Updated June 2026 · ClinicalTrials.gov
Efficacy and Safety of GNT0003 Following Imlifidase Pre-treatment in Severe Crigler-Najjar Syndrome
An Open-label, Phase 2 Trial to Evaluate the Efficacy and Safety of a Single Intravenous Administration of GNT0003 (an Adeno-associated Viral (AAV) Vector Expressing the UGT1A1 Transgene) Following Imlifidase Pre-treatment in Adult Participants With Severe Crigler-Najjar Syndrome (CNS) Requiring Daily Phototherapy and Presenting Pre-existing Anti-AAV8 Antibodies
Efficacy and Safety of GNT0003 Following Imlifidase Pre-treatment in Severe Crigler-Najjar Syndrome (NCT06518005) is a Phase 2 interventional studying Crigler-Najjar Syndrome, sponsored by Genethon. RECRUITING as of the most recent ClinicalTrials.gov update. Talk to your doctor before contacting the trial site.
About This Trial
Clinical trial rationale: CNS is an ultra-rare (\<1/1 million newborns), autosomal recessive disorder of bilirubin conjugation caused by mutation in the gene coding for uridine 5'-diphosphate glucuronosyltransferase (UGT1A1), that causes the accumulation of neurotoxic unconjugated bilirubin (UCB). Reduction of UCB is managed with phenobarbital in mild CNS, and daily phototherapy in severe CNS. There is no authorized curative medical treatment for CNS. Liver transplantation is currently the only curative treatment for severe CNS. GNT0003 is a genetically modified recombinant (r) viral vector composed of the AAV8 viral capsid carrying the UGT1A1 transgene which aims to correct the dysfunction of the mutated gene by achieving durable expression of a functional copy of the affected gene. Imlifidase (IgG-degrading enzyme) has demonstrated its efficacy in highly sensitized adult kidney transplant patients. To give participants with pre-existing anti-AAV8 antibodies access to gene therapy treatments, this trial aims to demonstrate the safety and efficacy of GNT0003 following imlifidase pre-treatment in adult participants with severe CNS requiring daily phototherapy and presenting with pre-existing anti-AAV8 antibodies. Primary objective: to assess efficacy of a single intravenous administration of GNT0003 following imlifidase pre-treatment in participants with severe CNS requiring phototherapy and pre-existing AAV8 antibodies Secondary objective: to collect data on safety and tolerability of GNT0003 and imlifidase, efficacy of imlifidase, pharmacokinetic and pharmacodynamic profile of GNT0003, and Quality of Life. The trial will include 3 parts: * A baseline period for at least 3 months * A treatment period * A follow-up period: * Initial post-treatment follow-up over 48 weeks * Long-term follow-up for 4 additional years This trial will be conducted in accordance with the International Conference on Harmonization Guideline for Good Clinical Practice and the Declaration of Helsinki. Participants must be consented using the approved Informed Consent Form before any procedures specified in the protocol are performed.
What Stage of Research Is This?
Phase 2 trials evaluate whether a treatment actually works against Crigler-Najjar Syndrome and continue monitoring side effects. Phase 2 enrolls larger groups (typically 100–300 patients) and produces the first real efficacy signal. A successful Phase 2 readout is what unlocks the much larger Phase 3 confirmatory trials needed for FDA approval.
This trial is currently recruiting participants. The sponsor has registered the study with ClinicalTrials.gov as actively enrolling, which means new applicants who meet the eligibility criteria can be considered for screening. Trial status can change between updates — confirm current recruiting status with the study contact before traveling for a screening visit.
With a target enrollment of 3 participants, this is a small study — typical of early-phase research, rare-disease trials, or pilot studies designed to generate preliminary signal before a larger study is launched.
Who May Be Eligible (Plain English)
These are translations of the protocol\'s inclusion and exclusion criteria, simplified for patients and caregivers. The original clinical text appears below. Eligibility is ultimately confirmed by the trial site\'s screening process — this summary is a starting point for a conversation with your doctor, not a final determination.
Original Eligibility Criteria
View original clinical language
Treatments Being Tested
Imlifidase
Imlifidase: single administration (dose is confidential), Lyophilized powder for concentrate for solution for infusion
GNT0003
GNT0003: single administration 5E+12 VG/kg, Sterile concentrate for solution for infusion
Locations (1)
Trial sites listed on ClinicalTrials.gov for this study. Site activation status can vary — confirm with the specific site before traveling for a screening visit.
How to Talk to Your Doctor About This Trial
Bring the printable summary of this trial — including the NCT ID (NCT06518005), the sponsor (Genethon), and the key eligibility criteria — to your next appointment. Your doctor can review the inclusion and exclusion criteria against your medical history, lab values, and current treatments to assess whether you are likely to qualify. They can also help you weigh whether trial participation makes sense alongside your existing care plan.
Useful questions to walk through together: What does the trial protocol require beyond standard care? How long is the active treatment phase, and how long is follow-up? Are there study visits at sites I can reach? Who pays for the trial-specific procedures, and who pays for standard-of-care portions? See our 25 questions to ask about clinical trials guide for a more complete checklist.
Authoritative Sources
The official record for this trial lives on ClinicalTrials.gov — the federal registry maintained by the National Library of Medicine at NIH. For background on how this trial fits into the FDA approval pathway, see the FDA drug approval process. For oncology-specific guidance for patients considering trials, the National Cancer Institute publishes patient-oriented overviews. International trial registries are aggregated by the WHO ICTRP.
Frequently Asked Questions
What is the NCT06518005 clinical trial studying?
Clinical trial rationale: CNS is an ultra-rare (\<1/1 million newborns), autosomal recessive disorder of bilirubin conjugation caused by mutation in the gene coding for uridine 5'-diphosphate glucuronosyltransferase (UGT1A1), that causes the accumulation of neurotoxic unconjugated bilirubin (UCB). Reduction of UCB is managed with phenobarbital in mild CNS, and daily phototherapy in severe CNS. There is no authorized curative medical treatment for CNS. Liver transplantation is currently the only curative treatment for severe CNS. GNT0003 is a genetically modified recombinant (r) viral vecto… The full protocol is registered on ClinicalTrials.gov and includes the primary outcome measures, eligibility criteria, and study endpoints.
Who can participate in NCT06518005?
Eligibility for this trial depends on the specific inclusion and exclusion criteria set by the sponsor. The plain-English summary above translates the most important criteria into accessible language; the official clinical text is preserved in the collapsible section underneath. Whether you fit any specific trial is a medical decision your doctor needs to confirm — bring the trial information to your treating physician for a full review against your medical history.
How do I contact the trial site for NCT06518005?
Contact information registered with ClinicalTrials.gov is shown in the sidebar of this page. Before reaching out, confirm with your treating physician that this trial is appropriate for your situation. The trial site will then walk you through the screening process to determine final eligibility.
Is participating in a clinical trial safe?
Clinical trials in the United States are regulated by the FDA and overseen by Institutional Review Boards (IRBs) that review the protocol for safety. Risk varies by trial — Phase 1 studies test new treatments in humans for the first time, while Phase 3 trials use treatments that have already passed earlier safety screening. The informed consent document for any specific trial details the known risks and what to expect. Discuss those risks with your physician before deciding whether to participate.
Where can I verify the data on this page?
Every detail on this page comes directly from the ClinicalTrials.gov API. Click "View on ClinicalTrials.gov" in the sidebar to see the official, unmodified record. The federal record is always authoritative; this page is a structured presentation with a plain-English eligibility translation. For background on how clinical trials are regulated, see the FDA drug approval process documentation.
How This Page Is Built
Every field on this page is pulled directly from the ClinicalTrials.gov API v2 — no estimates, no proxies. The plain-English eligibility translation is generated from the original protocol text and reviewed for fidelity to the underlying clinical criteria. The original clinical text remains visible in the collapsible section above so users and clinicians can verify the translation. Read the full methodology for the data pipeline and known limitations.
Source: ClinicalTrials.gov API v2 record for NCT06518005. Maintained by the National Library of Medicine at NIH. Public domain. Cite as: "TrialFinderData. NCT06518005. Data: ClinicalTrials.gov."
Medical disclaimer: This page is informational, not medical advice. Talk to your doctor about whether a clinical trial is right for you.
Last updated 2026-06-26 · Data from ClinicalTrials.gov.