Earlier this week, the etranacogene dezaparvovec (Hemgenix) made history as the first gene therapy approved by the US Food and Drug Administration (FDA) for the treatment of the rare genetic disorder hemophilia B.
Patients with hemophilia B lack the ability to make a vital clotting protein called factor IX (FIX) and must receive regular infusions of the protein to prevent uncontrollable bleeding.
Gene therapies for hemophilia have been in development for decades. One of the biggest hopes came in 2020, when uniQure revealed promising phase 3 results for Hemgenix. Six months after receiving genetherapy, the average FIX activity in patients with hemophilia B increased from less than 2% of what is considered normal to 37.2%, and the need for FIX replacement therapy was reduced by a 96%.
The final data from the phase 3 trial in February 2022 generated more excitement. At 18 months post-dose, 94% of enrolled patients had discontinued use of FIX replacement therapies.
Gene therapy consists of a viral vector that delivers a gene for FIX to the liver. The liver cells then produce FIX and the levels of the clotting protein in the blood increase.
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