Production processes of licensed recombinant factor VIII preparations

The state-of-the-art treatment for hemophilia A is replacement therapy with recombinant factor VIII (rFVIII) made possible by genetic engineering advances. Currently, there are four different products licensed and available for hemophilia A patients. All are produced by recombinant mammalian cells in large-scale fermenter cultures, purified to high purity, formulated in stable formulations and freeze dried. The first-generation products Recombinate and Kogenate (also sold as Helixate by Aventis) are characterized as full-length human factor VIII molecules and formulated using human serum albumin as a stabilizer. The second-generation product ReFacto contains an improved albumin-free sucrose formulation and incorporates advanced antiviral safety procedures in the manufacturing process. It is a truncated B region-deleted form of factor VIII (FVIII) that makes use of a nonhuman peptide linker 14 amino acids in length to connect the 80 and 90 kD subunits. The most recently licensed rFVIII product is the second-generation Kogenate product called KOGENATE Bayer/Kogenate FS, which combines the advantages of the human full-length FVIII molecule with an albumin-free, sucrose-based synthetic formulation as well as an improved viral safety profile. In this article, the manufacturing processes for each of the four different products are discussed in detail, focusing on expression systems and cell lines, culture medium, technical culture systems, purification process (including viral removal potential), and final formulation.     

First and next generation native rFVIII in the treatment of hemophilia A. What has been achieved? Can patients be switched safely?

The introduction of plasma-derived human factor VIII (FVIII) and later human recombinant FVIII (rFVIII) has potentially allowed patients suffering from hemophilia A to have a quality of life and life expectancy similar to the population at large. One of the major achievements in molecular biology over the past 15 years was the sequencing of the gene coding for FVIII, leading eventually to the ability to isolate the human gene for FVIII and transfect cells to produce human rFVIII. The first rFVIII products, which are native full-length FVIII molecules, have proved to have an excellent efficacy and safety profile in patients with hemophilia A. Initial concerns about a potential increased inhibitor formation have not been confirmed so far but long-term pharmacovigilance of inhibitor formation is still ongoing. To date, no transmission of hepatitis or human immunodeficiency virus (HIV) attributable to rFVIII products has been reported. However, a theoretical risk of transmission of infectious disease does exist as long as nonsynthetic proteins are used during the production process. The next-generation native rFVIII has been developed to minimize the exposure of patients to animal or human plasma-derived proteins. This has been achieved through major changes to the process of production of rFVIII from baby hamster kidney cells (BHK). This change has included the introduction of a solvent/detergent step and, of more importance, the introduction of a purification procedure without using albumin as a stabilizer. Finally, the rFVIII (BHK) is formulated using sucrose as the final stabilizer to produce the sucrose formulated rFVIII referred to as rFVIII-FS. This article summarizes the recently published pharmacokinetic, safety, and efficacy data for the native rFVIII-FS and compares its clinical profile with that of the first-generation rFVIII.     

Bioengineering of coagulation factor VIII for improved secretion

Factor VIII (FVIII) functions as a cofactor within the intrinsic pathway of blood coagulation. Quantitative or qualitative deficiencies of FVIII result in the inherited bleeding disorder hemophilia A. Expression of FVIII (domain structure A1-A2-B-A3-C1-C2) in heterologous mammalian systems is 2 to 3 orders of magnitude less efficient compared with other proteins of similar size compromising recombinant FVIII production and gene therapy strategies. FVIII expression is limited by unstable mRNA, interaction with endoplasmic reticulum (ER) chaperones, and a requirement for facilitated ER to Golgi transport through interaction with the mannose-binding lectin LMAN1. Bioengineering strategies can overcome each of these limitations. B-domain-deleted (BDD)-FVIII yields higher mRNA levels, and targeted point mutations within the A1 domain reduce interaction with the ER chaperone immunoglobulin-binding protein. In order to increase ER to Golgi transport we engineered several asparagine-linked oligosaccharides within a short B-domain spacer within BDD-FVIII. A bioengineered FVIII incorporating all of these elements was secreted 15- to 25-fold more efficiently than full-length FVIII both in vitro and in vivo. FVIII bioengineered for improved secretion will significantly increase potential for success in gene therapy strategies for hemophilia A as well as improve recombinant FVIII production in cell culture manufacturing or transgenic animals.     

Safety and prolonged activity of recombinant factor VIII Fc fusion protein in hemophilia A patients

Current factor VIII (FVIII) products display a half-life (t(1/2)) of ～ 8-12 hours, requiring frequent intravenous injections for prophylaxis and treatment of patients with hemophilia A. rFVIIIFc is a recombinant fusion protein composed of a single molecule of FVIII covalently linked to the Fc domain of human IgG(1) to extend circulating rFVIII t(1/2). This first-in-human study in previously treated subjects with severe hemophilia A investigated safety and pharmacokinetics of rFVIIIFc. Sixteen subjects received a single dose of rFVIII at 25 or 65 IU/kg followed by an equal dose of rFVIIIFc. Most adverse events were unrelated to study drug. None of the study subjects developed anti-rFVIIIFc antibodies or inhibitors. Across dose levels, compared with rFVIII, rFVIIIFc showed 1.54- to 1.70-fold longer elimination t(1/2), 1.49- to 1.56-fold lower clearance, and 1.48- to 1.56-fold higher total systemic exposure. rFVIII and rFVIIIFc had comparable dose-dependent peak plasma concentrations and recoveries. Time to 1% FVIII activity above baseline was ～ 1.53- to 1.68-fold longer than rFVIII across dose levels. Each subject showed prolonged exposure to rFVIIIFc relative to rFVIII. Thus, rFVIIIFc may offer a viable therapeutic approach to achieve prolonged hemostatic protection and less frequent dosing in patients with hemophilia A. This trial was registered at www.clinicaltrials.gov as NCT01027377.     

Role of bone marrow transplantation for correcting hemophilia A in mice

To better understand cellular basis of hemophilia, cell types capable of producing FVIII need to be identified. We determined whether bone marrow (BM)-derived cells would produce cells capable of synthesizing and releasing FVIII by transplanting healthy mouse BM into hemophilia A mice. To track donor-derived cells, we used genetic reporters. Use of multiple coagulation assays demonstrated whether FVIII produced by discrete cell populations would correct hemophilia A. We found that animals receiving healthy BM cells survived bleeding challenge with correction of hemophilia, although donor BM-derived hepatocytes or endothelial cells were extremely rare, and these cells did not account for therapeutic benefits. By contrast, donor BM-derived mononuclear and mesenchymal stromal cells were more abundant and expressed FVIII mRNA as well as FVIII protein. Moreover, injection of healthy mouse Kupffer cells (liver macrophage/mononuclear cells), which predominantly originate from BM, or of healthy BM-derived mesenchymal stromal cells, protected hemophilia A mice from bleeding challenge with appearance of FVIII in blood. Therefore, BM transplantation corrected hemophilia A through donor-derived mononuclear cells and mesenchymal stromal cells. These insights into FVIII synthesis and production in alternative cell types will advance studies of pathophysiological mechanisms and therapeutic development in hemophilia A.     

Influence of the type of factor VIII concentrate on the incidence of factor VIII inhibitors in previously untreated patients with severe hemophilia A

Inhibitor development is the major treatment complication in children with severe hemophilia A. It is not clear whether the risk of inhibitors is higher with recombinant factor VIII or with plasma-derived factor VIII. We used multivariate analysis to compare 2 cohorts of previously untreated patients (PUPs) with severe hemophilia A: 62 patients treated with the same brand of high-purity plasma-derived FVIII (pFVIII) containing von Willebrand factor (VWF) and 86 patients treated with full-length recombinant FVIII (rFVIII). In addition to the usual end points (all inhibitors, high inhibitors), we also examined a third end point (high inhibitors and/or immune tolerance induction). The risk of inhibitor development was higher in patients treated with rFVIII than in patients treated with pFVIII, regardless of other risk factors (F8 genotype; nonwhite origin; history of inhibitors in patients with a family history of hemophilia; age at first FVIII infusion). The adjusted relative risk (RRa) for inhibitor development with rFVIII versus pFVIII was 2.4 (all inhibitors), 2.6 (high inhibitors), and 3.2 (high inhibitors and/or immune tolerance induction), respectively, depending on the end point (above). The pathophysiology of this large effect must be understood in order to improve the characteristics of recombinant products and to reduce the incidence of inhibitors to FVIII.     

Comparison of the immunogenicity of different therapeutic preparations of human factor VIII in the murine model of hemophilia A

Von Willebrand factor (VWF) has been proposed to reduce the immunogenicity of therapeutic factor VIII (FVIII) in patients with hemophilia A. Using FVIII-deficient mice, we compared the immunogenicity of different preparations of plasma-derived (pd) and recombinant (r) FVIII. Treatment of mice with pdFVIII induced significantly lower titers of FVIII inhibitors, as measured by ELISA and in vitro coagulation assays, compared with rFVIII. Furthermore, pre-incubation of rFVIII with excess VWF significantly reduced rFVIII immunogenicity. Our data confirm that pdFVIII induces lower levels of inhibitors than rFVIII, and that VWF is an immuno-chaperone molecule for FVIII.     

Prolonged bleeding-free period following prophylactic infusion of recombinant factor VIII reconstituted with pegylated liposomes

Prophylactic treatment for hemophilia A involves infusion of factor VIII (FVIII) concentrates every 2 to 3 days. Liposomes can be efficacious vehicles for medicines, and surface modification by PEGylation can prolong liposome circulation time. When reconstituted with PEGylated liposomes (PEGLip's), recombinant FVIII binds noncovalently but with high affinity to the external liposome surface. This preparation showed prolongation of FVIII half-life and increased protection from bleeding in preclinical models. Here we report a blinded, controlled, crossover, multicenter clinical study that evaluated the time free from bleeding episodes in patients with hemophilia A during prophylaxis with standard rFVIII (no liposomes) or PEGLip rFVIII (PEGLip reconstituted) at 25 and 35 IU/kg doses. Of 24 enrolled patients, 23 were eligible for efficacy analysis. Mean number of days without bleeds was 7.2 +/- 1.7 with standard rFVIII compared with 13.3 +/- 4.8 with PEGLip rFVIII at the 35 IU/kg dose and 5.9 +/- 1.7 with standard rFVIII versus 10.9 +/- 2.9 with PEGLip rFVIII at the 25 IU/kg dose (P < .05 between treatment groups for each dose). PEGLip rFVIII was well tolerated. These data suggest that reconstitution of rFVIII with PEGLip's may reduce the frequency of treatment during prophylaxis.     

Inhibitors in hemophilia A: mechanisms of inhibition, management and perspectives.

Factor VIII (FVIII) replacement therapy remains the mainstay in hemophilia A care. The major complication of replacement therapy is formation of antibodies, which inhibit FVIII activity, thus dramatically reducing treatment efficiency. The present review summarizes the accumulated knowledge on epitopes of FVIII inhibitors and mechanisms of their inhibitory effects. FVIII inhibitors most frequently target the A2, C2 and A3 domains of FVIII and interfere with important interactions of FVIII at various stages of its functional pathway; a class of FVIII inhibitors inactivates FVIII by proteolysis. We discuss therapeutic approaches currently used for treatment of hemophilia A patients with inhibitors and analyze the factors that influence the outcome. The choice between options should depend on the level of inhibitors and consideration of efficacy, safety, and availability of particular regimens. Advances of basic science open avenues for alternative targeted, specific and long-lasting treatments, such as the use of peptide decoys for blocking FVIII inhibitors, bypassing them with human/porcine FVIII hybrids, neutralizing FVIII-reactive CD4 T cells with anti-clonotypic antibodies, or inducing immune tolerance to FVIII with the use of universal CD4 epitopes or by genetic approaches.     

Pharmacokinetics, coagulation factor consumption and clinical efficacy in patients being switched from full-length FVIII treatment to B-domain-deleted r-FVIII and back to full-length FVIII

Summary.  Concerns have been raised regarding pharmacokinetic performance, efficacy and safety of B-domain-deleted recombinant FVIII (BDD rFVIII). The objective of this study was to perform a retrospective survey of half-life measurements, efficacy and safety in patients with severe haemophilia A, switching treatment from full-length factor VIII (FL FVIII) to BDD rFVIII and then back to FL FVIII. We hypothesized that half-life of FVIII would be equal regardless of product and that total factor consumption and bleeding frequency would be indistinguishable. We report on inhibitor development and outcome following surgery. Patients with severe haemophilia A, exposed to BDD rFVIII were identified from a database. A retrospective analysis of laboratory data and medical notes was undertaken. No significant difference was detected between the half-life measurements during the switch from FL FVIII (T/2 median 9.15 h, range 6.4–22) to BDD rFVIII (T/2 median 9.7, range 4.7–16.8) and back to FL FVIII (T/2 median 9.0, range 5.0–19.5). There was no significant difference in coagulation factor usage (BDD rFVIII median 4803 IU kg⁻¹ year⁻¹, range 659–11 304; FL FVIII median 5349, range 1691–10 146), nor bleeds. Eleven received BDD rFVIII to cover surgical procedures, with no reports of excess bleeding. Thirty-three patients received significant exposure to BDD rFVIII and one developed a low titre inhibitor. BDD rFVIII was found to be equivalent to other FVIII products in terms of pharmacokinetics, clinical efficacy and safety in this study group.     

Hemophilia A--from basic science to clinical practice

This article summarizes achievements of basic research and their implementation in clinical treatment of one of the most common inherited bleeding disorders hemophilia A, which is caused by genetic deficiency of coagulation factor VIII (FVIII). We discuss the structure of FVIII, its major interactions in the intrinsic pathway of blood coagulation, and the catabolism of FVIII. We also discuss achievements in the contemporary clinical practice of treatment of hemophilia A. Replacement therapy has substantially improved by development of purification and virus inactivation procedures, allowing preparation of safe and effective therapeutic plasma-derived FVIII concentrates. We give special attention to the principles used in the development of contemporary recombinant FVIII products, which do not inherit a potential risk for viral or prion transmission. Development of FVIII inhibitory antibodies is the major complication of FVIII replacement therapy. We summarize the accumulated knowledge regarding epitopes of FVIII inhibitors and mechanisms by which they inactivate FVIII and discuss approaches to overcome the effects of inhibitors and to prevent their formation by induction of immunotolerance. We also analyze the main concepts and scientific priorities in the gene-therapeutic approach for treatment of hemophilia A.     

In vitro characterization of recombinant factor VIII concentrates reveals significant differences in protein content,activity and thrombin activation profile

Recombinant factor VIII (rFVIII) concentrates differ due to cell lines, culture conditions, presence of the B domain and authorized potency assays. This study characterizes three commercially available rFVIII concentrates: a second‐generation full length (A), a third‐generation full length (B) and a third‐generation B domain‐deleted (BDD) product (C). rFVIII concentrates were characterized for FVIII activity (FVIII:C) by one‐stage clotting and chromogenic assays, FVIII antigen (FVIII:Ag), thrombin activation profile and FXa‐generation assay. The rFVIII concentrates exhibited significant differences with regard to FVIII:C, FVIII:Ag and thrombin activation profile. Product A had significantly greater FVIII:C and FVIII:Ag relative to the measured values of products B and C. In addition, product A demonstrated faster and more complete activation by thrombin than the two others. BDD product C had the slowest measured thrombin activation rate. Product A exhibited a greater in vitro FXa generation than products B and C. We found no differences in FXa generation among all three products when FXa generation was normalized for FVIII:Ag. The greater FVIII:C and FVIII:Ag values for product A compared with that for products B and C are due to application of different authorized potency assays (one‐stage assay for A vs. chromogenic assay for B and C). The variation in thrombin activation profiles may arise from differences in cell line‐dependent posttranslational modifications of the various recombinant proteins.     

BAY 81‐8973, a full‐length recombinant factor VIII: manufacturing processes and product characteristics

BAY 81‐8973 (Kovaltry^®, Bayer, Berkeley, CA, USA) is an unmodified, full‐length recombinant human factor VIII (FVIII) approved for prophylaxis and on‐demand treatment of bleeding episodes in patients with haemophilia A. The BAY 81‐8973 manufacturing process is based on the process used for sucrose‐formulated recombinant FVIII (rFVIII‐FS), with changes and enhancements made to improve production efficiency, further augment pathogen safety, and eliminate animal‐ and human‐derived raw materials from the production processes. The baby hamster kidney cell line used for BAY 81‐8973 was developed by introducing the gene for human heat shock protein 70 into the rFVIII‐FS cell line, a change that improved cell line robustness and productivity. Pathogen safety was enhanced by including a 20‐nm filtration step, which can remove viruses, transmissible spongiform encephalopathy agents and potential protein aggregates. No human‐ or animal‐derived proteins are added to the cell culture process, purification or final formulation. The BAY 81‐8973 manufacturing process results in a product of enhanced purity with a consistently high degree of sialylation of N‐linked glycans on the molecular surface. The innovative manufacturing techniques used for BAY 81‐8973 yield an effective rFVIII product with a favourable safety profile for treatment of haemophilia A.     

Current and future approaches to inhibitor management and aversion

Immune tolerance induction (ITI) is the most common approach used to eliminate inhibitors that develop in hemophilia A patients following exposure to factor (F) VIII therapy. ITI generally requires ongoing long-term exposure to factor replacement therapy using FVIII or FIX. Although plasma-derived products have been the mainstay of ITI therapy in the past, recent data indicate that high-purity (i.e., recombinant) rFVIII products are probably equally effective. For patients who have failed to respond to ITI treatment, or for those at high risk to do so, immunosuppressive therapy may be helpful. Rituximab has demonstrated a possible clinical benefit in hemophilic and nonhemophilic patients developing FVIII inhibitors, but benefit in those with congenital hemophilia and inhibitors has not been established and more extensive clinical studies are needed. More recently, research on reducing the incidence of inhibitor development has included mutagenizing key epitopes of the FVIII antigenic molecule to alter its immunogenicity without affecting biological activity, as well as induction of tolerance by gene therapy with immunodominant A2 and C2 domains of FVIII presented by B cells as immunoglobulin fusion proteins.     

Antibody formation and specificity in Bethesda‐negative brother pairs with haemophilia A

Antibodies directed towards non‐neutralizing epitopes on the factor VIII protein (FVIII) may be detected in patients with haemophilia A. We evaluated the prevalence of non‐neutralizing antibodies, in 201 inhibitor‐negative brother pairs with severe haemophilia A, enrolled in the Malmö International Brother Study and the Haemophilia Inhibitor Genetics Study. To evaluate binding specificity of the antibodies, ELISA plates were coated with two recombinant full‐length (FL) FVIII‐products and one recombinant B‐domain‐deleted (BDD) product. Seventy‐nine patients (39.3%) had a history of positive inhibitor titre measured by Bethesda assay, and FVIII antibodies were detected in 20 of them (25.3%). Additional 23 samples from subjects without a history of FVIII inhibitors were ELISA‐positive corresponding to a frequency of non‐neutralizing antibodies of 18.9%. The antibody response towards the different FVIII products was heterogenous, and was raised not only towards the non‐functional B‐domain but also towards both FL‐rFVIII and BDD‐rFVIII. In patients considered successfully treated with immune tolerance induction, 25.4% had remaining FVIII antibodies. The number of families with an antibody response in all siblings was increased when the total antibody response was taken into account, further supporting the concept of a genetic predisposition of the immune response. Further studies and careful monitoring over time are required to appreciate the immune response on the risk of inhibitor development or recurrence in the future.     

First and second generation recombinant factor VIII concentrates in previously untreated patients: recovery,safety, efficacy,and inhibitor development

The first of the prospective multicenter studies in previously untreated patients (PUPs) with a recombinant factor VIII (FVIII) concentrate began in January 1989. Over the past 11 years, PUP studies have amassed a great deal of information concerning safety, efficacy, and inhibitor development of the two "first-generation" recombinant (r) FVIII concentrates (Kogenate and Recombinate) and of two "second-generation" products (ReFacto and Kogenate FS, which is formulated with sucrose rather than with albumin). Each of these products has proved to be safe, effective, and well-tolerated. Side effects have been rare and mild in nature. There have been no clinical reactions to hamster or murine proteins. During the course of the multinational PUP trials with Kogenate, Recombinate, and ReFacto, inhibitors developed in 29.7, 31, and 33%, respectively, of severely affected PUPs. Half of these were high titer and half were low titer. In each of these trials, several inhibitors were transient. PUPs and minimally treated patients (MTPs) in the Kogenate SF trial have not been followed long enough to determine the incidence of inhibitor development; however, the product appears to be safe and effective. Following demonstration of safety and efficacy with each rFVIII concentrate in previously treated patients with hemophilia A, studies in PUPs began. In general, the prospective trials in PUPs with each recombinant product were conducted similarly, allowing comparison of data. This article is intended to provide a review of the experience with both first- and second-generation rFVIII products in the prospective clinical trials in PUPs.     

Prolonged activity of a recombinant factor VIII-Fc fusion protein in hemophilia A mice and dogs

Despite proven benefits, prophylactic treatment for hemophilia A is hampered by the short half-life of factor VIII. A recombinant factor VIII-Fc fusion protein (rFVIIIFc) was constructed to determine the potential for reduced frequency of dosing. rFVIIIFc has an ～ 2-fold longer half-life than rFVIII in hemophilia A (HemA) mice and dogs. The extension of rFVIIIFc half-life requires interaction of Fc with the neonatal Fc receptor (FcRn). In FcRn knockout mice, the extension of rFVIIIFc half-life is abrogated, and is restored in human FcRn transgenic mice. The Fc fusion has no impact on FVIII-specific activity. rFVIIIFc has comparable acute efficacy as rFVIII in treating tail clip injury in HemA mice, and fully corrects whole blood clotting time (WBCT) in HemA dogs immediately after dosing. Furthermore, consistent with prolonged half-life, rFVIIIFc shows 2-fold longer prophylactic efficacy in protecting HemA mice from tail vein transection bleeding induced 24-48 hours after dosing. In HemA dogs, rFVIIIFc also sustains partial correction of WBCT 1.5- to 2-fold longer than rFVIII. rFVIIIFc was well tolerated in both species. Thus, the rescue of FVIII by Fc fusion to provide prolonged protection presents a novel pathway for FVIII catabolism, and warrants further investigation.     

Kinetics of the interaction between anti‐FVIII antibodies and FVIII from therapeutic concentrates,with and without von Willebrand factor,assessed by surface plasmon resonance

The presence of VWF in plasma‐derived FVIII (pdFVIII/VWF) products has been pointed out as a key difference with recombinant FVIII (rFVIII) products with regard to immunogenicity. A Surface Plasmon Resonance (SPR) study was designed to characterize in detail the interaction between anti‐FVIII (IgGs) from a severe haemophilia A patient, and FVIII from concentrates of different sources. Full‐length rFVIII (preincubated or not with purified VWF), B domain‐deleted (BDD)‐rFVIII and pdFVIII/VWF were analysed. To ensure reproducible conditions for accurate determination of kinetic constants, a capture‐based assay format was developed using protein G surfaces for specific and reversible coupling of endogenous anti‐FVIII antibodies. Concentration ranges (nm ) of FVIII products tested were 9–0.03 (rFVIII) and 6–0.024 (pdFVIII/VWF). The association with antibodies was monitored for 3–5 min, whereas dissociation of the complex was followed for 5–20–240 min. A strong interaction of rFVIII and BDD‐rFVIII with patient's IgG was detected with the K _D values in the low picomolar range (5.9 ± 3.0 and 12.7 ± 6.9 pm , respectively) and very slow dissociation rates, while pdFVIII/VWF showed only marginal binding signals. The VWF complexed rFVIII displayed reduced binding signals compared with uncomplexed rFVIII, but the K _D was still in the picomolar range (4.1 ± 1.9 pm ) indicating insufficient complex formation. rFVIII, alone or bound to exogenously added VWF, showed high affinity for anti‐FVIII IgGs from a severe haemophilia A patient whereas pdFVIII/VWF did not. These results are in agreement with those studies that point towards rFVIII concentrates to be more immunogenic than pdFVIII concentrates.     

Forum on: the role of recombinant factor VIII in children with severe haemophilia A

Summary. The development of recombinant FVIII (rFVIII) products, fuelled by the need for improved safety of treatment arising from the dramatic widespread blood‐borne virus transmission in the 1970–1980s revolutionized the care of children with haemophilia A over the last two decades. The larger availability of perceived safer replacement therapy associated with the introduction of rFVIII products reassured the haemophilia community and there was a strong push in some Western countries to treat haemophilic children only with rFVIII. Moreover, this significantly contributed in the 1990s to the diffusion outside Northern Europe of prophylactic regimens implemented at an early age to prevent bleeding and the resultant joint damage (i.e. primary prophylaxis), together with the possibility of home treatment. These changes led to a substantial improvement of the quality of life of haemophilic children and of their families. The general agreement that primary prophylaxis represents the first‐choice treatment for haemophilic children has been recently supported by two randomized controlled trials carried out with rFVIII products, providing evidence on the efficacy of early prophylaxis over on‐demand treatment in preserving joint health in haemophilic children. However, the intensity and optimal modalities of implementation of prophylaxis in children, in particular with respect to the issue of the venous access, are still debated. A number of studies also supports the role of secondary prophylaxis in children, frequently used in countries in which primary prophylaxis was introduced more recently. With viral safety now less than an issue and with the more widespread use of prophylaxis able to prevent arthropathy, the most challenging complication of replacement therapy for children with haemophilia remains the risk of inhibitor development. Despite conflicting data, there is no evidence that the type of FVIII concentrate significantly influences the complex multifactorial process leading to anti‐FVIII alloantibodies, whereas other treatment‐related factors are likely to increase (early intensive treatments due to surgery or severe bleeds) or reduce (prophylaxis) the risk. Although the optimal regimen is still uncertain, eradication of anti‐FVIII antibodies by immune tolerance induction (ITI), usually with the same product administered at inhibitor detection, should be the first‐choice treatment for all patients with recent onset inhibitors. This issue applies particularly to children, as most patients undergo ITI at an early age, when inhibitors usually appear. The availability of a stable and long‐lasting venous access represents a leading problem also in this setting. These and other topics concerning rFVIII treatment of haemophilic children were discussed in a meeting held in Rome on 27 February 2008 and are summarized in this report.     

Results from a large multinational clinical trial (guardian™1) using prophylactic treatment with turoctocog alfa in adolescent and adult patients with severe haemophilia A: safety and efficacy

Recombinant factor VIII (rFVIII) products provide a safe and efficacious replacement therapy for prophylaxis and treatment of bleeding episodes in patients with severe haemophilia A. This multinational, open‐label, non‐controlled trial investigated the safety and efficacy of turoctocog alfa, a new rFVIII product. The primary objective was to evaluate safety. A total of 150 patients (24 adolescents and 126 adults) with severe haemophilia A (FVIII activity ≤1%), with at least 150 exposure days (EDs) to any FVIII product and no history of inhibitors were enrolled, and 146 patients (97%) completed the trial. All patients received prophylaxis with turoctocog alfa for approximately 6 months and had a mean of 85 EDs during the trial. None of the patients developed FVIII inhibitors, there were no indications of early FVIII inhibitor development and no safety concerns were identified. A total of 225 adverse events were reported in 100 (67%) patients, with the most common being events associated with dosing procedures, headaches, and nasopharyngitis. A total of 499 bleeding episodes were reported during the trial, the majority (89%) were controlled with 1–2 infusions of turoctocog alfa. Based on patient reports, the success rate (defined as ‘excellent’ or ‘good’ haemostatic response) for treatment of bleeding episodes was 81%. The overall median annualized bleeding rate was 3.7 (interquartile range: 8.7) bleeds/patient/year. In conclusion, turoctocog alfa provides a new, safe and effective alternative for prophylaxis and treatment of bleeding episodes in patients with haemophilia A.