FDA approves first gene therapy for Haemophilia B

The US Food and Drug Administration (FDA) has approved Hemgenix (etranacogene dezaparvovec), the first gene therapy for adults with Haemophilia B (congenital Factor IX deficiency) who currently use Factor IX prophylaxis therapy, or have current or historical life-threatening haemorrhage, or have repeated, serious spontaneous bleeding episodes.

Standard treatment for the condition involves replacing the missing or deficient clotting factor to improve the body’s ability to stop bleeding and promote healing. Patients with severe Haemophilia B typically need routine intravenous (IV) infusions of Factor IX replacement products to sustain sufficient clotting factor levels to prevent bleeding episodes.

Hemgenix gene therapy for Haemophilia B

Hemgenix, an adeno-associated virus vector-based IV infusion, carries a gene for clotting Factor IX. The gene is expressed in the liver to produce Factor IX protein, to increase blood levels of Factor IX and thereby limit bleeding episodes.

“Gene therapy for haemophilia has been on the horizon for more than two decades. Despite advancements in the treatment of haemophilia, the prevention and treatment of bleeding episodes can adversely impact individuals’ quality of life,” stated Dr Peter Marks, PhD, director of the FDA’s Center for Biologics Evaluation and Research. “Today’s approval provides a new treatment option and represents important progress in the development of innovative therapies for this form of haemophilia.”

Kim Phelan, Chief Operating Officer of The Coalition for Hemophilia B shared: “Over the years we have seen a variety of advancements for the haemophilia community, but gene therapy is the first treatment option to offer those living with haemophilia B ⁠— and caregivers ⁠—the possibility of freedom from the need for regular, ongoing infusions.”

Clinical development of Hemgenix was led by uniQure. Sponsorship of the clinical trials transitioned to Australian biopharma company CSL after it acquired global rights to commercialise the treatment in May 2021. The FDA granted approval of Hemgenix to CSL Behring LLC. 

Haemophilia B clinical trial

The safety and effectiveness of Hemgenix was evaluated in two studies of 57 adult males between 18 to 75 years old with severe or moderately severe Haemophilia B. Effectiveness was determined based on decreases in the men’s annualised bleeding rate (ABR). One study with 54 participants showed subjects had enhanced Factor IX activity levels, a decreased need for routine Factor IX replacement prophylaxis and a 54 percent reduction in ABR compared to baseline.

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

Hemgenix is currently under assessment by other regulatory agencies.