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REGV131

Phase 1

Hemophilia B | Small molecule | Hematology |Regeneron Pharmaceuticals, Inc.|Last Updated: Jul 8, 2026

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Trial Design
CONTROLLEDDMC
Total Trials1
Total Enrollment130
FDA Designations
No designations recorded
Clinical trial landscape

REGV131 · 1 trial · 1 indication

Phase 1 1
NCT06379789A 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 BHemophilia B
RECRUITING130 Analytics
PHASE1RECRUITING
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
Hemophilia BUnlock trial analytics
Study Endpoints
Primary Endpoints
Occurrence of Treatment-Emergent Adverse Events (TEAEs)
Up to 2 Years

Part 1, 2B, and 2C

Severity of TEAEs
Up to 2 Years

Part 1, 2B, and 2C

Coagulation Factor IX (FIX) functional activity measured using the chromogenic substrate assay
Up to 2 Years

Part 1

Change in FIX functional activity in plasma, measured using the chromogenic substrate assay
Up to 2 Years

Part 2A, 2B, and 2C

Annualized Bleeding Rate (ABR) following sustained FIX functional activity among participants receiving the RDE
Up to 2 Years

Part 2A, 2B, and 2C

Occurrence of Serious Adverse Events (SAEs)
Through Long Term Follow Up (LTFU), Up to 15 Years

LTFU Period for Part 1, 2A, 2B, and 2C

Severity of SAEs
Through LTFU, Up to 15 Years

LTFU Period for Part 1, 2A, 2B, and 2C

Occurrence of Adverse Event of Special Interests (AESIs)
Through LTFU, Up to 15 Years

LTFU Period for Part 1, 2A, 2B, and 2C

Severity of AESIs
Through LTFU, Up to 15 Years

LTFU Period for Part 1, 2A, 2B, and 2C

Occurrence of clinically meaningful Adverse Events (AEs)
Through LTFU, Up to 15 Years

LTFU Period for Part 1, 2A, 2B, and 2C

Severity of clinically meaningful AEs
Through LTFU, Up to 15 Years

LTFU Period for Part 1, 2A, 2B, and 2C

Secondary Endpoints
Change in FIX functional activity in plasma measured using the chromogenic substrate assay
Up to 2 Years
ABR following sustained FIX functional activity among participants receiving the RDE
Through LTFU, Up to 15 Years
FIX functional activity in plasma over time during the study period using the chromogenic substrate assay
Through LTFU, Up to 10 Years
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Study Design & Arms
AllocationNON_RANDOMIZED
MaskingNONE
ModelSEQUENTIAL
PurposeTREATMENT
Treatment Arms
ArmTypeDescription
Part 1: Cohort 1 Dose Escalation for RDEEXPERIMENTALStarting dose to determine the RDE of REGV131-LNP1265 and further assess the safety, tolerability, and FIX functional activity data at the RDE
Part 1: Cohort 2 Dose Escalation for RDEEXPERIMENTALDose 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
Part 1: Cohort 3 Dose Escalation for RDEEXPERIMENTALDose 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
Part 1: Cohort 4 Dose Escalation for RDEEXPERIMENTALDose 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
Part 2: Dose Expansion AEXPERIMENTALParticipants ≥18 Years of Age will receive the RDE of REGV131-LNP1265 determined by Part 1
Part 2: Dose Expansion BEXPERIMENTALParticipants ≥12 to \<18 Years of Age will receive the administered weight-adjusted RDE of REGV131-LNP1265 determined by Part 1
Part 2: Dose Expansion CEXPERIMENTALParticipants ≥2 to \<12 Years of Age will receive the administered weight-adjusted RDE of REGV131-LNP1265 determined by Part 1
Interventions
NameTypeDescription
REGV131DRUGAdministered per the protocol before LNP1265
LNP1265DRUGAdministered per the protocol following REGV131
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Eligibility Criteria
Age Range2 Years to N/A
SexMALE
Healthy VolunteersNo
Study Sites44

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, ...

Countries:United StatesAustraliaCanadaFranceGermanyItalySpainUnited Kingdom
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Recent Changes (Last 90 Days)
LOWJul 8, 2026NCT06379789lastUpdatePostDate: changed
LOWJul 8, 2026NCT06379789lastUpdatePostDate: changed
MEDIUMMay 26, 2026NCT06379789primaryCompletionDate: changed
LOWMay 24, 2026NCT06379789studyFirstPostDate: changed