Immune tolerance induction in hemophilia patients with inhibitors: costly can be cheaper

The development of inhibitory antibodies to factor VIII (FVIII) occurs in approximately 30% to 40% of patients with severe hemophilia A. Management options for patients with inhibitor include eradicating it via immune tolerance induction (ITI) or treating bleeding episodes with large quantities of hemostatic agents. ITI is costly, approaching $1 million for the average 5-year-old, but if successful results in improved clinical outcomes. We constructed a decision analysis using the Markov process to model expected clinical outcomes and costs over a lifetime for a typical 5-year-old hemophiliac with high inhibitor levels. Estimates of relevant variables were based on a thorough review of the medical literature. Outcomes modeled included total lifetime costs as well as life expectancy. The decision analytic model revealed that the ITI strategy was associated with an increase in projected life expectancy of 4.6 years. Total estimated lifetime costs for the ITI strategy were approximately $1.7 million less per patient. Sensitivity analyses over clinically and economically reasonable ranges did not change these findings. The insight that ITI can achieve an improved clinical outcome while being cost-saving is not reflected in many current treatment regimens. This example also illustrates that expensive therapy for patients with a chronic disease may be cost effective when analyzed from a societal perspective over the patient's lifetime. This finding has important policy implications for medical decision makers at many levels and reinforces the need to undertake pharmacoeconomic analyses and choose therapies from a long-term, societal perspective. (Blood. 2000;96:1698-1702)     

Immune tolerance induction with recombinant factor VIII in hemophilia A patients with high responding inhibitors

Immune tolerance induction (ITI) eradicates inhibitors in patients with hemophilia A. This study was designed to investigate the success rate of ITI in high-responding inhibitor patients with severe hemophilia A using recombinant factor VIII (rFVIII). Twenty-six patients received different ITI regimens until a normal recovery (>66%) and half-life (>6 h) of infused FVIII was achieved. In order to maximize the chance of success, the initiation of ITI was deferred in the majority of patients until the inhibitor declined to <10 BU. Twenty-two patients (85%) had baseline inhibitor levels <10 BU (median 2.3 BU) when ITI began. Within a median of 6 months, immune tolerance was achieved in 19 of 26 patients (73%) including 12/17 (70%) with intron 22 inversion, 5/7 (71%) with other null mutations and two with small deletion/insertions in the F8 gene. In conclusion, recombinant FVIII induces a high rate of immune tolerance even in carriers of null F8 mutations.     

Immune tolerance induction for patients with severe hemophilia A: a critical literature review

The development of inhibitors that neutralize the function of clotting factor VIII (FVIII) is currently the most challenging complication associated with the treatment of hemophilia A as it increases the disease-related morbidity and mortality. Immune tolerance induction (ITI) is the only documented strategy to eradicate persistent inhibitors in severe hemophilia A patients. Several studies have been conducted so far to identify patient- and treatment-related factors associated with greater ITI success. The currently available literature on ITI in hemophilia A will be critically reviewed in this article. In particular, we will focus on the role of the type of FVIII product on ITI outcome by analyzing the clinical and experimental data.     

Immune tolerance induction in hemophilia A: a review

In this article, a comparative analysis of the data stemming from the studies conducted in the field of immune tolerance treatment (ITT) of hemophilia A was attempted. Comparisons are difficult because previous studies differ in many respects, including the dosage of factor (F) VIII, the number of FVIII administrations per day, the association with immunosuppressive drugs (prednisone, cyclophosphamide), and, most importantly, the definition of success in terms of the reacquisition of tolerance. However, a number of variables consistently influenced outcome: the inhibitor titer, either the maximum one or the one assayed before immune tolerance (IT) start and age. As to the FVIII dose, results are contrasting, even though the overall impression is that high dosages are associated with higher success rates. Treatment duration analyses appear to be fairly consistent in all the studies, with 1 year as the crucial time period useful in predicting outcome. Preliminary data suggest that concentrates containing von Willebrand factor may increase the success rate and allow patients refractory to IT procedures carried out with ultrapure or recombinant concentrates to become tolerant in the end. These data need to be formally confirmed in trials that compare the different brands. In the studies published so far, a common language and widely accepted definitions of the variables have emerged, which are important in setting up the controlled trials and improving the comparison among published data.     

Immune tolerance in hemophilia with factor VIII inhibitors: predictors of success.

BACKGROUND AND OBJECTIVES: Long term administration of high doses of factor VIII (FVIII) was shown to eliminate alloantibodies to FVIII (FVIII inhibitors). This procedure is widely referred to as immune tolerance (IT). DESIGN AND METHODS: In 1989 an international registry of IT protocols was created which recruited 314 patients with severe hemophilia A (HA) and an inhibitor who were given IT treatment. RESULTS: Fifty hemophilia care centers worldwide contributed data to the registry; 94.8% of the patients were high responders. The median inhibitor titer prior to IT (pre-titer) was 7 BU (range 0-720). The FVIII doses ranged from <50 International Units (I.U.)/kg/b.w./day to >200. At the end of IT, 140 patients had undetectable inhibitor titers, including 128 who also had normal FVIII kinetics. The remaining 174 patients included 66 with treatment failure, 23 who achieved partial responses, 48 patients in whom treatment was ongoing and 37 with data inadequate to evaluate outcome. Using logistic regression, the best predictive model for success included maximum inhibitor titer, pre-titer, dose and age at treatment. FVIII dose and pre-titer were also associated with treatment duration, as was the time between inhibitor detection and treatment. The risk of relapse was approximately 15% after 15 years of follow-up. INTERPRETATION AND CONCLUSIONS: This study underscores the importance of starting IT as early as possible, at the lowest inhibitor titer and with high FVIII doses in order to maximize the chance of treatment success and minimize treatment costs.     

Proteolytic antibodies activate factor IX in patients with acquired hemophilia

Acquired hemophilia is a rare bleeding disorder characterized by the spontaneous occurrence of inhibitory antibodies against endogenous factor VIII (FVIII). IgG from some patients with acquired hemophilia hydrolyze FVIII. Because of the complex etiology of the disease, no clinical parameter, including the presence of FVIII-hydrolyzing IgG, has been associated with patient's survival or death. Here, we demonstrate the presence of anti-FIX antibodies in acquired hemophilia patients. IgG from some patients were found to hydrolyze FIX. In most cases, IgG-mediated FIX-hydrolysis resulted in FIX activation. IgG-mediated hydrolysis of FIX thus led to the significant generation of activated FIX in 25 of 65 patients. Based on the estimated kinetic parameters, patients' IgG activated up to 0.3nM FIX in 24 hours, an amount that restored thrombin generation in vitro provided the presence of more than or equal to 3% residual FVIII activity in plasma. This work identifies proteolytic IgG as novel molecules able to activate FIX under pathologic conditions. IgG-mediated FIX activation is a prevalent phenomenon among acquired hemophilia patients. The presence of FIX-activating IgG may partly compensate for the antibody-mediated inhibition of endogenous FVIII in restoring thrombin generation. This clinical trial was registered at www.clinicaltrials.gov as #NCT00213473.     

Immune implications of gene therapy for hemophilia

Similar to any novel treatment strategy for hemophilia, gene therapy faces the question of the risk of formation of inhibitory antibodies to the therapeutic factor VIII or factor IX protein. Activation of CD4 (+) or CD8 (+) T cells could lead to antibody formation or cytotoxic T lymphocyte responses to transgene-expressing cells. Preclinical studies in animal models of hemophilia A and B with different mutations in the dysfunctional gene shed light on the risk for such immune responses and point toward strategies to avoid immune activation or even promote tolerance induction. The impacts of variables such as choice and design of gene transfer vector, underlying gene mutation, route of vector administration, and transient immune suppression are discussed. Maintenance of immunological hyporesponsiveness to the therapeutic gene product is critical for successful gene therapy. Recent studies provide evidence for tolerance induction to coagulation factor antigens by viral hepatic or neonatal in vivo gene transfer, by in utero gene delivery, and by oral or nasal administration of protein or peptides.     

Immune tolerance induction in patients with severe hemophilia with inhibitors: expert panel views and recommendations for clinical practice

For hemophilia patients with inhibitors, immune tolerance induction (ITI) may help to restore clinical response to factor (F) VIII or FIX concentrates. Several ITI regimens and protocols exist; however, despite 30 yr of progressive investigation, the ITI evidence base relies mainly on observational data. Expert opinion, experience, and interpretation of the available evidence are therefore valuable to support clinical decision-making. At the Sixth Zürich Haemophilia Forum, an expert panel considered recent data and consensus to distill key practice points relating to ITI. The panel supported current recommendations that, where feasible, ITI should be offered early to children and adults (ideally ≤ 5 yr of inhibitor detection) when inhibitor titers are <10 Bethesda units (BU) and should be stopped when successful tolerance is achieved. For hemophilia A inhibitor patients, ITI can be founded on recombinant FVIII at high doses. The panel considered that patients with a high bleeding frequency should be offered additional prophylaxis with a bypassing agent. For patients with hemophilia B, there may be a benefit of genetic testing to indicate the risk for inhibitors. ITI is often less effective and associated with a greater risk of side effects in these patients. For high-titer inhibitor (≥ 5 BU) hemophilia B patients, the panel advised that bypassing agents could be offered on demand in addition to ITI. Within future ITI regimens, there may be a role for additional immunosuppressant therapies. Participants agreed that research is needed to find alternatives to ITI therapy that offer durable and sustained effects and reduced rates of complications.     

Low-dose immune tolerance induction in hemophilia A patients with inhibitors

In patients with hemophilia A and inhibitory alloantibodies against factor VIII, various dosage schedules are used to obtain immune tolerance. In this study, we have evaluated the results of 13 years of low-dose immune tolerance induction and factors that are predictive of a positive result. The effect of immune tolerance induction in relation to age at inhibitor development, number of exposure days, age at start of therapy, maximum inhibitor titer, factor VIII products involved, and virologic status were determined. We evaluated 24 patients with severe hemophilia A and inhibitors who were treated with regular infusions with low-dose (25 U/kg every other day) factor VIII to obtain immune tolerance. In 21 of 24 patients (87%), immune tolerance induction was successful. The response time was determined by two factors: the highest inhibitor level and the age at inhibitor development. In patients with maximum inhibitor levels of less than 40 Bethesda units (BU)/mL, immune tolerance was obtained sooner than in patients with inhibitor levels exceeding 40 BU/mL (P = .005). Patients in whom an inhibitor developed before the age of 2.5 years also tended to have a quick immune response (P = .014). Immune tolerance with low-dose factor VIII is often successful in hemophilia A patients with inhibitors. Young children and patients with maximum inhibitors of less than 40 BU/mL show a relatively rapid response.     

Immune tolerance induction with highly purified plasma-derived factor VIII containing von Willebrand factor in hemophilia A patients with high-responding inhibitors

We retrospectively evaluated the efficacy of immune tolerance induction (ITI) in a homogenous cohort of eight patients with constitutive severe hemophilia A with high-responding factor VIII (FVIII) inhibitors using Facteur VIII-LFB/Factane, a highly purified FVIII concentrate containing von Willebrand factor (VWF).     

Induction of immune tolerance in patients with hemophilia A and inhibitors treated with porcine VIIIC by home therapy

Home therapy with porcine factor VIIIC was safe and effective when administered to five hemophilic patients over periods of 8 1/2, 6, 4, 3 1/2, and 2 years. No significant transfusion reactions occurred. Before treatment with porcine factor VIIIC, all five had high-level, high- responding anti-human VIIIC inhibitors initially lacking anti-porcine factor VIIIC activity. Although specific anti-porcine VIIIC inhibitors arose in all patients, these were generally transient, and only one patient became refractory to treatment. We believe that porcine factor VIIIC is the treatment of choice in patients whose inhibitors do not cross-react. All five patients lost their original anti-human VIIIC inhibitors after starting treatment with porcine VIIIC, permitting the reintroduction of human VIIIC in three of them. There has been no recurrence of anti-human VIIIC inhibitor activity during 2 to 3 years of regular treatment with human VIIIC in these patients. This suggests that tolerance to human VIIIC has arisen as a result of treatment with porcine VIIIC. Porcine VIIIC may have a role in the desensitization of some factor VIIIC inhibitor patients.     

Recombinant activated factor VII therapy in acquired hemophilia of the elderly

Acquired hemophilia is a life-threatening condition associated with a high mortality, occurring mainly in elderly patients. We report on a 92-year-old male, administered two courses of 90 microg kg(-1) of recombinant activated factor VII (rFVIIa) due to failure of human factor VIII (FVIII) therapy, without side effects nor evidence of thrombotic complications. Despite the bleeding being completely under control, the patient died on day 11 of acute respiratory failure due to pneumonia. This case confirms previous reports on the complexity and severity of this disorder, showing that rFVIIa is an effective and safe agent for achieving hemostasis even in elderly patients with a FVIII inhibitor.     

Immune complexes in hemophilia

Circulating immune complexes (ICs), assayed by the L1210 enzyme-linked immunoassay, were detected in 48% of patients with hemophilia. A, 50% of patients with von Willebrand's disease, and in none of our patients with hemophilia B. Eighty-five % of the hemophilia A and B patients had mild to moderate disease with only one patient demonstrating a circulating inhibitor. No correlation was found between IC levels and hepatitis B infection, SGOT, disease severity, total quantity of factor VIII or IX infused, time interval from list infusion, or rheumatoid factor positivity. Although the nature of the ICs is not known, the similarity of IC levels between hemophilia A and von Willebrand's disease is discussed with regard to antibodies generated to non-procoagulant portions of the factor VIII molecule.     

The acquired immunodeficiency syndrome in persons with hemophilia

The widespread use of coagulation factor concentrates prepared from the blood of numerous donors has doubled the life expectancy of persons with hemophilia, but parenteral exposure to alloantigens and infectious agents is not free of risk. The prevalence of the acquired immunodeficiency syndrome (AIDS) now approaches 1% in patients with hemophilia, and laboratory evidence of abnormal immunoregulation is found in at least 50% of treated patients with severe hemophilia. The immune defect is multifactorial. The attack rate of AIDS among patients with severe hemophilia appears to have reached a peak; further evidence suggests that only a minority of those infected with human T-lymphotropic virus type III will develop AIDS. The advent of improved donor screening methods and the application of heat treatment of coagulation factor concentrates should further reduce the risk of AIDS in persons with hemophilia.     

Use of porcine factor VIII in the treatment of patients with acquired hemophilia

Data have been collected from 47 centers in Europe and North America on the treatment with porcine factor VIII concentrate of 74 acute bleeding episodes in 65 patients with acquired hemophilia. The median initial anti-human factor VIII auto-antibody inhibitor level was 38 Bethesda unit (BU)/mL (range 1.2 to 1,024) whereas that against porcine was 1 BU/mL (range 0 to 15). The mean initial dose of porcine factor VIII infused was 84 IU/kg, which increased the plasma factor VIII:C activity by 0.85 IU/mL. Therapy was continued for a mean of 8.5 days during which time the average number of infusions was 11. Objective clinical responses were rated as good or excellent in 78% of recipients. Side effects were uncommon; only one patient experienced a severe anaphylactic reaction necessitating the discontinuation of porcine FVIII therapy. After therapy, no increase in the median level of anti- human FVIII or anti-porcine antibody was noted in the group as a whole, although 13 patients showed individual increases in either anti-human or anti-porcine antibody levels or both of more than 10 BU/mL. Of the 7 patients who subsequently rebled, 5 were successfully re-treated and 2 did not respond to further porcine factor VIII treatment. Porcine factor VIII is safe and clinically effective treatment for bleeding episodes associated with acquired hemophilia and should be considered as first-line therapy for patients whose acquired anti-factor VIII:C antibody cross-reacts with porcine factor VIII:C at low levels.     

Surgery-associated acquired hemophilia A

We present two patients who acquired factor VIII antibodies in the immediate postoperative period. One patient was receiving warfarin that was temporarily discontinued but reintroduced after the procedure. Preoperatively, none gave a history of bleeding, even with past surgeries, and both had normal coagulation tests. Within days of surgery, hemorrhage with prolonged activated partial thromboplastin time, low factor VIII levels, and demonstrable factor VIII antibodies were observed. For the patient who was receiving warfarin the severe bleeding was attributed, at the beginning, only to the high international normalized ratio (INR), which resulted in a fatal delay in diagnosis and appropriate treatment. We would like to raise awareness of surgery as a precipitating cause of acquired hemophilia, which is something to be considered with unusual postoperative bleeding. This syndrome is remarkable for its abrupt onset within days of surgery, severe bleeding but potential successful outcome with combined hemostatic control with recombinant activated FVII (rFVIIa) and elimination of the antibody by immunosuppression.     

Selective B-cell depletion with rituximab for the treatment of patients with acquired hemophilia

The activity and safety profile of selective B-cell depletion with rituximab, an anti-CD20 monoclonal antibody, were evaluated in 10 patients with acquired hemophilia. Rituximab was given intravenously at the dose of 375 mg/m(2) once weekly for 4 consecutive weeks. Infusion-related side effects were observed in 3 patients but were of mild intensity and did not require discontinuation of treatment. Eight patients with Factor VIII (FVIII) inhibitor titers between 4 and 96 Bethesda units per milliliter (BU/mL) achieved a complete remission, which was defined as a return to normal FVIII activity and undetectable FVIII inhibitor titers. Two more patients with inhibitor levels greater than 100 BU/mL experienced only a partial transient decrease of the inhibitor after rituximab alone, but they achieved a complete response after being challenged with a combination of rituximab plus pulse intravenous cyclophosphamide. With a median follow-up of 28.5 months (range, 12-41 months), 3 patients have thus far relapsed. Retreatment with the monoclonal antibody at the same dose and schedule resulted in a new sustained response in all these patients. In conclusion, rituximab appears an effective and well-tolerated treatment for patients with acquired hemophilia and low inhibitor titers. A reinforcement of therapy with other agents seems to be required to achieve a full and durable response in those patients with high inhibitor levels.