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Pfizer Receives Positive CHMP Opinion for its One-Time Gene Therapy for Adults with Hemophilia B

NEW YORK, May 31, 2024Pfizer Inc. (NYSE: PFE) today announced that the Committee for Medicinal Products for Human Use (CHMP) of the European Medicines Agency (EMA) adopted a positive opinion for fidanacogene elaparvovec, a gene therapy for the treatment of severe and moderately severe hemophilia B (congenital factor IX deficiency) in adult patients without a history of factor IX inhibitors and without detectable antibodies to variant AAV serotype Rh74.

Fidanacogene elaparvovec is a one-time treatment that is designed to enable people living with hemophilia B to produce factor IX (FIX) themselves, rather than requiring intravenous FIX infusions multiple times a week or month, which is the current standard of care.1,2

“Many people living with moderately severe to severe hemophilia B still experience persistent bleeding episodes, which can lead to painful joint damage and mobility issues,” said James Rusnak, M.D., Ph.D., Senior Vice President, Chief Development Officer, Internal Medicine and Infectious Diseases, Research and Development, Pfizer. “Gene therapy is a one-time treatment that has the potential to free patients from years of routine factor IX infusions – this recommendation for fidanacogene elaparvovec is a positive step for eligible patients.”

The Marketing Authorization Application for fidanacogene elaparvovec is based on results from the pivotal Phase 3 BENEGENE-2 study (NCT03861273) to evaluate the efficacy and safety of fidanacogene elaparvovec in adult male participants (age 18–65) with moderately severe to severe hemophilia B.

The European Commission, which grants central marketing authorizations in the European Union (EU), will review the CHMP recommendation and is expected to make a final decision in the coming months. If granted, the conditional marketing authorization of fidanacogene elaparvovec would be valid in all 27 EU member states, as well as in Iceland, Liechtenstein, and Norway. The CHMP recommendation for fidanacogene elaparvovec follows recent approvals by the U.S. Food and Drug Administration and Health Canada.3,4

About fidanacogene elaparvovec

Fidanacogene elaparvovec is a gene therapy that contains a bio-engineered adeno-associated virus (AAV) capsid and a high-activity variant of human coagulation FIX gene. For people living with hemophilia B, the goal of this gene therapy is to enable them to produce FIX themselves via this one-time treatment rather than needing regular intravenous infusions of FIX, as is the current standard of care.1,2,5

In December 2014, Pfizer licensed fidanacogene elaparvovec from Spark® Therapeutics. Under the agreement, Pfizer assumed responsibility for pivotal studies, any regulatory activities, and potential global commercialization of this gene therapy.


The BENEGENE-2 study is a Phase 3, open-label, single-arm study to evaluate the efficacy and safety of fidanacogene elaparvovec in adult male participants (age 18–65) with moderately severe to severe hemophilia B (defined as FIX circulating activity of 2% or less). The main objective of the study is to evaluate the annualized bleeding rate (ABR) for participants treated with gene therapy versus FIX prophylaxis replacement regimen, administered as part of usual care.

The study initially enrolled 45 participants. Eligible study participants have completed a minimum six months of routine FIX prophylaxis therapy during the lead-in study (NCT03587116) and received one intravenous dose of fidanacogene elaparvovec at a dose of 5 x 1011 vg/kg. Participants in the BENEGENE-2 study were screened with a validated assay designed to identify individuals who test negative for neutralizing antibodies to the gene therapy vector.

The European Marketing Authorization Application was based on a 15-month data cut in 41 participants (primary analysis) from the BENEGENE-2 study, with the 2-year data cut in these 41 participants provided during review. Clinical trial participants will be followed for up to a total of 15 years, including six years in the BENEGENE-2 study and an additional nine years as part of a separate Phase 3 study (NCT05568719) to learn about the long-term safety and efficacy of fidanacogene elaparvovec.

About Hemophilia B

Hemophilia is a rare genetic bleeding disorder which prevents normal blood clotting because of a deficiency in one of several blood-clotting factors and is predominately found in males.5,6 People with hemophilia are at risk for excessive and recurrent spontaneous and/or post-traumatic bleeding, which can be life-threatening, particularly in those with severe hemophilia.5,6 People with severe hemophilia often bleed spontaneously into their muscles or joints, or rarely into other critical closed spaces such as the intracranial space, where bleeding can be fatal.5,6

According to the World Federation of Hemophilia, more than 38,000 people worldwide are living with hemophilia B.7 People with hemophilia B have a deficiency in clotting FIX, a specific protein in the blood. Hemophilia B also is called congenital FIX deficiency or Christmas disease. The current standard of care requires recurrent intravenous infusions of either plasma-derived or recombinant FIX to control and prevent bleeding episodes.1,2,5

About Pfizer: Breakthroughs That Change Patients’ Lives

At Pfizer, we apply science and our global resources to bring therapies to people that extend and significantly improve their lives. We strive to set the standard for quality, safety and value in the discovery, development and manufacture of health care products, including innovative medicines and vaccines. Every day, Pfizer colleagues work across developed and emerging markets to advance wellness, prevention, treatments and cures that challenge the most feared diseases of our time. Consistent with our responsibility as one of the world’s premier innovative biopharmaceutical companies, we collaborate with health care providers, governments and local communities to support and expand access to reliable, affordable health care around the world. For 175 years, we have worked to make a difference for all who rely on us. We routinely post information that may be important to investors on our website at In addition, to learn more, please visit us on and follow us on X at @Pfizer and @Pfizer_News, LinkedIn, YouTube and like us on Facebook at

Disclosure Notice

The information contained in this release is as of May 31, 2024. Pfizer assumes no obligation to update forward-looking statements contained in this release as the result of new information or future events or developments.

This release contains forward-looking information about fidanacogene elaparvovec, a gene therapy, including its potential benefits, and EU regulatory review of fidanacogene elaparvovec for the treatment of adult patients with hemophilia B that involves substantial risks and uncertainties that could cause actual results to differ materially from those expressed or implied by such statements. Risks and uncertainties include, among other things, uncertainties regarding the commercial success of fidanacogene elaparvovec; the uncertainties inherent in research and development, including the ability to meet anticipated clinical endpoints, commencement and/or completion dates for our clinical trials, regulatory submission dates, regulatory approval dates and/or launch dates, as well as the possibility of unfavorable new clinical data and further analyses of existing clinical data; the risk that clinical trial data are subject to differing interpretations and assessments by regulatory authorities; whether regulatory authorities will be satisfied with the design of and results from our clinical studies; whether and when drug applications may be filed in particular jurisdictions for fidanacogene elaparvovec; whether and when any applications that may be pending or filed for fidanacogene elaparvovec (including the application pending with the European Commission) may be approved by regulatory authorities, which will depend on myriad factors, including making a determination as to whether the product's benefits outweigh its known risks and determination of the product's efficacy and, if approved, whether fidanacogene elaparvovec will be commercially successful; decisions by regulatory authorities impacting labeling, manufacturing processes, safety and/or other matters that could affect the availability or commercial potential of fidanacogene elaparvovec; uncertainties regarding the impact of COVID-19 on Pfizer’s business, operations and financial results; and competitive developments.

A further description of risks and uncertainties can be found in Pfizer’s Annual Report on Form 10-K for the fiscal year ended December 31, 2023, and in its subsequent reports on Form 10-Q, including in the sections thereof captioned “Risk Factors” and “Forward-Looking Information and Factors That May Affect Future Results”, as well as in its subsequent reports on Form 8-K, all of which are filed with the U.S. Securities and Exchange Commission and available at and


1 Ohmori T, Mizukami H, Ozawa K, et al. New approaches to gene and cell therapy for hemophilia. J Thromb Haemost. 2015;13(Suppl 1):S133–142.
2 Furlan R, Krishnan S, Vietri J. Patient and parent preferences for characteristics of prophylactic treatment in hemophilia. Patient Prefer Adherence. 2015;9:1687–1694.
3 U.S. Food & Drug Administration. BEQVEZ. Available at: Last accessed: May 2024. 
4 Government of Canada. Product information. December 2023. Available at: Last accessed: May 2024.
5 Centers for Disease Control and Prevention. What is hemophilia? October 2023. Available at: Last accessed: May 2024.
6 Mayo Clinic. Hemophilia. August 2023. Available at: Last accessed: May 2024.
7 World Federation of Hemophilia. Report on the Annual Global Survey 2021. October 2022. Available at: Last accessed: May 2024.


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