Recruiting
Phase 1
Phase 2

REGV131-LNP1265

Sponsor:

Regeneron Pharmaceuticals

Code:

NCT06379789

Conditions

Hemophilia B

Eligibility Criteria

Sex: Male

Age: 2+

Healthy Volunteers: Not accepted

Interventions

REGV131

LNP1265

Study Details

Brief summary:

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

Conditions

Hemophilia B

Study ID

NCT06379789

Start date

Sep 11, 2024

Status verified date

Aug, 2026

Completion date

Aug 14, 2047

Anticipated

Primary completion date

Aug 14, 2034

Anticipated

Eligibility Criteria

Eligibility Criteria

Sex: Male

Age: 2+

Healthy Volunteers: Not accepted

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

Study Design

Enrollment

130 participants

Anticipated

Allocation

Non randomized

Intervention Model

Sequential

Primary purpose

Treatment

Interventions and Outcome Measures

Arms

experimental: Part 1: Cohort 1 Dose Escalation for RDE

Starting dose to determine the RDE of REGV131-LNP1265 and further assess the safety, tolerability, and FIX functional activity data at the RDE

experimental: Part 1: Cohort 2 Dose Escalation for RDE

Dose 2 of ascending dose level cohorts to determine the RDE of REGV131-LNP1265 and further assess the safety, tolerability, and FIX functional activity data at the RDE

experimental: Part 1: Cohort 3 Dose Escalation for RDE

Dose 3 of ascending dose level cohorts to determine the RDE of REGV131-LNP1265 and further assess the safety, tolerability, and FIX functional activity data at the RDE

experimental: Part 1: Cohort 4 Dose Escalation for RDE

Dose 4 of ascending dose level cohorts to determine the RDE of REGV131-LNP1265 and further assess the safety, tolerability, and FIX functional activity data at the RDE

experimental: Part 2: Dose Expansion A

Participants ≥18 Years of Age will receive the RDE of REGV131-LNP1265 determined by Part 1

experimental: Part 2: Dose Expansion B

Participants ≥12 to <18 Years of Age will receive the administered weight-adjusted RDE of REGV131-LNP1265 determined by Part 1

experimental: Part 2: Dose Expansion C

Participants ≥2 to <12 Years of Age will receive the administered weight-adjusted RDE of REGV131-LNP1265 determined by Part 1

Interventions

REGV131

Administered per the protocol before LNP1265

LNP1265

Administered per the protocol following REGV131

Primary outcome measure

  • Occurrence of Treatment-Emergent Adverse Events (TEAEs) [ Time Frame: Up to 2 Years ]
  • Severity of TEAEs [ Time Frame: Up to 2 Years ]
  • Coagulation Factor IX (FIX) functional activity measured using the chromogenic substrate assay [ Time Frame: Up to 2 Years ]
  • Change in FIX functional activity in plasma, measured using the chromogenic substrate assay [ Time Frame: Up to 2 Years ]
  • Annualized Bleeding Rate (ABR) following sustained FIX functional activity among participants receiving the RDE [ Time Frame: Up to 2 Years ]
  • Occurrence of Serious Adverse Events (SAEs) [ Time Frame: Through Long Term Follow Up (LTFU), Up to 15 Years ]
  • Severity of SAEs [ Time Frame: Through LTFU, Up to 15 Years ]
  • Occurrence of Adverse Event of Special Interests (AESIs) [ Time Frame: Through LTFU, Up to 15 Years ]
  • Severity of AESIs [ Time Frame: Through LTFU, Up to 15 Years ]
  • Occurrence of clinically meaningful Adverse Events (AEs) [ Time Frame: Through LTFU, Up to 15 Years ]
  • Severity of clinically meaningful AEs [ Time Frame: Through LTFU, Up to 15 Years ]

Central Contacts and Locations

Central contacts

Clinical Trials Administrator

844-734-6643clinicaltrials@regeneron.com

Locations

Orthopaedic Hemophilia Treatment Center

Recruiting

Los Angeles, California, United States, 90007

David Geffen School of Medicine at UCLA

Recruiting

Los Angeles, California, United States, 90024

Children's Hospital Los Angeles

Recruiting

Los Angeles, California, United States, 90027

University of California Davis

Recruiting

Sacramento, California, United States, 95817

University California San Francisco

Recruiting

San Francisco, California, United States, 94143

University of Colorado Hemophilia and Thrombosis Center

Recruiting

Aurora, Colorado, United States, 80045

Yale HTC

Recruiting

New Haven, Connecticut, United States, 06510

University of Florida

Recruiting

Gainesville, Florida, United States, 32610

Indiana Hemophilia and Thrombosis Center

Recruiting

Indianapolis, Indiana, United States, 46260

Tulane University School of Medicine, Louisiana Center for Bleeding and Clotting Disorders

Recruiting

New Orleans, Louisiana, United States, 70112

University of Michigan

Recruiting

Ann Arbor, Michigan, United States, 48109

Nationwide Children's Hospital

Recruiting

Columbus, Ohio, United States, 43205

Children's Hospital of Philadelphia (CHOP)

Recruiting

Philadelphia, Pennsylvania, United States, 19104

Vanderbilt University Medical Center

Recruiting

Nashville, Tennessee, United States, 37232

University of Texas Health Science Center at Houston

Recruiting

Houston, Texas, United States, 77030

University of Alberta Hospital

Recruiting

Edmonton, Alberta, Canada, T6G 2B7

McMaster University Medical Centre - Hamilton Health Sciences

Recruiting

Hamilton, Ontario, Canada, L8N 3Z5

McGill University Health Center (MUHC)

Recruiting

Montreal, Quebec, Canada, H4J 3A1

More Information

Sponsor

Regeneron Pharmaceuticals

Last update posted

Aug 5, 2026

Last verified

Aug, 2026

Keywords

  • Severe and moderately severe congenital hemophilia B
  • FIX functional activity

Trial information was received from ClinicalTrials.gov and was last updated on 2026-09-09. This information was provided to ClinicalTrials.gov by Regeneron Pharmaceuticals on 2026-08-05.