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Study on Gene Therapy GNT0003 for Patients with Severe Crigler-Najjar Syndrome Requiring Phototherapy

Verified siteRegistered drugNo placebo
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What is this trial about?

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

This clinical trial is focused on studying a rare genetic condition called Crigler-Najjar syndrome. This condition affects the liver's ability to process a substance called bilirubin, leading to its buildup in the body. Patients with severe forms of this syndrome often require daily light therapy, known as phototherapy, to help manage bilirubin levels. The study is testing a new treatment called GNT0003, which is a type of gene therapy. This treatment involves using a specially designed virus to deliver a healthy version of the gene responsible for processing bilirubin directly into the liver cells. The goal is to help the liver function more normally and reduce the need for phototherapy.

The purpose of the study is to evaluate the safety and effectiveness of a single dose of GNT0003 given through an intravenous infusion, which means it is delivered directly into the bloodstream. The study is divided into two parts. The first part focuses on determining the safest dose of the treatment, while the second part assesses how well the treatment works at the selected dose. Participants will receive the treatment and be monitored over several weeks to see how their bodies respond. This includes checking for any side effects and measuring changes in bilirubin levels.

Throughout the study, participants will have regular check-ups, including blood tests and other assessments, to ensure their safety and to track the treatment's impact on their health. The study aims to provide valuable information on whether this gene therapy can offer a new way to manage Crigler-Najjar syndrome and improve the quality of life for those affected by this condition. The trial is expected to continue until 2028, allowing researchers to gather comprehensive data on the long-term effects of the treatment.

The research process

The trial runs in 5 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Joining the study

    Upon joining the study, eligibility is confirmed based on specific criteria, including a diagnosis of severe Crigler-Najjar syndrome and the need for daily phototherapy for at least 6 hours.

    Molecular confirmation of mutations in the UGT1A1 gene is required through DNA sequencing.

  2. Step 2

    Dose escalation phase

    The initial phase involves assessing the safety and tolerability of a single intravenous dose of GNT0003, a gene therapy product.

    Monitoring occurs for treatment-emergent adverse events and changes in laboratory parameters, vital signs, and physical examination up to Week 17.

  3. Step 3

    Confirmatory phase

    This phase evaluates the effectiveness of the selected dose of GNT0003 in reducing serum total bilirubin levels to 300 µmol/L or less by Week 48.

    Patients are observed for the absence of phototherapy from Week 16 onwards.

  4. Step 4

    Monitoring and follow-up

    Throughout the trial, regular assessments are conducted to monitor the clearance of the GNT0003 vector from blood, urine, saliva, and feces.

    Changes in health-related quality of life are measured using specific questionnaires, including SF-36 for adults and PedsQL for children, up to Week 48.

  5. Step 5

    Completion of the trial

    The trial is expected to conclude by October 2037, with ongoing evaluations of the long-term safety and efficacy of the treatment.

Who can join the trial?

5 criteria

  • Patients must have **severe Crigler-Najjar syndrome**, which is a rare liver disorder, and need daily **phototherapy** for at least 6 hours a day. Phototherapy is a treatment using light to help reduce high levels of a substance called bilirubin in the blood.
  • There must be **molecular confirmation** of changes, known as mutations, in the **UGT1A1 gene**. This is done through a process called **DNA sequencing**, which is a test to look at the genetic material.
  • Participants can be of any gender, meaning both females and males are eligible.
  • The study includes people from different age groups, specifically children, adolescents, and adults.
  • The study may include individuals considered as a **vulnerable population**, which means they might need special protection or care.

Who cannot join the trial?

4 criteria

  • Patients who do not have severe Crigler-Najjar syndrome that requires light treatment called phototherapy cannot participate. Phototherapy is a treatment that uses light to help reduce high levels of a substance called bilirubin in the blood.
  • Patients who are not within the specified age range for the study cannot participate. The study includes certain age groups, so if a patient is too young or too old, they may not be eligible.
  • Patients who are not able to safely receive the study treatment due to other health conditions or risks cannot participate. This is to ensure the safety of all participants.
  • Patients who are not able to follow the study procedures or attend all required visits cannot participate. This is important for collecting accurate study data.
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Investigated drugs

GNT0003 is an experimental therapy being tested in this clinical trial. It is an adeno-associated viral vector that carries the UGT1A1 transgene. This therapy is designed to help patients with severe Crigler-Najjar syndrome, a condition that affects the liver's ability to process a substance called bilirubin. The goal of GNT0003 is to introduce a functional version of the UGT1A1 gene into the patient's liver cells, which may help reduce the need for phototherapy, a common treatment for this condition.

What is already known about the treatment

GNT0003 – This medication is administered as an intravenous injection and is currently being studied in clinical trials for its safety and effectiveness. It is designed for patients with severe Crigler-Najjar syndrome who require phototherapy. The main therapeutic indication is to reduce the need for phototherapy in these patients. GNT0003 works by using an adeno-associated viral vector to deliver the UGT1A1 transgene, which helps in the breakdown of bilirubin, a substance that can build up to dangerous levels in these patients. It is classified as a gene therapy product.

Investigated diseases

Crigler-Najjar Syndrome – This is a rare genetic disorder characterized by the inability of the liver to properly process bilirubin, a substance produced by the breakdown of red blood cells. In severe cases, individuals require regular phototherapy to help reduce bilirubin levels in the blood. The condition is caused by a deficiency in the enzyme responsible for converting bilirubin into a form that can be easily excreted from the body. Without treatment, bilirubin can accumulate to toxic levels, potentially leading to neurological damage. The disease is typically diagnosed in infancy or early childhood and requires ongoing management to prevent complications.
Trial detailsLast updated 7 Oct 2026
Age18+ yearsPhasePhase I/IITrial ID2023-507007-60-00Protocol codeGNT-012-CRIGEstimated enrolment17 patientsSponsorGenethon

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