Alternative therapies for the management of inhibitors

Current status and future prospects of activated recombinant coagulation factor VIIa, NovoSeven®, in the treatment of haemophilia and rare bleeding disorders

rFVIIa, a human recombinant activated coagulation factor VII, has been used worldwide for more than two decades for the treatment of bleeding episodes and prevention of bleeding in patients undergoing surgery/invasive procedures with congenital haemophilia A or B with inhibitors (CHwI A or B), acquired haemophilia (AH), congenital factor VII deficiency and Glanzmann thrombasthenia (GT), refractory to platelet transfusion. The approved dosage, administration and indication of rFVIIa in the US, Europe and Japan differ, depending on the needs of the patient population and regulatory practices. This review presents an overview of the current status and future prospects, including that from a Japanese perspective, of using rFVIIa in the treatment of approved indications. The efficacy and safety of rFVIIa in the approved indications has been demonstrated in several randomised and observational studies and data from registries. The overall incidence of thrombosis across all approved indications in a retrospective safety assessment of clinical trials and registries, prelicensure studies and postmarketing surveillance studies of rFVIIa use was 0.17%. Specifically, the risk of thrombotic events was 0.11% for CHwI, 1.77% for AH, 0.82% for congenital factor VII deficiency and 0.19% for GT. Emerging non-factor therapies such as emicizumab have changed the treatment landscape of haemophilia A, including preventing bleeding in patients with CHwI. However, rFVIIa will continue to play a significant role in the treatment of such patients, particularly during breakthrough bleeding or surgical procedures.

Factor VIII and Factor IX Activity Measurements for Hemophilia Diagnosis and Related Treatments

Accurate measurement of clotting factors VIII (FVIII) or IX (FIX) is vital for comprehensive diagnosis and management of patients with hemophilia A or B. The one-stage activated partial thromboplastin time (aPTT)-based clotting assay is the most commonly used method worldwide for testing FVIII or FIX activities. Alternatively, FVIII and FIX chromogenic substrate assays, which assess the activation of factor X, are available in some specialized laboratories. The choice of reagent or methodology can strongly influence the resulting activity. Variation between one-stage FVIII or FIX activities has been reported in the measurement of some standard and extended half-life factor replacement therapies and gene therapy for hemophilia B using different aPTT reagents. Discrepancy between one-stage and chromogenic reagents has been demonstrated in some patients with mild hemophilia A or B, the measurement of some standard and extended half-life factor replacement therapies, and the transgene expression of hemophilia A and B patients who have received gene therapy. Finally, the measurement of bispecific antibody therapy in patients with hemophilia A has highlighted differences between chromogenic assays. It is imperative that hemostasis laboratories evaluate how suitable their routine assays are for the accurate measurement of the various hemophilia treatment therapies.

Integrated Hemophilia Patient Care via a National Network of Care Centers in the United States: A Model for Rare Coagulation Disorders

Rare, chronic diseases such as hemophilia and other congenital coagulation disorders require coordinated delivery of services for optimal outcomes. Hemophilia Treatment Centers (HTCs) are specialized, multidisciplinary health-care centers providing team-based care to meet the physical, psychosocial, and emotional needs of people with hemophilia (PWH) and may serve as a model for other rare coagulation disorders. Health-care purchasers, as well as the general medical community, may not appreciate the breadth and quality of services provided by HTCs. They exemplify the acculturalization and actualization of integrated care by providing comprehensive diagnostic and treatment services that reduce morbidity, mortality, avoidable emergency room visits, hospitalizations, and overall costs, while promoting a longer lifespan and improved patient functioning and outcomes. This is accomplished by a team-based approach relying upon a shared decision-making model to effectively prevent complications and manage symptoms in PWH, who are dependent on high-cost treatments. This article provides a concise yet comprehensive description of the core components of an HTC and the regional and national networks in the United States, which together achieve their incomparable value for all stakeholders.

The availability of new drugs for hemophilia treatment

INTRODUCTION

A number of new FVIII/IX concentrates enriched the portfolio of products available for the treatment of hemophilia A/B patients. Due to the large inter-patient variability, accurate tailoring of the therapy became essential to improve patients' adherence, clinical outcomes, and cost/effectiveness ratio. Recently, non-replacement therapies have taken the limelight and succeeded in decreasing the bleedings of patients.

AREAS COVERED

The PK characteristics, efficacy, and safety of the new rFVIII and rFIX concentrates and of non-replacement therapy, are reported in detail in the published clinical trials.

EXPERT OPINION

Outstanding improvements of rFIX concentrates' pharmacokinetics and pharmacodynamics have allowed to reduce the bleedings in hemophilia B patients, in order to increase their adherence to prophylaxis and quality of life. Less significant are the effects of pegylation or Fc fusion on the pharmacokinetics of the new rFVIII concentrates. The new non-replacement therapy is achieving the favor of many treaters and patients, in particular those with Factor VIII inhibitors. Great attention must be paid to the dangerous synergy of APCC and emicizumab, responsible for some fatal events during the clinical trials and compassionate use of this drug. So far, replacement therapy should be the standard of care for hemophilia patients without inhibitors or difficulties in venous access.

Intrinsic differences between FVIIIa mimetic bispecific antibodies and FVIII prevent assignment of FVIII-equivalence

Essentials Non-factor VIII (FVIII) therapies for hemophilia A, such as bispecific antibodies (bsAbs), are in development. Bispecific antibodies are intrinsically different from FVIII and lack many of the same regulatory mechanisms. These differences complicate assignment and interpretation of FVIII-equivalent activity. Inability to assign FVIII equivalence compromises our capacity to assess hemostatic potential of bsAb therapies.

BACKGROUND

Activated factor VIII (FVIIIa) mimetic bsAbs aim to enable prophylactic treatment of hemophilia A patients with and without inhibitors. With different mechanisms of action, benchmarking their activity against FVIII to determine efficacious yet safe dosage is difficult.

OBJECTIVE

To compare the activities of sequence identical emicizumab (SI-Emi) and another bsAb, BS-027125, to recombinant FVIII (rFVIII) using clinical and nonclinical assays and to evaluate our ability to assign a FVIII-equivalent value to bsAbs and implications thereof.

METHODS

Activities of SI-Emi, BS-027125, and rFVIII were measured by one-stage clotting assay, chromogenic factor Xa generation assay, and thrombin generation assay. We also assessed the activity of anti-FIXa and anti-FX bivalent homodimers of each bsAb and probed the effect of different reagents in thrombin generation assay (TGA).

RESULTS

The FVIII-like activity of SI-Emi and BS-027125 ranged greatly across each assay, varying both by parameter measured within an assay and by reagents used. Notably, SI-Emi anti-FIXa bivalent homodimer had meaningful activity in several assays, whereas BS-027125 anti-FIXa bivalent homodimer only had activity in the chromogenic assay. Surprisingly, SI-Emi displayed activity in the absence of phospholipids, while BS-027125 had minimal phospholipid-independent activity.

CONCLUSIONS

Bispecific antibodies demonstrate little consistency between assays tested here owing to intrinsic differences between FVIII and bsAbs. While some trends are shared, the bsAbs also differ in mechanism. These inconsistencies complicate assignment of FVIII-equivalent values to bsAbs. Ultimately, a deeper mechanistic understanding of bsAbs as well as bsAb-tailored assays are needed to monitor and predict their hemostatic potential and long-term efficacy and safety confidently.

Emicizumab: Review of the literature and critical appraisal

INTRODUCTION

Emicizumab-kywh (ACE910) is a recombinant, humanized, asymmetric bispecific antibody that functions to bring activated FIX (FIXa) and zymogen FX into an appropriate steric conformation to medicate the activation of FX to FXa thereby mimicking the cofactor function of FVIIIa.

AIM

The objective of this manuscript was to review the development and potential role for emicizumab in the treatment of patients with haemophilia A with and without inhibitors.

METHODS

A Cochrane Library and PubMed (MEDLINE) search focusing on emicizumab in haemophilia was conducted.

RESULTS

In total, 37 citations were retrieved and serve as the database for the literature reviewed herein. Once-weekly subcutaneous injection of emicizumab at three dose levels has been shown to be effective as prophylaxis to prevent bleeding in a majority haemophilia A patients with inhibitors to FVIII. Likewise, prevention of bleeding was also observed in more than two thirds of patients without inhibitors to FVIII. One antidrug antibody to emicizumab has been reported in over 600 treated patients, two have developed thromboembolic events and three thrombotic microangiopathy. These thrombotic complications have occurred in conjunction with FVIII-bypassing agents, and none have been observed following recommendations from the manufacturer regarding concomitant use of bypassing agents. The median annual treated bleeding rates were decreased in patients with as well as those without an inhibitor to FVIII.

CONCLUSION

The principal advantage of emicizumab is subcutaneous administration and effectiveness irrespective of the presence of inhibitors. Emicizumab could conceivably represent a new epoch in the treatment of people with haemophilia A.

Patient-Specific iPSC-Derived Endothelial Cells Provide Long-Term Phenotypic Correction of Hemophilia A

We generated patient-specific disease-free induced pluripotent stem cells (iPSCs) from peripheral blood CD34+ cells and differentiated them into functional endothelial cells (ECs) secreting factor VIII (FVIII) for gene and cell therapy approaches to cure hemophilia A (HA), an X-linked bleeding disorder caused by F8 mutations. iPSCs were transduced with a lentiviral vector carrying FVIII transgene driven by an endothelial-specific promoter (VEC) and differentiated into bona fide ECs using an optimized protocol. FVIII-expressing ECs were intraportally transplanted in monocrotaline-conditioned non-obese diabetic (NOD) severe combined immune-deficient (scid)-IL2rγ null HA mice generating a chimeric liver with functional human ECs. Transplanted cells engrafted and proliferated in the liver along sinusoids, in the long term showed stable therapeutic FVIII activity (6%). These results demonstrate that the hemophilic phenotype can be rescued by transplantation of ECs derived from HA FVIII-corrected iPSCs, confirming the feasibility of cell-reprogramming strategy in patient-derived cells as an approach for HA gene and cell therapy.

The inhibitors - a challenge for the management of patients with hereditary haemophilia A

INTRODUCTION

Our research strategy was aimed at evaluating the possible implication of the type of factor VIII product administered as substitution treatment to haemophilia A patients in the occurrence of inhibitors and their consequences on the management.

METHODS

Scientific articles from July 2015 to July 2017 were searched using the PubMed and PubMed Central databases. The used search terms included "haemophilia A", "inhibitors", "plasma-derived factor VIII" and "recombinant factor VIII".

RESULTS

The risk factors for inhibitors occurrence may be patients-related (genetic and nongenetic) and treatment-related. The possibility of a correlation between the increased purity of factor VIII given as substitution treatment and the occurrence of inhibitors is discussed in the light of literature data. Plasma-derived factor VIII is less immunogenic, but not entirely safe from the point of view of the possibility of transmitting biological agents. It is obvious that there is not enough plasma-derived factor VIII for the planet's needs. Recombinant factor VIII products have revolutionized the treatment of patients with haemophilia A over the past 3 decades by the disappearance of transfusion-related infections and their complications. They are safer in terms of pathogens and the new long-acting factor VIII products are based on recombinant DNA technology.

CONCLUSION

Plasma-derived or recombinant factor VIII products must co-exist on the market for the benefit of haemophilic patients. Future solutions could be: less immunogenic factor VIII products, nonfactor replacement strategies, or bispecific antibody that mimics the function of coagulation factor VIII.

Circumcision in hemophilia using low quantity of factor concentrates: experience from Dakar, Senegal

Background

Circumcision in hemophiliacs is a delicate surgery because of bleeding risks that could be avoided by adequate substitution of coagulation factor. This practice is very challenging in countries where anti hemophilic treatment is inaccessible. The study aimed to evaluate a circumcision protocol in hemophilia A using low quantities of factor concentrates.

Methods

This prospective study included 26 hemophiliacs A who underwent circumcision in 2014. Medical treatment protocol using low quantity of factor concentrates was drafted by physicians of the Hemophilia Treatment Center and the surgical protocol by experienced surgeons. Assessment criteria were: number of hospitalization days, number of exposure days to factor concentrates, delay to healing and occurrence of bleeding events.

Results

Mean age was 9.6 years (1–30). Hemophiliacs patients were classified as severe (n = 8), moderate (n = 9) and mild form (n = 9). Mean number of exposure days to factor VIII concentrates was 6.9 days (5–12) in children and 10.75 days (7–16) in adults (p = 0.0049); mean number of hospitalization days was 3.68 days (2–10) in children and 13.5 days (13–15) in adults (p = 0.0000); delay to healing was 26.47 days (20–35) in children and 25.25 days (22–30) in adults (p = 0.697); five haemophiliacs (19.2%) presented bleeding events after the circumcision. The mean amount of FIII concentrates used per patient was 1743 IU (810–2340).

Conclusion

The study shows treatment protocol using low quantity of factor concentrates is efficient in hemophilia patients who underwent circumcision.

Acquired factor VIII deficiency: two case reports and a review of literature

Background

Acquired factor VIII (FVIII) deficiency, or acquired hemophilia A (AHA), is a rare autoimmune disorder involving antibody-mediated depletion of coagulation FVIII, leading to severe, life-threatening bleeding. The condition is often associated with other autoimmune disorders, and its treatment involves replacement of FVIII and various modes of immunosuppression. Recently, a few noteworthy therapeutic advances have been made. We present two cases of severe AHA in Chinese women. One of these women developed this disorder in the setting of possible parvovirus B19 infection, which has not yet been reported in association with AHA. Other notable features of her case included paradoxical venous thrombosis and possible association with Sjogren’s syndrome and myositis. The other woman failed to respond to usual first-line therapies despite exhibiting a less severe clinical course, illustrating the varied but potentially stubborn behavior of this disorder.

Case 1

An 87-year-old woman presented with diffuse ecchymoses, melena, vaginal bleeding. Labs showed hemoglobin (Hgb) nadir of 5.7 mg/dL, elevated partial thromboplastin time (PTT), FVIII level <1%, mixing study consistent with an inhibitor, elevated anti-Sjogren’s-Syndrome-related antigen A antibody, elevated creatinine kinase, and elevated parvovirus IgM and IgG. Imaging of her arm showed diffuse myositis and deep venous thrombosis. After intravenous and oral steroids, her FVIII levels normalized, and her symptoms subsided.

Case 2

A 59-year-old woman presented with recurrent ecchymoses and hematomas in her extremities. Labs showed Hgb of 11.7 mg/dL, elevated PTT, FVIII level of 3%, and mixing study consistent with an inhibitor. Despite receiving a long course of steroids, several courses of IVIG, and a few courses of Rituximab, her FVIII level remained critically low.

Conclusion

The rarity of AHA limits our understanding of this disease and the ability to perform trials to discover optimal therapies. We hope that these case reports and discussion will shed further light on the varied clinical manifestations and natural histories of this disorder to guide better recognition and treatment of AHA.

Rare bleeding disorders-old diseases in the era of novel options for therapy

Rare diseases are defined as life-threatening or chronically debilitating diseases with a prevalence of less than one per 2000 according to the European Union or one per 1250 according to the USA. Congenital rare bleeding disorders RBD are reported in most populations, with incidence varying from 1 in 5000 (Hemophilia A), 1:30,000 (Hemophilia B) to much rarer (1:500,000 for FVII deficiency, 1-3 million for Prothrombin or FXIII deficiency). Acquired Hemophilia A is also a rare bleeding disorder with estimated frequency of 1 in million. Most RBDs are inherited as autosomal recessive (AR); however, heterozygous carriers with varying degrees of corresponding factor deficiency may render an unpredictable propensity for bleeding. In patients with bleeding symptoms, laboratory assessment and especially molecular techniques currently enable accurate diagnosis and may provide tools for prenatal and family counseling. Currently hemostasis control is mainly based upon replacement of the missing coagulation factors (unless presence of inhibitors renders it impossible), however future gene therapy and disruptive, non-replacement alternatives may be promising for patients with RBD.

The current state of adverse event reporting in hemophilia

INTRODUCTION

Replacement of the missing clotting factor is the mainstay of hemophilia treatment. Whilst historically many hemophilia patients were infected with blood-borne viruses transmitted via plasma-derived products, nowadays the formation of alloantibodies against the missing clotting factor is the main adverse event of treatment. Areas covered: This paper provides an overview of the current national and international adverse event reporting systems, what these surveillance schemes taught us about side effects of the products presently in use, and elaborates on how to adapt these systems to the challenges we face with the changing treatment landscape. Expert commentary: Treatment of inherited bleeding disorders was accompanied by severe complications in the past, resulting in major morbidity and mortality. Current products are much safer, but still require monitoring via efficient safety surveillance systems. Adverse events are reported in national and international systems. With many new products entering the market, as well as non-factor replacement therapies, new safety issues may arise. It is important to identify potential adverse events early by making surveillance systems suitable to pick up unknown or unexpected effects, and to recognize and communicate patterns of adverse events rapidly.