What the trial was testing
The trial enrolled 3 patients with hemophilia b. The study was sponsored by CSL Behring and tracked outcomes across the full group of patients who matched the trial's eligibility profile.
It was initial testing (phase 2). 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
Factor IX rose to 47% of normal — and bleeding stopped completely.
Blood Advances · 2019 · NCT03489291
These findings — that factor IX activity at 26 weeks and complete bleed cessation after gene therapy — were published in the Blood Advances and represent the headline result of the study.
Researchers tracked outcomes across 3 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 b, 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
Etranacogene dezaparvovec (Hemgenix) is FDA-approved and available now for hemophilia B in adults. It is a one-time IV infusion that can replace lifelong factor IX prophylaxis for many patients. The drug list price is the highest of any U.S. medicine ($3.5 million), but most major insurers cover it. Ask a hemophilia center about eligibility.
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 b trials
Efficacy and Safety of CSL222 (Etranacogene Dezaparvovec) Gene Therapy in Adults With Hemophilia B With Pretreatment Adeno-associated Virus Serotype 5 (AAV5) Neutralizing Antibodies (Nabs)
The purpose of this study is to assess the risk of bleeding due to failure of expected pharmacological action of CSL222 in adults with severe or moderately severe hemophilia B with detectable pretreatment AAV5 Nabs.
A Study to Evaluate the Safety and Efficacy of ZS801 in Adult Hemophilia B Patients
A non-randomized, open-label, dose-escalation, phase I/II study to evaluate the safety, tolerability, kinetics and efficacy of a single intravenous infusion of ZS801 in hemophilia B subjects with endogenous FIX ≤2%.