Hemophilia B: molecular pathogenesis and mutation analysis

Evaluating the Cost-Effectiveness of Etranacogene Dezaparvovec Gene Therapy for Hemophilia B Treatment in the USA

BACKGROUND

Hemophilia B, a severe genetic disorder, involves substantial treatment costs and frequent interventions. Etranacogene dezaparvovec (EDZ) is a recently approved gene therapy for hemophilia B.

OBJECTIVE

This study evaluates the cost-effectiveness of EDZ compared with conventional factor IX (FIX) prophylaxis.

METHODS

A semi-Markov model simulated a cohort of adult males with severe hemophilia B to assess the economic impact of EDZ versus FIX prophylaxis over a lifetime horizon from a health system perspective in the USA. Inputs derived from clinical trials included therapy durability and transition probabilities based on Pettersson Scores. Scenario analyses incorporated frameworks suggested by the Institute for Clinical and Economic Review for single or short-term transformative therapies.

RESULTS

Base-case analysis showed that at a cost of US$3.5 million, EDZ led to lifetime cost savings of US$11 million and an additional 0.64 quality-adjusted life years (QALYs) compared with FIX. However, FIX has extremely high annual costs. When annual cost offsets attributed to EDZ were capped at US$150,000, EDZ was found to have a threshold price of US$3.1 million at a willingness-to-pay of US$150,000 per QALY.

CONCLUSION

EDZ proved to be a dominant strategy over FIX prophylaxis in the base-case scenario, providing large cost savings and slightly better outcomes. The substantial costs associated with FIX are a primary driver behind these results. The introduction of cost-offset caps significantly affects the value-based price of EDZ. Using caps on cost offsets in considering price can help to balance affordability and value in the health system.

Identification of Novel F9 Gene Variants in 143 Vietnamese Patients with Hemophilia B

Purpose

Vietnam is estimated to have approximately 30,000 hemophilia B (HB) carriers, with hundreds of new cases registered annually. However, comprehensive molecular studies on HB remain limited. Therefore, this study aimed to characterize genetic variants and assess their clinical significance in unrelated Vietnamese patients with HB.

Patients and Methods

This study included a cohort of 143 unrelated HB patients with diagnosed FIX levels. Genetic analysis of the F9 gene was performed using DNA sequencing and other molecular techniques. Variant pathogenicity was classified following ACMG/AMP guidelines, supplemented by computational predictions and clinical data.

Results

A 100% variant detection rate was achieved, identifying 83 unique variants from 143 patients. Single nucleotide variants were predominant, with missense variants accounting for 71.08%. Of the 83 unique variants, 20 novel variants were identified, including six missenses, four nonsenses, four frameshifts, two large deletions, two in-frame deletions, and two splice-site variants. The serine protease domain contained the highest proportion of variants (49.4%). Pathogenicity analysis revealed a predominance of severe phenotypes (72.03%). Among the novel variants, twelve were classified as pathogenic, one as likely pathogenic, and seven as variants of uncertain significance. A noteworthy case was the NM_000133.4:c.-21C>T promoter variant associated with HB Leyden, which demonstrated age-dependent improvements in factor IX levels.

Conclusion

This study expands the mutational spectrum of HB in the Vietnamese population and provide critical insights into genotype-phenotype correlations. The identification of novel variants enhances diagnostic precision and underscores the importance of comprehensive genomic analyses in understanding disease mechanisms.

Hemophilia B Leyden: characteristics and natural history in the International Pediatric Network of Hemophilia Management Registry

BACKGROUND

A unique form of hemophilia B (HB) is HB Leyden. We evaluated the international Pediatric Network on Hemophilia Management Registry (PedNet) database to explore the natural history of HB Leyden, investigate genotype-phenotype associations, and guide clinical decision-making.

OBJECTIVES

To assess the association between genetic variants, endogenous factor (F)IX levels over time, treatment, and bleeding phenotype in children with HB Leyden.

METHODS

Data on genetic variants, FIX levels at diagnosis and over time, bleeding, and treatment details were extracted from the international PedNet in children with hemophilia born since 2000.

RESULTS

Of 457 individuals with HB, 24 showed an HB Leyden genotype. The most frequent F9 variant was c.-35G>A, affecting 14 individuals, followed by c.-35G>C (n = 4), c.-49T>A (n = 2), and c.-52C>T, c.-34A>G, and c.-22delT (n = 1 each). Major clinical differences in bleeding and treatment modality were observed when comparing c.-35G>A with non-c.-35G>A genotypes. For all children with a c.-35G>A genotype, FIX levels increased before the age of 4 years but did not normalize over time, irrespective of initial severity. In children with non-c.-35G>A genotypes, an increase in FIX was less common (4/9) and occurred later.

CONCLUSION

HB Leyden is caused by the variant c.-35G>A in >50% of cases in whom a FIX increase occurs at very young ages, which is associated with low bleeding rates. This contrasts with the phenotype of individuals with HB Leyden due to a non-c.-35G>A variant. Our study may thus help guide clinical decision-making in this rare HB entity.

Dose-intensive therapy (DIT) for infantile Pompe disease: A pilot study

Background

The current standard of care for infantile-onset Pompe disease (IOPD), a severe form of acid α-glucosidase enzyme activity deficiency is: (1) detection by newborn screening, (2) early initiation of intravenous enzyme replacement therapy (ERT) using recombinant human acid alpha-glucosidase (rhGAA), with higher doses of rhGAA increasingly used to improve clinical outcomes, and (3) immune tolerization induction (ITI) using to prevent anti-rhGAA antibody formation, with methotrexate (MTX), rituximab, and IVIG used for patients who are cross-reactive immunologic material negative (CRIM-) and monotherapy with MTX used in patients who are cross-reactive immunologic material positive (CRIM+).

Objectives/methods

A pilot study evaluates a dose-intensive therapy (DIT) using high-dose ERT (40 mg/kg/week) and more frequent exposure to ERT (i.e., 3 times weekly administration) to mitigate anti-rhGAA antibody formation, as an alternative to the standard therapeutic approach for IOPD.

Results

In the first patient, DIT resulted in rapid normalization of the following: (1) bi-ventricular hypertrophy, (2) urine HEX-4, (3) CK, (4) liver transaminases. At 7 years of age, the patient continues the DIT regimen. To date, all pediatric developmental milestones have been met on time, anti-rhGAA antibodies have been negative and the patient is able to attend school and maintain normal activities of daily living.

Conclusions

Over a 7-year period, DIT for CRIM-positive IOPD was well tolerated in the first patient treated. Excellent clinical outcomes were achieved, and anti-rhGAA antibodies levels were consistently undetectable. Assessments of more patients, that includes patients with CRIM-, as well as CRIM+ IOPD, will determine if this approach consistently achieves improved clinical outcomes and immune tolerization.

Development of iPSC-derived FIX-secreting hepatocyte sheet as a novel treatment tool for hemophilia B treatment

BACKGROUND

Hemophilia B is an inherited disorder caused by a mutation in the FIX gene, which results in insufficient blood clotting factor IX (FIX) production from hepatocytes. Currently, there are no treatments for hemophilia B patients. The patients should be continuously administrated with clotting factor concentrates 2-3 times a month to prevent bleeding. Therefore, this study aimed to develop an engineered FIX-secreting hepatocyte sheet that can release FIX for an extended period. Within this study, the engineered FIX-secreting hepatocyte sheet was developed by integrating two core technologies, including a gene editing platform to generate FIX-secreting cells and cell sheet technology to improve cell delivery efficacy.

METHODS

The human FIX gene was inserted into the APOC3 site of iPSCs by CRISPR/Cas9, which secretes the target protein after differentiation into hepatocytes. FIX-secreting hepatocyte sheets were obtained by temperature-responsive polymer grafted cell culture dishes (TRCD). Immunohistochemical and functional tests were performed for hepatocyte-like cells differentiated from FIX KI-iPSCs and wild-type iPSCs (WT-iPSCs). After validating the functional activity and secretion of FIX protein, the engineered hepatocyte-like cell sheets were transplanted to NOD/SCID mice for the in vivo experiments.

RESULTS

The insertion of the human FIX gene into the APOC3 site demonstrated a significant increase in FIX secretion in hepatocyte-like cells differentiated from FIX KI-iPSCs compared with those obtained from WT-iPSCs. Among the iPSCs to hepatocyte differentiation stages, the hepatic endoderm stage was most suitable for seeding the cells on TRCD and generating cell sheets by temperature changes from 37oC to room temperature when the hepatocyte-like cells have reached maturity. The engineered FIX-secreting cell sheets showed intensive expression of the FIX proteins without losing hepatocyte morphology for 20 days. Furthermore, an in vivo study showed that engineered FIX-secreting cell sheets retained their FIX secretion functions for two weeks, whereas single-cell injected traditionally were barely detected in the experimental animals.

CONCLUSIONS

The engineered FIX-secreting cell sheets fabricated from functionally improved iPSCs with practical cell delivery tools could be a promising tool for clinically treating Hemophilia B.

Evaluation of discrepancy between clot-based and chromogenic factor IX coagulation assays in non-severe hemophilia B patients and identification of the causing mutations

BACKGROUND

Hemophilia B, or Christmas disease, is a hemorrhagic inherited disorder. Previous studies have reported measurement discrepancies in factor VIII activity between clot-based and chromogenic assays in approximately one-third of patients with non-severe hemophilia A. However, similar discrepancies in hemophilia B have been less extensively studied. This research compares clot-based and chromogenic assays in 33 patients with non-severe hemophilia B and investigates the mutations associated with these discrepancies.

METHODS

Citrate and EDTA samples were collected from 33 patients with non-severe hemophilia B at Iran's hemophilia comprehensive care center. Clinical information was also gathered. Both clot-based and chromogenic assays were performed on these patients. DNA was extracted from the EDTA samples for those with discrepancies in the test results, and PCR was conducted to sequence their genes to find mutations.

RESULTS

Among 33 plasma samples from patients with non-severe hemophilia B, 7 showed a measurement discrepancy according to the definition of ISTH (<0.5, >2.0, or an absolute difference >10), which includes both reverse and classic types of discrepancies. In this study, mutations that previously did not show contradictory results now exhibit discrepancies. A difference in classification was observed in 21 % of the patients.

CONCLUSIONS

The findings indicate that the impact of specific mutations varies depending on the assay conditions. In addition to mutations, other factors also play a role in this discrepancy. Both types of assays are essential for the accurate diagnosis and classification of hemophilia B.

Multiplex, multimodal mapping of variant effects in secreted proteins

Despite widespread advances in DNA sequencing, the functional consequences of most genetic variants remain poorly understood. Multiplexed Assays of Variant Effect (MAVEs) can measure the function of variants at scale, and are beginning to address this problem. However, MAVEs cannot readily be applied to the ~10% of human genes encoding secreted proteins. We developed a flexible, scalable human cell surface display method, Multiplexed Surface Tethering of Extracellular Proteins (MultiSTEP), to measure secreted protein variant effects. We used MultiSTEP to study the consequences of missense variation in coagulation factor IX (FIX), a serine protease where genetic variation can cause hemophilia B. We combined MultiSTEP with a panel of antibodies to detect FIX secretion and post-translational modification, measuring a total of 44,816 effects for 436 synonymous variants and 8,528 of the 8,759 possible missense variants. 49.6% of possible F9 missense variants impacted secretion, post-translational modification, or both. We also identified functional constraints on secretion within the signal peptide and for nearly all variants that caused gain or loss of cysteine. Secretion scores correlated strongly with FIX levels in hemophilia B and revealed that loss of secretion variants are particularly likely to cause severe disease. Integration of the secretion and post-translational modification scores enabled reclassification of 63.1% of F9 variants of uncertain significance in the My Life, Our Future hemophilia genotyping project. Lastly, we showed that MultiSTEP can be applied to a wide variety of secreted proteins. Thus, MultiSTEP is a multiplexed, multimodal, and generalizable method for systematically assessing variant effects in secreted proteins at scale.

Clinical validation and application of targeted long-range polymerase chain reaction and long-read sequencing-based analysis for hemophilia: experience from a hemophilia treatment center in China

BACKGROUND

Targeted long-read sequencing (LRS) is expected to comprehensively analyze diverse complex variants in hemophilia A (HA) and hemophilia B (HB) caused by the F8 and F9 genes, respectively. However, its clinical applicability still requires extensive validation.

OBJECTIVES

To evaluate the clinical applicability of targeted LRS-based analysis compared with routine polymerase chain reaction (PCR)-based methods.

METHODS

Gene variants of retrieved subjects were retrospectively and prospectively analyzed. Whole-genome sequencing was performed to further analyze undiagnosed cases. Breakpoints of novel genomic rearrangements were mapped and validated using long-distance PCR and long-range PCR combined with sequencing.

RESULTS

In total, 122 subjects were retrieved. In retrospective analysis of the 90 HA cases, HA-LRS assay showed consistent results in 84 cases compared with routine methods and characterized 6 large deletions with their exact breakpoints confirmed by further validation in 6 cases (routine methods only presented failure in amplifying the involved exons). In prospective analysis of the 21 HA subjects, 20 variants of F8 were identified in 20 cases. For the remaining HA patient, no duplication/deletion or single-nucleotide variant (SNV)/insertion and deletion (InDel) was found, but a potential recombination involving exons 14 and 21 of F8 was observed by LRS. Whole-genome sequencing analysis and further verification defined a 30 478 base pairs (bp) tandem repeat involving exons 14 to 21 of F8. Among the 11 HB patients, HB-LRS analysis detected 11 SNVs/InDels in F9, consistent with routine methods.

CONCLUSION

Targeted LRS-based analysis was efficient and comprehensive in identifying SNVs/InDels and genomic rearrangements of hemophilia genes, especially when we first expanded the panel to include F9. However, further investigation for complex gross rearrangement is still essential.

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.

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.

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.

Current developments of gene therapy in human diseases

Gene therapy has witnessed substantial advancements in recent years, becoming a constructive tactic for treating various human diseases. This review presents a comprehensive overview of these developments, with a focus on their diverse applications in different disease contexts. It explores the evolution of gene delivery systems, encompassing viral (like adeno-associated virus; AAV) and nonviral approaches, and evaluates their inherent strengths and limitations. Moreover, the review delves into the progress made in targeting specific tissues and cell types, spanning the eye, liver, muscles, and central nervous system, among others, using these gene technologies. This targeted approach is crucial in addressing a broad spectrum of genetic disorders, such as inherited lysosomal storage diseases, neurodegenerative disorders, and cardiovascular diseases. Recent clinical trials and successful outcomes in gene therapy, particularly those involving AAV and the clustered regularly interspaced short palindromic repeats (CRISPR)-CRISPR-associated proteins, are highlighted, illuminating the transformative potentials of this approach in disease treatment. The review summarizes the current status of gene therapy, its prospects, and its capacity to significantly ameliorate patient outcomes and quality of life. By offering comprehensive analysis, this review provides invaluable insights for researchers, clinicians, and stakeholders, enriching the ongoing discourse on the trajectory of disease treatment.

Nucleic Acid Delivery Nanotechnologies for In Vivo Cell Programming

In medicine, it is desirable for clinicians to be able to restore function and imbue novel function into selected cells for therapy and disease prevention. Cells damaged by disease, injury, or aging could be programmed to restore normal or lost functions, such as retinal cells in inherited blindness and neuronal cells in Alzheimer's disease. Cells could also be genetically programmed with novel functions such as immune cells expressing synthetic chimeric antigen receptors for immunotherapy. Furthermore, knockdown or modification of risk factor proteins can mitigate disease development. Currently, nucleic acids are emerging as a versatile and potent therapeutic modality for achieving this cellular programming. In this review, we highlight the latest developments in nanobiomaterials-based nucleic acid therapeutics for cellular programming from a biomaterial design and delivery perspective and how to overcome barriers to their clinical translation to benefit patients.

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.

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.

Genetic variant detection in a South African haemophilia B population

BACKGROUND

Haemophilia B is characterised by a deficiency of factor IX (FIX) protein due to genetic variants in the FIX gene (F9). Genetic testing may have a vital role in effectively managing haemophilia B. However, in many developing countries, comprehensive genetic variant detection is unavailable. This study aimed to address the lack of genetic data in our country by conducting genetic variant detection on people affected by haemophilia B in our region.

METHODS

Twenty-one participants were screened with a direct Sanger sequencing method to identify variants in the F9 gene. The identified variants were then compared to previously published variants and/or to a reference database.

RESULTS AND DISCUSSION

A total of ten F9 genetic changes were detected, with five of them being novel. These identified variants were distributed across different domains of the FIX protein. Only one participant had a history of inhibitor formation against FIX replacement therapy. Notably, this participant had two distinct genetic changes present adjacent to each other. Thus, we hypothesise that the presence of multiple variants within the same functional region of the gene may increase the risk for inhibitor development.

CONCLUSION

The discovery of novel pathogenic variations in the F9 gene highlights the importance of genetic analysis in specific geographical regions. The possible link between a complex variant and inhibitor formation illustrates the potential role that genetic screening has as a pre-treatment tool in predicting treatment reactions and outcomes.

Pleiotropic effects of different exonic nucleotide changes at the same position contribute to hemophilia B phenotypic variation

BACKGROUND

The disease-causing effects of genetic variations often depend on their location within a gene. Exonic changes generally lead to alterations in protein production, secretion, activity, or clearance. However, owing to the overlap between proteins and splicing codes, missense variants can also affect messenger RNA splicing, thus adding a layer of complexity and influencing disease phenotypes.

OBJECTIVES

To extensively characterize a panel of 13 exonic variants in the F9 gene occurring at 6 different factor IX positions and associated with varying severities of hemophilia B (HB).

METHODS

Computational predictions, splicing analysis, and recombinant factor IX assays were exploited to characterize F9 variants.

RESULTS

We demonstrated that 5 (38%) of 13 selected F9 exonic variants have pleiotropic effects. Although bioinformatic approaches accurately classified effects, extensive experimental assays were required to elucidate and deepen the molecular mechanisms underlying the pleiotropic effects. Importantly, their characterization was instrumental in developing tailored RNA therapeutics based on engineered U7 small nuclear RNA to mask cryptic splice sites and compensatory U1 small nuclear RNA to enhance exon definition.

CONCLUSION

Overall, albeit a multitool bioinformatic approach suggested the molecular effects of multiple HB variants, the deep investigation of molecular mechanisms revealed insights into the HB phenotype-genotype relationship, enabling accurate classification of HB variants. Importantly, knowledge of molecular mechanisms allowed the development of tailored RNA therapeutics, which can also be translated to other genetic diseases.

Clinical Analysis and Mental Health Survey of Hemophilia Carriers: a Cross-sectional Study

OBJECTIVE

Hemophilia carriers (HCs), who are heterozygous for mutations in the clotting factor VIII/clotting factor IX gene (F8 or F9), may have a wide range of clotting factor levels, from very low, similar to afflicted males, to the upper limit of normal, and may experience mental health issues. The purpose of this study was to provide genetic information on mothers of hemophilia patients and to understand the clotting factor activity and phenotype of HCs. Additionally, we aimed to investigate the mental health status of HCs in China.

METHODS

A total of 127 hemophilia mothers, including 93 hemophilia A (HA) mothers and 34 hemophilia B (HB) mothers, were enrolled in this study. Long distance PCR, multiplex PCR, and Sanger sequencing were used to analyze mutations in F8 or F9. Coagulation factor activity was detected by a one-stage clotting assay. The Symptom Checklist 90 (SCL-90, China/Mandarin version) was given to HCs at the same time to assess their mental health.

RESULTS

A total of 90.6% of hemophilia mothers were diagnosed genetically as carriers, with inversion in intron 22 and missense mutations being the most common mutation types in HA and HB carriers, respectively. The median clotting factor level in carriers was 0.74 IU/mL (ranging from 0.09 to 1.74 IU/mL) compared with 1.49 IU/mL (ranging from 0.93 to 1.89 IU/mL) in noncarriers, of which 14.3% of HCs had clotting factor levels of 0.40 IU/mL or below. A total of 53.8% (7/13) of HA carriers with low clotting factor levels (less than 0.50 IU/mL) had a history of bleeding, while none of the HB carriers displayed a bleeding phenotype. The total mean score and the global severity index of the SCL-90 for surveyed HCs were 171.00 (±60.37) and 1.78 (±0.59), respectively. A total of 67.7% of the respondents had psychological symptoms, with obsessive-compulsive disorder being the most prevalent and severe. The pooled estimates of all nine factors were significantly higher than those in the general population (P<0.05).

CONCLUSIONS

The detection rate of gene mutations in hemophilia mothers was 90.6%, with a median clotting factor level of 0.74 IU/mL, and 14.3% of HCs had a clotting factor level of 0.40 IU/mL or below. A history of bleeding was present in 41.2% of HCs with low clotting factor levels (less than 0.50 IU/mL). Additionally, given the fragile mental health status of HCs in China, it is critical to develop efficient strategies to improve psychological well-being.

Emicizumab as a Promising Form of Therapy for Type A Hemophilia - A Review of Current Knowledge from Clinical Trials

Hemophilia is a plasma bleeding disorder characterized by a deficiency of certain blood clotting factors. The most common forms of this disease, i.e., type A and type B, affect approximately 400,000 people worldwide. Without appropriate treatment ensuring the proper coagulation cascade, this disease may lead to serious disability. Minimizing patient discomfort is possible via replacement therapy, consisting of the substitution of a missing coagulation factor via intravenous administration. Frequent medication and the risk related to factor inhibitors are significant disadvantages, necessitating the improvement of current therapies or the development of novel ones. This review examines the humanized bispecific antibody Emicizumab which ensures hemostasis by mimicking the action of the coagulation factor VIII, a deficiency of which causes type A hemophilia. The paper outlines the topic and then summarizes available clinical trials on Emicizumab in type A hemophilia. Several interventional clinical trials have found Emicizumab to be effective in decreasing bleeding episodes and raising patient satisfaction among various hemophilia A populations. Current Emicizumab-related trials are forecast to be completed between 2024 and 2030, and in addition to congenital hemophilia A, the trials cover acquired hemophilia A and patients playing sports. Providing a more comprehensive understanding of Emicizumab may revolutionize the management of hemophilia type A and improve quality of life. Conclusively, Emicizumab is a gentler therapy owing to subcutaneous delivery and fewer injections, which reduces injection-site reactions and makes therapy less burdensome, ultimately decreasing hospital visits and indirect costs.

Hemophilia Healing with AAV: Navigating the Frontier of Gene Therapy

Gene therapy for hemophilia has advanced tremendously after thirty years of continual study and development. Advancements in medical science have facilitated attaining normal levels of Factor VIII (FVIII) or Factor IX (FIX) in individuals with haemophilia, thereby offering the potential for their complete recovery. Despite the notable advancements in various countries, there is significant scope for further enhancement in haemophilia gene therapy. Adeno-associated virus (AAV) currently serves as the primary vehicle for gene therapy in clinical trials targeting haemophilia. Subsequent investigations will prioritize enhancing viral capsid structures, transgene compositions, and promoters to achieve heightened transduction efficacy, diminished immunogenicity, and more predictable therapeutic results. The present study indicates that whereas animal models have transduction efficiency that is over 100% high, human hepatocytes are unable to express clotting factors and transduction efficiency to comparable levels. According to the current study, achieving high transduction efficiency and high levels of clotting factor expression in human hepatocytes is still insufficient. It is also crucial to reduce the risk of cellular stress caused by protein overload. Despite encountering various hurdles, the field of haemophilia gene therapy holds promise for the future. As technology continues to advance and mature, it is anticipated that a personalized therapeutic approach will be developed to cure haemophilia effectively.

Treatment of congenital coagulopathies, from biologic to biotechnological drugs: The relevance of gene editing (CRISPR/Cas)

Congenital coagulopathies have, throughout the history of medicine, been a focus of scientific study and of great interest as they constitute an alteration of one of the most important and conserved pathways of evolution. The first therapeutic strategies developed to address them were aimed at restoring the blood components lost during hemorrhage by administering whole blood or plasma. Later on, the use of cryoprecipitates was a significant breakthrough as it made it possible to decrease the volumes of blood infused. In the 1970' and 80', clotting factor concentrates became the treatment and, from the 1990's to the present day, recombinant factors -with increasingly longer half-lives- have taken over as the treatment of choice for certain coagulopathies in a seamless yet momentous transition from biological to biotechnological drugs. The beginning of this century, however, saw the emergence of new advanced (gene and cell) treatments, which are currently transforming the therapeutic landscape. The possibility to use cells and viruses as well as specific or bispecific antibodies as medicines is likely to spark a revolution in the world of pharmacology where therapies will be individualized and have long-term effects. Specifically, attention is nowadays focused on the development of gene editing strategies, chiefly those based on CRISPR/Cas technology. Rare coagulopathies such as hemophilia A and B, or even ultra-rare ones such as factor V deficiency, could be among those deriving the greatest benefit from these new developments.

Haemophilia B in Algeria: Realities and therapeutic perspectives

INTRODUCTION

Haemophilia B is a debilitating hereditary coagulation disorder characterized by prolonged or spontaneous episodes of bleeding caused by a deficiency of endogenous factor IX. In Algeria, even though many studies are being carried out to evaluate the prevalence and management of haemophilia B, there is a paucity of locally published literature that can be used to understand the most recent information on the disease's epidemiology, diagnostic techniques and treatment options.

AIMS

The aim of this manuscript is to raise awareness among patients and family clinicians about current practices, recent developments and unmet needs related to haemophilia B in Algeria.

METHODS

A comprehensive literature search was conducted through online scientific databases to review publications regarding haemophilia B in Algeria. Exclusions of the review include case studies, interregional comparisons, abstract-only papers and studies outside the range of 2012-2022.

RESULTS

The findings discussed relate to the epidemiology of haemophilia B in Algeria, the clinical diagnostic process, disease symptoms, the benefits of molecular and genetic testing, advancements in prophylactic care, as well as unmet needs hindering the progression of optimal haemophilia B management.

CONCLUSION

These findings are crucial to encourage the maintenance of national registries with updated epidemiological data, facilitate early and timely detection of disease symptoms, improve the provision of diagnostic facilities and enhance the overall treatment landscape for better patient outcomes.

Monitoring prothrombin activation in plasma through loss of Förster resonance energy transfer

BACKGROUND

Current assays that monitor thrombin generation in plasma rely on fluorogenic substrates to follow the kinetics of zymogen activation, which may be complicated by substrate cleavage from other proteases. In addition, these assays depend on activation following cleavage at the prothrombin R320 site and fail to report the cleavage at the alternative R271 site, leading to the shedding of the auxiliary Gla and kringle domains of prothrombin.

OBJECTIVES

To develop a plasma assay that directly monitors prothrombin activation independent of fluorogenic substrate hydrolysis.

METHODS

Cleavage at the R271 site of prothrombin is monitored through loss of Förster resonance energy transfer in plasma coagulated along the extrinsic or intrinsic pathway.

RESULTS

The availability of factor (F)V in plasma strongly influences the rate of prothrombin activation. The rate of thrombin formation is equally perturbed in FV or prothrombin-depleted plasma, implicating that the thrombin-catalyzed feedback reactions that amplify the coagulation response play an important role in generating sufficient amounts of FVa required for the assembly of prothrombinase. Congenital deficiencies in FVIII and FIX significantly slow down cleavage at R271 in plasma coagulated along the extrinsic and intrinsic pathways. Prothrombin activation in FXI-deficient plasma is only perturbed when coagulation is triggered along the intrinsic pathway.

CONCLUSION

The Förster resonance energy transfer assay enables direct monitoring of prothrombin activation through cleavage at R271 without the need for fluorogenic substrates. The assay is sensitive enough to assess how deficiencies in coagulation factors affect thrombin formation.

Gene Therapy Approaches for the Treatment of Hemophilia B

In contrast to the standard enzyme-replacement therapy, administered from once per 7-14 days to 2-3 times a week in patients with severe hemophilia B, as a result of a single injection, gene therapy can restore F9 gene expression and maintain it for a prolonged time. In clinical research, the approach of delivering a functional copy of a gene using adeno-associated viral (AAV) vectors is widely used. The scientific community is actively researching possible modifications to improve delivery efficiency and expression. In preclinical studies, the possibility of genome editing using CRISPR/Cas9 technology for the treatment of hemophilia B is also being actively studied.

Structural and functional exploration of three newly identified coagulation factor IX mutations in Chinese hemophilia B patients

AIM

To structurally and functionally characterize three newly identified F9 missense mutations, C268Y, I316F, and G413V, in Chinese hemophilia B patients.

METHODS

FIX mutants were expressed in vitro by transient transfection of Chinese hamster ovary (CHO) cells. One-stage activated partial thromboplastin time (APTT) based assay and enzyme-linked immunosorbent assay (ELISA) were used to measure the coagulation activity and antigen level of FIX in conditioned medium. Western blot analysis was also used to evaluate interference of the mutations with synthesis and secretion of FIX. A structural model of the FIX G413V mutant was constructed and structural disturbance caused by the mutation was determined by molecular dynamics simulations.

RESULTS

Both C268Y and I316F impaired expression of FIX. However, the I316F mutant degraded quickly, whereas the C268Y mutant mostly accumulated intracellularly. The G413V mutant could be synthesized and secreted normally, but procoagulant activity was almost completely lost. This loss is likely mostly due to the impact on the catalytic residue cS195.

CONCLUSION

The three FIX mutations identified in Chinese hemophilia B patients either impaired the expression of FIX, as was seen with the I316F and C268Y mutants, or impaired the function of FIX, as was seen with the G413V mutant.

Molecular pathogenesis of a novel Met394Thr variant causing hemophilia B

BACKGROUND

Hemophilia B (HB), a rare bleeding disorder, shows X-linked recessive inheritance and is caused by heterogeneous variants in the FIX gene (F9) encoding coagulation factor IX (FIX). This study aimed to investigate the molecular pathogenesis of a novel Met394Thr variant causing HB.

METHODS

We used Sanger sequencing to analyze F9 sequence variants in members of a Chinese family with moderate HB. Subsequently, we performed in vitro experiments on the identified novel FIX-Met394Thr variant. In addition, we performed bioinformatics analysis of the novel variant.

RESULTS

We identified a novel missense variant (c.1181T>C, p.Met394Thr) in a Chinese family with moderate HB in the proband. The proband's mother and grandmother were carriers for the variant. The identified FIX-Met394Thr variant did not affect the transcription of F9 and the synthesis and secretion of FIX protein. The variant may, therefore, affect the physiological function of FIX protein by disrupting its spatial conformation. In addition, another variant (c.88+75A>G) in intron 1 of F9 was identified in the grandmother, which may also affect FIX protein function.

CONCLUSION

We identified FIX-Met394Thr as a novel causative variant of HB. Further understanding of the molecular pathogenesis underlying FIX deficiency may guide novel strategies for precision HB therapy.

Accessibility and visibility of genetic testing for haemophilia across Europe: Where do we stand?

INTRODUCTION

Haemophilia is characterized by bleeding complications resulting from clotting factor VIII (FVIII) or IX (FIX) deficiency. Identifying the causal pathogenic genetic variant denotes a vital aspect of haemophilia management.

AIM

This study evaluated the accessibility and performances of genetic testing for haemophilia across Europe. The types of genetic analyses, techniques used, turn-around time (TAT) and costs were collected and analysed, as were data updating and quality control.

METHODS

Reported data were retrieved from open access resources, including international databases, Google, laboratory websites, PubMed and government organizations.

RESULTS

Overall, 51 genetic laboratories across 15 European countries providing recently updated molecular haemophilia testing were identified. Gene sequencing for small variants of both F8 and F9 genes was provided in most surveyed laboratories. Almost two-thirds of them offer analysis for inversions using a polymerase chain reaction (PCR) method and detection of copy number variation (CNV) using multiplex ligation-dependent probe amplification (MLPA). Cost and TAT were found to vary considerably. In total, 74% of laboratories exhibited a last modified date or change history. The same percentage of laboratories was in possession of an ISO 15189 standard accreditation, whereas only few of them recently performed external quality assessment schemes (EQA) for haemophilia.

CONCLUSION

Despite several initiatives to improve access to genetic testing for haemophilia, such access must still be improved. Our study similarly revealed the large heterogeneity of the variants tested, techniques employed, TAT, cost and quality among the surveyed laboratories.

KGML-xDTD: a knowledge graph-based machine learning framework for drug treatment prediction and mechanism description

BACKGROUND

Computational drug repurposing is a cost- and time-efficient approach that aims to identify new therapeutic targets or diseases (indications) of existing drugs/compounds. It is especially critical for emerging and/or orphan diseases due to its cheaper investment and shorter research cycle compared with traditional wet-lab drug discovery approaches. However, the underlying mechanisms of action (MOAs) between repurposed drugs and their target diseases remain largely unknown, which is still a main obstacle for computational drug repurposing methods to be widely adopted in clinical settings.

RESULTS

In this work, we propose KGML-xDTD: a Knowledge Graph-based Machine Learning framework for explainably predicting Drugs Treating Diseases. It is a 2-module framework that not only predicts the treatment probabilities between drugs/compounds and diseases but also biologically explains them via knowledge graph (KG) path-based, testable MOAs. We leverage knowledge-and-publication-based information to extract biologically meaningful "demonstration paths" as the intermediate guidance in the Graph-based Reinforcement Learning (GRL) path-finding process. Comprehensive experiments and case study analyses show that the proposed framework can achieve state-of-the-art performance in both predictions of drug repurposing and recapitulation of human-curated drug MOA paths.

CONCLUSIONS

KGML-xDTD is the first model framework that can offer KG path explanations for drug repurposing predictions by leveraging the combination of prediction outcomes and existing biological knowledge and publications. We believe it can effectively reduce "black-box" concerns and increase prediction confidence for drug repurposing based on predicted path-based explanations and further accelerate the process of drug discovery for emerging diseases.

Whole F9 gene sequencing identified deep intronic variations in genetically unresolved hemophilia B patients

BACKGROUND

The disease-causative variant remains unidentified in approximately 0.5% to 2% of hemophilia B patients using conventional genetic investigations, and F9 deep intronic variations could be responsible for these phenotypes.

OBJECTIVES

This study aimed to characterize deep intronic variants in hemophilia B patients for whom genetic investigations failed.

METHODS

We performed whole F9 sequencing in 17 genetically unsolved hemophilia B patients. The pathogenic impact of the candidate variants identified was studied using both in silico analysis (MaxEntScan and spliceAI) and minigene assay.

RESULTS

In total, 9 candidate variants were identified in 15 patients; 7 were deep intronic substitutions and 2 corresponded to insertions of mobile elements. The most frequent variants found were c.278-1806A>C and the association of c.278-1244A>G and c.392-864T>G, identified in 4 and 6 unrelated individuals, respectively. In silico analysis predicted splicing impact for 4 substitutions (c.278-1806A>C, c.392-864T>G, c.724-2385G>T, c.723+4297T>A). Minigene assay showed a deleterious splicing impact for these 4 substitutions and also for the c.278-1786_278-1785insLINE. In the end, 5 variants were classified as likely pathogenic using the American College of Medical Genetics and Genomics guidelines, and 4 as of unknown significance. Thus, the hemophilia B-causing variant was identified in 13/17 (76%) families.

CONCLUSION

We elucidated the causing defect in three-quarters of the families included in this study, and we reported new F9 deep intronic variants that can cause hemophilia B.

Low-dose AAV-CRISPR-mediated liver-specific knock-in restored hemostasis in neonatal hemophilia B mice with subtle antibody response

AAV-delivered CRISPR/Cas9 (AAV-CRISPR) has shown promising potentials in preclinical models to efficiently insert therapeutic gene sequences in somatic tissues. However, the AAV input doses required were prohibitively high and posed serious risk of toxicity. Here, we performed AAV-CRISPR mediated homology-independent knock-in at a new target site in mAlb 3'UTR and demonstrated that single dose of AAVs enabled long-term integration and expression of hF9 transgene in both adult and neonatal hemophilia B mice (mF9 -/-), yielding high levels of circulating human Factor IX (hFIX) and stable hemostasis restoration during entire 48-week observation period. Furthermore, we achieved hemostasis correction with a significantly lower AAV dose (2 × 10⁹ vg/neonate and 1 × 10¹⁰ vg/adult mouse) through liver-specific gene knock-in using hyperactive hF9^R338L variant. The plasma antibodies against Cas9 and AAV in the neonatal mice receiving low-dose AAV-CRISPR were negligible, which lent support to the development of AAV-CRISPR mediated somatic knock-in for treating inherited diseases.

A Case of Acquired Hemophilia A and Congenital Hemophilia B

Congenital hemophilia B is a rare, inherited X-linked bleeding disorder caused by a deficiency of factor IX (FIX). Acquired hemophilia A is a rare, acquired bleeding disorder which presents as new onset bleeding in older adults due to the development of autoantibodies against factor VIII (FVIII). This report describes the management of a patient with congenital hemophilia B and acquired hemophilia A. We highlight the limitations in maintaining FVIII levels using factor replacement alone and the need for escalating treatment such as rituximab and prednisone in patients with acquired hemophilia A. This case demonstrates the importance of continuing to pursue alternative diagnoses when existing ones do not explain the full clinical picture and laboratory data is inconclusive.

Investigation of the Bleeding Tendency in Sudanese Female Carriers of Hemophilia B

Background. Hemophilia (HB) is an X-linked, recessive bleeding disorder characterized by the deficiency or absence of the coagulation factor IX. Usually, females are carriers of the trait, while males are affected. FIX deficiency leads to uncontrollable bleeding events, and the severity is dependent on the levels of the clotting factor. The objective of this research was to measure the prevalence of bleeding tendency in Sudanese carriers of HB. Materials and Methods. In this cross-sectional study, 88 Sudanese carriers of HB participated. The activated partial thromboplastin time test (APTT) and FIX test were performed for each carrier. The frequencies of DNA polymorphism and FIX-linked restriction fragments BamHI, HhaI, and MnII were also assessed. The study was conducted in Khartoum, Sudan, during the period from 2015 to 2017. Results. The study showed that 55 (62.5%) HB carriers were from the Laban village in the White Nile State, and all of them were members of the Shinkheb tribe. The mean age of the study population was 26.3 years. Among the carriers, 57 (64.7%) had abnormal coagulation profiles. The mean value of the APTT level among carriers was significantly increased ( $P$ value: 0.000), while the mean concentration of the FIX levels among the carriers was significantly decreased ( $P$ value: 0.000). The study also showed a negative correlation between PTT and F assay with $P$ value of 0.000 and $R$ value of 0.578. Conclusion. The APTT is high in most carriers and the FIX assay level is low in most carriers. Most carriers had no symptoms and were not bleeding. The Shinkheb tribe is the most ethnic tribe carrying HB (62.5%). HhaII is more informative for carrier detection than others, but it is of significant value if both (MnII and HhaII) were performed in parallel. In Sudanese, BamHI was informative but MnII and HhaII were best in the mutation detection and for prenatal diagnosis.

SAXS analysis of the intrinsic tenase complex bound to a lipid nanodisc highlights intermolecular contacts between factors VIIIa/IXa

The intrinsic tenase (Xase) complex, formed by factors (f) VIIIa and fIXa, forms on activated platelet surfaces and catalyzes the activation of factor X to Xa, stimulating thrombin production in the blood coagulation cascade. The structural organization of the membrane-bound Xase complex remains largely unknown, hindering our understanding of the structural underpinnings that guide Xase complex assembly. Here, we aimed to characterize the Xase complex bound to a lipid nanodisc with biolayer interferometry (BLI), Michaelis-Menten kinetics, and small-angle X-ray scattering (SAXS). Using immobilized lipid nanodiscs, we measured binding rates and nanomolar affinities for fVIIIa, fIXa, and the Xase complex. Enzyme kinetic measurements demonstrated the assembly of an active enzyme complex in the presence of lipid nanodiscs. An ab initio molecular envelope of the nanodisc-bound Xase complex allowed us to computationally model fVIIIa and fIXa docked onto a flexible lipid membrane and identify protein-protein interactions. Our results highlight multiple points of contact between fVIIIa and fIXa, including a novel interaction with fIXa at the fVIIIa A1-A3 domain interface. Lastly, we identified hemophilia A/B-related mutations with varying severities at the fVIIIa/fIXa interface that may regulate Xase complex assembly. Together, our results support the use of SAXS as an emergent tool to investigate the membrane-bound Xase complex and illustrate how mutations at the fVIIIa/fIXa dimer interface may disrupt or stabilize the activated enzyme complex.

The Molecular Basis of FIX Deficiency in Hemophilia B

Coagulation factor IX (FIX) is a vitamin K dependent protein and its deficiency causes hemophilia B, an X-linked recessive bleeding disorder. More than 1000 mutations in the F9 gene have been identified in hemophilia B patients. Here, we systematically summarize the structural and functional characteristics of FIX and the pathogenic mechanisms of the mutations that have been identified to date. The mechanisms of FIX deficiency are diverse in these mutations. Deletions, insertions, duplications, and indels generally lead to severe hemophilia B. Those in the exon regions generate either frame shift or inframe mutations, and those in the introns usually cause aberrant splicing. Regarding point mutations, the bleeding phenotypes vary from severe to mild in hemophilia B patients. Generally speaking, point mutations in the F9 promoter region result in hemophilia B Leyden, and those in the introns cause aberrant splicing. Point mutations in the coding sequence can be missense, nonsense, or silent mutations. Nonsense mutations generate truncated FIX that usually loses function, causing severe hemophilia B. Silent mutations may lead to aberrant splicing or affect FIX translation. The mechanisms of missense mutation, however, have not been fully understood. They lead to FIX deficiency, often by affecting FIX's translation, protein folding, protein stability, posttranslational modifications, activation to FIXa, or the ability to form functional Xase complex. Understanding the molecular mechanisms of FIX deficiency will provide significant insight for patient diagnosis and treatment.

Gender-specific differences in haemostatic parameters and their influence on blood loss in bimaxillary surgery

Objective

The objectives of this prospective cohort study were to establish gender-related differences in blood loss and haemostatic profiles associated with bimaxillary surgery. In addition, we aimed to identify if any gender differences could be established which might help predict blood loss volume.

Materials and methods

Fifty-four patients (22 males; 32 females) undergoing bimaxillary surgery for skeletal dentofacial deformities were eligible for inclusion. Blood samples were taken 1 day preoperatively and 48 h postoperatively for detailed gender-specific coagulation analysis incorporating global coagulation assays (endogenous thrombin potential) and specific coagulation parameters. Blood loss was measured at two different time points: (1) the end of surgery, visible intraoperative blood loss (IOB) using ‘subtraction method’; and (2) 48 h postoperatively perioperative bleeding volume (CBL-48 h) using ‘haemoglobin-balance method’ and Nadler’s formula. Correlation and regression analyses were performed to identify relevant parameters affecting the amount of blood loss.

Results

Significant differences in IOB and CBL-48 h were observed (p < 0.001). Men had higher IOB versus women, lacking statistical significance (p = 0.056). In contrast, men had significantly higher CLB-48 h (p = 0.019). Reduced CBL-48 h was shown to be most closely associated with the level of Antithrombin-III being decreased in females.

Conclusions

Male gender is associated with higher IOB and CBL-48 compared with females. Gender does not affect IOB regarding haemostatic profile but does correlate strongly with procedure length. Conversely, CBL-48 is closely associated with gender-specific imbalances in the anticoagulant system.

Clinical relevance

Knowledge of gender-related differences will help clinicians establish predictive factors regarding excessive blood loss in orthognathic surgery and identify at-risk patients.

Mutation analysis and characterisation of F9 gene in haemophilia- B population of India

Background

Hemophilia B (HB) is an X-linked bleeding disorder resulting from coagulation factor IX defects. Over 3,000 pathogenic, HB-associated mutations in the F9 gene have been identified. We aimed to investigate the role of F9 variants in 150 HB patients using sequencing technology.

Methods

F9 gene sequences were amplified from peripheral blood-derived DNA and sequenced on an Applied Biosystems (ABI) 3500 Sanger sequencing platform. Functional and structural predictions of mutant FIX were analyzed.

Results

Among 150 HB patients, 102 (68%), 30 (20%), and 18 (12%) suffered from severe, moderate, and mild HB, respectively. Genetic analysis identified 16 mutations, including 3 novel mutations. Nine mutations (7 missense and 2 stop-gain) were found to be pathogenic. Only 3 mutations (c.127C>T, c.470G>A, and c.1070G>A) were associated with different severities. While 2 mutations were associated with mild HB cases (c.304C>T and c.580A>G), 2 (c.195G>A and c.1385A>G) and 3 mutations (c.223C>T, c.1187G>A, and c.1232G>A) resulted in moderate and severe disease, respectively. Additionally, 1 mutation each was associated with mild-moderate (c.*1110A>G) and mild-severe HB disease (c.197A>T), 4 mutations were associated with moderate-severe HB cases (c.314A>G, c.198A>T, c.676C>T, and c.1094C>A). FIX concentrations were lower in the mutated group (5.5±2.5% vs. 8.0±2.5%). Novel p.E66D and p.S365 mutations were predicted to be pathogenic based on changes in FIX structure and function.

Conclusion

Novel single nucleotide polymorphisms (SNPs) largely contributed to the pathogenesis of HB. Our study strongly suggests that population-based genetic screening will be particularly helpful to identify risk prediction and carrier detection tools for Indian HB patients.

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.

Identification of zebrafish ortholog for human coagulation factor IX and its age-dependent expression

BACKGROUND

Coagulation factor IX (FIX) is a serine protease zymogen involved in the intrinsic blood coagulation pathway, and its deficiency causes hemophilia B. Zebrafish has three f9 genes, and the ortholog to human F9 is unknown.

OBJECTIVE

To identify the zebrafish ortholog to F9 using sequence analysis and piggyback knockdown technology.

METHODS

Gene and protein sequence analysis for three f9 genes, f9a, f9b, and f9l, present in the zebrafish genome was performed. In vivo and in vitro assays after knockdown of each gene and immunodepletion using specific antibodies were carried out.

RESULTS

Sequence analysis revealed that f9a and f9b are similar to human F9, whereas f9l is similar to human F10. RNA analysis showed an age-dependent increase in expression of all three genes. Zebrafish f9a gene knockdown and Fixa immunodepletion prolonged kinetic partial thromboplastin time (kPTT), whereas f9l knockdown and Fixl immunodepletion prolonged kPTT, kinetic prothrombin time, and kinetic Russell viper venom activation time. Laser-assisted venous thrombosis increased time to occlusion after f9a and f9l knockdown and antibody inhibition of Fixa and Fixl. Further, analysis of plasma proteins by mass spectrometry and immunohistochemistry detected all three proteins.

CONCLUSIONS

Our findings suggest that zebrafish f9a has functional activity similar to human F9. Fixl is functionally similar to Fx. The age-dependent increases of these factors are comparable to those observed in mice and humans. Thus, the zebrafish model could be used to study factors involved in increasing f9a expression during aging. It could also be used to test whether normal human Factor IX and Factor IX Leyden promoter work in zebrafish background.

Bleeding Post Constriction Ring Release Surgery Causing Lower Limb Ischemia in an Infant with Undetected Hemophilia B

Bleeding in the immediate postoperative period causing compromised limb circulation is an alarming complication. It is known to occur in coagulation disorders like hemophilia. When such complications happen in a child with no previous history of bleeding problems, one has to have a low threshold for suspecting a coagulation disorder. Repeated diffuse bleeding in the whole of the surgical wound with no specific bleeders must raise the suspicion and appropriate laboratory tests must immediately be ordered. Bleeding in coagulation disorders can stop only with supplementation of the appropriate missing clotting factor. Early diagnosis is important to avoid excess morbidity. We are reporting a 6-month-old child who underwent surgery for constriction ring syndrome in the limbs with Z-plasty and developed impending limb ischemia due to bleeding in the immediate postoperative period. The article emphasizes the need to think of the possibility while encountering recurrent bleeding in the postoperative period.

Genetic analysis of carrier status in female members of Japanese hemophilia families

BACKGROUND

Genetic characteristics and genetic carrier diagnosis in Japanese hemophilia female carriers have not been evaluated.

OBJECTIVES

To provide genetic information on Japanese hemophilia female carriers and demonstrate the advantages of genetic testing in carrier diagnosis.

METHODS

DNA sequencing combined with long polymerase chain reaction for inversion and multiplex ligation-dependent probe amplification for large mutations.

RESULTS

Genetic analysis was performed in 69 male hemophiliac patients (48 hemophilia A [HA] and 21 hemophilia B [HB]) and 112 female family members (FFM) (80 from 50 families with HA and 32 from 22 families with HB). In 72 hemophiliac families, the identified F8 mutations were inversion (42%), missense (26%), and other variations (32%), while 74% of F9 mutations were point mutations. Among the 112 FFM, 53/80 (66%) with HA and 21/32 (66%) with HB were diagnosed genetically as carriers based on detection of heterozygous mutations. Low factor VIII activity (FVIII:C) levels (<50 IU/dL) were detected in only 10% of gene-confirmed carriers, suggesting that FVIII:C is not suitable for HA carrier prediction. Low FVIII/von Willebrand factor ratio (<0.9) was observed in 67% of gene-confirmed carriers. Half of the gene-confirmed HB carriers had low FIX:C (<60 IU/dL). Importantly, 32 mothers of 37 sporadic cases (86%) (24/27 [89%] HA and 8/10 [80%] HB) showed the relevant mutations, suggesting low incidence of de novo mutations in males.

CONCLUSIONS

This study is the first to provide genetic information on Japanese hemophilia female carriers. Gene analysis is the gold standard for carrier diagnosis as it well identifies undetected female carriers based on pedigree information and hemostatic measurements.

Targeting of antithrombin in hemophilia A or B with investigational siRNA therapeutic fitusiran-Results of the phase 1 inhibitor cohort

BACKGROUND

Fitusiran, an investigational small interfering RNA therapy, reduces antithrombin production to rebalance hemostasis in people with hemophilia A or B, with or without inhibitors.

OBJECTIVES

To evaluate the safety and efficacy of fitusiran treatment for people with moderate/severe hemophilia A or B with inhibitors.

PATIENTS/METHODS

In this open-label phase 1, part D study, 17 males with hemophilia A or B with inhibitors received three once-monthly subcutaneous injections of fitusiran 50 mg (n = 6) or 80 mg (n = 11); followed for up to 112 days. Endpoints included safety (primary), pharmacokinetics/pharmacodynamics (secondary), annualized bleeding rate, and patient-reported outcomes (exploratory).

RESULTS

The most common adverse event was injection site erythema (n = 8). No thrombotic events were reported. At nadir, mean (standard error of the mean [SEM]) antithrombin activity decreased from baseline by 82.0% (2.2) and 87.4% (0.7) in the 50 mg and 80 mg groups, respectively. Antithrombin reduction was associated with increased thrombin generation. 11/17 (64.7%) participants had no bleeds during the observation period (mean [standard deviation] 69.4 [16.3] days). Mean (SEM) changes from baseline in Haemophilia Quality of Life Questionnaire for Adults total (-9.2 [2.9]) and physical health (-12.3 [3.9]) domain scores suggested clinically meaningful improvement.

CONCLUSIONS

Monthly fitusiran was generally well tolerated, lowered antithrombin levels from baseline, and resulted in improved thrombin generation. These preliminary results suggest that monthly fitusiran treatment may reduce bleeding episodes and improve quality of life in participants with hemophilia A or B with inhibitors.

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.

Coagulation factor IX analysis in bioreactor cell culture supernatant predicts quality of the purified product

Coagulation factor IX (FIX) is a complex post-translationally modified human serum glycoprotein and high-value biopharmaceutical. The quality of recombinant FIX (rFIX), especially complete γ-carboxylation, is critical for rFIX clinical efficacy. Bioreactor operating conditions can impact rFIX production and post-translational modifications (PTMs). With the goal of optimizing rFIX production, we developed a suite of Data Independent Acquisition Mass Spectrometry (DIA-MS) proteomics methods and used these to investigate rFIX yield, γ-carboxylation, other PTMs, and host cell proteins during bioreactor culture and after purification. We detail the dynamics of site-specific PTM occupancy and structure on rFIX during production, which correlated with the efficiency of purification and the quality of the purified product. We identified new PTMs in rFIX near the GLA domain which could impact rFIX GLA-dependent purification and function. Our workflows are applicable to other biologics and expression systems, and should aid in the optimization and quality control of upstream and downstream bioprocesses.

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.

Inhibitor incidence in an unselected cohort of previously untreated patients with severe haemophilia B: a PedNet study

The incidence of factor IX (FIX) inhibitors in severe hemophilia B (SHB) is not well defined. Frequencies of 3-5% have been reported but most studies to date have been small, including patients with different severities, and without prospective follow up for inhibitor incidence. The study objective was to investigate the inhibitor incidence in patients with SHB followed up for to 500 exposure days (ED), the frequency of allergic reactions, and the relationship with genotypes. Consecutive previously untreated patients (PUP) with SHB enrolled into the PedNet cohort were included. Detailed data was collected for the first 50 ED, followed by the annual collection of the inhibitor status and allergic re-actions. The presence of inhibitors was defined by at least two consecutive positive samples. Additionally, data on FIX gene mutation was collected. One hundred and fifty-four PUP with SHB were included; 75% were followed up until 75 ED, and 43% until 500 ED. Inhibitors developed in 14 patients (seven high-titer). The median number of ED at inhibitor manifestation was 11 (interquartile range [IQR]: 6.5-36.5). The cumulative inhibitor incidence was 9.3% (95% Confidence Interval [CI]: 4.4-14.1) at 75 ED, and 10.2% (95% CI: 5.1-15.3) at 500 ED. Allergic reactions occurred in four (28.6%) inhibitor patients. Missense mutations were most frequent (46.8%) overall but not associated with inhibitors. Nonsense mutations and deletions with large structural changes comprised all mutations among inhibitor patients and were associated with an inhibitor risk of 26.9% and 33.3%, respectively. In an unselected, well-defined cohort of PUP with SHB, the cumulative inhibitor incidence was 10.2% at 500 ED. Nonsense mutations and large deletions were strongly associated with the risk of inhibitor development. The ‘PedNet Registry’ is registered at clinicaltrials.gov; identifier: NCT02979119.

Nucleic acids therapeutics using PolyPurine Reverse Hoogsteen hairpins

PolyPurine Reverse Hoogsteen hairpins (PPRHs) are DNA hairpins formed by intramolecular reverse Hoogsteen bonds which can bind to polypyrimidine stretches in dsDNA by Watson:Crick bonds, thus forming a triplex and displacing the fourth strand of the DNA complex. PPRHs were first described as a gene silencing tool in vitro for DHFR, telomerase and survivin genes. Then, the effect of PPRHs directed against the survivin gene was also determined in vivo using a xenograft model of prostate cancer cells (PC3). Since then, the ability of PPRHs to inhibit gene expression has been explored in other genes involved in cancer (BCL-2, mTOR, topoisomerase, C-MYC and MDM2), in immunotherapy (SIRPα/CD47 and PD-1/PD-L1 tandem) or in replication stress (WEE1 and CHK1). Furthermore, PPRHs have the ability to target the complementary strand of a G-quadruplex motif as a regulatory element of the TYMS gene. PPRHs have also the potential to correct point mutations in the DNA as shown in two collections of CHO cell lines bearing mutations in either the dhfr or aprt loci. Finally, based on the capability of PPRHs to form triplexes, they have been incorporated as probes in biosensors for the determination of the DNA methylation status of PAX-5 in cancer and the detection of mtLSU rRNA for the diagnosis of Pneumocystis jirovecii. Of note, PPRHs have high stability and do not present immunogenicity, hepatotoxicity or nephrotoxicity in vitro. Overall, PPRHs constitute a new economical biotechnological tool with multiple biomedical applications.

Molecular analysis of 76 Chinese hemophilia B pedigrees and the identification of 10 novel mutations

BACKGROUND

Hemophilia B (HB) is an X-linked recessive inherited bleeding disorder caused by mutations in the F9 gene that lead to plasma factor IX deficiency. To identify the causative mutations in HB, a molecular analysis of HB pedigrees in China was performed.

METHODS

Using next-generation sequencing (NGS) and an in-house bioinformatics pipeline, 76 unrelated HB pedigrees were analyzed. The mutations identified were validated by comparison with the results of Sanger sequencing or Multiplex Ligation-dependent Probe Amplification assays. The pathogenicity of the causative mutations was classified following the American College of Medical Genetics and Genomics guidelines.

RESULTS

The mutation detection rate was 94.74% (72/76) using NGS. Of the 76 HB pedigrees analyzed, 59 causative variants were found in 72 pedigrees, with 38 (64.41%) missense mutations, 9 (15.25%) nonsense mutations, 2 (3.39%) splicing mutations, 5 (8.47%) small deletions, 4 (6.78%) large deletions, and 1 intronic mutation (1.69%). Of the 59 different F9 mutations, 10 were novel: c.190T>G, c.199G>T, c.290G>C, c.322T>A, c.350_351insACAATAATTCCTA, c.391+5delG, c.416G>T, c.618_627delAGCTGAAACC, c.863delA, and c.1024_1027delACGA. Of these 10 novel mutations, a mosaic mutation, c.199G>T(p.Glu67Ter), was identified in a sporadic HB pedigree. Using in-silico analysis, these novel variants were predicted to be disease-causing. However, no potentially causative mutations were found in the F9 coding sequences of the four remaining HB pedigrees. In addition, two HB pedigrees carrying additional F8/F9 mutations were discovered.

CONCLUSION

The identification of these mutations enriches the spectrum of F9 mutations and provides further insights into the pathogenesis of HB in the Chinese population.