FDA Approves Pfizer’s Gene Therapy for Hemophilia B


Fidanacogene elaparvovec-dzkt (Beqvez) is a 1 time treatment that allows patients with hemophilia B to produce factor IX themselves.

The FDA has approved fidanacogene elaparvovec-dzkt (Beqvez) for the treatment of moderate to severe hemophilia B in adult patients who currently use factor IX (FIX) prophylaxis therapy, or have current or historical life-threatening hemorrhage, or have repeated, serious spontaneous bleeding episodes, and do not have neutralizing antibodies to adeno-associated virus serotype Rh74var (AAVRh74var) capsid, Pfizer announced in a release.1

The FDA approved Beqvez for the treatment of moderate to severe hemophilia B / cbies - stock.adobe.com

The FDA approved Beqvez for the treatment of moderate to severe hemophilia B / cbies - stock.adobe.com

Fidanacogene elaparvovec-dzkt is an adeno-associated virus-based gene therapy that imparts a functional copy of the FIX gene into transduced cells. Compared to the current standard of care, which requires intravenous infusions of FIX to be administered multiple times a week or month, fidanacogene elaparvovec-dzkt is a 1 time treatment that allows patients with hemophilia B to produce FIX themselves.


Trial Name: A Study to Evaluate the Efficacy and Safety of Factor IX Gene Therapy With PF-06838435 in Adult Males With Moderately Severe to Severe Hemophilia B

ClinicalTrials.gov Identifier: NCT03861273

Sponsor: Pfizer

Summary: This study will evaluate the efficacy and safety of PF-06838435 (a gene therapy drug) in adult male participants with moderately severe to severe hemophilia B (participants that have a Factor IX circulating activity of 2% or less). The gene therapy is designed to introduce genetic material into cells to compensate for missing or non-functioning Factor IX. Eligible study participants will have completed a minimum 6 months of routine Factor IX prophylaxis therapy during the lead in study (C0371004). Participants will be dosed once (intravenously) and will be evaluated over the course of 6 years. The main objective of the study will evaluate the annualized bleeding rate [ABR] for participants treated with gene therapy versus standard of care (SOC) therapy (FIX prophylaxis replacement regimen).

“Many people with hemophilia B struggle with the commitment and lifestyle disruption of regular FIX infusions, as well as spontaneous bleeding episodes, which can lead to painful joint damage and mobility issues,” Adam Cuker, MD, MS, director of the Penn Comprehensive and Hemophilia Thrombosis Program, said in a release.1 “A one-time treatment with Beqvez has the potential to be transformative for appropriate patients by reducing both the medical and treatment burden over the long term.”

The approval of fidanacogene elaparvovec-dzkt was based on data from the Benegene-2 study (NCT03861273), in which the gene therapy met its primary endpoint of non-inferiority in the annual bleeding rate (ABR) of total bleeds post-Beqvez infusion versus prophylaxis regimen with FIX, administered as part of usual care.

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Benegene-2 is an ongoing, phase 3, open-label, single-arm study that is evaluating the efficacy and safety of Beqvez in adult male participants with moderately severe to severe hemophilia B. The study cohort includes 45 patients aged 18 to 65 who completed a minimum of 6 months of routine FIX prophylaxis therapy. During the study, bleeds were eliminated in 60% of patients treated with fidanacogene elaparvovec-dzkt, compared to 29% in the FIX arm.

Fidanacogene elaparvovec-dzkt also met both of its key secondary endpoints. The gene therapy showed a 78% reduction in treated ABR, as well as a 92% reduction in annualized infusion rate.2 The therapy was well-tolerated, with the most common adverse reaction being an increase in transaminases. As part of its clinical program, Pfizer is continuing to monitor patients for long-term treatment durability and safety over 15 years.

Hemophilia B is a rare inherited bleeding disorder that leads to an insufficient production of the blood clotting factor IX. The condition, which is the second most prevalent form of hemophilia, mostly impacts males and has a global rate of 3.8 per 100000. It can lead to complications such as recurrent hemarthrosis, intracerebral hemorrhage, and HIV and HCV infection. In developed countries, patients born with hemophilia have a 64% lower chance of living a life of average duration and quality.3

“For people living with hemophilia, disease management can interfere with many aspects of their lives,” Kim Phelan, chief operating officer at the Coalition for Hemophilia B, said in a release.1 “A one-time infusion of Beqvez may allow eligible patients more time for the things they love. We are excited to have Beqvez as a promising treatment option for eligible people living with hemophilia B. We look forward to learning more and celebrating with the community and with Pfizer at our annual conference that is currently taking place.”

READ MORE: Rare Disease Resource Center

1. U.S. FDA Approves Pfizer’s BEQVEZ™ (fidanacogene elaparvovec-dzkt), a One-Time Gene Therapy for Adults with Hemophilia B. News Release. Pfizer. April 26, 2024. Accessed April 26, 2024. https://www.pfizer.com/news/press-release/press-release-detail/us-fda-approves-pfizers-beqveztm-fidanacogene-elaparvovec
2. Pfizer Announces Positive Top-Line Results from Phase 3 Study of Hemophilia B Gene Therapy Candidate. News Release. Pfizer. December 29, 2022. Accessed April 26, 2024. https://www.pfizer.com/news/press-release/press-release-detail/pfizer-announces-positive-top-line-results-phase-3-study
3. Alshaikhli A, Killeen RB, Rokkam VR. Hemophilia B. In: StatPearls. Treasure Island (FL): StatPearls Published; October 29, 2023. https://pubmed.ncbi.nlm.nih.gov/32809627/
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