Pfizer has announced positive results from its phase 3 BENAGENE-2 study assessing the noninferiority and superiority of fidanacogene elaparvovec gene therapy for moderately severe to severe hemophilia B.

The results, announced via news release, showed the treatment met the primary superiority endpoint in terms of annualized bleeding rate (ABR) of total bleeds after infusion of the investigational therapy versus standard prophylactic factor IX administration.

“The burden people living with hemophilia B face is significant, with many receiving routine infusions or injections which can interfere with their ability to take part in day-to-day activities that many take for granted,” said Adam Cuker, MD, MS, director, University of Pennsylvania Comprehensive and Hemophilia Thrombosis Program, Philadelphia. “The BENEGENE-2 data demonstrate the promise of this gene therapy candidate as a potential one-time option for people living with hemophilia B as a means of reducing the clinical and treatment burden over the long term.”

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Fidanacogene elaparvovec is a novel gene therapy that employs a bio-engineered adeno-associated virus capsid to deliver a high-activity human coagulation FIX gene into patients with hemophilia B. Once treated, the goal is that patients will be able to produce FIX indefinitely after a single treatment, rather than requiring regular infusions of exogenous FIX.

The 45 patients in the BENAGENE-2 trial completed a lead-in study in which they received exogenous FIX over 6 months, followed by a single intravenous dose of 5e11 vg/kg fidanacogene elaparvovec.

The results demonstrated a mean ABR for all bleeds of 1.3 per year compared with 4.43 during the lead-in period, which represents a 71% reduction in ABR. Secondary endpoints included a 92% reduction in the annual infusion rate and a mean FIX activity of 27% at 15 months and 25% at 24 months.

Fidanacogene elaparvovec has already been granted breakthrough and orphan drug and regenerative medicines advance therapy designations from the US Food and Drug Administration, and priority medicines and orphan drug designations from the European Medicines Agency.


Pfizer announces positive top-line results from Phase 3 study of hemophilia B gene therapy candidate. News release. Pfizer, Inc.; December 29, 2022.