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# CSL Behring BLA for Hemophilia B Gene Therapy
- URL: https://www.fdaweb.com/csl-behring-bla-for-hemophilia-b-gene-therapy/
- Published: 2022-05-24T12:00:00.000Z
- Updated: 2026-09-14T17:46:00.000Z
- Author: David McFarland
- Tags: Biologics, #legacy-id-D5151884

FDA has accepted for priority review a CSL Behring BLA for etranacogene dezaparvovec, an investigational gene therapy for treating adults with hemophilia B. The therapy is designed to “make near-normal blood-clotting ability possible by addressing the underlying cause of hemophilia B: a faulty gene that causes a deficiency in clotting Factor IX (FIX),” the company says. “Etranacogene dezaparvovec has been shown in clinical trials to significantly reduce the rate of annual bleeds in trial participants after a single one-time infusion and, if approved, would be the first ever gene therapy treatment option for the hemophilia B community.”  
  
The submission is based on data from the pivotal HOPE-B trial, which showed a reduction in adjusted annualized bleeding rate of 64% and superiority to prophylaxis treatment at 18 months post-treatment compared to a six-month run in period, CSL Behring says.  
  
Etranacogene dezaparvovec uses a specific type of adeno-associated virus (AAV), called AAV5, as its vector. The AAV5 vector carries the Padua gene variant of FIX, which generates FIX proteins that are five to eight times more active than normal, the company says. “Preclinical and clinical data show that AAV5-based gene therapies may be clinically effective in a large percentage of hemophilia B patients with pre-existing antibodies to AAV vectors, thereby potentially increasing patient eligibility for treatment,” it says.