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

What this study is about

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

Who can join (things the study team will check)

✅ You may be able to join if…

• 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
• Currently taking FIX prophylaxis and previous experience with FIX therapy, as defined in the protocol
• 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

🚫 You may not be able to join if…

• History of FIX inhibitor (clinical or laboratory-based assessment) on 2 or more occasions
• Bethesda inhibitor titer greater than the Upper Limit of Normal (ULN) at screening
• 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)
• Any significant underlying liver disease such as: cholestatic liver disease, liver cirrhosis, portal hypertension, splenomegaly, hepatic encephalopathy
• Evidence of advanced liver fibrosis or significant fatty liver, as defined in the protocol
• Evidence of cirrhosis and/or portal hypertension as assessed by abdominal ultrasound at screening or measured within 6 months prior to the screening visit
• History of arterial or venous thrombo-embolic events, as defined in the protocol
• History of hypersensitivity to corticosteroids or known medical condition that requires chronic administration of corticosteroids
• 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

Where this trial is running

• 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

+ 32 more sites.

Who to contact

Clinical Trials Administrator · 844-734-6643 · clinicaltrials@regeneron.com

It's completely normal to call and ask questions before deciding anything. Mention the study ID: NCT06379789.