Clinical efficacy of prothrombin complex concentrates and recombinant factor VIIa in the treatment of bleeding episodes in patients with factor VII and IX inhibitors

Budget impact and cost-utility analysis of prophylactic emicizumab versus on-demand bypassing agents for adolescent severe haemophilia A patients with inhibitors in India

Introduction

Severe Haemophilia A patients with inhibitors are currently being treated with bypassing agents like activated prothrombin complex concentrates (aPCC) and recombinant factor VIIa. Emicizumab is a recombinant humanized monoclonal antibody, introduced to reduce the bleeding events, improve treatment adherence, and quality of life. However, cost-effectiveness and long-term sustainability of the intervention is not studied in a low middle income setting like India.

Aim

The primary objective of this study was to evaluate the cost-utility of Emicizumab compared to traditional bypassing agents in the treatment of severe haemophilia A patients with inhibitors in India. Secondary objective was to analyze the budgetary impact of introducing Emicizumab for this patient population from the perspective of public health system in India.

Methods

Markov model was created to compare the prophylactic emicizumab therapy against bypassing agents for a hypothetical cohort of 10-year-old adolescents in India. The time horizon was 10 years and model built based on health system perspective. Cost utility was expressed as costs per quality-adjusted life-years (QALYs) gained. All costs were expressed as 2021 US dollars. Probabilistic sensitivity analysis was performed to check the robustness of the estimates.

Results

Prophylactic emicizumab was a cost saving intervention with negative Incremental Cost Utility Ratio (ICUR) against recombinant factor VIIa of -853,573 USD (INR -63,109,773), and negative ICUR of -211,675 USD (INR -15,650,403) against APCC. The estimated total budget for treating all the severe Haemophilia A patients with inhibitors in India was USD 59,042,000 (INR 4,365,329,312) for 10 years' time horizon (per patient cost of USD 295,210 [INR 21,826,646.56]).

Conclusion

Prophylactic emicizumab therapy is a cost saving intervention when compared to both the bypassing agents as it is less costly and more effective for severe Haemophilia A patients with inhibitors in India.

Cost-effectiveness of emicizumab vs bypassing agents in the prevention of bleeding episodes in haemophilia A patients with anti-FVIII inhibitors in France

INTRODUCTION

The development of an anti-FVIII inhibitor is the most serious complication of haemophilia A occurring in up to 30% of severe haemophilic patients. The current management of haemophilia A with inhibitor uses bypassing agents (BPA) and represents a significant therapeutic burden together with a limited adherence to prophylactic treatment. Emicizumab is the first monoclonal antibody developed in haemophilia A approved for the prevention of bleeding episodes in patients with anti-FVIII inhibitor.

AIM

The purpose of this study is to evaluate the incremental cost-effectiveness ratio (ICER) of emicizumab versus BPAs.

METHODS

A Markov model was developed over a five-year time horizon to estimate the comparative costs and benefits of the different therapeutic approaches in this rare disease. Model inputs were clinical, including annual bleeding rate and quality of life, and economical including mainly costs of prophylaxis, bleeds and adverse events.

RESULTS

Emicizumab treatment is dominant, ie lest costly and more effective, in the base-case analysis saving 234 191 € for a gain of 0.88 QALY. This is confirmed by both the deterministic and probabilistic sensitivity analyses. The main limit of the study remains the absence of long-term clinical data allowing to relate treatment consumption to clinical benefit, especially in the progression of haemophilic arthropathy.

CONCLUSION

Our results show that emicizumab is a cost-effective treatment allowing to consider an easy to implement prophylactic treatment for haemophilia A patients with anti-FVIII inhibitors.

Gla-domainless factor Xa: molecular bait to bypass a blocked tenase complex

BACKGROUND

Hemophilia is caused by deficiencies in coagulation factor VIII or IX, resulting in direct blockade of the intrinsic tenase complex and indirect blockade of the extrinsic tenase complex which is rapidly inhibited upon binding of factor Xa to tissue factor pathway inhibitor. We evaluated the ability of Gla-domainless factor Xa, a truncated form of factor Xa devoid of procoagulant properties, to bind to tissue factor pathway inhibitor and to alleviate the physiological inhibition of the extrinsic tenase.

DESIGN AND METHODS

Using a thrombin generation assay triggered by a low concentration of tissue factor, we evaluated the ability of Gla-domainless factor Xa to restore blood coagulation in plasma from hemophilia A and B patients without and with inhibitors. We then compared its efficacy to generate thrombin to depletion of antithrombin or tissue factor pathway inhibitor by specific antibodies. Finally, we compared the kinetics of neutralization of factor Xa and Gla-domainless factor Xa by antithrombin and tissue factor pathway inhibitor.

RESULTS

Gla-domainless factor Xa was able to restore thrombin generation in plasma samples from hemophiliacs. This effect was observed for plasma from hemophilia A patients without or with inhibitors and for plasma from hemophilia B patients. Gla-domainless factor Xa had a lower affinity than factor Xa for tissue factor pathway inhibitor whereas the affinities of both proteins for antithrombin were similar. Finally, despite a short half-life in plasma, the effect of Gla-domainless factor Xa on thrombin generation was sustained for at least 1 hour.

CONCLUSIONS

As Gla-domainless factor Xa was able to restore thrombin generation in plasma from hemophilia patients, our results suggest that it may be an effective alternative to current treatments for hemophilia with or without an inhibitor.

Heparin-induced inhibitory effects of a prothrombin complex concentrate on global tests of haemostasis

Prothrombin complex concentrates (PCC) have been used as bypassing agents for the treatment of haemophilia A patients with inhibitor as well as for replacement therapy in congenital and acquired deficiencies of vitamin-K-dependent clotting factors. The efficacy of PCC is variable, however, especially during long-term and high-dose use, and all currently available products of this nature contain heparin. We have examined the haemostatic properties of PCC using reconstituted whole blood made by mixing coagulation-factor-deficient plasma and washed blood cells. In rotation thromboelastometry (ROTEM), the recommended therapeutic dose of Proplex ST corrected the abnormal patterns. At higher concentrations, however, the ROTEM patterns regressed. In addition, specific assays of coagulation factors appeared unreliable in the presence of 2.5 U/ml Proplex ST; the abnormalities were corrected when protamine sulfate was added. The findings suggest that the presence of heparin in PCC might have a greater effect on global haemostasis. Careful attention to the anticoagulant effect as well as thrombogenicity of PCC is required. Monitoring therapy using such as ROTEM analysis could be highly informative.

Acquired coagulation inhibitor-associated bleeding disorders: an update

Acquired blood coagulation inhibitors are circulating immunoglobulins that neutralize the activity of a specific coagulation protein or accelerate its clearance from the plasma, thus causing a bleeding tendency. In this review, we focus on the nonhemophilic inhibitors of coagulation, i.e. the autoantibodies occurring in individuals without a pre-existent coagulation defect, reporting the most recent advances in the pathophysiology, diagnosis and treatment of these rare acquired bleeding disorders.

Management of bleeding emergencies: when to use recombinant activated Factor VII

Recombinant activated Factor VII (rVIIa) was originally released as a clotting factor, with use limited to a select group of patients who had few other treatment options. Due to the apparent ability of rVIIa to stop bleeding, no matter what the underlying cause, there is great interest in use of rVIIa in a wide range of bleeding patients. This article discusses rVIIa and its uses in a variety of patients, especially liver disease and trauma patients, and makes suggestions for appropriate use. Although most of the reports on rVIIa are anecdotes and case series, there is increasing data for clinical trials to help guide usage.

Acquired hemophilia A: a concise review

Acquired hemophilia A is a rare but severe autoimmune bleeding disorder. It is more frequent in the elderly and results from the presence of autoantibodies directed against clotting factor VIII. In this review, we briefly report on the present state of knowledge regarding acquired hemophilia A, analyzing its epidemiology, pathogenesis, diagnostic, and clinical features. We also describe the main characteristics of this disorder according to its association with different conditions and the most important advances in the treatment of bleeding episodes and the eradication of the autoantibody.

Recent advances in the management of the child who has hemophilia

This article discusses recent advances in the management of the child who has hemophilia.

Inhibitors in congenital coagulation disorders

The development of inhibitory 'allo' antibodies to a deficient coagulation factor is arguably now the most severe and important complication of clotting factor concentrate exposure in haemophilia and other congenital coagulation disorders. Furthermore, development of an inhibitor to the factor VIII or factor IX transgene product remains a significant concern in gene therapy protocols for haemophilia. Although the development of an inhibitor does not usually change the rate, initial severity or pattern of bleeding, it does compromise the ability to manage haemorrhage in affected individuals, resulting in a greater rate of complications, cost and disability. The purpose of this review is to summarize current understanding of the epidemiology, immunobiology, laboratory evaluation and management of inhibitors arising in patients with congenital coagulation disorders. An attempt has been made to focus on recent advances in the immunology of inhibitors, and to speculate on their potential clinical application.

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.