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Gene Therapy Breakthrough reduces Bleeding in Hemophilia B


Clinical trial finds that novel gene therapy reduces bleeding in Hemophilia B

Hemophilia B is a rare genetic disorder that affects blood clotting. It is caused by a deficiency in clotting factor IX, which is needed to form blood clots to stop bleeding. Without enough factor IX, people with hemophilia B may experience prolonged bleeding episodes after an injury or surgery or spontaneous bleeding into joints and muscles. Hemophilia B is usually diagnosed in childhood, and there is no cure. Treatment typically involves regular infusions of factor IX to prevent bleeding and manage symptoms. People with hemophilia B can lead normal, active lives with proper care.

Gene Therapy

Gene therapy is a promising approach to treating hemophilia B. Gene therapy aims to introduce a functional copy of the factor IX gene into the body, which can then produce a steady supply of clotting factor IX without the need for frequent infusions.

Clinical Trial

In an open-label phase 3 study, researchers tested the safety and efficacy of a new gene therapy called etranacogene dezaparvovec for hemophilia B. The study enrolled 54 men with hemophilia B, all with 2% or less of the average factor IX activity levels. After a lead-in period of at least six months of factor IX prophylaxis, the participants received one etranacogene dezaparvovec gene therapy infusion. The researchers then evaluated the participants' bleeding rates and factor IX activity levels 18 months after treatment.

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The trial found that etranacogene dezaparvovec was non-inferior and superior to factor IX prophylaxis in reducing bleeding rates. The annualized bleeding rate decreased from 4.19 during the lead-in period to 1.51 during months 7 through 18 after treatment. This means gene therapy reduced bleeding rates by 64% compared to prophylactic factor IX therapy. In addition, factor IX activity levels increased by an average of 34.3 percentage points at 18 months after treatment, and usage of factor IX concentrate decreased by an average of 248,825 units per year per participant post-treatment period.

Safety Profile

The study also found that etranacogene dezaparvovec was safe and well-tolerated by the participants. No treatment-related serious adverse events occurred, and the gene therapy had a favorable safety profile.


Etranacogene dezaparvovec gene therapy could be an effective and safe treatment option for people with hemophilia B. However, further research is needed to confirm these results and determine the long-term safety and efficacy of the gene therapy. Nevertheless, the study represents an essential step in developing gene therapy for hemophilia B and offers hope for people living with this challenging condition.
New England Journal of Medicine, Feb-23-23
ClinicalTrials.gov, NCT03569891

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This content is for informational and educational purposes only. It is not intended to provide medical advice or to take the place of such advice or treatment from a personal physician. All readers/viewers of this content are advised to consult their doctors or qualified health professionals regarding specific health questions. CenTrial Data Ltd. does not take responsibility for possible health consequences of any person or persons reading or following the information in this educational content. Treatments and clinical trials mentioned may not be appropriate or available for all trial participants. Outcomes from treatments and clinical trials may vary from person to person. Consult with your doctor as to whether a clinical trial is a suitable option for your condition. Assistance from generative AI tools may have been used in writing this article.