Novel therapeutic approaches for haemophilia

Carbon Nanofiber-Ionic Liquid Nanocomposite Modified Aptasensors Developed for Electrochemical Investigation of Interaction of Aptamer/Aptamer-Antisense Pair with Activated Protein C

Selective and sensitive detection of human activated protein C (APC) was performed herein by using carbon nanofiber (CNF) and ionic liquid (IL) composite modified pencil graphite electrode (PGE) and electrochemical impedance spectroscopy (EIS) technique. A carbon nanomaterial-based electrochemical aptasensor was designed and implemented for the first time in this study for the solution-phase interaction of DNA-Apt with its cognate protein APC as well as APC inhibitor aptamer-antidote pair. The applicability of this assay developed for the determination of APC in fetal bovine serum (FBS) and its selectivity against different proteins (protein C, thrombin, bovine serum albumin) was also examined. CNF-IL modified aptasensor specific to APC provided the detection limit as 0.23 μg/mL (equal to 3.83 nM) in buffer medium and 0.11 μg/mL (equal to 1.83 nM) in FBS. The duration of the proposed assay from the point of electrode modification to the detection of APC was completed within only 55 min.

Non-factor replacement therapy for haemophilia: a current update

One of the most challenging issues facing us in the treatment of haemophilia is the development of alloantibodies against infused factor VIII (FVIII) or factor IX (FIX). Inhibitors render factor replacement therapy ineffective, exposing patients to an unacceptably high risk of morbidity and mortality. Besides the well-known bypassing agents (i.e. activated prothrombin complex concentrate and recombinant activated factor VII) used to treat or prevent bleeding in haemophilia patients with inhibitors, there is growing interest in a new class of therapeutic agents which act by enhancing coagulation (i.e. emicizumab) or inhibiting anticoagulant pathways (i.e. fitusiran and concizumab). This review will focus on these innovative therapies, providing an update on their current stage of clinical development.

Novel therapies and current clinical progress in hemophilia A

The evolution of hemophilia treatment and care is a fascinating one but has been fraught with many challenges at every turn. Over the last 50 years or so patients with hemophilia and providers have witnessed great advances in the treatment of this disease. With these advances, there has been a dramatic decrease in the mortality and morbidity associated with hemophilia. Even with the remarkable advancements in treatment, however, new and old challenges continue to plague the hemophilia community. The cost of factor replacement and the frequency of infusions, especially in patients with severe hemophilia on prophylaxis, remains a significant challenge for this population. Other challenges include obtaining reliable venous access, especially in younger patients, and the development of neutralizing alloantibodies (inhibitors). The development of extended half-life products, a bispecific antibody which mimics the coagulation function of factor VIII (FVIII) and inhibition of anticoagulation proteins such as antithrombin with antibodies, aptamers or RNA interference technology have offered novel therapeutic approaches to overcome some of these existing challenges. Additionally, ongoing gene therapy research offers a way to possibly cure hemophilia. These novel treatment tools in conjunction with the establishment of an increasing number of comprehensive hemophilia centers and worldwide advocacy efforts have continued to push the progress of hemophilia care to new frontiers. This review highlights and summarizes these novel therapeutic approaches and the current clinical progress of hemophilia A.

Immune tolerance induced by platelet-targeted factor VIII gene therapy in hemophilia A mice is CD4 T cell mediated

Essentials The immune response is a significant concern in gene therapy. Platelet-targeted gene therapy can restore hemostasis and induce immune tolerance. CD4 T cell compartment is tolerized after platelet gene therapy. Preconditioning regimen affects immune tolerance induction in platelet gene therapy.

SUMMARY

Background Immune responses are a major concern in gene therapy. Our previous studies demonstrated that platelet-targeted factor VIII (FVIII) (2bF8) gene therapy together with in vivo drug selection of transduced cells can rescue the bleeding diathesis and induce immune tolerance in FVIIInull mice. Objective To investigate whether non-selectable 2bF8 lentiviral vector (LV) for the induction of platelet-FVIII expression is sufficient to induce immune tolerance and how immune tolerance is induced after 2bF8LV gene therapy. Methods Platelet-FVIII expression was introduced by 2bF8LV transduction and transplantation. FVIII assays and tail bleeding tests were used to confirm the success of platelet gene therapy. Animals were challenged with rhF8 to explore if immune tolerance was induced after gene therapy. Treg cell analysis, T-cell proliferation assay and memory B-cell-mediated ELISPOT assay were used to investigate the potential mechanisms of immune tolerance. Results We showed that platelet-FVIII expression was sustained and the bleeding diathesis was restored in FVIIInull mice after 2bF8LV gene therapy. None of the transduced recipients developed anti-FVIII inhibitory antibodies in the groups preconditioned with 660 cGy irradiation or busulfan plus ATG treatment even after rhF8 challenge. Treg cells significantly increased in 2bF8LV-transduced recipients and the immune tolerance developed was transferable. CD4+ T cells from treated animals failed to proliferate in response to rhF8 re-stimulation, but memory B cells could differentiate into antibody secreting cells in 2bF8LV-transduced recipients. Conclusion 2bF8LV gene transfer without in vivo selection of manipulated cells can introduce immune tolerance in hemophilia A mice and this immune tolerance is CD4+ T cell mediated.

In Vitro Evaluation of Aptamer-Based Reversible Inhibition of Anticoagulant Activated Protein C as a Novel Supportive Hemostatic Approach

Activated protein C (APC) is a critical regulator of thrombin formation and thereby protects against thrombosis. On the other hand, overwhelming formation of APC increases the risk of bleeding such as in trauma-induced coagulopathy. Thus, pharmacological inhibition of APC activity may improve blood clottability in certain clinical situations. In this study, we demonstrate that the DNA aptamer HS02-52G binds with fast onset (1.118 ± 0.013 × 10⁵ M^-1 s^-1) to APC and possesses a long residence time of 13.5 min within the aptamer-APC complex. Functional analysis revealed HS02-52G as a highly potent and specific inhibitor of APC in plasma and whole blood with IC₅₀ values ≤30 nM, whose activity can be readily neutralized by the short complementary DNA molecule AD22. These features qualify the novel aptamer-antidote pair as a candidate treatment option for acute APC-related bleedings.

Tailoring hemostatic therapies to lower inhibitor development in previously untreated patients with severe hemophilia A

After technological progress provided safer therapeutic products for patients with hemophilia A, the development of alloantibodies (inhibitors) neutralizing the coagulant activity of infused factor VIII (FVIII) remains the most serious complication of replacement therapy, predisposing patients to greater morbidity and causing higher treatment costs. The pathogenesis of inhibitors, which develop at a high rate in previously untreated children with severe hemophilia A, is multifactorial, resulting from complex interactions between genetic and environmental factors. Among non-genetic determinants, a key role is played by treatment-related factors, including the source of FVIII product (i.e., plasma derived or recombinant) and the mode of replacement therapy delivery (i.e., intensity, prophylaxis vs. on demand). We review the potential interventions on these modifiable factors that may help to lower the rate of inhibitor development. In addition, interest is currently directed toward the potential for lesser immunogenicity of novel hemostatic agents designed to decrease the dosing frequency or avoid/delay the need of FVIII replacement therapy.

Safety surveillance in haemophilia and allied disorders

The introduction of clotting factor concentrates has transformed the lives of persons with inherited bleeding disorders. With the use of prophylactic treatment, it is now possible to prevent bleeding in these individuals. The early concentrates were contaminated with the HIV and hepatitis C viruses (HCV) and resulted in major morbidity and mortality in the recipients. Current products are much safer, especially in terms of infectious agents, but other adverse events such as alloantibodies (inhibitors), allergic reactions and thrombotic risks remain of concern. Approximately 30% of previously untreated patients with severe haemophilia A develop inhibitors, making this the most important issue in haemophilia care today. Recently, it was suggested that one of the most commonly used concentrates was associated with a higher inhibitor risk, but this was not supported by the evidence from all studies. Good safety surveillance systems are essential for all diseases and products but are particularly so in the group of individuals with inherited bleeding disorders treated with clotting factor concentrates who have suffered disproportionately from the adverse effects of their treatment. National and multinational systems are now in place to allow reporting of adverse events in patients with inherited bleeding disorders. All clinicians treating individuals with inherited bleeding disorders should prospectively report adverse events to treatment even if they are believed to be common and well recognized.

Hemophilic arthropathy of the elbow: prophylaxis, imaging, and the role of invasive management

Hemophilia is an X-linked recessive deficiency of clotting factor VIII (hemophilia A) or IX (hemophilia B) that can result in hemarthrosis of various joints, including the elbow. Left unchecked, this can lead to progressive joint destruction and significant morbidity. Appropriate management of the elbow joint through prophylactic measures, accurate imaging, and timely intervention is essential. Replacing or supplementing deficient factor with a plasma-derived or recombinant factor concentrate can minimize bleeding episodes. Joints should be routinely monitored for damage. Plain films offer an inexpensive window into bone disease and joint space changes but lack soft tissue detail and may not detect early changes. Magnetic resonance imaging provides a high level of detail but may be limited by its cost and need for sedation in younger patients. Ultrasound may not achieve the same level of resolution as magnetic resonance imaging, but it is increasingly used as a convenient, effective, and relatively inexpensive alternative. Patients who experience hemarthrosis of the elbow with joint damage often require more invasive treatment. Radiosynovectomy and arthroscopic synovectomy are effective at minimizing pain and preventing future bleeding episodes, whereas extensive joint damage may necessitate total elbow replacement.

Predicting the Uncertain Future of Aptamer-Based Diagnostics and Therapeutics

Despite the great promise of nucleic acid aptamers in the areas of diagnostics and therapeutics for their facile in vitro development, lack of immunogenicity and other desirable properties, few truly successful aptamer-based products exist in the clinical or other markets. Core reasons for these commercial deficiencies probably stem from industrial commitment to antibodies including a huge financial investment in humanized monoclonal antibodies and a general ignorance about aptamers and their performance among the research and development community. Given the early failures of some strong commercial efforts to gain government approval and bring aptamer-based products to market, it may seem that aptamers are doomed to take a backseat to antibodies forever. However, the key advantages of aptamers over antibodies coupled with niche market needs that only aptamers can fill and more recent published data still point to a bright commercial future for aptamers in areas such as infectious disease and cancer diagnostics and therapeutics. As more researchers and entrepreneurs become familiar with aptamers, it seems inevitable that aptamers will at least be considered for expanded roles in diagnostics and therapeutics. This review also examines new aptamer modifications and attempts to predict new aptamer applications that could revolutionize biomedical technology in the future and lead to marketed products.

Emerging genetic and pharmacologic therapies for controlling hemostasis: beyond recombinant clotting factors

For more than 3 decades, the scientific community has pursued gene correction of hemophilia, with the goal that an individual with congenitally deficient factor VIII or factor IX might synthesize adequate endogenous clotting factor to be relieved of burdensome repeated clotting factor infusions, as well as the emotional weight of continuous hemorrhage risk. Recent reports of successful factor IX gene therapy and partial correction of the bleeding phenotype have raised the bar for success for a robust crop of new clinical gene therapy efforts for both hemophilia A and B. At the same time that gene therapy is gaining momentum, suggesting the possibility of relief from regular intravenous coagulation protein replacement, a number of innovative technologies that enhance hemostatic potential independently of replacement factor administration are demonstrating success in human clinical application. Human clinical trial progress is reviewed regarding a recombinant bispecific IgG antibody to factors IXa and X that mimics factor VIII cofactor activity, as well as monoclonal antibody and short interfering RNA strategies that demonstrate hemostatic efficacy via opposing inhibitors of coagulation. These strategies, associated with prolonged hemostatic potential following subcutaneous (ACE910, ALN-AT3, Concizumab) or single administration (eg, gene therapy) make it possible to imagine a day when recombinant clotting factor administration, rather than being a daily preoccupation, is relegated to an adjunctive role in supporting more novel standard of care therapies.