Gene Therapy for Hemophilia B Shows Positive Results in Phase 3 Trial

uniQure announced positive 52-week data this week for its pivotal phase 3 clinical trial of a gene therapy candidate for severe and moderately severe hemophilia B.

The HOPE-B trial of AMT-061 (etranaogene dezaparvovec) involved 54 patients, all of whom received the adeno-associated virus 5 (AAV5)–based gene therapy.

The company said it is the largest group of patients with hemophilia B to receive a single gene therapy investigational product so far. Patients with hemophilia B have mutations in the factor IX gene and lack sufficient levels of the clotting factor IX.

“Data from the HOPE-B pivotal study showed that participants continued to demonstrate durable, sustained increases in Factor IX (FIX) activity,” the company said in a statement.

At 52 weeks post infusion, patients had a mean FIX activity of 41.5% of normal, as measured by a 1-stage APTT-based clotting assay, compared with a mean FIX activity of 39.0% of normal at 26 weeks of follow-up.

The 1-dose treatment also reduced the annualized rate of bleeding requiring treatment by 80% from a prospectively collected 3.39 at baseline to 0.68 bleeding episodes per year (P < .0001).

Late last year, the FDA placed a clinical hold on the trial after 1 patient developed a type of liver cancer, but the hold was lifted in April 2021 after an investigation and analysis showed that it was unlikely that etranaogene dezaparvovec was the reason for the cancer.

uniQure and its partner CSL Behring expect to submit a Biologics License Application to the FDA in the first quarter of 2022; that is a delay of about 6 months, according to a report, which noted that the FDA now wants 18-month data from the trial.

Over the next decade, multiple gene therapy approvals are expected. Currently in the United States, Medicaid pays for about half of all hemophilia B treatments, amounting to $1.57 billion in 2019.