Factor VIII recovery after a single infusion of recalibrated ReFacto® in 14 severe haemophilia A patients

A recent multicentre collaborative study showed higher estimates of ReFacto potency when assayed with ReFacto Laboratory Standard(TM) (RLS) in comparison when standards consisting of full-length factor VIII (FVIII) were used. The RLS was hence recalibrated, leading to a 20% increase in the amount of ReFacto per vial without change in the labelled potency. The primary objective of this study was to determine the incremental and in vivo recovery of the recalibrated ReFacto in patients with severe haemophilia A. Fourteen male severe haemophilia A patients (FVIII < 1 IU dL(-1)) with a cumulative previous exposure days to any FVIII product >150 were administered an intravenous infusion 50 +/- 5 IU kg(-1) of ReFacto over a 5-min period. Blood samples were collected before infusion and after 15, 30 and 60 min. FVIII clotting activity (FVIII:C) was assessed in a central laboratory by the chromogenic substrate assay. After ReFacto infusion, peak FVIII:C was obtained within 15 min for 10 patients and within 30 min for the remaining four. Mean FVIII:C at peak was 117.7 +/- 17.3 IU dL(-1). Mean incremental recovery was 2.22 +/- 0.27 IU dL(-1) per IU kg(-1) while mean in vivo recovery was 105.9 +/- 14.6%. One patient reported three mild adverse events rated as 'unrelated' to the study drug. FVIII recovery after recalibrated ReFacto infusion falls within the expected range and is similar to the values reported for other FVIII concentrates.     

In vitro evaluation of B-domain deleted recombinant factor VIII (ReFacto®) stability during simulated continuous infusion administration

The administration of factor VIII (FVIII) by continuous infusion (CI) to manage severe haemorrhage or during major surgery appears pharmacokinetically and economically favourable when compared with intermittent bolus infusions. Successful clinical use of FVIII delivered by CI, however, requires a thorough assessment of product stability under conditions encountered during CI such as prolonged exposure to the delivery devices at ambient temperature and the low FVIII concentrations. This investigation has identified conditions under which ReFacto, a recombinant human B-domain deleted FVIII, can be successfully delivered under dilute conditions when using large volume parenteral polyvinyl chloride (PVC) bags without the addition of stabilizers or as an undiluted preparation delivered by ambulatory infusion pumps. ReFacto is stable for 36 h when stored in large volume parenteral PVC reservoirs at 3 and 8 IU mL(-1) or 72 h when delivered undiluted at 62 IU mL(-1) by CADD infusion pumps. The greatest concern with the delivery of ReFacto by CI is adsorptive losses to the contact surfaces of the delivery system. There was no significant binding of ReFacto to the PVC reservoirs overtime; however, there was appreciable binding to the administration set under certain conditions. The binding was influenced by the ionic strength of the solution, residence time in the tubing and protein concentration. The recovery and stability profile of ReFacto under certain conditions appears favourable when compared with that of full-length recombinant FVIII products, observed by other investigators.     

Continuous infusion of B-domain deleted recombinant factor VIII (ReFacto) in patients with haemophilia A undergoing surgery: clinical experience

This retrospective, open-label, non-comparative study evaluated continuous infusion of recombinant factor VIII (ReFacto), B-domain deleted recombinant FVIII (BDDrFVIII), in patients with haemophilia A undergoing surgery and requiring >5 consecutive days of treatment. Sixteen patients from eight centres underwent a total of 20 procedures. Haemostatic outcome was assessed as 'excellent' or 'good' in 75% of procedures, and target FVIII:C levels were maintained throughout the continuous infusion period. The reported volume of blood loss during surgery was also within the normal range for non-haemophilic patients for the type of surgery performed. Red blood cell transfusions were required to balance excessive blood loss during BDDrFVIII continuous infusion in eight (40%) procedures (seven patients), five with bleeding or requiring volume replacement and three to treat anaemia secondary to blood loss. Non-serious adverse events considered by investigators as possibly or probably related to BDDrFVIII continuous infusion were infrequent (n = 5) considering the duration of treatment (n =239 cumulative days of continuous infusion), and all of these were mild-to-moderate in severity. No thromboembolic complications were reported except for one case of thrombophlebitis occurring at the infusion site. Only two patients (four events) experienced serious adverse bleeding; BDDrFVIII was otherwise well-tolerated. These data show that continuous infusion of BDDrFVIII provides reliable haemostasis and is an effective and well-tolerated regimen for patients with haemophilia A undergoing surgery.     

The safety and efficacy of B-domain deleted recombinant factor VIII concentrate in patients with severe haemophilia A

BACKGROUND: B-domain-deleted recombinant factor VIII (BDDrFVIII) was developed when the B-domain was found to be redundant for maintaining haemostasis. This allows formulation of the final product without albumin added as a stabilizer. METHODS: Three multicentre clinical studies and one pharmacokinetic study were conducted in 218 patients to evaluate the safety and haemostatic efficacy of BDDrFVIII. RESULTS: Previously treated patients (n = 113; median duration, 1711 days; median exposure days, 385; total 98,096,287 IU infused) rated 97-99% of all infusions as good or excellent efficacy. FVIII inhibitor was noted in one patient in the previously treated patient cohort after 113 exposure days. Among 101 previously untreated patients, responses to BDDrFVIII were rated as excellent or good in 92-95% of infusions (median duration, 1413 days; median exposure days, 148; total 12,636,458 IU infused). Thirty-two previously untreated patients developed inhibitors after a median duration of 12 exposure days (range, 3-49). Sixteen of 32 (50%) patients had low levels (< or = 5 Bethesda units) and 16 had high levels of inhibitors. Inhibitors disappeared in six of 14 (43%) of the high-level and six of eight (75%) of the low-level patients who underwent immune tolerance induction therapy. A total of 42 patients underwent surgery and the overall efficacy of BDDrFVIII was rated as excellent or good for 99.6% of infusions. CONCLUSIONS: The results of these clinical studies indicate that BBDrFVIII is safe and effective and has haemostatic activity similar to that of full-length FVIII concentrates.     

Practical and cost‐effective measurement of B‐domain deleted and full‐length recombinant FVIII in the routine haemostasis laboratory

The assessment of recombinant FVIII (rFVIII) activity (FVIII:C) in plasma of patients is dependent on the assay. Notably, a calibration with a product‐specific laboratory standard is recommended when measuring Refacto‐AF^R activity in plasma with a one‐stage assay. The objective of this study was to facilitate the measurement of rFVIII, taking into account the recent demonstration that a calibration curve does not have to be included in each run. FVIII:C was measured in patients' samples after infusion of different types of rFVIII with a one‐stage and a chromogenic assay calibrated either with pooled normal plasma or a product‐specific laboratory standard. Results obtained with the one‐stage coagulation assay were compared with these provided by a chromogenic assay. We confirmed that a calibration curve can be used for a prolonged period of time without loss of precision and accuracy. In such conditions, a stable relation between the calibration curves generated with a product‐specific laboratory standard and plasma can be established. In patients' plasma, Refacto‐AF levels measured with a one‐stage FVIII assay calibrated with plasma or a product‐specific laboratory standard diverged from ?58% to ?17% and from ?25% to +18%, respectively, from the activity determined with a chromogenic substrate assay. By comparison, FVIII:C levels of full‐length rFVIII measured with the one‐stage assay calibrated with plasma were 6–49% lower than with the chromogenic assay. In a monocentric setting, the long‐term stability of the calibration curves allows the implementation of a practical and cost‐effective approach to determine rFVIII:C levels.     

Pharmacokinetics of recombinant factor VIII (Kogenate-FS®) in children and causes of inter-patient pharmacokinetic variability

Summary.  Understanding the pharmacokinetics (PK) of factor VIII (FVIII) is important in the management of patients with haemophilia A. We studied the PK of FVIII in order to determine aetiological factors contributing to PK variability of FVIII in children.
Twenty children with haemophilia A (mean age 12.8 years) were administered a single bolus of 50 U kg⁻¹ of recombinant FVIII (rFVIII; Kogenate-FS^®, Bayer).
The mean incremental FVIII recovery was 1.87 (U mL⁻¹)/(U kg⁻¹) (range: 1.25–2.76) and the mean FVIII half-life was 10.7 h (range: 7.8–15.3). FVIII recovery was positively correlated with body surface area (BSA; P  = 0.04). FVIII half-life was positively correlated with preinfusion levels of von Willebrand factor antigen (VWF:Ag) ( P  = 0.0001) and was reduced in patients ( n  = 6) with very low FVIII inhibitor titres (<0.5 BU) vs. those ( n  = 14) with negative inhibitor titres ( P  = 0.06).
These observations suggest that (i) young children with haemophilia in comparison with adults have a low recovery of FVIII and that this might be explained by differences in body composition (BSA, plasma volume), (ii) levels of VWF:Ag may explain some of the differences in the half-life and clearance of FVIII and (iii) very low inhibitor titres, previously regarded as clinically insignificant, may actually be significant and should be evaluated in the context of PK studies.     

Recombinant factor IX (BeneFix®) by adjusted continuous infusion: a study of stability, sterility and clinical experience

The safety and efficacy of adjusted continuous infusion (CI) of recombinant factor IX (FIX; BeneFix) was assessed in vitro and in a clinical study. BeneFix was reconstituted at 100 IU mL-1 with or without unfractionated heparin (4 U mL-1) and stored at either 4 degrees C or room temperature. Reconstituted BeneFix retained at least 90% activity over 14 days if stored at 4 degrees C but stability was reduced at room temperature. BeneFix reconstituted in a sterile pharmacy was free of bacterial contamination. Six patients with haemophilia B received seven CIs of BeneFix to cover routine surgery and severe bleeding episodes. The CIs lasted between 3 and 10 days. In all cases, haemostasis was excellent and the desired therapeutic FIX level was easily maintained. No thrombotic episodes or inhibitor development occurred but two patients developed thrombophlebitis at the infusion site when heparin was not added to the infusion. BeneFix is not currently licensed for CI and we suggest that studies to enable licensing should be established as soon as possible.     

Evaluation of recombinant factor VIII (Kogenate®) stability for continuous infusion using a minipump infusion device

Continuous infusion of recombinant factor VIII (rFVIII) is desirable in clinical settings in order to maintain haemostatic levels in a cost-effective manner. This study was designed to determine rFVIII stability over time using a minipump set-up, which has been employed by clinicians for continuous infusion of rFVIII. Vials from three lots of Kogenate (Bayer Corporation) were reconstituted in sterile water for injection, pooled and transferred to minipump infusion sets composed of either polyvinylchloride (Medex # IPR86/tube volume 0.5 mL) or polyethylene (McGraw S5904-52, tube and adapter volume 2.1 mL), and held in temperature-controlled rooms at 5 degrees C, 25 degrees C and 30 degrees C. Additional bags of rFVII were prepared with heparin (4 U mL-1), and maintained at 30 degrees C. rFVIII was infused at a rate of 1.0 mL h-1. Samples were analysed for rFVIII activity over a 7-day period at 0, 1, 15, 24, 78 and 168 h. Prior to the start of the timed study, rFVIII activity was measured in the lot pools and in the polyvinylchloride or polyethylene bags, and in the first flush volumes through the tubing. There was no difference in rFVIII activity measured in the pools compared to the bags. rFVIII levels in the initial 3-mL infusion through the tubing showed a slight decrease in activity compared to the initial level which amounted to an insignificant loss of activity for the polyvinylchloride tubing but a significant loss in the polyethylene tubing (approximately 10 IU absolute loss in polyvinylchloride vs. 100 IU loss in polyethylene). After an initial flush of 1.0 mL for polyvinylchloride and 5.0 mL for polyethylene, activity returned to baseline and subsequently remained stable for all time points and temperatures from 5-30 degrees C over the 7-day period. We conclude that the standard polyvinylchloride in polyethylene minipump bags and tubing provide excellent delivery and stability of rFVIII for continuous infusion with or without heparin, and can be used in hospital and ambulatory settings.     

Effective and safe use of recombinant factor VIIa (NovoSeven®) in elderly mild haemophilia A patients with high-titre antibodies against factor VIII

Three patients with mild haemophilia A who developed high-titre antibodies against factor VIII at high age are reported. These patients had only a limited number of exposure days of FVIII concentrates in the past. The patients had to undergo surgery or presented with recurrent bleeding episodes. Treatment with recombinant FVIIa (rFVIIa) was effective and safe. Despite the high age and the presence of coronary heart disease in one of the patients, no adverse events or thrombotic complications occurred. These cases illustrate that the physician should always be alert on the development of inhibitors, also in elderly patients with mild haemophilia, in whom FVIII inhibitors had never been detectable before and that treatment with rFVIIa was effective and well-tolerated.     

Cost–utility analysis of recombinant factor VIIa (NovoSeven®) in six children with long-standing inhibitors to factor VIII or IX

The high cost of treating patients with inhibitors in an environment of restricted budgets warrants consideration of cost-effectiveness. We determined the clinical response, effect on quality of life and the cost-effectiveness of treatment with rFVIIa in six boys with long-standing inhibitors to factors VIII or IX, compared with other treatment regimes previously used in these patients. The study used a longitudinal before-and-after design and was conducted in three phases. Phase 1 was 6 months preceding the introduction of rFVIIa, during which patients received on-demand 'usual care' with other treatment regimes; phase 2 was 6 months treatment on rFVIIa assessed retrospectively; and phase 3 was 6 months on rfVIIa treatment assessed prospectively. Treatment with rFVIIa was reserved for intrarticular, compartment, psoas, mucosal and suspected intracranial bleeding. Treatment outcomes were obtained by interview using structured questionnaires, the quality-of-life instruments CHQ CF-80 and CHQ PF-50, patient self-reporting diary, interrogation of hospital records, and the EuroQoL EQ-5D for utility valuations. Our results confirm that rFVIIa is clinically effective and resulted in 63-92% reductions in the number of re-treatments, duration of painful episodes, delay to initiation of treatment, days requiring wheelchair or crutches, emergency room visits and lost carer time compared with the patients' other therapies. Quality-of-life improvements were observed in several important areas as perceived by both patients and their families, at an incremental cost per QALY of A$51 533.     

Experience with a third generation recombinant factor VIII concentrate (Advate®) for immune tolerance induction in patients with haemophilia A

Summary.  The development of an inhibitor represents one of the most challenging complications in patients with haemophilia A. Optimal management is immune tolerance induction (ITI), typically through the administration of high doses of factor VIII (FVIII) concentrate. Among 12 patients who underwent ITI using Advate, a third-generation recombinant FVIII product that is free of animal and human protein additives, tolerance was achieved in nine (75%), including seven of 10 patients (70%) with high-titre inhibitors. ITI is ongoing in two patients and not yet successful; immune tolerance failed in the third patient. The median time to success was 4.0 months for group as a whole and for patients with high-titre inhibitors. Treatment was well tolerated, and no adverse events were observed. Advate was found to be equivalent to other FVIII products with regard to both ITI success rates and the incidence of adverse effects when used in these immune tolerance regimens.     

Inhibitor development in patients receiving recombinant factor VIII (Recombinate rAHF/Bioclate®): a prospective pharmacovigilance study

Clinical trials to date have not been adequately powered to assess comparatively infrequent events such as inhibitor development in previously treated patients (PTPs). Comprehensive large-scale pharmacovigilance studies can be useful for this purpose. We prospectively collected inhibitor development reports worldwide among recipients of Recombinate rAHF recombinant factor VIII (rFVIII), also formerly distributed under the product name Bioclate, for the entire postlicensure period from 1993 through 2002. To determine level of exposure to rFVIII we also compiled the Recombinate rAHF/Bioclate International Units (IU) distributed annually. To estimate inhibitor incidence separately for previously untreated or minimally treated patients (PUPs) with 1-50 exposure days and PTPs with >50 exposure days, we used haemophilia A incidence and prevalence data and pooled mean annual rFVIII consumption per PUP and PTP from international multicentre prospective clinical trials. Documented inhibitor cases totalled 89, and the total quantity of Recombinate rAHF/Bioclate rFVIII distributed was 6.48 x10(9) IU. No lot association or other clustering of inhibitor events was evident in PTPs. The incidence of all reported inhibitors, expressed as a percentage of patients treated, was 11.9% (CI: 5.05-28.0%) for PUPs when compared with 0.123% (CI: 0.030-0.512%) for PTPs. The rates for high-titre inhibitors (>5 BU) only were 5.96% (CI: 3.00-11.8%) for PUPs and 0.0554% (CI: 0.0113-0.271%) for PTPs. Thus, incidence rates for both all inhibitors and high-titre inhibitors in PTPs were 1% of the corresponding rates in PUPs. Data from prospective PUP clinical trials involving intensive active monitoring suggest that true inhibitor incidence may be approximately twice that estimated in this pharmacovigilance study. Nevertheless, inhibitor development in PTPs receiving Recombinate rAHF/Bioclate is infrequent.     

The use of the new ReFacto AF Laboratory Standard allows reliable measurement of FVIII:C levels in ReFacto AF mock plasma samples by a one‐stage clotting assay

Summary. Factor VIII coagulant (FVIII:C) levels measured in patients receiving ReFacto^® (B‐domain‐deleted recombinant FVIII) using chromogenic substrate assay (CSA) and one‐stage clotting assay (OSA) have frequently shown discrepancies, and the use of the ReFacto Laboratory Standard (RLS) has therefore been recommended to minimize these differences. The potency of ReFacto AF^®, the albumin‐free successor of ReFacto^®, is determined using CSA for the titration of vials, and a new standard (RLS‐AF) was developed to measure its biological efficacy using OSA. This multicentre study therefore evaluated the efficacy of this new RLS in minimizing differences between OSA and CSA when measuring FVIII:C levels in plasma. Mock plasma samples were prepared by diluting ReFacto AF^® in FVIII‐deficient plasma to obtain four concentrations ranging from 15 to 90 IU dL^?1. FVIII:C levels were then measured in six laboratories on four separate days using three different procedures, i.e. OSA with a plasma standard (PS) as reference, OSA with RLS‐AF and CSA with PS. The inter‐centre standard deviation ranged from 1.4 to 5.5 IU dL^?1. However, FVIII:C levels measured with OSA were closer to the expected values when RLS‐AF was used. In addition, the uncertainty of measurement, reflecting the inter‐method discrepancy was greatly reduced when RLS‐AF was employed in OSA (15%) in place of PS (33%). This study demonstrates that the OSA performed with RLS‐AF to establish calibration curves provides a valuable alternative to CSA to measure FVIII:C in ReFacto‐AF‐treated patients.     

Pharmacokinetics of activated recombinant coagulation factor VII (NovoSeven®) in children vs. adults with haemophilia A

To establish the pharmacokinetic profile of activated recombinant coagulation factor VII (rFVIIa; NovoSeven in children with haemophilia A, and to compare it with the pharmacokinetic profile in adults with haemophilia A. Twelve children (2-12 years) received one single dose of rFVIIa 90 and 180 micrograms kg(-1) in randomized order separated by a washout period of 48 h to 1 month. Six adults (18-55 years) received a single dose of rFVIIa 90 micrograms kg(-1). The pharmacokinetic analyses were based on a non-compartmental method. In children, the plasma level of FVII increased proportionally with the dose. The total body clearance normalized for body weight was significantly faster in children than in adults (FVII:C, 58 vs. 39 mL kg(-1) h(-1) and FVIIa, 78 vs. 53 mL kg(-1) h(-1), P < 0.05). A trend towards a larger volume of distribution at steady-state in children than in adults was observed (P > 0.05). Dose proportionality was established for plasma concentrations of FVII in children with haemophilia A at the dose levels investigated (90 and 180 micrograms kg(-1) rFVIIa). Following administration of rFVIIa 90 micrograms kg(-1), significantly faster clearance was observed in children compared with adults, suggesting that higher doses of rFVIIa may be needed to achieve the same plasma levels as in adults.     

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.     

Prevalence of IgG antibodies to human parvovirus B19 in haemophilia children treated with recombinant factor (F)VIII only or with at least one plasma-derived FVIII or FIX concentrate: results from the French haemophilia cohort

Human parvovirus B19 (B19) has been transmitted by some brands of virally attenuated plasma-derived factor VIII (FVIII) or IX (FIX) concentrates. To quantify the differences of human parvovirus B19 risk transmission between albumin-stabilized recombinant factor and plasma-derived factor, we studied the prevalence of IgG antibodies to B19 (anti-B19) in 193 haemophiliac children between 1 and 6-years of age who had previously been treated with albumin-stabilized recombinant FVIII only (n = 104), and in children previously treated with solvent/detergent high-purity non-immunopurified and non-nanofiltered FVIII or IX concentrates (n = 89). Association between the prevalence of anti-B19 and the treatment group was analysed using multivariate logistic regression. Age, severity and type of haemophilia, number of cumulative days of exposure to factor VIII or IX, previous history of red blood cells or plasma transfusion were considered as potential confounding variables. A higher prevalence of anti-B19 was found in children previously treated with solvent/detergent high-purity non-immunopurified and non-nanofiltered FVIII or IX concentrates than in children treated with albumin- stabilized recombinant FVIII only (OR: 22.3; CI: 7.9-62.8), independently of the other factors studied.     

Management of haemophilic patients with inhibitors in major orthopaedic surgery by immunadsorption, substitution of factor VIII and recombinant factor VIIa (NovoSeven®): a single centre experience

Inhibitors of factor VIII or FIX in haemophilic patients are a common and serious complication associated with an increased risk of life-threatening bleeding during elective surgery. Substitution therapy fails to be effective, therefore an alternative treatment is needed. We have performed six major elective orthopaedic interventions in four patients with haemophilia A and inhibitors. A preoperative immunadsorbant therapy with Therasorb to eliminate inhibitors was successful in four cases, but during FVIII substitution inhibitors increased on day 4 to day 6 after surgery, leading to decreasing FVIII levels. Therefore, therapy was changed to recombinant FVIIa (rFVIIa; NovoSeven). Two interventions had to be covered with sole rFVIIa therapy as immunadsorbant therapy failed to be effective in one case and the need for acute intervention did not allow pretreatment in the other. We did not see increased bleeding during or after surgery when compared to our experience with non-inhibitor haemophilic patients. In conclusion, a preoperative decrease of inhibitors from immunadsorbant therapy, perioperative substitution of FVIII and changing treatment to rFVIIa when inhibitors are increased, is a safe and economic therapy for guaranteeing haemostasis in major elective orthopaedic surgery. On the contrary, sole therapy with rFVIIa allows immediate surgical intervention without a long hospital stay prior to surgery and a need for laboratory monitoring of inhibitor titres and FVIII levels. Our findings support data previously published.