FDA approves first gene therapy for hemophilia B

By Rachel Arthur contact

- Last updated on GMT

Pic:getty/svetlanakrivenceva
Pic:getty/svetlanakrivenceva

Related tags: Hemophilia, Gene therapy, CSL, CSL Behring, Viral vector

CSL’s Hemgenix (etranacogene dezaparvovec-drlb) becomes the first treatment to offer patients freedom from regular ongoing infusions.

Hemgenix reduces the rate of annual bleeds, reduces or eliminates the need for prophylactic therapy, and generates elevated and sustained IX levels for years after a one-time infusion. 

The adeno-associated virus vector-based gene therapy has been in development for more than a decade: initially led by Dutch biotech uniQure with CSL acquiring global rights to commercialize the treatment in 2020.

CSL Behring, a CSL business, says will make Hemgenix available for eligible people with hemophilia B as soon as possible; while the therapy is also under assessment by other global regulatory agencies.

Patients can produce own factor IX

Hemophilia B is a rare, lifelong bleeding disorder caused by a single gene defect, resulting in insufficient production of factor IX, a protein primarily produced by the liver that helps blood clots form.

Treatments for moderate to severe hemophilia B include prophylactic infusions of factor IX replacement therapy to temporarily replace or supplement low levels of blood-clotting factor and, while these therapies are effective, those with hemophilia B must adhere to strict, lifelong infusion schedules.

Hemgenix reduces the rate of abnormal bleeding by enabling the body to continuously produce factor IX, the deficient associated virus (AAV). The AAV5 vector carries the Padua gene variant of Factor IX (FIX-Padua) to the target cells in the liver, generating factor IX proteins that are 5x-8x more active than normal. 

Hemgenix allows appropriate hemophilia B patients to produce their own factor IX, which can lower the risk of bleeding.

The FDA has approved 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.

In an ongoing clinical trial, the therapy reduced the rate of annual bleeds and 94% of patients discontinued factor IX prophylaxis and remained prophylaxis-free.

“We are thrilled to witness this milestone in hemophilia B treatment,”​ said Kim Phelan, Chief Operating Officer of The Coalition for Hemophilia B.

“Over the years we have seen a variety of advancements for the hemophilia community, but gene therapy is the first treatment option to offer those living with hemophilia B - and caregivers - the possibility of freedom from the need for regular, ongoing infusions."

The FDA approval is supported by results from the ongoing HOPE-B trial, the largest gene therapy trial in hemophilia B to date. The study demonstrated that Hemgenix allowed patients to produce mean factor IX activity of 39% at six months and 36.7% at 24 months post infusion.

Seven to 18 months post-infusion, the mean adjusted annualized bleeding rate (ABR) for all bleeds was reduced by 54% compared to the six-month lead-in period on factor IX prophylactic replacement therapy. In addition, 94% (51 out of 54) of patients treated discontinued use of prophylaxis and remained free of previous continuous routine prophylaxis therapy.

“Hemgenix is unique in its approach to increasing mean factor IX activity and hemostatic protection in those with hemophilia B, and today’s approval could fundamentally transform the treatment paradigm for this life-long condition,”​ said Dr. Steven Pipe, Professor and the Laurence A. Boxer Research Professor of Pediatrics and Professor of Pathology at the University of Michigan and a lead investigator in the HOPE-B study.

“As a clinician, I look forward to being able to provide a new treatment option that may help patients treated with Hemgenix become free from the regular infusion schedule that many people living with hemophilia B rely on to protect them from the debilitating effects of the condition.”

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