Sequential therapy with activated prothrombin complex concentrate and recombinant factor VIIa in patients with severe haemophilia and inhibitors

Manipulation of prothrombin concentration improves response to high-dose factor VIIa in a cell-based model of haemophilia

Clinical reports suggest that treatment regimens employing both activated prothrombin complex concentrates (aPCCs) and recombinant activated factor VII (rFVIIa) may control the bleeding in patients with haemophilia who fail to respond to either agent alone. We hypothesised that increased concentrations of prothrombin, as may be observed after the infusion of aPCCs, favourably influence parameters of thrombin generation in haemophilia treated with high-dose rFVIIa. We examined the effect of varied prothrombin and rFVIIa concentrations on thrombin generation in a model of haemophilia. At all concentrations of rFVIIa, increased prothrombin concentrations led to increases in the peak and rate of thrombin generation. In assays with the highest concentrations of prothrombin and rFVIIa, peak thrombin actually equalled that measured in the model of normal haemostasis. The significant impact of prothrombin concentration on the effect of rFVIIa in vitro may explain the improved haemostasis reported with concurrent use of aPCCs and rFVIIa. These results imply that persons with plasma prothrombin levels at either end of the 'normal' range could have significantly different responses to similar rFVIIa doses. Furthermore, these results suggest that increasing plasma prothrombin concentration prior to rFVIIa administration may offer advantages over the use of rFVIIa alone in the treatment of haemophilic bleeding.

The diagnosis and management of factor VIII and IX inhibitors: a guideline from the United Kingdom Haemophilia Centre Doctors Organisation

The revised UKHCDO factor (F) VIII/IX Inhibitor Guidelines (2000) are presented. A schema is proposed for inhibitor surveillance, which varies according to the severity of the haemophilia and the treatment type and regimen used. The methodological and pharmacokinetic approach to inhibitor surveillance in congenital haemophilia has been updated. Factor VIII/IX genotyping of patients is recommended to identify those at increased risk. All patients who develop an inhibitor should be considered for immune tolerance induction (ITI). The decision to attempt ITI for FIX inhibitors must be carefully weighed against the relatively high risk of reactions and the nephrotic syndrome and the relatively low response rate observed in this group. The start of ITI should be deferred until the inhibitor has declined below 10 Bethesda Units/ml, where possible. ITI should continue, even in resistant patients, where it is well tolerated and so long as there is a convincing downward trend in the inhibitor titre. The choice of treatment for bleeding in inhibitor patients is dictated by the severity of the bleed, the current inhibitor titre, the previous anamnestic response to FVIII/IX, the previous clinical response and the side-effect profile of the agents available. We have reviewed novel dose-regimens and modes of administration of FEIBA (factor VIII inhibitor bypassing activity) and recombinant activated FVII (rVIIa) and the extent to which these agents may be used for prophylaxis and surgery. Bleeding in acquired haemophilia is usually treated with FEIBA or rVIIa. Immunosuppressive therapy should be initiated at the time of diagnosis with Prednisolone 1 mg/kg/d +/- cyclophosphamide. In the absence of a response to these agents within 6 weeks, second-line therapy with Rituximab, Ciclosporin A, or other multiple-modality regimens may be considered.

New approaches in the management of inhibitor patients

The most serious current complication of factor replacement therapy for hemophilia patients is the development of neutralizing antibodies to the factor termed inhibitors. Patients with high-titer inhibitors frequently develop serious bleeding complications which do not respond to standard factor replacement therapy. Therefore, they must be treated with the so-called bypassing agents, recombinant factor VIIa and activated prothrombin complex concentrates, neither of which is as effective as standard factor replacement in patients without inhibitors. Immune tolerance therapy aimed at eradicating inhibitors is successful in a majority of patients; however, a sizable minority will have life-long inhibitors and often develop debilitating joint disease. The ultimate goal is to develop strategies aimed at preventing inhibitor development though these have not been realized yet. Until this is achieved, additional novel approaches are needed to improve the treatment of bleeding episodes and to better treat arthropathy once it develops. Finally, there is no laboratory monitoring device which can predict the clinical response of patients to bypassing agents. Thus another goal of current research is to develop such a tool which will enable the individualization of bypassing agent.

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.

High-Dose Recombinant Factor VIIa Therapy in Hemophilia Patients With Inhibitors

Recombinant activated factor VII (rFVIIa; NovoSeven, Novo Nordisk, Bagsvaerd, Denmark) is well established as an effective hemostatic agent for the management and prophylaxis of hemorrhage in hemophilia patients with inhibitors. Treatment schedules usually involve multiple bolus doses of 90 to 120 microg/kg administered every 2 to 3 hours, but recent evidence suggests that the use of higher doses might be justified. Such high-dose regimens may overcome the rapid clearance rate observed in pediatric patients, and may be more convenient for patients with poor venous access. It has been suggested that individually tailored high-dose therapies might be beneficial in selected groups of patients, although careful monitoring of such patients is advised. Thrombelastography has demonstrated considerable success in this regard, allowing accurate assessment of both hemostatic efficacy and individual response to rFVIIa. To date, no safety issues associated with high-dose rFVIIa have been identified. However, it is hoped that further research will support these favorable observations and thus contribute towards more effective dose optimization of rFVIIa in hemophilic inhibitor patients.

Therapeutic decision-making in inhibitor patients

A panel of hematologists met to discuss treatment choices in patients with hemophilia A and inhibitors. The group agreed that the management of bleeding episodes is complicated by a variable response to bypassing therapy, uncertainties regarding optimal dosing of NovoSeven, and concerns about the combined use of NovoSeven and FEIBA. Thrombotic risk was rated very low for both agents, and there was consensus that product selection should not be restricted to recombinant products. Cost considerations in therapeutic decision-making were also discussed.

Prophylactic recombinant factor VIIa in haemophilia patients with inhibitors

Prevention of bleeding, especially into joints, with prophylactic factor infusions is the most effective treatment for severe haemophilia patients. Approximately 15-30% of patients with factor VIII deficiency and 3-5% of patients with factor IX deficiency develop neutralizing antibodies (inhibitors) to factor precluding their use. Such patients often have significant bleeding complications including life- and limb-threatening bleeds and severe joint disease. Prophylaxis for such patients is not generally considered because of the fact that the standard (bypassing) agents for such patients are not as effective as natural factor replacement, because of concerns for thrombotic complications and also because of the very high cost of bypassing agents. We treated two patients with high titre inhibitors with prophylactic recombinant factor VIIa (rFVIIa). The first patient was treated as a result of development of a target joint and to reduce the use of agents that can lead to anamnesis of his inhibitor. The second patient had multiple severe bleeds and was hospitalized 20% of the time over a 2-year period. He had a very poor quality of life. Both patients had shown good responses previously to rFVIIa for treatment of bleeds. Both patients had an outstanding response to prophylaxis albeit at a very high cost. Prophylaxis with rFVIIa can be an effective approach in select inhibitor patients with severe complications related to bleeding.

Therapy for haemophilia: recent advances and goals for the future

In the 20th century, haemophilia evolved from a life-threatening, crippling disease to one for which the prognosis is excellent and many patients lead normal, productive lives. Although dramatic achievements in the treatment of haemophilia have occurred, the current therapies have significant drawbacks. Among these is the relatively high incidence of inhibitor development, the requirement for frequent intravenous infusions to prevent bleeding complications, the lack of effective treatment for established joint disease, and the high cost of treatment. The future goal of haemophilia treatment first and foremost is curing this genetic condition via gene therapy. As this goal is likely many years away, improvements in the current factor products in order to reduce the development of inhibitors and to reduce the frequency of therapy are more immediately achievable goals. Finally, improving the treatment of bleeding complications, particularly in inhibitor patients, and developing novel adjunctive therapies for the management of joint disease are also important goals for the near future. This review will discuss in detail the cu-rrent and future goals of haemophilia therapy.

Hemophilia management: optimizing treatment based on patient needs

PURPOSE OF REVIEW

Progress in hemophilia management over the past year has focused on improving understanding of the most common complications of genetic bleeding disorders and building upon available therapeutic strategies.

RECENT FINDINGS

Research continued to link factor VIII structure with immune recognition and inhibitor formation. Clinical regimens of immune tolerance induction confirmed and expanded basic understanding. Barriers to optimal prevention using prophylaxis were explored allowing future refinements to address unmet needs. Outcome tools to assess joint health and overall quality of life were developed and validated. The inclusion of standardized instruments in assessment of outcome will allow meaningful comparison of available therapies. Use and complications of central venous access devices (CVAD), needed to deliver aggressive infusion regimens, were exhaustively reviewed. Finally, continued progress was achieved in development of improved vectors for future gene therapy of the hemophilias.

SUMMARY

A general theme of recent progress in hemophilia management is harmonization in definitions and assessments of complications and outcomes, facilitating more rigorous and ultimately more useful interpretation of laboratory and clinical research.