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FDA Approves Gene Therapy for Hemophilia B

If you have ever had a cut, tooth extraction, or been bruised, you know the importance of your body’s ability to form a clot and stop that bleeding.

Usually, when someone bleeds, platelets (tiny blood cells) and proteins called clotting factors come together in a series of events leading to clot formation.

Recently, the U.S. Food and Drug Administration (FDA) approved Hemgenix as a one-time gene therapy for adults with hemophilia B, a condition that affects blood clotting.

What is hemophilia B? 

Hemophilia B is a rare genetic bleeding disorder where the body makes an abnormal version of an essential clotting factor IX, or the body simply does not make enough.1

This lack of clotting factor IX results in impaired clot formation mechanism and uncontrolled, or even spontaneous bleeding.1 

Who is affected by hemophilia B?

According to the United States Centers for Disease Control and Prevention, hemophilia B occurrence is approximately 1 in 5000 live births.2

All races and ethnic groups are affected and males are more affected than females.2 

What are the current treatment approaches?

The current approach for hemophilia B is known as routine prophylaxis (prevention).2 Routine prophylaxis has its limitations including the need for regular intravenous (IV) injections which can have a risk of infection.

Periodic infusions of factor IX are also routine for those with hemophilia B.2 Unfortunately, injections and infusions can result in breakthrough bleeding episodes.

Another complication of the prophylaxis method is the development of antibodies.

These antibodies are inhibitors that reduce or eliminate the activity of factor IX.2 

How can gene therapy be used to treat hemophilia B? 

Hemgenix (etranacogene dezaparvovec-drlb) is a one-time gene therapy for adults with hemophilia B to restore the activity of factor IX.

This gene therapy will enable the liver to produce factor IX protein, to increase their blood levels and thereby limit bleeding episodes. 

Hemgenix is an adeno-associated virus vector-based gene therapy. Hemgenix is indicated for people with hemophilia B who

  • are currently using factor IX prophylaxis therapy,
  • have a current or historical life-threatening hemorrhage,
  • or have repeated, serious spontaneous bleeding episodes.1 

Is this gene therapy safe and effective? 

Based on the results of two studies, this gene therapy is safe and effective for people with hemophilia B. However, the more serious risks of Hemgenix include infusion reactions and elevation of liver enzymes.

Patients would have to be routinely monitored for symptoms or complications.


Hemgenix as gene therapy has shown better results compared to the prophylactic treatment in people with hemophilia B. Thankfully, the recent FDA approval of this drug will help improve the quality of life for many.


  1. FDA . (2022, November 22). FDA approves first gene therapy to treat adults with hemophilia B. U.S. Food and Drug Administration. https://www.fda.gov/news-events/press-announcements/fda-approves-first-gene-therapy-treat-adults-hemophilia-b 
  2. CDC. (August 1, 2022). Hemophilia. Centers for Disease Control and Prevention. https://www.cdc.gov/ncbddd/hemophilia/facts.html
Purnima Sharma PhD Medical Writer
Purnima Sharma PhD Medical Writer
Purnima Sharma, PhD., is a Medical Writer with a decade of successful experience in medical/ regulatory writing. She has worked in a wide range of therapeutic areas such as neurosciences, cardiology, and gastrointestinal disorders. She is very self-motivated, analytical, and detail-oriented professional, successful in fast-paced, high pressured work environment. Outside of work, she enjoys working out and walking.


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