Can hemophilia be cured? It depends on the definition.

Over the years, the palette of treatment options for hemophilia has grown extensively, leading to an increased life expectancy and quality of life for people living with hemophilia. Nonetheless, it is frequently emphasized that none of the current treatment modalities provides a "cure." It is therefore hoped that innovative treatments such as gene therapy may bridge this void. However, the precise definition of a "cure" for hemophilia remains unclear. In this review, we show how the concept of cure is currently used in the field of hemophilia. We then relate the discussion on cure to debates surrounding the classification of hemophilia and philosophical debates on the concepts of health and disease.

The genetic analysis of eight families with hemophilia B in Mongolia: Identification of two novel mutation.

BACKGROUND: This study aimed to conduct molecular diagnostics among individuals with hemophilia B (HB) and carriers of hemophilia in Mongolia. METHODS: Eight patients (six severe, two mild) with HB and their 12 female relatives were enrolled from eight families. Sanger sequence was performed for mutation identification. The questionnaire survey was conducted to evaluate carrier symptoms in female relatives. RESULTS: Two families had a history of HB. A total of five different variants (c.223C > T; c.344A > G; c.464G > C; c.187_188del; and c.1314_1314delA) were identified in six patients with severe HB. Of these, two (c.187_188del and c.1314_1314delA) were novel. No variant in the entire F9 was found in two patients with mild HB. Nonsense c.223C > T (p.Arg75*) mutation was detected in two unrelated patients. Carrier testing identified five mothers as carriers, while one younger sister was a non-carrier. The carrier status of six female relatives of the two mild patients remained undetermined. By questionnaire survey, only one of the five genetically identified carriers displayed noticeable symptoms of being a carrier. CONCLUSION: The novel variants c.187_188del and c.1314_1314delA can cause severe hemophilia B. This study did not observe a significant association between symptoms and carrier status in the five carriers.

Factor IX stimulants in preclinical and early phase trials for hemophilia B treatment.

INTRODUCTION: Hemophilia B is a X-linked rare inherited bleeding disorder characterized by coagulation factor IX (FIX) deficiency. Therapy for hemophilia B is aimed at replacing the FIX deficiency by means of several plasma-derived or recombinant FIX products. The recent availability of recombinant FIX concentrates with a prolonged FIX half-life represented a great technological advance, permitting more spaced drug infusions and reducing treatment burden among hemophilia B patients. AREAS COVERED: This review summarizes the main preclinical and phase 1/2 studies investigating the innovative hemostatic products for hemophilia B replacement therapy. EXPERT OPINION: The significant recent technological advantages in the treatment of hemophilia B has led to the development of innovative FIX products aimed at further extending FIX half-life and using increasingly effective and convenient modes of administration. These novel hemostatic agents, currently in the preclinical or early clinical phase of development, carry the potential of improving patients' health status and quality of life. Continuous research is anyway needed to offer such patients a concrete chance of conducting a normal existence, like to non-affected age-matched individuals.

Study on the Mutation of Fâ ¨ Gene in 31 Patients with Type B Hemophilia.

Hemophilia B (HB) is an inherited bleeding disorder caused by defects in the FⅨ gene, leading to severe coagulation dysfunction. This study designed eight pairs of primers covering eight exons of the FⅨ gene and used PCR and DNA sequencing to detect FⅨ gene mutations in 31 HB patients. Sequencing results were compared with normal sequences using Chromas software on Blast to identify mutation sites. Findings revealed the CpG dinucleotide region as a mutation hotspot and the 192nd nucleotide (FⅨ192) as a dinucleotide polymorphism site in the Chinese population. Pathogenic mutations included point mutations, deletions, insertions, and mutations affecting amino acids or splicing sites. For cases with only polymorphic sites, further exon sequencing is needed. This study adds new mutation data to the global HB database, supports research on racial differences in FⅨ gene mutations, and contributes to domestic HB statistics. The results aid in understanding the FⅨ gene's role in coagulation, elucidating HB pathogenesis, and providing a basis for future gene therapy.

Gene therapy for people with hemophilia B: a proposed care delivery model in Italy.

BACKGROUND: Gene therapy is designed to provide people with hemophilia B with a steady and elevated factor (F)IX activity, thereby strengthening protection and relieving the burden of frequent replacement therapy infusions. The European Medicines Agency has approved gene therapy for the severe and moderately severe forms of hemophilia B that uses the FIX-Padua variant (etranacogene dezaparvovec). OBJECTIVES: The aim was to provide a document dedicated to hemophilia B gene therapy and give a comprehensive overview of the topic. METHODS: An Italian group of experts in hemophilia carried out a narrative review of the literature and discussed during a virtual meeting several key aspects of the delivery of this treatment in Italy. The discussion covered the organizational model, the role of the multidisciplinary team, the laboratory surveillance, and the patient's journey, from the follow-up to the identification of safety issues and outcome measures. RESULTS: This article highlights the need to follow the Hub and Spoke organizational model and sheds light on the role of each professional figure within the multidisciplinary teams to favor patient engagement, management, and retention. Moreover, this article stresses the need to perform laboratory tests for patient screening and follow-up and proposes a checklist to help patient identification. Finally, the needs of Italian hemophilia centers have been considered to ensure an efficient implementation of the care delivery model. CONCLUSION: It is crucial to ensure that centers are appropriately organized, equipped, and trained to adequately select patients, deliver the gene therapy, and perform follow-up.

Primary postpartum hemorrhage in women with von Willebrand disease and carriers of hemophilia: a retrospective analysis.

Background: Between 2002 and 2011, the incidence of severe primary postpartum hemorrhage (PPH) in Dutch women with von Willebrand disease (VWD) and hemophilia carriers (HCs) was 8% vs 4.5% in the general population. Objectives: To determine the contemporary incidence of severe primary PPH in women with VWD and HCs. Methods: All women with VWD or HCs who delivered between 2012 and 2017 were selected from all 6 Dutch hemophilia treatment centers. Data on patient and disease characteristics, peripartum hematologic and obstetric management, and outcomes were retrospectively collected. Incidence of severe primary (≥1000 mL of blood loss ≤24 hours after childbirth) and primary (≥500 mL within ≤24 hours after childbirth) PPH was compared with the (1) previous cohort and (2) general Dutch population and between (3) women with VWD and HCs with third-trimester coagulation activity levels <50 international units (IU)/dL vs ≥50 IU/dL and (4) women treated with vs without peripartum hemostatic prophylaxis. Results: Three-hundred forty-eight deliveries (151 VWD, 167 hemophilia A, and 30 hemophilia B carriers) were included. The severe primary PPH incidence was 10% (36/348) and remained stable over time, whereas this incidence has increased in the general population (to 8%), leading to a similar risk (P = .17). Severe primary PPH risk was comparable between women with coagulation activity levels <50 and ≥50 IU/dL (11% [7/66] vs 10% [29/279]; odds ratio, 1.02; 95% CI, 0.43-2.44) and comparable between those with and those without prophylaxis (12% [11/91] vs 10% [25/254]; odds ratio, 1.26; 95% CI, 0.59-2.68). Conclusion: Severe primary PPH in women with VWD and HCs remained stable and is comparable with the increasing prevalence in the general population. More research is needed to find the optimal pregnancy management strategy for safe delivery in VWD and HC.

Navigating the Challenges of Factor X Deficiency: A Case Study.

The clotting pathway involves intrinsic and extrinsic pathways converging into a common pathway. These pathways require activated factors that sequentially convert prothrombin to thrombin, which then converts fibrinogen to fibrin, forming a stable clot. Clotting factor deficiency impairs this cascade leading to excessive bleeding or bruising due to insufficient clot formation. Here, we present the case of a 47-year-old female who initially complained of epigastric pain. By the third day of admission, she experienced four to five episodes of bleeding gums, resulting in a blood loss of approximately 300 mL. The patient exhibited abnormal prothrombin time (PT) and international normalized ratio (INR) values, leading to a diagnosis of Factor X (FX) deficiency upon further evaluation. This case report emphasizes the need to diagnose coagulopathies such as FX deficiency and how early diagnosis will help not only in patient care and management but also in screening family members who may be affected.

The association between unemployment and treatment among adults with hemophilia.

Background: People with hemophilia often experience pain and suffer from comorbidities related to their bleeding disorder. Consequently, unemployment due to disability is prevalent among people with hemophilia. Objectives: To explore associations between unemployment due to disability and treatment while adjusting for known risk factors for unemployment. Methods: Collecting data from 20 hemophilia centers from 15 European countries, the Age-related DeVelopments ANd ComorbiditiEs in hemophilia study recruited 785 participants aged 40 years and over with hemophilia A or B. A comprehensive electronic case report form included items related to patient characteristics, demographic information, past and current treatment regimens, and medical history, including a lifelong history of comorbidities. Baseline data from the Age-related DeVelopments ANd ComorbiditiEs in hemophilia study was analyzed using descriptive statistics and logistic regression models. Results: Employment status was available for 756 of 785 participants aged 40 to 88 years (median, 53 years). We used regression analysis to compare people with hemophilia who were fully employed with those who were unemployed due to disability. This analysis included 424 participants. Using multivariable logistic regression, we found that age (odds ratio [OR], 1.07; P < .01), severe hemophilia (OR, 10.81; P < .01), current smoker (OR, 2.53; P < .01), and psychiatric disorder (OR, 4.18; P = .02) were associated with increased odds of unemployment due to disability. In contrast, prophylactic treatment (OR, 0.44; P = .01) was associated with decreased odds. Conclusion: Our analysis suggests that by maintaining factor levels above a critical threshold (3%-5%), prophylactic treatment for people with hemophilia could help avoid unemployment due to disability. While prophylaxis is more costly and can be burdensome, the benefits to material well-being and quality of life could be substantial.

Successful immunosuppressive drug-free immune tolerance induction in hemophilia B with inhibitor and anaphylaxis to factor IX: A case report.

Recommendations advise factor IX desensitization before immune tolerance induction in severe hemophilia B, supported by immunosuppression. A child with inhibitor and anaphylaxis to factor IX showed successful immunosuppression-free immune tolerance induction using very low and slowly increasing doses of a factor IX extended-half-life product. Immune tolerance to factor IX based on this protocol merits further study.

Clinical data on treatment regimen and use of medication among patients with hemophilia B in Korea.

BACKGROUND: To investigate the clinical treatment status, such as treatment regimen, bleeding events, and drug dose, in patients with hemophilia B in South Korea. METHODS: In this retrospective chart review, data of patients with hemophilia B from eight university hospitals were collected. Demographic and clinical data, treatment data, such as regimen and number of injections, dose of factor IX concentrate, and bleeding data were reviewed. Descriptive analyses were performed with annual data for 2019, 2020, and 2021, as well as the three years consecutively. RESULTS: The medical records of 150 patients with hemophilia B between January 1, 2019, and December 31, 2021, were collected. Among these, 72 (48.0%) were severe, 47 (31.3%) were moderate, and 28 (18.7%) were mild. The results showed approximately two times more patients receiving prophylaxis as those receiving on-demand therapy, with 66.1% of patients receiving prophylaxis in 2019, 64.9% in 2020, and 72.1% in 2021. Annualized bleeding rates were 2.2% (± 3.1) in 2019, 1.8% (± 3.0) in 2020, and 1.8% (± 2.9) in 2021 among patients receiving prophylaxis. For the doses of factor IX concentrate, patients receiving prophylaxis received an average of 41.6 (± 11.9) IU/Kg/Injection in 2019, 45.7 (± 12.9) IU/Kg/Injection in 2020, and 60.1 (± 24.0) IU/Kg/Injection in 2021. CONCLUSIONS: Clinically, prophylaxis is more prevalent than reported. Based on insights gained from current clinical evidence, it is expected that the unmet medical needs of patients can be identified, and physicians can evaluate the status of patients and actively manage hemophilia B using more effective treatment strategies.

Concizumab prophylaxis in persons with hemophilia A or B with inhibitors: patient-reported outcome results from the phase 3 explorer7 study.

Background: Patient-reported outcomes (PROs) reflect patient perceptions of disease and treatment and are important for evaluating new therapies. Objectives: Evaluate the effects of once-daily concizumab prophylaxis on health-related quality of life (HRQoL), treatment burden, and treatment preference in males aged ≥12 years with hemophilia A/B with inhibitors. Methods: Patients enrolled in the multicenter, open-label explorer7 phase 3 study (ClinicalTrials.gov identifier: NCT04083781) were randomized to receive no prophylaxis (arm 1) or concizumab prophylaxis (arm 2) or were nonrandomly allocated to concizumab prophylaxis (arms 3 and 4). The study included questionnaires to assess patients' perception of HRQoL (Haemophilia Quality of Life Questionnaire for Adults), treatment burden (Hemophilia Treatment Experience Measure), and treatment preference (Haemophilia Patient Preference Questionnaire). Results: The estimated treatment difference between patients receiving concizumab prophylaxis vs no prophylaxis at week 24 for Haemophilia Quality of Life Questionnaire for Adults "total score" was -22.6 points (95% CI, -42.5; -2.7), directionally favoring patients receiving concizumab prophylaxis. For Hemophilia Treatment Experience Measure "total score," the estimated treatment difference was -19.9 points (95% CI, -34.3, -5.6) in favor of concizumab vs no prophylaxis. The majority of patients receiving concizumab expressed a preference for concizumab over their previous treatment, the main reasons being "fewer bleeds," "require less time," and "less painful to inject." Across all PROs, there were less responses collected than anticipated, limiting interpretations. Conclusion: PROs collected during the explorer7 study showed improvements in some domains of HRQoL, treatment burden, and patient treatment preference in persons with hemophilia A or B with inhibitors receiving concizumab prophylaxis compared with no prophylaxis.

Real-world usage and effectiveness of recombinant factor VIII/factor IX Fc in hemophilia A/B: final data from the 24-month, prospective, noninterventional PREVENT study in Germany.

Background: Real-world experience with efmoroctocog alfa (a recombinant factor [F]VIII Fc fusion protein [rFVIIIFc]) and eftrenonacog alfa (a recombinant factor IX Fc fusion protein [rFIXFc]) is needed to bridge evidence gaps. Objectives: To describe rFVIIIFc/rFIXFc usage and effectiveness over a 24-month prospective period. Methods: PREVENT (NCT03055611), a noninterventional study across 25 German hemophilia treatment centers, enrolled previously treated persons with hemophilia A and B (all ages/severities) on individualized rFVIIIFc/rFIXFc prophylaxis before/at enrollment. Primary endpoints included annualized bleeding rate (ABR), injection frequency (IF), and factor consumption (FC). Additionally, up to 12 months of retrospective FVIII/FIX data were collected. Physician and patient satisfaction, and safety outcomes were also assessed. Results: Overall, 150 patients received ≥1 rFVIIIFc dose and 47 patients received ≥1 rFIXFc dose, with median prospective follow-up of 20.6 and 21.0 months, respectively. rFVIIIFc/rFIXFc demonstrated low median ABR (0.5/1.7), annualized IF (121.8/52.2 injections/y), and FC (4611.7/2423.9 IU/kg) in line with product labels. Compared with previous FVIII/FIX, there was a 56.0% reduction in ABR for rFVIIIFc (rate ratio, 0.44; 95% CI, 0.31-0.64), with no change for rFIXFc (rate ratio, 0.93; 95% CI, 0.66-1.31); rFVIIIFc/rFIXFc reduced annualized IF (rFVIIIFc, mean difference, -31.7; 95% CI, -40.3 to -23.1; rFIXFc, mean difference, -37.3; 95% CI, -46.9 to -27.8), while FC remained stable (rFVIIIFc, +374.1; 95% CI, +46.8 to +701.3; rFIXFc, +503.9; 95% CI, +95.4 to +912.4). Most physicians and patients were satisfied or highly satisfied with rFVIIIFc/rFIXFc. rFVIIIFc/rFIXFc were well tolerated, with no inhibitor development or treatment-related serious adverse events. Conclusion: Real-world PREVENT data complement phase 3 trials and show that individualized rFVIIIFc/rFIXFc prophylaxis provided stable bleed protection with low IF and maintained FC. Compared with previous FVIII, ABR was considerably reduced with rFVIIIFc, with stable annualized FC. For rFIXFc, bleed protection was maintained vs previous FIX while reducing annualized IF.

Matched cohort study evaluating the hemostatic efficacy of fibrin sealant versus conventional approaches following dental surgery in patients with hemophilia.

Patients with hemophilia frequently require supplementary interventions, either invasive (suturing, gel foam, or cauterization) or non-invasive (fibrin sealant/glue), to attain hemostasis post dental procedures. This study aimed to compare the efficacy of fibrin sealant against traditional methods for achieving hemostasis post dental surgery. The medical records of patients with factor VIII or IX deficiency, or von Willebrand disease, who underwent dental procedures in the Department of Dentistry, Seth GSMC and KEM Hospital, were evaluated for inclusion in this retrospective matched cohort study. Cohort-1 included those treated with a fibrin sealant (Tisseel Lyo) with/without traditional hemostatic measures post-procedure, while cohort-2 (controls) included those in whom no fibrin sealant was used. A total of 128 patients, 64 in each group, were evaluated. There was no statistically significant difference in demographics, disease-related variables, dental complaints, or preoperative treatment given between the groups. However, there was a significant reduction (P < 0.001) in the requirement for secondary procedures for hemostasis (suturing, gel foam application, and/or cauterization) and postoperative requirement for factor replacement (P = 0.003) in the fibrin glue group as compared to the controls. In this study, fibrin sealant demonstrated superior efficacy in mitigating the necessity for active hemostasis control.

Characterization of recombinant factor IX fusion proteins enabling subcutaneous administration.

BACKGROUND: The X-linked bleeding disorder hemophilia B, caused by mutation(s) in the coagulation factor (F)IX gene, leads to partial or total loss of its function, requiring lifelong FIX replacement therapy. Although new recombinant FIX (rIX) therapeutics like albumin fusion proteins (rIX-FP) enable longer plasma half-life and thus less frequent administration, the complexity of intravenous (i.v.) injection remains. OBJECTIVES: The study aimed to characterize rIX-FP variants with anticipated enhanced specific activity, which would leverage rIX-FP's superior pharmacokinetic profile with beneficial characteristics for subcutaneous (s.c.) administration. METHODS: Two rIX-FP variants, R338L ("Padua variant") and R338L/E410K, were characterized in vitro. Pharmacokinetic profiles of FIX antigen and activity levels were evaluated in FIX-deficient mice after i.v. and s.c. administration of these variants (dosing based on antigen levels). The efficacy of the most promising variant was tested after i.v. and s.c. administration (dosing based on activity) in a tail clip bleeding model. A marketed wild-type (WT) rIX-FP product served as the comparator. RESULTS: Both rIX-FP variants showed a 4- to 5-fold increase in specific activity in vitro compared with rIX(WT)-FP, while FXIa-mediated activation was the fastest for rIX(WT)-FP and rIX(R338L)-FP. Compared with rIX(WT)-FP and rIX(R338L/E410K)-FP, rIX(R338L)-FP exhibited higher FIX activity exposure after i.v. and s.c. administration and demonstrated comparable efficacy with rIX(WT)-FP in reducing bleeding time and blood loss in FIX-deficient mice requiring ∼4 times lower protein amount. CONCLUSION: rIX(R338L)-FP was shown to be a promising candidate for s.c. administration, exhibiting increased specific activity combined with higher activity-based exposure and indicating efficacy at a lower protein dose.

An integrated multitool analysis contributes elements to interpreting unclassified factor IX missense variants associated with hemophilia B.

BACKGROUND: Dissection of genotype-phenotype relationships in hemophilia B (HB) is particularly relevant for challenging (mild HB) or for HB-associated but unclassified factor (F)IX missense variants. OBJECTIVE: To contribute elements to interpret unclassified HB-associated FIX missense variants by a multiple-level approach upon identification of a reported, but uncharacterized, FIX missense variant associated with mild HB. METHODS: Molecular modeling of wild-type and V92A FIX variants, expression studies in HEK293 cells with evaluation of protein (ELISA, western blotting) and activity (activated partial thromboplastin time-based/chromogenic assays) levels after recombinant expression, and multiple prediction tools. RESULTS: The F9(NM_000133.4):c.275T>C (p.V92A) variant was found in a mild HB patient (antigen, 45.4 U/dL; coagulant activity, 23.6 IU/dL; specific activity, 0.52). Newly generated molecular models showed alterations in Gla/EGF1-EGF2 domain conformation impacting Ca++ affinity and protein-protein interactions with activated factor XI (FXIa). Multitool analysis indicated a moderate impact on protein structure/function of the valine-to-alanine substitution, in accordance with patient and modeling data. Expression studies on the V92A variant showed a specific activity (0.49 ± 0.07; wild-type, 1.0 ± 0.1) recapitulating that of the natural variant, and pointed toward a moderate activation impairment as the main determinant underlying the p.V92A defect. The validated multitool approach, integrated with evidence-based data, was challenged on a panel (n = 9) of unclassified FIX missense variants, which resulted in inferred protein (secretion/function) outputs and HB severity. CONCLUSION: The rational integration of multitool and multiparameter analyses contributed elements to interpret genotype/phenotype relationships of unclassified FIX missense variants, with implications for diagnosis, management, and treatment of HB patients, and potentially translatable into other human disorders.

Inhibitor development according to concentrate after 50 exposure days in severe hemophilia: data from the European HAemophilia Safety Surveillance (EUHASS).

Background: Patients with hemophilia have a life-long risk of developing neutralizing antibodies (inhibitors) against clotting factor concentrates. After the first 50 exposure days (EDs), ie, in previously treated patients (PTPs), data on inhibitor development are limited. Objectives: To report inhibitor development according to factor (F)VIII or FIX concentrate use in PTPs with severe hemophilia A and B. Methods: Inhibitor development in PTPs was collected since 2008 from 97 centers participating in European HAemophilia Safety Surveillance. Per concentrate, inhibitors were reported quarterly and the number of PTPs treated annually. Incidence rates (IRs)/1000 treatment years with 95% CIs were compared between concentrate types (plasma derived FVIII/FIX, standard half-life recombinant FVIII/FIX, and extended half-life recombinant (EHL-rFVIII/IX) concentrates using IR ratios with CI. Medians and IQRs were calculated for inhibitor characteristics. Results: For severe haemophilia A, inhibitor rate was 66/65,200 treatment years, IR 1.00/1000 years (CI 0.80-1.30), occurring at median 13.5 years (2.7-31.5) and 150 EDs (80-773). IR on plasma-derived pdFVIII (IR, 1.13) and standard half-life recombinant FVIII (IR, 1.12) were similar, whereas IR on EHL-rFVIII was lower at 0.13 (incidence rate ratio, 0.12; 95% CI, <0.01-0.70; P < .01).For severe hemophilia B, inhibitor rate was 5/11,160 treatment years and IR was 0.45/1000 years (95% CI, 0.15-1.04), at median 3.7 years (95% CI, 2.1-42.4) and 260 EDs (95% CI, 130 to >1000). Data were insufficient to compare by type of FIX concentrates. Conclusion: Low inhibitor rates were observed for PTPs with severe hemophilia A and B. Data suggested reduced inhibitor development on EHL-rFVIII, but no significant difference between plasma-derived FVIII and standard half-life recombinant FVIII. FIX inhibitor rates were too low for robust statistical analysis.

Genotype-phenotype analyses of Iranian patients with hemophilia B (Leyden -) and hemophilia B (Leyden +): A single-center study.

BACKGROUND: There is a high prevalence of inherited bleeding disorders in Iran, such as hemophilia A (HA) and hemophilia B (HB). This study aimed to analyze the molecular and clinical profiles of patients with HB. METHODS: A single-center study was conducted among patients with severe HB between March 20, 2000, and June 31, 2023. The polymerase chain reaction (PCR) amplification was used for all of the major regions, such as the promoter, the exons, the adjacent intronic regions, and the untranslated regions of the F9 gene. Finally, Sanger sequencing was performed on the PCR products. RESULTS: A total of 111 HB patients (17 with HB [Leyden +] and 94 with HB [Leyden -]) were enrolled in this study. Among 94 patients with HB (Leyden -), 59 (62.8 %) had missense, 21 (22.3 %) had nonsense, and 8 (8.5 %) had frameshift mutations. Moreover, the most frequent pathogenic variant in HB (Leyden +) was c.-17 A>G in this study. CONCLUSION: The results of this study confirm that HB is caused by a wide range of molecular defects in Iran. Thus, by knowing the genotypes and phenotypes, we would be able to stratify the patients which is important in terms of their management and outcome.

International Society on Thrombosis and Haemostasis clinical practice guideline for treatment of congenital hemophilia A and B based on the Grading of Recommendations Assessment, Development, and Evaluation methodology.

BACKGROUND: Hemophilia is a rare congenital bleeding disorder that results from complete or partial deficiency of blood coagulation factor (F)VIII (hemophilia A) or FIX (hemophilia B) due to pathogenic variants in their coding genes. Hemophilia requires complex management. To date, there is no evidence-based clinical practice guideline on hemophilia treatment based on the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) approach. OBJECTIVES: This evidence-based clinical practice guideline from the International Society on Thrombosis and Haemostasis aims to provide an overview of evidence and support patients, caregivers, hematologists, pediatricians, other clinicians, researchers, and stakeholders in treatment decisions about congenital hemophilia A and B. METHODS: The International Society on Thrombosis and Haemostasis formed a multidisciplinary guideline panel of physicians and patients with global representation, balanced to minimize potential bias from conflicts of interest. The panel prioritized a set of clinical questions and outcomes according to their importance for clinicians and patients. A methodological team supported the guideline development process, including searching for evidence and performing systematic reviews. The GRADE approach was used, including GRADE Evidence to Decision frameworks. The recommendations were subject to public comment. RESULTS: The panel selected 13 questions, of which 11 addressed the treatment of hemophilia A and 2 the treatment of hemophilia B. Specifically, the panel addressed questions on prophylactic and episodic treatment with FVIII concentrates, bypassing agents, and nonfactor therapy (emicizumab) for hemophilia A (with and without inhibitors) as well as immune tolerance induction for hemophilia A. For hemophilia B, the panel addressed questions on prophylactic and episodic treatment of bleeding events with FIX concentrates. Agreement was reached for all 13 recommendations, of which 7 (54%) were based on evidence from randomized clinical trials, 3 (23%) on observational studies, and 3 (23%) on indirect comparisons. CONCLUSION: Strong recommendations were issued for prophylactic over episodic treatment for severe and moderately severe hemophilia A and B. Only conditional recommendations were issued for the remaining questions. Future research should focus on direct treatment comparisons and the treatment of hemophilia B with and without inhibitors. Future updates of this guideline will provide an updated evidence synthesis on the current questions and focus on new FVIII and FIX concentrates, novel nonfactor therapies, and gene therapy for severe and nonsevere hemophilia A and B.

Human umbilical cord mesenchymal stem cell-based gene therapy for hemophilia B using scAAV-DJ/8-LP1-hFIXco transduction.

BACKGROUND: Hemophilia B is an X-linked bleeding disorder caused by a mutation in the gene responsible for encoding coagulation factor IX (FIX). Gene therapy offers promising potential for curing this disease. However, the current method of relatively high dosage of virus injection carries inherent risks. The purpose of this study was to introduce a novel scAAV-DJ/8-LP1-hFIXco vector transduced human umbilical cord blood derived mesenchymal stem cells (HUCMSCs) as an alternative cell-based gene therapy to conventional gene therapy for Hemophilia B. METHODS: The LP1-hFIXco gene structure was designed by us through searching the literature from NCBI and the scAAV-DJ/8-LP1-hFIXco vector was constructed by a commercial company. The HUCMSCs were cultivated in routine approach and transduced with scAAV-DJ/8-LP1-hFIXco vector. The human FIX activation system was employed for detection of hFIXco activity. The RNA and protein expression levels of the hFIXco were evaluated using PCR and western blot techniques. In animal studies, both NSG and F9-KO mice were used for the experiment, in which clotting time was utilized as a parameter for bleeding assessment. The immunohistochemical analysis was used to assess the distribution of HUCMSCs in mouse tissue sections. The safety for tumorigenicity of this cell-based gene therapy was evaluated by pathological observation after hematoxylin-eosin staining. RESULTS: The transduction of HUCMSCs with the scAAV-DJ/8-LP1-hFIXco vector results in consistent and sustainable secretion of human FIXco during 5 months period both in vitro and in mouse model. The secretion level (hFIXco activity: 97.1 ± 2.3% at day 7 to 48.8 ± 4.5% at 5 months) was comparable to that observed following intravenous injection with a high dose of the viral vector (hFIXco activity: 95.2 ± 2.2% to 40.8 ± 4.3%). After a 5-month observation period, no clonal expansions of the transduced cells in tissues were observed in any of the mice studied. CONCLUSIONS: We have discovered a novel and safer HUCMSCs mediated approach potentially effective for gene therapy in hemophilia B.

Identifying hemophilia B carriers: Utility of aPTT, factor IX levels and ratios of factor IX to other Vitamin K dependent factors.

INTRODUCTION: Diagnosing hemophilia B (HB) carrier status is important to manage bleeding in carriers and to prevent bleeding in potential offspring. Without a family history of hemophilia, diagnosing HB carrier status is challenging. Genetic testing is the gold-standard, however it is reserved for individuals with a high suspicion of carrier status. AIMS: To describe the distribution of activated partial thromboplastin time (aPTT) and factor IX coagulant (FIX:C) levels in HB carriers and assess the ratio of FIX:C to other Vitamin K dependent factors (FII:C, FVII:C, FX:C) as an indicator of HB carrier status. METHODS: In this retrospective, single-centre cohort study, subjects were included if they were obligate or genetically proven HB carriers. Distributions of aPTT and FIX:C were described and the relationship between FIX:C levels in carriers and severity of familial HB was analysed. Ratios of FIX:C to FII:C, FVII:C, FX:C were calculated. RESULTS: Seventy-two female HB carriers (median age: 34 years; IQR 24-43) were included. Median aPTT and FIX:C levels were 33.0 s [IQR 30.0-37.0] and 57 IU/dL [IQR 43-74]. Fifteen carriers (21%) had mild HB (FIX:C levels of 10-40 IU/dL). FIX:C levels trended higher in carriers of mild HB versus carriers of moderate/severe HB. In six carriers, the median ratio of FIX:C to other Vitamin K dependent factors was 0.44, with 92% of ratios being ≤ 0.75. CONCLUSION: aPTT and FIX:C levels were unreliable in diagnosing HB carrier status. A low ratio of FIX:C to other Vitamin K dependent factors may be a useful marker of HB carrier status.