Bayer presents positive data at ISTH 2020 from its first-in-human Factor VIII gene therapy study in hemophilia A

During ISTH 2020, Bayer announced positive results and successful proof-of-concept from the first-in-human study Phase 1/2 trial for BAY 2599023, its investigational Factor VIII gene therapy in hemophilia A. The data show initial safety and efficacy in six patients treated in three cohorts with increasing dose levels with measurable, stable expression of endogenous Factor VIII and indications of hemostatic efficacy.

BAY 2599023 leverages a specific gene therapy approach using an adeno-associated virus (AAV) vector as shuttle to transport the Factor VIII gene into the body. The AAV vector is uniquely designed to target liver cells, as these constitute a major production site of endogenous Factor VIII. In some patients, viral vectors can cause innate or adaptive immune responses. While this is not dangerous, some immune responses may lead to a decreased efficiency of gene transfer or elimination of the transduced gene over time. Exploring novel capsid vectors for gene therapy in the hemophilia population may provide treatments for those who have immunity to other vectors.

“We’re delighted with these positive data and we’re encouraged to see how they will contribute to our ambition to provide a viable gene therapy option for people with hemophilia A” said Dr. Francesca Ferrante, Global Clinical Lead of Bayer’s Factor VIII gene therapy program. “The long-term aim for hemophilia treatments is to achieve stable and close to normal expression levels of Factor VIII that can be sustained over a long period of time. We at Bayer are committed to continually pursuing novel therapies which can deliver these long-term results for people living with hemophilia.”

The interim results are encouraging for BAY 2599023 but further studies are required to evaluate the safety and efficacy of this investigational FVIII gene therapy.

For more information on Bayer’s gene therapy program in hemophilia A, please click here

Presentation details: Steve Pipe, Principal Investigator, presents latest data at ISTH 2020 (accessible for registered healthcare providers only).

Access abstract: click here (abstract number 10363)

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Pamela Cohen, Innovation Communications

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About Bayer in Hemophilia
Bayer is driven by helping people with hemophilia thrive. We have a deep understanding of the evolving needs and aspirations of people with hemophilia, established over 30 years of partnering with the hemophilia community. FVIII replacement therapy is the standard of care to stop or prevent bleeding. Bayer’s portfolio of FVIII treatments offers people with hemophilia A across all stages of life a treatment to suit their individual needs and lifestyles. We work together with researchers, healthcare professionals and patient groups to build a strong community and help people with hemophilia to live fulfilling lives. Bayer is passionate about spearheading research and investing in developing the next generation of therapies, such as Gene Therapy and TFPI and solutions to help people with hemophilia thrive in the future.

About Bayer
Bayer is a global enterprise with core competencies in the life science fields of health care and nutrition. Its products and services are designed to benefit people by supporting efforts to overcome the major challenges presented by a growing and aging global population. At the same time, the Group aims to increase its earning power and create value through innovation and growth. Bayer is committed to the principles of sustainable development, and the Bayer brand stands for trust, reliability and quality throughout the world. In fiscal 2019, the Group employed around 104,000 people and had sales of 43.5 billion euros. Capital expenditures amounted to 2.9 billion euros, R&D expenses to 5.3 billion euros. For more information, go to

Forward-Looking Statements
This release may contain forward-looking statements based on current assumptions and forecasts made by Bayer management. Various known and unknown risks, uncertainties and other factors could lead to material differences between the actual future results, financial situation, development or performance of the company and the estimates given here. These factors include those discussed in Bayer’s public reports which are available on the Bayer website at The company assumes no liability whatsoever to update these forward-looking statements or to conform them to future events or developments.

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