FDA approves CSL gene therapy for hemophilia B

November 23, 2022 - 5 minutes
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CSL has revealed that the U.S. Food and Drug Administration (FDA) has approved HEMGENIX (etranacogene dezaparvovec-drlb), the first and only one-time gene therapy for appropriate adults with hemophilia B. 

HEMGENIX is approved 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 the ongoing clinical trial, HEMGENIX reduced the rate of annual bleeds and 94% of patients discontinued factor IX prophylaxis and remained prophylaxis-free.

“As part of our promise to patients, CSL is committed to delivering innovative and groundbreaking solutions to address unmet medical needs, and we are proud to introduce the next wave of breakthrough medicines for people living with hemophilia B,” said Paul Perreault, CSL’s chief executive officer and managing director. 

“We recognize and thank all trial participants, scientists and investigators—without whom this important achievement would not have been possible—and look forward to seeing the positive impact of HEMGENIX on the hemophilia B community.”

Treatment options

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. While these therapies are effective, those with hemophilia B must follow lifelong infusion schedules. They may also still experience spontaneous bleeding episodes as well as limited mobility, joint damage or severe pain as a result of the disease. For appropriate patients, HEMGENIX allows people living with hemophilia B to produce their own factor IX, which can lower the risk of bleeding.

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“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.”

Study details

The FDA approval is supported by results from the ongoing HOPE-B trial, the largest gene therapy trial in hemophilia B to date. Results from 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 (4.1 to 1.9). 

Also, 94% of patients treated with HEMGENIX discontinued use of prophylaxis and remained free of previous continuous routine prophylaxis therapy. The most common side effects were liver enzyme elevations, headache, elevated levels of a certain blood enzyme, flu-like symptoms, infusion-related reactions, fatigue, nausea and feeling unwell.  

“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 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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The multi-year clinical development program for HEMGENIX was led by uniQure, and sponsorship of the clinical trials transitioned to CSL after it acquired global rights to commercialize the treatment.

CSL Behring, a CSL business, will make HEMGENIX available for eligible people with hemophilia B as soon as possible.

HEMGENIX is still currently under assessment by other regulatory agencies.

About hemophilia B 

Hemophilia B is a life-threatening rare disease. People with the condition are particularly vulnerable to bleeds in their joints, muscles, and internal organs, leading to pain, swelling, and joint damage. Current treatments for moderate to severe hemophilia B include life-long prophylactic infusions of factor IX to temporarily replace or supplement low levels of the blood-clotting factor.  

About CSL’s HEMGENIX 

HEMGENIX is a gene therapy that reduces the rate of abnormal bleeding in eligible people with hemophilia B by enabling the body to continuously produce factor IX, the deficient protein in hemophilia B.

It uses AAV5, a non-infectious viral vector, called an adeno-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. These genetic instructions remain in the target cells, but generally do not become a part of a person’s own DNA. Once delivered, the new genetic instructions allow the cellular machinery to produce stable levels of factor IX.

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