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A study on the long-term safety and effectiveness of giroctocogene fitelparvovec or fidanacogene elaparvovec in patients with hemophilia A or hemophilia B

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What is this trial about?

A plain-language summary of the goals, design and what participants do

This study focuses on individuals living with Hemophilia A or Hemophilia B. These are rare bleeding disorders where the blood does not clot properly due to a lack of specific proteins needed for clotting. The purpose of this study is to describe the long-term safety and effectiveness of a single-dose treatment previously received by participants. The medications being observed are fidanacogene elaparvovec, used for those with Hemophilia A, and giroctocogene fitelparvovec, used for those with Hemophilia B.

The treatment involves gene therapy, which is a method used to introduce genetic material into cells to help the body produce the missing clotting proteins. Participants in this study will be monitored over a long period of time to observe how the body responds to these treatments. This includes tracking the level of clotting factor, which is the protein responsible for stopping bleeding, and checking for any potential issues such as thromboembolic events, which are blood clots that can travel through the bloodstream, or changes in liver health.

The research process

The trial runs in 2 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    <b>initial observation</b>

    The study begins after a single dose of either fidanacogene elaparvovec (for hemophilia A) or giroctocogene fitelparvovec (for hemophilia B) has already been administered through an intravenous infusion, which is a liquid medicine delivered directly into a vein.

  2. Step 2

    <b>long-term monitoring</b>

    Participation involves long-term monitoring to track safety and how well the previous treatment works over time.

    The process includes tracking factor activity levels, which measures how effectively the blood can clot.

    Health assessments are conducted to monitor for liver abnormalities, liver cancer, or blood clots.

    The frequency of bleeding episodes and the need for additional clotting factor treatments are recorded.

    The durability, or how long the effects of the gene therapy last, is observed throughout the study period.

Who can join the trial?

3 criteria

  • You must be a person who has already received one of two specific gene therapies, called giroctocogene fitelparvovec or fidanacogene elaparvovec, during a previous study organized by Pfizer.
  • You must be male.
  • You must be a child, as the age range specified for this study is for younger participants.

Who cannot join the trial?

1 criterion

  • There are no specific reasons listed that would prevent a person from participating in this study.
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Investigated drugs

  • Fidanacogene elaparvovec

    is a gene therapy designed to help people with Hemophilia A. It is given through an IV infusion to help the body produce the blood clotting factor that is missing or not working correctly due to the condition.

  • Giroctocogene fitelparvovec

    is a gene therapy designed to help people with Hemophilia B. It is given through an IV infusion to help the body produce the blood clotting factor that is missing or not working correctly due to the condition.

What is already known about the treatment

  • fidanacogene elaparvovec

    This medication is an intravenous solution used to treat people with severe to moderately severe hemophilia B. It is an experimental gene therapy that works by delivering a healthy piece of genetic material into the body to help the liver produce the missing blood-clotting protein. By correcting this internal process at a molecular level, the treatment aims to help the blood clot more effectively and reduce the need for regular infusions.

  • giroctocogene fitelparvovec

    This medicine is administered as an intravenous infusion to treat patients with hemophilia. As a specialized gene therapy, it works by introducing a functional gene into the patient's cells to trigger the natural production of essential clotting factors. This approach targets the root cause of the bleeding disorder at the cellular level to provide long-lasting improvements in blood clotting ability.

Investigated diseases

  • Hemophilia A

    This is a genetic bleeding disorder caused by a deficiency or lack of clotting factor VIII. Because this protein is missing, the blood cannot clot properly when an injury occurs. Over time, the condition can lead to frequent and spontaneous bleeding into joints and muscles. This repeated bleeding can cause long-term damage to the affected areas.

  • Hemophilia B

    This condition is a genetic disorder resulting from a deficiency of clotting factor IX. The lack of this specific protein prevents the blood from forming clots effectively. As the disease progresses, individuals may experience bleeding episodes in various parts of the body. These episodes can occur following minor injuries or even without a clear cause.

Trial detailsLast updated 2 Oct 2026
Age18+ yearsPhasePhase IIITrial ID2025-523660-21-00Protocol codeC0371017Estimated enrolment187 patientsSponsorPfizer Inc.

sourced from the EU Clinical Trials Register and site verification

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