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REGV131

Phase 1

Hemophilia B | Small molecule | Hematology |Regeneron Pharmaceuticals, Inc.|Last Updated: Aug 5, 2026

Success Probability

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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 Sites46

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)

LOWAug 5, 2026NCT06379789lastUpdatePostDate: changed
LOWJul 8, 2026NCT06379789lastUpdatePostDate: changed
LOWJul 8, 2026NCT06379789lastUpdatePostDate: changed

Frequently asked questions about REGV131

What is REGV131 used for in hemophilia B?

REGV131 is an investigational small molecule being developed for the treatment of hemophilia B. It is a coagulation factor IX gene insertion therapy designed to address the underlying deficiency of factor IX in patients with this bleeding disorder. The drug is currently in Phase 1 clinical development.

What does REGV131 target?

REGV131 is a coagulation factor IX gene insertion therapy. It is designed to insert a functional copy of the factor IX gene into cells, enabling the body to produce the clotting factor that is deficient in patients with hemophilia B. This approach aims to address the root cause of the bleeding disorder.

Who makes REGV131?

REGV131 is being developed by Regeneron Pharmaceuticals, Inc., a biopharmaceutical company traded on the Nasdaq under the ticker symbol REGN. The company is conducting a Phase 1 clinical trial to evaluate the safety and effectiveness of this investigational therapy in patients with hemophilia B.

What phase is REGV131 in?

REGV131 is in Phase 1 clinical development. It is an investigational drug, meaning it has not been approved by regulatory authorities and is still being studied for safety and effectiveness. The ongoing Phase 1 trial is currently recruiting participants with hemophilia B.

What clinical trials is REGV131 in?

REGV131 is being studied in a Phase 1 clinical trial registered as NCT06379789. This trial is investigating the safety and effectiveness of REGV131-LNP1265 in pediatric, adolescent, and adult participants with hemophilia B. The study is recruiting up to 130 male participants aged 2 years and older across multiple countries.

Is REGV131 the same as REGV131-LNP1265?

Yes, REGV131 is also known as REGV131-LNP1265. The clinical trial NCT06379789 refers to the therapy as REGV131-LNP1265, indicating that it is the same investigational drug being studied for hemophilia B. This naming convention is used in the trial documentation.