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Updated May 2026 · ClinicalTrials.gov

RECRUITINGPhase 1 / Phase 2INTERVENTIONAL

A Study to Investigate the Safety and Effectiveness of a Coagulation Factor IX Gene Insertion Therapy (REGV131-LNP1265) in Pediatric, Adolescent and Adult Participants With Hemophilia B

A Two-Part Open-Label Study of REGV131-LNP1265, A CRISPR/Cas9 Based Coagulation Factor IX Gene Insertion Therapy in Participants With Hemophilia B

A Study to Investigate the Safety and Effectiveness of a Coagulation Factor IX Gene Insertion Therapy (REGV131-LNP1265) in Pediatric, Adolescent and Adult Participants With Hemophilia B (NCT06379789) is a Phase 1 / Phase 2 interventional studying Hemophilia B, sponsored by Regeneron Pharmaceuticals. RECRUITING as of the most recent ClinicalTrials.gov update. Talk to your doctor before contacting the trial site.

Important: This information is not medical advice. Talk to your doctor about whether a clinical trial is right for you.

About This Trial

Participants in this study have a genetic mutation, specifically in the coagulation (blood clotting) Factor 9 gene that causes severe or moderately severe hemophilia B. This study is researching an experimental gene insertion therapy (the adding of a gene into your DNA) called REGV131-LNP1265, also called the "study drug". Gene insertion therapy aims to teach the body how to produce clotting factor long-term, without the need for factor replacement therapy. The main aim of this study is to find a safe and well-tolerated dose of the study drug by checking the side effects that may happen from taking it, both in the near term and over time. The study is looking at several other research questions including: * How much study drug is in the blood at different times * Whether the body makes antibodies against parts of the study drug, which could make the drug less effective or could lead to side effects. Antibodies are proteins produced by the body's immune system in response to a foreign substance * Whether the body makes antibodies against the clotting factor replacement therapy * How often factor replacement therapy is needed, both on a regular basis for prevention of bleeding, and as needed to treat bleeding events (and it if changes after taking study drug) * Whether there is a difference in 2 different methods for measuring Factor 9 activity in the blood

What Stage of Research Is This?

Phase 1 trials test a new treatment for the first time in humans, focusing on safety, dosing, and how the body processes the drug. For Hemophilia B, a Phase 1 study typically enrolls a small number of participants — often healthy volunteers or patients who have exhausted standard treatment options. Phase 1 results determine whether a treatment moves into larger Phase 2 efficacy studies.

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.

Target enrollment of 130 participants puts this in the typical range for a Phase 2-style efficacy study or a moderate Phase 3 trial in a focused Hemophilia B subpopulation. At this scale, the study has enough statistical power to detect a clear treatment effect but is not the largest cohort in the field.

Who May Be Eligible (Plain English)

Key Who May Qualify: 1. Confirmed diagnosis of severe or moderately severe hemophilia B with medical history of FIX functional activity (≤2% or \<0.02 IU/mL) or documented genotype known to produce severe hemophilia B 2. Currently taking FIX prophylaxis and previous experience with FIX therapy, as defined in the protocol 3. Participation in the lead-in period of this interventional study OR a separate lead-in study (R0000-HEMB-2187 \[NCT05568459\]) for at least 6 months for ABR data while taking FIX prophylaxis, as defined in the protocol Key Who Should NOT Join This Trial: 1. History of FIX inhibitor (clinical or laboratory-based assessment) on 2 or more occasions 2. Bethesda inhibitor titer greater than the Upper Limit of Normal (ULN) at screening 3. Detectable pre-existing antibodies to the AAV8 capsid; as measured by Enzyme-Linked ImmunoSorbent Assay (ELISA) at prescreening (or final lead-in visit, if applicable) 4. Any significant underlying liver disease such as: cholestatic liver disease, liver cirrhosis, portal hypertension, splenomegaly, hepatic encephalopathy 5. Evidence of advanced liver fibrosis or significant fatty liver, as defined in the protocol 6. Evidence of cirrhosis and/or portal hypertension as assessed by abdominal ultrasound at screening or measured within 6 months prior to the screening visit 7. History of arterial or venous thrombo-embolic events, as defined in the protocol 8. History of hypersensitivity to corticosteroids or known medical condition that requires chronic administration of corticosteroids 9. Previously received any AAV gene-based therapy or intends to receive approved or investigational AAV-based gene therapy other than REGV131-LNP1265 during the study period NOTE: Other Inclusion/Exclusion Protocol Defined Criteria Apply Always talk to your doctor about whether this trial is right for you.

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
Key Inclusion Criteria: 1. Confirmed diagnosis of severe or moderately severe hemophilia B with medical history of FIX functional activity (≤2% or \<0.02 IU/mL) or documented genotype known to produce severe hemophilia B 2. Currently taking FIX prophylaxis and previous experience with FIX therapy, as defined in the protocol 3. Participation in the lead-in period of this interventional study OR a separate lead-in study (R0000-HEMB-2187 \[NCT05568459\]) for at least 6 months for ABR data while taking FIX prophylaxis, as defined in the protocol Key Exclusion Criteria: 1. History of FIX inhibitor (clinical or laboratory-based assessment) on 2 or more occasions 2. Bethesda inhibitor titer greater than the Upper Limit of Normal (ULN) at screening 3. Detectable pre-existing antibodies to the AAV8 capsid; as measured by Enzyme-Linked ImmunoSorbent Assay (ELISA) at prescreening (or final lead-in visit, if applicable) 4. Any significant underlying liver disease such as: cholestatic liver disease, liver cirrhosis, portal hypertension, splenomegaly, hepatic encephalopathy 5. Evidence of advanced liver fibrosis or significant fatty liver, as defined in the protocol 6. Evidence of cirrhosis and/or portal hypertension as assessed by abdominal ultrasound at screening or measured within 6 months prior to the screening visit 7. History of arterial or venous thrombo-embolic events, as defined in the protocol 8. History of hypersensitivity to corticosteroids or known medical condition that requires chronic administration of corticosteroids 9. Previously received any AAV gene-based therapy or intends to receive approved or investigational AAV-based gene therapy other than REGV131-LNP1265 during the study period NOTE: Other Inclusion/Exclusion Protocol Defined Criteria Apply

Treatments Being Tested

DRUG

REGV131

Administered per the protocol before LNP1265

DRUG

LNP1265

Administered per the protocol following REGV131

Locations (20)

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.

Orthopaedic Hemophilia Treatment Center
Los Angeles, California, United States
David Geffen School of Medicine at UCLA
Los Angeles, California, United States
Children's Hospital Los Angeles
Los Angeles, California, United States
University of California Davis
Sacramento, California, United States
University California San Francisco
San Francisco, California, United States
University of Colorado Hemophilia and Thrombosis Center
Aurora, Colorado, United States
Yale HTC
New Haven, Connecticut, United States
University of Florida
Gainesville, Florida, United States
Indiana Hemophilia and Thrombosis Center
Indianapolis, Indiana, United States
Tulane University School of Medicine, Louisiana Center for Bleeding and Clotting Disorders
New Orleans, Louisiana, United States
University of Michigan
Ann Arbor, Michigan, United States
Nationwide Children's Hospital
Columbus, Ohio, United States
Children's Hospital of Philadelphia (CHOP)
Philadelphia, Pennsylvania, United States
Royal Prince Alfred Hospital, Haemophilia Treatment Centre
Camperdown, New South Wales, Australia
University of Alberta Hospital
Edmonton, Alberta, Canada
McMaster University Medical Centre - Hamilton Health Sciences
Hamilton, Ontario, Canada
McGill University Health Center (MUHC)
Montreal, Quebec, Canada
Hospices Civils de Lyon
Bron, Lyon, France
Hemostase Clinique, Institut Coeur Poumon
Lille, Nord, France
Hopital Necker
Paris, Île-de-France Region, France

How to Talk to Your Doctor About This Trial

Bring the printable summary of this trial — including the NCT ID (NCT06379789), the sponsor (Regeneron Pharmaceuticals), 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 NCT06379789 clinical trial studying?

Participants in this study have a genetic mutation, specifically in the coagulation (blood clotting) Factor 9 gene that causes severe or moderately severe hemophilia B. This study is researching an experimental gene insertion therapy (the adding of a gene into your DNA) called REGV131-LNP1265, also called the "study drug". Gene insertion therapy aims to teach the body how to produce clotting factor long-term, without the need for factor replacement therapy. The main aim of this study is to find a safe and well-tolerated dose of the study drug by checking the side effects that may happen from … The full protocol is registered on ClinicalTrials.gov and includes the primary outcome measures, eligibility criteria, and study endpoints.

Who can participate in NCT06379789?

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 NCT06379789?

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 NCT06379789. Maintained by the National Library of Medicine at NIH. Public domain. Cite as: "TrialFinderData. NCT06379789. 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 2026-05-08 · Data from ClinicalTrials.gov.