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NCT07213778ClinicalTrials.gov

REGN7508 Versus Acetylsalicylic Acid (ASA) for Venous Thromboprophylaxis After Total Knee Arthroplasty in Adult Participants

A Phase 3, Multicenter, Double-Blinded, Randomized Study to Evaluate REGN7508, a Factor XI Monoclonal Antibody, Versus Acetylsalicylic Acid for Prophylaxis of Symptomatic Venous Thromboembolism After Elective Total Knee Arthroplasty (ROXI-ASPEN)

RecruitingTaking participants now, according to the registry record.
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In brief

This study is researching an experimental drug called REGN7508 (called "study drug") and how it compares against another treatment called Acetylsalicylic Acid (ASA). The study is focused on adults undergoing elective, unilateral (one side) total knee replacement surgery. The aim…

Phase 32,000 participants sought36 sites4 countries

Categories

Haematology37%Musculoskeletal21%Cardiovascular21%Respiratory21%

Registered in 1 registry

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Trial information is shown as published by the registry, in its original language.

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How this study is set up

The points below are drawn from the public registry record for this study. Each one cites the field or sentence it came from. A dash (—) means the record does not state something — not that it is missing or wrong. Many well-run studies, especially small ones, leave some of these blank.

  • Registered before enrolment beganFirst posted 2025-10-09; recorded start 2025-11-24
  • Has a defined primary outcomeA primary outcome measure is listed in the record
  • The primary outcome states a time frameThe primary outcome measure records a time frame
  • Participants are randomly assignedAllocation is recorded as randomised
  • Has a comparison groupThe record lists a placebo or comparator arm, or more than one study arm
  • Uses blinding (masking)A masking level is recorded in the record
  • An ethics committee is not stated in the registry recordThis registry's ingested record has no ethics-committee field
  • Regulatory oversight (such as an IND or IDE) is not stated in the registry recordThis registry's ingested record has no regulatory-authorisation field
  • A data monitoring committee is not stated in the registry recordThis registry's ingested record has no data-monitoring-committee fieldA data monitoring committee is not required for many smaller studies, and its absence here is not unusual.
  • No cost to participants is mentioned in the recordChecked the summary, description and eligibility text; no cost-to-participant phrase found
  • Sponsor has 251 other studies in this databaseCounted from the lead sponsor named in the record (Regeneron Pharmaceuticals)
  • Sponsor has posted results for at least one studyBased on the sponsor’s studies in this database
  • The record lists 1 condition.
  • Lead sponsor type recorded as: industry.
  • Intervention regulatory context: investigational, within a phased regulatory pathway.

These are facts from the public registry record, not a judgement about the study. Discuss any trial with your own doctor before taking part.

What these facts mean, and what to ask · ruleset v1

Trial stature

Three independent measures of this study, described from its registry record — not a recommendation about it. A rigorous study by investigators nobody has heard of is better evidence than a weak study led by a famous one. How these are scored.

Methodological rigourDEFINITIVE

A definitive-grade design for a phase 3 study, judged from its ClinicalTrials.gov record.

How this score is built
  • Randomised allocation20/20

    Participants are randomly allocated between arms

  • Blinding20/20

    Quadruple-blind

  • Control arm15/15

    Active-comparator control arm

  • Primary-outcome specificity10/10

    Named primary outcome with a defined time frame

  • Endpoint type10/10

    Mortality / MACE endpoint (hard clinical outcome)

  • Multi-centre8/8

    Multi-centre: 32 sites

  • Data monitoring committee7/7

    A data monitoring committee is in place

  • Prospective registration5/5

    Registered before the study start date

  • Protocol / SAP posted0/5

    No protocol or SAP posted to the registry

ScaleLARGE

A large study, international in scope: 2,000 participants (target), run at 36 sites, across 4 countries.

How this score is built
  • Enrolment33/40

    2,000 participants (target)

  • Site count18/25

    32 sites

  • Country count7/15

    4 countries

  • Planned duration6/10

    Planned over about 20 months

  • Sponsor scale9/10

    Regeneron Pharmaceuticals has led 248 trials in our corpus

Investigator standingUNKNOWN

We have no verifiable track record for the investigator named on this trial. That is common for early-career investigators and for records held outside ClinicalTrials.gov — it is not a negative signal.

How this score is built
  • Investigator standing0/100

    No investigator recorded in the registry for this trial

These describe the registry record only, and today we hold ClinicalTrials.gov data. Absent fields lower a score, and absence often reflects registration practice rather than study quality. A high-stature trial is not necessarily safer or a better choice for you — enrolling in a large definitive trial can mean a higher chance of receiving placebo, while a small early-phase study may be the only route to a new therapy.

Summary

This study is researching an experimental drug called REGN7508 (called "study drug") and how it compares against another treatment called Acetylsalicylic Acid (ASA). The study is focused on adults undergoing elective, unilateral (one side) total knee replacement surgery. The aim of the study is to see how effective the study drug is at preventing Venous Thromboembolism (VTE) and other related diseases after total knee replacement surgery compared to acetylsalicylic acid. The study is looking at several other research questions, including: * What side effects may happen from taking the study drug * How much study drug is in the blood at different times * Whether the body makes antibodies against the study drug (which could make the study drug less effective or could lead to side effects)

Conditions

  • Symptomatic Venous Thromboembolism (VTE)

Eligibility

SexAll
Ages18 Years – No maximum
Healthy volunteersNo

Eligibility as written in the registry

Key Inclusion Criteria: 1. Is undergoing a primary elective unilateral TKA 2. Is in good health based on laboratory safety testing as described in the protocol Key Exclusion Criteria: 1. Any condition that, as assessed by the investigator, may confound the results of the study or pose an additional risk to the participant by study participation 2. History of bleeding in the 6 months prior to randomization requiring hospitalization or transfusion; history of intracranial or intraocular bleeding, excessive operative or post-operative bleeding, and traumatic spinal or epidural anesthesia; history of bleeding diathesis (eg, hemophilia A or B, von Willebrand's Factor deficiency) 3. History of thromboembolic disease or thrombophilia 4. History of platelet dysfunction 5. Has received or plans to receive preoperative enoxaparin on the day prior to TKA surgery Note: Other protocol-defined Inclusion/ Exclusion criteria apply

Eligibility in plain statements

This record's criteria have not been broken into separate statements yet. The registry text above is complete and is the authoritative version.

Study design

Study typeInterventional
PhasePhase 3
AllocationRandomised
Intervention modelPARALLEL
Primary purposeTREATMENT
MaskingQUADRUPLE (4)
Enrolment2,000 participants sought

Sponsor and collaborators

  • Regeneron Pharmaceuticals Sponsor

Arms and interventions

  • REGN7508 and PlaceboEXPERIMENTAL
  • Placebo and ASAACTIVE_COMPARATOR

Interventions

  • Drug Acetylsalicylic Acid (ASA)

    Administered per the protocol

  • Drug Placebo

    Administered per the protocol

  • Drug REGN7508

    Administered per the protocol

Outcome measures

  1. Primary outcome

    Incidence of the composite endpoint of symptomatic VTE and all-cause death

    Time frame Through day 30 visit

  2. Secondary outcome

    Incidence of all-cause death

    Time frame Through day 30 visit

  3. Secondary outcome

    Time to first event of the confirmed symptomatic DVT

    Time frame Through day 30 visit

  4. Secondary outcome

    Time to first event of the confirmed PE

    Time frame Through day 30 visit

  5. Secondary outcome

    Time to the all-cause death

    Time frame Through day 30 visit

  6. Secondary outcome

    Incidence of the composite endpoint of major bleeding and Clinically Relevant Non-Major (CRNM) bleeding

    Time frame Through day 30 visit

  7. Secondary outcome

    Incidence of minor bleeding

    Time frame Through day 30 visit

  8. Secondary outcome

    Incidence of Treatment-Emergent Adverse Events (TEAEs)

    Time frame Through day 90 visit

  9. Secondary outcome

    Severity of TEAEs

    Time frame Through day 90 visit

  10. Secondary outcome

    Incidence of Anti-drug Antibody (ADA) to REGN7508

    Time frame Through day 90 visit

  11. Secondary outcome

    Magnitude of ADA to REGN7508

    Time frame Through day 90 visit

  12. Secondary outcome

    Concentrations of REGN7508

    Time frame Through day 90 visit

  13. Secondary outcome

    Time to first event of the composite endpoint of symptomatic VTE and all-cause death

    Time frame Through day 30 visit

  14. Secondary outcome

    Incidence of confirmed symptomatic Deep Vein Thrombosis (DVT)

    Time frame Through day 30 visit

  15. Secondary outcome

    Incidence of confirmed Pulmonary Embolism (PE)

    Time frame Through day 30 visit

Dates

Start dateNovember 24, 2025 (actual)
Primary completionMay 17, 2027 (estimated)
CompletionJuly 16, 2027 (estimated)
First postedOctober 9, 2025 (actual)
Last updatedSeptember 14, 2026
Results postedNot stated in the registry record
Status last verifiedSeptember 2026

Actual means the event happened. Estimated means the sponsor expects it. The two mean different things.

Locations

34 sites are recruiting

Greece

FacilityCityState or regionStatus
Henry Dunant Hospital CenterAthensAtticaRecruiting

Malaysia

FacilityCityState or regionStatus
Hospital Pakar Universiti Sains MalaysiaKota BharuKelantanRecruiting
Hospital Queen Elizabeth IIKota KinabaluSabahRecruiting
Hospital Tengku Ampuan Afzan (HTTA)KuantanPahangRecruiting
Sultan Abdul Halim HospitalSungai PetaniKedahRecruiting

Moldova

FacilityCityState or regionStatus
PMSI Emergency Medicine InstituteChisinauRecruiting

United States

FacilityCityState or regionStatus
Velocity Clinical Research, AnnapolisAnnapolisMarylandRecruiting
Sinai Hospital of Baltimore, Inc.BaltimoreMarylandRecruiting
Boston Medical CenterBostonMassachusettsRecruiting
Tufts Medical CenterBostonMassachusettsRecruiting
University of CincinnatiCincinnatiOhioRecruiting
The Ohio State University Wexner Medical CenterColumbusOhioRecruiting
Ohio Clinical TrialsColumbusOhioRecruiting
South Florida Joint Replacement CenterDeerfield BeachFloridaRecruiting
Duke University Health System (Duke Health), Duke University HospitalDurhamNorth CarolinaRecruiting
HD Research - Memorial Hermann VillageHoustonTexasCompleted
NextStage Clinical Research, All American Orthopedics and Sports MedicineHoustonTexasRecruiting
The Orthopaedic Research Foundation, Inc.IndianapolisIndianaRecruiting
Horizon Clinical ResearchLa MesaCaliforniaRecruiting
Sky Ridge Medical CenterLone TreeColoradoRecruiting
Medical Research of Westchester - MPLUS Research NetworkMiamiFloridaRecruiting
University of PittsburghPittsburghPennsylvaniaRecruiting
Eximia Equihealth Research-Raleigh. LLCRaleighNorth CarolinaRecruiting
The Vein and Vascular Center at Raleigh RadiologyRaleighNorth CarolinaRecruiting
Eisenhower Medical CenterRancho MirageCaliforniaRecruiting
Carilion ClinicRoanokeVirginiaRecruiting
University of Rochester Medical CenterRochesterNew YorkRecruiting
Endeavor Clinical TrialsSan AntonioTexasWithdrawn
Flourish Research - San Antonio (Formerly Clinical Trials of Texas)San AntonioTexasRecruiting
Endeavor HealthSkokieIllinoisRecruiting
Larkin Community Hospital South MiamiSouth MiamiFloridaRecruiting
Spokane Joint Replacement CenterSpokaneWashingtonRecruiting
Phoenix Clinical ResearchTamaracFloridaRecruiting
Holy Name Medical CenterTeaneckNew JerseyRecruiting
NextStage Clinical Research, St. Francis Medical ParkWichitaKansasRecruiting
Coastal Vascular Institute, PAWilmingtonNorth CarolinaRecruiting

Study documents

No documents are linked in this registry record.

Changes over time

  1. September 14, 2026

    Site added

    2 sites added (36 total)

    3436

  2. August 19, 2026

    Site added

    2 sites added (34 total)

    3234

Registry: ClinicalTrials.gov · NCT########

https://xmedica.io/trials/ctgov/NCT07213778