Recent advances in the development of coagulation factors and procoagulants for the treatment of hemophilia

Hemophilia is a family of rare bleeding disorders. The two primary types, hemophilia A and hemophilia B, are caused by recessive X-chromosome linked mutations that result in deficiency of coagulation factor VIII (FVIII) or factor IX (FIX), respectively. Clinically, hemophilia is manifested by spontaneous bleeding, particularly into the joints (haemarthrosis) and soft tissue, and excessive bleeding following trauma or surgery. The total overall number of hemophilia patients worldwide is approximately 400,000, however only about 100,000 of these individuals are treated. The first treatment of hemophilia was initiated when it was determined that the clotting deficiency could be corrected by a plasma fraction taken from normal blood. The discovery of factor VIII enrichment by cryoprecipitation of plasma opened a new era of therapy which eventually led to the production of factor concentrates and the subsequent development of highly purified forms of plasma factors. The most significant improvements have been the availability of recombinant forms of factors VIII and IX. Unfortunately, recombinant factors still retain some of the limitations of plasma concentrates. These limitations include development of antibody responses in patients and the relatively short half-life of the molecules requiring frequent injection to maintain effective concentration. Treatment beyond replacement of native factors has been tried. They include the development of modified factor VIII and IX molecules with improved potency, stability and circulating half-life and enhancement of a prothrombotic responses and/or stabilization of coagulation factors via inhibition of key negative regulatory pathways. These approaches will be reviewed in this commentary.     

Treatment strategies in children with hemophilia

Hemophilia is an inherited bleeding disorder caused by quantitative or qualitative defects in the synthesis of factor VIII (FVIII) or factor IX (FIX). Clinically, it is divided into severe, moderate and mild disease depending on the levels of FVIII or FIX in the blood. The bleeding tendency is most pronounced and can start at a very young age in severe hemophilia, which is characterized by repeated hemorrhage into the joints and muscles. Without treatment, these episodes lead to severe arthropathy, and there is also a high risk of lethal cerebral hemorrhage. The treatment of bleeding symptoms requires the correction of the coagulation defect. Factor concentrates have been available for 30 years, initially with the development of cryoprecipitate, subsequently with increasingly purified plasma-derived forms, and ultimately with recombinant clotting factor concentrates. The advantage of this highly effective therapy has been subdued by the outbreak of HIV and Hepatitis C infections in patients with hemophilia treated with factor concentrates which did not have adequate viral inactivation steps in the purification process. Plasma-derived and recombinant factor concentrates are today considered to have a good safety profile, but are only available for a small group of hemophilia patients worldwide. A multidisciplinary team approach is important for early diagnosis, communication with the patient and parents, and to tailor the best treatment possible with the amount of clotting factor concentrates available. The main goal of hemophilia treatment is to prevent bleeding symptoms and allow normal integration in social life. In patients with severe hemophilia, this can best be achieved by early home treatment and primary prophylaxis. Future developments in gene therapy may transform severe hemophilia to a mild form, with no need for regular injections of clotting factor concentrates.     

The safety of pharmacologic options for the treatment of persons with hemophilia

ABSTRACT

Introduction: The mainstay of treatment of hemophilia A and B is the replacement of the congenitally deficient coagulation factor through the intravenous infusion of specific concentrates (factor VIII, FVIII, in hemophilia A; factor IX, FIX, in hemophilia B). Several commercial brands of FVIII or FIX products extracted from human plasma or engineered using recombinant DNA technology are available.

Areas covered: We analyze the safety aspects of plasma-derived and recombinant FVIII and FIX products licensed in Europe, focusing on their pathogen safety and inhibitor and thrombosis risks. The safety aspects of bypassing agents (i.e., activated prothrombin complex concentrates and recombinant activated factor VII) used for treatment of bleeding episodes in inhibitor patients will be also briefly discussed.

Expert opinion: The analysis of the published literature documents the high degree of safety from pathogen risk for both plasma-derived and recombinant products available for hemophilia treatment. The main threat to factor concentrate safety is represented by the development of neutralizing alloantibodies against the infused coagulation factor, which in hemophilia A seem to occur more frequently following the administration of recombinant than plasma-derived FVIII products. Great expectations are placed on newer products, particularly on those based upon mechanisms of action other than FVIII replacement.     

Access to treatment among persons with hemophilia: A spatial analysis assessment in the Rhone-Alpes region,France

ObjectivesIn France, only hospital pharmacies can dispense clotting factor concentrates to persons with hemophilia, which limits the access to care for the treatment and the prevention of bleeding episodes. Moreover, the cost of clotting factor concentrates may restrain the maintenance of sufficient stocks in hospital pharmacies. The aim of this study was to investigate the accessibility of clotting factor concentrates to persons with hemophilia in the context of long-term prophylaxis and emergency treatment in the Rhone-Alpes region of France.MethodsA geographic information system was used for evaluating accessibility of clotting factor concentrates. Persons with hemophilia and hospital pharmacies were geolocalized with the use of postal data, and the evaluation of accessibility was based on the road network.ResultsApproximately 72% of the study area was accessible in less than 30 minutes to a hospital pharmacy. Eighty-five percent of persons with hemophilia had access to clotting factor concentrates for prophylactic treatment in less than 20 minutes. Most of them were patients with severe or moderate hemophilia. Regarding emergency doses, factor VIII was accessible in less than 30 minutes in 45.6% of the study area, and factor IX in 30.5%.ConclusionThis study highlights that spatial access to clotting factor concentrates by persons with hemophilia in the Rhône-Alpes region is good for prophylactic treatment but is more uneven for emergency doses.     

Gene therapy for hereditary hematological disorders

The year 2000 saw the first successful treatment of a genetic disorder by gene therapy. Pediatric patients with X-linked severe combined immunodeficiency disorder (SCID-X1) received autologous CD34+ hematopoietic cells following ex vivo gene transfer using a retroviral vector, with subsequent demonstration of improved immune responses. A number of preclinical and clinical studies have been conducted with the aim of developing gene therapy for hemophilia, Fanconi anemia, sickle cell disease, beta-thalassemia, chronic granulomatous disease, and other inherited hematological disorders. The greatest advances in novel approaches toward treatment of hematological disorders have been made in hemophilia, with 3 current phase I clinical trials ongoing. Two trials are investigating the safety and feasibility of utilizing either an ex vivo, non-viral gene transfer technique or an intravenous infusion of a retroviral vector to treat adults with severe hemophilia A (factor VIII deficiency). The third study involves intramuscular administration of an adeno-associated viral (AAV) vector for expression of factor IX in adult patients with hemophilia B. Results from this study and from preclinical studies preceding the trial demonstrate that it is possible to safely administer high doses of a viral vector in vivo.     

Coagulation products and their uses.

The indications, pharmacokinetics, and therapeutic guidelines for available coagulation products are reviewed. Patients with hemophilia, von Willebrand's disease (VWD), or acquired inhibitors to antihemophilic factor (AHF) cannot spontaneously stop an acute hemorrhage. Coagulation products used to manage bleeding in patients with these disorders include AHF concentrates, factor IX concentrates, factor VIIa concentrate, factor IX complexes, anti-inhibitor coagulant complexes, and desmopressin acetate. Typically, these commercially available products are used to manage acute bleeding or to prevent excessive bleeding during surgery. The dosage of the coagulation products and the duration of therapy depend on many variables, including the severity of the hemorrhage, the pharmacokinetics of the coagulation products, and patient-specific factors. Product purity and viral attenuation are also important considerations in determining an appropriate dosage regimen. Recombinant versions of some coagulant factors are available and can eliminate the risk of viral transmission. A thorough understanding of each coagulation product can guide product selection, dosing, and treatment duration and can reduce the risk of viral transmission.     

FVIII at the crossroad of coagulation,bone and immune biology: Emerging evidence of biological activities beyond hemostasis

Hemophilia A is an X-linked hereditary disorder that results from deficient coagulation factor VIII (FVIII) activity, leading to spontaneous bleeding episodes, particularly in joints and muscles. FVIII deficiency has been associated with altered bone remodeling, dysregulated macrophage polarization, and inflammatory processes that are associated with the neoformation of abnormal blood vessels. Treatment based on FVIII replacement can lead to the development of inhibitors that render FVIII concentrate infusion ineffective. In this context, hemophilia has entered a new therapeutic era with the development of new drugs, such as emicizumab, that seek to restore the hemostatic balance by bypassing pathologically acquired antibodies. We discuss the potential extrahemostatic functions of FVIII that may be crucial for defining future therapies in hemophilia.     

Novel therapeutic agents in the management of hemorrhage and thrombosis

Abnormalities in the hemostatic system can lead to, on one end of the spectrum, hemorrhage, and on the opposite end, thrombosis. Over the past decade, important new agents for the management of hemorrhagic and thrombotic disorders have been developed and more are in development. The care of patients with bleeding disorders has been advanced by the development of techniques to manufacture recombinant factor products with reduced or absent exposure to human or animal proteins, prolonged half-life or with reduced immunogenicity. Though first developed for use in hemophiliacs with inhibitors, recombinant factor VIIa (rFVIIa) has now garnered experience in a variety of settings of inherited and acquired bleeding disorders. Thrombosis can occur in a variety of vascular beds and cause a spectrum of clinical sequelae. Depending on whether the thrombosis is venous or arterial, major therapeutic targets are platelets and procoagulant clotting factors. Novel targets on the platelet surface include the thrombin protease activated receptors (PAR) and the collagen receptor, glycoprotein VI (GPVI). In animal models, PAR1 and GPVI inhibition have both demonstrated a protective effect against arterial thromboembolism. For many years, the only agents available to inhibit procoagulant clotting factors were heparin and warfarin. The recent development of a pentasaccharide and other agents targeting factor Xa, factor IX, and thrombin offer useful alternatives for the management of arterial and venous thrombosis. These agents and others will be discussed in detail with respect to mechanism of action, clinical efficacy and safety.     

Haemophilia B: current pharmacotherapy and future directions

Introduction: Hemophilia B is a rare hereditary hemorrhagic disorder characterized by deficiency of the clotting factor IX (FIX). Hemophilia B patients experience mild to severe bleeding complications according to the degree of FIX defect. Nowadays, the most challenging complication of individuals with hemophilia B is the development of alloantibodies, which render the standard replacement therapy with FIX concentrates ineffective, exposing them to a significantly increased morbidity and mortality. Areas covered: This review summarizes the most important events leading to the development of the current FIX products available for the treatment of hemophilia B patients. In addition, it focuses on the more recent advances in the production of new FIX molecules aimed at improving the clinical management of such patients. Expert opinion: Although the availability of plasma-derived FIX concentrates has greatly improved the clinical management of hemophilia B patients, the introduction of FIX products using recombinant DNA technology has represented the most significant therapeutic progress in hemophilia B therapy, ensuring an advanced level of safety. The development of rFIX products with extended half lives will further improve the therapeutic armamentarium for hemophilia B patients.     

Current options and new developments in the treatment of haemophilia

Haemophilia A and B are X-linked bleeding disorders due to the inherited deficiency of factor VIII or factor IX, respectively. Of the approximately 1 per 5000-10000 male births affected by haemophilia, 80% are deficient in factor VIII and 20% are deficient in factor IX. Haemophilia is characterized by spontaneous and provoked joint, muscle, gastrointestinal and CNS bleeding leading to major morbidity and even mortality if left untreated or under-treated. The evolution of haemophilia management has been marked by tragedy and triumph over recent decades. Clotting factors and replacement strategies continue to evolve for patients without inhibitors. For patients with an inhibitor, factor replacement for acute bleeding episodes and immune tolerance, immune modulation and extracorporeal methods for inhibitor reduction are the cornerstone of care. In addition, adjuvant therapies such as desmopressin, antifibrinolytics and topical agents also contribute to improved outcomes for patients with and without inhibitors. The future direction of haemophilia care is promising with new longer-acting clotting factors and genetic therapies, including gene transfer and premature termination codon suppressors. With these current and future treatment modalities, the morbidity and mortality rates in patients with haemophilia certainly will continue to improve.     

Chimeric proteins comprising the constant region of immunoglobulins for treating hemophilia B (WO2005001025)

The application (WO2005001025) details recombinant fusion proteins attached to the constant region of heavy chains of immunoglobulins. They are found to be particularly useful for the treatment of hemostatic disorders, such as hemophilia B. It aims at engineering chimeric proteins comprising of a single molecule of human factor IX (FIX) and the constant region (Fc domain) of one or two heavy chain(s) of human IgG (rFIXFc). cDNA for rFIXFc was generated by a PCR. rFIXFc protein was isolated and purified from stably transfected mammalian cells. The concentration and clotting activity of rFIXFc were assessed in mice, rats, monkeys, and FIX-deficient mice and dogs, after intravenous administration. The half-life of rFIXFc activity is prolonged by three to fourfold, compared with rFIX, when administered intravenously in all animals. The generation of chimeric proteins, comprised of FIX fused to the Fc domain of IgG, extends the clotting activity of the recombinant molecule. rFIXFc represents a promising candidate for the treatment of patients with hemophilia B. The application claims the methods of making recombinant chimeric proteins comprising of one biologically active molecule fused to the Fc region of the heavy chain(s) of immunoglobulins and their use for therapy.     

Chimeric proteins comprising the constant region of immunoglobulins for treating hemophilia B (WO2005001025)

The application (WO2005001025) details recombinant fusion proteins attached to the constant region of heavy chains of immunoglobulins. They are found to be particularly useful for the treatment of hemostatic disorders, such as hemophilia B. It aims at engineering chimeric proteins comprising of a single molecule of human factor IX (FIX) and the constant region (Fc domain) of one or two heavy chain(s) of human IgG (rFIXFc). cDNA for rFIXFc was generated by a PCR. rFIXFc protein was isolated and purified from stably transfected mammalian cells. The concentration and clotting activity of rFIXFc were assessed in mice, rats, monkeys, and FIX-deficient mice and dogs, after intravenous administration. The half-life of rFIXFc activity is prolonged by three to fourfold, compared with rFIX, when administered intravenously in all animals. The generation of chimeric proteins, comprised of FIX fused to the Fc domain of IgG, extends the clotting activity of the recombinant molecule. rFIXFc represents a promising candidate for the treatment of patients with hemophilia B. The application claims the methods of making recombinant chimeric proteins comprising of one biologically active molecule fused to the Fc region of the heavy chain(s) of immunoglobulins and their use for therapy.     

Safety of recombinant coagulation factors in treating hemophilia

Introduction: During the last decade, new FVIII/IX concentrates have been developed for the treatment of patients affected by hemophilia A/B. Significant progress has been achieved regarding their half-life, but the old issue of immunogenicity and new concerns about safety need to be addressed.

Areas covered: After the implementation of virucidal methods, both plasma-derived and recombinant clotting factor concentrates achieved a very safe profile. The development of anti-FVIII antibodies is the major adverse event of replacement therapy with both FVIII concentrates. Furthermore, the new extended half-life concentrates, protein fused or pegylated, raised some concerns about their side effects.

Expert Opinion: The treatment of hemophilia A with inhibitors by induction of immunotolerance and using by-passing concentrates, improved the quality of life of patients but did not allow them to have a life expectancy like that of patients without inhibitors. The new humanized monoclonal antibody (MAb) ACE910, mimicking FVIII function, seems to be able to reduce the bleedings of hemophilia A patients with inhibitors. The post-marketing surveillance will clarify if the adverse events observed during the phase III clinical trials and compassionate use were due to the association with a Prothrombin activated complex concentrate or to the prothrombotic effect of the drug itself.     

Emerging drugs for the treatment of hemophilia A and B

Introduction: Replacement therapy with clotting factor concentrates is the most appropriate and effective way to treat bleedings of Hemophilia A&B to prevent chronic arthropathy. Unfortunately, the short half-life (HL) of FVIII/IX concentrates obliges the patients to receive frequent infusions, a big concern for children. The development of inhibitors in about 30–45% of hemophilia A and in 3–5% of hemophilia B patient is the major adverse event of replacement therapy.

Areas covered: In the last few years, new rFIX have been developed with HL. New rFVIII concentrates are displaying small increase of PK characteristics. The new bio-engineering methods allowed the production of molecules fused with Fc fragment of IgG or Albumin or linked to PEG. A new approach to improve hemostasis is represented by Mab against TFPI and small RNA interfering with Antithrombin synthesis. Another innovative drug seems to be the new bi-specific antibody which mimics FVIII function in linking FXa and FX to tenase production.

Expert opinion: The emerging drugs for hemophilia treatment seem to be very promising. The extended half-life will improve the adherence of patients to therapy. Accurate post-marketing surveillance studies will be necessary to check the efficacy, safety and immunogenicity of these new molecules.     

Haemophilia B: current pharmacotherapy and future directions

Introduction: Hemophilia B is a rare hereditary hemorrhagic disorder characterized by deficiency of the clotting factor IX (FIX). Hemophilia B patients experience mild to severe bleeding complications according to the degree of FIX defect. Nowadays, the most challenging complication of individuals with hemophilia B is the development of alloantibodies, which render the standard replacement therapy with FIX concentrates ineffective, exposing them to a significantly increased morbidity and mortality.

Areas covered: This review summarizes the most important events leading to the development of the current FIX products available for the treatment of hemophilia B patients. In addition, it focuses on the more recent advances in the production of new FIX molecules aimed at improving the clinical management of such patients.

Expert opinion: Although the availability of plasma-derived FIX concentrates has greatly improved the clinical management of hemophilia B patients, the introduction of FIX products using recombinant DNA technology has represented the most significant therapeutic progress in hemophilia B therapy, ensuring an advanced level of safety. The development of rFIX products with extended half lives will further improve the therapeutic armamentarium for hemophilia B patients.     

Safety of the new generation recombinant factor concentrates

Haemophilia A and B are X-linked disorders resulting from deficiency of Factor VIII and IX, respectively. Clinical sequellae of Factor VIII or IX deficiency include spontaneous and traumatic haemorrhages into joints, soft tissues, and muscles. The cornerstone of therapy has been replacement of the deficient factor, historically with pooled-plasma derivatives. The unfortunate blood-borne infection transmission (such as HIV, hepatitis B and C viruses), inhibitor formation, immunosuppression, and, in certain cases, thrombosis by these products has spawned major advances and innovations in the manufacture of clotting products. Recombinant technology has virtually eliminated transmissible disease risk; yet, the presence of albumin in second and third generation recombinant products raises, at the least, theoretical risk of prions and parvovirus B19. Other non-infectious complications, including inhibitor formation, allergic reactions, and thrombosis, remain formidable concerns. Despite this, recombinant factors remain the most attractive treatment approach for haemophilia. Future improvement awaits the development of safe and effective gene transfer technology.     

Safety of the new generation recombinant factor concentrates

Haemophilia A and B are X-linked disorders resulting from deficiency of Factor VIII and IX, respectively. Clinical sequellae of Factor VIII or IX deficiency include spontaneous and traumatic haemorrhages into joints, soft tissues, and muscles. The cornerstone of therapy has been replacement of the deficient factor, historically with pooled-plasma derivatives. The unfortunate blood-borne infection transmission (such as HIV, hepatitis B and C viruses), inhibitor formation, immunosuppression, and, in certain cases, thrombosis by these products has spawned major advances and innovations in the manufacture of clotting products. Recombinant technology has virtually eliminated transmissible disease risk; yet, the presence of albumin in second and third generation recombinant products raises, at the least, theoretical risk of prions and parvovirus B19. Other non-infectious complications, including inhibitor formation, allergic reactions, and thrombosis, remain formidable concerns. Despite this, recombinant factors remain the most attractive treatment approach for haemophilia. Future improvement awaits the development of safe and effective gene transfer technology.     

Pharmacokinetic drug evaluation of albutrepenonacog alfa (CSL654) for the treatment of hemophilia

Introduction: Replacement therapy for FVIII/IX in hemophilia A/B is more than 50 years old following the discovery of cryoprecipitate by Judith Pool in 1964. On-demand therapy and prophylaxis to treat or prevent bleedings is very demanding owing to the short half-life (HL) of factor concentrates (no more than 12–14 h for FVIII or 16–18 h for FIX). Patients are very eager to prolong the intervals between bolus. The enhanced HL of long-acting recombinant FIX (rFIX) concentrates seems to fulfill this expectance.

Areas covered: Great improvements have been achieved in the bio-engineering of new rFIX concentrates. Production, formulation, pharmacokinetics, pharmacodynamics, efficacy and tolerability of albutrepenonacog alfa (rIX-FP, trade name Idelvion) will be addressed. rIX-FP is produced by expression of genetically linked FIX and albumin in Chinese Hamster Ovary cells. rIX-FP exhibits a long HL, low clearance and small volume of distribution.

Expert opinion: There is no doubt that rIX-FP, as well as other long-acting rFIX concentrates, will facilitate and improve the adherence to therapy of younger hemophilia patients, toddlers and children. Efficacy, safety and immunogenicity of rIX-FP must be assessed not only during the regulatory clinical trials but also by post-marketing surveillance.     

DDAVP in the treatment of bleeding disorders

Hemophilia A and von Willebrand's disease are hereditary disorders associated with qualitative and quantitative abnormalities of clotting factor VIII. A major clinical feature is excessive or abnormal bleeding often necessitating the use of transfusions of pooled blood products to achieve hemostasis. Exposure to blood products places the recipient at risk for infection by the hepatitis B virus or the human immunodeficiency virus. A synthetic analog of arginine vasopressin, 1-desamino-8-D-arginine vasopressin, has been shown to increase the plasma levels of factor VIII coagulant activity and von Willebrand's factor, and clinically to improve abnormal bleeding, obviating the need to use blood products.     

Inhibition of plasma coagulation through interaction between oxidized low-density lipoprotein and blood coagulation factor VIII

Oxidatively modified low-density lipoprotein (OxLDL) is present in atherosclerotic lesions and has been proposed to play an important role in atherogenesis. Thrombosis is the major mechanism underlying acute complications of atherosclerosis. In the present study, we analyzed the interaction between OxLDL and blood coagulation factors, which are involved in the blood coagulation pathway. We investigated the effect of OxLDL on plasma coagulation by measuring prothrombin time (PT) as a parameter of the extrinsic pathway of blood coagulation and activated partial thromboplastin time (APTT) as a parameter of the intrinsic pathway of blood coagulation following the addition of OxLDL to plasma. OxLDL, but not native LDL, caused prolongation of APTT in a dose- and oxidation time-dependent manner. In addition, the oxidatively modified product of acetylated LDL (AcLDL), but not AcLDL, also caused prolongation of APTT. The inhibition of lysophosphatidylcholine production in OxLDL by phenylmethylsulfonyl fluoride or Pefabloc pretreatment of LDL resulted in a prolongation of APTT, which was equivalent to the effect of OxLDL. Moreover, OxLDL significantly inhibited blood coagulation factor VIII, IX, and XI activity. Furthermore, we demonstrated that recombinant factor VIII binds to OxLDL and that factor VIII associated with OxLDL is detected in the incubation mixture of OxLDL and plasma. These results indicate that the binding of factor VIII to OxLDL affects the intrinsic pathway of the blood coagulation cascade. The present study suggests that the interaction between OxLDL and factor VIII may provide important information on the initiation and progression of atherosclerosis.