High Risk Of Inhibitor Development Research Articles

F9 mutations causing deletions beyond the serine protease domain confer higher risk for inhibitor development in hemophilia B

F9 mutations causing deletions beyond the serine protease domain confer higher risk for inhibitor development in hemophilia B

Hemophilia: The Past, the Present, and the Future.

Hemophilia: The Past, the Present, and the Future.

An Individualized Approach to Treating Pups with Severe Hemophilia a: Which Factors Correlate with the Low Rate of Inhibitor Development?

▪Introduction:Development of inhibitors to replacement factor VIII (FVIII) remains a significant challenge to the management of previously untreated patients (PUPs) with severe hemophilia A. Although several determinants have been associated with the risk of inhibitor development, the impact of treatment approach remains controversial. Here we report our experience with an individualized approach to managing PUPs at a single hemophilia treatment center (HTC) in Germany.Methods:PUPs with severe hemophilia A (FVIII:C <1%) treated at the Gerinnungszentrum Rhein-Ruhr (GZRR), Germany, between January 2013 and June 2021 were followed prospectively. Our treatment approach includes early prophylactic physiotherapy, pdFVIIIconcentrate for at least the first 50 exposure days (EDs), tailored prophylaxis with individualized dose escalation according to bleeding tendency, and avoidance of prolonged on-demand treatment by avoiding treatment of minor bleeds or hematomas. Potential bleeds were examined by a hemophilia specialist and a decision made as whether to treat with pdFVIII based on the bleed location and severity. Ultrasound was performed every 3-6 months to check for joint bleeds. Where on-demand treatment was necessary, we used a high initial dose of 60-80 IU/kg with the aim of reducing the need for subsequent doses. Non-urgent surgical procedures were postponed and venous access system implants were avoided within the first 100 EDs. Inhibitor levels were measured using the modified Bethesda assay every 3-4 EDs until ED 100, and every 3 months thereafter for 2 years.Results:Data from 28 consecutive caucasian PUPs were collected. Fourteen (50%) patients had a F8 gene mutation associated with a high risk for inhibitor development. At the time of data cut-off 23 patients had received over 50 EDs of FVIII treatment, with 21 patients having over 100 EDs; the remaining patients had up to 45 EDs.Of the 28 patients, 27 started prophylaxis within the first 10 EDs. The initial prophylaxis schedule was tailored to each patient and ranged from 21 IU/kg every 10 days up to 40 IU/kg twice per week. One patient was treated on-demand for an intracranial bleed from ED 1-100. Only 3 spontaneous bleeds in 3 patients were treated; 25 patients (89%) remained free of spontaneous bleeds during prophylaxis. All three spontaneous bleeds were treated successfully with FVIII ± tranexamic acid. None of the 28 patients developed inhibitors.Discussion:Our approach to managing PUPs includes treatment with pdFVIII for at least the first 50 EDs, during which we treat bleeds only where necessary and use high doses to minimize further infusions. We had no cases of inhibitor development in our prospective cohort of 28 patients. In contrast, between 2003 and 2012, four of nine (44%) PUPs treated at our center developed inhibitors during the first 20 EDs, with two patients developing low-titer and two high-titer inhibitors. At that time we used recombinant FVIII (rFVIII) for prophylaxis in most patients and were less selective about which bleeds to treat with FVIII. Our individualized management approach, choice of pdFVIII and restricted use of FVIII for on-demand treatment therefore appear to correlate with a reduction in inhibitor incidence at our center. We usually switch patients from pdFVIII to rFVIII after at least 50 EDs due to the lower administration volume. Given the low rate of inhibitor development reported for PUPs treated with human cell line-derived rFVIII, there is a rationale to consider starting PUPs on human cell line-derived rFVIII.Conclusion:Our data support the position, that the use of an individualized management approach minimizes the risk of inhibitor development and raise important questions about how different aspects of treatment approach could impact outcomes in PUPs with severe hemophilia A. DisclosuresNo relevant conflicts of interest to declare.

Incidence of inhibitor development in PUPs with severe Haemophilia A in the CEE region between 2005 and 2015

IntroductionThis study analyses real-world data on 144 previously untreated patients (PUPs) with severe Haemophilia A, from seven countries in Central and Eastern Europe (CEE: Bulgaria, Croatia, Czech Republic, Hungary, Latvia, Serbia, and Slovenia), over a period of 11 years. It analyses the risk factors associated with development of inhibitors to factor VIII concentrates. MethodsCox proportional hazard models were used to estimate the hazard risk of factors possibly influencing the development of inhibitors. Patients were followed for up to 100 exposure days (EDs). ResultsCumulative inhibitor incidence at the time of 100 EDs was 18.7%, slightly lower than the 25–35% incidence reported in most studies. Of PUPs who developed inhibitors, a majority (56%) developed them within the first 20 EDs and 88% by the 50th ED. FVIII class (recombinant or plasma-derived) did not influence the inhibitors' incidence rate (p = 0.64). We found a significant protective effect of prophylaxis compared to on-demand treatment (p = 0.003). PUPs who had an intensive peak treatment during the first 50 EDs were at significantly higher risk for inhibitor development (HR (95% CI) 5.3 (2.3–12.5), p < 0.001). ConclusionInhibitors are and will continue to be the most significant complication of haemophilia treatment with factor concentrates. This is particularly true for haemophilia A. In our cohort, we were able to show that the treatment regimen used during first 50EDs influenced significantly the inhibitor risk, but the class of the factor concentrate did not play an important role. Real world data will remain one of the important resources for improving our knowledge of haemophilia.

The Un-BLyS-Ful State: Blocking Factor VIII Inhibitor Development with BLyS Depletion

The development of neutralizing alloantibodies (inhibitors) to infused factor VIII (FVIII) remains the most significant complication of therapy in hemophilia A (HA). Despite some insights into genetic and environmental risk factors associated with inhibitor development, the immunological mechanisms behind this complication remain incompletely understood. Given that infused FVIII is likely encountered in the periphery, transitional B cell response to FVIII may regulate inhibitor development. Transitional B cell survival, maturation and proliferation are tightly regulated by the cytokine BLyS (B-lymphocyte stimulator). Elevated levels of BLyS have been described in both auto- and allo-immune disease processes and may be genetically determined in a subset of patients with lupus and multiple sclerosis. In prior experiments, we noted that BLyS levels are higher in HA patients with inhibitors as opposed to 10 other pro- and anti-inflammatory cytokines. However, BLyS levels normalized amongst those who underwent successful immune tolerance induction. Thus, we hypothesized that BLyS may regulate FVIII inhibitor development or persistence. Here, we present results from animal studies aimed at 1) preventing inhibitor development in naïve HA mice and 2) maintaining long-term tolerance.For prevention experiments, HA C57Bl/6 mice (n=8-10/group) were given a single dose of anti-BLyS neutralizing antibody (Sandy-2, Adipogen) or PBS control one week prior to immunization with recombinant human FVIII (rhFVIII) at 80 IU/kg via tail vein injection every 14 days for four injections (Fig 1). Plasma samples were obtained at baseline and 7 days after last immunization and analyzed for FVIII antibody by Bethesda assay, anti-FVIII IgG by ELISA, and BLyS levels by ELISA. To test long-term tolerance, 22 weeks after initial anti-BLyS antibody injection, mice without inhibitors were challenged with 4 additional rhFVIII intravenous infusions and plasma obtained 7 days following each injection (Fig 1). Data was analyzed using Prism and is reported as median (IQR) with Mann-Whitney test for two-group comparisons and Mantel-Cox log-rank test for Kaplan-Meier survival analysis.Anti-BLyS treated mice achieved nadir BLyS levels at 14 days post-injection compared to control (0.2 [0.09-0.3] vs 8.2 [7.3-8.5] ng/ml, respectively, p < 0.0001), and levels equalized by day 28 between groups. Only 2 of 9 mice in the anti-BLyS treated group developed inhibitors to FVIII (0 [0-12.5] BU) compared to 9 of 10 in the treated group (21.1 [2.5-157.3] BU) with a significant log-rank survival of 0.0007 and favorable hazard ratio of 0.16 (95% CI 0.05-0.56) after initial immunization. Total anti-FVIII IgG was lower in the treated group (4.7 [1.1-11.5] mcg/ml) compared to control mice (27.6 [24-42] mcg/ml) with p of 0.003. Of the anti-BLyS treated inhibitor-free mice that have been challenged with rhFVIII, no inhibitors were detected until after the fourth rhFVIII injection. In these mice, there was a trend towards lower inhibitor titers compared to controls with a range of 1-1.8 BU vs. 85.6-1016 BU and lower FVIII IgG (23 [20.9-25.2] vs 69.9 [65.1-129.9] mcg/ml), respectively.Here, we demonstrate that BLyS depletion prior to FVIII exposure in naïve HA mice can prevent antibody development and may result in long-term sustained FVIII tolerance. As BLyS is central to the survival and maturation of transitional B cells, including marginal zone B cells which have recently been demonstrated to be important in inhibitor formation, this may provide a strategy for both antibody prevention and eradication in HA patients. Notably, the anti-BLyS monoclonal antibody belimumab is already FDA approved for the treatment of patients with lupus. Further studies to confirm the duration of immune tolerance obtained with anti-BLyS therapy in animal models may allow for translation of this strategy to provide long-lasting FVIII tolerance to patients with high risk of inhibitor development. [Display omitted] DisclosuresDoshi:Bayer Hemophilia Awards Program: Research Funding.

Timing and severity of inhibitor development in recombinant versus plasma‐derived factor VIII concentrates: a SIPPET analysis

Background The development of neutralizing antibodies (inhibitors) against factor VIII (FVIII) is the most severe complication in the early phases of treatment of severe hemophilia A. Recently, a randomized trial, the Survey of Inhibitors in Plasma-Product Exposed Toddlers (SIPPET) demonstrated a 2-fold higher risk of inhibitor development in children treated with recombinant FVIII (rFVIII) products than with plasma-derived FVIII (pdFVIII) during the first 50 exposure days (EDs). Objective/Methods In this post-hoc SIPPET analysis we evaluated the rate of inhibitor incidence over time by every 5 EDs (from 0 to 50 EDs) in patients treated with different classes of FVIII product, made possible by a frequent testing regime. Results The highest rate of inhibitor development occurred in the first 10 EDs, with a large contrast between rFVIII and pdFVIII during the first 5 EDs: hazard ratio 3.14 (95% confidence interval [CI], 1.01-9.74) for all inhibitors and 4.19 (95% CI, 1.18-14.8) for high-titer inhibitors. For patients treated with pdFVIII, the peak of inhibitor development occurred later (6-10 EDs) and lasted for a shorter time. Conclusion These results emphasize the high immunologic vulnerability of patients during the earliest exposure to FVIII concentrates, with the strongest response to recombinant FVIII products.

Genetic risk stratification to reduce inhibitor development in the early treatment of hemophilia A: a SIPPET analysis

AbstractA recent randomized trial, the Survey of Inhibitors in Plasma-Product Exposed Toddlers (SIPPET), showed a higher risk of inhibitor development with recombinant factor VIII (rFVIII) than plasma-derived concentrates (pdFVIII). We investigated whether risk stratification by F8 mutation identifies patients who do not suffer this deleterious effect of rFVIII. Among 235 randomized patients with severe hemophilia A previously untreated with FVIII concentrate, 197 with null mutations were classified as high risk and 38 with non-null mutations were classified as low risk. With pdFVIII, no inhibitors occurred in those with low genetic risk, whereas high-risk patients had a cumulative incidence of 31%. The risk among low- and high-risk patients did not differ much when they were treated with rFVIII (43% and 47%, respectively). This implies that patients with low genetic risk suffer disproportionate harm when treated with rFVIII (risk increment 43%), as also shown by the number needed to harm with rFVIII, which was 6.3 for genetically high-risk patients and only 2.3 for low-risk patients. Risk stratification by F8 mutation does not identify patients who can be safely treated with rFVIII, as relates to immunogenicity. This trial was registered at the European Clinical Trials Database (EudraCT) as #2009-011186-88 and at www.clinicaltrials.gov as #NCT01064284.

Concerns regarding clinical trials in haemophilia—Augmenting Iorio's “Research and policy implications of a recently published controlled study in previously untreated haemophilia patients at high risk of inhibitor development” Haemophilia (2017), 1‐3 https://doi.org/10.1111/hae.13176

Concerns regarding clinical trials in haemophilia—Augmenting Iorio's “Research and policy implications of a recently published controlled study in previously untreated haemophilia patients at high risk of inhibitor development” Haemophilia (2017), 1‐3 https://doi.org/10.1111/hae.13176

Research and policy implications of a recently published controlled study in previously untreated haemophilia patients at high risk of inhibitor development

HaemophiliaVolume 23, Issue 3 p. 350-352 Letter to the Editor Research and policy implications of a recently published controlled study in previously untreated haemophilia patients at high risk of inhibitor development A. Iorio, Corresponding Author A. Iorio iorioa@mcmaster.ca orcid.org/0000-0002-3331-8766 Health Research Methods, Evidence and Impact, McMaster University, Hamilton, ON, CanadaCorrespondence: Alfonso Iorio, Health Research Methods, Evidence, and Impact, McMaster University, 1280 Main Street West, Hamilton, ON, Canada, L8S 4K1. Tel.: +1 905 525 9140; fax: +1 905 577 8478; e-mails: iorioa@mcmaster.caSearch for more papers by this author A. Iorio, Corresponding Author A. Iorio iorioa@mcmaster.ca orcid.org/0000-0002-3331-8766 Health Research Methods, Evidence and Impact, McMaster University, Hamilton, ON, CanadaCorrespondence: Alfonso Iorio, Health Research Methods, Evidence, and Impact, McMaster University, 1280 Main Street West, Hamilton, ON, Canada, L8S 4K1. Tel.: +1 905 525 9140; fax: +1 905 577 8478; e-mails: iorioa@mcmaster.caSearch for more papers by this author First published: 20 February 2017 https://doi.org/10.1111/hae.13176Citations: 14Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article.Citing Literature Volume23, Issue3May 2017Pages 350-352 RelatedInformation

Genetic Risk Stratification to Minimize Inhibitor Risk with the Use of Recombinant Factor VIII Concentrates: A Sippet Analysis

▪BackgroundThe development of neutralizing antibodies against factor VIII is a common and serious complication of replacement therapy, occurring mainly in the early stages of treatment. Meta-analyses of observational studies have suggested a higher risk of inhibitor development with concentrates produced by recombinant technologies (rFVIII) than with those derived from human plasma (pdFVIII) containing von Willebrand factor, which was recently confirmed in a randomized trial. In this trial cumulative incidences of inhibitor development were 44.5% for rFVIII and 26.8% for pdFVIII, for a hazard ratio (HR) of 1.87 (95% confidence interval (CI95) 1.17-2.96). Given the particularly high risk with rFVIII , it has been suggested to restrict the use of rFVIII to low risk patients, and treat high-risk patients with pdFVIII. We investigated such a strategy in a post-hoc analysis of the SIPPET study, in which we used the FVIII genotype (F8 gene mutation) to classify patients by prior risk.MethodsSIPPET is an open label international randomized trial on which 251 previously untreated (n=142) or minimally treated (less than five exposure to blood components other than concentrate or cryoprecipitate, n=109) in 42 centers to be treated exclusively with a concentrate from the class of rFVIII or pdFVIII. Patients were tested for inhibitors before entry and at regular intervals during 50 exposure days, 3 years or the development of an inhibitor of at least 0.4 Bethesda units (BU). The trial ran from 2010 to 2014 and was terminated when the prespecified number of patients was included. Patients who had not reached 50ED by that time were censored. Patients were classified at high risk when they carried a null mutation (inversion, large deletion, frameshift, nonsense mutation) in the F8 gene and as low risk when they carried another causative variant (missense, splice site, polymorphisms, no mutation). We estimated cumulative incidences, hazard ratios and numbers needed to harm (NNH) for rFVIII vs pdFVIII for high- and low risk patients.ResultsAmong 251 patients, 76 developed an inhibitor (all > 0.7 BU) of which 50 were high- titer (> 5 BU). Among 197 patients classified as high risk, 65 developed an inhibitor (cumulative incidence 38.2%, CI95 30.8-45.6), whereas among the 38 patients classified as low risk 7 developed an inhibitor (cumulative incidence 23.9%, CI95 8.2-39.6). High and low risk patients were equally distributed over the two arms of the trial, i.e., 96 out of 126 treated with rFVIII were high risk, and 101 out of 125 treated with pdFVIII. Among high risk patients, cumulative incidence was 30.7% when treated with pdFVIII , and 46.5% when treated with rFVIII (risk difference 15.8%). Among low risk patients, no inhibitors developed with pdFVIII, whereas the cumulative incidence was 43.2% with rFVIII (risk difference 43.2%). This implies that the Number Needed to Harm was 5.6 overall, 6.3 for high-risk patients, and 2.3 in low risk patients.ConclusionRisk stratification by the type of F8 mutation does not identify previously untreated patients with hemophilia A who have a low inhibitor risk when exposed to rFVIII. Other means need to be found to reduce the occurrence of inhibitors with rFVIII. DisclosuresPalla:Pfizer: Other: travel support . Mannucci:NovoNordisk: Speakers Bureau; Kedrion: Speakers Bureau; Grifols: Speakers Bureau; Bayer: Speakers Bureau. Peyvandi:Bayer: Speakers Bureau; SOBI: Speakers Bureau; Kedrion Biopharma: Consultancy, Other: research funding paid to Luigi Villa Foundation, Research Funding; Alexion: Other: research funding paid to Luigi Villa Foundation, Research Funding; Octapharma: Consultancy; Ablynx: Membership on an entity's Board of Directors or advisory committees, Other: research funding paid to Luigi Villa Foundation, Research Funding; Biotest: Other: research funding paid to Luigi Villa Foundation, Research Funding, Speakers Bureau; CSL Behring: Speakers Bureau; LFB: Consultancy; Grifols: Speakers Bureau; Novo Nordisk: Other: research funding paid to Luigi Villa Foundation, Research Funding, Speakers Bureau.

Inhibitor Development in Previously Untreated Patients with Severe Hemophilia a Treated with Nuwiq®, a New Generation Recombinant FVIII of Human Origin

Inhibitor Development in Previously Untreated Patients with Severe Hemophilia a Treated with Nuwiq®, a New Generation Recombinant FVIII of Human Origin

NHF‐McMaster Guideline on Care Models for Haemophilia Management

This guideline was developed to identify evidence-based best practices in haemophilia care delivery, and discuss the range of care providers and services that are most important to optimize outcomes for persons with haemophilia (PWH) across the United States. The guideline was developed following specific methods described in detail in this supplement and based on the GRADE (Grading of Recommendations, Assessment, Development and Evaluation approach). Direct evidence from published literature and the haemophilia community, as well as indirect evidence from other chronic diseases, were reviewed, synthesized and applied to create evidence-based recommendations. The Guideline panel suggests that the integrated care model be used over non-integrated care models for PWH (conditional recommendation, moderate certainty in the evidence). For PWH with inhibitors and those at high risk for inhibitor development, the same recommendation was graded as strong, with moderate certainty in the evidence. The panel suggests that a haematologist, a specialized haemophilia nurse, a physical therapist, a social worker and round-the-clock access to a specialized coagulation laboratory be part of the integrated care team, over an integrated care team that does not include all of these components (conditional recommendation, very low certainty in the evidence). Based on available evidence, the integrated model of care in its current structure, is suggested for optimal care of PWH. There is a need for further appropriately designed studies that address unanswered questions about specific outcomes and the optimal structure of the integrated care delivery model in haemophilia.

Specific and global coagulation tests in patients with mild haemophilia A with a double mutation (Glu113Asp, Arg593Cys).

Heterogeneous bleeding phenotypes are observed in haemophilia A patients with the same mutation in the F8 gene. Specific mutations in the A2 domain of factor VIII are associated with mild haemophilia and a higher risk of inhibitor development. Double mutations in mild haemophilia A are rarely reported. In this study, we investigated the in vitro function of factor VIII, performing different specific and global coagulation assays, observed clinical characteristics and assessed the possible predictive diagnostic value of the differences. The clinical features of haemophiliacs with a mild phenotype were reviewed. Blood samples were obtained and analysed for mutations and coagulation assays: activated partial thromboplastin time, one-stage and chromogenic factor VIII activity, factor VIII antigen and rotational thromboelastometry. We report on a cohort of 22 patients with double Glu113Asp, Arg593Cys mutations. All our patients have a quantitative defect of factor VIII and preserved similar functional activity. Factor VIII activities measured by the one-stage or chromogenic method were not discrepant, although the chromogenic assay resulted in 20% lower factor VIII activities. Waveform analysis showed a lower maximum value of the second derivative curve (Max2) of APTT with curve shape alternation, while thromboelastometry (INTEM) showed low sensitivity in comparison to results in a normal population. In genotyping, the coexistence of a second mutation should never be excluded, especially in cases of discordant clinical presentation. Waveform analysis correlates better with factor VIII activity than thromboelastometry and the Max2 parameter could provide additional information in managing haemophilia patients. The utility of specific factor activity and global haemostatic assays in general practice still needs to be investigated.

Evaluation of safety and effectiveness of factor VIII treatment in haemophilia A patients with low titre inhibitors or a personal history of inhibitor. Patient Data Meta-analysis of rAFH-PFM Post-Authorization Safety Studies.

There is no prospective evidence on inhibitor recurrence among haemophilia A patients with low titre inhibitors or history of inhibitors, and whether or how therapeutic choices affect the risk of recurrence. The aims of this study were to synthesise safety data in patients with moderate-severe haemophilia A and with low titre inhibitors or inhibitor history enrolled in the rAHF PFM (ADVATE) - Post-Authorization Safety Studies (ADVATE-PASS) international programme. The study was conducted in clinics participating to the ADVATE PASS programme. The patient population consisted of patients entering the studies with low titre (≤ 5 BU) inhibitors or a positive personal history of inhibitors. Patients on Immune Tolerance Induction at study entry were excluded. Primary outcome was new or recurrent inhibitor titre > 5 BU. Secondary outcomes were any increase of inhibitor titre not reaching 5 BU; any unexplained change in treatment regimen. Primary analysis was done by two-stage random effects meta-analysis. Secondary analysis was done by a hierarchical Bayesian random effects logistic model. A total of 219 patients from seven studies were included. Of these 214 (97.7 %) patients had been previously treated for more than 50 exposure days. Two hundred ten patients had positive history for inhibitors, nine a baseline measurable titre. No patient presented a primary outcome event (95 % confidence interval [CI] 0-1.6 %). Six patients with previous history developed a low titre recurrence (overall rate 2.2, 95 %CI 0-4.8 %). When any increase of inhibitor titre or any treatment change was accounted for, overall 3.7 % (95 % CI 0 %-8.0 %) of patients experienced the outcome. In conclusion, the observed rate of events does not support the definition of this population as at high risk for inhibitor development.

Recombinant factor VIII products and inhibitor development in previously untreated boys with severe hemophilia A

AbstractSix recombinant factor VIII (rFVIII) products have been marketed worldwide. In 2013, the Research of Determinants of Inhibitor Development (RODIN) study group reported an unexpectedly high risk of inhibitor development with a second-generation full-length rFVIII (Product D) in previously untreated patients (PUPs) with severe hemophilia A (HA). In 1994, French public health authorities established a prospective cohort to monitor hemophilia treatment safety. A PUP subgroup was designed to investigate inhibitor risk factors. We analyzed this subcohort in view of the RODIN findings. After excluding 50 patients who participated in the RODIN study, the primary analysis focused on 303 boys with severe HA first treated with a rFVIII product. A clinically significant inhibitor was detected in 114 boys (37.6%). The inhibitor incidence was higher with Product D vs the most widely used rFVIII product (adjusted hazard ratio [aHR], 1.55; 95% confidence interval [CI], 0.97-2.49). Similar results were found for high-titer inhibitors and in 10 sensitivity analyses. No heterogeneity was observed between RODIN and our results. Combined aHRs were 1.58 (95% CI, 1.17-2.14) for all inhibitors and 1.70 (95% CI, 1.15-2.52) for high-titer inhibitors. Our results confirm the higher immunogenicity of Product D vs other rFVIII products in PUPs with severe HA.

Analysis of F8 inversions as risk factors for FVIII inhibitor development in Indian severe haemophilia A patients.

FVIII inhibitor development in haemophilia A (HA) patients, especially those with severe manifestations is a serious adverse effect in patients with haemophilia A, and the clinical management of these patients is very difficult as most don't respond to conventional treatment. Many genetic and non-genetic risk factors have been proposed however, these are diverse in different population groups, highlighting the importance of determining specific risk factors for each population. F8 mutations and especially inversions, which are the most common causative mutation in severe HA, have been significantly associated with inhibitor development earlier, however there is no conclusive data so far with regard to Indian haemophiliacs. This study provides novel evidence that intron 22 inversions in the F8 gene are indeed significantly associated with FVIII inhibitor development in Indian haemophiliacs. Further studies with other risk factors would enable better insights into the immune response towards FVIII in these patients, and possibly help to characterize patients at a higher risk for inhibitor development.

The Rodin (Research Of Determinants of INhibitor Development among PUPs with haemophilia) study: the clinical conundrum from the perspective of haemophilia treaters

The Rodin study, recently published in the New England Journal of Medicine, has begun to provide some very important answers to several questions pertinent to the quality and safety of replacement therapy to individuals with haemophilia [1]. Probably the most serious complication of modern haemophilia care is currently the development of alloantibody neutralizing inhibitors and considerable recent literature until the Rodin trial had speculated that the recombinant factor (rFVIII) replacement products were more likely than the plasma-derived products to produce this. The Rodin trial has extended our thoughts on this issue because it is a robustly populated prospective observational study, in contrast to previously published results, which have been generated from smaller, retrospective, mostly uncontrolled heterogeneous population studies. Based on the results of 574 previously untreated severe haemophilia A patients (FVIII activity, <0.01 IU mL ), the observations in Rodin indicated that there was no difference in the incidence of alloantibody inhibitors whether patients received plasma-derived or recombinant full-length FVIII products (adjusted hazards ratio = 0.96). Furthermore, among those who developed alloantibody inhibitors while on plasma-derived FVIII concentrates, the content of von Willebrand factor (VWF) did not influence the risk of inhibitor formation (adjusted hazards ratio = 0.90). Lastly, the Rodin population study indicated that switching from a plasma-derived FVIII product (irrespective of relative VWF content) to a full-length rFVIII product did not increase the risk of inhibitor development. These conclusions are extremely cogent to patients and their physicians alike as the possibility that rFVIII products were more immunogenic, that the high content of VWF protein in plasma-derived FVIII products could protect against alloantibody formation, and that product switching would be harmful all were used as rationale to determine the choice of replacement product for previously untreated, slightly previously treated, and even those previously treated individuals with over 150 exposure days. This published report notwithstanding the possibility that it may be underpowered to conduct most of the above comparisons due to the relatively low number of patients treated with plasma-derived molecules has added to the cumulative published data, which tend to discount these concerns when determining product choice for previously untreated patients (PUPs) and others. In fact, several of the haemophilia treaters and haemophilia treatment centres (HTC), who participated in Rodin, had expressed publicly prior to this publication that these same concerns influenced their decision to initiate their PUPs considered at higher risk for inhibitor development on plasma-derived products. The Rodin trial was observational, that is NOT a randomized controlled study, and allowed each HTC to determine independently how it was to treat its PUPs. This approach could have led to an imbalance in the baseline prognostic characteristics of the groups being compared in Rodin and this potential bias could have introduced a significant biostatical flaw into the study design [2].

Common SNPs within or near Three Immune Response Genes Implicated in the Risk of FVIII Immunogenicity in Hemophilia A Do Not Influence Steady-State Levels of Their Encoded mRNAs

AbstractAbstract 3366 Background/Aims:The hemophilia A (HA)-causing Factor (F)VIII gene (F8) mutation type is a well-established determinant of risk for the development of alloimmune inhibitors that neutralize replacement FVIII proteins in ∼20% of all HA patients. Studies have investigated variants of immune response genes to determine if they may account for the inter-individual variability in FVIII immunogenicity observed in patients with the same F8 abnormality, e.g., the intron-22 inversion. While some studies have found associations between inhibitor status and promoter polymorphisms in CTLA4, TNFA and/or IL10, others have not. If these promoter polymorphisms are indeed functional and truly influence inhibitor development, their alleles could modulate transcription initiation rates. The goal of this study was to investigate the possibility of cis-acting genotype-specific differences in mean steady-state mRNA levels encoded by CTLA4, TNFA and IL10. Methods:We examined the relationship of lymphocyte CTLA4, TNFA and IL10 mRNA levels with the genotypes of 265 SNPs located across their structural loci in 1189 Mexican American subjects in the San Antonio Family Heart Study. Expression profiles were generated using Illumina’s HWG-6 BeadChips and genotypes came from the Illumina OmniExpress-12 BeadChip. Measured genotype association analyses that accounted for non-independence of family members and employed an additive model (in which testing to determine whether gene expression varies by genotype, with the model constrained so that each “dose” of the minor allele raises or lowers gene expression by an equal amount “beta”) were performed using the software package SOLAR. P-values were calculated using a 1 degree-of-freedom chi-square test comparing the likelihood of a model where the change in expression levels by genotype is estimated to the likelihood of a model where beta is constrained to zero. Results:None of the 265 genotyped SNPs within or near these three genes (i.e., 49 SNPs in IL10, 35 SNPs in CTLA4 & 181 SNPs in TNFA) function as cis-acting regulatory variants, as no significant genotype-specific associations with these genes’ transcript levels were identified. Conclusions:We observed no evidence for cis-regulation of CTLA4, TNFA or IL10 in Mexican Americans, the largest and most rapidly growing minority population in the United States, despite having genotyped directly the previously implicated promoter polymorphisms in the current analysis (e.g., see Figure). Although Hispanic American HA patients were recently found to have a significantly higher risk for inhibitor development than White HA patients, it is possible that cis-acting functional variants in this minority population are rare and not well-represented by the common GWAS SNPs used for these analyses. Since linkage disequilibrium patterns between markers are population-specific, we are also currently genotyping these SNPs in a large cohort of African and Caucasian American HA patients. [Display omitted] Disclosures:No relevant conflicts of interest to declare.

Prevention and prediction of inhibitor risk

Studies of determinants of the development of inhibitory antibodies in patients with haemophilia indicate that this is a complex process involving several factors. The foundation is characterized by the T- and B-cell repertoire and the antigen presenting cells and to elicit an immune response to the deficient factor, a pre-disposing foundation is needed. Hence, in the absence of a certain set of circumstances, there will be no risk for development of inhibitors. Conversely, in patients fundamentally at risk, genetic and non-genetic factors might add to the risk. These factors may be additive or interactive, and ultimately promote or counteract the immune reaction by modifying immune regulators and the cytokine profile in an individual. In some subjects, only minor inflammatory signals might be needed, whereas in others a more pronounced pro-inflammatory state will be required. Regarding genetic markers other than the type of mutation and the HLA class II molecules, polymorphisms in various immune regulatory genes have been associated with inhibitor risk. These associations have not, however, been consistent across all patient groups. The reason for this is not clear, but could be related to study design or statistical power, family relationships among those studied, the complexity of interacting molecules and ethnic genomic variation. The Hemophilia Inhibitor Genetics Study (HIGS) has identified additional candidates within the intracellular pathways, all of which require additional evaluation to be fully appreciated. In the case of non-genetic factors, the overall view is that immune system challenges might add to the risk. HIGS data suggest that it will be possible to calculate a genetic score to identify patients at high risk for inhibitor development before the start of treatment. By doing so, it may hopefully be possible in the future to prevent the formation of inhibitors in these patients by offering therapeutic options other than the native factor VIII or IX molecule in an inflammatory setting.

Experience of Advate rAHF-PFM in previously untreated patients and minimally treated patients with haemophilia A

Summary We report a prospective trial of 55 previously untreated patients (PUPs) and minimally treated patients (MTPs) with severe/moderately severe haemophilia A (baseline factor VIII [FVIII] ≤2%) treated with a single FVIII replacement product. It was the objective of this study to evaluate the immunogenicity, efficacy, and safety of rAHF-PFM (Advate ® ). Ondemand or prophylactic treatment regimens were determined at the discretion of the investigator. rAHF-PFM was also permitted for perioperative management. There were 633 bleeding episodes (BEs), including 517 treated, and 466 rated for efficacy. Haemostatic efficacy was considered excellent/good in 93% of 466 rated treatments. Of 517 treated BEs, 463/517 (90%) were managed with one (356/517 [69%]) or two infusions (107/517 [21%]). There were 27 surgeries. Intraoperative (n=22) and postoperative (n=25) haemostatic efficacies were considered excellent or good in 100% of rated surgeries. Related serious adverse events (SAEs) were inhibitor development in 16/55 (29.1%) subjects who received at least one infusion of rAHF-PFM. Nonserious, related adverse events (AEs) were few in number (14 in eight subjects). The odds ratio (OR [95% Confidence Interval, CI]) of developing inhibitors was significantly higher in subjects with a family history of inhibitor (4.95 [1.29–19.06]), non-Caucasian ethnicity (4.18, [1.18–14.82]), and intensive treatment at high dose (4.5 [1.05–19.25]) within ≤20 exposure days (EDs). In conclusion, rAHF-PFM was safe and effective for the management and perioperative coverage of PUPs/MTPs with severe/moderately severe haemophilia A. This report supports previous findings from studies in which family history of inhibitor, non-Caucasian ethnicity, and high intensity treatment were associated with high risk of inhibitor development.