Hemgenix Approved by FDA to Become 1st Gene Therapy for Hem B

Therapy meant for patients on prophylaxis or with serious bleeding episodes

Margarida Maia, PhD avatar

by Margarida Maia, PhD |

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The first gene therapy for adults with hemophilia B — branded as Hemgenix (etranacogene dezaparvovec) — has been approved by the U.S. Food and Drug Administration (FDA).

Meant to be a one-time treatment, Hemgenix is expected to keep bleeding in check in the long term, while also allowing patients to skip or stop their prophylactic (preventive) therapy, which is considered the standard care for hemophilia B.

Hemgenix is indicated for those who are currently on prophylactic therapy or have (or have had) life-threatening bleeding or repeated, serious spontaneous bleeding episodes.

“Gene therapy for hemophilia has been on the horizon for more than two decades,” Peter Marks, MD, PhD, director of the FDA’s Center for Biologics Evaluation and Research, said in a press release.

“Today’s approval provides a new treatment option for patients with hemophilia B and represents important progress in the development of innovative therapies for those experiencing a high burden of disease associated with this form of hemophilia,” Marks added.

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Hemophilia occurs when the body does not make enough of certain clotting factor proteins that help the blood to clot. This means that people with hemophilia bleed more often and longer than normal. The specific type of hemophilia depends on the clotting factor that is missing. In hemophilia B, it is factor IX.

Hemgenix (formerly known as EtranaDez, or AMT-061) uses a harmless virus to carry into the liver a highly functional version of the gene that contains instructions for making factor IX. Once there, the modified gene is used by liver cells to spur on the production of the missing factor IX. A single dose of Hemgenix given by infusion into a vein is expected to keep factor IX levels raised for the long term, thereby limiting hemophilia symptoms.

Its approval was mainly supported by data from an ongoing Phase 3 trial called HOPE-B (NCT03569891), which is evaluating the safety and efficacy of Hemgenix in 54 men, ages 18–75, with moderate to severe hemophilia B, over a period of five years.

Men who took part in HOPE-B had stable and durable increases in factor IX activity levels. Six months after the infusion, factor IX activity levels reached a mean 39% of normal; at two years after the infusion, they were at about 37%.

Seven to 18 months after the infusion, the annualized bleeding rate, which is the number of bleeds calculated as an annual rate, had dropped by 54% from the trial’s lead-in period.

Most men (94%) treated with Hemgenix stopped taking their routine factor IX infusions and no longer used prophylactic therapy.

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Side effects include infusion-related reactions and elevated liver enzyme levels

“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,” Steven Pipe, MD, a lead investigator in the HOPE-B trial, said in another press release. Pipe is a professor of pathology and the Laurence A. Boxer research professor of pediatrics at the University of Michigan.

The most common side effects reported in the study included liver enzyme elevations, headache, flu-like symptoms, infusion-related reactions, fatigue, and feeling unwell. Patients should be monitored for infusion-related reactions and liver enzyme elevations in their bloodstream.

“We have always believed that gene therapy had the potential to provide transformative benefits to people living with hemophilia B and are excited that the hemophilia community will have a new, safe and effective treatment option available to them,” said Matt Kapusta, CEO of uniQure, which led research and clinical development of the gene therapy for more than a decade.

CSL Behring bought the global rights to market Hemgenix from uniQure and is planning to make the gene therapy available to patients as soon as possible.

“With Hemgenix, we now offer a comprehensive portfolio of innovative medicines for hemophilia B, giving people living with the condition more choice in treatments and better and more durable control over their disease,” said Bill Mezzanotte, head of research and development, and chief medical officer of CSL.

The gene therapy is also under review by European regulators.