Recombinant factor IX Fc for the treatment of hemophilia B

Current hemophilia B treatment guidelines recommend routine prophylaxis with factor IX (FIX) replacement products, tailored to maintain plasma activity at levels that will prevent bleeds. However, plasma FIX activity may not be the primary determinant or best indicator of hemostatic efficacy due to its extravascular distribution. FIX replacement therapy has evolved to include extended half-life (EHL) products that provide effective bleed protection when administered at intervals of 7 days or longer. rFIXFc is a recombinant fusion protein with an extended circulation time. rFIXFc has a biodistribution profile consistent with distribution into extravascular space, where it may support hemostasis at sites of vessel injury independent of circulating plasma activity levels. The safety and efficacy of rFIXFc prophylaxis is well established in adults, adolescents and children including previously untreated patients with hemophilia B, with substantial evidence from clinical trials and real-world clinical practice. This review describes the pharmacokinetic characteristics of rFIXFc, summarizes available safety and efficacy data, and evaluates the use of rFIXFc in special populations. Current hemophilia B treatment challenges, including target FIX plasma levels, perioperative use, and management of patients with comorbidities, are discussed together with the potential role of EHL products in the future treatment landscape of hemophilia B.

Etranacogene dezaparvovec gene therapy for haemophilia B (HOPE-B): 24-month post-hoc efficacy and safety data from a single-arm, multicentre, phase 3 trial

BACKGROUND

Etranacogene dezaparvovec, the first gene therapy approved for haemophilia B treatment, was shown to be superior to treatment with continuous prophylactic factor IX in terms of bleeding protection 18 months after gene therapy in a phase 3 trial. We report post-hoc 24-month efficacy and safety data from this trial to evaluate the longer-term effects of etranacogene dezaparvovec in individuals with haemophilia B.

METHODS

The phase 3 HOPE-B trial enrolled males aged 18 years or older with inherited haemophilia B, classified as severe (plasma factor IX activity level <1%) or moderately severe (plasma factor IX activity level ≥1% and ≤2%), with a severe bleeding phenotype and who were on stable continuous factor IX prophylaxis. Participants were treated with a single infusion of etranacogene dezaparvovec (2 × 1013 genome copies per kg of bodyweight). The primary endpoint, reported previously, was non-inferiority of the annualised bleeding rate (ABR) during the 52 weeks following stable factor IX expression (defined as months 7-18 after treatment) versus an at least 6-month lead-in period in which participants received their usual continuous factor IX prophylaxis, and is updated here up to month 24. Additional, post-hoc efficacy analyses, including adjusted ABR, factor IX activity, participants within factor IX ranges, and factor IX use, and safety analyses were performed at 24 months after gene therapy. Data were analysed in the full analysis set, which comprised the 54 patients who received at least a partial dose of gene therapy. The trial is ongoing and is registered with ClinicalTrials.gov, number NCT03569891.

FINDINGS

The study began on June 27, 2018, and participants were treated between January, 2019, and March, 2020; the date of data cutoff was April 21, 2022. 54 adult males (40 White, two Asian, one Black or African American, 11 other or missing) received a single intravenous infusion of etranacogene dezaparvovec and were followed for a median of 26·51 months (IQR 24·54-27·99), after a lead-in period of 7·13 months (6·51-7·82). In the updated analysis comparing months 7-24 after gene therapy to the lead-in period, mean adjusted ABR significantly reduced from 4·18 to 1·51 (p=0·0002) for all bleeds and from 3·65 to 0·99 (p=0·0001) for factor IX-treated bleeds. During each 6-month period after gene therapy, at least 67% of participants experienced no bleeding (36 of 54 during months 0-6 and stable thereafter), compared with 14 (26%) of 54 during the lead-in period. 24 months after gene therapy, 1 (2%) participant had one-stage factor IX activity less than 5%, whereas 18 (33%) had factor IX activity more than 40% (non-haemophilia range), with mean factor IX activity stable and sustained at 36·7% (SD 19·0%). 52 (96%) of 54 participants expressed endogenous factor IX, remaining free of factor IX prophylaxis at month 24. No new safety concerns were identified and no treatment-related serious adverse events or treatment-related deaths occurred. The most common treatment-related adverse events were an increase in alanine aminotransferase (nine [17%] of 54 patients), headache (eight [15%]), influenza-like illness (seven [13%]), and an increase in aspartate aminotransferase (five [9%]).

INTERPRETATION

By providing durable disease correction throughout the 24 months after gene therapy, etranacogene dezaparvovec provides a safe and effective therapeutic option for patients with severe or moderately severe haemophilia B.

FUNDING

uniQure and CSL Behring.

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.

Efficacy and Safety of Early Administration of 4-Factor Prothrombin Complex Concentrate in Patients With Trauma at Risk of Massive Transfusion: The PROCOAG Randomized Clinical Trial

Importance

Optimal transfusion strategies in traumatic hemorrhage are unknown. Reports suggest a beneficial effect of 4-factor prothrombin complex concentrate (4F-PCC) on blood product consumption.

Objective

To investigate the efficacy and safety of 4F-PCC administration in patients at risk of massive transfusion.

Design, Setting, and Participants

Double-blind, randomized, placebo-controlled superiority trial in 12 French designated level I trauma centers from December 29, 2017, to August 31, 2021, involving consecutive patients with trauma at risk of massive transfusion. Follow-up was completed on August 31, 2021.

Interventions

Intravenous administration of 1 mL/kg of 4F-PCC (25 IU of factor IX/kg) vs 1 mL/kg of saline solution (placebo). Patients, investigators, and data analysts were blinded to treatment assignment. All patients received early ratio-based transfusion (packed red blood cells:fresh frozen plasma ratio of 1:1 to 2:1) and were treated according to European traumatic hemorrhage guidelines.

Main Outcomes and Measures

The primary outcome was 24-hour all blood product consumption (efficacy); arterial or venous thromboembolic events were a secondary outcome (safety).

Results

Of 4313 patients with the highest trauma level activation, 350 were eligible for emergency inclusion, 327 were randomized, and 324 were analyzed (164 in the 4F-PCC group and 160 in the placebo group). The median (IQR) age of participants was 39 (27-56) years, Injury Severity Score was 36 (26-50 [major trauma]), and admission blood lactate level was 4.6 (2.8-7.4) mmol/L; prehospital arterial systolic blood pressure was less than 90 mm Hg in 179 of 324 patients (59%), 233 patients (73%) were men, and 226 (69%) required expedient hemorrhage control. There was no statistically or clinically significant between-group difference in median (IQR) total 24-hour blood product consumption (12 [5-19] U in the 4F-PCC group vs 11 [6-19] U in the placebo group; absolute difference, 0.2 U [95% CI, -2.99 to 3.33]; P = .72). In the 4F-PCC group, 56 patients (35%) presented with at least 1 thromboembolic event vs 37 patients (24%) in the placebo group (absolute difference, 11% [95% CI, 1%-21%]; relative risk, 1.48 [95% CI, 1.04-2.10]; P = .03).

Conclusions and Relevance

Among patients with trauma at risk of massive transfusion, there was no significant reduction of 24-hour blood product consumption after administration of 4F-PCC, but thromboembolic events were more common. These findings do not support systematic use of 4F-PCC in patients at risk of massive transfusion.

Trial Registration

ClinicalTrials.gov Identifier: NCT03218722.

First open-label, single-arm, prospective study of real-world use of FIX replacement therapy in a predominantly pediatric hemophilia B population in China

BACKGROUND

Nonacog alfa (recombinant factor IX [FIX]) is approved in China for the control and prevention of bleeding events in patients with hemophilia B. This was the first study to assess prophylaxis and on-demand therapy with recombinant FIX replacement in a real-world setting in China. This study aimed to evaluate the safety and efficacy of nonacog alfa in Chinese patients with hemophilia B.

METHODS

In this open-label, multicenter study (clinicaltrials.gov identifier NCT02336178), patients received on-demand or prophylactic treatment with intravenous nonacog alfa for approximately 6 months or 50 exposure days, whichever occurred first. The primary safety outcome was medically important events (i.e., development of FIX inhibitors, allergic reactions, and thrombotic events). Key secondary efficacy outcomes included the annualized bleeding rate for on-demand treatment and prophylaxis, response to on-demand treatment, the number of infusions per bleeding event, and the number of breakthrough bleeding events within 48 hours of prophylaxis.

RESULTS

Seventy male patients (mean [standard deviation] age 7.8 [7.2] years) were enrolled (on-demand, n = 37; prophylaxis, n = 57 [24 patients were included in both groups]). Thirty-eight (54%) patients had up to 50 FIX exposure days before the study. The only medically important event was a transient low-titer FIX inhibitor (incidence 1.4%, 95% confidence interval, 0-7.7). The mean annualized bleeding rate was 26.3 for on-demand treatment and 6.5 for prophylaxis. A mean (standard deviation) of 1.5 (1.7) nonacog alfa infusions were given per bleeding episode; 78.8% of episodes resolved with 1 infusion. Response was "excellent" or "good" for 88% of the on-demand infusions. Twenty-three bleeding events (n = 11 patients) occurred within 48 hours of 2032 prophylaxis doses (1.13%).

CONCLUSION

In the real-world setting, nonacog alfa is safe and effective for on-demand treatment and for prophylaxis for patients with hemophilia B in China.

Prophylaxis Using a Mixture of Plasma-Derived Activated Factor VII and Factor X (pdFVIIa/FX) in a Patient with Hemophilia B Complicated by Inhibitors and Allergy to Factor IX Concentrates: A Case Report

Treating patients with hemophilia and inhibitors is often problematic. The presence of inhibitors negatively impacts the effectiveness of treatment to achieve hemostasis especially in patients with hemophilia B, owing mainly to allergic reactions to factor IX (FIX) concentrates and the low success rate of immune tolerance therapy. A 9-month-old boy had intracranial hemorrhage and was diagnosed with hemophilia B. After replacement therapy, he developed inhibitors and an allergic reaction to FIX. Prophylactic therapy was initiated with recombinant activated factor VII (rFVIIa) and later switched to pdFVIIa/factor X (FX; 120 μg/kg as the FVII dose, every other day) because of a recurrence of intracranial hemorrhage. Since then, he remained well without life-threatening bleeding for more than 2 years. Our case suggests that pdFVIIa/FX may be useful for prophylactic therapy in hemophilia B complicated by inhibitors and allergic reaction to FIX concentrates.

Long-term safety and efficacy of rIX-FP prophylaxis with extended dosing intervals up to 21 days in adults/adolescents with hemophilia B

BACKGROUND

An international, multicenter extension study evaluated recombinant fusion protein linking recombinant coagulation factor IX (FIX) with recombinant human albumin (rIX-FP) in hemophilia B (FIX ≤ 2%) patients previously enrolled in a phase III study or who initiated rIX-FP prophylaxis following surgery.

OBJECTIVES

To investigate the long-term safety and efficacy of rIX-FP prophylaxis in adult previously treated patients (PTPs) with hemophilia B.

METHODS

Male PTPs were treated with a 7- (35-50 IU/kg), 10- or 14-day regimen (50-75 IU/kg). Patients ≥18 years who were well-controlled on a 14-day regimen for ≥6 months could switch to a 21-day regimen (100 IU/kg).

RESULTS

A total of 59 patients (aged 13-63 years) participated in the study. Following a single dose of 100 IU/kg rIX-FP, in patients eligible for the 21-day regimen, the mean terminal half-life was 143.2 hours. Mean steady-state FIX trough activity levels ranged from 22% with the 7-day regimen to 7.6% with the 21-day regimen. Median (Q1, Q3) annualized spontaneous bleeding rates were 0.00 (0.00, 1.67), 0.28 (0.00, 1.10), 0.37 (0.00, 1.68), and 0.00 (0.00, 0.45) for the 7-, 10-, 14-, and 21-day regimens, respectively. Comparable efficacy was demonstrated for both the 14- and 21-day regimens compared to the 7-day regimen. Overall, 96.5% of bleeding episodes were treated successfully with 1 to 2 rIX-FP infusions. No patients developed an inhibitor and treatment was well tolerated.

CONCLUSIONS

rIX-FP extended interval prophylaxis provides dosing flexibility and, in selected patients, a 21-day regimen may provide an alternative option to minimize treatment burden and individualize treatment.

Hemophilia - Impact of Recent Advances on Management

There have been numerous advances in the field of hemophilia management in the past decade, including long acting factor products, non-factor products, and potentially curative interventions such as gene therapy. Each of these interventions introduces exciting treatment modalities to patients with both hemophilia A and B, however they also pose a daunting array of possible management options. Adverse reactions to novel agents are being reported as more patients are treated and long-term sustainability of interventions such as gene therapy is yet to be determined. The practicing hematologist should be aware of the intricacies involved in customizing care for their individual patients and be aware of the monitoring strategies for each interventional strategy to avoid adverse events. Upfront cost vs. long term benefit should be considered as choices of treatment strategies are made, especially in resource poor countries. The goal of the newer agents is to decrease annualized bleed rates and avoid debilitating arthropathy. This article looks at current treatment models for prophylaxis and management of inhibitors, reviews the recent advances in the field (with bioengineered factor products, non-factor products and gene therapy) and summarizes the incorporation of these new interventions in the treatment plan for patients with hemophilia.

Nonacog Beta Pegol: A Review in Haemophilia B

Nonacog beta pegol [Refixia® (EU)] is an intravenously-administered, glycoPEGylated recombinant factor IX (FIX), with an extended terminal half-life. It is approved in the EU for the treatment and prophylaxis of bleeding in patients aged ≥ 12 years with haemophilia B. The therapeutic efficacy and safety of nonacog beta pegol was demonstrated in the phase 3 Paradigm trials in previously treated adolescents and adults with haemophilia B. In Paradigm 2, nonacog beta pegol showed good haemostatic effects when treating bleeds on-demand, and reduced annualized bleeding rates when used as a once-weekly prophylaxis. It also improved some health-related quality of life measures in adult patients. The longer-term efficacy of nonacog beta pegol was demonstrated in the open-label extension Paradigm 4 trial. In Paradigm 3, nonacog beta pegol effectively maintained intraoperative and postoperative haemostasis. Nonacog beta pegol was well tolerated in phase 3 clinical trials in patients with haemophilia B, with no evidence of FIX inhibitor formation, allergic reactions or thromboembolic complications. In conclusion, nonacog beta pegol is effective and well tolerated in the on-demand, prophylaxis and perioperative settings in adolescent and adults with haemophilia B. Its extended half-life allows for once-weekly prophylaxis. Therefore, nonacog beta pegol is a useful additional treatment option for patients with haemophilia B.

Clotting factor product administration and same-day occurrence of thrombotic events, as recorded in a large healthcare database during 2008-2013

BACKGROUND

Thrombotic events (TEs) are serious adverse events that can occur following administration of clotting factors (CFs).

OBJECTIVES

To evaluate occurrence of same-day TEs for different CF products and potential risk factors.

METHODS

A retrospective cohort study of individuals exposed to CF products during 2008-2013 was conducted using a large commercial insurance database. CF products were identified by procedure codes, and TEs were ascertained via diagnosis codes. Crude same-day TE rates (per 1000 persons exposed) were estimated overall and by congenital factor deficiency (CFD) status, CF products, age and gender. Multivariable logistic regression analyses were used to control for confounding. Laboratory analysis was used to compare the procoagulant activities of FIX products.

RESULTS

Of 3801 individuals exposed to CFs, 117 (30.8 per 1000) had same-day TEs recorded. The crude same-day TE rate was higher for CF users without CFD, 70.2 (102 of 1452), as compared with those with CFD, 6.4 (15 of 2349) (RR, 11.0; 95% CI, 6.4-18.9). For individuals without CFD, a significantly increased same-day TE risk was identified for factor IX complex (OR, 6.92; 95% CI, 3.11-15.40), factor VIIa (OR, 9.42; 95% CI, 4.99-17.78) and other products when compared with fibrin sealant. An increased risk of a TE was found with older age (≥ 45 years), history of TEs and underlying health conditions. The laboratory identified elevated procoagulant activity in Profilnine(®) and Benefix(®) .

CONCLUSIONS

The study shows an increased same-day TE risk for CF users without CFD and suggests substantial off-label CF use. The study findings also show elevated same-day TE rates for different CF products and suggest the importance of product properties and patient factors.

Risk of thromboembolic events after protocolized warfarin reversal with 3-factor PCC and factor VIIa

Bleeding events and life-threatening hemorrhage are the most feared complications of warfarin therapy. Prompt anticoagulant reversal aimed at replacement of vitamin K-dependent clotting factors is essential to promote hemostasis. A retrospective cohort study of warfarin-treated patients experiencing a life-threatening hemorrhage treated with an institution-specific warfarin reversal protocol (postimplementation group) and those who received the prior standard of care (preimplementation group) was performed. The reversal protocol included vitamin K, 3-factor prothrombin complex concentrate, and recombinant factor VIIa. Demographic and clinical information, anticoagulant reversal information, and all adverse events attributed to warfarin reversal were recorded. A total of 227 patients were included in final analysis, 109 in the preimplementation group and 118 in the postimplementation group. Baseline patient characteristics were similar in both groups, with the exception of higher average Sequential Organ Failure Assessment scores in the postimplementation group (P = .0005). The most common indication for anticoagulation reversal was intraparenchymal hemorrhage. Prereversal international normalized ratios (INRs) were similar in both groups. Attainment of INR normalization to less than 1.4 was higher, and rebound INR was lower in the postimplementation group (P < .0001; P = .0013). Thromboembolic complications were significantly higher in the postimplementation group (P = .003). Elevated baseline Sequential Organ Failure Assessment score and mechanical valve as an indication for anticoagulation were independently associated with thrombotic complications (P = .005). A warfarin reversal protocol consisting of 3-factor prothrombin complex concentrate, recombinant factor VIIa, and vitamin K more consistently normalized INR values to less than 1.4 as compared to the prior standard of care in a diverse patient population. This success came at the cost of a 2-fold increase in risk of thromboembolic complications.

Desensitization and immune tolerance induction in children with severe factor IX deficiency; inhibitors and adverse reactions to replacement therapy: a case-report and literature review

Hemophilia B is a rare X-linked recessive disorder with plasma factor IX (FIX) deficiency. 1-3% of patients treated with exogenous FIX-containing products develop inhibitors (i.e. polyclonal high affinity immunoglobulins) that neutralize the procoagulant activity of a specific coagulation factor. Although the incidence of inhibitors in hemophilia B patients is low, most are "high titer" and frequently associated with the development of severe allergic or anaphylactic reactions. Immune tolerance induction as a strategy for inhibitor eradication was first described in 1984. Unfortunately, the overall reported success of immune tolerance induction in FIX deficiency with inhibitors is approximately 25-40%.We report the case of a 2-year-old boy with hemophilia B severe FIX deficiency (<1%), inhibitor antibodies to FIX development, and a history of adverse reactions to FIX infusions, who underwent a successful desensitization and immune tolerance induction with a daily FIX infusion. With this regimen the inhibitor titer decreased with effective bleeding prevention.

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.).

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.

Factor IX and thrombosis

Fractionation technology has made Factor IX concentrates available. In addition to a very high incidence of hepatitis, thrombosis is being recognized as a consequence of their use. Contradictory reports exist in the literature as to the incidence of thrombotic events. A recent study of thrombohemorrhagic phenomena after infusion with Factor IX concentrates in patients with congenital Factor IX deficiency (hemophilia B) or liver disease, revealed an incidence of twenty episodes in 188 cases (11%). It is imperative to delineate the thrombogenic factors and find methods for their removal to insure the safety of Factor IX products.

Prothrombin complex concentrate (Beriplex P/N) for emergency anticoagulation reversal: a prospective multinational clinical trial

BACKGROUND

Prothrombin complex concentrate (PCC) can substantially shorten the time needed to reverse antivitamin K oral anticoagulant therapy (OAT). OBJECTIVES. To determine the effectiveness and safety of emergency OAT reversal by a balanced pasteurized nanofiltered PCC (Beriplex P/N) containing coagulation factors II, VII, IX, and X, and anticoagulant proteins C and S.

PATIENTS AND METHODS

Patients receiving OAT were eligible for this prospective multinational study if their International Normalized Ratio (INR) exceeded 2 and they required either an emergency surgical or urgent invasive diagnostic intervention or INR normalization due to acute bleeding. Stratified 25, 35, or 50 IU kg(-1) PCC doses were infused based on initial INR. Study endpoints included INR normalization (

RESULTS

Forty-three patients, 26 requiring interventional procedures and 17 experiencing acute bleeding, received PCC infusions at a median rate of 7.5 mL min(-1) (188 IU min(-1)). At 30 min thereafter, INR declined to

CONCLUSIONS

PCC treatment serves as an effective rapid hemorrhage control resource in the emergency anticoagulant reversal setting. More widespread availability of PCC is warranted to ensure its benefits in appropriate patients.

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Key Words Collapse

MESH Headings

• Adult
• Aged
• Aged, 80 and over
• Anticoagulants/adverse effects
• Coumarins/adverse effects
• Drug Combinations
• Emergencies
• Europe/epidemiology
• Factor IX/adverse effects
• Factor IX/therapeutic use
• Factor VII/adverse effects
• Factor VII/therapeutic use
• Factor X/adverse effects
• Factor X/therapeutic use
• Female
• Hemorrhage/chemically induced
• Hemorrhage/drug therapy
• Hemorrhage/prevention & control
• Hemostatics/adverse effects
• Hemostatics/therapeutic use
• Humans
• International Normalized Ratio
• Israel/epidemiology
• Male
• Middle Aged
• Prospective Studies
• Prothrombin/adverse effects
• Prothrombin/therapeutic use
• Pulmonary Embolism/chemically induced
• Vitamin K/therapeutic use

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Grants Collapse

Affiliation(s)

I Pabinger Department of Internal Medicine, Division of Haematology and Haemostaseology, Medical University Vienna, Vienna, Austria
B Brenner
U Kalina
S Knaub
A Nagy
H Ostermann

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Achievement of immune tolerance in a patient with haemophilia B and inhibitory antibodies, complicated by an anaphylactoid reaction

We describe a young boy with severe haemophilia B who developed inhibitory antibodies and an anaphylactoid reaction to factor IX. Immune tolerance was achieved by desensitisation with escalating doses of factor IX followed by the Malmö regimen.

Molecular epidemiologic study of a human immunodeficiency virus 1 outbreak in haemophiliacs B infected through clotting factor 9 after 1990

BACKGROUND AND OBJECTIVES

Twenty haemophiliacs were diagnosed as infected with human immunodeficiency virus 1 (HIV-1), 1 to 2 years after exposure to clotting factor 9 manufactured in Korea, beginning in early 1990. This study assessed the genetic relationships between viruses found in plasma donors and haemophiliacs.

MATERIALS AND METHODS

Sequencing of the nef and pol genes of viruses from infected haemophiliacs, plasma donors whose plasma was used in domestic clotting factor manufacture, haemophiliacs infected outside Korea, and local controls were determined by nested polymerase chain reactions and direct DNA sequencing. Phylogenetic analysis was used to investigate the relationships among the sequences.

RESULTS

Both plasma donors and the haemophiliacs were infected with a subclade of subtype B that is a founder effect lineage in Korea.

CONCLUSION

Our data indicate that HIV-1 transmission to 20 haemophiliacs occurred through intravenous injection of Korean-made clotting factor.

SUMMARY

A clotting factor made in Korea from blood from cash-paid donors infected at least 20 haemophiliacs with HIV-1 subtype B.

Blood safety and the choice of anti-hemophilic factor concentrate

Hemophilia is a congenital disorder due to the deficiency of the activity of factor VIII (classical hemophilia A) or IX (Christmas disease or hemophilia B). Bleeding is common and may result in long-term complications or even death. Bleeding may be treated or prevented by infusion of factor concentrates however these drugs are not without risk. Clinicians often feel ill prepared to provide accurate and impartial information regarding these drugs. This review will provide the reader with an historical yet up to date perspective on blood safety as it relates to the choice of concentrates to treat hemophilia.

Differences between patients', physicians' and pharmacists' preferences for treatment products in haemophilia: a discrete choice experiment

The provision of health care to patients with haemophilia through replacement of the deficient coagulation factor is the result of a complex interaction between patients, physicians and policy makers, each carrying their individual sets of preferences. Preferences of patients, physicians and pharmacists towards perceived viral safety, risk of inhibitor development, infusion frequency during prophylaxis, pharmaceutical dosage form, distribution modes and price were evaluated by conjoint analysis, using a discrete choice experiment. Overall 178 patients', 69 physicians and 58 pharmacists completed the study. Patients, physicians and pharmacists displayed preferences: (i) similar in direction and strength for risk of inhibitors and frequency of prophylaxis, (ii) similar in direction, but not in strength for perceived viral safety and price, with patients showing lower strength compared with physicians and pharmacists, and (iii) dissimilar in direction and/or strength for: (i) dosage form, which tested important only for pharmacists and (ii) distribution mode, which tested important for patients and physicians only. Our study provides evidence of the differences between different stakeholders in the preferences towards haemophilia replacement therapy, indicating that different opinions should be taken into account when planning optimal care.

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.

Hemophilia gene transfer: comparison with conventional protein replacement therapy

One of the unanswered questions in hemophilia is whether gene transfer, if successful, will be a safe and effective alternative to standard clotting factor treatment for hemophilia. Despite life-threatening complications of protein-based clotting factor treatment during the last three decades, including acquired immunodeficiency syndrome and hepatitis C, factor infusion is now considered safe, effective, and compatible with a normal lifespan. Thus, protein-based therapy will be the standard against which the safety and efficacy of gene transfer will be judged. Will the potential risks of gene transfer be sufficiently low to justify its use? Should all individuals with hemophilia consider gene transfer? To answer these questions, the known risks and benefits of current protein-based therapy must be compared with the potential risks and benefits of gene transfer. It is anticipated that risks of gene transfer may include the known risks of protein-based therapies, including allergic reactions, inflammatory responses, inhibitor formation, chronic hepatitis, as well as gene-transfer-specific risks, including germline transmission, insertional mutagenesis, thrombosis, and potential ethical and psychological issues. This article reviews and compares the risks and benefits of standard protein-based therapy with those of gene transfer, and considers how gene transfer might fit into state-of-the-art management of hemophilia.

Clinical Gene Transfer Studies for Hemophilia B

Hemophilia B, a deficiency of functional factor IX (FIX), has been extensively explored as a model for gene transfer. Two U.S. Food and Drug Administration-approved clinical studies for hemophilia B have been undertaken, both using adeno-associated viral vectors (AAV). AAV vectors have tropism for liver, muscle, central nervous system, and the respiratory tract; both skeletal muscle and liver have been used as target tissues in the hemophilia B studies. In both studies, proof of principle was first established in the hemophilia B dog model, with long-term expression of canine FIX at therapeutic levels achieved before clinical studies were initiated. In the AAV-FIX muscle trial, vector was introduced into skeletal muscle of the upper and lower extremities of eight human patients by direct intramuscular injection. Muscle biopsies taken 2 to 10 months postinjection demonstrated gene transfer and expression (by Southern blot and immunofluorescence, respectively) in all patients, but circulating FIX levels were generally not >1%, and escalation of dose to levels that proved therapeutic in animals was thwarted by feasibility issues regarding the number of injections required. Nevertheless, the study demonstrated that parenteral injection of AAV-FIX was safe at the doses tested, and could result in long-term expression of the transgene. Moreover, the general characteristics of transduction of human muscle were similar to those observed in other animal models. The safety and efficacy data established in the first trial formed the basis for a second trial in which AAV-FIX is administered systemically to target the liver. The liver study is currently ongoing, with six patients enrolled to date.

A retrospective survey on the safety of Replenine®, a high-purity factor IX concentrate

PURPOSE

To assess the safety of a plasma-derived highly purified factor IX concentrate (Replenine) in routine clinical use.

METHODS

Following guidelines entitled Safety Assessment of Marketed Medicines (SAMM), safety data were collected in the UK by retrospective review of the hospital notes of 114 patients who received an estimated 14.8 million IU of Replenine. Included were 40 patients undergoing 44 surgical procedures or dental extractions [corrected].

RESULTS

The study detected a total of nine adverse events (AEs), four of which were possibly product-related, four that were unrelated to the product and one whose causality was unknown. None of these cases had been notified to the manufacturer through conventional spontaneous reporting procedures. One patient was switched from Replenine because of infusion site irritation, but no unexpected adverse reactions were noted. There were no reports of virus transmission or new factor IX inhibitor development. The mean factor IX recovery value was 1.44 IU/dl per IU/kg (95%CI: 1.31-1.57 IU/dl per IU/kg).

CONCLUSIONS

The study was a practical application of the SAMM guidelines to the collection of pharmacovigilance data on patients with Haemophilia B. Replenine is well tolerated in routine clinical practice.

Successful induction of immune tolerance in a patient with haemophilia B with inhibitor

We describe successful induction of immune tolerance (IT) in a 10-month-old boy with severe haemophilia B. Urticaria developed soon after starting prophylactic treatment and was associated with an inhibitor at 7 Bethesda units mL(-1). Initially, we tried low dose factor IX therapy to induce IT with only a transient effect. The patient experienced an intracranial haemorrhage. A simple bolus dose of FIX eradicated the inhibitor. Thereafter he has been free from inhibitor and nephrotic syndrome for more than 5 years, although he receives FIX three times a week.

Management of haemophilia B inhibitor patients with anaphylactic reactions to FIX concentrates

Allergic reactions to concentrates containing factor IX (FIX) are serious complications in the treatment of haemophilia B patients with inhibitor. We have established a therapeutic protocol for such cases using an initial skin test followed by step-wise infusions of FIX concentrates under hydrocortisone cover. We have successfully treated three patients whose treatment with FIX had been suspended.

Continuous intravenous infusion of a plasma-derived factor IX concentrate (Mononine) in haemophilia B

This prospective, multicentre, open-label study evaluated the efficacy and safety of a plasma-derived factor IX concentrate [Mononine, Coagulation Factor IX (Human) Monoclonal Antibody Purified] administered by continuous intravenous (CIV) infusion to patients with haemophilia B. Admission criteria included documented diagnosis of haemophilia B (mild, moderate, or severe). Twenty-eight patients (25 surgery, two trauma, one severe spontaneous haemorrhage) were enrolled to receive a therapeutic bolus dose followed by CIV infusion of factor IX (FIX) to maintain FIX:C plasma levels of 0.4-1.0 IU mL(-1) (i.e. 40-100%). A median intravenous bolus dose of 54.2 IU kg(-1) FIX was administered to a subset of 13 non-emergency patients 7-21 days prior to CIV infusion to determine pharmacokinetic parameters in order to guide the dosing for CIV. For treatment, a bolus injection (median FIX dose; 89.6 IU kg(-1)) (range, 12.4-108.3), followed by a median total CIV infusion dose of 396.4 IU kg(-1) (range, 44.9-785.5) was administered at a median rate of 3.84 IU kg(-1) h(-1) (range, 1.74-7.33) for 107.17 h (range, 31.75-144). Twenty-four patients completed 72-120 h of FIX CIV infusion. Overall, 'excellent' (i.e. achievement of normal haemostasis) efficacy was reported in 23 of 24 (96%) evaluable patients, and 'good' (i.e. slight oozing) efficacy was reported in one (4%) patient. Median FIX:C was 72-86% for all patients receiving FIX by CIV on all days. Nine patients reported 13 adverse events that were possibly related to study medication but were not deemed serious by the investigator and were mainly because of local irritation at the infusion site. FIX CIV infusion therapy is safe and effective in the treatment of haemophilia B patients undergoing surgery, exposed to trauma, or experiencing severe spontaneous haemorrhage.

Safety of the new generation recombinant factor concentrates

Haemophilia A and B are X-linked disorders resulting from deficiency of Factor VIII and IX, respectively. Clinical sequellae of Factor VIII or IX deficiency include spontaneous and traumatic haemorrhages into joints, soft tissues, and muscles. The cornerstone of therapy has been replacement of the deficient factor, historically with pooled-plasma derivatives. The unfortunate blood-borne infection transmission (such as HIV, hepatitis B and C viruses), inhibitor formation, immunosuppression, and, in certain cases, thrombosis by these products has spawned major advances and innovations in the manufacture of clotting products. Recombinant technology has virtually eliminated transmissible disease risk; yet, the presence of albumin in second and third generation recombinant products raises, at the least, theoretical risk of prions and parvovirus B19. Other non-infectious complications, including inhibitor formation, allergic reactions, and thrombosis, remain formidable concerns. Despite this, recombinant factors remain the most attractive treatment approach for haemophilia. Future improvement awaits the development of safe and effective gene transfer technology.

Concentrate safety and efficacy

Safety from transmission of infections through plasma-derived clotting factor concentrates is assured by improved donor screening, serological testing of individual donations and direct viral testing of small plasma pools. Modern viral-inactivation techniques are highly effective. Recombinant concentrates stabilized in human albumin are being superaeded by those with other stabilizers. Recently reported discrepancies between estimates of concentrate potency from in vitro assays versus in vivo recovery, depending upon type of assay and reference standard used, are not fully resolved.

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.

Similar late revascularization rates 10 to 12 years after angioplasty or bypass surgery for multivessel coronary artery disease: a report from the Lady Davis Carmel Medical Center (LDCMC) Registry

We compared completed long-term outcome and late repeat revascularization rates in 272 consecutive patients with multivessel coronary disease who underwent revascularization (95 angioplasty cohort, 177 surgical cohort) between 1984 and 1986. Long-term survival was similar at 12 years in the angioplasty (70%) and surgical (74%) cohorts (p = NS), and repeat revascularization, although more frequent in the angioplasty patients during the first 5 years of follow-up, was performed equally in the 2 patient cohorts after 10 to 12 years of follow-up.

Venous thromboembolism after hip fracture surgery in a patient with haemophilia B and factor V Arg506Gln (factor V Leiden)

We describe a patient with mild haemophilia B who developed symptomatic venous thromboembolism after hip arthroplasty for a traumatic fracture. A deep vein thrombosis developed in the operated leg while he was receiving a high-purity factor IX concentrate. Subsequently, he was determined to be a heterozygous carrier for the factor V Arg506Gln (Leiden) mutation. This case illustrates the importance of providing thromboprophylaxis for all patients with haemophilia receiving coagulation factor replacement and who undergo surgical procedures known to be associated with a high risk of venous thromboembolism. In patients with haemophilia and a family history of venous thromboembolism, preoperative screening for the presence of the factor V Arg506Gln mutation and other thrombophilias may be useful.

Induction of immune tolerance and suppression of anaphylaxis in a child with haemophilia B by simple plasmapheresis and antigen exposure

Anaphylaxis to factor IX (FIX) in patients with haemophilia B is a rare and life-threatening complication that has been reported to occur in association with the development of inhibitors to FIX. Management of these patients is difficult. This report presents an 18-month-old boy with a frame-shift mutation of the FIX gene and FIX coagulant level of <1% who developed anaphylactoid reactions to low and high purity plasma-derived FIX concentration infusions and an inhibitor measuring 1.0 BU mL(-1). The patient was managed with simple plasmapheresis, a short course of corticosteroids and high-dose antigen exposure, which successfully induced long-lasting immune tolerance to FIX concentrates.

Possible association between cytomegalovirus infection and gastrointestinal bleeding in hemophiliac patients

Cytomegalovirus (CMV) infection is of major concern in immunocompromised and immunosuppressed patients. Prior to the introduction of HIV-1 antibody screening and efficient virucidal processes to inactivate viruses, individuals with a factor VIII or factor IX deficiency had a high risk of contracting HIV-1 infection through the infusion of contaminated blood products. In addition, blood products were also frequently associated with alterations in immune function. This study investigated the frequency of active CMV infection and its clinical relevance in Brazilian hemophiliacs. One hundred hemophiliacs were screened for the presence of CMV-DNA in their blood using nested PCR. Twenty-five out of 100 patients (25%) were positive for CMV-DNA and 24 of these 100 patients (24%) were HIV-1 positive; 6 of these 24 (25%) were positive for CMV-DNA. A similar frequency was observed among HIV-1-negative patients. In 60 hemophiliacs, the clinical relevance of the CMV infection was assessed. Twenty-one patients were positive for CMV-DNA. Of these, 10 had gastrointestinal bleeding compared to only 9 of 39 patients who were CMV-DNA negative (p = 0.05; chi(2) test). These data indicate a high prevalence of active CMV infection in Brazilian hemophiliac patients, irrespective of whether the patients were or were not infected by HIV-1. There was a possible association between the presence of CMV and the occurrence of gastrointestinal bleeding.

Coagulation products and their uses

The indications, pharmacokinetics, and therapeutic guidelines for available coagulation products are reviewed. Patients with hemophilia, von Willebrand's disease (VWD), or acquired inhibitors to antihemophilic factor (AHF) cannot spontaneously stop an acute hemorrhage. Coagulation products used to manage bleeding in patients with these disorders include AHF concentrates, factor IX concentrates, factor VIIa concentrate, factor IX complexes, anti-inhibitor coagulant complexes, and desmopressin acetate. Typically, these commercially available products are used to manage acute bleeding or to prevent excessive bleeding during surgery. The dosage of the coagulation products and the duration of therapy depend on many variables, including the severity of the hemorrhage, the pharmacokinetics of the coagulation products, and patient-specific factors. Product purity and viral attenuation are also important considerations in determining an appropriate dosage regimen. Recombinant versions of some coagulant factors are available and can eliminate the risk of viral transmission. A thorough understanding of each coagulation product can guide product selection, dosing, and treatment duration and can reduce the risk of viral transmission.

Incidence of factor IX inhibitor development in severe haemophilia B patients treated with only one brand of high purity plasma derived factor IX concentrate

Fifteen previously untreated patients (Pups) with severe haemophilia B (factor IX activity < or = 2 U/dl) only treated with one brand of plasma-derived high purity factor IX concentrate (FIX LFB) were studied. Age at first injection varied from 1 to 137 months and follow-up since this first injection from 21 to 86 months (median: 35). Cumulative exposure days (CED) were from 4 to over 100 (median: 26). Among these 15 Pups only one developed an inhibitor. Mutation analysis performed in all patients showed total gene deletion in the patient with inhibitor, partial gene deletion in another one, and missense mutations in 9 families. Mutation was not found in one patient. Actually, according to the data already published, only two patients were at high risk for inhibitor development in our population. Our study, although rather small, confirms the previously reported low incidence of inhibitors in haemophilia B. Large studies on incidence of FIX inhibitors are indeed difficult to perform, due to both the overall small number of severe haemophilia B patients and the low incidence of FIX inhibitors. Consequently, the impact of bias, such as prevalence of different types of gene defects in a given population, is major. Therefore, any study, dealing with incidence of FIX inhibitors in severe haemophilia B should report, for each patient, the type of gene defect.

Virus safety of prothrombin complex concentrates and factor IX concentrates

Substantial progress in virus safety has been achieved during the past 15 years. Therefore only a few virus transmissions with plasma-derived products have been observed since 1985. Specific steps to eliminate, remove, or inactivate viruses were developed. Although virus safety is of decisive importance, chemical or physical treatment during the manufacturing process need not activate labile coagulation factors that cause the risk of thrombogenicity nor need not create neoantigens that mediate the risk of inhibitor formation. Thus, any new virus elimination procedure has to be evaluated and validated for all safety aspects. A comprehensive framework of regulations and efforts has been set up involving plasma donors, donation centres, manufacturers, regulatory authorities, politicians responsible for legislation, physicians, and patients. Blood and plasma donation centres and pharmaceutic industry follow "Good Manufacturing Practice" and are subject to regular audits and official inspections. Every single donation as well as plasma pools are tested for virus markers. The final products need both a marketing authorization and official batch release; in Germany, supervised by the Paul-Ehrlich-Institute. European integration is the purpose of the European Medicines Evaluation Agency. An alert pharmacovigilance system enables scientifically adequate reactions in any case of a safety problem. The ultimate evidence of product safety is provided by clinical surveillance. By participating in clinical studies, patients themselves are able to contribute significantly to the safety of plasma-derived products. The currently achieved high level of safety should encourage us to take further steps to stabilize this success and to look for further progress, wherever possible.

Continuous infusion of FVIII and FIX concentrates: in vitro analysis of clinically relevant parameters

A high purity factor VIII/von Willebrand Factor (FVIII/vWF) concentrate (IMMUNATE [STIM plus]) (n = 6 batches), and a high purity factor IX (FIX) concentrate (IMMUNINE [STIM plus]) (n = 7 batches), were assessed in vitro for their applicability to continuous infusion. Parameters pertinent to continuous infusion were investigated and included stability, sterility and, in the case of FIX, the generation of potentially thrombogenic components. Four stationary or transportable mini infusion pumps, equipped with polyethylene, polypropylene or polyvinylchloride plastic components were used. The concentrates were reconstituted without extra filling volume and perfused at 12.5 mL h-1 and 1 mL h-1; sampling was carried out at the start of the experiment and for up to 48 h. The FVIII procoagulant activity (FVIII:C) was assayed by amidolytic, 1-stage and 2-stage assays; vWF was examined for ristocetin cofactor activity, antigen and multimers. The FIX coagulation activity (FIX:C) was determined by a 1-stage coagulation assay; thrombogenicity potential was assessed in vivo (Wessler stasis model in rabbits) and in vitro (FIXa and nonactivated thromboplastin time). Reconstituted concentrate incubated under the same conditions served as a control. Both concentrates remained sterile throughout the testing period. The perfused and control samples remained stable, retaining over 95% of activity for FVIII:C and over 90% for FIX:C for up to 48 h. Intermittent decrease of FVIII:C or FIX:C was not observed, suggesting no adsorption of FVIII or FIX onto plastic surfaces during either short or long-term exposure. No thrombogenic components were detected in the high purity FIX concentrate. Thus, under the in vitro conditions used, FVIII/vWF and FIX were found to be suitable for administration by continuous infusion.

Anaphylactoid reactions and nephrotic syndrome--a considerable risk during factor IX treatment in patients with haemophilia B and inhibitors: a report on the outcome in two brothers

Anaphylaxis/anaphylactoid reactions have recently been reported after few treatments with factor IX concentrates in patients with haemophilia B at the same time as inhibitors to factor IX were demonstrated. In some of these cases nephrotic syndrome has appeared during immune tolerance induction (ITI) with high doses of factor IX concentrates. Gene deletions seem to be associated with a high risk of developing antibodies to factor IX. This report presents two brothers with deletion of 1 bp in exon f of the factor IX gene. Both showed anaphylactoid reactions and they were desensitized using slow i.v. injections of factor IX. At the time of anaphylaxis, inhibitors of factor IX in a low titre could be demonstrated. The elder brother responded well after a short time on ITI and has no spontaneous bleedings on regular prophylaxis although in a somewhat higher dose than expected. On the other hand, in spite of comparable regimens, the younger brother has so far been resistant to ITI. Moreover, during treatment with extremely high doses of factor IX concentrate he developed nephrotic syndrome which only slowly subsided after treatment with corticosteroids and withdrawal of factor IX.

Membranous glomerulonephritis and nephrosis post factor IX infusions in hemophilia B

Children with hemophilia B who receive exogenous factor IX infusions may rarely develop inhibitors to the exogenous factor IX and require desensitization. Nephrotic syndrome has recently been described in some of these children. We report the renal clinicopathological findings in a child with severe factor IX deficiency, requiring induction of an immune tolerance protocol, who developed nephrotic syndrome. Renal biopsy revealed peripheral capillary wall thickening and a spike appearance consistent with membranous glomerulonephritis. Electron microscopy showed prominent deposits throughout the thickness of the basement membrane. Factor IX dose reduction was accompanied by reversal of the child's nephrotic syndrome without relapses.