a profound reduction in factor VIII use in all seven participants. In this small study, no safety events were noted, but no safety conclusions can be drawn. (Funded by BioMarin Pharmaceutical; ClinicalTrials.gov number, NCT02576795 ; EudraCT number, 2014-003880-38 .).

Targeting of Antithrombin in Hemophilia A or B with RNAi Therapy

BACKGROUND

Current hemophilia treatment involves frequent intravenous infusions of clotting factors, which is associated with variable hemostatic protection, a high treatment burden, and a risk of the development of inhibitory alloantibodies. Fitusiran, an investigational RNA interference (RNAi) therapy that targets antithrombin (encoded by SERPINC1), is in development to address these and other limitations.

METHODS

In this phase 1 dose-escalation study, we enrolled 4 healthy volunteers and 25 participants with moderate or severe hemophilia A or B who did not have inhibitory alloantibodies. Healthy volunteers received a single subcutaneous injection of fitusiran (at a dose of 0.03 mg per kilogram of body weight) or placebo. The participants with hemophilia received three injections of fitusiran administered either once weekly (at a dose of 0.015, 0.045, or 0.075 mg per kilogram) or once monthly (at a dose of 0.225, 0.45, 0.9, or 1.8 mg per kilogram or a fixed dose of 80 mg). The study objectives were to assess the pharmacokinetic and pharmacodynamic characteristics and safety of fitusiran.

RESULTS

No thromboembolic events were observed during the study. The most common adverse events were mild injection-site reactions. Plasma levels of fitusiran increased in a dose-dependent manner and showed no accumulation with repeated administration. The monthly regimen induced a dose-dependent mean maximum antithrombin reduction of 70 to 89% from baseline. A reduction in the antithrombin level of more than 75% from baseline resulted in median peak thrombin values at the lower end of the range observed in healthy participants.

CONCLUSIONS

Once-monthly subcutaneous administration of fitusiran resulted in dose-dependent lowering of the antithrombin level and increased thrombin generation in participants with hemophilia A or B who did not have inhibitory alloantibodies. (Funded by Alnylam Pharmaceuticals; ClinicalTrials.gov number, NCT02035605 .).

Long-term safety and efficacy of extended-interval prophylaxis with recombinant factor IX Fc fusion protein (rFIXFc) in subjects with haemophilia B

The safety, efficacy, and prolonged half-life of recombinant factor IX Fc fusion protein (rFIXFc) were demonstrated in the Phase 3 B-LONG (adults/adolescents ≥12 years) and Kids B-LONG (children <12 years) studies of subjects with haemophilia B (≤2 IU/dl). Here, we report interim, long-term safety and efficacy data from B-YOND, the rFIXFc extension study. Eligible subjects who completed B-LONG or Kids B-LONG could enrol in B-YOND. There were four treatment groups: weekly prophylaxis (20-100 IU/kg every 7 days), individualised prophylaxis (100 IU/kg every 8-16 days), modified prophylaxis (further dosing personalisation to optimise prophylaxis), and episodic (on-demand) treatment. Subjects could change treatment groups at any point. Primary endpoint was inhibitor development. One hundred sixteen subjects enrolled in B-YOND. From the start of the parent studies to the B-YOND interim data cut, median duration of rFIXFc treatment was 39.5 months and 21.9 months among adults/adolescents and children, respectively; 68/93 (73.1 %) adults/adolescents and 9/23 (39.1 %) children had ≥100 cumulative rFIXFc exposure days. No inhibitors were observed. Median annualised bleeding rates (ABRs) were low in all prophylaxis regimens: weekly (≥12 years: 2.3; <6 years: 0.0; 6 to <12 years: 2.7), individualised (≥12 years: 2.3; 6 to <12 years: 2.4), and modified (≥12 years: 2.4). One or two infusions were sufficient to control 97 % (adults/adolescents) and 95 % (children) of bleeding episodes. Interim data from B-YOND are consistent with data from B-LONG and Kids B-LONG, and confirm the long-term safety of rFIXFc, absence of inhibitors, and maintenance of low ABRs with prophylactic dosing every 1 to 2 weeks.

Predicting the outcomes of using longer-acting prophylactic factor VIII to treat people with severe hemophilia A: a hypothetical decision analysis

Essentials No randomized trials have compared long-acting factor VIII (FVIII) with currently used products. A comparison was undertaken using a decision model to predict FVIII use and number of bleeds. In the base case, longer acting FVIII reduced factor use by 17% while resulting in similar bleeds. The value of longer acting FVIII will be largely determined by existing regimens and unit price. Click to hear Prof. Makris's presentation on new treatments in hemophilia SUMMARY: Background Recently, factor VIII (FVIII) products with longer half-lives, such as recombinant FVIII Fc fusion protein (rFVIIIFc), have become available. Use of longer-acting FVIII products will largely depend on effectiveness and cost; no direct evaluations have compared these parameters between conventional and longer-acting FVIII therapies. Objectives To present a hypothetical decision analysis, combining evidence from multiple sources to estimate bleeding frequency, resource use and cost of longer-acting prophylactic products, such as rFVIIIFc, vs. conventional recombinant FVIII (rFVIII). Patients/Methods The decision model used published pharmacokinetic parameters, bleeding frequency vs. time information below a 1-IU dL-1 FVIII trough level, and adherence. Prophylactic treatment scenarios were modelled for a hypothetical patient with severe hemophilia A (<1 IU/dL) receiving rFVIIIFc or rFVIII. Results Infusing twice weekly with rFVIIIFc 42.7 IU kg-1 per dose required less clotting factor than infusing every 56 h with rFVIII 33.75 IU kg-1 per dose; annual bleeding rates were similar. Base case analysis suggested that total FVIII costs were equated when rFVIIIFc cost 1.18 times more per IU than rFVIII, assuming similar adherence. Other modelled scenarios produced similar results, although differences in FVIII consumption were particularly sensitive to assumptions regarding frequency and dose of the rFVIII and rFVIIIFc regimens. For example, decreasing rFVIII from 33.75 IU kg-1 to 30 IU kg-1 per dose decreased the price factor to 1.05. Conclusions Longer-acting FVIII products may reduce FVIII consumption and infusion frequency without compromising hemostatic effect; this should be considered along with other factors (e.g. adherence and underlying FVIII regimen) when evaluating a suitable price for these agents.

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.

Phase 3 study of recombinant factor IX Fc fusion protein in hemophilia B

BACKGROUND

Prophylactic factor replacement in patients with hemophilia B improves outcomes but requires frequent injections. A recombinant factor IX Fc fusion protein (rFIXFc) with a prolonged half-life was developed to reduce the frequency of injections required.

METHODS

We conducted a phase 3, nonrandomized, open-label study of the safety, efficacy, and pharmacokinetics of rFIXFc for prophylaxis, treatment of bleeding, and perioperative hemostasis in 123 previously treated male patients. All participants were 12 years of age or older and had severe hemophilia B (endogenous factor IX level of ≤2 IU per deciliter, or ≤2% of normal levels). The study included four treatment groups: group 1 received weekly dose-adjusted prophylaxis (50 IU of rFIXFc per kilogram of body weight to start), group 2 received interval-adjusted prophylaxis (100 IU per kilogram every 10 days to start), group 3 received treatment as needed for bleeding episodes (20 to 100 IU per kilogram), and group 4 received treatment in the perioperative period. A subgroup of group 1 underwent comparative sequential pharmacokinetic assessments of recombinant factor IX and rFIXFc. The primary efficacy end point was the annualized bleeding rate, and safety end points included the development of inhibitors and adverse events.

RESULTS

As compared with recombinant factor IX, rFIXFc exhibited a prolonged terminal half-life (82.1 hours) (P<0.001). The median annualized bleeding rates in groups 1, 2, and 3 were 3.0, 1.4, and 17.7, respectively. In group 2, 53.8% of participants had dosing intervals of 14 days or more during the last 3 months of the study. In groups 1, 2 and 3, 90.4% of bleeding episodes resolved after one injection. Hemostasis was rated as excellent or good during all major surgeries. No inhibitors were detected in any participants receiving rFIXFc; in groups 1, 2, and 3, 73.9% of participants had at least one adverse event, and serious adverse events occurred in 10.9% of participants. These events were mostly consistent with those expected in the general population of patients with hemophilia.

CONCLUSIONS

Prophylactic rFIXFc, administered every 1 to 2 weeks, resulted in low annualized bleeding rates in patients with hemophilia B. (Funded by Biogen Idec; ClinicalTrials.gov number, NCT01027364.).

The incidence and magnitude of fibrinolytic activation in trauma patients

BACKGROUND

Trauma is a global disease, with over 2.5 million deaths annually from hemorrhage and coagulopathy. Overt hyperfibrinolysis is rare in trauma, and is associated with massive fatal injuries. Paradoxically, clinical trials suggest a much broader indication for antifibrinolytics.

OBJECTIVE

To determine the incidence and magnitude of fibrinolytic activation in trauma patients and its relationship to clot lysis as measured by thromboelastometry.

METHODS

A prospective cohort study of 303 consecutive trauma patients admitted between January 2007 and June 2009 was performed. Blood was drawn on arrival for thromboelastometry (TEM) and coagulation assays. Follow-up was until hospital discharge or death. TEM hyperfibrinolysis was defined as maximum clot lysis of > 15%. Fibrinolytic activation (FA) was determined according to plasmin-antiplasmin (PAP) complex and D-dimer levels. Data were collected on demographics, mechanism, severity of injury, and baseline vital signs. The primary outcome measure was 28-day mortality. The secondary outcome measures were 28-day ventilator-free days and 24-h transfusion requirement.

RESULTS

Only 5% of patients had severe fibrinolysis on TEM, but 57% of patients had evidence of 'moderate' fibrinolysis, with PAP complex levels elevated to over twice normal (> 1500 μg L(-1)) without lysis on TEM. TEM detected clot lysis only when PAP complex levels were increased to 30 times normal (P < 0.001) and antiplasmin levels were < 75% of normal. Patients with FA had increased 28-day mortality as compared with those with no FA (12% vs. 1%, P < 0.001), fewer ventilator-free days, and longer hospital stay.

CONCLUSIONS

FA occurs in the majority of trauma patients, and the magnitude of FA correlates with poor clinical outcome. This was not detected by conventional TEM, which is an insensitive measure of endogenous fibrinolytic activity.

Access to primary dental care for patients with inherited bleeding disorders

Patients with inherited bleeding disorders (IBD) can face difficulty in accessing primary dental care either due to disease-specific or patient-related barriers. This can lead to poor oral health and increase the need for more invasive dental treatment. This study aimed to highlight actual and perceived barriers that IBD patients from the East London area were experiencing. It also gives an overview of the experience history of the General Dental Practitioners (GDPs) treating these patients. Information was gathered via pre-designed surveys as part of a service development audit. A total of 105 anonymous patient surveys and 50 GDP surveys were completed between December 2010 and July 2011. The patient survey highlighted more patients to be affected by patient-related than disease-specific barriers to access dental care. The GDP survey identified that just under half of GDPs questioned were not confident in the dental management of patients with bleeding disorders. Identifying misconceptions and barriers to access primary dental care will enable further development of our shared-care approach between General Dental Services, Hospital or Community Dental Services and Haemophilia Centre, optimizing regular preventative advice and follow ups to prevent dental disease and invasive dental treatment requiring haemostatic treatment.

Fatal postoperative pulmonary embolism in mild haemophilia

The use of thromboprophylaxis in patients with haemophilia receiving factor replacement is often not considered necessary, but remains an area of debate. In this report we describe a patient with mild haemophilia A, who underwent major pelvic surgery. He had several underlying risk factors associated with the development of thromboembolism, and ultimately died as a direct consequence of multiple pulmonary emboli. The need for thromboprophylaxis and the risk balance ratio should always be considered in patients with bleeding disorders if they fall into what would otherwise be high-risk category for hospital acquired venous thromboembolism.

Thrombosis and inflammatory bowel disease

Interaction between thrombosis and inflammation is increasingly recognized. With this, interest has arisen in the role of thrombosis in inflammatory conditions, including the inflammatory bowel diseases. Although the association between active inflammatory bowel disease and thromboembolic complications has long been known, there has been a resurgence in research into the role of thrombosis and the hemostatic system in the pathogenesis of both ulcerative colitis and Crohn's disease. Here we review the increased frequency of thromboembolic complications occurring in patients with inflammatory bowel disease; whether thrombosis might play a part in the initiation and maintenance of inflammation in inflammatory bowel disease; abnormalities of the coagulation system found in patients with inflammatory bowel disease; platelet dysfunction in inflammatory bowel disease; the mechanisms by which hemostatic processes might be proinflammatory in inflammatory bowel disease; and how these interactions might impact not only on the prevention of complications, but also on the treatment of the underlying inflammation in inflammatory bowel disease.

A framework for genetic service provision for haemophilia and other inherited bleeding disorders

This framework document offers guidance to patients, doctors, nurses, laboratory scientists, funders and hospitals on the provision of clinical and laboratory genetic services for haemophilia. With recent advances in molecular laboratory techniques it is now possible to give the vast majority of individual patients and family members very reliable genetic information. To enable these genetic data to be used for both the optimal treatment of patients with inherited bleeding disorders and for appropriate reproductive decisions in carriers, there needs to be a clear and robust framework for systematically acquiring the necessary clinical, personal, family and laboratory information upon which decisions can be made. This document provides guidance on the range and standards of clinical and laboratory genetic services which should be offered to patients and their families. Included are arrangements for genetic counselling and testing (including consent and confidentially issues), management of early pregnancy, standards for laboratory genetic services, as well as advice on data storage, security and retrieval.

The prevalence of the cysteine1584 variant of von Willebrand factor is increased in type 1 von Willebrand disease: co-segregation with increased susceptibility to ADAMTS13 proteolysis but not clinical phenotype

The molecular pathogenesis of type 1 von Willebrand disease (VWD) is uncertain in most patients. We examined 30 type 1 VWD families in the UK Haemophilia Centre Doctors' Organization study. Heterozygosity for Y/C1584 was present in eight of 30 (27%) families and 19 of 76 (25%) individuals with type 1 VWD recruited into the study. Eighteen (95%) of these 19 individuals were blood group O. C1584 did not co-segregate with VWD in four families, and co-segregated in one family; the results were equivocal in three families. In all families increased susceptibility of von Willebrand factor (VWF) to a disintegrin and metalloprotease with thrombospondin motifs (ADAMTS) 13 proteolysis co-segregated with C1584 in affected and unaffected individuals. These data show that C1584, associated with blood group O, is prevalent among patients with type 1 VWD but not necessarily causative of disease and should not be used in isolation to diagnose VWD. Increased susceptibility of C1584 VWF to ADAMTS13 proteolysis may be physiologically significant and increase an individual's risk of bleeding and presenting with VWD.

Versatile Peptide Dendrimers for Nucleic Acid Delivery

Dendrimers are nonviral vectors that have attracted interest on account of a number of features. They are structurally versatile because their size, shape, and surface charge can be selectively altered. Here we examine the functions of a new family of composite dendrimers that were synthesized with lipidic amino acid cores. These dendrimers are bifunctional because they are characterized by positively charged (lysine) modules for interaction with nucleic acids and neutral lipidic moieties for membrane lipid-bilayer transit. We assessed their structure-function correlations by a combination of molecular and biophysical techniques. Our assessment revealed an unexpected pleitropy of functions subserved by these vectors that included plasmid and oligonucleotide delivery. We also generated a firefly luciferase cell line in which we could modulate luciferase activity by RNA interference. We found that these vectors could also mediate RNA suppression of luciferase expression by delivering double-stranded luciferase transcripts generated in vitro. The structural uniqueness of these lipidic peptide dendrimers coupled with their ease and specificity of assembly and the versatility in their choice of cargo, puts them in a new category of macromolecule carriers. These vectors, therefore, have potential applications as epigenetic modifiers of gene function.

The safety and efficacy of recombinant human blood coagulation factor IX in previously untreated patients with severe or moderately severe hemophilia B

This international clinical trial evaluated the safety and efficacy of recombinant factor IX (rFIX) in previously untreated patients (PUPs) with severe or moderately severe hemophilia B (FIX activity, < or = 3 IU/dL). Sixty-three PUPs aged younger than 1 month to 14 years received rFIX (median treatment duration, 37 months; range, 4-64 months). Mean rFIX recovery (0.68 +/- 0.27 IU/dL per IU/kg) remained constant over 5 years and was similar in infants (1 month to < 2 years) and children (2 to < 12 years). Fifty-four PUPs used rFIX (median dose, 62.7 IU/kg per infusion; range, 8.2-292 IU/kg) to treat 997 hemorrhages. Bleeding was well controlled, with 75% of hemorrhages requiring only one rFIX infusion. Response to rFIX was "excellent" or "good" in 94% of cases. Effective hemostasis was achieved in 32 PUPs receiving rFIX for routine prophylaxis, with 91% of prophylaxis responses rated "excellent." rFIX administered for 30 surgical procedures in 23 PUPs achieved hemostasis for all rated procedures. Five patients experienced allergic-type manifestations, including 2 (3%) patients who developed FIX inhibitors (both > 5 BU/dL). rFIX was well tolerated, with no associated thrombotic events or evidence of viral transmission. These data indicate that rFIX is a safe and effective treatment for PUPs with hemophilia B.

The effects of folic acid supplements on coagulation status in pregnancy

Thromboembolic disease remains the leading cause of maternal death in the UK. Recent literature has proposed that folate status is a strong predictor for venous thrombosis. Using thrombelastography (TEG((R))), we tested the hypothesis that folic acid supplementation is associated with a reduction in whole blood coagulability. Blood samples and questionnaire data were obtained at a mean gestation of 13.6 weeks (SD: 3.8, range: 6-38 weeks) from unselected consecutive women attending for their antenatal booking scan. Of 588 patients, 439 (74.7%) took folic acid. All TEG((R)) parameters were less hypercoagulable in women that had taken folic acid compared with those that had not: mean maximum amplitude (MA) 60.3 versus 62.1; mean difference 1.8; 95% confidence interval 0.8, 2.8; P = 0.0001; mean coagulation index (CI) 0.54 versus 0.85; mean difference 0.31; 95% confidence interval 0.11, 0.5; P = 0.002. There was no difference in the incidence of the homozygous MTHFR mutation in patients taking folic acid (5.53%) compared with those that were not (4.08%). This study suggests that benefit may be derived from longer-term treatment, although large multicentre studies are required to determine whether the relative hypocoagulability is associated with a reduction in risk of venous thrombosis.

Coagulation status and complications of pregnancy

INTRODUCTION

There is much interest in the relationship between coagulation status and complications of pregnancy. The thrombelastograph (TEG) has been proposed as a useful, inexpensive tool to screen for patients with hypercoagulable states.

MATERIALS AND METHODS

We investigated 588 unselected pregnant women at booking, obtaining blood samples for TEG and thrombophilia investigation. Pregnancy outcome data was recorded.

RESULTS

We found significant correlations between TEG parameters and the Prothrombin time (PT) and Activated Partial Thromboplastin time (APTT) (p<0.01) and with plasma Antithrombin level (p<0.01). There was no correlation between TEG and other thrombophilic defects (protein C, protein S, Factor V Leiden mutation, Prothrombin G20210A mutation, MTHFR C677T mutation and Lupus Anticoagulant). There was a significant association of TEG parameters with mid-trimester loss (MTL) but not with other adverse pregnancy outcomes.

CONCLUSIONS

The correlation between TEG and PT, APTT and antithrombin level supports its value in providing a global measure of haemostasis. Coagulation status at booking is associated with increased risk of MTL but not with complications occurring later in pregnancy.

Fish as bioreactors: transgene expression of human coagulation factor VII in fish embryos

A plasmid containing human coagulation factor VII (hFVII) complementary DNA regulated by a cytomegalovirus promoter was microinjected into fertilized eggs of zebrafish, African catfish, and tilapia. The active form of hFVll was detected in the fish embryos by various assays. This positive expression of human therapeutic protein in fish embryos demonstrates the possibility of exploitation of transgenic fish as bioreactors.

The diagnosis of von Willebrand disease: a guideline from the UK Haemophilia Centre Doctors' Organization

von Willebrand disease (VWD) is the commonest inherited bleeding disorder. However, despite an increasing understanding of the pathophysiology of VWD, the diagnosis of VWD is frequently difficult because of uncertainty regarding the relationship between laboratory assays and function in vivo. The objective of this guideline is to provide contemporary advice on a rational approach to the diagnosis of VWD. This is the second edition of this UK Haemophilia Centre Doctors' Organisation (UKHCDO) guideline and supersedes the previous edition which was published in 1997.

Management of von Willebrand disease: a guideline from the UK Haemophilia Centre Doctors' Organization

von Willebrand disease (VWD) is the commonest inherited bleeding disorder. The aim of therapy for VWD is to correct the two defects of haemostasis in this disorder, impaired primary haemostasis because of defective platelet adhesion and aggregation and impaired coagulation as a result of low levels of factor VIII. The objective of this guideline is to inform individuals making choices about the treatment and management of VWD including the use of therapeutic products. This is the second edition of this UK Haemophilia Centre Doctors' Organization (UKHCDO) guideline and supersedes the previous edition which was published in 1994.

Markers of platelet activation, thrombin generation and fibrinolysis in women with sickle cell disease: effects of differing forms of hormonal contraception

OBJECTIVE

To examine laboratory markers of platelet activation, thrombin generation and fibrinolysis in women with sickle cell disease (SCD) using the combined oral contraceptive pill (COCP), progestogen only (PO) contraception and non-hormonal contraception.

DESIGN

A prospective observational study set in two teaching hospitals in the London region.

METHOD

Forty-four women with SCD in steady haematological state using differing hormonal contraception were recruited and venesection was performed at standardised times for the measurements of markers of platelet activation, thrombin generation and fibrinolysis.

OUTCOME MEASURES

Prothrombin fragment1+2, plasmin alpha2 antiplasmin complexes, platelet factor 4 (PF-4), beta-thromboglobulin and free protein S antigen (PS-Ag).

RESULTS

PS-Ag was decreased and PF-4 increased in all women while the other haemostatic variables were within normal reference ranges. However, there was no statistically significant differences in the measurements of all the haemostatic variables between the three groups of sickle cell women (Kruskal-Wallis, P > 0.05).

CONCLUSION

There is anxiety about prescribing the COCP in women with SCD based on the assumption that risk of venous thromboembolism may be compounded by the underlying disease process that occurs with these women. The observed data suggest that SCD women who use the COCP have haemostatic markers which are not statistically different compared with similar women who use PO contraception or non-hormonal contraception. However, a randomized interventional trial would be necessary to evaluate further the safety aspect of COCP use in this group of women.

Use of recombinant factor IX in subjects with haemophilia B undergoing surgery

Recombinant human FIX (rFIX) was evaluated in 28 subjects, including 26 with mild, moderate, or severe haemophilia B and two haemophilia B carriers undergoing 36 surgical procedures. Preoperative rFIX dose was highly correlated with postinfusion FIX activity, r=0.61, P=0.0158. Peri- and post-operative estimated blood loss was similar to that expected in non-haemophilic individuals, and haemostasis was rated as excellent or good in 34 of 35 (97.1%) of the operative procedures. Transfusions were required in five of 36 (13.9%) procedures, including one liver transplantation, and three knee and one hip arthroplasties. Adverse events occurred in 15 of 28 (53.6%) subjects, but there were no perioperative haemorrhages, thromboembolic events, coagulation activation, viral transmission, or inhibitor formation. A transient low-responding FIX inhibitor developed in one subject preoperatively, but required no change in treatment and resolved 15 months later. Thus, rFIX was found to be safe and effective in achieving haemostasis in subjects with FIX deficiency undergoing surgery.

Simple shifts in redox/thiol balance that perturb blood coagulation

The biological chemistry that underlies and regulates the blood coagulation cascade is not fully understood. To begin to understand this, we performed clotting assays under various redox conditions. By varying the amount of oxidant and/or antioxidant in these assays, we observed that both the intrinsic/tenase complex and the extrinsic pathways were susceptible to shifts in the thiol/redox balance. We established a dichotomy where blood clotting via the intrinsic pathway was sensitive to oxidation whereas the tissue factor or extrinsic pathway was more sensitive to reduction. These differential inhibitory effects present a conceptual mechanism for selective modulation of the activities of clotting factors specific for the respective pathways. These data also suggest that blood clotting may be influenced by unidentified redox or thiol equilibria.

Human recombinant factor IX: safety and efficacy studies in hemophilia B patients previously treated with plasma-derived factor IX concentrates

Human plasma-derived factor IX (pdFIX) concentrates are routinely used to treat patients with hemophilia B, an X-linked bleeding disorder that affects 1 in 30 000 males, but concerns remain regarding transmission of blood-borne pathogens. Therefore, the safety and efficacy of recombinant human factor IX (rFIX) were evaluated. A 20-center international trial was conducted in previously treated patients with severe or moderate (< 5 IU/dL factor IX activity) hemophilia B. Participants received rFIX for pharmacokinetic studies, treatment of or prophylaxis against hemorrhage, or surgical hemostasis, and were assessed at 3-month intervals for 2 years. Fifty-six subjects were treated. Mean incremental rFIX recovery was 0.75 IU/dL per IU/kg, 30% lower than expected for pdFIX, although the mean half-life was similar. Pharmacokinetic parameters were stable over time. Somewhat lower recoveries were seen in subjects younger than 15 years of age and in those with no detectable factor IX antigen. A total of 7362 infusions of rFIX were administered. All 1796 hemorrhages were controlled, 80.9% of which required only one rFIX infusion. Effective hemostasis was also achieved in prophylactic and surgical settings. One individual developed a low titer (1.2 Bethesda unit) transient inhibitor that spontaneously resolved. rFIX was not associated with serious adverse events, thrombogenicity, or virus transmission. rFIX is safe and effective for the treatment of hemophilia B. Despite a lower recovery compared with pdFIX, rFIX controlled hemorrhage in a wide variety of settings and may provide a safety advantage in terms of risk from blood-borne pathogens.

Aberrant dimerization of von Willebrand factor as the result of mutations in the carboxy-terminal region: identification of 3 mutations in members of 3 different families with type 2A (phenotype IID) von Willebrand disease

The 3' end of the VWF gene was screened in the affected members of 3 different families with type 2A (phenotype IID) von Willebrand disease (vWD). Exons 49 to 52 of the VWF gene were amplified and screened for mutations by chemical cleavage mismatch detection. Mismatched bands were detected in exon 52 of 2 patients and in exon 51 of a third patient. Using direct DNA sequencing, a heterozygous G8562A transition leading to a Cys2008Tyr substitution was found in all the patients in family 1, and a T8561A transversion leading to a Cys2008Ser substitution was found in both patients from family 2. In a patient from a third family, an 8-base deletion from nucleotide 8437 to 8444 was identified in exon 51. The 2 mutations in exon 52 were reproduced by in vitro site-directed mutagenesis of full-length von Willebrand factor (vWF) cDNA and transiently expressed in COS-7 cells. The corresponding recombinant VWFs for these 2 mutations exhibited the typical aberrant vWF:Ag multimer pattern seen in the plasma of the patients. These 3 mutations demonstrate the importance of other carboxy-terminal cysteines in addition to the reported Cys2010 residue, in the normal dimerization of vWF, and their essential role in the assembly of normal multimeric vWF. (Blood. 2001;98:674-680)