scholarly journals Gene therapy for haemophilia: a very modern success story

2015 ◽  
Vol 2 (2) ◽  
pp. 26-28
Author(s):  
Amit Nathwani
Keyword(s):  
Gene Therapy ◽  
Clotting Factor ◽  
Haemophilia A ◽  
Single Administration ◽  
Success Story ◽  
Spontaneous Bleeding ◽  
Bleeding Episodes ◽  
Paradigm Shifting

Abstract AAV-mediated gene therapy has the potential to be paradigm shifting as a treatment for haemophilia. A single administration of AAV vector can result in safe and consistent long-term expression of transgene (>5 years), reduction in spontaneous bleeding episodes, reduction in clotting factor usage and an improvement in quality of life. There is huge commercial interest in this approach, with the expectation that an AAV gene therapy product for haemophilia B will be licensed by 2020.

scholarly journals Gene therapy for hemophilia

Hematology ◽  
2019 ◽  
Vol 2019 (1) ◽  
pp. 1-8 ◽  
Author(s):  
Amit C. Nathwani
Keyword(s):  
Gene Therapy ◽  
Hemophilia A ◽  
Phase 1 ◽  
Substantial Reduction ◽  
Factor Ix ◽  
Clotting Factor ◽  
High Dose ◽  
Single Administration ◽  
Spontaneous Bleeding ◽  
Endogenous Expression

Abstract Gene therapy offers the potential for a cure for patients with hemophilia by establishing continuous endogenous expression of factor VIII or factor IX (FIX) following transfer of a functional gene to replace the hemophilic patient’s own defective gene. The hemophilias are ideally suited for gene therapy because a small increment in blood factor levels (≥5% of normal) is associated with significant amelioration of bleeding phenotype in severely affected patients. In 2011, the St. Jude/UCL phase 1/2 trial was the first to provide clear evidence of a stable dose-dependent increase in FIX levels in patients with severe hemophilia B following a single administration of adeno-associated viral (AAV) vectors. Transgenic FIX expression has remained stable at ∼5% of normal in the high-dose cohort over a 7-year follow-up period, resulting in a substantial reduction in spontaneous bleeding and FIX protein usage without toxicity. This study has been followed by unparalleled advances in gene therapy for hemophilia A and B, leading to clotting factor activity approaching normal or near-normal levels associated with a “zero bleed rates” in previously severely affected patients following a single administration of AAV vectors. Thus, AAV gene therapies are likely to alter the treatment paradigm for hemophilia A and B. This review explores recent progress and the remaining limitations that need to be overcome for wider availability of this novel treatment of inherited bleeding disorders.

scholarly journals Gene therapy for haemophilia: an update on progress in clinical trials

2015 ◽  
Vol 2 (1) ◽  
pp. 3-5
Author(s):  
Sarah Gilgunn
Keyword(s):  
Gene Therapy ◽  
Clinical Trials ◽  
Replacement Therapy ◽  
Viral Vector ◽  
Effective Means ◽  
Clotting Factor ◽  
Haemophilia A ◽  
Spontaneous Bleeding ◽  
Factor Gene ◽  
Highly Effective

Abstract Clotting factor replacement therapy has proven a highly effective means of treating haemophilia A and B. But treatment involves frequent and lifelong infusion of factor concentrates and is generally prophylactic rather than curative. It is also extremely expensive, associated with inhibitor formation and does not fully abolish the potential for spontaneous bleeding. Gene therapy offers a potential cure for haemophilia, with the possible continuous expression of a clotting factor gene following the administration of a viral vector carrying the appropriate gene. Recent clinical trials of gene therapy for haemophilia have proven positive in selected patients and new studies are underway.

scholarly journals Efficacy and safety of the drug Octofactor in prophylactic treatment in patients with severe haemophilia A

2018 ◽  
Vol 5 (3) ◽  
pp. 60-73 ◽  
Author(s):  
T. A. Andreeva ◽  
V. Yu. Zorenko ◽  
I. L. Davydkin ◽  
V. N. Konstantinova ◽  
O. E. Zalepukhina ◽  
...  
Keyword(s):  
Hemophilia A ◽  
Bleeding Episode ◽  
Coagulation Factor ◽  
Preventive Treatment ◽  
Haemophilia A ◽  
Severe Haemophilia ◽  
Efficacy And Safety ◽  
Spontaneous Bleeding ◽  
Bleeding Episodes ◽  
Blood Coagulation Factor Viii

Relevance.The development of a new recombinant blood coagulation factor VIII preparation is a promising step towards optimizing the treatment of hemophilia A. An introduction of a new medication into clinical practice precedes a clinical trials to evaluate the efficacy and safety.Materials and methods.The efficacy and safety of the domestic recombinant B-domain deleted blood coagulation factor VIII (FVIII) (moroctocog alfa, Octofactor®, JSC “GENERIUM”) were studied in the preventive treatment of 31 patients aged 21 to 52 years with severe haemophilia A. The Octofactor was administered in doses of 40 ± 5 IU/kg 3 times per week at intervals of at least 48 hours for 21 ± 1 weeks.Results.The efficacy of therapy was evaluated in 30 patients, since 1 patient refused to participate in the trial after the first injection of the study medication. There were registered 43 episodes of bleeding among 11 patients in the course of the preventive treatment with Octofactor. The average number of bleeding episodes was 1.4 ± 2.58. There were 43 bleeding episodes, 9 (20.9 %) of them were posttraumatic, 34 (79.1 %) of them were spontaneous. The average number of the spontaneous bleeding episodes (a major criterion of the efficacy) was 1.13 ± 2.19, which showed a low incidence of exacerbations of the hemorrhagic syndrome in the course of preventive treatment with Octofactor. Among all registered bleeding episodes there were 6 (14 %) mild episodes, 37 (86 %) moderate episodes. Among all spontaneous bleedings there were 6 mild episodes (17.6 %), 28 (82.4 %) moderate episodes. All posttraumatic bleedings were moderate. The vast majority (36, or 83.7 %) of bleeding episodes were stopped with administration of the Octofactor. The average number of administrations of the Octofactor for arresting 1 bleeding episode was 1.2 ± 0.56, for 1 spontaneous bleeding episode – 1.2 ± 0.59. On average, it was required to administer 3534.9 ± 2329.02 IU of the Octofactor to stop 1 episode of bleeding. In the vast majority of patients with severe hemophilia A (83.3–86.7 %),  the remaining activity FVIII was 1 % or more after the administration of the Octofactor in 48 hours. The total amount of the Octofactor, introduced for the prevention of bleeding, was 6,107,000 IU, to stop bleeding – 152,000 IU. The safety of therapy was evaluated in 31 patients. There were recorded 25 adverse events (AE) in 17 patients. Among them the laboratory ones prevailed in 23 (92 %) cases, which is not associated with the use of the trial medication. There were noted nausea and an unpleasant aftertaste in the mouth in 1 patient during the first administration of the Octofactor, and therefore he refused to continue to participate in the trial. Causality 2 AE with the study drug was regarded as definite. Such AE are expected and described in the instructions to the preparation. All AE were not serious and mild and resolved without outcomes. There were no presented thromboembolic events and immunogenic reactions.Conclusions.The obtained data testify to the efficacy and safety of the Octofactor both for preventive measures and for stopping bleeding in adult patients with severe hemophilia A.

The long-term course of factor VIII inhibitors in patients with congenital haemophilia A without immune tolerance induction

2011 ◽  
Vol 105 (01) ◽  
pp. 59-65 ◽  
Author(s):  
Camila Caram ◽  
Roberta Grazielle de Souza ◽  
Júlio Carepa de Sousa ◽  
Tatiana Araújo Pereira ◽  
Ana Maria do Amaral Cerqueira ◽  
...  
Keyword(s):  
Confidence Interval ◽  
Factor Viii ◽  
Immune Tolerance ◽  
Tolerance Induction ◽  
Clotting Factor ◽  
Haemophilia A ◽  
Immune Tolerance Induction ◽  
Inhibitor Titre ◽  
Very High

SummaryThe development of alloantibodies that inhibit or neutralise the function of factor VIII is considered the most serious complication of the treatment of congenital haemophilia A. In order to describe their course without immune tolerance induction (ITI), we documented data on all performed inhibitor tests with dates as well as on clotting factor infusions of all consecutive patients who were treated in our centre between 1993 and 2006. Patients were tested every 7.1 months (95% confidence interval [CI], 6.6–7.8). A ‘sustained negative inhibitor status’ was defined as consistent non-positive inhibitor measurements for two years or longer. A total of 60/486 (12%) patients tested had a positive inhibitor titre in two or more occasions. Most of the patients (56%) with a maximum inhibitor titre of < 5 Bethesda unit (BU)/ml (named “low titre inhibitor”) developed a sustained negative inhibitor status. Among patients with high (5–9.9 BU/ml) and very high (≥ 10 BU/ ml) inhibitor titres, the proportions were 50% and 3%, respectively. Our findings suggest that ITI might not be needed for all patients with non-transient inhibitors, especially when their maximum inhibitor titre is below 10 BU/ml. Further studies in countries where ITI is not available are needed to examine predictors of the natural sustained negative inhibitor status.

scholarly journals Dental management of patients with haemophilia in the era of recombinant treatments: increased efficacy and decreased clinical risk

2019 ◽  
Vol 12 (4) ◽  
pp. e227974
Author(s):  
Antonio Liras ◽  
Luis Romeu
Keyword(s):  
Factor Viii ◽  
Conventional Treatment ◽  
Coagulation Factors ◽  
Clotting Factor ◽  
Haemophilia A ◽  
Severe Haemophilia ◽  
Optimal Result ◽  
Dental Management ◽  
Efficient Access

Haemophilia is a hereditary X-linked recessive disorder caused by a deficiency of either clotting factor VIII (haemophilia A) or IX (haemophilia B). Conventional treatment is currently based on the use of either plasma derived or recombinant coagulation factors. This paper reports on the case of a patient with severe haemophilia who presented with mesial decay and interproximal tartar build-up, for which extraction and scaling to remove tartar deposits were indicated. Following extraction, the usual haemostasis techniques were applied, and postoperative prophylactic antihaemophilic treatment was indicated for 2 or 3 days. The patient presented with moderate bleeding for a few minutes immediately after the procedure. Administration of factor VIII before surgery as well as the patient’s favourable pharmacokinetic response allowed for an optimal result. This treatment has afforded patients with haemophilia a better quality of life, and safe and efficient access to invasive surgical procedures.

Animal Testing of Retroviral-Mediated Gene Therapy for Factor VIII Deficiency

1999 ◽  
Vol 82 (08) ◽  
pp. 555-561 ◽  
Author(s):  
Douglas Jolly ◽  
Judith Greengard
Keyword(s):  
Gene Therapy ◽  
Factor Viii ◽  
Hemophilia A ◽  
Joint Damage ◽  
Coagulation Factor ◽  
The United States ◽  
Severe Hemophilia ◽  
Factor Viii Gene ◽  
Bleeding Episodes

IntroductionHemophilia A results from the plasma deficiency of factor VIII, a gene carried on the X chromosome. Bleeding results from a lack of coagulation factor VIII, a large and complex protein that circulates in complex with its carrier, von Willebrand factor (vWF).1 Severe hemophilia A (<1% of normal circulating levels) is associated with a high degree of mortality, due to spontaneous and trauma-induced, life-threatening and crippling bleeding episodes.2 Current treatment in the United States consists of infusion of plasma-derived or recombinant factor VIII in response to bleeding episodes.3 Such treatment fails to prevent cumulative joint damage, a major cause of hemophilia-associated morbidity.4 Availability of prophylactic treatment, which would reduce the number and severity of bleeding episodes and, consequently, would limit such joint damage, is limited by cost and the problems associated with repeated venous access. Other problems are associated with frequent replacement treatment, including the dangers of transmission of blood-borne infections derived from plasma used as a source of factor VIII or tissue culture or formulation components. These dangers are reduced, but not eliminated, by current manufacturing techniques. Furthermore, approximately 1 in 5 patients with severe hemophilia treated with recombinant or plasma-derived factor VIII develop inhibitory humoral immune responses. In some cases, new inhibitors have developed, apparently in response to unnatural modifications introduced during manufacture or purification.5 Gene therapy could circumvent most of these difficulties. In theory, a single injection of a vector encoding the factor VIII gene could provide constant plasma levels of factor in the long term. However, long-term expression after gene transfer of a systemically expressed protein in higher mammals has seldom been described. In some cases, a vector that appeared promising in a rodent model has not worked well in larger animals, for example, due to a massive immune response not seen in the rodent.6 An excellent review of early efforts at factor VIII gene therapy appeared in an earlier volume of this series.7 A summary of results from various in vivo experiments is shown in Table 1. This chapter will focus on results pertaining to studies using vectors based on murine retroviruses, including our own work.

Successful Long Term Therapeutic Expression of Factor VIII in Hemophilia A Dogs After Administration of AAV-cFVIII Using a Two-Chain or Single Chain Delivery Approach.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 546-546
Author(s):  
Denise E. Sabatino ◽  
Ekaterina Altynova ◽  
Amy M. Lange ◽  
Shangzhen Zhou ◽  
Elizabeth P. Merricks ◽  
...  
Keyword(s):  
Low Dose ◽  
Hemophilia A ◽  
High Dose ◽  
Dependent Manner ◽  
Igg Antibodies ◽  
Single Chain ◽  
Spontaneous Bleeding ◽  
Aav Vector ◽  
Bleeding Episodes

Abstract Abstract 546 While adeno-associated virus (AAV) is a promising gene delivery vector, it has been challenging to deliver FVIII due to the large size of the FVIII cDNA and the high frequency of FVIII antibody formation in hemophilia A (HA) patients. We used two approaches to overcome the size limitation of AAV for FVIII: (1) two-chain delivery in which the canine FVIII (cFVIII) heavy chain (HC) is delivered in one AAV vector and the cFVIII light chain (LC) is delivered in a second AAV vector and (2) single chain delivery in which the B-domain deleted cFVIII cDNA with minimal regulatory elements is within one AAV vector. In the two-chain approach AAV-HC (4.0 Kb) and AAV-LC (3.9 Kb) with a liver specific promoter was co-injected at a dose of 6×1012 vector genomes/vector/kg or 1.25×1013vg/vector/kg using AAV8 or AAV9 via hepatic infusion. Five hemophilia A dogs treated with AAV-HC and AAV-LC expressed 0.5-11% cFVIII in a dose-dependent manner. The mean cFVIII activity based on Coatest assay for the low dose was 1.3% (>1220d)(Linus)(AAV8) and 0.6% (>1770d)(H19)(AAV9), while for the high dose it was 5.2% (800d)(F24)(AAV8) and 2.4% (>1270d)(Woodstock)(AAV9). One dog (J60) had a splenectomy due to a complication at the time of surgery and has maintained high levels of expression (mean 11.0%; >820d). The WBCT consistently remained at a mean of 17.6 min for low dose dogs and 13.7 min for high dose dogs compared to 8-12 min in normal dogs. Using novel reagents that we generated specific to cFVIII, we developed assays to detect cFVIII antigen levels and IgG antibodies. Despite receiving equal doses of each vector, at day 85 the cFVIII-LC antigen levels (71.7 ± 19.2 ng/ml) were >10-fold higher than would be predicted based on activity while the cFVIII-HC antigen levels (14.6 ± 9.2 ng/ml) were >3-fold higher than activity. Since functional FVIII synthesis relies on the co-transduction of AAV-HC and AAV-LC in the same cell, this suggests that only a portion of the vector co-transduces and expresses cFVIII in the same cell and that the light chain is secreted more efficiently than the HC. No IgG antibodies to cFVIII were detected at any time point in these dogs. Three dogs have maintained FVIII expression for >3.5 years and two dogs for >2 years with ongoing observation. No spontaneous bleeding episodes have been observed in these dogs for a cumulative observation of >16 years while >80 bleeding episodes would be expected during this time period. The second approach, the single chain delivery, overcomes the co-transduction requirement of the two-chain approach by ensuring that each transduced cell expresses functional FVIII. However, it is difficult to efficiently package the large 5.2 Kb single chain construct into an AAV vector. Since no significant differences were observed between AAV8 and AAV9 using the two-chain approach, we used AAV8 to deliver the single chain cFVIII by peripheral vein infusion at 2×1013vg/kg or 4×1013vg/kg. The mean cFVIII activity was 0.7% (>430d) for the low dose dog (L51) and 6.8% (>290d) and 2.2% (>110d) for the high dose dogs (M06, M50). cFVIII HC and LC ELISA showed that cFVIII antigen levels correlated with activity. WBCT was a mean of 19.1 min for L51, 15.3 min for M06 and 11.6 min for M50. No spontaneous bleeding episodes have been observed in these dogs. The high dose dogs had no IgG antibodies to FVIII. L51 had transient IgG antibodies to FVIII until d52 in the absence of a Bethesda titer. A rise in FVIII expression in L51 coincided with the disappearance of anti-cFVIII antibodies. Comparison of single chain and two-chain delivery of FVIII reveals that (1) long term therapeutic levels of cFVIII in a dose-dependent manner can be obtained with both delivery approaches; (2) circulating cFVIII antigen levels are >10-fold higher than activity in the two-chain delivery in contrast to single chain delivery in which antigen correlates with activity; and (3) high antigen levels may facilitate tolerance to FVIII in the setting of liver-directed gene transfer, since a transient non-inhibitory antibody was observed in only one dog with very low FVIII levels. Notably, no cellular toxicity due to continuous expression of various forms of FVIII was found in these animals based on long-term sustained FVIII expression levels and normal liver enzymes in all eight HA dogs. Further studies to characterize the immune responses to the transgene will define the optimal vector approach. These data will form the basis for clinical studies in humans with severe HA. Disclosures: No relevant conflicts of interest to declare.

Efficacy and Safety Results of Prolong-9FP Clinical Program of Recombinant Fusion Protein Linking Coagulation Factor IX with Albumin (rIX-FP) in Previously Treated Patients with Hemophilia B

Blood ◽  
2015 ◽  
Vol 126 (23) ◽  
pp. 548-548 ◽  
Author(s):  
Elena Santagostino ◽  
Christine Voigt ◽  
Denise Wolko ◽  
Grace Cole ◽  
Yanyan Li ◽  
...  
Keyword(s):  
Day Treatment ◽  
Hemophilia B ◽  
Spontaneous Bleeding ◽  
Safety And Efficacy ◽  
On Demand ◽  
Routine Prophylaxis ◽  
Previously Treated Patients ◽  
Previously Treated ◽  
Bleeding Episodes

Abstract A fusion protein genetically linking recombinant human coagulation FIX with recombinant human albumin (rIX-FP) has been developed with an improved PK profile, thus improving hemophilia B treatment by allowing less frequent dosing. Two Phase 3 studies (CSL654-3001 and CSL654-3002) were completed. CSL654-3001 study evaluated safety and efficacy of rIX-FP for prophylaxis treatment (PT) of every 7-, 10- and 14-day and on-demand (ODT) of bleeding episodes in 63 previously treated patients (PTP), 12-61 years of age with hemophilia B (FIX ≤ 2%). Subjects in the on-demand arm received only ODT for 6 months and then switched to every 7-day PT. Subjects in the prophylaxis arm received every 7-day PT, and eligible subjects switched to every 10- or 14-day PT for approximately 12-18 months. Annualized spontaneous bleeding rates (AsBR) were compared between ODT and PT periods (in on-demand arm), and between 7-day PT and 10- or 14-day PT (in prophylaxis arm). CSL654-3002 study evaluated safety and efficacy of rIX-FP for weekly prophylaxis regimen in 27 previously treated patients younger than 12 years with hemophilia B (FIX ≤ 2%) for approximately 12 months. Annualized spontaneous bleeding rates (AsBR) were calculated. The median annualized spontaneous bleeding rate were all 0.00 for all treatment interval (7-day, 10-day or 14-day) and in both studies age groups (1-11 years and 12-65 years) during the two completed phase 3 studies. Seventy-six subjects from both studies continued their prophylaxis regimen in the on-going extension study. In addition, subjects (including children), switched to longer treatment intervals of 10-day, 3 times per month or 14-day or lowered their weekly prophylaxis dose. Nine subjects switched to 21-day treatment interval with 100 IU/kg rIX-FP. As of 28 July 2015, at least 50 subjects (PTP) had achieved 100 EDs without developing an inhibitor to FIX or antibodies to rIX-FP. The long term safety and efficacy of rIX-FP will be presented. This presentation includes the new information regarding the change to longer than 7-day treatment regimens in the extension study, among those subjects (1-61 years of age) that previously participated in the lead in studies. Conclusion: The Prolong - 9FP clinical programdemonstrated the clinical efficacy of rIX-FP for routine prophylaxis every 7-, 10- and 14-day treatment intervals. Routine prophylaxis once every 21 days may be effective in preventing bleeding episodes in a selected patient population. In addition, rIX-FP demonstrated favorable long-term safety and tolerability. Disclosures Santagostino: Novo Nordisk: Speakers Bureau; Bayer: Speakers Bureau; CSL Behring: Speakers Bureau; Baxter/Baxalta: Speakers Bureau; Pfizer: Research Funding, Speakers Bureau; Biogen/Sobi: Speakers Bureau; Biotest: Speakers Bureau; Kedrion: Speakers Bureau; Octapharma: Speakers Bureau; Roche: Speakers Bureau. Voigt:CSL Behring: Employment. Wolko:CSL Behring: Employment. Cole:CSL Behring: Employment. Li:CSL Behring: Employment. Jacobs:CSL Behring: Employment.

scholarly journals Haemophilia and Joint Disease: Pathophysiology, Evaluation, and Management

2011 ◽  
Vol 1 (1) ◽  
pp. 51-59 ◽  
Author(s):  
Karin Knobe ◽  
Erik Berntorp
Keyword(s):  
Joint Disease ◽  
Clotting Factor ◽  
Recurrent Bleeding ◽  
Effective Prevention ◽  
Haemophilic Arthropathy ◽  
Chronic Synovitis ◽  
Bleeding Episodes ◽  
End Stage ◽  
Clotting Factor Concentrates

In patients with haemophilia, regular replacement therapy with clotting factor concentrates (prophylaxis) is effective in preventing recurrent bleeding episodes into joints and muscles. However, despite this success, intra-articular and intramuscular bleeding is still a major clinical manifestation of the disease. Bleeding most commonly occurs in the knees, elbows, and ankles, and is often evident from early childhood. The pathogenesis of haemophilic arthropathy is multifactorial, with changes occurring in the synovium, bone, cartilage, and blood vessels. Recurrent joint bleeding causes synovial proliferation and inflammation (haemophilic synovitis) that contribute to end-stage degeneration (haemophilic arthropathy); with pain and limitation of motion severely affecting patients’ quality of life. If joint bleeding is not treated adequately, it tends to recur, resulting in a vicious cycle that must be broken to prevent the development of chronic synovitis and degenerative arthritis. Effective prevention and management of haemophilic arthropathy includes the use of early, aggressive prophylaxis with factor replacement therapies, as well as elective procedures, including restorative physical therapy, analgesia, aspiration, synovectomy, and orthopaedic surgery. Optimal treatment of patients with haemophilia requires a multidisciplinary team comprising a haematologist, physiotherapist, orthopaedic practitioner, rehabilitation physician, occupational therapist, psychologist, social workers, and nurses.

scholarly journals Etranacogene dezaparvovec for hemophilia B gene therapy

2021 ◽  
Vol 2 ◽  
pp. 263300402110588
Author(s):  
Courtney D. Thornburg
Keyword(s):  
Gene Therapy ◽  
Clinical Trials ◽  
Continuous Production ◽  
Factor Ix ◽  
Hemophilia B ◽  
Clotting Factor ◽  
Plain Language ◽  
Long Term Follow Up

The treatment landscape for hemophilia has been rapidly changing with introduction of novel therapies. Gene therapy for hemophilia is a promising therapeutic option for sustained endogenous factor production to mitigate the need for prophylactic treatment to prevent spontaneous and traumatic bleeding. Etranacogene dezaparvovec is an investigational factor IX (FIX) gene transfer product that utilizes the adeno-associated virus (AAV) 5 vector with a liver-specific promoter and a hyperactive FIX transgene. Here, the development of etranacogene dezaparvovec and available efficacy and safety data from clinical trials are reviewed. Overall, etranacogene dezaparvovec provides sustained FIX expression for more than 2 years and allows for a bleed and infusion-free life in the majority of patients. Safety, efficacy, and quality-of-life data will inform shared decision-making for patients who are considering gene therapy. Long-term follow-up regarding duration of expression and safety are crucial. Plain Language Summary Factor IX Padua gene therapy to boost clotting factor and prevent bleeding for people living with hemophilia B People living with hemophilia have low or missing clotting factor, which can lead to bleeding that is unexpected or caused by a traumatic event (such as a sports injury or surgery). There are two main types of hemophilia: clotting factor (F)VIII deficiency (known as hemophilia A) and FIX deficiency (known as hemophilia B). People living with the severe or moderately severe forms of hemophilia (clotting factor levels below 3% of normal) need regular treatment, typically by infusions into the vein, to stop or prevent bleeding and damage to their joints. Gene therapy is currently being investigated as a new treatment option that introduces a working copy of the clotting factor gene to the liver. Following treatment, clotting factor is produced by the liver. Etranacogene dezaparvovec [Et-ra-na-co-gene dez-a-par-vo-vec] is a form of gene therapy for people living with hemophilia B. This form of gene therapy includes a modified form of FIX (FIX Padua) which produces high levels of FIX activity compared with normal FIX. It is being tested to see whether individuals will have low rates of bleeding and not need to treat themselves with clotting factor. In the clinical trials, participants with FIX levels below 2% (of normal) receive a single gene therapy infusion. The results of the trials have so far shown that patients given etranacogene dezaparvovec have continuous production of FIX, whereby they have reported much less bleeding and factor treatment. Questions relating to the safety of the gene therapy and how long it works will hopefully be answered through long-term follow-up of the patients once the trials are completed.

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