Preclinical evaluation of a next-generation, subcutaneously administered, coagulation factor IX variant, dalcinonacog alfa.

INTRODUCTION: The rapid clearance of factor IX necessitates frequent intravenous administrations to achieve effective prophylaxis for patients with hemophilia B. Subcutaneous administration has historically been limited by low bioavailability and potency. Dalcinonacog alfa was developed using a rational design approach to be a subcutaneously administered, next-generation coagulation prophylactic factor IX therapy. AIM: This study aimed to investigate the pharmacokinetic, pharmacodynamic, and safety profile of dalcinonacog alfa administered subcutaneously in hemophilia B dogs. METHODS: Two hemophilia B dogs received single-dose daily subcutaneous dalcinonacog alfa injections for six days. Factor IX antigen and activity, whole blood clotting time, and activated partial thromboplastin time were measured at various time points. Additionally, safety assessments for clinical adverse events and evaluations of laboratory test results were conducted. RESULTS: There was an increase in plasma factor IX antigen with daily subcutaneous dalcinonacog alfa. Bioavailability of subcutaneous dalcinonacog alfa was 10.3% in hemophilia B dogs. Daily subcutaneous dosing of dalcinonacog alfa demonstrated the effects of bioavailability, time to maximal concentration, and half-life by reaching a steady-state activity sufficient to correct severe hemophilia to normal, after four days. CONCLUSION: The increased potency of dalcinonacog alfa facilitated the initiation and completion of the Phase 1/2 subcutaneous dosing study in individuals with hemophilia B.

Plant-based oral tolerance to hemophilia therapy employs a complex immune regulatory response including LAP+CD4+ T cells.

Coagulation factor replacement therapy for the X-linked bleeding disorder hemophilia is severely complicated by antibody ("inhibitor") formation. We previously found that oral delivery to hemophilic mice of cholera toxin B subunit-coagulation factor fusion proteins expressed in chloroplasts of transgenic plants suppressed inhibitor formation directed against factors VIII and IX and anaphylaxis against factor IX (FIX). This observation and the relatively high concentration of antigen in the chloroplasts prompted us to evaluate the underlying tolerance mechanisms. The combination of oral delivery of bioencapsulated FIX and intravenous replacement therapy induced a complex, interleukin-10 (IL-10)-dependent, antigen-specific systemic immune suppression of pathogenic antibody formation (immunoglobulin [Ig] 1/inhibitors, IgE) in hemophilia B mice. Tolerance induction was also successful in preimmune mice but required prolonged oral delivery once replacement therapy was resumed. Orally delivered antigen, initially targeted to epithelial cells, was taken up by dendritic cells throughout the small intestine and additionally by F4/80(+) cells in the duodenum. Consistent with the immunomodulatory responses, frequencies of tolerogenic CD103(+) and plasmacytoid dendritic cells were increased. Ultimately, latency-associated peptide expressing CD4(+) regulatory T cells (CD4(+)CD25(-)LAP(+) cells with upregulated IL-10 and transforming growth factor-ß (TGF-ß) expression) as well as conventional CD4(+)CD25(+) regulatory T cells systemically suppressed anti-FIX responses.

Prothrombin complex concentrates as reversal agents for new oral anticoagulants: lessons from preclinical studies with Beriplex.

Although new oral anticoagulants (NOACs) represent an advance in anticoagulant therapy over vitamin K antagonists (VKAs), they nevertheless have a low, but significant risk for bleeding complications. Reversal agents for VKAs, such as prothrombin complex concentrates (PCCs), are currently being evaluated in preclinical studies for NOAC reversal. This article reviews the preclinical data for the most extensively studied PCC for NOAC reversal, Beriplex, a 4-factor PCC. The results from the Beriplex studies are also compared with those obtained with other reversal agents, including different nonactivated PCCs, activated PCCs, and recombinant activated factor VII.

Current management of the hemophilic child: a demanding interlocutor. Quality of life and adequate cost-efficacy analysis.

Hemophilias are the most known inherited bleeding disorders. The challenges in the management of hemophilic children are different from those in adults: prophylaxis regimen removed the hallmark of crippling disease with lifelong disabilities; individualized regimens are being implemented in order to overcome venous access problems. Presently, at least in high-income countries, advances in treatment of hemophilia resulted in continuous improvement of the patients' quality of life and life expectancy. Inhibitors remain the most severe complication of hemophilia therapy. The treatment' compliance is the key to achieve a successful management. The patient, his family, the medical and psychological team are the players of a comprehensive care system. The current management of hemophilic children is the example of huge resource investments enabling long-term benefits in particular quality of life as a primary objective of the healthcare process.

Preclinical safety and efficacy of a new recombinant FIX drug product for treatment of hemophilia B.

Baxter has developed a new recombinant factor IX (rFIX) drug product (BAX326) for treating patients with hemophilia B, or congenital FIX deficiency. An extensive preclinical program evaluated the pharmacokinetics, efficacy, and safety of BAX326 in different species. The efficacy of BAX326 was tested in three mouse models of primary pharmacodynamics: tail-tip bleeding, carotid occlusion, and thrombelastography. The pharmacokinetics was evaluated after a single intravenous bolus injection in mice, rats, and macaques. Toxicity was assessed in rats and macaques, safety pharmacology in rabbits and macaques, and immunogenicity in mice. BAX326 was shown to be efficacious in all three primary pharmacodynamic studies (P ≤ 0.0076). Hemostatic efficacy was dose related and similar for the three lots tested. Pharmacokinetic results showed that rFIX activity and rFIX antigen concentrations declined in a bi-phasic manner, similar to a previously licensed rFIX product. BAX326 was well tolerated in rabbits and macaques at all dose levels; no thrombogenic events and no adverse clinical, respiratory, or cardiovascular effects occurred. BAX326 was also shown to have a similar immunogenicity profile to the comparator rFIX product in mice. These results demonstrate that BAX326 has a favorable preclinical safety and efficacy profile, predictive of a comparable effect to that of the previously licensed rFIX in humans.

Prophylaxis for severe haemophilia: clinical challenges in the absence as well as in the presence of inhibitors.

Prophylaxis is defined as the regular administration of clotting factor concentrates to prevent bleeding. Extensive data from observational studies and a recent randomized controlled trial (have established that early prophylactic treatment prevents bleeds and arthropathy in boys with severe haemophilia. The initiation of prophylaxis in young children remains challenging. To prevent arthropathy, prophylaxis should be started early, before the onset of joint damage. Alternative strategies of starting include starting before the age of 2 years, or starting before the third joint bleed. Dose and frequency vary between the original Swedish regime of 20-40 IU kg(-1) three times per week and lower dosed and step up regimes starting with 50 IU kg(-1) once weekly and rapidly increasing dose and frequency in case of bleeds. In the second decade, most patients on prophylaxis learn self-infusion. Self-management warrants confirmation of adequate knowledge of the disease. Increasing self-management concurring with major physical and psychological changes may cause reduced adherence. The challenge is to promote adherence and continue to prevent bleeds during this important period of rapid growth. The third decade of life often represents a change in lifestyle. Patients may get a job and periods of physical activity may be more confined. About two thirds of patients experiment with discontinuing prophylaxis in their early twenties, and 20-30% with mild bleeding patterns switch to on-demand treatment for prolonged periods or even permanently. The challenge is to optimize efficiency by individualizing prophylactic dose and frequency according to lifestyle and bleeding pattern. Inhibitors may develop in up to 30% of patients with severe haemophilia. Especially those with high titre inhibitors are at increased risk of developing target joints and severe arthropathy. The use of prophylactic treatment with bypassing agents in inhibitor patients is increasing. Early studies report in a significant reduction of bleeds, including intracranial bleeds, and improvement in quality of life. Data on results of primary prophylaxis in patients with inhibitors to prevent arthropathy are not yet available.

[A Jehovah's Witness child with hemophilia B and factor IX inhibitors undergoing scoliosis surgery].

PURPOSE: To describe the successful perioperative hemostatic management of a Jehovah's Witness patient with hemophilia B and anaphylactic inhibitors to factor IX, undergoing scoliosis surgery. CLINICAL FEATURES: A 14 (1/2)-yr-old boy with severe hemophilia B who had a history of anaphylactic inhibitors to factor IX was scheduled to undergo corrective scoliosis surgery. He was initially started on epoetin alfa and iron supplementation to maximize preoperative red cell mass. Additionally, he was placed on a desensitization protocol of recombinant coagulation factor IX (rFIX) and was then treated with activated recombinant coagulation factor VII (rFVIIa) during the postoperative period. Tranexamic acid was given concomitantly. The intraoperative blood loss was approximately 350 mL. The nadir hemoglobin concentration was 111 g.L(-1) on postoperative days one and two. On postoperative day 11, the patient was stable and discharged home with a hemoglobin of 138 g.L(-1). He did not require blood transfusion and no adverse events were observed. CONCLUSIONS: The use of rFIX, rFVIIa, erythropoetin, iron, and tranexamic acid before, during and after scoliosis surgery may be a viable and safe option for hemophilia patients with inhibitors, who refuse blood products.

Haemophilic factors produced by transgenic livestock: abundance that can enable alternative therapies worldwide.

Haemophilia replacement factors, both plasma-derived and recombinant, are in relatively short supply and are high-cost products. This has stymied the study and development of alternative methods of administration of haemophilia therapy even in the most economically advanced countries, owing to the large amounts of material needed because bioabsorption and bioavailability of haemophilic factors can be less than 10% when using non-intravenous routes of delivery. There is therefore a need to increase access to therapy worldwide by decreasing the cost and increasing the abundance so that therapy can be achieved through simplified, alternative delivery methods. Transgenic livestock have been used to produce haemophilic factors in milk. Only the pig mammary gland has been shown to carry out the post-translational processing necessary to enable both the biological activity and long circulation half-life needed for therapeutic glycoproteins. Furthermore, the large amounts of recombinant protein that can be produced from pig milk make feasible the use of alternative delivery methods such as oral, intratracheal, subcutaneous, and intramuscular administration.

Preclinical gene therapy studies for hemophilia using adenoviral vectors.

Hemophilia A and B are hereditary coagulation defects resulting from a deficiency of factor VIII (FVIII) and factor IX (FIX), respectively. Introducing a functional FVIII or FIX gene could potentially provide a cure for these bleeding disorders. Adenoviral vectors have been used as tools to introduce potentially therapeutic genes into mammalian cells and are by far the most efficient vectors for hepatic gene delivery. Long-term expression of both FVIII and FIX has been achieved in preclinical (hemophilic) mouse models using adenoviral vectors. Therapeutic levels of FVIII and FIX also have been achieved in hemophilic dogs using adenoviral vectors and in some cases expression was long-term. The performance of earlier generation adenoviral vectors, which retained residual viral genes, was compromised by potent acute and chronic inflammatory responses that contributed to significant toxicity and morbidity and short-term expression of FVIII and FIX. The development of improved adenoviral vectors devoid of viral genes (gutless or high-capacity adenoviral vectors) was therefore warranted, which led to a significant reduction in acute and chronic toxicity and more prolonged expression of FVIII and FIX. Strategies aimed at making these vectors safer and less immunogenic and their implications for hemophilia gene therapy are discussed in this review.

Onco-retroviral and lentiviral vector-based gene therapy for hemophilia: preclinical studies.

Hemophilia A and B gene therapy requires long-term and stable expression of coagulation factor VIII (FVIII) or factor IX (FIX), respectively, and would need to compare favorably with protein replacement therapy. Onco-retroviral and lentiviral vectors are attractive vectors for gene therapy of hemophilia. These vectors have the potential for long-term expression because they integrate stably in the target cell genome. Whereas onco-retroviral vectors can only transduce dividing cells, lentiviral vectors can transduce a broad variety of cell types irrespective of cell division. Several preclinical and clinical studies have explored the use of onco-retroviral and, more recently, lentiviral vectors for gene therapy of hemophilia A or B. Both ex vivo and in vivo gene therapy approaches have been evaluated, resulting in therapeutic FVIII or FIX levels in preclinical animal models. Whereas in vivo gene therapy using onco-retroviral or lentiviral vectors often led to long-term FVIII or FIX expression from transduced hepatocytes, ex vivo approaches were generally hampered by either low or transient expression of FVIII or FIX levels in vivo and/or inefficient engraftment. Furthermore, immune responses against the transgene product remain a major issue that must be resolved before the full potential of these vectors eventually can be exploited clinically. Nevertheless, the continued progress in vector design combined with a better understanding of vector biology may ultimately yield more effective gene therapy approaches using these integrating vectors.

Evaluation of recombinant human factor IX: pharmacokinetic studies in the rat and the dog.

The pharmacokinetics of intravenously administered recombinant human factor IX (rhFIX) were studied in Sprague-Dawley rats and Beagle dogs. Rats received rhFIX (50 IU/kg once daily) for 28 days, and the plasma half-life was 5 h. Anti-Human Factor IX serum antibody levels were found in only 1 of 12 rats. The pharmacokinetic profiles of rhFIX or Mononine, a purified human plasma-derived factor IX, after single 100 IU/kg i.v. doses in dogs, were similar. Peak plasma concentrations of rhFIX and Mononine were 4-5 micrograms/ml. The mean plasma half-lives were 13.2 +/- 1.6 h for rhFIX and 13.3 +/- 1.6 h for Mononine. Dogs also received rhFIX (40 IU/kg i.v., daily) for 28 days or Mononine (40 IU/kg i.v. daily) for 14 days. Anti-human Factor IX serum antibody levels were determined for each compound. Pharmacokinetic half-lives decreased in these treated dogs which developed antihuman Factor IX antibodies. The antibody responses in 28 day rhFIX (40 IU/kg) dogs were similar to 14 day Mononine (40 IU/kg) dogs.

Subcutaneous injection of factor IX for the treatment of haemophilia B.

Haemophilia B patients are normally treated, either prophylactically or in response to bleeding episodes, by frequent intravenous injections of factor IX purified from blood donors. Here we show in model animal experiments that purified human factor IX, when injected subcutaneously, is rapidly (in 3-11 h) and reasonably efficiently (30-40% of an equivalent intravenous dose) transported at least partly by the lymphatic drainage of the skin into the bloodstream, mostly in a biologically active form. This suggests that patients could be treated prophylactically by subcutaneous rather than intravenous injection, where the short delay in raising plasma factor IX to haemostatic levels would be clinically acceptable. More generally, our studies emphasize that the subcutaneous route of injection should be useful for other therapeutic proteins, including other clotting factors, which have to be delivered to the bloodstream, as long as their half-life is at least a few hours allowing time for transport into the general circulation.