Hemgenix (etranacogene dezaparvovec)

The first gene therapy approved for hemophilia B. A single infusion enables the body to produce its own Factor IX clotting protein, potentially reducing or eliminating the need for regular factor infusions. It is approved for adults with hemophilia B who currently use Factor IX prophylaxis, have current or past life-threatening bleeding, or have repeated serious spontaneous bleeding episodes.

Hemgenix uses an AAV5 viral vector to deliver the Factor IX Padua gene variant to liver cells. The Padua variant produces a highly active form of Factor IX. After a single infusion, the liver begins manufacturing its own Factor IX, reducing or eliminating the need for regular clotting factor infusions.

Liver enzyme elevations are common and require monitoring. Headache, flu-like symptoms, and infusion-related reactions may occur. Liver blood tests are needed weekly for 3 months after the infusion, then monthly for up to 1 year. The label also warns about serious allergic and infusion reactions, including anaphylaxis (patients are watched for at least 3 hours after the infusion). It also warns about a possible risk of liver cancer (people at high risk need liver ultrasounds and AFP blood tests for 5 years) and says Factor IX levels and Factor IX inhibitors should be checked after treatment.

Single one-time intravenous infusion. Treatment takes about one to several hours at a specialized center. Patients require long-term follow-up monitoring.

Yes, Etranacogene dezaparvovec (Hemgenix) is FDA approved (2022) for the treatment of Hemophilia B.

In the Phase 3 HOPE-B trial, mean Factor IX activity was 36.9% of normal at 18 months and 36.1% at 5 years. The average yearly bleeding rate fell from 4.1 before treatment to 1.9 after (54% lower), and it stayed at 1.9 through 5 years of follow-up. 4 of 54 patients used Factor IX prophylaxis again at some point after treatment.

Hemgenix made headlines in November 2022 as both the first gene therapy for hemophilia B and one of the most expensive single-dose therapies at the time. It demonstrated the potential of gene therapy to replace lifelong factor replacement with a single infusion.

The Padua variant is a naturally occurring gain-of-function mutation that produces Factor IX protein 5-8 times more active than the normal version. This means lower levels of gene expression can still produce clinically effective clotting, improving the therapy's chance of success.

Hemgenix should not be given to people who have Factor IX inhibitors now or have had them in the past. Before treatment, doctors also check liver health with blood tests, a liver ultrasound and elastography, and may consult a liver specialist if they find problems. Treatment is postponed while a person has active hepatitis B or C. The label does not exclude people who already have antibodies to the AAV5 vector. In the trial, people with these antibodies (up to a titer of 1:678) had somewhat lower Factor IX levels on average, and one patient with a very high titer (1:3212) did not respond and stayed on regular prophylaxis.

Liver function must be monitored regularly for at least a year post-infusion, as liver enzyme elevations are common. Factor IX levels are also tracked. Some patients require corticosteroid treatment to manage immune responses to the viral vector in liver cells.

With Pfizer's discontinuation of Beqvez in February 2025, Hemgenix (by CSL Behring/uniQure) remains the only available gene therapy for hemophilia B. This makes it the sole gene therapy option for eligible hemophilia B patients seeking a one-time treatment.

HEMGENIX Connect assigns a dedicated support team including a Patient Resource Navigator and Case Manager for insurance coverage assistance, financial support, and copay assistance for eligible patients.