Plasma-derived Factor VIII Products Research Articles

Emizicumab Promotes Factor Xa Generation on Activated Endothelium in a Blood Cell-Independent Manner

IntroductionHemophilia A (HA) is an inherited bleeding disorder caused by the deficiency of coagulation factor VIII (FVIII) resulting in severe hemorrhage if untreated. Recombinant and plasma derived FVIII products have long been the standard of care in hemophilia. However, approximately 25-30% of patients with severe HA develop inhibitors, neutralizing alloantibodies to FVIII, a significant complication in the treatment of patients with HA that leads to bleeding despite factor therapy.First approved for bleed prophylaxis in HA with inhibitors in the US by the FDA in 2018, emicizumab (Genentech, USA) has initiated a new era of HA treatment. This drug is a bispecific, monoclonal antibody that binds to activated Factor IX (FIXa) and Factor X (FX), mimicking activated FVIII (FVIIIa) by bringing FIXa and FX into proximity to enable FX activation, even in the presence of inhibitors.Emicizumab prophylaxis drastically reduces bleed episodes. However, thromboses and thrombotic microangiopathy (TMA) were observed in trials, all associated with concomitant use of activated prothrombin complex concentrates (aPCC) (Callaghan et al., 2021). The mechanism of this devastating condition is uncertain, as emicizumab is not known to bind to phospholipid or vascular surfaces. We report that FX is more readily activated by FIXa and emicizumab on endothelium that has been activated by tumor necrosis factor alpha (TNF). This finding may partially explain the development of TMA in these patients.MethodsWe utilized novel, microfluidic devices that are inexpensive to manufacture and were modified from a technique previously described (Alapan et al. 2016). These devices are fabricated using a laser cut double-sided adhesive film sandwiched between a clear, gas-permeable polymer (Ibidi, Germany) and an acrylic top that is laser cut (Universal Laser Systems Inc., USA) (Figure 1).Human umbilical endothelial cells (HUVEC, Lonza, Switzerland) were harvested at passage 3 to 4 and seeded into the devices. These were then cultured under flow conditions using a non-peristaltic, air-driven pump (Ibidi GmbH, Germany) to achieve a confluent and quiescent endothelial surface. HUVEC are then activated by incubating with 5 nM TNF in serum-free growth medium for 4 hours. This treatment induced markers of endothelial activation without gross apoptosis. Non-activated HUVEC were incubated with endothelial cell growth medium (2% serum) until time of experiments.Factors IXa, X (Haemtech, USA), and/or emicizumab (discarded clinical material) were mixed in HEPES-buffered saline with 5 mM calcium chloride for all experimental conditions. Concentrations used of FIXa (30 nM), FX (170 nM), and emicizumab (55 ug/mL) were constant for all conditions. Combinations of factors and emicizumab were then incubated in the endothelialized device for 30 minutes at 37° C. The entire volume of the mixture was then aspirated (20 uL) and stored at -80° C.FXa activity was assayed on the effluent for 60 minutes using a chromogenic FXa substrate (Pefachrome, Pentapharm, Switzerland).ResultsNo significant generation of Xa was noted in the presence of healthy or activated endothelium with emicuzumab alone, emicizumab and FIXa, emicizumab and FX, or factors IXa and X. Median Xa generation observed with the combination of emicizumab, FIXa, and FX on healthy endothelium was 2 nM. Median Xa generation with the same combination on activated endothelium was 8.1 nM, a four-fold increase (P = 0.028, Mann-Whitney test) (Figure 2).DiscussionEmicizumab represents an evolving standard of care for hemophilia A. Considering data showing diminishing FVIII expression in the months to years after AAV gene therapy, (Pasi et al., 2020) it may well be the dominant treatment paradigm in HA for some time.However, much remains to be answered in the use of emicizumab, and the mechanism of thrombosis and TMA with concomitant aPCC use has resulted in the avoidance of aPCC use for breakthrough bleeding in patients on emicizumab therapy, even up to 6 months after cessation.Our data demonstrate that activated endothelial cells promote FX activation more readily than quiescent endothelial cells in the presence of FIXa and emicizumab. These findings demonstrate the potential of thrombotic angiopathy in an in vitro system. Further investigation of the interaction of endothelium with FIXa, FX, and FVIIIa-mimetic antibodies is warranted. [Display omitted] DisclosuresEllsworth: Takeda: Other: Salary supported as part of NHF-Takeda Clinical Fellowship Award. Monroe: Medexus Pharmaceuticals: Consultancy; Takeda: Consultancy; Otello Medical: Current equity holder in publicly-traded company. Hoffman: Takeda: Research Funding; CSL Behring: Consultancy; Sanofi: Consultancy; BPL (Bio Products Laboratory): Consultancy. Key: BioMarin: Honoraria, Other: Participation as a clinical trial investigator; Takeda: Research Funding; Grifols: Research Funding; Uniqure: Consultancy, Other: Participation as a clinical trial investigator; Sanofi: Consultancy.

Factor VIII products: key aspects of development, clinical research and use (part 2)

Continuous replacement therapy with clotting factor products can lead to serious complications in haemophilia A patients. One of potential reasons of such complications is an undesirable immune response to a blood clotting factor VIII (FVIII) product, which undermines the treatment effectiveness. The aim of the study was to systematise and summarise data on undesirable immunogenicity of plasma-derived and recombinant FVIII products, formation of immunological tolerance, and modern approaches to the development of clinical trial programmes for such products. The analysis was based on scientific literature, as well as Russian and international guidelines, including the updated document of the European Medicines Agency. The paper presents clinical trial data on pharmacokinetics, efficacy, and safety of FVIII products, including data on manifestations of unwanted immunogenicity. It highlights molecular mechanisms of interaction between inhibitors and FVIII, and analyses the main factors (genetic characteristics, immune status of patients, dosage regimen, etc.) affecting the frequency and intensity of the immune response to the product. The authors summarised approaches to the clinical trial design, including selection of patients and studied parameters. They substantiate the need for post-authorisation studies to collect additional clinical data on both efficacy and safety of the routine use of the product, including additional assessment of immunogenicity and other adverse reactions. It is concluded that the successful use of high-quality FVIII products ensures by harmonisation of requirements of Russian and international regulatory documents.

Changes in Factor VIII:C Activity over 24 Hours Depending on Diluent and Storage Conditions after Dilution

Background : Continuous infusion of factor VIII (FVIII) is a more cost-effective method for treating hemophilia A than intermittent bolus injection, especially when undergoing surgery. The activity of the factor 8 concentrates may gradually decreases over 24 hours at room temperature, making it difficult to maintain a desired appropriate blood concentration. However, there are no specific guidelines for precise method and duration of continuous intravenous. administration of factor VIII products. In this study, we evaluate in vitro factor VIII activity during 24 hours after reconstitution with diluent fluid in various conditions to propose an effective continuous i.v. infusion method.Method : A total 6 of coagulation factor VIII concentrates were used (2 plasma derived FVIII products and 4 recombinant FVIII products) - Greengene-F®,Advate®, Xyntha®, monoclateP®, Koginate®,Immunate®. Each drug was dissolved in the enclosed water for injection according to the manufacturer's instruction. After 30 minutes of stabilizing, each drug was further diluted in sterilized distilled water or normal saline or dextrose water was adjusted to the same concentration for this experiment. Then, the drugs were stored at refrigeration or room temperature with exposure to light or light-shielded. In vitro FVIII:C was measured at five time points (0, 2, 4, 6, 8, and 24 hours after reconstitution) with a one-stage clotting assay a CS5100 coagulation analyzer system from Sysmex. Then, the factor VIII activity of each time was statistically compared with activity of 0 hour.Results: With all experimental conditions, FVIII activities of all 6 drugs persistently decreased over the course of 24 hours (p <0.001). There was a significant difference in the degree of decrease in activity over time depending on the type of drug (p <0.001), the activity after 2 hours is 47.58 to 90.76 %, the activity after 4 hours is 31.58 to 86.21 %, the activity after 8 hours is 6.49 to 77.03 %, the activity after 18 hours is 2.24 to 75.49 %, the activity after 24 hours is 1.23 to 73.63%. Two hours after the dilution, the FVIII activity decreased to 80% or less with 3 of 6 drugs. After 4 hours, 5 of 6 drugs had the FVIII activity of 80% or less, and after 6 hours the FVIII activity decreased to less than 80% in all of 6 drugs. There was a difference in the degree of decrease in activity depending on the presence or absence of shading and refrigeration, and diluent solutions (normal saline or dextrose water instead of distilled water), but there was a difference between the drugs and consistent correlation was not observed.Conclusions : When the FVIII concentrates were diluted, the activity of each of the six drugs decreased significantly over the 24 hours in vitro, and the degree of decrease was significantly different according to the exposed conditions although there was a difference by drug. Based on the results of the continuous decrease in FVIII activity over time, it is not appropriate to dissolve a 24-hour dose in a large amount of diluted fluid at one time and continuously infuse during 24 hours. Replacing the concentrate before 2 to 6 hours after dilution is probably a better method to maintain desired FVIII activity in patients with hemophilia. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Do We Really Need Plasma-Derived FVIII Concentrates in Every PUP to Minimize the Risk of Inhibitor Development?

Background:The development of inhibitors due to infused factor VIII (FVIII) remains a significant challenge in haemophilia treatment, particularly in previously untreated patients (PUPs). Inhibitors in PUPs usually develop within the first 50 exposure days (EDs), with a median time to inhibitor development of around 10-15 EDs. The impact of product type on the risk of inhibitor development remains controversial. Whilst some studies have found no difference in the rate of inhibitor development between plasma-derived (pd) and recombinant (r)FVIII products, other studies have reported higher rates of inhibitor development after treatment with rFVIII. The prospective, randomised SIPPET study found an 87% higher incidence of inhibitors in PUPs treated with rFVIII than in PUPs treated with pdFVIII concentrates containing von Willebrand factor (VWF).MethodsThe aim of this study was to investigate a personalised treatment approach in PUPs in order to limit both joint damage and inhibitor development. This approach included the use of intensive monitoring from an early age, tailored prophylaxis using pdFVIII concentrates and personalised physiotherapy regimen. FVIII levels and Von Willebrand Antigen (VWF-Ag) were measured after birth (if possible), before start of prophylaxis and during prophylaxis. The inhibitor titre was measured every 3-4 EDs. Our study cohort was compared with a historical cohort (2004 - 2012) treated with early prophylaxis with hamster cell-derived rFVIII or pdFVIII. We enrolled 24 patients, 9 from the historical cohort (7 treated with rFVIII and 2 with pdFVIII) and since 2013 15 patients from in the study cohort (14 treated with pdFVIII and 1 not yet treated).Results:Since 2013 all 14 PUPs started early prophylaxis with pdFVIII/VWF. Initial dose ranged from 25 IU/kg/10 days to 60 IU/kg/week for the first 20 ED and thereafter individual dose escalation was performed. So far, no patient had developed and inhibitor to FVIII. In our historical group 4 out of 7 patients developed a high titre inhibitor (≥ 5 BU) during the first 20 EDs with rFVIII, but none of the patients receiving prophylaxis with pdFVIII (n=2) (p=0.007).All patients who developed an inhibitor later on had a VWF-Ag below 77%, those patients receiving rFVIII and remaining without an inhibitor had an VWF-Ag above 77% (n=3); this difference was highly significant (p<0.001).Conclusion:We found that individually tailored treatment schedules and early prophylaxis seems to minimize the incidence of inhibitors in our cohort. Nevertheless, it has to be investigated if PUPs with a high VWF-level can be treated safely with rFVIII without risking the development of inhibitors. We recommend further prospective studies with a greater number of patients. DisclosuresHalimeh:Bayer healthcare, Baxalta Innovations, Biotest, CSL Behring, Novartis, Novo Nordisk, Octapharma, LFB, Pfizer: Honoraria; Bayer Healthcare, Baxalta Innovations, Biotest, CSL Behring, Novo Nordisk, Octapharma, Pfizer: Research Funding.

Components in Plasma-Derived Factor VIII, But Not in Recombinant Factor VIII Downregulate Anti-Inflammatory Surface Marker CD163 in Human Macrophages through Release of CXCL4 (Platelet Factor 4)

Background: Hemarthrosis, or bleeding into the joints, is a hallmark of hemophilia. Heme triggers oxidative stress, inflammation, and destruction of cartilage and bone. The haptoglobin-CD163-heme oxygenase-1 (HO-1) pathway circumvents heme toxicity through enzymatic degradation of heme and transcription of antioxidant genes. Plasma-derived factor concentrates contain many proteins that might impact on cellular pathways in joints, blood, and vessels. Methods: Activation of platelets from healthy volunteers was assessed by flow cytometry analysis of fibrinogen binding and CD62P expression. Platelet CXCL4 release was measured by ELISA. Human peripheral blood mononuclear cells were exposed to CXCL4 or platelet supernatants (untreated or pre-stimulated with factor VIII (FVIII) products) during their differentiation to macrophages and analyzed for CD163 expression. Some macrophage cultures were additionally incubated with autologous hemoglobin for 18 h for analysis of HO-1 expression. Results: Platelet CXCL4 release was increased by all 8 tested plasma-derived FVIII products but not the 3 recombinant products. Macrophages exposed to supernatant from platelets treated with some plasma-derived FVIII products downregulated CD163 surface expression and failed to upregulate the athero- and joint protective enzyme HO-1 in response to hemoglobin. Conclusion: Plasma-derived FVIII products might promote bleeding-induced joint injury via generation of macrophages that are unable to counteract redox stress.

Risk Differential in Inhibitor Development in the First Days of Treatment By Product Class: A Sippet Analysis

BACKGROUNDAdministration of factor VIII (FVIII) concentrates to patients with severe hemophilia A has nearly normalized their life expectancy; however, a substantial number of previously untreated patients (PUPs) develop neutralizing alloantibodies (inhibitors) against FVIII that complicate the benefits of treatment and make the management of these patients difficult and costly. Recently a randomized clinical trial (SIPPET) showed that the risk of inhibitor development is nearly doubled in previously untreated and minimally treated patients with severe hemophilia A treated with recombinant products (rFVIII) compared with plasma-derived (pdFVIII) products containing von Willebrand factor (VWF). AIMThe aim of this post-hoc analysis of the SIPPET study was to assess the early risk of inhibitor development every 5 exposure days (EDs) and to see whether or not there was a difference between the two arms of plasma-derived FVIII and recombinant FVIII products over the course of time of FVIII exposure. METHODS251 children were enrolled in the SIPPET study and randomized to receive a single pd or rFVIII (4 different brands of each). The outcomes were any FVIII inhibitor levels ≥ 0.4 Bethesda Units (BU) and high-titer inhibitors (peak levels > 5 BU). Patients were tested for inhibitors before entry and at regular intervals during 50 EDs, 3 years or the development of an inhibitor. Patients who had not reached 50 EDs by the time of study termination were censored. To study the risk over time, survival analysis by Kaplan-Meier and Cox regression were repeated for every 5 EDs to assess the association of source of FVIII with inhibitor development over time. RESULTS76 out of 251 patients developed an inhibitor and of those 50 were high-titer; all occurred before 40 EDs.Over the complete observation period, users of rFVIII products had a 87% higher rate of inhibitor development than users of pdFVIII (hazard ratio (HR) 1.87; 95% confidence interval (CI95) 1.17-2.96). The hazard ratio was particularly high during the first 5 EDs, both for all (HR 3.14, CI95% 1.01-9.74) and high-titer inhibitor development (HR 4.19, CI95% 1.18-14.8). After the first 5 EDs, the difference between two arms was less pronounced and quickly dropped to the overall difference of 1.87. Table 1 shows the cumulative incidence per time interval for each of the product classes. CONCLUSIONThe risk of inhibitor development during replacement therapy occurs more early (0-5 EDs) in patients treated with rFVIII than in those treated with pdFVIII, and remains high until 15 EDs. For pdFVIII, the highest risk came later (6-10 EDs) and this peak lasted shorter. The results of this analysis shows the relevance of the early exposure days for inhibitor development. [Display omitted] DisclosuresPeyvandi:Alexion: Other: research funding paid to Luigi Villa Foundation, Research Funding; Novo Nordisk: Other: research funding paid to Luigi Villa Foundation, Research Funding, Speakers Bureau; Bayer: Speakers Bureau; Kedrion Biopharma: Consultancy, Other: research funding paid to Luigi Villa Foundation, Research Funding; LFB: Consultancy; CSL Behring: Speakers Bureau; Biotest: Other: research funding paid to Luigi Villa Foundation, Research Funding, Speakers Bureau; Octapharma: Consultancy; Ablynx: Membership on an entity's Board of Directors or advisory committees, Other: research funding paid to Luigi Villa Foundation, Research Funding; SOBI: Speakers Bureau; Grifols: Speakers Bureau. Palla:Pfizer: Other: travel support . Mannucci:Bayer: Speakers Bureau; Grifols: Speakers Bureau; Kedrion: Speakers Bureau; NovoNordisk: Speakers Bureau.

Inhibitors in Severe Hemophilia A: 25-Year Experience in Slovakia.

We present 25-year experience with inhibitors in previously untreated patients (PUPs) with severe hemophilia A in Slovakia, where safe factor VIII (FVIII) concentrates have been used since 1990. A prospective study focused on inhibitor incidence in PUPs was established in 1997. Out of a total 61 PUPs born between January 1997 and October 2015, 59 were eligible for evaluation; 50 and 9 were treated with > 20 exposure days (ED) of plasma-derived FVIII (pdFVIII) and recombinant FVIII (rFVIII) products, respectively. In the entire group 13/59 (22%) PUPs developed inhibitors; i.e. 7/50 (14%) and 6/9 (67%) treated with pdFVIII and rFVIII, respectively. Univariate analysis of inhibitor risk factors in patient groups with and without inhibitors showed the rFVIII and serious/recurrent infections within the first 50 EDs to be associated with inhibitor development (OR of 12.3 [95% CI 2.48-60.83; p = 0.002] and 5.0; [95% CI 1.16-21.9; p = 0.03), respectively]). Also, in multivariate Cox regression analysis, peak treatment ≥ 5 EDs reached statistical significance. The hazard ratio (HR) was 7.15 (95% CI 1.65-31.36) p = 0.0086 for rFVIII and 4.38 (95% CI 1.02-18.67) p = 0.046 for intensive treatment. Between 1993 and 2015, 21 immune tolerance inductions (ITIs) in 19 inhibitor patients were performed in the two largest hemophilia centers in Slovakia. In all but one ITI courses pdFVIII containing von Willebrand factor (FVIII/VWF) was used with preferred use of high-dose ITI (HD ITI) in high responders (HRs). Complete or partial success was achieved in 17/19 (89.5%) patients. Evaluating only the patients who already completed ITI, the success rate was even higher (15/16; 94%), including 7/7 low responders and 8/9 HR. Our national prospective study comprising entire group of PUPs with severe hemophilia A showed higher incidence of inhibitors in patients treated with rFVIII and those with intensive therapy within first 50 EDs. However, our experience is limited to small numbers of patients; thus, our results must be interpreted cautiously. High success rate of the ITI in our inhibitor patients has been achieved with FVIII/VWF concentrates and preferred use of HD ITI in HR patients.

Immune Tolerance Induction in Severe Hemophilia a Patients Using Wilate®, a Von Willebrand Factor/Factor VIII Concentrate

Introduction: To prevent and treat bleeding episodes, hemophilia A patients undergo factor VIII (FVIII) replacement therapy with either recombinant FVIII (r-FVIII) or plasma-derived FVIII (pd-FVIII). Approximately 32% of patients develop neutralizing antibodies to the FVIII protein rendering FVIII therapy ineffective (Gouw et al. N Engl J Med. 2013; 368:231-239). Development of these neutralizing antibodies, or ‘inhibitors’ is the most serious and challenging complication in the treatment of hemophilia A patients and represents the highest economic burden for a chronic disease (Gringeri et al. Blood 2003; 102:2358-2363). The standard approach for eradicating inhibitors is to tolerize the patient to FVIII through prolonged, daily exposure to high-dose FVIII – a process termed immune tolerance induction (ITI). Although costly, ITI can successfully eliminate inhibitors in a large proportion of low-risk patients, however there are several risk factors that reduce the likelihood of ITI success. For high-risk patients, the choice of drug product (r-FVIII versus pd-FVIII) may be particularly important. Several small studies have demonstrated the superiority of pd-FVIII for ITI, as these products contain the FVIII stabilizing protein, von Willebrand Factor (VWF) (Gringeri et al., Haemophilia 2007; 13:373-379). Wilate® (Octapharma) is a high-purity pd-FVIII complex that contains the two proteins (VWF and FVIII) in a 1:1 ratio. In this retrospective study, we present the patient history and outcome for four severe hemophilia A patients that have undergone ITI with Wilate®. Patients and Methods. All patients presented with severe FVIII deficiency ( Results. ITI with Wilate was found to be well tolerated, with no reported drug-related adverse events. Although 75% of the patients presented with high-risk factors for poor ITI outcome, Wilate ITI reduced inhibitor levels below 5 BU/mL for 3 out of 4 patients. The clinical outcome of Wilate ITI correlated with the presence and number of high-risk factors. Patient 1 did not respond to Wilate, and was considered a failure. This patient had 3 high risk factors for poor ITI outcome including FVIII gene mutation type, peak historical titer >50, and inhibitor titer at ITI onset > 10 BU/mL. Of the three patients that responded to Wilate ITI, patient 4 experienced a CS to Wilate ITI in 4 months. For the remaining 2 patients, Wilate ITI is currently ongoing. Despite the presence of high risk factors, these two patients have thus far achieved a PS with inhibitor levels stable for several months at or below 1 BU/mL. One of these patients (patient 2) presented with 5 high-risk factors, including having failed a previous ITI attempt. The frequency of bleeding episodes were significantly reduced upon commencement of Wilate ITI, allowing for the eventual cessation of FEIBA prophylaxis. Conclusion. Despite the presence of high-risk factors, 3 out of 4 patients (75%) experienced a clinical response to Wilate ITI. The patients experienced improved quality of life. Wilate ITI resulted in a significant reduction in bleed episodes in a high-risk patient. The type of FVIII product to use during ITI has been debated, however, some have observed a higher success rate when plasma-derived FVIII products containing VWF are used. From our experience, we conclude that Wilate for ITI in patients with inhibitors is effective and produces high rates of ITI success in high-risk patients. Disclosures Wu:Bayer: Honoraria, Membership on an entity9s Board of Directors or advisory committees, Research Funding; Baxter: Honoraria; Pfizer: Membership on an entity9s Board of Directors or advisory committees; Biogen Idec: Honoraria, Membership on an entity9s Board of Directors or advisory committees; Novo Nordisk: Honoraria, Membership on an entity9s Board of Directors or advisory committees; Octapharma: Honoraria, Membership on an entity9s Board of Directors or advisory committees; CSL Behring: Honoraria, Membership on an entity9s Board of Directors or advisory committees. Woo:Bayer: Honoraria, Membership on an entity9s Board of Directors or advisory committees; Baxter: Honoraria, Membership on an entity9s Board of Directors or advisory committees; Pfizer: Honoraria, Membership on an entity9s Board of Directors or advisory committees. Crilly:Bayer: Consultancy, Honoraria, Membership on an entity9s Board of Directors or advisory committees; Baxter: Consultancy, Honoraria, Membership on an entity9s Board of Directors or advisory committees; Octapharma: Honoraria, Membership on an entity9s Board of Directors or advisory committees.

Novel investigations on the protective role of the FVIII/VWF complex in inhibitor development

Development of inhibitory antibodies to infused factor VIII (FVIII) concentrates is the most serious unresolved complication of haemophilia A treatment. Systematic reviews suggest a twofold higher incidence of inhibitors with recombinant (rFVIII) vs. plasma-derived (pdFVIII) FVIII products, but study methodologies vary widely. The lower immunogenicity of pdFVIII concentrates is believed to derive from the presence of von Willebrand factor (VWF) which acts as protector and chaperone for FVIII. Several novel investigations reinforce the protective role of the VWF/FVIII complex in inhibitor development. At the basic science level, numerous in vitro and in vivo experiments have demonstrated that VWF-containing pdFVIII concentrates (pdFVIII/VWF) provide better protection against inhibitor neutralization than rFVIII products. Conformational aspects of the binding between VWF and FVIII are thought to prevent the 'attack' on FVIII by inhibitory antibodies. VWF/FVIII binding is 100% in pdFVIII products but only 80% in recombinant products and this 'free' FVIII may be a target for inhibitory antibodies. At the clinical level, newer strategies to prevent inhibitor development in previously untreated patients with severe haemophilia are under investigation. The concept of early prophylaxis (before the onset of a bleed) is convincing from a theoretical point of view but requires further evaluation. The Study on Inhibitors in Plasma-Product Exposed Toddlers is specifically addressing the issue of relative immunogenicity between classes of FVIII product (recombinant vs. plasma-derived). Currently nearing its target enrolment of 300 patients, this international randomized controlled trial is expected to provide some definitive answers about this ever-present clinical dilemma.

Systematic Review of the Role of FVIII Concentrates in Inhibitor Development in Previously Untreated Patients with Severe Hemophilia A: A 2013 Update

Nowadays, patients with hemophilia A receive a high standard of care; therefore, the most challenging complication of factor VIII (FVIII) replacement therapy has become the development of FVIII inhibitors, which render the concentrate infusion ineffective and expose patients to an increased risk of morbidity and mortality. Among environmental risk factors influencing inhibitor development, the type of FVIII products has always drawn the attention of investigators. Conflicting results are reported in the literature concerning rates of inhibitor development after either plasma-derived or recombinant FVIII concentrates. To help elucidate this controversial issue, we have performed a systematic review and meta-analysis of prospective studies evaluating the incidence of inhibitors in previously untreated patients with severe hemophilia A receiving plasma-derived or recombinant FVIII products. The quality of the studies was assessed using the Newcastle-Ottawa Scale (NOS), the STrenghtening the Reporting of OBservational studies in Epidemiology and an ad hoc quality score. Overall, 28 prospective studies, including 1,421 patients with hemophilia A, fulfilled our selection criteria and were included in the systematic review. No statistically significant differences were observed in the inhibitor incidence between plasma-derived and recombinant FVIII concentrates considering all (weighted means: 23%, 95% CI: 15-33% vs. 29%, 95% CI: 26-32%) and high titer (16%, 95% CI: 10-26% vs. 18%, 95% CI: 15-21%) inhibitors. Similarly, no significant differences were found in the inhibitor incidence among the different classes of recombinant products. In conclusion, the results of our meta-analysis show that the different types of FVIII products are not associated with different risks of inhibitor development.

Hemophilia A in the third millennium

Hemophilia A is an X-linked hereditary bleeding disorder due to the deficiency of coagulation factor VIII (FVIII). According to the degree of FVIII deficiency, mild, moderate or severe forms are recognized. Although patients with mild hemophilia A usually bleed excessively only after trauma or surgery, those with severe hemophilia experience frequent episodes of spontaneous or excessive bleeding after minor trauma, particularly into joints and muscles. The modern management of hemophilia began in the 1970s and is actually based upon several plasma-derived or recombinant FVIII products. In addition, the synthetic drug desmopressin can be used to prevent or treat bleeding episodes in patients with mild hemophilia A. Long-term and continuous substitution therapy (prophylaxis), the recommended treatment in severe hemophilia, prevents bleeding and the resultant joint damage. In the last twenty years the high standard of hemophilia care has greatly improved the quality of life of patients and their life expectancy has reached that of the non-hemophilic male population, at least in high-income countries. The most serious and challenging complication of treatment of hemophilia A is the development of inhibitors, which renders FVIII concentrate infusion ineffective and exposes patients to an increased risk of morbidity and mortality. In this narrative review, the actual knowledge on the clinical features and management of patients with hemophilia A is summarized.

Von Willebrand factor-containing factor VIII concentrates and inhibitors in haemophilia A

The development of inhibitors that neutralise the function of factor VIII (FVIII) is currently not only the most challenging complication associated with the treatment of haemophilia A but it also increases the disease-related morbidity as bleeding episodes do not respond to standard therapy. The main short-term goal of the treatment of inhibitor patients is to control bleeding episodes while the long-term one is to permanently eradicate the inhibitor by immune tolerance induction, particularly in the case of high-titer antibodies. Due to some in vitro studies and clinical observations, some investigators have suggested that FVIII concentrates containing von Willebrand factor (VWF) may be less immunogenic than high-purity or recombinant FVIII products. It has also been suggested that success rates for immune tolerance induction are higher when plasma-derived FVIII products are used. The currently available data from laboratory and clinical studies on the role of VWF in inhibitor development and eradication in haemophilia A is critically analysed in this review. As a result, we have not found definitive evidence supporting a role for product type on inhibitor incidence and inhibitor eradication in haemophilia A patients.

Combined Factor V and Factor VIII Deficiency

Combined deficiency of factor V (FV) and factor VIII (FVIII) (F5F8D, or FV+FVIII) is a autosomal recessive bleeding disorder caused by mutations in genes encoding two components of the endoplasmic reticulum (ER)-Golgi intermediate compartment (ERGIC-53), that is, lectin mannose binding protein ( LMAN1) and multiple coagulation factor deficiency 2 ( MCFD2), involved in the FV and FVIII intracellular transport rather than by DNA defects in the genes that encode the corresponding coagulation factors. F5F8D is estimated to be extremely rare (1:1,000,000) in the general population, but an increased frequency is observed in regions where consanguineous marriages are practiced. F5F8D is characterized by concomitantly low levels (usually between 5% and 20%) of both FV and FVIII and is associated with a mild to moderate bleeding tendency. Treatment of bleeding episodes requires a source of both FV and FVIII; replacement of FV is achieved only through use of fresh-frozen plasma (FFP) and replacement of FVIII by FFP and desmopressin or specific FVIII concentrates (plasma-derived or recombinant FVIII products).

Inhibitor development in haemophilia A: the role of von Willebrand factor/factor VIII concentrates

The presence of inhibitors that neutralize the function of factor VIII (FVIII) decreases the haemostatic efficacy of replacement clotting factor concentrate and increases morbidity among patients with haemophilia A. Certain genetic and environmental variables have been linked to a higher incidence of inhibitors. Conversely, the presence of von Willebrand factor (VWF) in some plasma-derived FVIII products may provide some measure of protection against inhibitor development, although the evidence is not conclusive. Clinical trials are needed to resolve this issue and determine the appropriate role of VWF-containing FVIII concentrates in the treatment of haemophilia A patients.

Treating haemophilia A with recombinant blood factors: a comparison

The mainstay in the treatment of haemophilia A is replacement therapy with repeated infusions of plasma-derived Factor VIII (FVIII) concentrates or recombinant FVIII products. While modern plasma-derived FVIII concentrates have an excellent safety profile, there is an inexorable shift towards the use of recombinant products, especially in affluent countries. Recombinant FVIII products have demonstrated excellent haemostatic efficacy and higher safety with regard to the transmission of blood-borne pathogens. The experience in haemophilia A treatment with five currently available recombinant FVIII products, including the first third-generation product, Advate®, which is completely free from human or animal proteins, is summarised. Some unresolved problems concerning the efficacy and assaying of recombinant factors and future perspectives of both recombinant and plasma-derived FVIII products in global haemophilia care, are also discussed.