The FDA has accepted CSL Behring’s priority review application for a hemophilia B gene therapy, potentially fast-tracking the drug after a bumpy ride that included a clinical hold—and later, a lift.
If approved, etranacogene dezaparvovec—an AAV-5 gene therapy candidate given as a one-time treatment—would be the first gene therapy option for patients with hemophilia B, a life-threatening degenerative disease.
CSL Behring, the global biotherapeutics business of Australia-based CSL, acquired the gene therapy from biotech uniQure in June 2020. The therapy is designed to significantly reduce blood-clotting by addressing the underlying root of hemophilia B: a faulty gene that leads to a clotting deficiency.
Results from CSL and uniqure’s HOPE-B trial, the largest gene therapy trial in hemophilia B conducted thus far, support the biologics license application (BLA) for priority review. In the trial, hemophilia B patients receiving etranacogene dezaparvovec showed a 64% lower annualized bleeding rate and superiority to prophylaxis treatment at 18-months post-treatment compared to six months.
But it hasn’t been a smooth ride. In December 2020, the FDA slapped a clinical hold on the trial after a case of liver cancer was reported.
A months-long uniQure investigation found the gene therapy was “highly unlikely” to have triggered the cancer, with multiple pieces of evidence pointing to other causes. After four months, the FDA lifted the clinical hold, allowing the trial to resume.
One death did occur during the study, though it was found to be unrelated to the investigational treatment. Most of the adverse events reported in the HOPE-B trial were considered mild.
Now, CSL Behring holds the ticket to potentially fast-track the treatment to market. The FDA aims to make a decision on therapies accepted under priority review in six months, compared to 10 months for a standard review.
In March, the European Medicines Agency accepted an application from CSL for etranacogene dezaparvovec and is currently reviewing the therapy for that market.