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HemophiliaMarch 2022Summary reviewed June 2026

What the GENEr8-1 Trial Found — Gene Therapy for Severe Hemophilia A

Researchers tested valoctocogene roxaparvovec, a one-time gene therapy, in 134 men with severe hemophilia A. After one year, patients made their own clotting factor and needed 99% less replacement treatment. Bleeding episodes dropped by 84%.

What the trial was testing

The GENER8-1 enrolled 144 patients with hemophilia. The study was sponsored by BioMarin Pharmaceutical and tracked outcomes across the full group of patients who matched the trial's eligibility profile.

It was a large trial designed to confirm whether the treatment works well enough for wider use. Trials at this stage are designed to produce evidence regulators and physicians can act on — not just observations to follow up later.

What the results showed

One year after gene therapy, patients needed 99% less clotting factor replacement.

The New England journal of medicine · 2022 · NCT03370913

These findings — that patients made their own factor VIII and barely needed infusions anymore — were published in the The New England journal of medicine and represent the headline result of the study.

Researchers tracked outcomes across 144 patients enrolled in the trial. The result was consistent enough across the group that the team felt confident reporting it.

What this means for patients

For patients with hemophilia, this result changes the calculus on what to ask their care team about. Whether it changes day-to-day care depends on factors like disease subtype, prior treatments, and where the patient is in their care journey.

What you can do now

This gene therapy was FDA-approved in June 2023 under the brand name Roctavian. It's designed for adults with severe hemophilia A who don't have antibodies against the virus used to deliver the therapy. Talk to your hemophilia treatment center about whether you're a candidate.

Eligibility for the treatments mentioned above depends on specific test results and clinical history. Bring this summary, the trial name, and your most recent labs or pathology report to your next visit.

Open hemophilia trials