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.

Contact this study

In brief

Phase 32,000 participants sought36 sites4 countries

Registered in 1 registry

ClinicalTrials.govNCT07213778Open this record at ClinicalTrials.govSynced 5 days ago

One study can be registered in several registries. We show it once and link every record we hold.

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.

Present: Registered before enrolment beganFirst posted 2025-10-09; recorded start 2025-11-24
Present: Has a defined primary outcomeA primary outcome measure is listed in the record
Present: The primary outcome states a time frameThe primary outcome measure records a time frame
Present: Participants are randomly assignedAllocation is recorded as randomised
Present: Has a comparison groupThe record lists a placebo or comparator arm, or more than one study arm
Present: Uses blinding (masking)A masking level is recorded in the record
Not stated: An ethics committee is not stated in the registry recordThis registry's ingested record has no ethics-committee field
Not stated: Regulatory oversight (such as an IND or IDE) is not stated in the registry recordThis registry's ingested record has no regulatory-authorisation field
Not stated: 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.
Present: No cost to participants is mentioned in the recordChecked the summary, description and eligibility text; no cost-to-participant phrase found
Present: Sponsor has 251 other studies in this databaseCounted from the lead sponsor named in the record (Regeneron Pharmaceuticals)
Present: 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

Eligibility
Sex	All
Ages	18 Years – No maximum
Healthy volunteers	No

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 design
Study type	Interventional
Phase	Phase 3
Allocation	Randomised
Intervention model	PARALLEL
Primary purpose	TREATMENT
Masking	QUADRUPLE (4)
Enrolment	2,000 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

Primary outcome
Incidence of the composite endpoint of symptomatic VTE and all-cause death
Time frame Through day 30 visit
Secondary outcome
Incidence of all-cause death
Time frame Through day 30 visit
Secondary outcome
Time to first event of the confirmed symptomatic DVT
Time frame Through day 30 visit
Secondary outcome
Time to first event of the confirmed PE
Time frame Through day 30 visit
Secondary outcome
Time to the all-cause death
Time frame Through day 30 visit
Secondary outcome
Incidence of the composite endpoint of major bleeding and Clinically Relevant Non-Major (CRNM) bleeding
Time frame Through day 30 visit
Secondary outcome
Incidence of minor bleeding
Time frame Through day 30 visit
Secondary outcome
Incidence of Treatment-Emergent Adverse Events (TEAEs)
Time frame Through day 90 visit
Secondary outcome
Severity of TEAEs
Time frame Through day 90 visit
Secondary outcome
Incidence of Anti-drug Antibody (ADA) to REGN7508
Time frame Through day 90 visit
Secondary outcome
Magnitude of ADA to REGN7508
Time frame Through day 90 visit
Secondary outcome
Concentrations of REGN7508
Time frame Through day 90 visit
Secondary outcome
Time to first event of the composite endpoint of symptomatic VTE and all-cause death
Time frame Through day 30 visit
Secondary outcome
Incidence of confirmed symptomatic Deep Vein Thrombosis (DVT)
Time frame Through day 30 visit
Secondary outcome
Incidence of confirmed Pulmonary Embolism (PE)
Time frame Through day 30 visit

Dates

Dates
Start date	November 24, 2025 (actual)
Primary completion	May 17, 2027 (estimated)
Completion	July 16, 2027 (estimated)
First posted	October 9, 2025 (actual)
Last updated	September 14, 2026
Results posted	Not stated in the registry record
Status last verified	September 2026

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

Locations

34 sites are recruiting

Greece

Greece
Facility	City	State or region	Status
Henry Dunant Hospital Center	Athens	Attica	Recruiting

Malaysia

Malaysia
Facility	City	State or region	Status
Hospital Pakar Universiti Sains Malaysia	Kota Bharu	Kelantan	Recruiting
Hospital Queen Elizabeth II	Kota Kinabalu	Sabah	Recruiting
Hospital Tengku Ampuan Afzan (HTTA)	Kuantan	Pahang	Recruiting
Sultan Abdul Halim Hospital	Sungai Petani	Kedah	Recruiting

Moldova

Moldova
Facility	City	State or region	Status
PMSI Emergency Medicine Institute	Chisinau		Recruiting

United States

United States
Facility	City	State or region	Status
Velocity Clinical Research, Annapolis	Annapolis	Maryland	Recruiting
Sinai Hospital of Baltimore, Inc.	Baltimore	Maryland	Recruiting
Boston Medical Center	Boston	Massachusetts	Recruiting
Tufts Medical Center	Boston	Massachusetts	Recruiting
University of Cincinnati	Cincinnati	Ohio	Recruiting
The Ohio State University Wexner Medical Center	Columbus	Ohio	Recruiting
Ohio Clinical Trials	Columbus	Ohio	Recruiting
South Florida Joint Replacement Center	Deerfield Beach	Florida	Recruiting
Duke University Health System (Duke Health), Duke University Hospital	Durham	North Carolina	Recruiting
HD Research - Memorial Hermann Village	Houston	Texas	Completed
NextStage Clinical Research, All American Orthopedics and Sports Medicine	Houston	Texas	Recruiting
The Orthopaedic Research Foundation, Inc.	Indianapolis	Indiana	Recruiting
Horizon Clinical Research	La Mesa	California	Recruiting
Sky Ridge Medical Center	Lone Tree	Colorado	Recruiting
Medical Research of Westchester - MPLUS Research Network	Miami	Florida	Recruiting
University of Pittsburgh	Pittsburgh	Pennsylvania	Recruiting
Eximia Equihealth Research-Raleigh. LLC	Raleigh	North Carolina	Recruiting
The Vein and Vascular Center at Raleigh Radiology	Raleigh	North Carolina	Recruiting
Eisenhower Medical Center	Rancho Mirage	California	Recruiting
Carilion Clinic	Roanoke	Virginia	Recruiting
University of Rochester Medical Center	Rochester	New York	Recruiting
Endeavor Clinical Trials	San Antonio	Texas	Withdrawn
Flourish Research - San Antonio (Formerly Clinical Trials of Texas)	San Antonio	Texas	Recruiting
Endeavor Health	Skokie	Illinois	Recruiting
Larkin Community Hospital South Miami	South Miami	Florida	Recruiting
Spokane Joint Replacement Center	Spokane	Washington	Recruiting
Phoenix Clinical Research	Tamarac	Florida	Recruiting
Holy Name Medical Center	Teaneck	New Jersey	Recruiting
NextStage Clinical Research, St. Francis Medical Park	Wichita	Kansas	Recruiting
Coastal Vascular Institute, PA	Wilmington	North Carolina	Recruiting

Study documents

No documents are linked in this registry record.

Changes over time

September 14, 2026
Site added
2 sites added (36 total)
3436
August 19, 2026
Site added
2 sites added (34 total)
3234

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

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

Categories

Registered in 1 registry

Interested in this study?

How this study is set up

Summary

Conditions

Eligibility

Eligibility as written in the registry

Eligibility in plain statements

Study design

Sponsor and collaborators

Arms and interventions

Interventions

Outcome measures

Dates

Locations

Greece

Malaysia

Moldova

United States

Study documents

Changes over time