Bleeding Disorders

FDA Approves First Gene Therapy for Hemophilia B

The FDA has approved etranacogene dezaparvovec for the treatment of adults with Hemophilia B who are currently using Factor IX prophylaxis therapy, have a history of life-threatening hemorrhaging, or have serious spontaneous bleeding episodes. The adeno-associated virus vector-based therapy is the first-of-its-kind for the treatment of Hemophilia B.

“Gene therapy for hemophilia has been on the horizon for more than two decades,” Peter Marks, MD, PhD, director of the FDA’s Center for Biologics Evaluation and Research, said in a press release. “Despite advancements in the treatment of hemophilia, the prevention and treatment of bleeding episodes can adversely impact individuals’ quality of life.”

Hemophilia B is a genetic bleeding disorder that mostly affects men—about one in 40,000 are diagnosed with the disease. Women can be carriers as well, but show no symptoms or have mild cases. Hemophilia B is caused by missing or insufficient levels of blood clotting Factor IX—a protein needed to produce blood clots in order to stop bleeding.

The approval of etranacogene dezapervovec follows two studies that examined the safety and efficacy of the treatment of severe or moderate Hemophilia B. The studies evaluated 57 men aged 18 to 75 years, and used the decrease in the men’s annualized bleeding rate (ABR) as a marker for the effectiveness of treatment. One study had a total of 54 participants that showed an increase in Factor IX activity levels, a decrease in the need for routine Factor IX replacement prophylaxis, and a 54% reduction in ABR when compared to baseline.

The most common adverse reactions associated with the treatment included liver enzyme elevations, headache, mild infusion-related reactions, and flu-like symptoms. It is recommended that patients be monitored for adverse infusion reactions in addition to liver enzyme elevations in their blood.


—Jessica Ganga


FDA approves first gene therapy to treat adults with hemophilia B. News release. US Food and Drug Administration; November 22, 2022. Accessed November 28, 2022.