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One-Time gene therapy could free hemophilia patients from frequent infusions

NCT ID NCT03588299

Disease control Sponsor: Bayer Source: ClinicalTrials.gov ↗

What the study statuses mean

This study's is highlighted.

Recruitment status, easiest to join first

Recruiting now
This trial is taking on new participants right now.
Not yet recruiting
Registered, but not yet taking participants.
By invitation only
Not open to general applications. Only people the study team invites can take part.
Paused
Paused for now. It may or may not start again.
Ongoing This study
Running, but no longer taking on new participants.
Completed
The trial has finished. Results may not be published yet.
Stopped early
Stopped early, before it reached the end. That can be for many reasons, including safety.
Cancelled
Cancelled before anyone took part.

Expanded access (not trials)

Expanded access
Not a trial. This treatment can be requested outside a study, case by case, for people who qualify.
Expanded access (paused)
Not a trial. The treatment can normally be requested outside a study, but is unavailable right now.
Expanded access (ended)
Not a trial. The treatment could once be requested outside a study, but no longer can.
Approved
The treatment has been approved, so it is available normally rather than through this programme.

When the status isn't known

Details not published
The full record has not been published yet, so there is little to show here.
Status unknown
This status has not been confirmed recently, so it may be out of date.

First seen Jun 24, 2026 · Last updated Jul 07, 2026 · Updated 4 times

Summary

This study tests a one-time gene therapy called BAY2599023 for adults with severe hemophilia A. The therapy uses a harmless virus to deliver a working copy of the factor VIII gene, so the body can produce its own clotting factor. The trial involves 11 participants and aims to find the safest and most effective dose. If it works, it may reduce or eliminate the need for regular clotting factor infusions.

What this could mean

Our plain-language read of the trial. This is informational only, not medical advice or a prediction.

Active substance
BAY2599023 (DTX201) – a gene therapy using a modified virus to deliver a working copy of the factor VIII gene
What this could lead to
If successful, this could allow people with severe hemophilia A to produce their own clotting factor, reducing or eliminating the need for regular infusions.
What could go wrong
This is an early, small trial (11 people) focused on safety and dosing. Gene therapy may not work for everyone, and long-term effects are unknown. There is a risk of immune reactions or the therapy not producing enough clotting factor.

This is an AI summary of the original study and may miss details. Read our disclaimer.

Study facts

What this study's own registry entry says, in plain language.

Phase

Phase 1/2

Runs two stages together: safety and dose first, then whether the treatment works.

Participants

11 people

The number who actually took part.

Started

Nov 2018

Expected to finish

Sep 2026

An estimate. End dates often move.

Lead sponsor

A company

The lead sponsor is a pharmaceutical, biotech, or medical-device company.

Who can take part

This study's own entry requirements. Only the study team can say for certain whether you qualify.

Ages

18 years and older

Sex

Male participants only

Healthy volunteers

Not accepted

This study is not open to healthy volunteers. The entry requirements below say who it is open to.

Show the full entry requirements

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Inclusion Criteria: * Males age 18 years or older. * Confirmed diagnosis of hemophilia A as evidenced by their medical history with plasma FVIII activity levels \< 1% of normal or at screening. * Have \>150 exposure days (EDs) to FVIII concentrates (recombinant or plasma-derived). If on prophylaxis, are required to be willing to stop prophylactic treatment at specified time points throughout the study or If on-demand: should have had \> 4 bleeding events in the last 52 weeks \- Agree to use reliable barrier contraception. Exclusion Criteria: * History of allergic reaction to any FVIII product. * Clinically relevant findings in the physical examination considered critical by the treating physician, including obesity with BMI \> 35 kg/m\*2 * Current evidence of measurable inhibitor against factor VIII, prior history of inhibitors to FVIII protein or clinical history suggestive of inhibitor. * Evidence of active hepatitis B or C. * Currently on antiviral therapy for hepatitis B or C. * Significant underlying liver disease. * Serological evidence of HIV-1 or HIV-2 with CD4 counts ≤200/mm\*3; HIV+ and stable participants with CD4 count \>200/mm\*3 and undetectable viral load are eligible to enroll. * Detectable antibodies reactive with AAVhu37capsid. * Participant with another bleeding disorder that is different from hemophilia A (e.g., von Willebrand disease, hemophilia B). * Participated in a gene transfer trial within the last 52 weeks or in a clinical trial with an investigational product within the last 12 weeks. * Known or suspected hypersensitivity or allergic reaction to trial product(s) or related FVIII products or any component of BAY2599023 (DTX201), or a contraindication to prednisolone

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Conditions

The condition(s) this trial relates to.

hemophilia A severe hemophilia A

As listed by the trial registrant

The condition terms exactly as the trial's registrant entered them.

Hemophilia A

Contacts and locations

Locations

  • APHP-Hopital Necker Enfants malades

    Paris, Île-de-France Region, 75015, France

  • Academisch Medisch Centrum (AMC)

    Amsterdam, North Holland, 1105 AZ, Netherlands

  • Arkansas Children's Hospital - Hematology / Oncology

    Little Rock, Arkansas, 72202, United States

  • C.S. Mott Children's Hospital - Hematology / Oncology

    Ann Arbor, Michigan, 48109, United States

  • CHU Rennes - Hopital Pontchaillou

    Rennes, Brittany Region, 35033, France

  • Erasmus Medisch Centrum

    Rotterdam, South Holland, 3015 CE, Netherlands

  • Manchester Royal Infirmary

    Manchester, Greater Manchester, M13 9WL, United Kingdom

  • SHATHD Spec. Hospi. for Active Treatm. of Haematol. Dis. EAD

    Sofia, Sofia City Province, 1756, Bulgaria

  • UW Health Carbone Cancer Center

    Madison, Wisconsin, 53792, United States

  • Universitair Medisch Centrum Groningen

    Groningen, 9713 GZ, Netherlands

  • University Medical Center Utrecht

    Utrecht, 3584 CX, Netherlands

  • Universitätsklinikum des Saarlandes

    Homburg, Saarland, 66421, Germany

  • Vivantes Klinikum im Friedrichshain

    Berlin, 10249, Germany

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