Relationship between plasma tissue Factor Pathway Inhibitor (TFPI) levels, thrombin generation and clinical risk of bleeding in patients with severe haemophilia A or B.

INTRODUCTION: Bleeding severity in severe haemophilic patients, with low thrombin generation (TG) capacity, can vary widely between patients, possibly reflecting differences in tissue factor pathway inhibitor (TFPI) level. AIM: To compare free TFPI (fTFPI) levels in patients with severe haemophilia A (sHA) and severe haemophilia B (sHB) and to investigate in these patients as a whole the relationships between bleeding and TG potential, between TG potential and fTFPI level and between fTFPI level and bleeding tendency. METHODS: Data on bleeding episodes retrospectively recorded during follow-up visits over 5-10 years were collected and used to calculate the annualised joint bleeding rate (AJBR). fTFPI levels and basal TG parameters were determined in platelet-poor plasma (PPP) and platelet-rich plasma (PRP) using calibrated automated tomography (CAT). RESULTS: Mean fTFPI levels did not differ significantly between sHA (n = 34) and sHB (n = 19) patients. Mean values of endogenous thrombin potential (ETP) and thrombin peak (peak) in PPP and PRP were two-fold higher when fTFPI levels < 9.4 versus > 14.3 ng/mL. In patients treated on demand, ETP and peak in PRP were doubled when AJBR was ≤ 4.9 $ \le 4.9$ , AJBR being halved in patients with a low fTFPI level (9.4 ng/mL). In patients on factor prophylaxis, no association was found between TG parameters and either fTFPI level or AJBR. CONCLUSION: In patients treated on demand, bleeding tendency was influenced by fTFPI levels, which in turn affected basal TG potential. In patients on prophylaxis, bleeding tendency is probably determined primarily by the intensity of this treatment.

Molecular analysis of severe hemophilia B in Indian families: Identification of mutational hotspot and novel variants.

INTRODUCTION: Hemophilia B is associated with molecular heterogeneity, with more than 1200 unique variants in the F9 gene. We hereby describe the mutational spectrum of severe hemophilia B patients presenting in a tertiary-care center in India. METHOD: DNA was extracted from peripheral blood samples of 35 diagnosed severe hemophilia B patients belonging to 32 families, and were subjected to Sanger sequencing. Determination of the effect of novel variants on the protein structure and correlation between genotype and phenotype was attempted using in-silico tools. RESULTS: Twenty-seven different mutations were detected in 30 probands, including 20 known and 7 novel variants. Also, we found one suspected case of whole gene deletion. The serine peptidase domain harbored most of the variants (48.1%). Inhibitory antibodies were found in two patients. CONCLUSIONS: This study provides a comprehensive mutational spectrum and mutation screening strategy by Sanger sequencing of F9 gene in severe hemophilia B patients, in a resource-constraint setting.

Hemostatic Management in an Infant With Neuroblastoma and Severe Hemophilia B With Extended Half-life Recombinant Factor IX Fusion Protein.

In the rare co-occurrence of childhood cancer and severe hemophilia, hemostatic management is of paramount therapeutic importance. We present the case of an 11-month-old boy with severe congenital hemophilia B, who was diagnosed with metastatic high-risk neuroblastoma. He consequently developed paraneoplastic coagulopathy with life-threatening tumor hemorrhage and intracranial hemorrhage, showing central nervous system relapse. Management consisted of factor IX replacement with extended half-life factor IX fusion protein, adjusted to bleeding risk. Additional interventions included factor XIII, fibrinogen, fresh frozen plasma, tranexamic acid, and platelet transfusions. The half-life of factor IX products was markedly reduced requiring close factor IX monitoring and adequate replacement. This intensified treatment allowed chemotherapy, autologous stem cell transplantation, and GD2 antibody immune therapy without bleeding or thrombosis.

Factor-mimetic and rebalancing therapies in hemophilia A and B: the end of factor concentrates?

Hemophilia A (HA) and B are inherited bleeding disorders caused by a deficiency of factor VIII or factor IX, respectively. The current standard of care is the administration of recombinant or purified factor. However, this treatment strategy still results in a high economic and personal burden to patients, which is further exacerbated by the development of inhibitors-alloantibodies to factor. The treatment landscape is changing, with nonfactor therapeutics playing an increasing role in what we consider to be the standard of care. Emicizumab, a bispecific antibody that mimics the function of factor VIIIa, is the first such nonfactor therapy to gain US Food and Drug Administration approval and is rapidly changing the paradigm for HA treatment. Other therapies on the horizon seek to target anticoagulant proteins in the coagulation cascade, thus "rebalancing" a hemorrhagic tendency by introducing a thrombotic tendency. This intricate hemostatic balancing act promises great things for patients in need of more treatment options, but are these other therapies going to replace factor therapy? In light of the many challenges facing these therapies, should they be viewed as a replacement of our current standard of care? This review discusses the background, rationale, and potential of nonfactor therapies as well as the anticipated pitfalls and limitations. This is done in the context of a review of our current understanding of the many aspects of the coagulation system.

Current status of haemophilia inhibitor management in mainland China: a haemophilia treatment centres survey on treatment preferences and real-world clinical practices.

To investigate the current experience and expertise for haemophilia inhibitor patient management in haemophilia treatment centres (HTCs) in mainland China. Questionnaires were distributed to 'tertiary tier A' hospital HTCs across China to collect information on treatment preferences for bleeding control, prophylaxis and inhibitor eradication, as well as their regimens in real-world clinical practice. Of 40 questionnaires distributed, 39 were returned. In all, 38 were analysable for treatment preferences and 34 for actual clinical practice. For haemostatic treatment, 76·3% (29/38) HTCs preferred activated recombinant human Factor VII (rFVIIa). In clinical practice, the most widely used by-pass agent was prothrombin complex concentrate (26 HTCs). Although 65·8% (25/38) of HTCs believed prophylaxis treatment was necessary, it was prescribed in only 12. Similarly, 65·8% (25/38) of HTCs believed immune tolerance induction (ITI) therapy was necessary but only 14·8% (92/622) of patients in 19 HTCs received low-dose ITI treatment. HTCs in relatively economically developed cities (with higher-than-average per-capita gross domestic product) had better access to haemostatic treatment, coagulation testing and were more likely to provide prophylaxis and ITI in practice. The present survey showed there were gaps in haemophilia inhibitor care between the HTC physicians' preferences and their actual clinical practice. More specific care guidelines, education and clinical decision support tools are needed to guide clinical practice.

Gene therapy for hemophilia: Current status and laboratory consequences.

Since the cloning and characterization of the factor VIII (FVIII) and factor IX genes in the mid-1980s, gene therapy has been perceived as having significant potential for the treatment of severe hemophilia. Now, some 35 years later, these proposals are close to being realized through the licensing of the first clinical gene therapy product. Adeno-associated viral vector-mediated gene therapy for hemophilia A and B has been extensively investigated in preclinical models over the past 20 years, and since 2011, there has been increasing evidence in early phase clinical trials that this therapeutic strategy can provide safe and effective rescue of the hemostatic phenotype in severe hemophilia. As the uptake of hemophilia gene therapy progresses, it is clear that many aspects of the gene therapy process require crucial laboratory support to ensure safe and effective outcomes from his new therapeutic paradigm. These laboratory contributions extend from evaluations of the gene therapy vehicle, assessments of the patient immune status for the vector, and ultimately the performance of assays to determine the hemostatic benefit of the gene therapy and potentially of its long-term safety on the host genome. As with many aspects of past hemophilia care, the safe and effective delivery of gene therapy will require an informed and coordinated contribution from laboratory science.

Fusion of engineered albumin with factor IX Padua extends half-life and improves coagulant activity.

The short half-life of coagulation factor IX (FIX) for haemophilia B (HB) therapy has been prolonged through fusion with human serum albumin (HSA), which drives the neonatal Fc receptor (FcRn)-mediated recycling of the chimera. However, patients would greatly benefit from further FIX-HSA half-life extension. In the present study, we designed a FIX-HSA variant through the engineering of both fusion partners. First, we developed a novel cleavable linker combining the two FIX activation sites, which resulted in improved HSA release. Second, insertion of the FIX R338L (Padua) substitution conferred hyperactive features (sevenfold higher specific activity) as for FIX Padua alone. Furthermore, we exploited an engineered HSA (QMP), which conferred enhanced human (h)FcRn binding [dissociation constant (KD ) 0·5 nM] over wild-type FIX-HSA (KD 164·4 nM). In hFcRn transgenic mice, Padua-QMP displayed a significantly prolonged half-life (2·7 days, P < 0·0001) versus FIX-HSA (1 day). Overall, we developed a novel FIX-HSA protein with improved activity and extended half-life. These combined properties may result in a prolonged functional profile above the therapeutic threshold, and thus in a potentially widened therapeutic window able to improve HB therapy. This rational engineering of both partners may pave the way for new fusion strategies for the design of engineered biotherapeutics.

Serpins, New Therapeutic Targets for Hemophilia.

Hemostasis is a tightly regulated process characterized by a finely tuned balance between procoagulant and anticoagulant systems. Among inherited hemostatic conditions, hemophilia is one of the most well-known bleeding disorders. Hemophilia A (HA) and B (HB) are due to deficiencies in coagulation factor VIII (FVIII) or FIX, respectively, leading to unwanted bleeding. Until recently, hemophilia treatment has consisted of prophylactic replacement therapy using plasma-derived or recombinant FVIII in cases of HA or FIX in cases of HB. Because FVIII and FIX deficiencies lead to an imbalance between procoagulant and anticoagulant systems, a recent upcoming strategy implies blocking of endogenous anticoagulant proteins to compensate for the procoagulant factor deficit, thus restoring hemostatic equilibrium. Important physiological proteins of the anticoagulant pathways belong to the serpin (serine protease inhibitor) family and, recently, different experimental and clinical studies have demonstrated that targeting natural serpins could decrease bleeding in hemophilia. Here, we aim to review the different, recent studies demonstrating that blocking serpins such as antithrombin, protein Z-dependent protease inhibitor, and protease nexin-1 or modifying a serpin like α1-antitrypsin could rebalance coagulation in hemophilia. Furthermore, we underline the potential therapeutic use of serpins for the treatment of hemophilia.

Pharmacodynamics of eftrenonacog-alfa (rFIX-Fc) in severe hemophilia B patients: A real-life study.

Eftrenonacog-alfa is a recombinant factor IX-Fc fusion protein increasingly prescribed in hemophilia B patients. We aimed to assess its pharmacodynamics (PD) in real-life setting via FIX activity measurement and thrombin generation assay (TGA). Sixty samples from 15 severe hemophilia B treated patients were collected at different time points. FIX activity was measured using product-specific one-stage clotting assay (reference method) and two chromogenic assays (CSA) (Biophen FIX and Rox FIX). TGA was triggered with 1 pM tissue factor. Five parameters were analyzed: lag time (LT), time to peak (TTP), peak height (PH), endogenous thrombin potential (ETP), and velocity. PD models were built to characterize their relationships with FIX activity, using mixed effects models. Mean trough FIX level was estimated at 4.64 (±1.50) IU/dl with a recovery at 0.78 (±0.16) IU/dl per 1 IU/kg injected dose. FIX activity ranged between 1 and 86 IU/dl with 21.5 IU/dl median value. Biophen FIX and Rox FIX allowed reliable measurements except in samples with FIX <20 IU/dl in which values were underestimated (delta >30%). PD models revealed that velocity was the most sensitive TGA parameter to FIX activity followed by PH, ETP, TTP and finally LT. Following FIX activity peak after eftrenonacog-alfa injection, velocity decreased first, followed by PH then ETP. Both CSA failed to accurately measure FIX in severe hemophilia B patients receiving eftrenonacog-alfa throughout the measuring range. TGA could be an additional valuable tool to evaluate hemostasis balance in treated patients.

Continuous infusion factor replacement in haemophilia B during and after cardiac surgery: the better choice?

A 57-year-old man with mild haemophilia B was admitted for coronary artery bypass graft surgery. His factor IX (FIX) activity was 15% on admission. Our goal was to maintain his FIX activity at 80%-100% for post-op days (PODs) 0-3, and at 60%-80% for PODs 4-14. Preoperatively, the patient was given recombinant FIX (rFIX) bolus using the formula:Dosage needed=%(desired FIX level-current level of FIX)×weight (kg)×1.3.This increased his activity to 100%. One IU of rFIX increased FIX activity by 0.8%; the half-life of rFIX is 18-24 hours. The rFIX infusion was started intraoperatively and continued after surgery to maintain target FIX activity. He was discharged on POD 9 on rFIX bolus dosing of 5000 IU every 12 hours for an additional 5 days. Using continuous factor infusion, we managed to decrease the amount rFIX used by >60% while maintaining steady state FIX activity level.

Normal activated partial thromboplastin time in Chinese patients with mild hemophilia B.

OBJECTIVES: Hemophilia B (HB, OMIM: 300746) is one of the most common bleeding disorders with an X-linked recessive inheritance pattern, caused by the deficiency of coagulation factor IX (FIX). FIX is encoded by the F9 gene located on Xq27.1. Diagnosis of HB is primarily suspected by prolonged activated partial thromboplastin time (APTT), decreased FIX activity (FIX:C) or genetic test of the F9 gene. We herein described a Chinese family with patients of mild HB. METHODS: Sanger sequencing of the F9 gene was applied to identify mutation. Coagulation tests were performed. RESULTS: The proband was a 5-year-old boy. He suffered prolonged bleeding after tonsillectomy recently and circumcision last year as well. His grandfather experienced prolonged bleeding after gastric surgery. Both patients showed normal APTT, though they had significantly decreased FIX:C. Sanger sequencing of the F9 gene revealed a novel hemizygous F9 c.639C > A (p.Asn213Lys) missense mutation in both patients. The proband's mother carried heterozygous mutation. This mutation was located in the activation peptide domain of FIX. CONCLUSION: In conclusion, we confirmed that APTT could be normal in mild HB patients. Highly sensitive APTT for mild HB and molecular genetic test could confirm the diagnosis of mild HB.

Carriers of haemophilia: pregnancy, childbirth and postpartum.

Management of haemophilia carrier women during labour and postpartum is yet to be standardized. Pregnancy was accompanied by a marked rise in factor VIII levels compared with only a small rise in factor IX levels. After delivery, a carrier's factor level drops down to prepregnancy levels, which increases the chance of postpartum haemorrhage. Availability of management guideline and care provided in a multidisciplinary approach can help to minimize bleeding complications in carriers of haemophilia and their newborns.

The Progression of Hemophilic Arthropathy: The Role of Biomarkers.

BACKGROUND: Hemophilia A and B are X-linked congenital bleeding disorders characterized by recurrent hemarthroses leading to specific changes in the synovium and cartilage, which finally result in the destruction of the joint: this process is called hemophilic arthropathy (HA). This review highlights the most prominent molecular biomarkers found in the literature to discuss their potential use in the clinical practice to monitor bleeding, to assess the progression of the HA and the effectiveness of treatments. METHODS: A review of the literature was performed on PubMed and Embase, from 3 to 7 August 2020. Study selection and data extraction were achieved independently by two authors and the following inclusion criteria were determined a priori: English language, available full text and articles published in peer-reviewed journal. In addition, further articles were identified by checking the bibliography of relevant articles and searching for the studies cited in all the articles examined. RESULTS: Eligible studies obtained at the end of the search and screen process were seventy-three (73). CONCLUSIONS: Despite the surge of interest in the clinical use of biomarkers, current literature underlines the lack of their standardization and their potential use in the clinical practice preserving the role of physical examination and imaging in early diagnosis.

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

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

Low bone mass and hypovitaminosis D in haemophilia: A single-centre study in patients with severe and moderate haemophilia A and B.

INTRODUCTION: Haemophilia (H) is frequently associated with a multifactorial reduction in bone mineral density (BDM), but little is known about possible differences between HA and HB according to their severity. AIM: To evaluate the association between low bone mineral density (BMD), 25-hydroxyvitamin D [25(OH)D] concentrations and bone turnover markers in patients with HA and HB younger or older than 50 years. METHODS: In 78 patients <50 years and 33 patients >50 years with severe (S) or moderate (M) HA and HB, BMD was measured by dual-energy X-ray absorptiometry at femoral neck (FN) and lumbar spine and then correlated to annual bleeding rate (ABR), World Federation of Haemophilia orthopaedic joint scale (WFH score), 25(OH)D concentrations, parathyroid hormone (PTH), amino-terminal telopeptide of type 1 collagen (NTx), urinary pyridinolines, osteocalcin and bone-specific alkaline phosphatase. RESULTS: Overall, a high prevalence of hypovitaminosis D was diagnosed. In patients <50 years, low FN-BMD was significantly more frequent in HA than in HB, while PTH, pyridinolines, ABR and WFH score were associated with H type and severity. In patients >50 years, similarly low FN-BMD was observed in HA and HB, while ABR and WFH score were associated with H type and severity, being milder in HB. CONCLUSIONS: Low bone mass is a frequent comorbidity in haemophilic patients of all ages, apart from those with MHB. Clinical and laboratory assessments confirm a higher bone impairment and faster bone resorption in HA compared with HB. Looking at H type and severity, MHB seems to have a normal bone metabolism and a less severe disease.

Rituximab for treating inhibitors in people with inherited severe hemophilia.

BACKGROUND: Hemophilia A and B are inherited coagulation disorders characterized by a reduced or absent level of factor VIII or factor IX respectively. The severe form is characterized by a factor level less than 0.01 international units (IU) per milliliter. The development of inhibitors in hemophilia is the main complication of treatment, because the presence of these antibodies, reduces or even nullifies the efficacy of replacement therapy, making it very difficult to control the bleeding. People with inhibitors continue to have significantly higher risks of morbidity and mortality, with considerable treatment costs. Given the wide 'off-label' use of rituximab for treating people with hemophilia and inhibitors, its efficacy and safety need to be evaluated. This is an update of a previously published Cochrane Review. OBJECTIVES: To assess the efficacy and safety of rituximab for treating inhibitors in people with inherited severe hemophilia A or B. SEARCH METHODS: We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group's Coagulopathies Trials Register, complied from electronic database searches and handsearching of journals and conference abstract books. We searched the reference lists of relevant articles and reviews and also searched for ongoing or unpublished studies. We also undertook further searches of other bibliographic databases and trial registries. Date of last search of the Cochrane Cystic Fibrosis and Genetic Disorders Group's Coagulopathies Trials Register: 19 March 2020. SELECTION CRITERIA: Randomized controlled trials and controlled clinical trials investigating the efficacy and safety of rituximab for treating inhibitors in people with hemophilia. DATA COLLECTION AND ANALYSIS: No randomized controlled trials matching the selection criteria were eligible for inclusion. MAIN RESULTS: No randomized controlled trials on rituximab for treating inhibitors in people with hemophilia were identified. AUTHORS' CONCLUSIONS: We were unable to identify any relevant trials on the efficacy and safety of rituximab for treating inhibitors in people with hemophilia. The research evidence available is from case reports and case series. Randomized controlled trials are needed to evaluate the efficacy and safety of rituximab for this condition. However, prior to the publication of any possible future randomized controlled trials, meta-analysis of case reports and case series may provide some evidence.

Is the Detection of Factor IX Inhibitors in Hemophilia B Orphan than Factor VIII Inhibitors in Hemophilia A? A Concise, Systematic Review.

OBJECTIVE: Development of inhibitors in hemophilia A and B comprise significant challenge for patients, hematologists, and health provider systems. It has recommended by the World Federation of Hemophilia (WFH) to check inhibitors every 3-4 months. The incidence of inhibitor in hemophilia B is lower than hemophilia A. Here, it tried to unravel whether the detection of inhibitors in hemophilia B neglected compared to hemophilia A or not? METHODS: A comprehensive review carried out using six international and local medical search engines on published contributions about inhibitors in hemophilia A and B in Iran. RESULTS: From 699 titles, 12 relevant papers were selected. The mean of factor VIII inhibitors in hemophilia A was 14.8%. The mean of factor IX inhibitors in hemophilia B was 6%. The minimum and maximum reported percentages of factor VIII inhibitors were 4% and 19.6%, while the minimum and maximum of reported percentages of factor IX inhibitors were 0% and 11.8%, respectively. The inhibitors in hemophilia A had reported in 6 papers. One paper had covered the inhibitors in hemophilia B. There were five papers on inhibitors in both hemophilia A and B. The comparison between the reported patients showed that 3020 patients with hemophilia A and 314 patients with hemophilia B had studied. CONCLUSION: Consistent with the lower frequency of hemophilia B and the lower development of inhibitors in hemophilia B compared to hemophilia A, it was concluded that hemophilia B had not neglected in Iran. It seems to be rational that each country, check rates of detection of inhibitors in hemophilia B to identify whether it has neglected or not.