Treating haemophilia A with recombinant blood factors: a comparison

A study of reported factor VIII use around the world

The effect of replacement therapy has significantly improved the morbidity and mortality of people with haemophilia A in high income countries, a recent socio-economic development as the availability of safe concentrates has been matched by a willingness for their provision through reimbursement. In the developing world, however, this state has not been achieved, primarily because of the low visibility of haemophilia coupled with its expense, leading to inadequate treatment with its sequelae of severe pain, joint deformities, arthropathy, disabilities, and even death in childhood or early adult life. The objective of this paper was to study the reported factor VIII (FVIII) use on a country-by-country basis. Data on the reported FVIII use for 104 countries were obtained from the Marketing Research Bureau, Inc. and the World Federation of Hemophilia. The results show that FVIII use varies considerably among countries, even among the wealthiest of countries. The use of FVIII concentrate increases as economic capacity increases; in addition, consumption of FVIII has been increasing at a greater rate in high income countries. Given these trends, there probably will be a global increase in FVIII concentrates usage. Such information is critical for national healthcare agencies to determine realistic budget priorities in planning for an increased allocation of resources required to improve the treatment of patients with haemophilia A. This information is also important for pharmaceutical manufacturers to adequately plan for increased production of FVIII concentrates.

Recombinant proteins in therapeutics: haemophilia treatment as an example

One of the most spectacular advances in the history of scientific knowledge was the discovery of deoxyribonucleic acid (DNA) by Watson and Crick in 1953. This enabled certain proteins to be prepared in this way for their therapeutic use in clinical practice. Today, in the first decade of the 21st century, hundreds of therapeutic proteins have been produced recombinantly and about 50 of them have been approved for clinical use. Because of the specific procedure used for obtaining these products, which is based on expressing a atherapeutica gene from a fragment of DNA in a cell to produce a functional protein that is free from any human or animal component, they are especially acleana and thus the therapy of choice for many current diseases. The immediate question is: why are recombinant products not used more extensively given their high efficacy and maximum safety? In short, we are faced with an interesting but also unfortunate paradox of pharmacology that greater progress in therapeutic procedures is not always associated with greater introduction of those resources that are safest, for the simple reason that they are more costly.

Development of a Peptidomimetic Ligand for Efficient Isolation and Purification of Factor VIII via Affinity Chromatography

Hemophilia A, one of the most severe bleeding disorders, results from an inherited deficiency of factor VIII (FVIII) function. Treatment by injection of FVIII has been a common procedure for decades. Nevertheless, the production and purification of FVIII remains a challenging task. Current procedures using immunoaffinity chromatography are expensive and suffer from the instability of the applied antibody ligands, which elute along with the product and contaminate it. Recently, FVIII was purified by use of octapeptide ligands, but their low protease-resistance limits their application. We here report the systematic rational and combinatorial optimization procedure that allowed us to transfer the octapeptide ligands into a small peptidomimetic. This compound is the smallest ligand known for separation of such a large protein (330 kDa). It not only binds and purifies FVIII with high efficiency but also is stable, protease-resistant, and cheap to produce in preparative scale. Hence it offers a valuable alternative to antibody-based purification procedures.

Hemorrhagic subcutaneous nodules: an initial clinical sign of hemophilia A

A 9-month-old boy presented with multiple hemorrhagic subcutaneous nodules after treatment with oral antibiotics for an upper respiratory tract infection. Excessive bleeding after an incisional biopsy led to a diagnosis of hemophilia A. While this was an unexpected presentation of hemophilia, screening laboratory coagulation studies prior to biopsy would have revealed the etiology. Similar presentations should alert dermatologists to suspect an underlying coagulation defect prior to biopsy, thus averting bleeding complications.

IgE-mediated anaphylactic reaction to purified and recombinant factor VIII in a patient with severe haemophilia A

We report a 51-year-old patient with severe haemophilia A developing a severe life-threatening anaphylactic reaction to recombinant factor VIII (rFVIII). Anaphylactic reactions are a rare but well-known side effect of FVIII products. The nature of these reactions could not be clarified as previous studies failed to demonstrate a specific IgE response. Here, we could prove a grade 3 anaphlyactic reaction as an IgE-mediated response to rFVIII for the first time by Western blotting.

Role of the B domain in proteolytic inactivation of activated coagulation factor VIII by activated protein C and activated factor X

Hereditary deficiency of factor VIII (FVIII), haemophilia A, is treated by plasma-derived FVIII (pd-FVIII) or recombinant FVIII (rFVIII) infusions. B-domain-deleted FVIII (BDD-rFVIII), although generally safe and effective, was less effective than pd-FVIII in prophylaxis -- evidenced by a 2.5-fold higher bleeding incidence. Assessment of BDD-rFVIII activity in chromogenic and one-stage clotting assays gives up to 50% difference in activity values. As earlier studies demonstrated identical activation and cofactor activity of BDD-rFVIII and pd-FVIII, we decided to study susceptibility of thrombin-activated pd-FVIII, full-length rFVIII and BDD-rFVIII to proteolytic inactivation by activated protein C (APC) and activated factor X (FXa) in a purified system. Proteolysis was monitored by Western blot using monoclonal antibodies C5 and R8B12 specific for the A1 and A2 domains, respectively. Inactivation was monitored by measuring the residual cofactor activity of FVIII forms in a one-stage clotting assay. Proteolysis of A1 and A2 domains of activated BDD-rFVIII proceeded 11 or 13 times faster than that of pd-FVIII or full-length rFVIII. Inactivation of activated BDD-rFVIII was two to three times faster by APC and five to six times faster by FXa. We suggest that differences in proteolytic inactivation may contribute to differences between BDD-rFVIII and pd-FVIII in assaying and in clinical use.

Infectious disease in the blood supply and the public health response

The consistent improvements in hemophilia care seen in the years 1960 to 1980 halted when human immunodeficiency virus (HIV) appeared in the blood supply. In the early 1980s, before HIV virulence was fully understood, a complacent blood therapy industry and its regulators waffled on an appropriate response. As a result, the period between the appearance of HIV and its effective elimination from the blood supply was lengthy and many recipients of blood therapies became infected, with devastating impact on their quality of life, quality of care, and longevity. As the decade wore on, even as they began to better understand the threat, industry and public health officials continued to stall, in part because development of interventions was costly and cumbersome. In order to protect the safety of the blood supply and blood-derived therapies, it must be recognized that new pathogens will continue to emerge. Agencies' and companies' decision-making processes in this regard must therefore be proactive rather than reactive, and should preferably implement a formalized risk-management approach. The ongoing safety of blood therapies and the blood supply will also depend on continued vigilance and research. Finally, the hemophilia community must be allowed to play an active and educated role in their own care.

Economic and epidemiological modelling of full-length antihaemophilic factor (recombinant), plasma/albumin-free method, in previously treated patients with haemophilia A : comparison with B-domain deleted rFVIII, and value of potential viral transmission reduction due to plasma/albumin-free status

OBJECTIVES

To the extent that current recombinant clotting factor concentrates contain even trace amounts of human or animal protein, there is continuing potential for transmission of nonenveloped viruses, including hepatitis A, and parvovirus, and the theoretical potential for transmission of relatively unknown agents, such as prions (Creutzfeldt-Jakob disease, or its variant). Full-length antihaemophilic factor (recombinant), plasma/albumin-free method (rAHF-PFM; Advate), represents a novel pharmacotherapeutic option for the management of haemophilia A. This investigation was designed to discern: (i) the efficacy-based use pattern (International Units [IUs]) of rAHF-PFM versus B-domain deleted rFVIII (BDDrFVIII; ReFacto) required to resolve a bleeding episode (event) among previously treated patients with haemophilia A employing on-demand treatment; (ii) the health service expenditure pattern (percentage differential; payor's perspective) associated with use of rAHF-PFM versus BDDrFVIII among previously treated patients with haemophilia A employing on-demand treatment; and (iii) the fiscal utility attributable to the plasma/albumin-free status of rAHF-PFM under the assumed emergence of a novel and infectious blood (plasma)-borne virus.

MATERIALS AND METHODS

Data stemming from phase II/phase III clinical trials of rAHF-PFM, together with published literature on BDDrFVIII, afforded calculation of the probability of occurrence for specific endpoints of interest (e.g. non-response to first infusion). Monte Carlo simulation, a decision-analytical framework parameterised with stochastic (random) and deterministic (fixed) components (10 000 iterations per month [or year] of age examined [3, 6, 9 months; years 1 through 19; and years 20, 30, 40, 50, 60, 70 and 80]) was used to compare: (i) the efficacy-based use pattern by treatment option; and (ii) the health service utilisation-based expenditure pattern by treatment option, accounting for the need for subsequent infusion(s), and potential complications (use of services) stemming from failure of the initial infusion (five scenarios). Theoretical and direct modelling methods for assessing the fiscal utility attributable to the plasma/albumin-free status of rAHF-PFM under the assumed emergence of a novel and infectious blood (plasma)-borne virus were developed. Assumptions included: (i) a low population infection rate (<5%); (ii) annual health service expenditures equivalent to 5% of that observed with HIV/AIDS; and (iii) the number of bleeding events experienced per year were 6, 9 or 12.

RESULTS

Monte Carlo simulation-replicated simulations per year of age examined revealed: (i) use of rAHF-PFM resulted in a 12.20% median reduction in the number of IUs required to resolve a bleeding episode (event) relative to BDDrFVIII (p < 0.05); and (ii) a health service utilisation-based savings [primary care; hospital] (p < 0.05; range 13.74-39.34% [dependent on intensity (sequencing) of care required]) with rAHF-PFM relative to BDDrFVIII. The overall scenario-weighted health service utilisation-based savings was 16.94% (p < 0.05). Under the assumption of the emergence of a novel and infectious blood (plasma)-borne virus, deterministic models for persons weighing 20 kg, 50 kg and 80 kg all revealed a savings potential ($US per IU) with use of rAHF-PFM relative to use of a non-plasma/albumin-free product.

CONCLUSION

Use of rAHF-PFM in on-demand management of haemophilia A offers enhanced patient safety and represents a fiscally prudent therapeutic strategy.