The management of inhibitors in haemophilia A: introduction and systematic review of current practice

Budget impact analysis of Jivi (damoctocog alfa pegol, Bay 94-9027) in severe hemophilia A in Japan

OBJECTIVE

Hemophilia A (HA) is a genetic bleeding disorder characterized by a deficiency of clotting factor VIII (FVIII) requiring lifelong prophylactic treatment typically with conventional standard half-life recombinant FVIII (rFVIII). Lifelong prophylaxis impacts budget, patient adherence, and long-term outcomes. The consequent economic and treatment burden may be reduced by using novel extended half-life rFVIII. The objective of this analysis was to estimate the budget impact of introducing Jivi (damoctocog alfa pegol, BAY 94-9027), hereafter referred to as BAY 94-9027, as an on-demand and prophylactic treatment for severe HA from a Japanese payer's perspective.

METHODS

A global budget impact model was adapted to the Japanese setting using data obtained via a targeted literature review of Japanese sources. The model considered a five-year time horizon for a market without and with BAY 94-9027. Using annual per-patient costs, the total cost of on-demand and prophylactic treatment of adolescent and adult patients with severe HA (without inhibitors) were analyzed. The model used summary of product characteristics (SmPC) and clinical trial dosing, and unit costs from the National Health Insurance (NHI) drug price database. Comparators considered in the model comprised of currently available products in Japan. Projected BAY 94-9027 uptake ranged from 4% to 9% over the five years (2020-2024).

RESULTS

Introduction of BAY 94-9027 for the treatment of severe HA is estimated to decrease the overall budget by 1.5%, with a cost saving of approximately $67 million USD (¥7.4 billion JPY) over five years. Estimated cost savings associated with BAY 94-9027 ranged from $1.4 million USD (¥156 million JPY) in 2020 to $23 million USD (¥2.6 billion JPY) in 2024 for the Japanese healthcare system.

LIMITATIONS

There were limitations associated with the study. The Japanese guidelines consulted during the targeted literature review of national data sources in Japan were based on global data as reference sources. Also, studies reporting the bleeding rate, dosing guidelines, and economic burden in the Japanese population identified by the targeted literature review were limited hence global studies were used and may not have been representative of the Japanese population.

CONCLUSIONS

BAY 94-9027 can reduce total severe HA treatment costs, driven by lower annual rFVIII utilization, and a narrow weekly dosing range compared to competitor products in the Japanese market.

Haemophilia A: health and economic burden of a rare disease in Portugal

BACKGROUND

Haemophilia A is a hereditary bleeding disorder, which has been considered rare and chronic. The burden of this disease in Portugal remains unknown. The aim of this study was to estimate the annualized cost and health burden of haemophilia A in Portugal.

METHODS

Data were extracted from a Portuguese expert panel, from official data and national literature. Annual costs were calculated from the perspective of the society including direct and indirect costs. Unitary costs were extracted from 2017 national official sources and are expressed in euros. Health burden was expressed in disability adjusted life years (DALYs) based on incidence and quality of life questionnaires. Estimates are presented for the overall population and stratified by severity, age group (< 18 years vs. adults) and inhibitor status.

RESULTS

The yearly average cost per patient is estimated to range from €39,654/patient without inhibitors and €302,189/patient with inhibitors, representing a 7.6 fold difference. Amongst patients without inhibitors, the annual average cost was €401 in mild, €5327 in moderate and €85,805 in severe disease. Average cost per child and adult is €72,287 and €51,737, respectively. Direct costs represent approximately 95% of all costs, of which almost the totality accounts for clotting factor replacement therapy and bypassing agents. The total annual cost of haemophilia A for the Portuguese society was estimated to be €42,66 million, one third of which was related to the treatment of patients with inhibitors. It is estimated that haemophilia A is responsible for 3878 DALYs in Portugal (497 DALYs in mild, 524 DALYs in moderate, 2031 DALYs in severe patients without inhibitors and 784 DALYs in patients with inhibitors) for the cohort of 2017 (750 patients) or 5.2 DALY/patient during lifetime.

CONCLUSIONS

Despite being rare, the economic and health burden of haemophilia A is remarkable. The main cost driver is clotting factor replacement therapy. Moreover, haemophilia A is more costly in children than in adults and rises exponentially with disease severity.

Impact of the Survey of Inhibitors in Plasma-Product Exposed Toddlers (SIPPET) study and its post hoc analyses on clinical practice in the United States: A survey of Haemophilia and Thrombosis Research Society members

INTRODUCTION

A recent randomized trial, the Survey of Inhibitors in Plasma-Product Exposed Toddlers (SIPPET), confirmed that exposure to recombinant FVIII (rFVIII) products doubled the risk of inhibitor development compared to plasma-derived FVIII (pdFVIII) in previously untreated (or minimally treated) patients (PUPs) with severe haemophilia A. SIPPET post hoc analyses showed that early exposure to rFVIII was more immunogenic and that rFVIII could harm low-risk PUPs with non-null mutations. Clinical implications of SIPPET findings for the haemophilia community were unclear.

AIM

Study the impact of the SIPPET study and its post hoc analyses on clinical practice for PUPs with severe haemophilia A in the United States.

METHODS

Members of the North American Hemophilia and Thrombosis Research Society (HTRS) completed two online questionnaires related to SIPPET publications and PUP management (study period: 12/2016-8/2018).

RESULTS

Over 50% participated the study. Sixty per cent expressed methodological concerns about the SIPPET study, yet 55% shared the study with new families. During the study period, rFVIII selection fell from 43/61 (70%) to 15/54 (28%) while use of pdFVIII and shared decision-making increased from 5/61 (8%) to 9/54 (17%) and from 4/61 (7%) to 10/54 (19%), respectively. Based on post hoc analyses, 44/54 (82%) would change their clinical practice with 31/44 (70%) using pdFVIII for PUPs. Barriers to translation of SIPPET analyses included study design concerns, non-inclusion of novel therapies, inability to perform genetic testing at diagnosis and risk of plasma-derived infections.

CONCLUSION

Despite the methodological concerns about the SIPPET study, this Grade I evidence appears to have influenced the clinical practice of haemophilia providers in the United States.

Costs and utilization of treatment in patients with hemophilia

Background

Although hemophilia has a potentially high economic impact, there are no published estimates of healthcare costs for this disease in Portugal. The aim of this study was to evaluate costs of treatment and hospital utilization among patients with hemophilia A and B, with and without inhibitors, over a 3-year period in a Portuguese Comprehensive Care Hemophilia Centre. This is the first study on the financial impact of healthcare costs in patients with hemophilia in Portugal.

Methods

This retrospective, observational study identified patients diagnosed with hemophilia A and B using medical and pharmacy electronic medical records and data from Centro Hospitalar São João, between January 2011 and December 2013. Patients with inhibitors were all high responders (>5 Bethesda Units [BU]). Severity was classified as mild, moderate or severe based on clotting factor levels. Two main outcomes were measured: (1) cost associated with hospital pharmacy claims (clotting factor) and (2) number of hospital visits/hospitalization.

Results

A cohort of 103 patients were identified: 72 (69.9 %) with hemophilia A and 31 (30.1 %) with hemophilia B. Among these, five individuals were classified as patients with inhibitors (four with hemophilia A and one with hemophilia B). From the cohort of hemophilia A patients, 36 individuals (35.0 %) were identified as having severe disease; 20 (19.4 %) moderate; and 16 (15.5 %) mild. In the cohort of hemophilia B patients, 14 (13.6 %) were identified as having severe disease; 14 (13.6 %) moderate; and three (2.9 %) mild. The total mean aggregate cost per year (including clotting factor and hospital utilization) for patients with severe hemophilia B was €112,469, compared with €793 for mild hemophilia A. Clotting factor concentrate amounted for 90 % of total cost in severe cases and hospital utilization was also higher in these cases.

Conclusions

Hemophilia treatment is expensive, particularly for patients with severe disease and especially if they develop inhibitors to replacement clotting factors. In our study, severe hemophilia is associated with greater annual total costs in both types of hemophilia (A = €77,587 and B = € 112,469). Patients with inhibitors have costs 3.3 times higher than patients without inhibitors. Age was not associated with significantly greater total costs (clotting factor and hospital visits/hospitalizations).

Risk factors for high-titer inhibitor development in children with hemophilia A: results of a cohort study

Among the discussed risk factors for high-titre inhibitor (HRI) development in patients with hemophilia A (HA) are high dose FVIII replacement therapy and use of recombinant FVIII concentrates (rFVIII). The aim of this study was to evaluate the aforementioned risk factors for HRI development in children with hemophilia A ≤2%. About 288 ascertained PUPs (Israel and Germany) were followed after initial HA diagnosis over 200 exposure days. Inhibitor-free survival, hazard ratios (HR), and 95% confidence intervals (CIs) were calculated. Adjustment was performed for factor VIII concentrates, median single dose over the first three months of treatment, first FVIII administration before the age of three months, presence of risk HA gene mutations, "intensive treatment moments" and "year of birth" (proxy for different treatment periods). HRI occurred in 71/288 children (24.7%). In multivariate analysis adjusted for "year of birth", underlying risk gene mutations (HR/CI: 2.37/1.40-3.99), FVIII dose, measured per one IU increase per kgbw (HR/CI: 1.05/1.04-1.07), and first FVIII administration before the age of three months showed a significant impact on HR development. The risk of HRI development was similar for recombinant or plasmatic FVIII products. Children at risk should be treated with carefully calculated lower dose regimens, adapted to individual bleeding situations.

Impact of HLA alleles and cytokine polymorphisms on inhibitors development in children with severe haemophilia A

Human Leucocyte Antigen (HLA) alleles, cytokine polymorphisms and the type of factor VIII (FVIII) gene mutation are among predisposing factors for inhibitors (inh) development in children with severe haemophilia A (HA). The aim was to investigate the correlations among (i) FVIII gene intron-22 inversion, (ii) HLA alleles and haplotypes and (iii) certain cytokine polymorphisms, with the risk for FVIII inhibitors development in 52 Greek severe HA children, exclusively treated with recombinant concentrates. We performed Long-Range PCR for detection of intron-22 inversion and PCR-SSP, PCR-SSO for genotyping of HLA-A, B, C, DRB1, DQB1 alleles and also for cytokine polymorphisms of TNF-α, TGF-β1, IL-10, IL-6 and IFN-γ. Chi-squared test and Fischer's exact test were used for statistical analysis. A total of 28 children had developed inhibitors (Group I), 71.4% high responding, while 24 had not (Group II). No statistically increased intron-22 inversion prevalence was found in Group I compared with Group II (P = 0.5). Comparison of HLA allele frequencies between the two groups showed statistically significant differences in the following genotypes (i) promoting inhibitors development: DRB1*01(P = 0.014), DRB1*01:01(P = 0.011) and DQB1*05:01 (P = 0.005) and (ii) possibly protecting from inhibitors development: DRB1*11 (P = 0.011), DRB1*11:01 (P = 0.031), DQB1*03 (P = 0.004) and DQB1*03:01 (P = 0.014). Analysis of cytokines revealed a higher incidence of inhibitor detection only in homozygotes of the haplotypes ACC and ATA for IL-10 polymorphisms (P = 0.05). There is evidence that HLA alleles and cytokine polymorphisms play an important role in FVIII inh development. On the contrary, no statistically significant results were obtained for intron-22 inversion and its impact on FVIII inhibitors formation.

Immune tolerance induction therapy for patients with hemophilia A and FVIII inhibitors particularly using low-dose regimens

BACKGROUND

Inhibitory antibodies against infused clotting factor VIII concentrates (FVIII) developed in 20-30% of patients with hemophilia A. Bypass therapy may control the bleeds in patients with FVIII inhibitors, however, immune tolerance induction (ITI) therapy is the only proven modality for eradicating FVIII inhibitors. Since the cost of high-dose (200 IU/kg) ITI is extremely expansive, we conducted this study to identify whether low-dose ITI can be an alternative strategy besides high-dose ITI or bypass therapy.

PROCEDURE

Patients with hemophilia A and FVIII inhibitors treated by ITI in Kaohsiung Medical University Hospital from January 2000 to January 2010 were enrolled. Regimens of ITI therapy included high-dose (100 IU/kg) and low-dose (30-50 IU/kg).

RESULTS

High-dose ITI therapy for two high responders (HRs) and low-dose ITI therapy for three HRs and all low responders (LRs) were performed. Complete tolerance was achieved in 2 HRs with high-dose regimen, and in one HR and 19 LRs with low-dose regimens. We administered low-dose ITI combined with immune suppressants treatment for one of the patient with extremely high FVIII inhibitor titers and the inhibitor level markedly declined and no spontaneous bleeding episode was noticed during the treatment period.

CONCLUSIONS

The outcome of ITI in our study was satisfactory without clinically significant complications. Low-dose ITI regimens can effectively treat patients with high responder inhibitors, including one patient with extremely high inhibitor levels over 700 BU. Low-dose ITI may be an alternative modality for FVIII inhibitors management, especially in countries with limited resources.

Can B-domain deletion alter the immunogenicity of recombinant factor VIII? A meta-analysis of prospective clinical studies

BACKGROUND

As a result of the infrequency of inhibitors in previously treated patients (PTPs) with hemophilia A and the small size of available clinical studies, the immunogenicity of factor (F)VIII products has been difficult to assess.

OBJECTIVES

A meta-analysis of prospective clinical studies was conducted to test the hypothesis that de novo inhibitor incidence differs between PTPs receiving full-length recombinant FVIII (FL-rFVIII) and B-domain deleted recombinant FVIII (BDD-rFVIII).

METHODS

Prospective studies with data on inhibitors in PTPs receiving FL-rFVIII or BDD-rFVIII were sought using systematic methods including bibliographic database searches. Data were secured from published study reports and inquiries to investigators. Between-group differences in inhibitor incidence rates were evaluated using mixed effects Cox regression.

RESULTS

Twenty-nine studies with 3012 total PTPs were included. Patients were at risk of de novo inhibitor development for a median of 79 exposure days. A total of 35 de novo inhibitors were observed. The cumulative hazard for all de novo inhibitors was 1.25% with a 95% confidence interval (CI) of 0.63-1.88%. The corresponding rate for high-titer de novo inhibitors [> 5 Bethesda units (BU)] was 0.29% (CI, 0.01-0.57%). Exposure to BDD-rFVIII was associated with an increased risk of all de novo inhibitors (hazard ratio, 7.26; CI, 2.12-24.9; P = 0.0016) and of high-titer de novo inhibitors (hazard ratio, 10.8; CI, 2.17-53.7; P = 0.0037), compared with FL-rFVIII.

CONCLUSIONS

This meta-analysis of prospective clinical studies suggests that recombinant FVIII products may differ in immunogenicity.

Treatment of hemophilia: a review of current advances and ongoing issues

Replacement of the congenitally deficient factor VIII or IX through plasma-derived or recombinant concentrates is the mainstay of treatment for hemophilia. Concentrate infusions when hemorrhages occur typically in joint and muscles (on-demand treatment) is able to resolve bleeding, but does not prevent the progressive joint deterioration leading to crippling hemophilic arthropathy. Therefore, primary prophylaxis, ie, regular infusion of concentrates started after the first joint bleed and/or before the age of two years, is now recognized as first-line treatment in children with severe hemophilia. Secondary prophylaxis, whenever started, aims to avoid (or delay) the progression of arthropathy and improve patient quality of life. Interestingly, recent data suggest a role for early prophylaxis also in preventing development of inhibitors, the most serious complication of treatment in hemophilia, in which multiple genetic and environmental factors may be involved. Treatment of bleeds in patients with inhibitors requires bypassing agents (activated prothrombin complex concentrates, recombinant factor VIIa). However, eradication of inhibitors by induction of immune tolerance should be the first choice for patients with recent onset inhibitors. The wide availability of safe factor concentrates and programs for comprehensive care has now resulted in highly satisfactory treatment of hemophilia patients in developed countries. Unfortunately, this is not true for more than two-thirds of persons with hemophilia, who live in developing countries.

Cost of care of haemophilia with inhibitors

In Western countries, the treatment of patients with inhibitors is presently the most challenging and serious issue in haemophilia management, direct costs of clotting factor concentrates accounting for >98% of the highest economic burden absorbed for the healthcare of patients in this setting. Being designed to address questions of resource allocation and effectiveness, decision models are the golden standard to reliably assess the overall economic implications of haemophilia with inhibitors in terms of mortality, bleeding-related morbidity, and severity of arthropathy. However, presently, most data analyses stem from retrospective short-term evaluations, that only allow for the analysis of direct health costs. In the setting of chronic diseases, the cost-utility analysis, that takes into account the beneficial effects of a given treatment/healthcare intervention in terms of health-related quality of life, is likely to be the most appropriate approach. To calculate net benefits, the quality adjusted life year, that significantly reflects such health gain, has to be compared with specific economic impacts. Differences in data sources, in medical practice and/or in healthcare systems and costs, imply that most current pharmacoeconomic analyses are confined to a narrow healthcare payer perspective. Long-term/lifetime prospective or observational studies, devoted to a careful definition of when to start a treatment; of regimens (dose and type of product) to employ, and of inhibitor population (children/adults, low-responding/high responding inhibitors) to study, are thus urgently needed to allow for newer insights, based on reliable data sources into resource allocation, effectiveness and cost-utility analysis in the treatment of haemophiliacs with inhibitors.

Quantitation of anti-factor VIII antibodies in human plasma

The presence of antibodies (Abs) in hemophilia A patients can potentially influence the therapeutic qualities of factor VIII (fVIII) administration. Much work has been focused on the presence of inhibitory antibodies, whereas the quantitation of noninhibitory anti-fVIII antibodies has been largely undetermined. Our objective was to develop a sensitive and specific fluorescence-based immunoassay (FLI) for the quantitation of anti-fVIIIAbs in human plasma. Affinity-purified human anti-fVIIIAb, isolated from a hemophilia A subject, was used as a calibrator with a detectability limit of 40 (+/-1.5) pM. The calibrator and the human plasma anti-fVIIIAb were captured on recombinant fVIII (rfVIII)- coupled microspheres and probed with mouse anti-human Ig-R-phycoerythrin. Plasma samples from 150 healthy donors and 39 inhibitor-negative hemophilia A subjects were compared with 4 inhibitor-positive hemophilia A plasma samples with inhibitor titers of 1 BU/mL (94.6 +/- 0.8 nM), 11 BU/mL (214.3 +/- 7.1 nM), 106 BU/mL (2209.4 +/- 84.9 nM), 140 BU/mL (2417.7 +/- 3.8 nM) as measured by the Nijmegen method. We also describe the validation of a mouse anti-human fVIIIAb as a surrogate calibrator. Four healthy individuals (3%) showed detectable anti-fVIIIAb in the range of 0.6 to 6.2 nM, whereas 13 (33%) of the 39 inhibitor-free hemophilia A subjects were positive for anti-fVIIIAb in the range of 0.5 to 20 nM. The method may be useful for therapeutic management of hemophilia A patients.

Long-term consequences of intracranial haemorrhage in children with haemophilia

Intracranial haemorrhages (ICH) in children with haemophilia are rare, and the outcome is variable, ranging from no apparent impairment to death. The aim of this investigation was to identify if children with haemophilia and ICH, have any long-term problems with motor function, visual motor integration or strengths and difficulties compared with a control group. A review of the Haemophilia Database at Great Ormond Street Hospital for Children NHS Trust was undertaken to identify boys with haemophilia and a history of ICH, as well as a control group of peers with no such history. Boys were born between January 1994 and December 2002. All boys were assessed using the movement Assessment Battery for Children, the Developmental Test of Visual Motor Integration and The Strengths and Difficulties Questionnaire as standardized assessments of motor competence, visual motor integration and behavioural difficulties. Six boys with haemophilia and ICH and 11 controls (mean age: 7 years; range: 4-12 years) were assessed. Children with ICH were significantly more likely to have problems with motor function and visual motor integration (Fisher's exact: P < 0.05). In addition, they had a tendency towards more problems with strengths and difficulties than their peer group (Fisher's exact: P = 0.06). Five of the six boys who had sustained an ICH were in mainstream schools; four requiring assistance with their education. The results of this small study suggest that ICH may signify long-term consequences for boys with haemophilia. The multidisciplinary team need to be aware of the rare but potentially important impact on motor function, visual motor integration and behaviour, which may inhibit the child from functioning optimally. An agreed comprehensive battery of assessments in collaboration with schools and healthcare workers is required to identify impairments to enable prompt interventions to be co-ordinated.

Assessment of in vitro cytokine response in hemophilia A patients with or without factor VIII inhibitory antibody

Factor VIII (FVIII) inhibitor antibodies are produced in a proportion of hemophilia A patients. Development of anti-FVIII inhibitor antibodies is a T cell-dependent response, mediated by FVIII specific CD4(+) T cells. This study was performed to investigate the contribution of T helper (Th) cell-mediated cytokine response in inhibitor production. Peripheral blood mononuclear cells (PBMCs) were obtained from hemophilia A patients with (n = 14) or without inhibitor (n = 14) and from normal individuals (n = 14). Following stimulation of PBMCs with rFVIII and phytohemagglutinin (PHA) mitogen, the secreted cytokines, interferon-gamma (IFN-gamma), interleukin-10 (IL-10), and transforming growth factor-beta1 (TGF-beta1), in culture supernatant and the proliferative response were assessed using sandwich ELISA and (3)H-thymidine incorporation, respectively. No significant proliferative response to FVIII was observed, whereas PHA induced a strong response in all groups. No cytokine secretion was observed in response to FVIII stimulation. Although PHA induced IL-10, TGF-beta1 and IFN-gamma secretion in all groups, the level of IFN-gamma was significantly lower in hemophilia A patients than in normal individuals (p < 0.0001). The levels of TGF-beta1 and IL-10 were similarly higher in patients compared with normal subjects, but the difference was not statistically significant. Lack of FVIII-induced proliferative response and cytokine production together with reduced secretion of PHA-induced IFN-gamma in both groups of patients suggest involvement of nonspecific immunosuppression possibly due to hepatitis C virus (HCV) infection observed in the majority of patients.

Management of factor VIII inhibitors

The development of inhibitory alloantibodies to factor VIII (FVIII) is a major complication of clotting factor replacement therapy for hemophilia A. Inhibitor development compromises effective hemostasis management in affected individuals and results in higher morbidity and costs of care compared with hemophilic individuals without anti-FVIII antibodies. The therapeutic approach to the management of bleeding in the presence of low- and high-titer inhibitors is founded on the principles of either saturating antibody with excess FVIII or bypassing the FVIII requirement altogether. Although spontaneous antibody disappearance does occur, immune tolerance is often required for antibody eradication. Studies aimed at optimizing this treatment approach and developing newer strategies for inhibitor prevention are ongoing.

Management of factor VIII inhibitors

The development of inhibitory alloantibodies to factor VIII is arguably one of the most severe and important complications of clotting factor concentrate exposure in haemophilia A. The development of an inhibitor compromises the ability to effectively manage haemorrhage, resulting in a greater rate of disability, complications and costs of therapy. This chapter briefly reviews the epidemiology, immunobiology, and laboratory evaluation of inhibitors. It discusses the therapeutic approach and management of inhibitors in various clinical settings and also focuses on inhibitor eradication practices (immune tolerance) and newer experimental strategies with potential clinical application for inhibitor prevention.

Mortality and causes of death in patients with hemophilia, 1992-2001: a prospective cohort study

BACKGROUND

Clotting factor products have been safe for HIV since 1985, and for hepatitis C since 1992. Few studies have reported on mortality in the total population of hemophilia patients after the period of risk of viral infection transmission.

OBJECTIVES

We studied the mortality, causes of death, and life expectancy of hemophilia patients between 1992 and 2001. We compared these findings with those of previous cohorts, together spanning the periods before, during, and after the use of potentially contaminated clotting products.

PATIENTS AND METHODS

We performed a prospective cohort study among 967 patients with hemophilia A and B. Death rates, overall and cause-specific, were compared with national mortality figures for males adjusted for age and calendar period as standardized mortality ratio (SMRs).

RESULTS

Between 1992 and 2001, 94 (9.7%) patients had died and two patients were lost to follow-up (0.2%). Mortality was 2.3-times higher in hemophilia patients than in the general male population (SMR 2.3 95% confidence interval 1.9-2.8). In patients with severe hemophilia, life expectancy decreased from 63 (1972-1985) to 59 years (1992-2001). Exclusion of virus-related deaths resulted in a life expectancy at birth of 72 years.

CONCLUSIONS

AIDS was the main cause of death (26%) and 22% of deaths were because of hepatitis C. In patients not affected by viral infections, there still appeared to be a trend toward a moderately increased mortality compared with the Dutch male population. Thus, mortality of patients with hemophilia is still increased; this is largely because of the consequences of viral infections.

Italian guidelines for the diagnosis and treatment of patients with haemophilia and inhibitors

The Italian Association of Haemophilia Centres reviewed and finally approved in November 2004 the new Italian Guidelines for the diagnosis and treatment of patients with clotting factor inhibitors. The recommendations have been based on the identification of levels of clinical evidence derived from the systematic review carried out in 2003 by the School of Health and Related Research, the University of Sheffield, UK, and further integrated by clinical studies published from 2003 to 2004. The Italian guidelines consist of six major domains concerning inhibitor definition, epidemiology, risk factors, diagnosis, inhibitor eradication, management of bleeding episodes, in patients with congenital and acquired coagulation disorders, with 121 statements, 59 synthesis and 54 recommendations. We report here recommendations and open issues concerning the diagnosis and monitoring of inhibitors, inhibitor eradication and the management of bleeding in patients with haemophilia A and B.

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

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

Dose and response in haemophilia - optimization of factor replacement therapy

The mainstay of the management of haemophilia is the replacement of clotting factors, using clotting factor concentrates (CFC) in a way that prevents bleeding and its complications. Beginning with small doses, as whole blood and plasma over 50 years ago, highly purified CFCs are now administered frequently in large doses to effectively treat this condition so that even people with severe haemophilia can lead near normal lives. However, with such regimens, compliance and expense have both become significant issues. The question therefore is whether the current models of clotting factor replacement are optimal. This article reviews the literature on the dose-response relationship in haemophilia, with particular reference to management of musculoskeletal bleeding and surgical haemostasis. Current practices are based on uncontrolled observational data. Less intensive protocols could achieve similar outcomes. Large multi-centre prospective studies are needed to provide comparative data on unresolved issues so that factor replacement therapy can be optimized, based on evidence.

Systematic review of the management of patients with haemophilia A and inhibitors

The London Directorate of Health and Social Care Research and Development Group recently commissioned the School of Health and Related Research at the University of Sheffield to perform a systematic review of the management of patients with haemophilia A and inhibitors. The main areas of the review were the epidemiology of inhibitors, the role and effectiveness of immune tolerance induction, and the control of acute bleeding. In addition, an economic model of the different treatment strategies was constructed. Among the findings was that the overall prevalence of inhibitors in unselected haemophilic populations is 5-7%, with the cumulative inhibitor risk varying from 0% to 39%. The prevalence of inhibitors was inversely related to the size of the reported population. Immune tolerance induction was considered desirable, with evidence suggesting that the Bonn protocol may be more effective than either the Malmo or low-dose protocols. Immunosuppressive drug regimens on their own were ineffective. Activated prothrombin complex concentrates (aPCC) were more effective than non-aPCC. Recombinant activated factor VII was also effective, but there were no randomized trials comparing this agent with aPCC. Porcine factor VIII was highly effective in both treating acute bleeding episodes and preventing bleeding after surgery.

Inhibitors in hemophilia A

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.