The U.S. Food and Drug Administration has approved etranacogene dezaparvovec (Hemgenix) for the treatment of adults with Hemophilia B who currently use Factor IX prophylaxis therapy, or have current or historical life-threatening hemorrhage, or have repeated serious spontaneous bleeding episodes.

Hemophilia B is a congenital bleeding disorder caused by dysfunction or deficiency of coagulation Factor IX. People with this condition may bleed for longer periods of time after injury or surgery. They are also susceptible to spontaneous bleeding in muscles, joints and organs, which can be extremely painful and, in some cases, life-threatening.

The current standard of care for hemophilia B includes life-long prophylactic infusions of Factor IX. While infusions can significantly benefit these patients, infusions are inconvenient, painful, and can cause veins to fibrose over time. A patient’s immune system may also generate inhibitors against the replacement factor, negating the treatment benefit. Additionally, prophylactic Factor IX replacement therapy sometimes fails to control unobservable micro-bleeds in the joints, meaning that the degeneration can continue despite regular infusions. As such, there is a need for novel therapeutic options for hemophilia B patients.

Etranacogene dezaparvovec is an adeno-associated virus five (AAV5)-based gene therapy. The approval of this drug was based on two studies (NCT03569891 and NCT03489291) of 57 adult men, 18- to 75-years-of-age with severe or moderately-severe hemophilia B. Effectiveness was established based on decreases in the men’s annualized bleeding rate (ABR). In the HOPE-B study, which had 54 participants, the subjects had increases in Factor IX activity levels, a decreased need for routine Factor IX replacement prophylaxis, and a 54% reduction in ABR compared to baseline. Further, 94% of patients given the gene therapy no longer require  prophylactic infusions of Factor IX.

The most common adverse reactions associated with Hemgenix included liver enzyme elevations, headache, mild infusion-related reactions and flu-like symptoms. Patients should be monitored for adverse infusion reactions and liver enzyme elevations (transaminitis) in their blood.

The gene therapy was developed by uniQure and acquired by CSL Behring. At present, the cost of the one-infusion gene therapy has yet to be established but could be as high as $2.9 million.

To learn more about hemophilia B and other rare hematological disorders, visit