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Gene therapy for treating 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

PHASE1; PHASE2 · Regeneron Pharmaceuticals · NCT06379789

This study is testing a new gene therapy to see if it can help people with severe or moderately severe hemophilia B produce their own clotting factor IX and how safe it is for both adults and kids.

Quick facts

PhasePHASE1; PHASE2
Study typeInterventional
Enrollment130 (estimated)
Ages2 Years and up
SexMale
SponsorRegeneron Pharmaceuticals (industry)
Locations41 sites (Los Angeles, California and 40 other locations)
Trial IDNCT06379789 on ClinicalTrials.gov

What this trial studies

This study investigates the safety and effectiveness of a gene insertion therapy called REGV131-LNP1265 for patients with severe or moderately severe hemophilia B. It employs a two-part adaptive design, starting with dose escalation in adults to determine the recommended dose for expansion. Following this, the study will expand to include adolescents and pediatric patients, assessing the therapy's ability to enable the body to produce clotting factor IX long-term. The study will also monitor side effects and the body's immune response to the therapy.

Who should consider this trial

Good fit: Ideal candidates include individuals with a confirmed diagnosis of severe or moderately severe hemophilia B who have been on factor IX prophylaxis.

Not a fit: Patients with a history of FIX inhibitors or detectable pre-existing antibodies to the AAV8 capsid may not benefit from this therapy.

Why it matters

Potential benefit: If successful, this therapy could significantly reduce or eliminate the need for regular factor replacement therapy in hemophilia B patients.

How similar studies have performed: Other studies have shown promise with gene therapy approaches for hemophilia, indicating potential for success in this novel treatment.

Eligibility criteria

Show full inclusion / exclusion criteria 
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

Where this trial is running

Los Angeles, California and 40 other locations

Study contacts

How to participate

  1. Review the eligibility criteria above with your treating physician.
  2. Visit the official trial page on ClinicalTrials.gov for the most current contact information and recruitment status.
  3. Contact the listed study coordinator or principal investigator to request pre-screening. Pre-screening is free and never obligates you to enroll.

View on ClinicalTrials.gov →

Conditions: Hemophilia B, Severe and moderately severe congenital hemophilia B, FIX functional activity

Last reviewed 2026-05-15 by the Find a Trial editorial team. Information on this page is for educational purposes and is not medical advice. Always consult qualified healthcare professionals about clinical trial participation.