Advances in the treatment of bleeding disorders

Present status of scheduled vaccinations and vaccination-related bleeding in Chinese children with haemophilia

AIM

Many countries have detailed recommendations for haemophilia patients to reduce the risk of vaccination-related bleeding. However, data from developing countries are lacking. We investigated scheduled vaccinations and vaccination-related bleeding complications in Chinese children with haemophilia and analysed issues related to vaccinations.

METHODS

Children with haemophilia in the PUMCH Haemophilia Treatment Centre were contacted via telephone. We distributed a vaccination questionnaire to their parents. The severity of haemophilia, coagulation factor infusions before vaccination, injection mode, and vaccination-related complications were analysed.

RESULTS

A total of 440 valid questionnaires were received from 27 of 34 provinces in China. 31.3% (138/440) of the children with haemophilia did not receive all of their vaccinations. Among the children who received vaccinations, 48.1% (197/409) experienced bleeding complications. In patients with severe haemophilia, those on regular prophylaxis had a lower incidence of local hematoma compared to those on intermittent or no prophylaxis (14.3% vs. 26.5% vs. 39.7%, P < 0.05). The incidence of local hematomas was lower by subcutaneous (SQ) injections than by intramuscular injections (24.6% vs. 35.3%, P < 0.05).

CONCLUSION

The vaccination rate is quite insufficient in Chinese children with haemophilia. Missed vaccinations are related to vaccination-related bleeding complications. Prophylaxis before vaccination and SQ injections would help reduce bleeding complications.

Rare bleeding disorders: Advances in management

Inherited factor coagulation deficiencies and vascular bleeding disorders, associated with bleeding of various severity, are often classified as rare bleeding disorders (RBDs). These include inherited fibrinogen disorders, inherited platelet function disorders (IPFD) and hereditary haemorrhagic telangiectasia (HHT). In the last decades, there have been large increases in knowledge on the epidemiology, genetics, physiopathology, clinical features, and diagnosis of RBDs, but improvements in management have been more limited and remain challenging. The treatment mainstay of RBDs is based only on replacement of a few available coagulation factor concentrates or cryoprecipitates. There is growing interest in therapeutic agents that enhance coagulation or inhibiting anticoagulant pathways in RBDs. In severe IPFD, the optimal platelet transfusion strategy is not yet established. Moreover, data is scarce on the effectiveness and safety of desmopressin and/or antifibrinolytic drugs often used for milder IPFD treatment. The best fibrinogen replacement strategy (prophylaxis vs. on demand) in afibrinogenemia is still debated. Similarly, the optimal trough fibrinogen target level for treatment of acute bleeding, and the role of fibrinogen replacement during pregnancy in mild hypofibrinogenemia and dysfibrinogenemia, have not been properly evaluated. The therapeutic arsenal in HHT includes antifibrinolytics and a series of antiangiogenic agents whose potential efficacy has been tested in small studies or are under investigation for treatment of bleeding. However, there is need to address several issues, including the optimal dosing strategies, the potential emergent toxicity of longer-term use, and the impact of systemic antiangiogenic treatment on visceral arteriovenous malformations.

RNA therapeutics for the treatment of blood disorders

Blood disorders are defined as diseases related to the structure, function, and formation of blood cells. These diseases lead to increased years of life loss, reduced quality of life, and increased financial burden for social security systems around the world. Common blood disorder treatments such as using chemical drugs, organ transplants, or stem cell therapy have not yet approached the best goals, and treatment costs are also very high. RNA with a research history dating back several decades has emerged as a potential method to treat hematological diseases. A number of clinical trials have been conducted to pave the way for the use of RNA molecules to cure blood disorders. This novel approach takes advantage of regulatory mechanisms and the versatility of RNA-based oligonucleotides to target genes and cellular pathways involved in the pathogenesis of specific diseases. Despite positive results, currently, there is no RNA drug to treat blood-related diseases approved or marketed. Before the clinical adoption of RNA-based therapies, challenges such as safe delivery of RNA molecules to the target site and off-target effects of injected RNA in the body need to be addressed. In brief, RNA-based therapies open novel avenues for the treatment of hematological diseases, and clinical trials for approval and practical use of RNA-targeted are crucial.

Blood-Induced Arthropathy: A Major Disabling Complication of Haemophilia

Haemophilic arthropathy (HA) is one of the most serious complications of haemophilia. It starts with joint bleeding, leading to synovitis which, in turn, can cause damage to the cartilage and subchondral bone, eventually inducing degenerative joint disease. Despite significant improvements in haemophilia treatment over the past two decades and recent guidelines from ISTH and WFH recommending FVIII trough levels of at least 3 IU/dL during prophylaxis, patients with haemophilia still develop joint disease. The pathophysiology of HA is complex, involving both inflammatory and degenerative components. Early diagnosis is key for proper management. Imaging can detect joint subclinical changes and influence prophylaxis. Magnetic resonance imagining (MRI) and ultrasound are the most frequently used methods in comprehensive haemophilia care centres. Biomarkers of joint health have been proposed to determine osteochondral joint deterioration, but none of these biomarkers has been validated or used in clinical practice. Early prophylaxis is key in all severe haemophilia patients to prevent arthropathy. Treatment is essentially based on prophylaxis intensification and chronic joint pain management. However, there remain significant gaps in the knowledge of the mechanisms responsible for HA and prognosis-influencing factors. Better understanding in this area could produce more effective interventions likely to ultimately prevent or attenuate the development of HA.

National strategic advocacy to manage patients with inherited bleeding disorders in low and lower-middle income countries

INTRODUCTION

Inherited bleeding disorders (IBDs) including hemophilia, von Willebrand disease, platelet disorders, mucocutaneous bleeding disorders and coagulation factor deficiencies are rarely found and under-recognized in low and lower-middle-income countries. Some patients succumbed to serious bleeding without diagnosis and treatment during childhood.

AREA COVERED

Diagnosis, management, and prevention should be integrated into the existing health care system. Although some countries have not implemented appropriate health care infrastructure, an initiative plan should be set up by cooperation of experienced experts and health care providers. Identification of patients with IBDs should be started in the antenatal setting to search for females at risk of carrier state. The investigations include bleeding assessment, mixing venous clotting time, coagulogram, coagulation factor assay and mutation detection. Genotypic analysis is helpful for confirming the definite diagnosis, carrier detection as well as prenatal diagnosis for females at risk of bearing an offspring with severe bleeding manifestations. Management involves replacement therapy ranging from blood component to virus-inactivated factor concentrate. Appropriate research is an essential backbone for improving patients' care.

EXPERT OPINION

Effective national strategic advocacy to manage patients with IBDs requires intensive collaboration among policy makers, health care providers, patients, and family members.

Survival analysis of coagulation disorders: A retrospective study with a 5-year follow-up

Objective

Rare bleeding disorders (RBDs) are the diseases in which patients experience a deficiency of coagulation factors. In the management of these disorders, surveillance is a significant challenge. This study aimed to assess the survival of patients with RBDs in a five-year follow-up.

Materials and methods

This descriptive cross-sectional study was conducted on 146 patients with RBDs who had referred to Be'sat Hospital of Hamadan, Iran from July 2017 to August 2022. A computerized record search was performed to identify the patients. The surveillance time for a five-year follow-up was assessed with the Kaplan-Meier curve. A log-rank test also served to compare the survival rates according to the type of factor.

Results

Out of 146 patients, 117 (80.2%) were males and 29 (19.8%) were females. They were in the range of 2-59 years of age with a mean of 23.11 ± 14.6. The most common disorder was FVIII deficiency (65.8%), and the rarest one was FXIII deficiency (4.8%). The rate of survival for any reason was 54.42 ± 1.3 months. The survival in combined FV and FVIII deficiencies was found to be longer than in the other deficiencies (55.9 ± 5.7), but there was no significant difference (P ≥ 0.05). In contrast, the survival in FXIII deficiency was observed to be lower than the other cases (44 ± 9.6); however, no significant difference was found in this regard (P ≥ 0.05).

Conclusion

The results of this study show that patients with RBDs have different rates of survival, which suggests that identifying high-risk patients may be helpful for the improvement of their survival time through timely therapeutic interventions.

Postoperative outcomes of total elbow replacement in haemophilic elbow arthropathy: A systematic review

INTRODUCTION

Total elbow replacement (TER) is a surgical treatment option for haemophilic elbow arthropathy.

AIM

To review the outcomes of TER in haemophilic elbow arthropathy. The primary outcome measures were perioperative blood loss, postoperative complications, revision rates and length of hospital stay (LOS). Secondary outcomes were elbow range of motion (ROM), functional outcome scores and the visual analogue pain scale (VAS).

MATERIALS AND METHODS

PubMed, Medline, Embase and the Cochrane register were searched conforming to the PRISMA guidelines. Only studies with a minimum postoperative follow-up of 1 year were included. Quality appraisal was performed utilizing the MINORS criteria.

RESULTS

One hundred and thirty-eight articles were identified. Following article screening, only seven studies met the inclusion criteria. A total of 51 TERs in 38 patients were performed, with the Coonrad-Morrey prosthesis utilized in 51% of cases. The pooled postoperative complication and revision rates were 49% and 29%, respectively. Surgery-related postoperative mortality was 3.9%. The mean preoperative Mayo elbow performance score (MEPS) was 43 ± 20 whereas the mean postoperative MEPS was 89 ± 6. Mean preoperative VAS was 7.2 ± 1.9 while the mean postoperative VAS was 2.0 ± 1.4. Mean preoperative and postoperative elbow flexion arcs were 54 ± 15 and 91 ± 10 degrees, respectively. Mean preoperative and postoperative forearm rotation arcs were 86 ± 40 and 135 ± 19 degrees, respectively.

CONCLUSION

TER for haemophilic elbow arthropathy provides good to excellent improvements in pain and elbow ROM postoperatively. However, the overall complication and revision rates are relatively high, when compared to TER performed for other indications.

Current factor IX replacement options for hemophilia B and the challenges ahead

INTRODUCTION

Therapy for hemophilia B is aimed at replacing the congenital deficiency of coagulation factor IX (FIX). For replacement therapy, several FIX concentrates derived from donated human plasma or engineered by recombinant DNA technology are currently commercially available. The use of these products is well established and permit patients a relatively normal life. To further improve treatment efficacy, recombinant FIX products with a prolonged half-life have been developed, allowing relaxed prophylactic dosing and reducing treatment burden.

AREAS COVERED

In this review, we explore the current FIX replacement options for hemophilia B patients by analyzing the outcomes of their main clinical trials. We cover advances in the FIX molecules with extended half-life (EHL). Published literature on products for replacement of hemophilia B was retrieved using PubMed with no temporal limits.

EXPERT OPINION

The recent introduction of recombinant EHL FIX products has represented a major advance in the therapeutic management of hemophilia B patients, permitting both a reduction of treatment burden and improving patients' compliance to prophylaxis and, ultimately, quality of life.

Building the foundation for a community-generated national research blueprint for inherited bleeding disorders: research priorities for ultra-rare inherited bleeding disorders

BACKGROUND

Ultra-rare inherited bleeding disorders (BDs) present important challenges for generating a strong evidence foundation for optimal diagnosis and management. Without disorder-appropriate treatment, affected individuals potentially face life-threatening bleeding, delayed diagnosis, suboptimal management of invasive procedures, psychosocial distress, pain, and decreased quality-of-life.

RESEARCH DESIGN AND METHODS

The National Hemophilia Foundation (NHF) and the American Thrombosis and Hemostasis Network identified the priorities of people with inherited BDs and their caregivers, through extensive inclusive community consultations, to inform a blueprint for future decades of research. Multidisciplinary expert Working Group (WG) 3 distilled highly feasible transformative ultra-rare inherited BD research opportunities from the community-identified priorities.

RESULTS

WG3 identified three focus areas with the potential to advance the needs of all people with ultra-rare inherited BDs and scored the feasibility, impact, and risk of priority initiatives, including 13 in systems biology and mechanistic science; 2 in clinical research, data collection, and research infrastructure; and 5 in the regulatory process for novel therapeutics and required data collection.

CONCLUSIONS

Centralization and expansion of expertise and resources, flexible innovative research and regulatory approaches, and inclusion of all people with ultra-rare inherited BDs and their health care professionals will be essential to capitalize on the opportunities outlined herein.

Preoperative coagulation screening tests in pediatric patients: Clinical relevance and hemorrhagic outcomes of abnormal results

PURPOSE

Coagulation screening tests in children are still frequently performed in many countries to evaluate bleeding risk. The aim of this study was to assess the management of unexpected prolongations of the activated partial thromboplastin time (APTT) and prothrombine time (PT) in children prior to elective surgery, and the perioperative hemorrhagic outcomes.

METHODS

Children with prolonged APTT and/or PT who attended a preoperative anesthesia consultation from January 2013 to December 2018 were included. Patients were grouped according to whether they were referred to a Hematologist or were scheduled to undergo surgery without further investigation. The primary endpoint was to compare perioperative bleeding complications.

RESULTS

1835 children were screened for eligibility. 102 presented abnormal results (5.6%). Of them, 45% were referred to a Hematologist. Significant bleeding disorders were associated with a positive bleeding history, odds ratio of 51 (95% CI 4.8-538.5, P=.0011). No difference in perioperative hemorrhagic outcomes were found between the groups. An additional cost of 181 euros per patient and a preoperative median delay of 43 days was observed in patients referred to Hematology.

CONCLUSIONS

Our results suggest that hematology referral has limited value in asymptomatic children with a prolonged APTT and/or PT. Hemorrhagic complications were similar among patients referred and not referred to Hematology. A positive personal or family bleeding history can help identify patients with a higher bleeding risk, thus it should guide the need for coagulation testing and hematology referral. Further efforts should be made to standardize preoperative bleeding assessments tools in children.

Pain, depression and anxiety in people with haemophilia from three Nordic countries: Cross-sectional survey data from the MIND study

Introduction

People with haemophilia (PwH) may experience symptoms of haemophilia‐related pain, depression or anxiety, which can negatively impact health‐related quality of life.

Aim

To obtain the perspective of PwH and treaters from Sweden, Finland and Denmark on the management of haemophilia‐related pain, depression and anxiety using cross‐sectional survey data from the MIND study (NCT03276130).

Methods

PwH or their caregivers completed a survey about experiences of pain, depression and anxiety related to haemophilia, and the standard EQ‑5D‐5L instrument. Five investigators at haemophilia treatment centres (HTC) were sent a complementary survey containing questions about the management of pain and depression/anxiety.

Results

There were 343 PwH (mild: 103; moderate: 53; severe: 180; seven lacking severity information) and 71 caregiver responses. Experience of pain in the last 6 months was reported by 50% of PwH respondents and 46% of caregiver respondents. Anxiety/depression was reported by 28% of PwH respondents. Reporting of pain and anxiety/depression was associated with disease severity. Whilst 62% of PwH who had experienced pain at any time point (n = 242) felt this was adequately addressed and treated at their HTC, only 24% of those who had experienced depression/anxiety (n = 127) felt this was adequately addressed. Disease severity was negatively associated with EQ‐5D‐5L utility value (p < .001). In the HTC survey, 4/5 and 2/5 agreed that pain and depression/anxiety, respectively, are adequately addressed.

Conclusions

Pain and depression/anxiety occur more frequently with increasing haemophilia severity, with negative impacts on health‐related quality of life. PwH with depression/anxiety or unaddressed pain could benefit from improved management strategies.

International consensus recommendations on the management of people with haemophilia B

Haemophilia B is a rare X-linked genetic deficiency of coagulation factor IX (FIX) that, if untreated, can cause recurrent and disabling bleeding, potentially leading to severe arthropathy and/or life-threatening haemorrhage. Recent decades have brought significant improvements in haemophilia B management, including the advent of recombinant FIX and extended half-life FIX. This therapeutic landscape continues to evolve with several non-factor replacement therapies and gene therapies under investigation. Given the rarity of haemophilia B, the evidence base and clinical experience on which to establish clinical guidelines are relatively sparse and are further challenged by features that are distinct from haemophilia A, precluding extrapolation of existing haemophilia A guidelines. Due to the paucity of formal haemophilia B-specific clinical guidance, an international Author Group was convened to develop a clinical practice framework. The group comprised 15 haematology specialists from Europe, Australia, Japan, Latin America and North America, covering adult and paediatric haematology, laboratory medicine and biomedical science. A hybrid approach combining a systematic review of haemophilia B literature with discussion of clinical experience utilized a modified Delphi format to develop a comprehensive set of clinical recommendations. This approach resulted in 29 recommendations for the clinical management of haemophilia B across five topics, including product treatment choice, therapeutic agent laboratory monitoring, pharmacokinetics considerations, inhibitor management and preparing for gene therapy. It is anticipated that this clinical practice framework will complement existing guidelines in the management of people with haemophilia B in routine clinical practice and could be adapted and applied across different regions and countries.

Safety and effectiveness of recombinant factor XIII‐A 2 in congenital factor XIII deficiency: Real‐world evidence

Background

Objective

Patients/Methods

Results

Conclusions

Gastrointestinal Bleeding in Congenital Bleeding Disorders

Gastrointestinal bleeding (GIB) is serious, intractable, and potentially life-threatening condition. There is considerable heterogeneity in GIB phenotypes among congenital bleeding disorders (CBDs), making GIB difficult to manage. Although GIB is rarely encountered in CBDs, its severity in some patients makes the need for a comprehensive and precise assessment of underlying factors and management approaches imperative. Initial evaluation of GIB begins with assessment of hematological status; GIB should be ruled out in patients with chronic anemia, and in presentations that include hematemesis, hematochezia, or melena. High-risk patients with recurrent GIB require urgent interventions such as replacement therapy for treatment of coagulation factor deficiency (CFD). However, the best management strategy for CFD-related bleeding remains controversial. While several investigations have identified CBDs as potential risk factors for GIB, research has focused on assessing the risks for individual factor deficiencies and other CBDs. This review highlights recent findings on the prevalence, management strategies, and alternative therapies of GIB related to CFDs, and platelet disorders.

Engineered Bio-inspired Multifunctional Peptide- and Protein-based Therapeutic Biomolecules for Better Wound Care

Developing non-immunogenic therapeutic biomolecules for facilitating blood clotting followed by wound healing via therapeutic angiogenesis, still remains a formidable challenge. Excessive blood loss of accident victims and battalions cause a huge number of deaths worldwide. Patients with inherited bleeding disorders face acute complications during injury and post-surgery. Biologically-inspired peptide-based hemostat can act as a potential therapeutic for handling coagulopathy. Additionally, non-healing wounds for patients having ischemic diseases can cause severe clinical complications. Advancement in stabilized growth-factor-based proangiogenic therapy may offer effective possibilities for the treatment of ischemic pathology. This review will discuss nature-inspired biocompatible stabilized peptide- and protein-based molecular medicines to serve unmet medical challenges for handling traumatic coagulopathy and impaired wound healing.

Hemophilic arthropathy: Current knowledge and future perspectives

Hemophilia A and B are rare X-linked inherited bleeding disorders caused by complete or partial deficiency in or the absence of coagulation factors VIII and IX. Recurrent joint bleeding (hemarthrosis) is the most frequent clinical manifestation of severe hemophilia. Unless appropriately managed, even subclinical hemarthrosis can lead to the development of hemophilic arthropathy, a disabling condition characterized by joint remodelling, chronic pain, and a reduced quality of life, and eventually requires joint replacement. Given the lack of specific treatments to reduce blood-induced synovitis, the prevention of bleeding is pivotal to the maintenance of joint health. Prophylactic coagulation factor replacement therapy using extended half-life recombinant drugs has significantly improved patients' quality of life by reducing the burden of intravenous injections, and the more recent introduction of nonreplacement therapies such as subcutaneous emicizumab injections has improved treatment adherence and led to the greater protection of patients with hemophilia A. However, despite these advances, chronic arthropathy is still a significant problem. The introduction of point-of-care ultrasound imaging has improved the diagnosis of acute hemarthrosis and early hemophilic arthropathy, and allowed the better monitoring of progressive joint damage, but further research into the underlying mechanisms of the disease is required to allow the development of more targeted treatment. In the meantime, patient management should be based on the risk factors for the onset and progression of arthropathy of each individual patient, and all patients should be collaboratively cared for by multidisciplinary teams of hematologists, rheumatologists, orthopedic surgeons, and physiotherapists at comprehensive hemophilia treatment centers.

Severe Rare Bleeding Disorders: A Single-center Experience

Although rare bleeding disorders (RBDs) are not common diseases, they are important for life-threatening bleedings and prophylaxis approaches, especially in severe forms. In this retrospective study, the authors have analyzed data from children with severe RBDs who were examined at the center over a period of 10 years to describe the distribution, clinical features, treatment patterns, and outcome of severe RBDs in patients. Data from all children (age under 18 y) with RBDs who were examined in the center between 2005 and 2015 were retrospectively reviewed. In total, 12 patients were included in the study. Four of the cases had factor (F) VII (33.3%), 6 had FX (50%), 1 had FXIII (8.3%), and 1 had fibrinogen deficiency (8.3%). Of the 12 children with severe RBDs, 8 (67%) experienced at least 1 major bleeding. Prophylaxis was applied to 10 patients. In conclusion, RBDs are more common in our country because of the high parental consanguinity rates. So, it is necessary to raise public awareness about the risks of consanguineous marriages and increase access to genetic counseling and testing facilities. Delayed diagnosis and lack of adequate prophylactic replacement therapy are the most important risk factors that increase life-threatening bleeding.

Practical considerations for nonfactor-replacement therapies in the treatment of haemophilia with inhibitors

New therapeutic agents for haemophilia with inhibitors that are in development or already licensed are expected to provide transformative treatment options. Many of these new therapies are not based on simply replacing the missing factor; new strategies include bispecific antibody technology that mimics factor VIII coagulation function (emicizumab), and inhibition of anticoagulant proteins such as tissue factor pathway inhibitor (eg PF-06741086) and antithrombin (eg fitusiran). These agents are administered subcutaneously and should significantly reduce treatment burden and increase the ability to deliver prophylaxis for patients. Limited real-world data and validated practical guidance on these recently licensed/upcoming treatments resulted in the authors convening to discuss recommendations on their use. Emicizumab is currently the only licenced nonfactor therapy; thus, our recommendations focus on this product. Target candidates for emicizumab prophylaxis are difficult-to-treat patients with haemophilia A and inhibitors and/or venous access issues, frequent bleeds and target joints. In case of breakthrough bleeding while receiving emicizumab, patients still require treatment with bypassing agents; the adjunct treatment of choice is recombinant activated factor VII. This treatment is also recommended to prevent bleeds in patients with inhibitors undergoing surgery. Our recommendations on suitable laboratory assays and monitoring new products, as well as the benefit of patient-reported outcomes (such as pain and physical activity levels), are included. We also briefly discuss future treatment options for patients with haemophilia B and inhibitors. Although these nonfactor treatments offer great promise, further data and real-world evidence are needed.

Optimizing language for effective communication of gene therapy concepts with hemophilia patients: a qualitative study

BACKGROUND

For communities of people living with hemophilia and other genetic conditions, gene therapy could represent a paradigm shift in treatment strategies. As investigational therapeutic modalities such as gene therapy become more widely used and discussed, there is a critical need for all stakeholders to communicate using a lexicon that is intelligible, accurate, consistent, and representative of novel treatments. In doing so, expectations can be more carefully managed and potential risks, benefits, and limitations better understood. In recognition of this need, a first-ever study of gene therapy lexicon was conducted using established methods of market research and linguistic analysis.

METHODS

Ninety-four participants representing hematologists, nurses, caregivers, and people with hemophilia A, in six countries (US, UK, Spain, Germany, France, Italy) took part in a series of in-depth interviews, face-to-face focus groups, an advisory board meeting, and online group interviews to develop, refine, and test verbal, written, and pictorial language concepts through a three-phase iterative process. Sessions were conducted in local languages using detailed discussion guides. Feedback from participants was captured using real-time instant-response dial testing to measure moment-by-moment emotional responses to language stimuli. Semiquantitative analysis of the responses informed selection of preferred language concepts for final testing, and qualitative discussion explored preference rationale. Participants also completed polling and forced rank and choice written exercises.

RESULTS

Study feedback showed that the hemophilia community has preferences around consistent lexicon to describe hemophilia and its management. Expert linguistic analysis of feedback from the three phases enabled agreement of a consensus lexicon of vocabulary and an optimized summary narrative for talking about gene therapy amongst people affected by hemophilia A. Preferences were largely consistent across audiences and countries, although some country-specific recommendations were made. A representative summary phrase was agreed: "Gene therapy is being studied in clinical trials with the aim to allow the body to produce factor VIII protein on its own".

CONCLUSIONS

The use of preferred language across different stakeholders increases understanding and comfort during discussions of novel and complex therapeutic modalities such as gene therapy. Consistent use of community-informed lexicon minimizes miscommunication and facilitates informed decision-making regarding potential future treatment opportunities.

Diagnosis, therapeutic advances, and key recommendations for the management of factor X deficiency

Factor X deficiency is a rare coagulation disorder that can be hereditary or acquired. The typology and severity of the associated bleeding symptoms are highly heterogeneous, adding to the difficulties of diagnosis and management. Evidence-based guidelines and reviews on factor X deficiency are generally limited to publications covering a range of rare bleeding disorders. Here we provide a comprehensive review of the literature on factor X deficiency, focusing on the hereditary form, and discuss the evolution in disease management and the evidence associated with available treatment options. Current recommendations advise clinicians to use single-factor replacement therapy for hereditary disease rather than multifactor therapies such as fresh frozen plasma, cryoprecipitate, and prothrombin complex concentrates. Consensus in treatment guidelines is still urgently needed to ensure optimal management of patients with factor X deficiency across the spectrum of disease severity.

Von Willebrand disease type 2N: An update

Quantitative or qualitative defects of von Willebrand factor (VWF) are responsible for the most common inherited bleeding disorder, von Willebrand disease (VWD). Type 2N VWD is an uncommon recessive disorder that results from gene mutations located in the region coding for the binding site of VWF for factor VIII (FVIII). This narrative review describes the pathophysiology, diagnostic procedures and treatment as well as the molecular biology of type 2N VWD. Although other VWF-dependent functions like binding to platelets and collagen are preserved, FVIII plasma levels are low due to the rapid clearance of this moiety in the absence or reduction of its binding to VWF. The diagnosis of type 2N should be considered in patients with low FVIII coagulant activity (FVIII:C) and disproportionally higher VWF antigen, especially when they present with an autosomal recessive pattern of inheritance. Because an accurate diagnosis is essential for genetic counseling and optimal treatment, type 2N must be distinguished from mild/moderate hemophilia A and its carrier state. This differential diagnosis can be obtained by using the laboratory assay of the FVIII binding capacity of VWF (VWF:FVIIIB) or analysis of the FVIII binding site on the VWF gene.

Low-dose surgical prophylaxis: Optimization of use of World Federation of Hemophilia Humanitarian Aid donated clotting factor concentrates to developing countries

BACKGROUND

Patients with hemophilia (PWH) might need surgical interventions during the course of their lives. Such medical interventions pose hemostatic challenges and requests infusion of clotting factor concentrates (CFCs) during peri and postoperative for variable periods to prevent bleeding and until complete wound healing. Access to CFCs to PWH living in resource limited settings is usually a challenge which makes surgical interventions either risky or not practical. Recently World Federation of Hemophilia (WFH) started a humanitarian aid program to channel CFCs into resource limited countries and which allowed the possibility to perform surgical interventions for PWH in these countries.

AIM OF WORK

To study safety and efficacy of using lower doses of CFCs for surgical prophylaxis.

METHODS

Review of literature and our center experience to demonstrate safety and efficacy of low dose surgical prophylaxis using CFCs RESULTS: Several elements can help using lower doses of CFCs for surgical prophylaxis in resource limited setting. These elements include severity of hemophilia, type of surgical procedure, the use of hemostatic surgical techniques, the type of CFCs, the mode of infusion of CFCs and finally the use of adjunctive therapies CONCLUSION: Management of surgical procedures for PWH in a multidisciplinary specialized hemophilia treatment centers with proper understanding of hemostatic and surgical challenges of the procedure can allow for safe and effective use of lower doses of CFCs for surgical prophylaxis.

Impact of SMTP Targeting Plasminogen and Soluble Epoxide Hydrolase on Thrombolysis, Inflammation, and Ischemic Stroke

Stachybotrys microspora triprenyl phenol (SMTP) is a large family of small molecules derived from the fungus S. microspora. SMTP acts as a zymogen modulator (specifically, plasminogen modulator) that alters plasminogen conformation to enhance its binding to fibrin and subsequent fibrinolysis. Certain SMTP congeners exert anti-inflammatory effects by targeting soluble epoxide hydrolase. SMTP congeners with both plasminogen modulation activity and anti-inflammatory activity ameliorate various aspects of ischemic stroke in rodents and primates. A remarkable feature of SMTP efficacy is the suppression of hemorrhagic transformation, which is exacerbated by conventional thrombolytic treatments. No drug with such properties has been developed yet, and SMTP would be the first to promote thrombolysis but suppress disease-associated bleeding. On the basis of these findings, one SMTP congener is under clinical study and development. This review summarizes the discovery, mechanism of action, pharmacological activities, and development of SMTP.

Peptide-based topical agents and intravenous hemostat for rapid hemostasis

Traumatic coagulopathy due to severe external injury and internal hemorrhage is life-threatening to accident victims and soldiers on the battlefield, causing considerable number of deaths worldwide. Patients with inherited bleeding disorders (such as haemophilia, von Willebrand disease, inherited qualitative platelet defects, and afibrinogenemia) also contribute to the vast number of deaths due to abnormal bleeding, and these patients are difficult to handle during surgery. Platelets and different plasma proteins play an essential role in blood coagulation and in the maintenance of the body's hemostatic balance. The improper function or deficiency of these factors cause abnormal bleeding. To address such bleeding disorders, external clotting agents (such as extracellular protein-inspired natural and synthetic peptide-based sealants and peptide-functionalized polymer/liposome-based sealants) have been developed by different groups of researchers. The primary focus of this review is to provide molecular insights into the existing biologically inspired peptide-based sealants, highlighting the advantages and limitations of such reported designed sealants to handle blood clotting, and also provide insights into the design of improved next-generation surgical sealants.

Rare bleeding disorders: spectrum of disease and clinical manifestations in the Pakistani population

Background

Rare inherited coagulation factor deficiencies constitute an important group of bleeding disorders. A higher frequency of these disorders is seen in areas of high consanguinity. Our aim was to study the prevalence and spectrum of rare inherited bleeding disorders, characterize the severity of the deficiencies, identify different clinical manifestations, and evaluate different treatments provided.

Methods

This cross-sectional study was conducted in the Department of Haematology, Armed Forces Institute of Pathology Rawalpindi, between January 2014 and December 2018. A detailed history was taken, and an examination was performed. The signs and symptoms were noted, and the patients were diagnosed on the basis of a coagulation profile. The disease severity was assessed using factor assays.

Results

Among 2,516 patients with suspected coagulation disorders, 774 (30.8%) had an inherited bleeding disorder. Of the 774 patients, 165 (21.3%) had a rare bleeding disorder; 91 (55.2%) of them were males, and 74 (44.9%) were females, with a male-to-female ratio of 1.2:1. The median patient age was 9 years 3 months. The most common disorder was factor VII deficiency (46 patients, 27.9%). The most common clinical presentation was bruising in 102 (61.8%) and gum bleeding in 91 (55.2%) patients.

Conclusion

The most common rare bleeding disorder in our population is factor VII deficiency. The prevalence of these bleeding disorders is high in our population due to a high number of consanguineous marriages.

A mutated factor X activatable by thrombin corrects bleedings in vivo in a rabbit model of antibody-induced hemophilia A

Rendering coagulation factor X sensitive to thrombin was proposed as a strategy that can bypass the need for factor VIII. In this paper, this non-replacement strategy was evaluated in vitro and in vivo in its ability to correct factor VIII but also factor IX, X and XI deficiencies. A novel modified factor X, named Actiten, was generated and produced in the HEK293F cell line. The molecule possesses the required post-translational modifications, partially keeps its ability to be activated by RVV-X, factor VIIa/tissue factor, factor VIIIa/factor IXa and acquires the ability to be activated by thrombin. The potency of the molecule was evaluated in respective deficient plasmas or hemophilia A plasmas, for some with inhibitors. Actiten corrects dose dependently all the assayed deficient plasmas. It is able to normalize the thrombin generation at 20 μg/mL showing however an increased lagtime. It was then assayed in a rabbit antibody-induced model of hemophilia A where, in contrast to recombinant factor X wild-type, it normalized the bleeding time and the loss of hemoglobin. No sign of thrombogenicity was observed and the generation of activated factor X was controlled by the anticoagulation pathway in all performed coagulation assays. This data indicates that Actiten may be considered as a possible non replacement factor to treat hemophilia's with the advantage of being a zymogen correcting bleedings only when needed.

Prevalence of FVIII Inhibitors Among Children with Hemophilia A: Experience at the Jordanian Royal Medical Services

Introduction:

Replacement therapy is constantly required by Hemophilia A (HA) patients lacking coagulation factor VIII (FVIII). The most serious complication of this treatment is the development of neutralizing antibodies (inhibitors).

Aim:

The aim of this study is to determine the frequency of FVIII inhibitors among children treated for HA at the Jordanian Royal Medical Services.

Methods:

A total of 165 diagnosed HA patients receiving on-demand treatment, were tested for FVIII inhibitors between 2003 and 2018. The age range was 6 months to 16 years. Coagulation and inhibitor screening assays were performed, followed by Bethesda assay for inhibitor-positive samples to quantify FVIII inhibitor titers.

Results:

Out of the 165 patients, 111 had severe hemophilia with FVIII level < 1%, 26 had moderate hemophilia with FVIII levels of 1–5% and 28 had mild hemophilia with FVIII levels of > 5%. Twenty patients had FVIII inhibitors, of whom 18 had high titers, 2 had low titers. The mean inhibitor level in low (titer) responders was 2.40 ± 0.85 BU, as opposed to 116.25 ±169.25 BU in high (titer) responders. In terms of disease severity, 18 of the 20 patients with FVIII inhibitors had severe HA, whereas two had moderate HA. No inhibitors were encountered in the mild HA group.

Conclusion:

Inhibitors only developed in moderate and severe cases of HA. The severity of the disease and age were the main contributing factors. The association between family history of inhibitors and the incidence of inhibitor formation warrants genetic evaluations to look for relevant mutations.

Synergistic Effect of Bypassing Agents and Sequence Identical Analogue of Emicizumab and Fibrin Clot Structure in the In Vitro Model of Hemophilia A

Development of inhibitors to factor VIII (FVIII) occurs in approximately 30% of severe hemophilia A (HA) patients. These patients are treated with bypassing agents (activated prothrombin complex concentrate [aPCC] and recombinant activated FVII-rFVIIa). Recently, a bispecific FIX/FIXa- and FX/FXa-directed antibody (emicizumab) has been approved for the treatment of HA patients with inhibitors. However, the data from clinical studies imply that coadministration of emicizumab and bypassing agents, especially aPCC, could have a thrombotic effect.

This study was aimed to address the question of potential hypercoagulability of emicizumab and bypassing agents' coadministration, we have investigated fibrin clot formation and structure in the in vitro model of severe HA after adding sequence-identical analogue (SIA) of emicizumab and bypassing agents.

Combined overall hemostasis potential (OHP) and fibrin clot turbidity assay was performed in FVIII-deficient plasma after addition of different concentrations of SIA, rFVIIa, and aPCC. Pooled normal plasma was used as control. The fibrin clots were analyzed by scanning electron microscopy (SEM).

OHP and turbidity parameters improved with the addition of aPCC, while therapeutic concentrations of rFVIIa did not show substantial improvement. SIA alone and in combination with rFVIIa or low aPCC concentration improved OHP and turbidity parameters and stabilized fibrin network, while in combination with higher concentrations of aPCC expressed hypercoagulable pattern and generated denser clots.

Our in vitro model suggests that combination of SIA and aPCC could potentially be prothrombotic, due to hypercoagulable changes in fibrin clot turbidity and morphology. Additionally, combination of SIA and rFVIIa leads to the formation of stable clots similar to normal fibrin clots.

Concomitant Use of rFVIIa and Emicizumab in People with Hemophilia A with Inhibitors: Current Perspectives and Emerging Clinical Evidence

Emicizumab, a humanized, bi-specific, monoclonal antibody subcutaneously administered, mimicking the function of FVIIIa, represents a milestone in treatment of patients affected by hemophilia A complicated with inhibitors. The HAVEN 1 and 2 studies have clearly established its superiority compared to bypassing agents for routine prophylaxis in preventing or reducing bleeding episodes in adult and pediatric patients with inhibitors. However, its protection against bleeding is only partial, and concomitant use of a bypassing agent may be required with potential prothrombotic risk. The emicizumab Phase III trials (HAVEN 1, 2 and 4) have shown that the traditional bypassing agents, activated prothrombin complex concentrates or recombinant activated factor VII (rFVIIa), may be necessary for the treatment of breakthrough bleeds or surgery management. A post hoc analysis in particular has shown that the concomitant use of emicizumab and rFVIIa is safe and no thrombotic events have been described. The review describes the state of the art of the concomitant use of emicizumab and rFVIIa for treating acute bleeding and surgeries, its efficacy and safety and the lack of thrombotic events associated with this treatment modality. Data still derive mainly from HAVEN trials; however, the availability of emicizumab in clinical practice is progressively increasing the number of patients treated and no adverse events directly attributed to this agent have occurred. The availability of guidelines for the use and dosing of rFVIIa during emicizumab prophylaxis is useful in clinical practice for managing suspected or ongoing bleeding, emergency situations and elective invasive procedures. In the next years, careful prospective post-licensure surveillance to monitor safety of rFVIIa use during prophylaxis with emicizumab is highly recommended.

Genetic analysis of a compound heterozygous patient with congenital factor X deficiency and regular replacement therapy with a prothrombin complex concentrate

Congenital factor X (FX) deficiency is a rare bleeding disorder with an incidence of one in one million. The proband, a 2-year-old girl, exhibited easy bruising and a history of umbilical cord bleeding at birth. Prothrombin time (> 40 s) and activated partial thromboplastin time (65.0 s) were prolonged. Marked declines in FX activity (< 1%) and FX antigen levels (5%) were also observed. Genetic analysis of the proband identified two types of single-base substitutions, c.353G>A (p.Gly118Asp) and c.1303G>A (p.Gly435Ser), indicating compound heterozygous congenital FX deficiency. Genetic analysis of family members revealed that her father and older sister (5-year-old) were also heterozygous for p.Gly118Asp, and that her mother was heterozygous for p.Gly435Ser. To improve the bleeding tendency, the proband received regular replacement of 500 units of PPSB-HT, a prothrombin complex concentrate (PCC). Following continued regular replacement of 500 units of PPSB-HT once per week, the proband has exhibited no bleeding tendencies and no new bruises have been observed. There are no previous report of the use of PPSB-HT for regular FX replacement. Regular replacement therapy with PPSB-HT may be an effective method for preventative control of bleeding tendencies in FX deficiency.

Updated overview on von Willebrand disease: focus on the interest of genotyping

Introduction: Von Willebrand disease (VWD) is the most common inherited bleeding disorder, characterized by a quantitative or qualitative defect of von Willebrand factor (VWF), a multimeric glycoprotein crucial for primary hemostasis and coagulation. VWD pathophysiology is heterogeneous as it includes several types and subtypes which therapeutic management is different. The mainstays of VWD treatment are desmopressin and replacement therapy based on both plasma-derived concentrates and a recently developed recombinant VWF. VWD definitive diagnosis is achieved by a battery of phenotypic biologic assays and genotyping is currently performed mostly for research.Areas covered: This narrative review will firstly present a general overview on VWD epidemiology, pathophysiology, classification, clinics, phenotypic biologic diagnosis, and treatment. Secondly, a focus on VWD genotyping will be presented with specific emphasis on the evolution of its technical aspects, its applications for research dedicated to a better understanding of VWD pathophysiology and epidemiology and its interest in both a faster diagnosis and an optimal treatment of VWD.Expert opinion: Based on analysis of the literature, it can be concluded that the fast evolution of genetic techniques together with the development of innovating treatments may significantly change diagnostic flow charts for VWD and their use for specific and personalized treatment.

Real-life experience in switching to new extended half-life products at European haemophilia centres

The concept of replacement therapy in haemophilia is changing significantly thanks to the switch from standard products to extended half-life products. These novel drugs are showing beneficial effects overcoming current prophylaxis limitations by reducing the infusion frequency, maintaining a higher trough level to ensure a lower risk of bleeding, and making treatment significantly less distressing to patients by improving the quality of life. Real-life data on the efficacy of novel drugs and their impact on routine management of haemophilia A and B patients are still limited. This manuscript reports the results of a European survey conducted by the European Association for Haemophilia and Allied Disorders (EAHAD) at the beginning of 2018 on the clinical management of patients using extended half-life recombinant FVIII and FIX fusion products, since at the time of the survey none of the PEGylated products were available yet. We report data on the efficacy of these novel drugs by 33 European haemophilia centres that have already switched to extended half-life fusion products, showing a significant reduction in the number of infusions and a satisfactory trough levels in the clinical care of haemophilia patients, with a greater impact for haemophilia B.

The use of prophylaxis in the treatment of rare bleeding disorders

Rare bleeding disorders (RBDs) are a heterogeneous group of coagulation factor deficiencies that include fibrinogen, prothrombin, α₂-antiplasmin, plasminogen activator inhibitor-1, and factors II, V, V/VIII, VII, X, XI and XIII. The incidence varies based upon the disorder and typically ranges from 1 in 500,000 to 1 per million population. Symptoms vary with the disorder and residual level of the clotting factor, and can range from relatively minor such as epistaxis, to life threatening, such as intracranial hemorrhage. Rapid treatment of bleeding episodes in individuals with severe bleeding phenotypes is essential to preserve life or limb and to prevent long-term sequelae; therapeutic options depend on the deficiency and range from plasma-derived (eg, fresh frozen plasma, prothrombin complex concentrates, factor X concentrate) to highly purified and recombinant single factor concentrates. The rarity of these disorders limits the feasibility of conventional prospective clinical trials; instead, clinicians rely upon registries, published case reports/series and experience to guide treatment. In some disorders, long-term prophylactic therapy is administered in response to the bleeding phenotype in an individual patient or based on the known natural history and severity of the deficiency. Intermittent prophylaxis, surrounding surgery, pregnancy, labor, and menstruation may be required to prevent or control excessive bleeding. This review summarizes therapeutic options, guidelines, recommendations and observations from the published literature for long-term, surgical, gynecological, and obstetric prophylaxis in deficiencies of fibrinogen; prothrombin; factors II, V, V/VIII, VII, X, XI and XIII; combined vitamin-K dependent factors; α2-antiplasmin; and plasminogen activator inhibitor 1. Platelet disorders including Glanzmann's thrombasthenia and Bernard-Soulier syndrome are also addressed.

The Neonatal Fc Receptor (FcRn): A Misnomer?

Antibodies are essential components of an adaptive immune response. Immunoglobulin G (IgG) is the most common type of antibody found in circulation and extracellular fluids. Although IgG alone can directly protect the body from infection through the activities of its antigen binding region, the majority of IgG immune functions are mediated via proteins and receptors expressed by specialized cell subsets that bind to the fragment crystallizable (Fc) region of IgG. Fc gamma (γ) receptors (FcγR) belong to a broad family of proteins that presently include classical membrane-bound surface receptors as well as atypical intracellular receptors and cytoplasmic glycoproteins. Among the atypical FcγRs, the neonatal Fc receptor (FcRn) has increasingly gained notoriety given its intimate influence on IgG biology and its ability to also bind to albumin. FcRn functions as a recycling or transcytosis receptor that is responsible for maintaining IgG and albumin in the circulation, and bidirectionally transporting these two ligands across polarized cellular barriers. More recently, it has been appreciated that FcRn acts as an immune receptor by interacting with and facilitating antigen presentation of peptides derived from IgG immune complexes (IC). Here we review FcRn biology and focus on newer advances including how emerging FcRn-targeted therapies may affect the immune responses to IgG and IgG IC.

Clinical advances in gene therapy updates on clinical trials of gene therapy in haemophilia

Gene therapy is rapidly becoming a new therapeutic strategy for haemophilia A and B treatment. In the 1990s, studies in animal models showed that adeno-associated vectors (AAV) exhibited an efficient expression of factor IX (FIX). In the first clinical trial in patients with haemophilia B, therapeutic levels of FIX were documented but the expression remained only for few weeks. Subsequently, improvements in vector design, such as the use of different AAV serotypes, the development of the self-complementary vector, the engineering of the transgene with codon optimization and liver-specific expression cassette resulted in circulating FIX level between 2% and 5% for long-lasting period. Recently, a natural gain of function FIX variant (Padua) inserted in the F9 cDNA improved the expression of FIX achieving a level of more than 30% resulting in cessation of infusions and in a greatly reduction of bleeding events. Encouraging clinical progresses have been also obtained from trials of gene therapy for haemophilia A. Transgene expression persisted for three years with circulating FVIII activity levels of 52.3% in patients treated with AAV vector containing a codon-optimized F8 cDNA. A complication, reported in both clinical trials for haemophilia A and B, was the elevation of liver enzymes, which resolved with steroid treatment in a large group of patients. However, to date, the pathophysiological mechanism for the liver toxicity remains still unclear. Clinical trials with adeno-associated vectors have documented a significant success for haemophilia gene therapy demonstrating potential to transform haemophilia treatment offering hope for a long-term expression.

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.

Molecular Mechanisms and Determinants of Innovative Correction Approaches in Coagulation Factor Deficiencies

Molecular strategies tailored to promote/correct the expression and/or processing of defective coagulation factors would represent innovative therapeutic approaches beyond standard substitutive therapy. Here, we focus on the molecular mechanisms and determinants underlying innovative approaches acting at DNA, mRNA and protein levels in inherited coagulation factor deficiencies, and in particular on: (i) gene editing approaches, which have permitted intervention at the DNA level through the specific recognition, cleavage, repair/correction or activation of target sequences, even in mutated gene contexts; (ii) the rescue of altered pre-mRNA processing through the engineering of key spliceosome components able to promote correct exon recognition and, in turn, the synthesis and secretion of functional factors, as well as the effects on the splicing of missense changes affecting exonic splicing elements; this section includes antisense oligonucleotide- or siRNA-mediated approaches to down-regulate target genes; (iii) the rescue of protein synthesis/function through the induction of ribosome readthrough targeting nonsense variants or the correction of folding defects caused by amino acid substitutions. Overall, these approaches have shown the ability to rescue the expression and/or function of potentially therapeutic levels of coagulation factors in different disease models, thus supporting further studies in the future aimed at evaluating the clinical translatability of these new strategies.

Treatment of rare factor deficiencies other than hemophilia

The deficiency of fibrinogen, prothrombin, factor V (FV), FVII, FVIII, FIX, FX, FXI, and FXIII, called rare coagulation disorders (RCDs), may result in coagulopathies leading to spontaneous or posttrauma and postsurgery hemorrhages. RCDs are characterized by a wide variety of symptoms, from mild to severe, which can vary significantly from 1 disease to another and from 1 patient to another. The most typical symptoms of all RCDs are mucosal bleedings and bleeding at the time of invasive procedures, whereas other life-threatening symptoms such as central nervous system bleeding and hemarthroses are mostly present only in some deficiencies (afibrinogenemia, FX, and FXIII). At variance with hemophilia A and B and von Willebrand disease, RCDs are much less prevalent, ranging from 1 case in 500 000 to 1 in 2 million in the general population. Their clinical heterogeneity associated with the low number of patients has led to a delay in the development of appropriate therapies. Indeed, a similar heterogeneity can also be found in the treatment products available, ranging from the specific recombinant proteins to treat FVII- and FXIII-deficient patients to the complete absence of specific products to treat patients with FII or FV deficiencies, for whom prothrombin complex concentrates or fresh frozen plasma are, to date, the only option. The recent development of novel hemostatic approaches for hemophilia, such as the use of nonsubstitutive therapy as RNA interference, anti-tissue factor pathway inhibitor, and the gene therapy aimed at improving the patient's quality of life may also have an important role in the treatment of patients with RCDs in the future.

Prophylactic versus on-demand treatments for hemophilia: advantages and drawbacks

INTRODUCTION

Early long-term prophylaxis is the standard of care to prevent joint bleeding and chronic arthropathy in patients with severe hemophilia. Areas covered: Despite the obvious prophylaxis advantages upon the clinical outcomes, there are still several drawbacks to be addressed for the optimal patients' compliance. Frequency of treatment due to short half-life of conventional FVIII and FIX concentrates, difficult venous access, adherence to the prescribed therapy and costs may represent significant critical issues. The development of inhibitors also makes replacement therapy ineffective, preventing patients from receiving long-term prophylaxis. This paper will review these drawbacks and the tools to overcome these limitations, mainly thanks to the use of extended half-life products and the development of novel non-conventional therapeutic approaches. Expert commentary: The use of extended half-life products may help in reducing the burden of the frequent intravenous administration and in better tailoring an individualized prophylaxis. The development of novel therapeutic approaches, like the bi-specific antibody mimicking the coagulation function of FVIII or inhibition of anticoagulant proteins may facilitate prophylaxis treatment not only in patients with inhibitors, but also in severe hemophilia patients without inhibitors. Exciting opportunities are emerging for improving prophylaxis in hemophilia.

In vitro studies show synergistic effects of a procoagulant bispecific antibody and bypassing agents

Essentials Patients with hemophilia A and inhibitors receiving emicizumab experience breakthrough bleeding. Safety concerns may exist when combining emicizumab with bypassing agents. Combined bypassing agent and bispecific antibody increased thrombin generation up to 17-fold. Thrombotic effects should be considered when combining emicizumab with plasma bypassing agent.

SUMMARY

Background Investigational non-factor products such as emicizumab offer a treatment option for patients with hemophilia and inhibitors. However, their mechanism of action raises questions regarding safety when they are combined with treatments for breakthrough bleeding. Objectives To evaluate in vitro thrombin generation (TG) and clot formation for combinations of activated prothrombin complex concentrate (aPCC), recombinant activated factor VII (rFVIIa), and a sequence-identical analog of emicizumab (SIA). Methods Therapeutic concentrations of SIA (20-600 nm) alone or with aPCC (0.05-1 U mL-1 ), isolated aPCC components or rFVIIa (0.88-5.25 μg mL-1 ) were tested for TG and compared with reference ranges for healthy donor plasma. Coagulation of FVIII-inhibited blood was determined with a widely established method, i.e. rotational thromboelastometry (ROTEM), and confirmed with the Total Thrombus-formation Analysis System. Results and conclusions SIA (600 nm) or aPCC (0.5 U mL-1 ) alone resulted in peak thrombin levels of 21.4 nm and 38.6 nm, respectively, both of which are lower than normal (83.7 ± 29.8 nm). SIA plus aPCC (0.5 U mL-1 ) increased the peak thrombin level 17-fold over SIA alone, exceeding the reference plasma value by 4.2-fold. This hypercoagulable effect occurred with 600 nmSIA combined with as little as 0.25 U mL-1 aPCC, confirmed by ROTEM. FIX was the main driver for enhanced TG. SIA plus rFVIIa (1.75 μg mL-1 ) induced a 1.8-fold increase in the peak thrombin level in platelet-rich plasma, but it did not reach the normal range. These in vitro experiments demonstrate excessive TG after administration of a combination of aPCC and SIA at clinically relevant doses. Careful judgement may be required when breakthrough bleeding is treated in patients receiving emicizumab.

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.

Nonacog Beta Pegol: A Review in Haemophilia B

Nonacog beta pegol [Refixia® (EU)] is an intravenously-administered, glycoPEGylated recombinant factor IX (FIX), with an extended terminal half-life. It is approved in the EU for the treatment and prophylaxis of bleeding in patients aged ≥ 12 years with haemophilia B. The therapeutic efficacy and safety of nonacog beta pegol was demonstrated in the phase 3 Paradigm trials in previously treated adolescents and adults with haemophilia B. In Paradigm 2, nonacog beta pegol showed good haemostatic effects when treating bleeds on-demand, and reduced annualized bleeding rates when used as a once-weekly prophylaxis. It also improved some health-related quality of life measures in adult patients. The longer-term efficacy of nonacog beta pegol was demonstrated in the open-label extension Paradigm 4 trial. In Paradigm 3, nonacog beta pegol effectively maintained intraoperative and postoperative haemostasis. Nonacog beta pegol was well tolerated in phase 3 clinical trials in patients with haemophilia B, with no evidence of FIX inhibitor formation, allergic reactions or thromboembolic complications. In conclusion, nonacog beta pegol is effective and well tolerated in the on-demand, prophylaxis and perioperative settings in adolescent and adults with haemophilia B. Its extended half-life allows for once-weekly prophylaxis. Therefore, nonacog beta pegol is a useful additional treatment option for patients with haemophilia B.

Underestimation of N-glycoPEGylated factor IX one-stage clotting activity owing to contact activator-impaired activation

BACKGROUND

In clinical practice, factor IX (FIX) activity is routinely quantified by measurement of the activated partial thromboplastin time (APTT) in a one-stage (OS) FIX clotting assay. APTT reagents provide a contact activator and phospholipid surfaces required for triggering and sustaining the plasma clotting process. The large diversity in reagent components is reflected in the variable recovery of nonacog beta pegol (N9-GP; N-glycoPEGylated recombinant FIX) activity when assayed against a FIX standard. This variation warrants mechanistic studies and is plausibly attributable to the nature and amount of contact activator.

OBJECTIVE

To identify the cause of the N9-GP activity underestimation observed with a heterogeneous group of APTT reagents.

METHODS

Experiments mimicking the clotting phase (omitting the contact activation phase) of the OS assay, complemented by measurements of activated factor XI (FXIa) activity, were performed to characterize and explain the influence of APTT reagents/contact activators on the conversion of N9-GP and regular FIX (N9) to activated FIX (FIXa).

RESULTS

In the presence of an intact underestimating APTT reagent or the isolated contact activator, clotting phase activation of N9-GP proceeded at a reduced rate compared with that of N9. APTT reagent and contact activator negatively affected the activity of FXIa, conceivably as a consequence of FXIa adsorption. Thus, activation of FIX apparently poses a greater steric challenge after polyethylene glycol (PEG) conjugation.

CONCLUSIONS

Some OS clotting assay contact activators reduce FXIa-mediated activation of N9-GP to a larger degree than that of N9, causing underestimation of N9-GP activity of potential clinical significance.

Targeting of Antithrombin in Hemophilia A or B with RNAi Therapy

BACKGROUND

Current hemophilia treatment involves frequent intravenous infusions of clotting factors, which is associated with variable hemostatic protection, a high treatment burden, and a risk of the development of inhibitory alloantibodies. Fitusiran, an investigational RNA interference (RNAi) therapy that targets antithrombin (encoded by SERPINC1), is in development to address these and other limitations.

METHODS

In this phase 1 dose-escalation study, we enrolled 4 healthy volunteers and 25 participants with moderate or severe hemophilia A or B who did not have inhibitory alloantibodies. Healthy volunteers received a single subcutaneous injection of fitusiran (at a dose of 0.03 mg per kilogram of body weight) or placebo. The participants with hemophilia received three injections of fitusiran administered either once weekly (at a dose of 0.015, 0.045, or 0.075 mg per kilogram) or once monthly (at a dose of 0.225, 0.45, 0.9, or 1.8 mg per kilogram or a fixed dose of 80 mg). The study objectives were to assess the pharmacokinetic and pharmacodynamic characteristics and safety of fitusiran.

RESULTS

No thromboembolic events were observed during the study. The most common adverse events were mild injection-site reactions. Plasma levels of fitusiran increased in a dose-dependent manner and showed no accumulation with repeated administration. The monthly regimen induced a dose-dependent mean maximum antithrombin reduction of 70 to 89% from baseline. A reduction in the antithrombin level of more than 75% from baseline resulted in median peak thrombin values at the lower end of the range observed in healthy participants.

CONCLUSIONS

Once-monthly subcutaneous administration of fitusiran resulted in dose-dependent lowering of the antithrombin level and increased thrombin generation in participants with hemophilia A or B who did not have inhibitory alloantibodies. (Funded by Alnylam Pharmaceuticals; ClinicalTrials.gov number, NCT02035605 .).

Peptide Mimetic Drugs for Modulating Thrombosis and Hemostasis

Preclinical Research Hemostasis is the complex physiological process that stems bleeding at an injury site while simultaneously maintaining unobstructed circulation in other areas of the body. This system is kept in balance with finely tuned regulation by pro- and antithrombotic agents. When this balance is thrown out of equilibrium, uncontrolled bleeding, or thrombotic complications can occur. Because of the high number of hemostatic disorders, researchers are continually searching for improved technologies for controlling coagulation. Recently, peptide mimetic strategies have been employed to target and regulate various stages of the coagulation cascade. In this review, we present an overview of the coagulation cascade and provide a summary of various peptide-mimetic approaches for its modulation. Drug Dev Res 78 : 236-244, 2017. © 2017 Wiley Periodicals, Inc.