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Abstract: Coagulation factor VIII (FVIII) is essential for hemostasis. After activation, it combines with activated FIX (FIXa) on anionic membranes to form the intrinsic Xase enzyme complex, responsible for activating FX in the rate-limiting step of sustained coagulation. Hemophilia A (HA) and hemophilia B are due to inherited deficiencies in the activity of FVIII and FIX, respectively. Treatment of HA over the last decade has benefited from an improved understanding of FVIII biology, including its secretion pathway, its interaction with von Willebrand factor in circulation, the biochemical nature of its FIXa cofactor activity, the regulation of activated FVIII by inactivation pathways, and its surprising immunogenicity. This has facilitated biotechnology innovations with first-in-class examples of several new therapeutic modalities recently receiving regulatory approval for HA, including FVIII-mimetic bispecific antibodies and recombinant adeno-associated viral (rAAV) vector-based gene therapy. Biological insights into FVIII also guide the development and use of gain-of-function FVIII variants aimed at addressing the limitations of first-generation rAAV vectors for HA. Several gain-of-function FVIII variants designed to have improved secretion are currently incorporated in second-generation rAAV vectors and have recently entered clinical trials. Continued mutually reinforcing advancements in the understanding of FVIII biology and treatments for HA are necessary to achieve the ultimate goal of hemophilia therapy: normalizing hemostasis and optimizing well-being with minimal treatment burden for all patients worldwide., (© 2024 American Society of Hematology. Published by Elsevier Inc. All rights are reserved, including those for text and data mining, AI training, and similar technologies.)

Abstract: This article discusses novel genetic therapies for sickle cell disease, Duchenne muscular dystrophy, and hemophilia A. Gene therapies have the potential to deliver more targeted and effective approaches to treatment, especially for rare diseases for which the availability of approved therapies is limited. This article describes the first FDA-approved CRISPR/Cas9 treatment and the treatment protocols, indications, warnings, precautions, cost, and contraindications of four novel genetic therapies., (Copyright © 2024 American Academy of Physician Associates.)

Adeno-associated virus (AAV) vector gene therapy provides a promising platform for treatment of monogenic inherited disorders. Clinical studies have demonstrated long-term expression with reduction in bleeding using this approach for the treatment of hemophilia. Despite these advances, there are unknowns surrounding the natural history of recombinant AAV (rAAV) vectors and the cellular mechanisms mediating vector persistence. These unknowns underpin questions regarding long-term efficacy and safety. The predominant mechanism via which AAV is proposed to persist is in circular double-stranded extrachromosomal DNA structures (episomes) within the nucleus. Studies of wild-type AAV (WT-AAV) and rAAV have demonstrated that AAV also persists via integration into a host cell's DNA. It is important to determine whether these integration events can mediate expression or could result in any long-term safety concerns. WT-AAV infection affects a large proportion of the general population, which is thought to have no long-term sequelae. Recent studies have highlighted that this WT-AAV has been detected in cases of acute hepatitis in children and in a minority of cases of hepatocellular carcinoma. Integration following treatment using rAAV has also been reported in preclinical and clinical studies. There have been variable reports on the potential implications of integration for rAAV vectors, with data in some murine studies demonstrating recurrent integration with development of hepatocellular carcinoma. These findings have not been seen in other preclinical or clinical studies. In this review, we will summarize current understanding of the natural history of AAV (wild-type and recombinant) with a focus on genomic integration and cellular implications., Competing Interests: Declaration of competing interests P.B. has received research support from BioMarin and consulting fees or honoraria from BioMarin, Octapharma, Novo Nordisk, CSL Behring, Pfizer, and Institute for Nursing and Medication Education (IMNE). D.L. has received research support from BioMarin, CSL Behring, and Sanofi and has received consulting fees or honoraria from BioMarin, CSL Behring, Novo Nordisk, Pfizer, and Sanofi., (Copyright © 2024 International Society on Thrombosis and Haemostasis. Published by Elsevier Inc. All rights reserved.)

Background: Platelet gene therapy is effective in hemophilia A (HA) mice even with inhibitors. Fludarabine (Flu), along with busulfan (Bu) or melphalan (Mel), preconditioning has been shown to be highly effective for hematopoietic stem cell transplantation in the clinic., Objectives: To evaluate the efficacy of Bu-Flu and Mel-Flu preconditioning in platelet gene therapy of HA with inhibitors., Methods: Bu-Flu and Mel-Flu were used to condition HA mice preimmunized with recombinant human factor (F)VIII. An optimal 660 centigray total body irradiation was used as a control regimen in parallel. Platelet-FVIII expression was introduced by transplantation of 2bF8 lentivirus (LV)-transduced hematopoietic stem cells. Animals were analyzed by fluorescence-activated cell sorting, quantitative polymerase chain reaction, FVIII assays, and tail bleeding tests., Results: Bu-Flu, but not Mel-Flu, enabled successful 2bF8 gene therapy. All recipients achieved >55% chimerism post hematopoietic stem cell transplantation in both Bu-Flu and 660 centigray groups, with comparable copy numbers of 2bF8 cassette and the platelet-FVIII levels. The bleeding phenotype was rescued in 2bF8LV-transduced recipients. FVIII inhibitor titers declined with time, with comparable disappearance time of inhibitors between the 2 groups. When animals were rechallenged with recombinant human FVIII after the titers dropped to undetectable levels, no inhibitors were detected in 2bF8LV-transduced recipients. In contrast, all untransduced transplanted control mice produced inhibitors. These data demonstrate that immune tolerance was established in 2bF8LV-transduced primed HA mice under Bu-Flu conditioning., Conclusion: Bu-Flu preconditioning allows for successfully introducing platelet-FVIII expression to restore hemostasis and induce immune tolerance in primed HA mice, suggesting that this approach is a promising clinically translatable strategy for gene therapy of HA with inhibitors., Competing Interests: Declaration of competing interests There are no competing interests to disclose., (Copyright © 2024 International Society on Thrombosis and Haemostasis. Published by Elsevier Inc. All rights reserved.)

Abstract: Despite numerous efforts to raise awareness, many hemophilia carriers and female persons with hemophilia (PWHs) remain undiagnosed. Between May 2021 and April 2023, we identified potential and obligate carriers of hemophilia A (HA) and hemophilia B (HB) by updating pedigrees of all PWHs followed at the Cliniques universitaires Saint-Luc, Brussels. Retrospective data on previously screened females were collected, including bleeding history, coagulation factor levels, and testing for the proband's pathogenic variant. In addition, a proactive approach involved sending 125 invitation letters to unscreened or incompletely screened individuals, through related PWHs. In pedigrees of 287 male PWHs (226 HA and 61 HB) and 7 female index patients from 236 families (184 HA and 52 HB), a total of 900 female individuals were identified. Of those, 454 were obligate and/or genetically proven carriers, and 118 were noncarriers. Genetic testing was conducted in 133 obligate, 237 potential, and 4 sporadic carriers, with 190 obligate and 328 potential carriers remaining untested. Among carriers with known factor levels (261/454), 42 HA (23.0%) and 23 HB carriers (29.5%) had a factor level <40 IU/dL. Carriers with a factor deficiency were screened on average 6 years earlier than other females (P = .034). This study, to our knowledge, represents the first systematic effort to identify potential carriers among families of all PWHs within a single center, emphasizing the challenges in comprehensive screening for female individuals genetically linked to one or more PWHs. Such initiatives are vital for achieving equitable access to hemophilia care for all potentially affected individuals, irrespective of gender. This trial was registered at www.ClinicalTrials.gov as #NCT05217992., (© 2024 by The American Society of Hematology. Licensed under Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0), permitting only noncommercial, nonderivative use with attribution. All other rights reserved.)

Abstract: After successful efforts in adeno-associated virus (AAV) gene addition for hemophilia B gene therapy, the development of valoctocogene roxaparvovec (Roctavian; Biomarin) over the past decade represents a potential new hemophilia A (HA) treatment paradigm. Roctavian is the first licensed HA gene therapy that was conditionally approved in Europe in August 2022 and approved in the United States in June 2023. Beyond Roctavian, there are ongoing pivotal trials of additional AAV vectors for HA, others that are progressing through preclinical development or early-phase clinical trial, as well as non-AAV approaches in clinical development. This review focuses on the clinical development of Roctavian for which the collective clinical trials represent the largest body of work thus far available for any licensed AAV product. From this pioneering clinical development, several outstanding questions have emerged for which the answers will undoubtedly be important to the clinical adaptation of Roctavian and future efforts in HA gene therapy. Most notably, unexplained year-over-year declines in factor VIII (FVIII) expression after Roctavian treatment contrast with stable FVIII expression observed in other AAV HA gene therapy clinical trials with more modest initial FVIII expression. This observation has been qualitatively replicated in animal models that may permit mechanistic study. The development and approval of Roctavian is a landmark in HA therapeutics, although next-generation approaches are needed before HA gene therapy fulfills its promise of stable FVIII expression that normalizes hemostasis., (© 2024 by The American Society of Hematology. Licensed under Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0), permitting only noncommercial, nonderivative use with attribution. All other rights reserved.)

Abstract: Gene therapy for severe hemophilia A uses an adeno-associated virus (AAV) vector and liver-specific promoters that depend on healthy hepatocyte function to achieve safe and long-lasting increases in factor VIII (FVIII) activity. Thus, hepatocyte health is an essential aspect of safe and successful gene therapy. Many people living with hemophilia A have current or past chronic hepatitis C virus infection, metabolic dysfunction-associated steatosis or steatohepatitis, or other conditions that may compromise the efficacy and safety of AAV-mediated gene therapy. In addition, gene therapy may induce an immune response to transduced hepatocytes, leading to liver inflammation and reduced FVIII activity. The immune response can be treated with immunosuppression, but close monitoring of liver function tests and factor levels is necessary. The long-term risk of hepatocellular carcinoma associated with gene therapy is unknown. Routine screening by imaging for hepatocellular carcinoma, preferable every 6 months, is essential in patients at high risk and recommended in all recipients of hemophilia A gene therapy. This paper describes our current understanding of the biologic underpinnings of how liver health affects hemophilia A gene therapy, and provides practical clinical guidance for assessing, monitoring, and managing liver health both before and after gene therapy., (© 2024 by The American Society of Hematology. Licensed under Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0), permitting only noncommercial, nonderivative use with attribution. All other rights reserved.)

A 3-month-old domestic shorthair tomcat born on a farm was unsuccessfully treated with meloxicam for alternating lameness, fever and inappetence. On presentation, there was lameness (grade 2/4) of the right forelimb with mild swelling of the soft tissue. Rectal temperature was 39.9°C, a moderate anemia developed. Inadequate bleeding occurred during arthrocentesis performed on suspicion of polyarthritis. Coagulation tests revealed an isolated prolonged activated partial thromboplastin time (aPTT). Activity of factor VIII was 5% (reference range: 70-125%), of factor IX 55% (80-130%), and of factor XII 73% (50-140%).In a genetic study, exons and adjacent intron sequences of the feline F8-gene were sequenced and compared with the reference (ENSFCAT000078256.1). While no non-synonymous variants were found in coding sequences, intron 19 revealed the variant c.6073+2 T>C. This variant likely results in splice site alteration, atypical splicing, and thus an altered mRNA for FVIII.The patient was treated symptomatically (metamizole, buprenorphine, tranexamic acid) and clinical signs improved. Chemical castration with a GnRH implant was performed at 8 and 18 months of age, whereby minor bleeding at the implantation site occurred after the second implantation. After 3.5 years, the cat lives nearly without clinical signs of bleeding.aPTT prolongation with normal PT indicated a factor deficiency. Determination of factor activity led to the diagnosis of hemophilia A. Genetic testing detected a splice variant in the F8-gene., Competing Interests: Die Autoren versichern, dass keine persönlichen Interessen, sei es beruflicher oder anderer Art, an einem Produkt oder Unternehmen bestehen, die Einfluss auf die im vorliegenden Fallbericht behandelten Inhalte ausüben könnten., (Thieme. All rights reserved.)

Background: In 2022-2023, the US Food and Drug Administration approved 2 novel gene therapies, valoctocogene roxaparvovec and etranacogene dezaparavovec, for hemophilia A and B, respectively. These one-time-administered gene therapies have been marketed at prices that create financial challenges for payers and patients. Understanding the magnitude and uncertainties around the long-term value of these therapies and how they can potentially relate to managed care practices is of high interest to the payer and patient community., Objective: To conduct a systematic review of cost-effectiveness analysis (CEA) studies to assess (1) the long-term value of valoctocogene roxaparvovec and etranacogene dezaparavovec and (2) the relevance and validity of the underlying data and assumptions used in the CEA models and discuss how they relate to the challenges identified for CEAs of gene therapies., Methods: A systematic review of cost-effectiveness studies of novel hemophilia A and B gene therapy was conducted. PubMed and Embase were searched for published studies from inception to January 12, 2024. Original research articles published in English that conducted a CEA on gene therapy treatments for hemophilia A and B, with a comparison of incremental costs and health effects, were considered. Critical appraisal of the quality of reporting and the underlying modeling assumptions were conducted to assess the relevance and validity of the results., Results: Two hundred thirty-eight studies were identified, of which 4 met the inclusion criteria. Three studies were conducted from a US health care perspective and 1 from a Dutch societal perspective. Despite the high upfront costs of the gene therapies, all included studies' (3 hemophilia A and 1 hemophilia B) modeled results showed that gene therapies had lower overall costs and better health outcomes compared with factor concentrate replacement therapies and emicizumab. The results were driven by the assumption that gene therapies will have a durable effect of at least 10 years and offset the high cost of the current standard of care. The modeled health improvements varied substantially across studies, showing that the long-term value is sensitive to varying clinical and economic assumptions., Conclusions: The novel hemophilia gene therapy treatments can potentially be a cost-effective use of treatment resources if the treatment effects are durable over time. To reduce the risk for payers while still facilitating patient access, outcomes-based agreements similar to what has recently been proposed by the Centers for Medicare & Medicaid Services for sickle-cell therapies are well supported.

Prophylactic replacement therapy for hemophilia A (hereditary factor VIII deficiency) is a success story of the production of coagulation factor concentrates from donor plasma. Recombinant factor concentrates, which are also produced with modified gene constructs for coagulation factor VIII in order to improve pharmacological properties, have since proven their worth. This successful development over many years of factor concentrates for the successful treatment of hemophilia patients has now been followed by the innovation of a factor VIII mimetic in the form of a monoclonal antibody, which was developed in Japan already some years back. Emicizumab is a humanized, bispecific monoclonal antibody for therapeutic use in hemophilia A. With this therapeutic agent, the treatment of the hereditary coagulation defect is based, for the first time, on a completely new active principle. The specific antibody simulates the properties of coagulation factor VIII as a cofactor for the formation of the tenase complex with the coagulation factors IX and X. As a result under steady state conditions almost normal thrombin and thus fibrin formation can be achieved., (© 2024. The Author(s), under exclusive licence to Springer Medizin Verlag GmbH, ein Teil von Springer Nature.)

Background: Tissue factor pathway inhibitor (TFPI) regulates tissue factor-triggered coagulation. Humans and mice express transcripts encoding for multidistributed (endothelial, platelet, and plasma) 3-Kunitz domain TFPIα and endothelial membrane-anchored 2-Kunitz TFPIβ. Mice express a third transcript, γ, that encodes plasma lipoprotein-associated 2-Kunitz TFPI. In humans, proteolysis of α and/or β produces plasma lipoprotein-associated 2-Kunitz TFPI at lower levels. In clinical trials, monoclonal antibodies that target all TFPI isoforms extend coagulation and correct bleeding in hemophilic patients but with some thrombosis risks., Objectives: To determine the impact of TFPI isoform-specific deletions on promoting clotting in hemophilic mice., Methods: Engineered TFPI isoform-specific, hemophilic (factor VIII-null) mice were evaluated for clotting., Results: Mice expressing any single TFPI isoform were healthy. Thrombin generation assays identified TFPIγ as the dominant anticoagulation isoform in mouse plasma. Hemostasis was assessed by serial bleeding times from a tail vein laceration. Repeatedly, after a clot forms, it was manually disrupted; the number of clots/disruptions occurring over a 15-minute period were reported. C57BL/6 and hemophilic mice clot on average 25.6 vs 5.4 times, respectively. On a hemophilia background, TFPIβ or TFPIγ-specific deletion improved clotting to 14.6 and 15.2 times, respectively (P < .0001). TFPIα-specific deletion was without impact, clotting 5.1 times. Heterozygous deletion of TFPIβ was effective, clotting 11.8 times (P < .0001). Heterozygous deletion of TFPIα or TFPIγ alone was ineffective, clotting 3.0 and 6.1 times, respectively, but heterozygous TFPIαγ deletion improved clotting to 11.2 times (P < .001)., Conclusion: In hemophilic mice, endothelial TFPIβ and plasma γ-derived 2-Kunitz TFPI individually contribute more to bleeding than total TFPIα., Competing Interests: Declaration of competing interests All authors have no competing interests to disclose., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

Introduction: Hemophilia A is an inherited bleeding disorder caused by pathogenic variants in the factor VIII gene (F8), which leads to factor VIII (FVIII) deficiency. Immune tolerance induction (ITI) is a therapeutic approach to eradicate alloantibodies (inhibitors) against exogenous FVIII in people with inherited hemophilia A. Few studies have evaluated the role of F8 variants on ITI outcome., Material and Methods: We included people with severe hemophilia A (FVIII ˂ 1 international units/dL) and high-responding inhibitors (≥ 5 Bethesda units/mL lifelong) who underwent a first course of ITI. Socio-demographic, clinical and laboratory data were collected. ITI outcomes were defined as total, partial successes, and failure. Detection of intron 1 and 22 inversions was performed by polymerase-chain reaction, followed by F8 sequencing., Results: We included 168 people with inherited hemophilia A and high-responding inhibitors, median age 6 years at ITI start. Intron 22 inversion was the most prevalent variant (53.6 %), followed by nonsense (16.1 %), small insertion/deletion (11.3 %), and large deletion (10.7 %). In comparison with intron 22 inversion, the odds of ITI failure were 15.5 times higher (odds ratio [OR] 15.50; 95 % confidence interval [95 % CI] 4.59-71.30) and 4.25 times higher (95 % CI, 1.53-12.3) among carriers of F8 large deletions and small insertions and deletions, respectively., Conclusion: F8 large deletions and small insertions/deletions predicted ITI failure after a first course of ITI in patients with severe hemophilia A and high-responding inhibitors. This is the first study to show F8 large deletions and small insertions/deletions as predictors of ITI failure., Competing Interests: Declaration of competing interest RMC received speaker fees from Bayer, NovoNordisk, Hoffman-La Roche, and Takeda, consultancy fees from Hoffman-La Roche and Takeda, and sponsorship to attend scientific event grants from Bayer, NovoNordisk, Hoffman-La Roche, and Takeda. AGO received speaker fees and scientific event grants from NovoNordisk and Takeda. MRFR received speaker fees from NovoNordisk, scientific event grants from Hoffman-La Roche, Takeda and NovoNordisk, and consultancy fees from the Brazilian Ministry of Health. FMRAC received sponsorship to attend scientific event grants from Hoffman-La Roche and NovoNordisk. LYE received scientific event grants from Hoffman-La Roche. MAFC received sponsorship to attend scientific event grants from Hoffman-La Roche and NovoNordisk. ISSP received speaker fees from Hoffman-La Roche, NovoNordisk and Takeda, sponsorship to attend scientific event grants from Hoffman-La Roche, Takeda and NovoNordisk, consultancy fees from the Hoffman-La Roche, NovoNordisk, Bayer and Biomarin, and grants for scientific publication from Takeda. AAG received speaker fees from Takeda and NovoNordisk, sponsorship to attend scientific event grants from Takeda and NovoNordisk, and consultancy fees from NovoNordisk. THA received sponsorship to attend scientific event grants from Hoffman-La Roche and Takeda. DCFN received sponsorship to attend scientific event grants from Takeda. LWZ, RPS, MMD, MAPS, LLJ, RAR, MHC, CSL, DMT, VKBF, RPT, DGC, JVDB and SMR declare they have no competing interests which might be perceived as posing as a conflict., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Background:  Desmopressin (DDAVP) is used in patients with moderate/mild hemophilia A (PWMHs) to increase their factor VIII (FVIII) level and, if possible, normalize it. However, its effectiveness varies between individuals. The GIDEMHA study aims to investigate the influence of F8 gene variants., Material and Methods:  The study collected the trajectory of FVIII levels from therapeutic intravenous DDAVP tests in four French hemophilia treatment centers. A pharmacological analysis was performed associated with efficacy scores according to F8 variants: absolute and relative responses, as well as new scores: absolute duration (based on duration with FVIII ≥ 0.50 IU.mL -1 ) and relative duration (based on half-life)., Results:  From enrolled 439 PWMHs, 327 had a hot-spot F8 variant (with ≥5 PWMHs). For these, the median (min-max) basal and peak FVIII were 0.20 (0.02-0.040) and 0.74 (0.14-2.18) IU.mL -1 respectively, with FVIII recovery being 3.80 IU.ml -1 (1.15-14.75). The median FVIII half-life was 3.9 hours (0.7-15.9 hours). FVIII was normalized (≥0.50 IU.mL -1 ) in 224/327 PWMHs (69%) and the median time with normalized FVIII was 3.9 hours (0.0-54.1 hours). Following the response profiles to DDAVP defined by the four efficacy scores, four groups of F8 variants were isolated, and then compared using survival curves with normalized FVIII ( p  < 0.0001): "long-lastingly effective" [p.(Glu739Lys), p.(Ser2030Asn), p.(Arg2178His), p.(Gln2208Glu), and T-stretch deletion in intron 13]; "moderately effective" [p.(Ser112Phe), p.(Ala219Thr), p.(Thr2105Ile), p.Phe2146Ser), and p.(Asp2150Asn)]; "moderately ineffective" [p.Ala81Asp), p.(Gln324Pro), p.(Tyr492His), p.(Arg612Cys), p.(Met701Val), p.(Val2035Asn), and p.(Arg2178Cys)]; and "frequently ineffective" [c.-219C > T, p.(Cys2040Tyr), p.(Tyr2169His), p.(Pro2319Leu), and p.(Arg2326Gln)]., Conclusion:  In view of our data, we propose indications for DDAVP use in PWMH based on F8 variants for minor and major invasive procedures., Competing Interests: B.G. has received grants or consultant fees from CSL-Behring, LFB, NovoNordisk, Octapharma, Roche/Chugaï, and Sobi. Y.R. has received funding or consultant fees from BioMarin, CSL-Behring, LFB, NovoNordisk, Octapharma, Roche, Shire, Sobi, and Takeda. X.D. has received honoraria for participation in symposia by CSL Behring, Shire, Octapharma, and Sobi. M.T. has received funding or consultant fees from Bayer Healthcare, CSL-Behring, NovoNordisk, Octapharma, Parexel, Roche, Sanofi, Shire, Sobi, and Takeda. P.J.L. has received grants from Pfizer, Sanofi, Sobi, and Roche. M.P., S.B., P.Be., and P.Bo. declare no disclosure., (Thieme. All rights reserved.)

Severe protein C deficiency (SPCD) is a rare inherited thrombotic disease associated with high morbidity and mortality. In the current study, we established a viable murine model of SPCD, enabling preclinical gene therapy studies. By creating SPCD mice with severe hemophilia A (PROC -/- /F8 - ), the multi-month survival of SPCD mice enabled the exploration of recombinant adeno-associated viral vector-PC (rAAV8-PC) gene therapy (GT). rAAV8- PC (10 12 vg/kg of AAV8-PC) was injected via the tail vein into 6-8-week-old PROC -/- /F8 - mice. Their plasma PC antigen levels (median of 714 ng/mL, range 166-2488 ng/mL) and activity (303.5 ± 59%) significantly increased to the normal range after GT compared to untreated control animals. PC's presence in the liver after GT was also confirmed by immunofluorescence staining. Our translational research results provide the first proof of concept that an infusion of rAAV8-PC increases PC antigen and activity in mice and may contribute to future GT in SPCD. Further basic research of SPCD mice with prolonged survival due to the rebalancing of this disorder using severe hemophilia A may provide essential data regarding PC's contribution to specific tissues' development, local PC generation, and its regulation in inflammatory conditions.

One of the major challenges in the choice of the best therapeutic approach for the treatment of patients affected by hemophilia A (HA) is the definition of criteria predicting the formation of factor VIII (FVIII) neutralizing antibodies, called inhibitors. Both genetic and environmental elements influencing the immune response toward FVIII have been identified but still not all the factors causing the pathological rejection of FVIII have been identified. Since there is a connection between coagulation and inflammation, here we assessed the role played by the FVIII deficiency in shaping the humoral and cellular response toward an antigen other than FVIII itself. To this aim, we challenged both HA and wild-type (WT) mice with either FVIII or ovalbumin (OVA) and followed antigen-specific antibody level, immune cell population frequency and phenotype up to 9 weeks after the last antigen booster. The activation threshold was evaluated in vitro by stimulating the murine T cells with a decreasing dose of α-CD3. The humoral response to FVIII was similar between the two groups while both the in vivo and in vitro experiments highlighted an antigen-independent sensitivity of HA compared with WT T cells causing an increase in memory T-cell conversion and proliferation capability., (© 2024 Wiley‐VCH GmbH.)

Background: Haemophilic arthropathy (HArt) is a serious complication in patients with hemophilia. Early diagnosis and treatment are essential to minimise the development of HArt. The use of biomarkers may improve early diagnosis of HArt. Circulating microRNAs (miRNAs) are small, non-coding RNAsthat regulate gene expression, and are being investigated as promising biomarkers due to their role in joint and bone metabolism., Aims: To investigate differential expression of miRNAs and their relationship to arthropathy in patients with hemophilia A., Methods: miRNA expression was examined in a pilot study followed by a validation study (100 hemophilia A patients with [n = 83] and without HArt [n = 17], 14 controls). Differential miRNA expression was investigated using real-time quantitative PCR., Results: The pilot study identified 2 miRNAs differentially expressed in patients with Hart (Pettersson score ≥ 1), after adjusting for the false discovery rate (FDR). The validation study evaluated these 2 miRNAs. The results demonstrated that two miRNAs (miR- 208a-3p and 524-3p) were significantly underexpressed in plasma of patients with HArt compared to patients without arthropathy, with FDR <0.05 (Fig. 1). In addition, 3 miRNAs (130a-3p, miR- and 506-3p) were significantly underexpressed in patients with moderate HArt (Pettersson score 4 to 7)., Conclusions: In this proof of concept study we identified a signature of 5 circulating miRNAs associated with Hart with potential as diagnosis tools for HArt. These miRNAs are potential negative regulators of gene expression, suggesting their activity in HArt by interfering with osteoblastic (miR- 208a-3p) and osteoclastic (miR-506-3p) differentiation to impair bone mineralization and remodeling processes, or regulating chondrogenesis (miR-335-5p). miRNAs associated with earlier stages of HArt will be further investigated in a sub-study of the prospective clinical trial PROVE, which will investigate the effects of long-term prophylaxis with simoctocog alfa versus emicizumab in adults with hemophilia A., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Hemophilia A is a rare bleeding disorder with variable expressivity and allelic heterogeneity. Despite the advancement of prenatal diagnostics and molecular studies, the number of studies reviewing the reproductive choices of hemophilia A carriers and affected individuals remains limited. Through this retrospective review, we hope to gain a deeper understanding of hemophilia A-affected individuals' clinical and molecular characteristics, as well as the reproductive choices of the at-risk couples. A total of 122 individuals harboring likely causative F8 gene alterations from 64 apparently unrelated families attending three centers between 3/2000 and 3/2023 were included in this study. Their clinical and molecular findings as well as reproductive choices were gathered in a clinical setting and verified through the electronic medical record database of the public health system. Forty-seven affected males and 75 female heterozygous carriers were included in the analysis. Among 64 apparently unrelated families, 36 distinct pathogenic/likely pathogenic variants were identified, of which 30.6% (11/36) of variants were novel. While the majority of clinical findings and genotype-phenotype correlations appear to be in accordance with existing literature, female carriers who had no fertility intention were significantly more likely to have affected sons than those who had fertility intention (5/19 vs. 4/5; p = 0.047). Through this retrospective review, we summarized the clinical and molecular characteristics of 122 individuals harboring pathogenic/likely pathogenic F8 variants, as well as their fertility intentions and reproductive outcomes. Further studies are required to look into the considerations involved in reproductive decision-making., (© 2024 The Authors. American Journal of Medical Genetics Part A published by Wiley Periodicals LLC.)

Durable factor VIII expression that normalizes hemostasis is an unrealized goal of hemophilia A adeno-associated virus-mediated gene therapy. Trials with initially normal factor VIII activity observed unexplained year-over-year declines in expression while others reported low-level, stable expression inadequate to restore normal hemostasis. Here we demonstrate that male mice recapitulate expression-level-dependent loss of factor VIII levels due to declines in vector copy number. We show that an enhanced function factor VIII variant (factor VIII-R336Q/R562Q), resistant to activated protein C-mediated inactivation, normalizes hemostasis at below-normal expression without evidence of prothrombotic risk in male hemophilia A mice. These data support that factor VIII-R336Q/R562Q may restore normal factor VIII function at low levels of expression to permit durability using low vector doses to minimize dose-dependent adeno-associated virus toxicities. This work informs the mechanism of factor VIII durability after gene transfer and supports that factor VIII-R336Q/R562Q may safely overcome current hemophilia A gene therapy limitations., (© 2024. The Author(s).)

Background: Hemophilia A (HA) is an X-linked recessive genetic disorder caused by pathogenic variations of the factor VIII -encoding gene, F8 gene. Due to the large size and diverse types of variations in the F8 gene, causative mutations in F8 cannot be simultaneously detected in one step by traditional molecular analysis, and genetic molecular diagnosis and prenatal screening of HA still face significant difficulties and challenges in clinical practice. Therefore, we aimed to develop and validate an efficient, accurate, and time-saving method for the genetic detection of HA., Methods: A comprehensive analysis of hemophilia A (CAHEA) method based on long-range PCR and long-read sequencing (LRS) was used to detect F8 gene mutations in 14 clinical HA samples. The LRS results were compared with those of the conventional methods to evaluate the accuracy and sensitivity of the proposed approach., Results: The CAHEA method successfully identified 14 F8 variants in all probands, including 3 small insertion deletions, 4 single nucleotide variants, and 7 intron 22 inversions in a "one-step" manner, of which 2 small deletions have not been reported previously. Moreover, this method provided an opportunity to analyze the mechanism of rearrangement and the pathogenicity of F8 variants. The LRS results were validated and found to be in 100% agreement with those obtained using the conventional method., Conclusion: Our proposed LRS-based F8 gene detection method is an accurate and reproducible genetic screening and diagnostic method with significant clinical value. It provides efficient, comprehensive, and accurate genetic screening and diagnostic services for individuals at high risk of HA as well as for premarital and prenatal populations., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Abstract: A2 domain dissociation in activated factor VIII (FVIIIa) results in reduced activity. Previous studies demonstrated that some FVIII mutants (D519V/E665V and K1813A) with delayed A2 dissociation enhanced coagulation potential. We speculated, therefore, that FVIII encompassing a combination of these mutations might further enhance coagulant activity. The aim was to assess the D519V/E665V/K1813A-FVIII mutation as a gain of function. The FVIII mutants, D519V/E665V/K1813A, D519V/E665V, and K1813A were expressed in a baby hamster kidney cell system, and global coagulation potential of these mutants was compared with wild-type (WT) FVIII in vitro and in hemophilia A mice in vivo. Kinetic analyses indicated that the apparent Kd for FIXa on the tenase assembly with D519V/E665V and D519V/E665V/K1813A mutants were lower, and that the generated FXa for D519V/E665V/K1813A was significantly greater than WT-FVIII. WT-FVIII activity after thrombin activation increased by ∼12-fold within 5 minutes, and returned to initial levels within 30 minutes. In contrast, The FVIII-related activity of D519V/E665V/K1813A increased further with time after thrombin activation, and showed an ∼25-fold increase at 2 hours. The A2 dissociation rate of D519V/E665V/K1813A was ∼50-fold slower than the WT in a 1-stage clotting assay. Thrombin generation assays demonstrated that D519V/E665V/K1813A (0.125 nM) exhibited coagulation potential comparable with that of the WT (1 nM). In animal studies, rotational thromboelastometry and tail-clip assays showed that the coagulation potential of D519V/E665V/K1813A (0.25 μg/kg) was equal to that of the WT (2 μg/kg). FVIII-D519V/E665V/K1813A mutant could provide an approximately eightfold increase in hemostatic function of WT-FVIII because of increased FVIIIa stability and the association between FVIIIa and FIXa., (© 2024 by The American Society of Hematology. Licensed under Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0), permitting only noncommercial, nonderivative use with attribution. All other rights reserved.)

Gene therapy for hemophilia is a groundbreaking treatment approach with promising results and potential to reduce the burden of the disease. However, uncertainties remain, particularly regarding the liver side effects of AAV gene therapy, which are more common in hemophilia A. Unlike some other diseases, such as spinal muscular atrophy, where the target cell for gene therapy is different from the one affected by side effects, hemophilia gene therapy operates within the same cellular domain-the hepatocyte. This overlap is challenging and requires a targeted strategy to mitigate the risks associated with liver injury, which often requires temporary immunosuppressive therapy. A comprehensive approach is essential to increase the efficacy of gene therapy and reduce the likelihood of hepatocyte damage. Key components of this strategy include a thorough pre-gene therapy assessment of liver health, careful post-gene therapy liver monitoring, and prompt therapeutic intervention for loss of transgene expression and liver injury. Collaboration between hematologists and hepatologists is essential to ensure a well-coordinated management plan for patients undergoing hemophilia gene therapy. This review addresses the critical aspect of hepatic comorbidities in patients with hemophilia, emphasizing the need to identify and address these issues prior to initiating gene therapy. It examines the known mechanisms of liver damage and emphasizes the importance of liver monitoring after gene therapy. In addition, the review draws insights from experiences with other AAV-based gene therapies, providing valuable lessons that can guide hemophilia centers in effectively managing liver damage associated with hemophilia gene therapy., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Background: Replacement and nonreplacement therapies effectively control bleeding in hemophilia A (HA) but imply lifelong interventions. Authorized gene addition therapy could provide a cure but still poses questions on durability. FVIIIgene correction would definitively restore factor (F)VIII production, as shown in animal models through nuclease-mediated homologous recombination (HR). However, low efficiency and potential off-target double-strand break still limit HR translatability., Objectives: To correct common model single point mutations leading to severe HA through the recently developed double-strand break/HR-independent base editing (BE) and prime editing (PE) approaches., Methods: Screening for efficacy of BE/PE systems in HEK293T cells transiently expressing FVIII variants and validation at DNA (sequencing) and protein (enzyme-linked immunosorbent assay; activated partial thromboplastin time) level in stable clones. Evaluation of rescue in engineered blood outgrowth endothelial cells by lentiviral-mediated delivery of BE., Results: Transient assays identified the best-performing BE/PE systems for each variant, with the highest rescue of FVIII expression (up to 25% of wild-type recombinant FVIII) for the p.R2166∗ and p.R2228Q mutations. In stable clones, we demonstrated that the mutation reversion on DNA (∼24%) was consistent with the rescue of FVIII secretion and activity of 20% to 30%. The lentiviral-mediated delivery of the selected BE systems was attempted in engineered blood outgrowth endothelial cells harboring the p.R2166∗ and p.R2228Q variants, which led to an appreciable and dose-dependent rescue of secreted functional FVIII., Conclusion: Overall data provide the first proof-of-concept for effective BE/PE-mediated correction of HA-causing mutations, which encourage studies in mouse models to develop a personalized cure for large cohorts of patients through a single intervention., Competing Interests: Declaration of competing interests There are no competing interests to disclose., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

Objective: To review efficacy and safety data of valoctocogene roxaparvovec (Roctavian) and etranacogene dezaparavovec (Hemgenix), novel gene therapies for the treatment of the life-threatening bleeding disorders hemophilia A and B, respectively., Data Sources: A PubMed/Google Scholar search from inception through August 11, 2023 was conducted using the following keywords: gene therapy , hemophilia A , hemophilia B , etranacogene dezaparavovec , valoctocogene roxaparvovec , and bleeding., Study Selection and Data Extraction: Data, including phase 1 to 3 clinical trials (non-comparator), were obtained from primary literature and package inserts. These reports evaluated clinical pharmacology, efficacy, safety, adverse events, warnings, and precautions., Data Synthesis: Valoctocogene phase 3 study in males (n = 134): 87% had factor VIII (FVIII) levels that at least met criteria for mild hemophilia. Etranacogene phase 3 study in males (n = 54): within 3 weeks of infusion, mean factor IX (FIX) levels had reached 26.8 IU/dL. Both therapies provided clinically and statistically significant decreases in bleeding events and prophylactic factor infusions. Most common adverse event was elevations in liver function tests that were treated with glucocorticoids., Relevance to Patient Care and Clinical Practice in Comparison With Existing Drugs: The endogenous production of clotting factors mimics physiological production while decreasing morbidity and mortality related to bleeding events similar to the effects of existing replacement strategies. Gene therapy was also shown to increase patient quality of life., Conclusion: Valoctocogene and etranacogene provide another treatment for selected patients with hemophilia. Treatment for the patient with hemophilia (gene therapy vs replacement strategy) must be personalized as new clinical data are published being cognizant of drug affordability., Competing Interests: Declaration of Conflicting InterestsThe authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Hemophilia A (HA) is an X-linked recessive bleeding disorder caused by mutations in the F8 gene, resulting in deficient or dysfunctional factor VIII (FVIII). This study aimed to characterize the mutational profile of HA in Romanian patients using next-generation sequencing (NGS) and multiplex ligation-dependent probe amplification (MLPA). A total of 107 patients were analyzed, revealing pathogenic or likely pathogenic variants in 96.3% of cases. The identified mutations included missense (30.5%), nonsense (9.1%), small deletions (6.4%), small insertions (2.1%), splice-site variants (4.3%), large deletions (1.6%), and large duplications (1.1%). Large intron inversion was previously found in 37.5% of the patients. Novel variants accounted for 21.5% of identified mutations, expanding the spectrum of F8 variants in this population. This study underscores the genetic heterogeneity of HA and provides insights into genotype-phenotype correlations, aiding in clinical management and prenatal diagnosis.

Background: Exploring the expression of X linked disorders like haemophilia A (HA) in females involves understanding the balance achieved through X chromosome inactivation (XCI). Skewed XCI (SXCI) may be involved in symptomatic HA carriers. We aimed to develop an approach for dissecting the specific cause of SXCI and verify its value in HA., Methods: A family involving three females (two symptomatic with severe/moderate HA: I.2, the mother, and II.1, the daughter; one asymptomatic: II.2) and two related affected males (I.1, the father and I.3, the maternal uncle) was studied. The genetic analysis included F8 mutational screening, multiplex ligation-dependent probe amplification, SNP microarray, whole exome sequencing (WES) and Sanger sequencing. XCI patterns were assessed in ectoderm/endoderm and mesoderm-derived tissues using AR -based and RP2 -based systems., Results: The comprehensive family analysis identifies I.2 female patient as a heterozygous carrier of F8 :p.(Ser1414Ter) excluding copy number variations. A consistent XCI pattern of 99.5% across various tissues was observed. A comprehensive filtering algorithm for WES data was designed, developed and applied to I.2. A Gly58Arg missense variant in VMA21 was revealed as the cause for SXCI.Each step of the variant filtering system takes advantage of publicly available genomic databases, non-SXCI controls and case-specific molecular data, and aligns with established concepts in the theoretical background of SXCI., Conclusion: This study acts as a proof of concept for our genomic filtering algorithm's clinical utility in analysing X linked disorders. Our findings clarify the molecular aspects of SXCI and improve genetic diagnostics and counselling for families with X linked diseases like HA., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2024. No commercial re-use. See rights and permissions. Published by BMJ.)

One of the well-known X-linked genetic disorders is hemophilia, which could be hemophilia A as a result of a mutation in the F8 (factor VIII) gene or hemophilia B as a result of a mutation in the F9 (factor IX) gene, leading to insufficient levels of the proteins essential for blood coagulation cascade. In patients with severe hemophilia, factor VIII or factor IX activities in the blood plasma are considerably low, estimated to be less than 1%. This is responsible for spontaneous or post-traumatic bleeding episodes, or both, leading to disease complications and death. Current treatment of hemophilia relies on the prevention of bleeding, which consists of expensive lifelong replacement infusion therapy of blood plasma clotting factors, their recombinant versions, or therapy with recombinant monoclonal antibodies. Recently emerged gene therapy approaches may be a potential game changer that could reshape the therapeutic outcomes of hemophilia A or B using a one-off vector in vivo delivery and aim to achieve long-term endogenous expression of factor VIII or IX. This review examines both traditional approaches to the treatment of hemophilia and modern methods, primarily focusing on gene therapy, to update knowledge in this area. Recent technological advances and gene therapeutics in the pipeline are critically reviewed and summarized. We consider gene therapy to be the most promising method as it may overcome the problems associated with more traditional treatments, such as the need for constant and expensive infusions and the presence of an immune response to the antibody drugs used to treat hemophilia.

Most invasive dental procedures elicit some degree of bleeding which ultimately leads to clotting and eventual hemostasis. However, patients with inherited coagulation disorders may exhibit prolonged or, in some cases, excessive bleeding requiring multiple perioperative interventions. Von Willebrand disease is the most common inherited coagulopathy and often manifests via easy bruising, epistaxis, or prolonged bleeding. Hemophilia A (factor VII) and B (factor IX) are factor deficiencies that are clinically indistinguishable and managed according to severity and the required dental treatment. Other coagulopathies are rare (ie, inheritance is autosomal recessive) and may only become evident in homozygotes or compound heterozygotes. Current lab values and medical consultation with the patient's hematologist are imperative prior to rendering invasive dental treatment. There are a myriad of sedation and general anesthesia considerations, including risks for epistaxis with nasal instrumentation and bruising with improper patient positioning. Preoperative treatment with desmopressin or factor replacement may be required and generally should facilitate normal hemostasis. Additional therapies should be considered to help ensure adequate postoperative hemostasis, including pressure dressings, resorbable clotting materials, laser therapy, and oral rinses.

Gene transfer therapies utilizing adeno-associated virus (AAV) vectors involve a complex drug design with multiple components that may impact immunogenicity. Valoctocogene roxaparvovec is an AAV serotype 5 (AAV5)-vectored gene therapy for the treatment of hemophilia A that encodes a B-domain-deleted human factor VIII (FVIII) protein controlled by a hepatocyte-selective promoter. Following previous results from the first-in-human phase 1/2 clinical trial, we assessed AAV5-capsid- and transgene-derived FVIII-specific immune responses with 2 years of follow-up data from GENEr8-1, a phase 3, single-arm, open-label study in 134 adult men with severe hemophilia A. No FVIII inhibitors were detected following administration of valoctocogene roxaparvovec. Immune responses were predominantly directed toward the AAV5 capsid, with all participants developing durable anti-AAV5 antibodies. Cellular immune responses specific for the AAV5 capsid were detected in most participants by interferon-γ enzyme-linked immunosorbent spot assay 2 weeks following dose administration and declined or reverted to negative over the first 52 weeks. These responses were weakly correlated with alanine aminotransferase elevations and showed no association with changes in FVIII activity. FVIII-specific cellular immune responses were less frequent and more sporadic compared with those specific for AAV5 and showed no association with safety or efficacy parameters., Competing Interests: Declaration of interests All authors are current or former employees and shareholders of BioMarin Pharmaceutical Inc. BioMarin Pharmaceutical Inc. has patents and/or patent applications covering ROCTAVIAN (valoctocogene roxaparvovec) and methods for treating hemophilia A., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

Background: Hemophilia A (HA) is an X-linked congenital bleeding disorder, which leads to deficiency of clotting factor (F) VIII. It mostly affects males, and females are considered carriers. However, it is now recognized that variants of F8 in females can result in HA. Nonetheless, most females go undiagnosed and untreated for HA, and their bleeding complications are attributed to other causes. Predicting the severity of HA for female patients can provide valuable insights for treating the conditions associated with the disease, such as heavy bleeding., Objectives: To predict the severity of HA based on F8 genotype using a machine learning (ML) approach., Methods: Using multiple datasets of variants in the F8 and disease severity from various repositories, we derived the sequence for the FVIII protein. Using the derived sequences, we used ML models to predict the severity of HA in female patients., Results: Utilizing different classification models, we highlight the validity of the datasets and our approach with predictive F1 scores of 0.88, 0.99, 0.93, 0.99, and 0.90 for all the validation sets., Conclusion: Although with some limitations, ML-based approaches demonstrated the successful prediction of disease severity in female HA patients based on variants in the F8. This study confirms previous research findings that ML can help predict the severity of hemophilia. These results can be valuable for future studies in achieving better treatment and clinical outcomes for female patients with HA, which is an urgent unmet need., (Copyright © 2024 International Society on Thrombosis and Haemostasis. All rights reserved.)

Background: Valoctocogene roxaparvovec transfers a human factor (F)VIII coding sequence into hepatocytes of people with severe hemophilia A to provide bleeding protection., Objectives: To present 3-year efficacy and safety in the multicenter, open-label, single-arm, phase 3 GENEr8-1 trial., Methods: GENEr8-1 enrolled 134 adult males with severe hemophilia A who were receiving FVIII prophylaxis. Efficacy endpoints included annualized bleeding rate, annualized FVIII utilization, FVIII activity (chromogenic substrate assay; imputed as 1 IU/dL at baseline and 0 IU/dL after discontinuation), and the Haemophilia-Specific Quality of Life Questionnaire for Adults. Safety was assessed by adverse events (AEs)., Results: At week 156, 131 of 134 participants remained in the study; overall, 17 of 134 resumed prophylaxis. Mean annualized bleeding rate for treated bleeds decreased from 4.8 (SD, 6.5) bleeds/y at baseline to 0.8 (SD, 2.3; P < .0001) bleeds/y after prophylaxis (prophylaxis cessation to last follow-up) and 0.97 (SD, 3.48) bleeds/y during year 3. Annualized FVIII utilization decreased 96.8% from baseline after prophylaxis and 94.2% during year 3. At week 156, mean and median FVIII activity were 18.4 (SD, 30.8) and 8.3 IU/dL, respectively. FVIII activity decrease was lower between years 2 and 3 than between years 1 and 2. At the end of year 3, clinically meaningful improvements in the Haemophilia-Specific Quality of Life Questionnaire for Adults Total Score were observed (mean change from baseline, 6.6; 95% CI, 4.24-8.87; P < .0001). Mild alanine aminotransferase elevations remained the most common AE during year 3 (23.7% of participants). A serious AE of B-cell acute lymphoblastic leukemia was considered unrelated to treatment., Conclusion: Hemostatic efficacy was maintained, and safety remained unchanged from previous years., Competing Interests: Declaration of competing interests M.C.O. has participated in advisory boards for Bayer, BioMarin Pharmaceutical Inc, Pfizer, Sanofi, and Takeda and received honoraria from BioMarin Pharmaceutical Inc, Biotest, Novo Nordisk, Pfizer, Roche, Takeda, and Sanofi. P.R. has received grant/travel support from CSL Behring, Sobi, and Takeda and advisory honoraria from Idogen, Pfizer, Sigilon, and Sobi. E.S. has received travel grants from CSL Behring and Novo Nordisk. D.V.Q. has served on advisory boards and speakers bureaus or as a consultant for Bayer, BioMarin Pharmaceutical Inc, Genentech, Novo Nordisk, Octapharma, Sanofi, Takeda, and uniQure. A.D.L. has served as an investigator for BioMarin Pharmaceutical Inc and Pfizer. S.W.P. has served as a consultant for ApcinteX, Bayer, BioMarin Pharmaceutical Inc, CSL Behring, Equilibra Bioscience, GeneVentiv, HEMA Biologics, LFB, Novo Nordisk, Pfizer, Regeneron, Roche, Sanofi, Siemens, Spark, Takeda, and uniQure. G.L. has received honoraria for participating in educational events from Alexion, LEO Pharma, Novartis, Novo Nordisk, Sanofi, Sobi, and Takeda and consulting fees from UCB. G.K. has received grant funding from Genentech and Pfizer and served on advisory boards or as a consultant for Bayer, BioMarin Pharmaceutical Inc, Genentech, Novo Nordisk, Sanofi, Sobi, Spark, and Takeda. M.T.R. has served as an investigator for Bayer and BioMarin Pharmaceutical Inc and served on advisory boards or speakers bureaus for Bayer, CSL Behring, Genentech, HEMA Biologics, Novo Nordisk, Sanofi, and Takeda. M.W. has served as a consultant for Bayer, BioMarin Pharmaceutical Inc, Bioverativ, Catalyst, CSL Behring, Genentech, HEMA Biologics, and Novo Nordisk. A.v.D. has received research funding from Pfizer and Sanofi, is a cofounder and board member of Hematherix Inc, and served as a consultant for ASC Therapeutics, BioMarin Pharmaceutical Inc, CSL Behring, Genentech, Regeneron, Sanofi, Takeda, and uniQure. R.K. has received grants from Bayer, CSL Behring, and LEO Pharma; consulting fees from Bayer, BioMarin Pharmaceutical Inc, CSL Behring, Novo Nordisk, Octapharma, Pfizer, Roche/Chugai, Sanofi, Sobi, and Takeda; and payment of honoraria for lectures, presentations, speakers bureaus, manuscript writing, or educational events from Bayer, BioMarin Pharmaceutical Inc, Biotest, CSL Behring, Daiichi Sankyo, Grifols, LEO Pharma, Novo Nordisk, Octapharma, Pfizer, Roche/Chugai, Sanofi, Sobi, Shire/Takeda, and uniQure. S.S. has received speaking, educational, or travel honoraria from CSL Behring, Pfizer, Roche, Sobi, and Takeda. H.C. has served as a consultant for BioMarin Pharmaceutical Inc, Novo Nordisk, Roche, and Sobi. A.L.D has received research funding from BioMarin Pharmaceutical Inc, Novo Nordisk, Sanofi, and Takeda; served as a consultant for CSL Behring, Roche, and uniQure; and is a board member of the National Hemophilia Foundation and World Federation of Hemophilia USA. J.O. has received research funding from Bayer, Biotest, CSL Behring, Octapharma, Pfizer, Swedish Orphan Biovitrum, and Takeda and consultancy, speakers bureau, honoraria, scientific advisory board, and travel expenses from Bayer, Biogen Idec, BioMarin Pharmaceutical Inc, Biotest, Chugai, CSL Behring, Freeline, Grifols, LFB, Novo Nordisk, Octapharma, Pfizer, Roche, Sanofi, Spark Therapeutics, Swedish Orphan Biovitrum, and Takeda. F.P. has served as a consultant for BioMarin Pharmaceutical Inc, Grifols, Roche, Sanofi, Sobi, and Takeda. C.M.M. has received research funding from CSL Behring, Grifols, and Takeda and has served as a speaker or consultant for CSL Behring, LFB Pharma, Novo Nordisk, Octapharma, Takeda, and Sobi. D.O., H.Y., E.D.-A., and T.M.R. are employees and shareholders of BioMarin Pharmaceutical Inc. J.Mahlangu has received research funding from BioMarin Pharmaceutical Inc, Catalyst, Roche, Novo Nordisk, Pfizer, Sandoz, Sanofi, and Spark Therapeutics. B.M., J. Mason, and S.-C.C. have no conflicts to declare., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

The aim of this study is to characterize zebrafish coagulation cofactors fviii and fv mutant fish and assess if they phenocopy classical hemophilia A and factor V deficiency in humans. The embryos from fviii and fv zebrafish heterozygote mutants generated by ENU mutagenesis were purchased from the ZIRC repository. They were reared to adulthood and genotyped. The heterozygote male and female were crossed to get homozygote, heterozygote, and wild-type fish. Functional kinetic coagulation assays and bleeding assays were performed on normal and mutant adult fish, and venous laser injury assays were performed on the larvae. The DNA from fviii and fv mutants were sequenced to confirm if they have a premature stop codon in exon 19, and in exon 2, respectively, and in both mutants, the amino acid glutamine is replaced with a stop codon. Homozygous and heterozygous 5 days post fertilization (dpf) larvae for fviii and fv deficient mutants exhibited prolonged time to occlusion after venous laser injury compared to wild-type controls. The homozygous and heterozygous fviii adult mutants showed modest bleeding and delayed fibrin formation in the kinetic partial thromboplastin time (kPTT) assay with their plasma. fv homozygous larvae had poor survival beyond 12 dpf. However, heterozygous fv mutants exhibited heavy bleeding and prolonged fibrin formation in the kPTT and kPT assay compared with wild-type siblings. Our characterization showed fviii and fv mutants from ZIRC phenocopied to a considerable extent classical hemophilia A and factor V deficiency in humans, respectively. These models should be useful in studying and developing novel drugs that reverse the phenotype and in generating suppressor mutations to identify novel factors that compensate for these deficiencies., (Copyright © 2024 Wolters Kluwer Health, Inc. All rights reserved.)

Abstract: Gene therapy using adeno-associated virus (AAV) vectors is a promising approach for the treatment of monogenic disorders. Long-term multiyear transgene expression has been demonstrated in animal models and clinical studies. Nevertheless, uncertainties remain concerning the nature of AAV vector persistence and whether there is a potential for genotoxicity. Here, we describe the mechanisms of AAV vector persistence in the liver of a severe hemophilia A dog model (male = 4, hemizygous; and female = 4, homozygous), more than a decade after portal vein delivery. The predominant vector form was nonintegrated episomal structures with levels correlating with long-term transgene expression. Random integration was seen in all samples (median frequency, 9.3e-4 sites per cell), with small numbers of nonrandom common integration sites associated with open chromatin. No full-length integrated vectors were found, supporting predominant episomal vector-mediated long-term transgene expression. Despite integration, this was not associated with oncogene upregulation or histopathological evidence of tumorigenesis. These findings support the long-term safety of this therapeutic modality., (© 2024 American Society of Hematology. Published by Elsevier Inc. All rights are reserved, including those for text and data mining, AI training, and similar technologies.)

Lentiviral vectors (LV) are efficient vehicles for in vivo gene delivery to the liver. LV integration into the chromatin of target cells ensures their transmission upon proliferation, thus allowing potentially life-long gene therapy following a single administration, even to young individuals. The glycoprotein of the vesicular stomatitis virus (VSV.G) is widely used to pseudotype LV, as it confers broad tropism and high stability. The baculovirus-derived GP64 envelope protein has been proposed as an alternative for in vivo liver-directed gene therapy. Here, we perform a detailed comparison of VSV.G- and GP64-pseudotyped LV in vitro and in vivo. We report that VSV.G-LV transduced hepatocytes better than GP64-LV, however the latter showed improved transduction of liver sinusoidal endothelial cells (LSEC). Combining GP64-pseudotyping with the high surface content of the phagocytosis inhibitor CD47 further enhanced LSEC transduction. Coagulation factor VIII (FVIII), the gene mutated in hemophilia A, is naturally expressed by LSEC, thus we exploited GP64-LV to deliver a FVIII transgene under the control of the endogenous FVIII promoter and achieved therapeutic amounts of FVIII and correction of hemophilia A mice., (© 2024. The Author(s).)

Background: No F8 genetic abnormality is detected in approximately 1% to 2% of patients with severe hemophilia A (HA) using conventional genetic approaches. In these patients, deep intronic variation or F8 disrupting genomic rearrangement could be causal., Objectives: The study aimed to identify the causal variation in families with a history of severe HA for whom genetic investigations failed., Methods: We performed whole F8 gene sequencing in 8 propositi. Genomic rearrangements were confirmed by Sanger sequencing of breakpoint junctions and/or quantitative polymerase chain reaction., Results: A structural variant disrupting F8 was found in each propositus, so that all the 815 families with a history of severe HA registered in our laboratory received a conclusive genetic diagnosis. These structural variants consisted of 3 balanced inversions, 3 large insertions of gained regions, and 1 retrotransposition of a mobile element. The 3 inversions were 105 Mb, 1.97 Mb, and 0.362 Mb in size. Among the insertions of gained regions, one corresponded to the insertion of a 34 kb gained region from chromosome 6q27 in F8 intron 6, another was the insertion of a 447 kb duplicated region from chromosome 9p22.1 in F8 intron 14, and the last one was the insertion of an Xq28 349 kb gained in F8 intron 5., Conclusion: All the genetically unsolved cases of severe HA in this cohort were due to structural variants disrupting F8. This study highlights the effectiveness of whole F8 sequencing to improve the molecular diagnosis of HA when the conventional approach fails., Competing Interests: Declaration of competing interests There are no competing interests to disclose., (Copyright © 2024 International Society on Thrombosis and Haemostasis. Published by Elsevier Inc. All rights reserved.)

Gene therapy represents a significant potential to revolutionize the field of hematology with applications in correcting genetic mutations, generating cell lines and animal models, and improving the feasibility and efficacy of cancer immunotherapy. Compared to different genetic engineering tools, clustered regularly interspaced short palindromic repeats (CRISPR) CRISPR-associated protein 9 (Cas9) emerged as an effective and versatile genetic editor with the ability to precisely modify the genome. The applications of genetic engineering in various hematological disorders have shown encouraging results. Monogenic hematological disorders can conceivably be corrected with single gene modification. Through the use of CRISPR-CAS9, restoration of functional red blood cells and hemostasis factors were successfully attained in sickle cell anemia, beta-thalassemia, and hemophilia disorders. Our understanding of hemato-oncology has been advanced via CRIPSR-CAS9 technology. CRISPR-CAS9 aided to build a platform of mutated genes responsible for cell survival and proliferation in leukemia. Therapeutic application of CRISPR-CAS9 when combined with chimeric antigen receptor (CAR) T cell therapy in multiple myeloma and acute lymphoblastic leukemia was feasible with attenuation of CAR T cell therapy pitfalls. Our review outlines the latest literature on the utilization of CRISPR-Cas9 in the treatment of beta-hemoglobinopathies and hemophilia disorders. We present the strategies that were employed and the findings of preclinical and clinical trials. Also, the review will discuss gene engineering in the field of hemato-oncology as a proper tool to facilitate and overcome the drawbacks of chimeric antigen receptor T cell therapy (CAR-T)., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Haemophilic arthropathy (HA), a common comorbidity in haemophilic patients leads to joint pain, deformity and reduced quality of life. We have recently demonstrated that a long non-coding RNA, Neat1 as a primary regulator of matrix metalloproteinase (MMP) 3 and MMP13 activity, and its induction in the target joint has a deteriorating effect on articular cartilage. In the present study, we administered an Adeno-associated virus (AAV) 5 vector carrying an short hairpin (sh)RNA to Neat1 via intra-articular injection alone or in conjunction with systemic administration of a capsid-modified AAV8 (K31Q) vector carrying F8 gene (F8-BDD-V3) to study its impact on HA. AAV8K31Q-F8 vector administration at low dose, led to an increase in FVIII activity (16%-28%) in treated mice. We further observed a significant knockdown of Neat1 (~40 fold vs. untreated injured joint, p = 0.005) in joint tissue of treated mice and a downregulation of chondrodegenerative enzymes, MMP3, MMP13 and the inflammatory mediator- cPLA2, in mice receiving combination therapy. These data demonstrate that AAV mediated Neat1 knockdown in combination with F8 gene augmentation can potentially impact mediators of haemophilic joint disease., (© 2024 The Author(s). Journal of Cellular and Molecular Medicine published by Foundation for Cellular and Molecular Medicine and John Wiley & Sons Ltd.)

Recurrent joint bleeding in hemophilia patients frequently causes hemophilic arthropathy (HA). Drastic degradation of cartilage is a major characteristic of HA, but its pathological mechanisms has not yet been clarified. In HA cartilages, we found server matrix degradation and increased expression of DNA methyltransferase proteins. We thus performed genome-wide DNA methylation analysis on human HA (N=5) and osteoarthritis (OA) (N=5) articular cartilages, and identified 1228 differentially methylated regions (DMRs) associated with HA. Functional enrichment analyses revealed the association between DMR genes (DMGs) and extracellular matrix (ECM) organization. Among these DMGs, Tenascin XB (TNXB) expression was down-regulated in human and mouse HA cartilages. The loss of Tnxb in F8 -/- mouse cartilage provided a disease-promoting role in HA by augmenting cartilage degeneration and subchondral bone loss. Tnxb knockdown also promoted chondrocyte apoptosis and inhibited phosphorylation of AKT. Importantly, AKT agonist showed chondroprotective effects following Tnxb knockdown. Together, our findings indicate that exposure of cartilage to blood leads to alterations in DNA methylation, which is functionally related to ECM homeostasis, and further demonstrate a critical role of TNXB in HA cartilage degeneration by activating AKT signaling. These mechanistic insights allow development of potentially new strategies for HA cartilage protection., Competing Interests: JC, QZ, XW, RX, WW, YH, QS, WY, PW, PT, HJ No competing interests declared, DC Reviewing editor, eLife, (© 2024, Chen, Zeng et al.)

Background: Adeno-associated virus (AAV)-based gene therapy for haemophilia has advanced substantially in the last 13 years; recently, three products have received approvals from regulatory authorities. Although the impact on quality of life seems promising, some limitations remain, such as the presence of pre-existing anti-AAV neutralising antibodies and the occurrence of hepatotoxicity. This review follows the CSL Behring-sponsored symposium at the 27th Congress of the European Hematology Association (EHA) 2022 that examined the haemophilia gene therapy process from a 360-degree multidisciplinary perspective. Here, the faculty (haematologist, nurse and haemophilia patient) summarised their own viewpoints from the symposium, with the aim of highlighting the key considerations required to engage with gene therapy effectively, for both patients and providers, as well as the importance of multidisciplinary collaboration, including with industry., Results: When considering these new therapies, patients face a complex decision-making process, which includes whether gene therapy is right for them at their current stage of life. The authors agreed that collaboration and tailored education across the multidisciplinary team (including patients and their carers/families), starting early in the process and continuing throughout the long-term follow-up period, is key for the success of gene therapy. Additionally, patient expectations, which may surround eligibility, follow-up requirements and treatment outcomes, should be continually explored. During these ongoing discussions, transparent communication of the unknown factors, such as anticipated clotting factor levels, long-term factor expression and safety, and psychological changes, is critical. To ensure efficiency and comprehensiveness, clearly‑defined protocols should outline the whole process, which should include the recording and management of long-term effects., Conclusion: In order to engage effectively, both patients and providers should be familiar with these key considerations prior to their involvement with the haemophilia gene therapy process. The future after the approval of haemophilia gene therapies remains to be seen and real-world evidence is eagerly awaited., (© 2024. The Author(s).)

Medical therapies for hemophilia patients over the past 60 years have included several blessings and a curse. The long-sought cure with gene therapy may have finally arrived. Unfortunately, preclinical animal models are now raising concerns for genotoxicity with gene therapy. Although no cancers have been detected in humans, it may be a few decades before we know if gene therapy for hemophilia is another blessing, or another curse., Competing Interests: Disclosure No financial disclosures reported. Artificial intelligence was not used in the study, research, preparation, or writing of this manuscript., (Copyright 2024 by the Missouri State Medical Association.)

Aim: To characterise non-severe haemophilia A (HA) patients enrolled on the Australian Bleeding Disorders Registry (ABDR) treated through a state-wide Haemophilia Treatment Centre (HTC) with respect to their mutational profile, inhibitor risk and health-care burden., Method: We conducted a single-centre observational study of all non-severe HA patients treated at the Alfred Health HTC registered on the ABDR as of the 26th July 2023. Data were extracted from the ABDR and electronic medical record (EMR) regarding demographics, severity, genetic testing, treatment, inhibitors, bleeding events and procedures. Inhibitor risk was calculated as a function of exposure days (EDs) of FVIII replacement., Results: There were 289 non-severe HA patients treated at the Alfred HTC registered on the ABDR as of July 2023, all of whom were adult patients aged > 18 years old. Genotyping had been performed in 228/289 (78.9%). Of the inhibitor analysis population, 14/193 (7.3%) had an inhibitor. The cumulative incidence of inhibitor development at 75 EDs was 31% (95% CI 13%-46%). The median cost of bypassing agents per inhibitor patient was $57,087.50/year., Conclusion: These results demonstrate a relatively high inhibitor prevalence and incidence risk in non-severe HA compared to previously published work, although this may partly reflect a smaller population size. High rates of genotyping have allowed representative mutational characterisation. The burden of care imposed by non-severe HA in terms of bleeding events, procedures and bypassing agent cost is larger than expected, particularly within the inhibitor population., (© 2024 The Authors. Haemophilia published by John Wiley & Sons Ltd.)

Independent data collection is crucial in addressing the challenges associated with gene therapy for hemophilia, which is a promising treatment option but requires careful monitoring and management of short-term and potential long-term safety concerns. The International Society on Thrombosis and Haemostasis has identified a minimum efficacy and safety data set included in the World Federation of Hemophilia Gene Therapy Registry that should be collected on a national basis at specific time points for each patient who has been treated with the gene therapy products. This Gene Therapy Minimum Data Set (GT-MDS) was developed to facilitate data collection and to ensure capturing the most relevant data and most known and unknown safety and efficacy parameters recently cited by the European Medicine Agencies. The concept of assembling a minimum data set is not about creating a new data set but rather about identifying a subset of critical and essential topics that should always be included. The GT-MDS is structured into 3 sections and comprises an abridged list of 6 topics during routine gene therapy follow-up, keeping the number of data points low but allowing for rapid and independent data evaluation. The World Federation of Hemophilia Gene Therapy Registry data set, developed by the World Federation of Hemophilia, the International Society on Thrombosis and Haemostasis, and other organizations, including industry partners in 2020, is comprehensive. The GT-MDS reports the minimum relevant information that should not be lost and is mandatory to be collected for all patients who undergo gene therapy. Therefore, the implementation of the gene therapy registry and the minimum data set empowers and enhances data collection at a global level., Competing Interests: Declaration of competing interests W.M.: Bayer, BioMarin, Biotest, CSL Behring, Chugai, Freeline, LFB, Novo Nordisk, Octapharma, Pfizer, Regeneron, Roche, Sanofi, Sigilon, Sobi, Takeda/Shire, uniQure. B.K.: Grant/research support from CSL Behring, Pfizer, Sanofi, Spark Therapeutics, Takeda, and uniQure; Consultant fees from Be Biopharma, BioMarin, Regeneron, Pfizer, Sanofi; Leadership roles: World Federation for Hemophilia, Foundation for Women and Girls with Blood Disorders. P.C.: Bayer, Boehringer Ingelheim, CSL Behring, Chugai, Freeline, NovoNordisk, Pfizer, Roche, Sanofi, Spark, Sobi, and Takeda. R.K.: Grants from Bayer; consulting fees from BioMarin, Pfizer; honoraria for lectures from Pfizer; participation on a data safety monitoring board or advisory board: BioMarin, Pfizer. F.L.: Grant/research support from CSL Behring, Takeda, uniQure, Sobi; consultant fees from uniQure, Sobi, BioMarin; Research support from CLE Behring, Takeda, Sobi, uniQure. J.M.: Grant/research support from BioMarin, Novartis, Novo Nordisk, Pfizer, F. Hoffmann-La Roche Ltd, Sanofi, Spark Therapeutics, and uniQure; consultant fees for BioMarin, Novo Nordisk, F. Hoffmann-La Roche Ltd, Sanofi, Spark Therapeutics and Takeda; Speaker bureau fees from Novo Nordisk, Pfizer, F. Hoffmann-La Roche Ltd, Sanofi, Takeda, WFH, and ISTH. M.M.: Leadership roles: EAHAD council member 2018-2022. ISTH council member 2018-2022. S.W.P.: Consulting fees from Apcintex, ASC Therapeutics, Bayer, BioMarin, CSL Behring, Equilibra Bioscience, HEMA Biologics, Freeline, LFB, Novo Nordisk, Pfizer, Regeneron/Intellia, Roche/Genentech, Sanofi, Takeda, Spark Therapeutics, and uniQure; Scientific Advisory Board member: Equilibra Bioscience, GeneVentiv. G.P.: consultant to ASC Therapeutics, BioMarin, Pfizer, Regeneron, and Spark Therapeutics and on the scientific advisory boards of Be Bio, Frontera, and Metagenomic. A.S.: speaker: Novo Nordisk, Roche, Sanofi, Takeda, Octapharma, and BioMarin; advisory board: Novo Nordisk, Roche, Sanofi, Takeda, Pfizer, BioMarin, and Spark; research grant: Roche, Novo Nordisk, Sanofi, and Pfizer. J.V.: no personal fees. F.P.: consulting fees from CSL Behring, Biomarin, Roche, Sobi, and Sanofi; payment or honoraria for lectures: Takeda and Spark., (Copyright © 2024 International Society on Thrombosis and Haemostasis. All rights reserved.)

The remarkable advance in gene editing technology presents unparalleled opportunities for transforming medicine and finding cures for hereditary diseases. Human trials of clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein-9 nuclease (Cas9)-based therapeutics have demonstrated promising results in disrupting or deleting target sequences to treat specific diseases. However, the potential of targeted gene insertion approaches, which offer distinct advantages over disruption/deletion methods, remains largely unexplored in human trials due to intricate technical obstacles and safety concerns. This paper reviews the recent advances in preclinical studies demonstrating in vivo targeted gene insertion for therapeutic benefits, targeting somatic solid tissues through systemic delivery. With a specific emphasis on hemophilia as a prominent disease model, we highlight advancements in insertion strategies, including considerations of DNA repair pathways, targeting site selection, and donor design. Furthermore, we discuss the complex challenges and recent breakthroughs that offer valuable insights for progressing towards clinical trials., (© 2024. The Author(s).)

Hemophilia is a genetic disorder that is caused by mutations in coagulation factor VIII (hemophilia A) or IX (hemophilia B) genes resulting in blood clotting disorders. Despite advances in therapies, such as recombinant proteins and products with extended half-lives, the treatment of hemophilia still faces two major limitations: the short duration of therapeutic effect and production of neutralizing antibodies against clotting factors (inhibitor). To overcome these limitations, new hemophilia treatment strategies have been established such as gene therapy, bispecific antibody, and rebalancing therapy. Although these strategies have shown promising results, it is difficult to achieve a permanent therapeutic effect. Advances in the clustered regularly interspaced short palindromic repeat (CRISPR) technology have allowed sustainable treatment by correcting mutated genes. Since genome editing generates irreversible changes in host genome, safety must be ensured by delivering target organs. Therefore, the delivery tool of the CRISPR system is crucial for safe, accurate, and efficient genome editing. Recently, non-viral vector lipid nanoparticles (LNPs) have emerged as safer tools for delivering CRISPR systems than other viral vectors. Several previous hemophilia pre-clinical studies using LNP-CRISPR showed that sufficient and sustainable therapeutic effects, which means that LNP-CRISPR-mediated genome-editing therapy can be a valid option for the treatment of hemophilia. In this paper, we summarize the latest advancements in the successful treatment of hemophilia and the potential of CRISPR-mediated genome-editing therapy using LNPs., (© 2024. The Author(s).)