Comparative thrombotic event incidence after infusion of recombinant factor VIIa vs. factor VIII inhibitor bypass activity--a rebuttal

Use of the UKHCDO Database for a postmarketing surveillance study of different doses of recombinant factor VIIa in haemophilia

INTRODUCTION

Recombinant factor VIIa (rFVIIa) is recommended in Europe at standard (3 × 90 μg kg^-1 ) or high (1 × 270 μg kg^-1 ) doses. When granting the license for the high dose, the European Medicines Agency (EMA) requested postmarketing surveillance for thrombosis. This was conducted by the United Kingdom National Haemophilia Database (NHD) on behalf of Novo Nordisk and the EMA.

AIM

To assess the use and safety of rFVIIa utilizing prospective data collected by the NHD (1 January 2008 to 30 June 2011).

RESULTS

Data were obtained from 67 haemophilia A/B patients with inhibitors treated for 1057 bleeds and 31 acquired haemophilia patients treated for 70 bleeds. Initial rFVIIa dose was categorized post hoc as low (<90 μg kg^-1 ), intermediate (≥90-<180 μg kg^-1 ) or high (≥180-<270 or ≥270 μg kg^-1 ). For haemophilia A/B, high and lower initial rFVIIa dose was used for 38.4% and 51.4% of episodes, respectively, while for acquired haemophilia, the values were 11.4% and 77.1% respectively. Median initial doses were higher for haemophilia A/B (146.3 μg kg^-1 ) than acquired haemophilia (90.5 μg kg^-1 ). A single administration of rFVIIa was the most frequently used regimen for haemophilia A/B, in contrast with standard recommendations and previous reports. For acquired haemophilia, most episodes were treated with multiple doses. No adverse drug reactions or thromboembolic events were reported for any rFVIIa dose.

CONCLUSION

The novel use of a national database for postmarketing surveillance has demonstrated acceptable safety for all recommended doses of rFVIIa.

Recombinant factor VIIa (eptacog alfa): a review of its use in congenital hemophilia with inhibitors, acquired hemophilia, and other congenital bleeding disorders

Recombinant factor VIIa (NovoSeven; also known as recombinant activated factor VII or eptacog alfa) is structurally similar to human plasma-derived coagulation factor VIIa, but is manufactured using DNA biotechnology. Recombinant factor VIIa interacts with thrombin-activated platelets to produce a thrombin burst leading to accelerated fibrin clot formation localized to the site of vascular injury. It is approved in many countries for use as an intravenous hemostatic agent in patients with congenital hemophilia with inhibitors, and also for acquired hemophilia, factor VII deficiency, and Glanzmann thrombasthenia in some countries. Studies have shown it to be effective and generally well tolerated when used intravenously to treat bleeding episodes or provide hemostatic cover during surgery in patients with congenital hemophilia with inhibitors, acquired hemophilia, factor VII deficiency or Glanzmann thrombasthenia. Based on available data, its efficacy in terms of patient-assessed response may be similar to that of activated prothrombin complex concentrate (aPCC), but treatment with a single 270 microg/kg dose of recombinant factor VIIa might reduce the need for rescue therapy compared with aPCC. Recombinant factor VIIa is not immunogenic in patients with hemophilia, does not produce an anamnestic response in hemophilia patients with inhibitors, and has very low thrombogenicity. It is recommended in guidelines as the treatment of choice for bleeds in patients with hemophilia B with high-responding inhibitors and for patients with factor VII deficiency, and is also a first-line therapeutic option for high-responder hemophilia A patients with inhibitors and those with acquired hemophilia. Cost data from pharmacoeconomic analyses support its use in hemophilia patients with inhibitors. Thus, recombinant factor VIIa is a valuable treatment option for patients with these rare, but potentially serious, bleeding disorders.

Factor VIII inhibitor bypassing activity (FEIBA) - addressing safety issues

Bypassing therapy is usually necessary to control or prevent bleeding episodes in patients with haemophilia A or B and high-titre inhibitors. Factor VIII inhibitor bypassing activity (FEIBA) has a long history of successful use in the acute, surgical and prophylactic treatment settings, but safety concerns have made some reluctant to administer this bypassing agent. A review of the literature and clinical trial data show that FEIBA has a low prevalence of thrombosis, a low prevalence of anamnesis that does not impact haemostatic efficacy and an excellent record of pathogen safety and clinical tolerability.

The Evidence for the Use of Recombinant Human Activated Factor VII in the Treatment of Bleeding Patients With Quantitative and Qualitative Platelet Disorders

There are increasing reports suggesting that high-dose recombinant human activated factor VII (rFVIIa) is effective in the treatment and prevention of bleeding in patients with quantitative and qualitative platelet disorders. These clinical observations are supported by evidence that FVIIa binds weakly to activated platelet surface and at high concentration improves thrombin generation. In experimental models, this improved thrombin generation enhances platelet adhesion in thrombocytopenic conditions and enhances adhesion and aggregation of platelets lacking glycoprotein IIbIIIa (integrin alpha(IIb)beta(3)), characteristic of the qualitative platelet disorder Glanzmann thrombasthenia (GT). There is a need for clinical trials to confirm the safety and efficacy of rFVIIa in patients with various quantitative and qualitative platelet defects, either by itself or in combination with other hemostatic agents such as platelet transfusion. Pending the availability of such data, rFVIIa may be considered in severe bleeding in thrombocytopenia and GT patients with platelet antibodies and refractory to platelet transfusions and other standard treatments. An international survey suggests that rFVIIa at about 90 microg/kg every 2 hours for 3 or more doses could be used for GT patients with severe bleeding, but confirmation by larger studies is needed. For GT patients undergoing surgery and for treatment and prevention of bleeding in thrombocytopenic patients, the optimal rFVIIa regimen remains to be defined.

A review of the off-label use of recombinant activated factor VII in a developing country tertiary care center

Recombinant activated factor VII (rFVIIa) was first approved for treatment of congenital hemophilia. It could, however, also have a role in management of patients without pre-existing coagulopathies who undergo surgical procedures, have life-threatening hemorrhages, or sustain traumas associated with major blood loss. A retrospective chart review was performed for all cases given rFVIIa at American University of Beirut Medical Center (AUB MC). Patients with a previous medical history of thrombophilia were excluded. There were four pediatric patients with a mean age younger than 1 year. Adult patients' mean age was 64.5 +/- 17.4 years. The most common off-label uses for rFVIIa are control of hemorrhage during the repair of aortic dissection (4/17 cases) or following intracerebral hemorrhage (4/17 case). One trauma patient received the medication. Complications included cerebral ischemia in one patient. Three of the patients died but their death was not related to the bleeding or the medication. Based on the prognostic score proposed by Biss and Hanley, seven patients were low risk, four intermediate risk, and six high risk. Although off-label use of rFVIIa at AUB MC was supported by published reports, and associated with few complications, guidelines are required to control use of this medication.