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REGN9933

Phase 2

Venous Thromboembolism | Small molecule | Cardiovascular |Regeneron Pharmaceuticals, Inc.|Last Updated: Aug 12, 2026

Target and mechanism

Molecular targetFactor XI
Target classProtein
ModalitySmall molecule

Success Probability

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Market & Valuation

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Trial Design

RandomizedDouble-BlindACTIVE_CONTROLLEDDMC
Total Trials2
Total Enrollment568

FDA Designations

No designations recorded

Clinical trial landscape

REGN9933 · 5 trials · 3 indications

Phase 2 2Phase 1 3
NCT06299111A Trial to Learn How Well REGN9933 and REGN7508 Work for Preventing Blood Clots, and How Safe They Are, in Adults Who Have a Peripherally Inserted Central Catheter (PICC)Venous Thromboembolism
COMPLETED195 Analytics
NCT05618808A Trial to Learn How Well REGN9933 Works for Preventing Blood Clots After Knee Replacement Surgery in Adult ParticipantsVenous Thromboembolism
COMPLETED373 Analytics
PHASE2COMPLETED
A Trial to Learn How Well REGN9933 and REGN7508 Work for Preventing Blood Clots, and How Safe They Are, in Adults Who Have a Peripherally Inserted Central Catheter (PICC)
Venous ThromboembolismUnlock trial analytics
PHASE2COMPLETED
A Trial to Learn How Well REGN9933 Works for Preventing Blood Clots After Knee Replacement Surgery in Adult Participants
Venous ThromboembolismUnlock trial analytics

Study Endpoints

Primary Endpoints

Incidence of confirmed VTE per central reading center (CRC) review
Through Day 14
Incidence of treatment-emergent adverse event (TEAEs)
Up to Day 100
Severity of TEAEs
Up to Day 100
Percentage of Participants With Confirmed, Adjudicated Venous Thromboembolism (VTE) (REGN9933 vs Enoxaparin)
Through Day 12

Composite endpoint that includes: asymptomatic deep DVT (deep venous thrombosis) detected by unilateral venography of the operated leg; confirmed symptomatic DVT of either leg; confirmed fatal or nonfatal pulmonary embolism (PE) including unexplained death for which PE cannot be ruled out

Occurrence of Treatment-Emergent Adverse Events (TEAEs)
Up to approximately 78 days
Change in fecal hemoglobin content (FHC)
Baseline and up to day 22
Incidence and severity of treatment emergent adverse events (TEAE)
Until resolution of pharmacodynamic (PD) effects; approximately 36 days

Secondary Endpoints

Incidence of confirmed PICC associated venous thrombosis per CRC review
Through Day 14
Incidence of major bleeding
Through Day 14
Incidence of clinically relevant non-major (CRNM) bleeding
Through Day 14
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Study Design & Arms

AllocationRANDOMIZED
MaskingQUADRUPLE
ModelPARALLEL
PurposeTREATMENT

Treatment Arms

ArmTypeDescription
REGN9933EXPERIMENTALRandomized 1:1:1
REGN7508EXPERIMENTALRandomized 1:1:1
PlaceboPLACEBO_COMPARATORRandomized 1:1:1
EnoxaparinACTIVE_COMPARATOREnoxaparin will be administered by subcutaneous (SC) administration
ApixabanACTIVE_COMPARATORApixaban will be administered orally twice a day
REGN9533EXPERIMENTAL -
Arm 1: AspirinACTIVE_COMPARATORRandomized 1:1:1:1
Arm 2: Aspirin + REGN9933EXPERIMENTALRandomized 1:1:1:1
Arm 3: Aspirin + REGN7508EXPERIMENTALRandomized 1:1:1:1
Arm 4: Aspirin + RivaroxabanACTIVE_COMPARATORRandomized 1:1:1:1
Intravenous CohortsEXPERIMENTALRandomized 6:2 to REGN9933 or placebo
Subcutaneous CohortsEXPERIMENTALRandomized 6:2 to REGN9933 or placebo

Interventions

NameTypeDescription
REGN9933DRUGIntravenous (IV) single dose administered
REGN7508DRUGIV single dose administered
PlaceboDRUGIV single dose administered
EnoxaparinDRUGParticipants will receive enoxaparin by SC administration daily through the time of venography (or day 12, whichever is earlier)
ApixibanDRUGParticipants will receive apixaban orally twice a day through the time of venography (or day 12, whichever is earlier)
REGN9533DRUGAdministered per the protocol
HeparinDRUGAdministered per the protocol
AspirinDRUGOral administration
RivaroxabanDRUGOral administration
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Eligibility Criteria

Age Range18 Years to N/A
SexALL
Healthy VolunteersNo
Study Sites23

Key Inclusion Criteria: 1. PICC is clinically indicated for at least 14 days and is anticipated to remain in place for at least 14 days 2. Eastern Cooperative Oncology Group (ECOG) Performance Status ≤2 or equivalent functional status as described in the protocol 3. Body weight ≥45 kg and ≤130 kg d...

Countries:United StatesBulgariaCanadaIsraelRomaniaUnited KingdomBelgiumHungaryLatviaLithuaniaPoland
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Recent Changes (Last 90 Days)

LOWAug 12, 2026NCT07759167NEW_TRIAL: changed
LOWAug 12, 2026NCT07759167NEW_TRIAL: changed

Frequently asked questions about REGN9933

What is REGN9933 used for?

REGN9933 is an investigational small molecule being studied for preventing blood clots, including venous thromboembolism after knee replacement surgery and in adults with a peripherally inserted central catheter. It is also being evaluated in healthy volunteers and in adults with end-stage kidney disease on hemodialysis.

What does REGN9933 target?

REGN9933 targets Factor XI, a protein involved in blood clotting. By targeting Factor XI, REGN9933 is being studied as a potential anticoagulant to prevent blood clots while possibly reducing bleeding risk compared to other anticoagulants.

Who is developing REGN9933?

REGN9933 is being developed by Regeneron Pharmaceuticals, Inc., a biopharmaceutical company traded on the Nasdaq under the ticker REGN.

What phase is REGN9933 in?

REGN9933 is in Phase 1 clinical development. It has completed Phase 1 and Phase 2 trials, and a new Phase 1 trial in end-stage kidney disease is planned but not yet recruiting. It is not approved by the FDA and remains investigational.

What clinical trials is REGN9933 in?

REGN9933 has been studied in several trials. NCT05102136 was a Phase 1 healthy volunteer study. NCT05618808 was a Phase 2 trial for preventing blood clots after knee replacement. NCT06299111 was a Phase 2 trial for preventing clots with a PICC line. NCT07759167 is a planned Phase 1 trial in end-stage kidney disease.

Is REGN9933 the same as REGN7508 or REGN9533?

No, REGN9933 is a distinct investigational drug from REGN7508 and REGN9533. These are separate monoclonal antibodies being studied by Regeneron, sometimes in the same trials, such as NCT06299111 and NCT07759167, but they are not the same compound.