Effect of factor VIII concentrate on leucocyte cytokine receptor expression in vitro: relevance to inhibitor formation and tolerance induction

Costs, quality of life, treatment satisfaction and compliance in patients with beta-thalassemia major undergoing iron chelation therapy: the ITHACA study

OBJECTIVES

Iron chelation treatment (ICT) in beta-thalassemia major (beta-TM) patients undergoing blood transfusions can cause low satisfaction, low compliance, with possible negative consequences on treatment success, patients' wellbeing, and costs. The purpose was to estimate the societal burden attributable to beta-TM in terms of direct and indirect costs, health-related quality-of-life (HRQoL), satisfaction and compliance with ICT in patients undergoing transfusions and ICT.

RESEARCH DESIGN AND METHODS

The naturalistic, multicenter, longitudinal Italian-THAlassemia-Cost-&-Outcomes-Assessment (ITHACA) cost-of-illness study was conducted involving patients of any age, on ICT for at least 3 years, who were enrolled at 8 Italian Thalassemia Care Centers. Costs were estimated from the societal perspective, quantified with tariffs, prices, or net earnings valid in 2006.

RESULTS

One-hundred and thirty-seven patients were enrolled (median age = 28.3, 3-48 years, 49.6% male) and retrospectively observed for a median of 11.6 months. Mean direct costs were euro1242/patient/month, 55.5% attributable to ICT, 33.2% attributable to transfusions. Relevant quantity and quality of productivity was lost. Both physical and mental components of HRQoL were compromised. Little difficulties remembering to take ICT and positive satisfaction with the perceived effectiveness of therapy were declared, but not good levels of satisfaction with acceptance, perception of side effects and burden of ICT.

CONCLUSIONS

The management of beta-TM patients undergoing transfusions and ICT is efficacious, although costly, but overall benefits were not always perceived as optimal by patients. Efforts must be focused to improve patients' acceptance and satisfaction with their therapy; this would contribute to a better compliance and hence an increase in treatment effectiveness and patients' overall wellbeing, with expected improved allocation of human and economic resources.

Reactivity profile of anti-factor VIII antibodies with designed synthetic peptides mimicking epitopes of the C2 and a1 domains

Antibodies (Abs) that block factor VIII (FVIII) activity occur in hemophilia A patients treated with FVIII replacement therapy and severely impair treatment. In this work, we designed and synthesized ten peptides whose sequences are found in putative epitopes at the surface of a1 and C2 domains of the FVIII molecule. These peptides were screened for their ability to inhibit the binding of anti-FVIII Abs from plasmas of hemophilia A patients to FVIII. All peptides were efficient in inhibiting anti-FVIII Abs in plasma from patients with inhibitors, with however different efficiencies. It was found that each tested patient's plasma had a different profile of reactivity with peptides, consistent with an individual anti-FVIII Ab specificity. The profile of recognized peptides was also changing during the treatment of the patients. Three peptides were used in an affinity chromatography assay to attempt to remove anti-FVIII Abs from patients' plasma. Anti-FVIII IgGs were significantly captured by the peptide-Sepharose affinity matrixes as assessed by enzyme-linked immunosorbent assay. However, due to the low level of Abs in the plasma samples, other methods (Chromogenic and Bethesda assays) were not sensitive enough to properly detect the reduction of inhibitors.

Urgent inhibitor issues: targets for expanded research

Although up to 80% of high-responding inhibitors in patients with severe factor VIII deficiency can be eliminated using heterogeneous regimens for immune tolerance induction, the residual morbidity in this population of haemophilic patients is far from trivial. There is an exigent need for focussed basic, translational and clinical research to extend our understanding of the pathogenesis of haemophilic inhibitor development. In this article, we identify four key research needs, including (i) whether presently available clotting factor concentrates (CFCs) have differential antigenicity, giving rise to clinically relevant immunogenicity; (ii) the interplay of quantitative and qualitative (e.g. age at first exposure) influences of CFCs as well as host-environmental factors (e.g. vaccination effects) on inhibitor development; (iii) the therapeutic role (if any) that concurrent immune tolerance with suppressive or immune-competitive therapeutic strategies play in inhibitor eradication and (iv) pending any major therapeutic advances, alternative or enhanced strategies for treating acute haemorrhage and for preventing chronic haemorrhagic events in these patients.

Recombinant vs. plasma-derived products, especially those with intact VWF, regarding inhibitor development

The development of inhibitors in previously untreated patients (PUPs) with haemophilia A is correlated with a variety of endogenous and exogenous risk factors. It is still controversial whether recombinant factor VIII (rFVIII) products pose a higher risk for inhibitor development than plasma-derived (pd) FVIII concentrates, particularly with intact von Willebrand factor (VWF). A systematic review on the epidemiology of inhibitors in haemophilia A investigated the influence of different FVIII products on inhibitor formation. Patients treated with a single pd product had a lower cumulative incidence (0-12.4%) than those treated with a single recombinant concentrate (36.0-38.7%) independent of disease severity, study size, or inhibitor testing frequency. However, this analysis does not take into account the heterogeneity of the study populations. A study investigating the effects of different variables on inhibitor development in PUPs was started 13 years ago by the Paediatric Committee of the German, Austrian and Swiss Society on Thrombosis and Haemostasis Research. This prospectively conducted study revealed a slight difference (P = 0.08) in terms of type of concentrate. In the group of severe haemophiliacs treated with pdFVIII concentrate (n = 57), 12 patients developed an inhibitor (21%), whereas 17 of 47 patients receiving rFVIII (36%) were affected by this complication. This observation was substantiated by retrospective Italian and French analyses. These results, as well as hypothetical considerations, indicate that there is a body of evidence that FVIII products with VWF may be less immunogenic in PUPs. However, in order to provide more evidence a well-designed randomized study is needed.

Risk of inhibitors in haemophilia and the type of factor replacement

PURPOSE OF REVIEW

Inhibitors in haemophilia are a serious complication that may render usual replacement therapy ineffective. The risk is greatest in previously untreated children with severe haemophilia A. The role of replacement factor VIII in this group is an important issue.

RECENT FINDINGS

Until now, few clinical studies have correctly taken into account the variety of cofactors involved in inhibitor development: genetic (familial antecedents, ethnicity, F8 and immune response genotypes), and environmental cofactors (age at first infusion, prophylaxis and intensity of treatment). This is a prerequisite to correctly evaluating the putative role of the type of factor replacement. Prospective cohort studies are therefore urgently needed. Depending on the expected inhibitor risk in the reference group, the intensity of the relationship between risk factor and endpoint, the duration of patient follow up, and the design of the study (balanced or unbalanced groups), cohorts including 200-500 previously untreated children should be sufficient to demonstrate an increased intensity of risk of about 2 or more with one product compared with another.

SUMMARY

Aside from clinical studies, fundamental research is essential to test the multiple hypotheses that could explain a difference in inhibitor risk between the currently available factor VIII concentrates in order to develop less immunogenic factor VIII.

The Role of Immunomodulation in the Management of Factor VIII Inhibitors

Approximately 25% of persons with hemophilia A will have their treatment complicated by the development of anti-FVIII inhibitory antibodies. This adverse event requires the use of alternative hemostatic agents to treat bleeding and the consideration of a protocol to generate immunological tolerance to FVIII. The pathogenetic factors contributing to FVIII inhibitor generation include both patient- and concentrate-related characteristics. The FVIII genotype contributes to this risk as do other, less well defined, immunogenetic factors. The role of the type of FVIII concentrate as a precipitant for inhibitor generation appears to be less influential. Immunomodulatory management of FVIII inhibitors requires sustained and repeated exposure to FVIII through a variety of intravenous immune tolerance induction (ITI) protocols. Certain pre-ITI characteristics predict for the likelihood of success, most especially the pre-ITI anti-FVIII inhibitor titer. Currently, two major areas of debate remain unresolved with relation to the optimal form of ITI schedule. The best FVIII dose to generate FVIII tolerance is under investigation in an international prospective trial, while the issue of whether von Willebrand factor–containing concentrates may provide more powerful tolerizing effects remains open for further discussion. With a variety of ITI protocols, success rates of approximately 80% have been achieved with good-risk patients. In those that fail initial attempts at ITI, additional treatments using agents such rituximab are now being explored with further evidence of success in 60–80% of these salvage patients. Finally, several pre-clinical studies of innovative approaches to achieving FVIII tolerance suggest that combinations of immunomodulatory therapy may be of benefit in the future.