Clinical use of factor VIII and factor IX concentrates

Introduction

Factor VIII (FVIII) and factor IX (FIX) are the cofactor and the pro-enzyme, respectively, acting in the tenase complex, a key mechanism of physiological haemostasis in which a phospholipide-dependent reaction produces the activation of factor X¹. Mutations in the genes encoding for coagulation FVIII or IX, both located in the X chromosome, are responsible for haemophilia A and haemophilia B, respectively. These congenital bleeding disorders occur overall in approximately 1 in 5,000 male live births without racial predilection. However, the prevalence of haemophilia A is estimated 4–6 times higher than haemophilia B^2–3. According to the residual endogenous FVIII/FIX concentrations, individuals with plasma factor levels <1 IU/dL are classified as severe haemophiliacs and represent about half of the diagnosed cases, whereas those with factor levels between 2–5 IU/dL and >5–40 IU/dL are defined as moderate and mild haemophiliacs⁴. Although the bleeding phenotype is recognised to be heterogeneous and affected by many genetic and environmental factors^5–6, this classification reflects rather closely the severity of clinical symptoms. Thus, patients with mild haemophilia experience excessive bleeding in the large majority of cases in response to surgery, other invasive procedures or major injuries^4,7. On the other hand, patients with moderate haemophilia experience excessive bleeding after relatively minor trauma and those with severe haemophilia bleed spontaneously or after trivial trauma^4,8. In the latter, haemarthrosis, particularly into hinged joints (ankle, knee, elbow), is largely the most frequently reported bleeding symptom^8,9. Recurrent joint bleeding is associated with progressive joint morbidity (haemophilic arthropathy), leading to chronic pain and disability, that often warrant orthopaedic surgery and joint replacement¹⁰. Soft-tissue haematomas, mucosal, parenchimal and delayed post-surgical bleeding are less common manifestations, including life-threatening intracranial, neck-throat and gastro-intestinal haemorrhages^8,9,11.

Replacement therapy with intravenously delivered plasma-derived or recombinant FVIII and FIX concentrates, aimed at correcting the coagulation factor deficiency in the case of, or in order to prevent, bleeding is the cornerstone of management of patients with haemophilia A and haemophilia B, respectively. Indeed, these specific and viral-inactivated products are the source of choice of the missing proteins, in preference to fresh frozen plasma (for both factors), cryoprecipitate (for FVIII) or prothrombin complex concentrates (for FIX)¹¹. The two forms of haemophilia have been usually considered indistinguishable from a clinical point of view and, consequently, as regards patterns of treatment. In this respect, most literature data have been achieved in cohorts of patients with haemophilia A and extrapolated to those with haemophilia B. However, according to recent findings, the bleeding tendency associated with FIX deficiency is likely to be less severe, with possible better long-term outcomes¹². Plasma-derived FVIII concentrates may also contain variable amounts of von Willebrand factor (VWF), therefore some products are used in the management of those patients with von Willebrand disease with severe VWF deficiencies, in whom response to endogenous release by desmopressin is impossible or insufficient¹³. After a historical overview of treatment of haemophilia, this article will report the current clinical use of FVIII and FIX concentrates, also with reference to the Italian clinical scenario.

The history of treatment of haemophilia: past and present

In the 1950s and early 1960s, haemophiliacs were treated with whole blood or fresh plasma. Unfortunately, FVIII or FIX concentrations in these blood products were not sufficient to stop serious bleeding and thus most people with severe haemophilia died in childhood or in early adulthood, the most common causes of death being haemorrhages in vital organs, especially in the brain, and bleeding after surgery or trauma^14,15.

Although the discovery in 1964 by Judith Pool that the fraction cryoprecipitated from plasma contained large amounts of FVIII represented an enormous step forward in haemophilia care^14,15, the beginning of the modern management of haemophilia is traditionally referred to the 1970s with the production of lyophilised plasma concentrates of coagulation factors manufactured using Cohn-Oncley fractionation^14–16. Indeed, this technologic innovation greatly improved the quality and expectancy of life of haemophiliacs, as it permitted the widespread adoption of home replacement therapy with the early control of haemorrhages and the reduction of the musculoskeletal damage typical of untreated or poorly treated patients. Specialised haemophilia centres developed programmes of comprehensive care, with the involvement of such specialists as orthopaedic surgeons, physiotherapists and dentists. Elective surgery, particularly orthopaedic operations, became possible and safe, and helped to correct or reduce the musculoskeletal abnormalities that had developed as a consequence of untreated or inadequately treated bleeding episodes into joints and muscles^14,15.

In parallel, prophylaxis (i.e., the regular infusion of factor concentrates in order to prevent joint bleeding and its long-term deleterious effects) was successfully pioneered in Sweden and in the Netherlands and then adopted in other countries, with different regimens but similar evidence that the earlier the start of treatment, the better the outcomes in preventing bleeding episodes, reducing the impact of arthropathy and ultimately improving patients’ quality of life^17,18. Unfortunately, this golden era of the treatment of haemophilia was destined to end rapidly and dramatically during the first part of the 1980s. This was the period of the transmission of the human immunodeficiency (HIV) and hepatitis C (HCV) viruses through contaminated coagulation factor concentrates manufactured from plasma pooled from thousands of donors^14,15. Thousands of persons with haemophilia died of acquired immunodeficiency syndrome (AIDS) in the 1980s and 1990s. As a consequence of the devastating sequelae of the AIDS and hepatitis epidemics, the need for a safe treatment became crucial for the haemophilia community. The implementation of viral inactivation techniques for the production of plasma-derived factor concentrates, as well as the adoption of new methods to screen viruses in blood donations (i.e., Nucleic Acid Testing [NAT]), greatly improved the safety of plasma-derived products, as shown by the fact that blood-borne transmission of hepatitis viruses or HIV have not occurred in the last 20 years^14,19. However, following the cloning of FVIII and FIX genes in 1982 and 1984, the most important advance in this field was represented by the rapid progress in DNA technology, which allowed the industrial production of recombinant FVIII (and subsequently of FIX), culminating with the publication in 1989 of the first report of clinical efficacy of this product in two patients with haemophilia A²⁰. The viral safety of factor concentrates dramatically improved the treatment and quality of life of haemophilia patients and significantly contributed to the diffusion of prophylaxis, with primary prophylaxis (i.e. started in the first years of life, before the onset of irreversible joint damage) clearly recognised as the first-choice treatment in children with severe haemophilia²¹ and increasingly adopted also in adolescent and adult patients²². In parallel, the life span of haemophiliacs has progressively become similar to that of males in the general population, at least in more developed countries^23,24. However, with ageing, persons with haemophilia develop medical and surgical conditions (e.g., cardiovascular diseases, cancers, renal disease) previously rarely seen in this group^25–26, which represent a new challenge for physicians working in haemophilia centers²⁷. Presently, at least in high-income countries with large availability of factor concentrates, the most challenging complication of haemophilia treatment has become the development of inhibitory alloantibodies against FVIII or FIX. Inhibitors, occurring in approximately 25–30% of previously unexposed patients (PUPs) with severe haemophilia A and in 3–5% of those with severe haemophilia B, render replacement treatment partially or completely ineffective and hamper prophylaxis feasibility, thus exposing the patients to an increased risk of morbidity and mortality²⁸.

Factor VIII and factor IX concentrates

A variety of plasma-derived and recombinant concentrates are licensed in Italy for treatment of haemophilia (Table I). Plasma-derived concentrates are classified depending on the modality of purification procedures: intermediate purity products obtained through conventional techniques of precipitation/adsorption, and high-purity concentrates purified through ion exchange chromatography or through monoclonal antibodies¹⁶. As above mentioned, viral inactivation techniques have become integral part of the productive process. The main methods of viral inactivation, compatible with the maintenance of the biological activity of clotting factors and thus applicable to factor concentrate production, are: dry heat, pasteurization, vapour, solvent/detergent. Regarding the sensitivity of such methods, it should be taken in account that while HIV is particularly sensitive to heat treatment, hepatitis viruses necessitate higher temperature for longer periods to be inactivated and non-enveloped viruses (i.e., hepatitis A virus [HAV] and parvovirus B19) are not inactivated by solvent/detergent treatment. Thus, to minimise the viral infective risk, the great majority of producers have adopted two methods of inactivation in the preparation of plasma-derived FVIII and FIX concentrates, associating solvent/detergent methods to heat treatment. In addition, viral elimination techniques of ultrafiltration and nanofiltration, which allow the removal of smaller and non-enveloped viruses, have been implemented in the last years in the preparation of FVIII and FIX concentrates.

Table I.

Factor VIII and factor IX concentrates licensed in Italy (listed in alphabetical order).

Product	Manufacturer	Production characteristics
		Purification	Viral inactivation
Plasma-derived FVIII concentrates
Alphanate®1	Grifols	Heparin ligand chromatography	S/D, dry heat
Beriate®	CSL Behring	Ion exchange chromatography	Pasteurisation
Emoclot D.I.®	Kedrion	Ion exchange chromatography	S/D, dry heat
Fanhdi®1	Grifols	Heparin ligand chromatography	S/D, dry heat
Haemate P®1	CSL Behring	Multiple precipitation	Pasteurisation
Haemoctin®	Biotest	Ion exchange chromatography	S/D, dry heat
Talate®1	Baxter	Ion exchange chromatography	Detergent, vapour
Recombinant FVIII concentrates
Advate®2	Baxter	Immunoaffinity chromatography	S/D
Helixate NexGen®3	CSL Behring	Immunoaffinity chromatography	S/D, ultrafiltration
Kogenate Bayer®3	Bayer Healthcare	Immunoaffinity chromatography	S/D, ultrafiltration
Recombinate®4	Baxter	Immunoaffinity chromatography	-
Refacto AF®5	Pfizer	Immunoaffinity chromatography	S/D, nanofiltration
Plasma-derived FIX concentrates
Aimafix®	Kedrion	Anionic chromatography	S/D, dry heat
Alphanine®	Grifols	Anionic chromatography	S/D, nanofiltration
Haemobionine®	Biotest	Anionic and affinity chromatography	S/D, nanofiltration
FIXnove®	Baxter	Anionic chromatography	Detergent, vapour
Mononine®	CSL Behring	Immunoaffinity chromatography	Sodium tiocianate, ultrafiltration
Recombinant FIX concentrates
Benefix®	Pfizer	Anionic chromatography	Ultrafiltration, nanofiltration

Legend S/D, solvent/detergent.

¹This concentrate is also licensed for treatment of patients with von Willebrand disease;

²Third-generation full-length, produced in chinese hamster ovary (CHO) cells;

³Second-generation full-length, produced in baby hamster kidney (BHK) cells;

⁴First-generation full-length, CHO-derived;

⁵Third-generation B-domain deleted, CHO-derived.

Recombinant DNA technology led to the production of first-generation recombinant FVIII (rFVIII) concentrates from Chinese hamster ovary (CHO) cells or baby hamster kidney (BHK) cells, stabilised with human albumin. BHK-derived rFVIII was then obtained as a second-generation product containing sucrose instead of albumin in the final formulation. The CHO-derived product evolved in a third-generation rFVIII, manufactured without additional human or animal plasma proteins²⁹. Beyond these full-length rFVIII molecules, a B-domain deleted rFVIII was also developed, without affecting its final haemostatic activity. No traces of human or animal protein are contained in the current formulation of this concentrate²⁹. The only recombinant FIX (rFIX) concentrate commercially available is manufactured without additional human or animal plasma proteins³⁰, similar to third-generation rFVIII products. No significant difference in the pharmacokinetic profile is reported between plasma-derived and recombinant FVIII products, whereas in vivo recovery of rFIX is reduced by approximately 30% compared with plasma-derived FIX. As a consequence, larger doses of rFIX than plasma-derived FIX are required for achieving similar plasma levels of FIX³⁰. Viral inactivation/elimination techniques are also utilised in the manufacturing process of rFVIII and rFIX concentrates (Table I).

Some plasma-derived FVIII concentrates containing adequate amounts of VWF are also licensed for treatment of patients with VWD. These products show different VWF:FVIII and VWF Ristocetin Cofactor (VWF:RCo):Antigen (VWF:Ag) ratios. A plasma-derived product with largely predominant VWF content is also available¹³. A recombinant VWF product is presently on investigation, with data of a phase 1 clinical trial recently published³¹.

For a comprehensive list and more details on the characteristics of these and other available FVIII and FIX products, the readers are referred to a recent publication of the World Federation of Hemophilia (WFH)³².

Clinical use of factor VIII and IX concentrates

In the following paragraphs the regimens of replacement treatment in haemophilia and other clinical indications of FVIII and FIX concentrates will be presented.

Regimens of treatment in haemophilia: prophylaxis vs on-demand treatment

With the exception of newborns with bleeding complications at delivery (in particular if intracranial) or of patients experiencing severe traumas or requiring surgery, replacement treatment with FVIII/FIX concentrates in haemophilic children is usually started at the time of the first joint bleed, occurring in most cases before the age of 2 years, when joint mobilisation and load increase⁵. On-demand factor concentrate infusion, which is the treatment in the occurrence of an acute bleeding episode, is able to stop haemorrhage. However, in the case of haemarthrosis, the presence of blood already accumulated into the joint synovial tissues, triggers inflammatory reactions that, in a vicious cycle of recurrent bleeding (“target joint”) and amplification of phenomena, lead to progressive, irreversible damage of cartilage and bone³³. Joint degeneration with function limitations can be documented in more than half of patients within six years from the first bleeding episode¹⁰ and the severity of such abnormalities, evaluated by clinical or radiological scores, is tightly related with the frequency of bleeding episodes^10,18. These observations, together with the recognition that patients with moderate or mild haemophilia (who have FVIII/FIX levels >1%) show a low frequency of joint bleeds and rarely develop severe arthropathy³⁴, provided the rationale for therapeutically converting severe haemophilia to a milder form through a regular, long-term regimen of concentrate infusions, in order to minimise the number of joint bleeds and prevent or reduce the muscle-skeletal impairment²². As above mentioned, since the 1960s different prophylaxis regimens were developed in Northern Europe (high-dose for all patients in Sweden, FVIII 25–40 IU/kg thrice weekly or FIX 30–40 IU/kg twice weekly¹⁷; lower dose in the Netherlands, FVIII 20–40 IU/kg twice or thrice weekly or FIX 30–40 IU/kg once or twice weekly, according to the bleeding tendency¹⁸), followed by other countries, showing clinical and social benefits over on-demand treatment in terms of total and joint bleeding rates and, in particular, of long-term outcomes (arthropathy and patients’ quality of life), with better results in children with earlier start of prophylaxis²². Results from retrospective cohorts of patients were more recently confirmed by two prospective randomised trials with high-dose regimens that definitively provided evidence of “primary” prophylaxis as the first-choice treatment for children with severe haemophilia^21,35. However, benefits of prophylaxis have been recognised even later in life, in reducing the frequency of bleeding and, although less clearly, in improving patients’ joint outcomes and quality of life^36,37. Overall, these findings led to the current definitions of prophylaxis (Table II)¹¹, which reflect a wide spectrum of clinical conditions and objectives of treatment, from the prevention of recurrent or life-threatening bleeds to the complete absence of arthropathy, enabling children to live a substantially normal life, without overprotection^22,38. However, if there is general agreement concerning the early start of prophylaxis in children, the intensity of prophylaxis regimens and how to initiate prophylaxis are still debated³⁹. In this respect, barriers are represented by the need for frequent venous access in small children (leading to the implantation of central venous access devices in many cases) and adequate training of families for home treatment in order to improve adherence to such a demanding treatment³⁹. These problems and differences in patients’ bleeding pattern led to experience tailored regimens, in which dose and/or frequency of infusions is escalated on the basis of the bleeding tendency (like in the Canadian approach⁴⁰) or, as more recently proposed, is driven by the individual pharmacokinetic pattern⁴¹. These regimens seem to be very effective in preventing bleedings and, consequently arthropathy, however data on long-term outcomes, including possible advantages in terms of cost-effectiveness (hoped in the light of the high costs of treatment) are still not available⁴².

Table II.

Definitions of regimens of factor replacement therapy in haemophilia^{^}.

Regimen	Definition
Episodic (on-demand treatment)	Treatment given at the time of clinically evident bleeding
Continuous prophylaxis	Regular continuous* treatment started:
Primary prophylaxis	In the absence of documented osteochondral joint disease, determined by physical examination and/or imaging studies, and started before the second clinically evident large joint** bleed and age 3 years
Secondary prophylaxis	After 2 or more bleeds into large joints** and before the onset of joint disease documented by physical examination and imaging studies
Tertiary prophylaxis	After the onset of joint disease documented by physical examination and plain radiographs of the affected joints
Intermittent (periodic) prophylaxis	Treatment given to prevent bleeding for periods not exceeding 45 weeks in a year

^{^}According to the recommendations of the Subcommittee on factor VIII and factor IX of the Scientific and Standardization Committee of the International Society on Thrombosis and Haemostasis, reported in the Guidelines for the management of hemophilia from the Working Group of the World Federation of Haemophilia¹¹.

^*With the intent of treating for 52 weeks per year and receiving a minimum of an a priori defined frequency of infusions for at least 45 weeks (85%).

^**Large joints: ankles, knees, hips, elbows and shoulders.

Studies specifically focused on prophylaxis in haemophilia B are lacking, due to its lower prevalence and to the general practice of transferring results obtained in patients with haemophilia A. However, a Canadian survey showed that regular prophylaxis was less frequently used in patients with severe haemophilia B than in those with severe haemophilia A (overall 32% vs 69%). This difference was remarkably present in children but detectable in all age subgroups⁴³. This finding, together with other studies reporting lower rates of admissions, bleeding episodes or orthopaedic interventions in patients with haemophilia B than in those with haemophilia A, may suggest different severities of the two forms of haemophilia¹². The lack of prospective data hamper to draw definite conclusions, with the possible therapeutic implications.

In spite of a later implementation than in other countries in Northern Europe, prophylaxis was rapidly spread in Italy, particularly after the advent of recombinant products⁴⁴, and is presently adopted in the large majority of patients with severe haemophilia (89%)⁴⁵. Indeed, beyond the well-known benefits in children (the ESPRIT, the randomised trial of prophylaxis in children with the longest -10 years- follow-up, was carried out in Italy³⁵), a large clinical experience of secondary and tertiary prophylaxis has been achieved and published, documenting the global positive impact in terms of bleeding rates, joint status and quality of life even in adult patients, although costs of treatment are remarkably increased^36,46.

Treatment of bleeding

In the occurrence of haemorrhages, factor concentrates should be administered as early as possible in order to achieve haemostatic levels of the missing coagulation proteins, until the complete resolution of bleeding. Doses and intervals of infusions are different in patients with haemophilia A and B, taking into account the specific pharmacokinetic profiles of FVIII and FIX concentrates. Indeed, the half-life of FVIII is approximately 8–12 hours and, in the absence of inhibitors, each unit per kilogram body weight of a FVIII concentrate intravenously administered will raise FVIII plasma levels of approximately 2 IU/dL. On the other hand, the half-life of FIX is longer, approximately 18–24 hours, and the increase in plasma levels after the infusion of each unit per kilogram body weight of a FIX concentrate lower, approximately 1 IU/dL¹¹. Moreover, the dose of factor concentrates to be administered should consider the severity and site of bleeding, together with the baseline factor level of the patient, in order to raise plasma levels suitably. However, in spite of decades of clinical experience, optimal haemostatic levels and protocols of treatment remain largely empiric, even in the case of the most common bleeding manifestation, haemarthrosis⁴⁷. Many national and international scientific societies, including the Italian Association of Haemophilia Centres (AICE)⁴⁸, published recommendations for replacement treatment in the different clinical settings of bleeding, as summarised in Table III. In the recent update of WFH recommendations, desired factor levels and duration of treatment are differentiated according to the availability of factor concentrates and economic resources (in the presence of significant constraint or not)¹¹.

Table III.

Recommended doses of FVIII and FIX concentrates for the treatment/prevention of bleeding in haemophilia A and B.

Clinical setting	Haemophilia A FVIII dose (IU/kg)	Haemophilia B FIX dose (IU/kg)
Mild/moderate haemarthroses or haematomas	20–30	20–40
Severe haemarthroses or haematomas External bleeding with anaemia Moderate post-traumatic bleeding	30–50	40–60
Cranial trauma Cerebral haemorrhage	50–100	50–100
Surgery prophylaxis	50–100^	50–100^
Primary prophylaxis	25–30 (three times per week)	30–40 (two times per week)

^*From the Italian guidelines on replacement therapy for haemophilia⁴⁸.

^{^}Maintain FVIII/FIX levels above 50% for 7–15 days after surgery.

Surgery and invasive procedures

Replacement treatment with FVIII or FIX concentrates should be administered to cover the haemorrhagic risk related to surgery and other invasive procedures, not only in the operative period, but until the complete wound healing. Doses and interval of concentrate administrations are calculated as above mentioned, however taking into account the individual pharmacokinetic profile is suggested, in particular in the case of major surgery^11,49. Virtually normal FVIII/FIX are desired on the day of the procedure and in the immediately following post-operative days in patients undergoing major procedures. Lower levels, but at least 50 IU/dL, are suggested thereafter and in the case of minor interventions, with a duration of treatment depending on the type of procedures^11,49. Again, although many reports are available in the literature in different settings of surgical and invasive procedures (in particular orthopaedic surgery, liver biopsy, dental surgery and indwelling central venous catheter insertion, the most common procedures in haemophiliacs), few randomised studies have been carried out and current recommendations are based on clinical practice and expert panel consensus⁴⁹. In particular in the surgical setting, some studies evaluated the administration of factor concentrates by continuous infusion (CI). The stability of plasma factor levels by CI may represent an advantage, eliminating unnecessary factor peak levels, immediately after the bolus infusions, and the trough levels, possibly at risk of inadequate haemostatic coverage. Moreover, CI might considerably reduce the overall factor concentrate required, thus resulting more cost-effective than bolus administration, in particular when an “adjusted dose” in accordance with the factor daily clearance is used^49,50. This approach, requiring careful monitoring and expertise, is presently limited to highly specialised centres.

Immune tolerance induction (ITI)

Since the late 1970s the regular and prolonged administration of factor concentrates was shown to restore immune tolerance and clinical response to the standard replacement treatment in patients with inhibitors. This therapeutic approach, known as ITI, is presently the only strategy able to eradicate inhibitors and is attempted in most children as soon as possible after inhibitor diagnosis, in order to avoid the morbidity burden of persistent inhibitors, in particular on joint health⁵¹. High success rates (60–80%) have been reported with heterogeneous ITI protocols (dose and type of concentrate, interval of infusions, association of immunomodulating agents), mostly in retrospective studies or registries^51,52. Also in this case, the majority of studies have been carried out in patients with haemophilia A, not only because of the higher prevalence of FVIII inhibitors. Indeed, ITI is rarely attempted in patients with FIX inhibitors, due to the association with severe anaphylactic reactions at FIX re-exposure⁵¹. Recently, a randomised trial confirmed that similar success rates are obtained with a high-dose (200 IU/kg daily) and a low-dose (50 IU/kg thrice weekly) FVIII regimen in “good-prognosis” children (i.e. those aged <8 yrs, with a historical inhibitor peak titre lower than 200 BU/mL and starting ITI when inhibitor titre is lower than 10 BU/mL, within 24 months from inhibitor detection). However, significantly higher rates of bleeding episodes reported in patients on the low-dose arm of the study presently raise concerns for choosing such regimen in good-risk children⁵³. Even more debated is the optimal approach in poor-risk patients, in particular in adults with long-standing inhibitors. Indeed, the cost-utility of ITI is easily perceived in children in the perspective of the high success rate and the prevention of joint deterioration, which enable to predict a considerable long-term reduction of costs in the majority of treated patients⁵⁴. A careful, individual risk-benefit assessment, taking into account the bleeding phenotype and the bleeding risk related to possible surgical indications and co-morbidities, is needed in poor-risk patients⁵². High-dose or lower-dose (100 IU/kg) but daily regimens are most frequently used in Italy, as documented by the national ITI registry collecting data between 1998 and 2009⁵⁵.

Plasma-derived FVIII concentrates in VWD

As mentioned above, four plasma-derived FVIII concentrates (Table I) are licensed in Italy for treatment of VWD patients who are unresponsive or insufficiently responsive to desmopressin (severe type 1, most type 2, all type 3)¹³. At variance with haemophilic patients, because of different bleeding pattern and sequelae of haemorrhages, the large majority of VWD patients receive replacement treatment on demand, for treating spontaneous bleeding episodes or for preventing bleeding during surgical or invasive procedures. Dosages given once daily or every other day from 20 to 60 IU/kg of VWF:RCo/FVIII (depending on the risk and severity of bleeding) are considered haemostatically effective. As these concentrates are labeled in terms of FVIII content, the VWF:RCo/FVIII ratio of the specific product should be taken into account. Indeed, the accumulation of exogenous FVIII, together with that endogenously synthesised and stabilised by the infused VWF, may lead to very high plasma FVIII concentrations when repeated and closely spaced infusions are given for severe bleeding episodes or to cover major surgery¹³. Such high FVIII levels have been associated with the risk of venous thromboembolic episodes, rarely but definitely documented in these conditions⁵⁶. Some patients with severe forms of VWD (i.e., FVIII levels <5 U/dL) show frequent haemarthroses and may therefore benefit from secondary long-term prophylaxis. This regimen should be considered also for patients with recurrent gastrointestinal bleeding or frequent epistaxis. Long-term outcomes and the cost-effectiveness of this approach versus on-demand therapy are still being investigated¹³.

A highly purified plasma VWF concentrate, containing very low FVIII concentration, has been developed for exclusive use in VWD⁵⁷. After the infusion of this product, endogenous FVIII levels rise slowly reaching a peak between 6 and 8 hours, a priming dose of FVIII should be therefore co-administered if prompt haemostasis is required^13,57. This is not necessary in the case of surgery (concentrate infusion is anticipated 6 hours before the procedure) or of regular secondary prophylaxis.

The choice of type of factor concentrate: an open issue

In the current scenario, with the availability of a variety of safe and effective plasma-derived and recombinant products, the choice of the optimal type of product is keenly debated. Over the last two decades, the impact of infectious complications being dramatically reduced, inhibitor development became the most challenging issue in this choice, in particular in patients with haemophilia A. Indeed, some in vitro data and mainly retrospective or uncontrolled studies suggested a lower incidence of inhibitory alloantibodies in patients receiving plasma-derived products, especially single-brand concentrates, compared with recombinant ones^58–60. An ongoing randomised trial, the SIPPET study, will probably clarify this issue⁶¹, however, recent large cohort studies^62,63, the results form a 3-yr prospective European surveillance programme⁶⁴ and a metanalysis of prospective studies in severe patients⁶⁵ failed to show any difference in inhibitor development between plasma-derived and recombinant concentrates.

In spite of the lack of evidence of any major infection transmitted for more than 20 years, the viral safety of plasma-derived concentrates remains matter of concern. Several factors have contributed to the undoubted high degree of safety of these products, including the adoption of the quarantine of the plasma units utilised for industrial fractionation and the introduction of NAT testing for 5 viruses (HIV 1–2, HBV, HCV, HAV and parvovirus B19) for most of the factor concentrates actually commercialised. Moreover, an essential role has to be attributed to viral inactivation/elimination techniques, currently combined to minimise the viral infective risk in the majority of plasma-derived products (solvent/detergent associated with heat treatment in FVIII concentrates and with nanofiltration for the smaller FIX molecule). However, some sentinel events should induce to maintain high the level of guard. This is the case of the documented transmission of parvovirus B19 through plasma-derived concentrates^66,67. Although clinical impact of this infectious agent is often minimally relevant, it is however the signal that other, still unknown, clinically more important viruses could be resistant to the currently available viral inactivation techniques and thus infect haemophiliacs through factor concentrates⁶⁸. In addition, the recent report of the autopsy detection of the variant Creutzfeldt-Jacob disease (vCJD) in a neurologically asymptomatic UK haemophiliac infused with FVIII concentrates prepared from plasma pools known to include donations from a donor who subsequently developed vJCD⁶⁹, raised some concerns regarding the possibility of prion transmission through plasma-derived factor concentrates.

In parallel, in spite of the inherent risks of biological products, no safety concern has been raised concerning recombinant products over more than 20 years of clinical use. Moreover, their safety also improved during the last decade. Apart the implementation of viral inactivation/elimination techniques similar to those of plasma-derived products, many efforts have been made by manufacturers for the progressive removal of human and animal proteins during the productive process and in the final formulation²⁹. For these reasons, although higher costs are challenging in the current economic scenario, many haemophilia specialists consider recombinant concentrates the first-choice products, in particular in children, and this choice is supported by a series of national recommendations^70–72, including the Italian guidelines⁴⁸. Although the latter were published in 2000 and updated in 2003, a very recent survey among the Directors of Italian haemophilia centres showed that for the large majority of respondents (approximately 80%) the choice of the type of concentrate is still dictated by safety concerns rather than by the immunogenicity of the different products and almost all (96%) prescribe recombinant products in PUPs⁷³. Consistently, approximately 80% of FVIII and FIX concentrates utilised by Italian haemophiliacs are recombinant products⁴⁵.

Conclusions

From the analysis of the literature data, it clearly emerges that nowadays replacement therapy for haemophilia has reached a high degree of quality thanks to the availability of a series of effective and safe plasma-derived or recombinant products. The diffusion of early prophylaxis presently enables children with severe haemophilia to achieve an excellent quality of life, without significant physical and psychological restrictions. The increasing use of secondary and tertiary prophylaxis is reducing joint morbidity and improving quality of life even later in life. Strategies for reducing the high costs of treatment, preserving its high quality are being investigated, in particular individually “tailored” approaches. Unsolved problems remain inhibitor development and the need for venous access, challenging in particular in small children at start of prophylaxis or in those undergoing ITI. In this respect, research is now directed towards the development of modified molecules (again thanks to recombinant technologies) with reduced immunogenicity or with longer half-life. The latter products are in an advanced phase of clinical investigation and encouraging results have been achieved in particular for factor IX concentrates¹⁵.