FDA Accepts BLA for Hemophilia B Gene Therapy

The FDA has accepted the biologics license application (BLA), for priority review, for etranacogene dezaparvovec (also known as CSL222), an investigational gene therapy for the treatment of adults with hemophilia B. The clinical development program for etranacogene dezaparvovec was led by uniQure, and CSL Behring has acquired global rights to commercialize the investigational treatment.

Etranacogene dezaparvovec was specifically 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. The therapy uses an adeno-associated virus as a vector that carries the Padua gene variant of Factor IX, which generates Factor IX proteins.

Etranacogene dezaparvovec has been shown in clinical trials to significantly reduce the rate of annual bleeds in people with hemophilia B after a single one-time infusion, and if approved, would be the first ever gene therapy treatment option for the hemophilia B community.

The BLA is supported by results from the pivotal HOPE-B trial, the largest gene therapy trial in hemophilia B to date. People with hemophilia B treated with etranacogene dezaparvovec demonstrated reduced adjusted annualized bleeding rate by 64% and superiority to prophylaxis treatment at 18 months post-treatment compared with a 6-month run in period.

The majority of adverse events (80.4%) were considered mild. One death occurred during the clinical trial and was considered unrelated to treatment by investigators. A serious adverse event of hepatocellular carcinoma was determined to be unrelated to treatment. No inhibitors to Factor IX were reported.