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Gene Therapy Research Offers Transformative Possibilities for People Living With Hemophilia B

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What’s in a gene? For people living with hemophilia B, the answer holds the key to their disease. That’s because hemophilia B, a rare life-long bleeding disorder, is caused by mutations in the F9 gene, which lead to insufficient levels of Factor IX (FIX), a protein primarily produced by the liver that helps blood clots form during the healing process.[i] The more severe the condition, the less able a person is to form blood clots, making them more vulnerable to bleeding. i


While the genetic underpinnings of hemophilia were identified in the 1950s, it wasn’t until 1982 that scientists successfully cloned the Factor IX gene, paving the way for breakthrough synthetic factor therapies (not derived from human plasma) using recombinant technologies.[ii]

Replacement factor therapies have dramatically improved the lives of people with hemophilia, allowing them to engage in daily activities with less fear of bleeding.ii However, risks and limitations remain even for patients who regularly receive replacement therapy.[iii] People who rely on regular intravenous infusions to prevent bleeding (prophylaxis treatment) must plan their lives around scheduled infusions and the highs and lows of their factor levels, which rise immediately after an infusion but drop over time — leaving them more vulnerable to breakthrough bleeds.[iv]

What if the next step in the treatment of hemophilia B could reduce its impact not for a day, or for a week, but potentially for years to come?

Gene therapy for hemophilia B is on the horizon

Hemophilia B is an ideal target for gene therapy because it’s caused by mutations in a single gene.[v] Gene therapies under investigation aim to provide a working copy of the F9 gene.v


How – and why – gene therapy breaks new ground for patients with hemophilia B

Current treatments for hemophilia B work to temporarily replace or supplement low levels of blood-clotting FIX.v But, gene therapy has the potential to help improve FIX levels by addressing the condition at its source: a faulty FIX gene.v Through a one-time infusion, gene therapy aims to enable patients to create their own FIX in the liver, potentially delivering lasting bleed protection for years.[vi] A goal of gene therapy is to provide long-term benefits of sustained factor IX activity levels from a single administration of treatment, potentially reducing or even eliminating bleeding and the need for regular, long-term prophylaxis.iv

Making gene therapy for hemophilia B a reality

Nearly 70 years after scientists identified the genetic cause of hemophilia B,[vii] we are closer than ever before to making the promise of gene therapy for hemophilia B a reality. While clinical trials for gene therapies are still ongoing and currently no hemophilia B gene therapy has received FDA approval, companies like CSL Behring are studying potential gene therapy treatments.


To learn more about gene therapy and hemophilia B, visit

[i]  Srivastava A, et al. WFH Guidelines for the Management of Hemophilia, 3rd edition. Haemophilia. 2020 Aug;26 Suppl 6:1-158. doi: 10.1111/hae.14046. Epub 2020 Aug 3. Erratum in: Haemophilia. 2021 Jul;27(4):699.

[ii] Nathwani AC, Tuddenham EGD. Haemophilia, the journey in search of a cure. 1960-2020. Br J Haematol. 2020 Nov; 191(4): 573-578. doi: 10.1111/bjh.17155.

[iii] Mannucci PM. Hemophilia therapy: the future has begun. Haematologica. 2020 Mar;105(3):545-553. doi: 10.3324/haematol.2019.232132. Epub 2020 Feb 14. PMID: 32060150.

[iv] Miesbach, W. et al. (2019). How to discuss gene therapy for haemophilia? A patient and physician perspective. Haemophili: the official journal of the World Federation of Hemophilia, 25(4), 545–557.

[v] Perrin, et al. Update on clinical gene therapy for hemophilia. ASH Publications. Blood (2019) 133 (5): 407-414. Introduction. 1-2.

[vi] Pipe SW, Recht M, Key NS, et al. First data from the phase 3 HOPE-B Gene therapy trial: efficacy and safety of etranacogene dezaparvovec (AAV5-Padua hFIX variant; AMT-061) in adults with severe or moderate-severe hemophilia B treated irrespective of pre-existing anti-capsid neutralizing antibodies. Abstract LBA-6. Presented at the 2020 American Society of Hematology Annual Meeting; December 8, 2020.

[vii] National Hemophilia Foundation. History. Timeline. 5. Last Accessed March 22, 2022 at

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