A Study to Evaluate Efficacy and Safety of Casirivimab+Imdevimab (Monoclonal Antibodies) for Prevention of COVID-19 in Immunocompromised Adolescents and Adults

October 9, 2025 updated by: Regeneron Pharmaceuticals

A Phase 3, Randomized, Double-Blind, Placebo-Controlled Study to Evaluate the Efficacy and Safety of Anti-Spike SARS-CoV-2 Monoclonal Antibodies as Pre-Exposure Prophylaxis to Prevent COVID-19 in Immunocompromised Participants

The primary objective of the study is to evaluate the effect of casirivimab+imdevimab, compared with placebo, in preventing symptomatic SARS-CoV-2 infection in immunocompromised participants.

The secondary objectives of the study are:

  • To evaluate the safety and tolerability of repeated SC injections of casirivimab+imdevimab in the study population
  • To characterize concentrations of casirivimab and imdevimab in serum over time
  • To assess the immunogenicity of casirivimab and imdevimab

Study Overview

Status

Status

Indicates the current recruitment status or the expanded access status.
Terminated

Conditions

Conditions

The disease, disorder, syndrome, illness, or injury that is being studied. On ClinicalTrials.gov, conditions may also include other health-related issues, such as lifespan, quality of life, and health risks.

Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.

Study Type

Study Type

Describes the nature of a clinical study. Study types include interventional studies (also called clinical trials), observational studies (including patient registries), and expanded access.
Interventional

Enrollment (Actual)

Enrollment

The number of participants in a clinical study. The "anticipated" enrollment is the target number of participants that the researchers need for the study.
66

Phase

Phase

The stage of a clinical trial studying a drug or biological product, based on definitions developed by the U.S. Food and Drug Administration (FDA). The phase is based on the study's objective, the number of participants, and other characteristics. There are five phases: Early Phase 1 (formerly listed as Phase 0), Phase 1, Phase 2, Phase 3, and Phase 4. Not Applicable is used to describe trials without FDA-defined phases, including trials of devices or behavioral interventions.
  • Phase 3

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Locations

  • Mexico
    • Mexico City
      • Cuauhtémoc, Mexico City, Mexico, 6700
        • Regeneron Study Site
  • United States
    • Alabama
      • Birmingham, Alabama, United States, 35205
        • Central Alabama Research
    • Arkansas
      • Little Rock, Arkansas, United States, 72205
        • Baptist Health Center For Clinical Research
    • California
      • Long Beach, California, United States, 90806
        • Regeneron Study Site
      • Los Angeles, California, United States, 90048
        • Cedars-Sinai Medical Center
      • Los Angeles, California, United States, 90033
        • Regeneron Study Site
      • Palo Alto, California, United States, 94304
        • Stanford University
      • Sacramento, California, United States, 95817
        • University of California
      • Stanford, California, United States, 94305
        • Regeneron Study Site
      • West Hollywood, California, United States, 90069
        • James R Berenson MD Inc.
    • Colorado
      • Aurora, Colorado, United States, 80045
        • University of Colorado
    • Connecticut
      • North Haven, Connecticut, United States, 06473-2195
        • Regeneron Study Site
    • District of Columbia
      • Washington D.C., District of Columbia, United States, 20007
        • Georgetown University
    • Florida
      • Aventura, Florida, United States, 33180
        • Arthritis and Rheumatic Disease Specialties
      • Clearwater, Florida, United States, 33756
        • Innovative Research of West Florida, Inc.
      • Ft. Pierce, Florida, United States, 34982
        • Midway Immunology and Research Center
      • Hollywood, Florida, United States, 33024
        • Elixia COVID-19
      • Miami, Florida, United States, 33184
        • De La Cruz Research Center, LLC
      • Miami, Florida, United States, 33126
        • AppleMed Research Group, LLC
      • Tampa, Florida, United States, 33606
        • University of South Florida
      • Zephyrhills, Florida, United States, 33542
        • Florida Medical Clinic, LLC
    • Georgia
      • Atlanta, Georgia, United States, 30322
        • Regeneron Study Site
      • Marietta, Georgia, United States, 30060
        • Regeneron Study Site
    • Illinois
      • Chicago, Illinois, United States, 60625
        • Great Lakes Clinical Trials - Ravenswood
    • Iowa
      • Iowa City, Iowa, United States, 52242
        • University of Iowa
    • Louisiana
      • New Orleans, Louisiana, United States, 70112
        • Tulane University
    • Maryland
      • Baltimore, Maryland, United States, 21287
        • Johns Hopkins Hospital
      • Baltimore, Maryland, United States, 21201
        • Institute of Human Virology
      • Bethesda, Maryland, United States, 20892
        • Laboratory of Clinical Immunology and Microbiology, NIAID
    • Massachusetts
      • Boston, Massachusetts, United States, 02215
        • Beth Israel Deaconess Medical Center
      • Boston, Massachusetts, United States, 02111
        • Tufts Medical Center
      • Boston, Massachusetts, United States, 02115
        • Regeneron Study Site
    • Michigan
      • Ann Arbor, Michigan, United States, 48109
        • University of Michigan
      • Grand Rapids, Michigan, United States, 49503
        • Spectrum Health
    • Minnesota
      • Rochester, Minnesota, United States, 55905
        • Mayo Clinic
    • Nebraska
      • Omaha, Nebraska, United States, 68198
        • University of Nebraska Medical Center
    • New Jersey
      • Neptune City, New Jersey, United States, 07753
        • Jersey Shore University Medical Center
      • Teaneck, New Jersey, United States, 07666
        • Holy Name
    • New York
      • Brooklyn, New York, United States, 11220
        • Maimonides Cancer Center
      • New York, New York, United States, 10065
        • Memorial Sloan Kettering Cancer Center
      • New York, New York, United States, 10029
        • Icahn School of Medicine at Mount Sinai
      • New York, New York, United States, 10032-3729
        • Regeneron Study Site
      • New York, New York, United States, 10065
        • Regeneron Study Site 2
      • Rochester, New York, United States, 14642
        • Regeneron Study Site
      • Syracuse, New York, United States, 13215
        • Suny Upstate Medical University
      • Syracuse, New York, United States, 13210
        • Regeneron Study Site
      • The Bronx, New York, United States, 10467
        • Montefiore Medical Center
    • North Carolina
      • Morganton, North Carolina, United States, 28655
        • Burke Primary Care
    • Ohio
      • Canton, Ohio, United States, 44718
        • Gabrail Cancer Center Research
      • Cleveland, Ohio, United States, 44195
        • Regeneron Study Site
      • Dayton, Ohio, United States, 45409
        • Miami Valley Hospital
    • Pennsylvania
      • Duncansville, Pennsylvania, United States, 16635
        • Altoona Center for Clinical Research
      • Philadelphia, Pennsylvania, United States, 19140
        • Temple University
      • Philadelphia, Pennsylvania, United States, 19104
        • Penn Prevention Clinical Research Site
    • Rhode Island
      • Providence, Rhode Island, United States, 02903
        • Regeneron Study Site
    • Tennessee
      • Jackson, Tennessee, United States, 38305
        • West Tennessee Research Institute
    • Texas
      • Amarillo, Texas, United States, 79109
        • PharmaTex Research, LLC
      • Austin, Texas, United States, 78705
        • Central Texas Clinical Research
      • Houston, Texas, United States, 77030
        • MD Anderson Cancer Center
      • Houston, Texas, United States, 77030
        • Houston Methodist Hospital
      • Houston, Texas, United States, 77004
        • Therapeutic Concepts, PA
      • Houston, Texas, United States, 77087
        • Synergy Group Medical,LLC
    • Virginia
      • Richmond, Virginia, United States, 23219
        • Regeneron Study Site
    • Washington
      • Seattle, Washington, United States, 98109
        • Fred Hutchinson Cancer Research Center
      • Seattle, Washington, United States, 98122
        • Swedish Medical Center- First Hill
      • Seattle, Washington, United States, 98109
        • Regeneron Study Site
    • Wisconsin
      • Madison, Wisconsin, United States, 53792
        • University Of Wisconsin - Madison

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Eligibility Criteria

The key requirements that people who want to participate in a clinical study must meet or the characteristics they must have. Eligibility criteria consist of both inclusion criteria (which are required for a person to participate in the study) and exclusion criteria (which prevent a person from participating). Types of eligibility criteria include whether a study accepts healthy volunteers, has age or age group requirements, or is limited by sex.

Ages Eligible for Study

12 years and older (Child, Adult, Older Adult)

Accepts Healthy Volunteers

No

Description

Key Inclusion Criteria:

  1. Meets ≥1 of the following criteria:

    • Is immunocompromised, including people with transplant, who have cancer, primary immunodeficiencies, HIV, rheumatological disease, autoimmune disease, multiple sclerosis OR
    • Currently taking immunosuppressant drugs
  2. Have been fully vaccinated against COVID-19 or deemed medically ineligible to receive full course of vaccine
  3. Has documented negative serology/antibody response in an anti-SARS-CoV-2 spike protein IgG clinical test or ≤50 U/mL on the Elecsys® SARS-CoV-2 S Total Ig test
  4. Tested negative for the COVID-19 virus within 72 hours prior to randomization

Key Exclusion Criteria:

  1. Weighs <40 kg (only applies to participants ≥12 to <18 years of age)
  2. Has any signs or symptoms consistent with COVID-19
  3. Past COVID-19 infection within 90 days prior to randomization
  4. Planned use of any investigational, authorized, or approved vaccine for COVID-19 within 90 days of the last dose of study drug
  5. Prior, current, or planned use of any of COVID-19 convalescent plasma, other monoclonal antibodies against SARS-CoV-2 or any COVID-19 treatment
  6. Is planned to begin immunoglobulin (IVIG) or immunoglobulin (SCIG) therapy, is planned to have a change to existing IVIG or SCIG, or has been on a chronic stable dose of their IVIG or SCIG regimen for less than 90 days prior to screening
  7. Has any known active acute respiratory infection
  8. Has persistent (refractory to treatment for ≥14 days) bacterial or fungal infection
  9. Has known allergy or hypersensitivity to components of the study drugs

NOTE: Other Protocol Defined Inclusion/Exclusion Criteria Apply

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Prevention
  • Allocation: Randomized
  • Interventional Model: Sequential Assignment
  • Masking: Triple

Arms and Interventions

Participant Group / Arm

Participant Group / Arm

A group or subgroup of participants in a clinical trial that receives a specific intervention/treatment, or no intervention, according to the trial's protocol.
Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.
Experimental: casirivimab+imdevimab Initial + Q4W
Initial subcutaneous (SC) dose, then SC dose every 4 weeks (Q4W)
Drug: casirivimab+imdevimab
Co-administered sequentially subcutaneous (SC)
Other Names:
  • REGN-COV2
  • REGEN-COV™
  • Ronapreve™
  • REGN10933
  • REGN10987
Experimental: casirivimab+imdevimab Q4W
SC dose Q4W
Drug: casirivimab+imdevimab
Co-administered sequentially subcutaneous (SC)
Other Names:
  • REGN-COV2
  • REGEN-COV™
  • Ronapreve™
  • REGN10933
  • REGN10987
Experimental: casirivimab+imdevimab Q12W
SC dose every 12 weeks (Q12W)
Drug: casirivimab+imdevimab
Co-administered sequentially subcutaneous (SC)
Other Names:
  • REGN-COV2
  • REGEN-COV™
  • Ronapreve™
  • REGN10933
  • REGN10987
Placebo Comparator: Placebo
SC dose Q4W
Drug: Placebo
Administered SC

What is the study measuring?

Primary Outcome Measures

Primary Outcome Measures

In a clinical study's protocol, the planned outcome measure that is the most important for evaluating the effect of an intervention/treatment. Most clinical studies have one primary outcome measure, but some have more than one.
Outcome Measure
Measure Description
Time Frame
Cumulative Incidence of Symptomatic (Broad Term), RT-PCR-confirmed SARS-CoV-2 Infection Cases During the EAP
Time Frame: The EAP was defined as the day from first dose of study drug to day 169 +/- 7 days
Cumulative incidence of symptomatic (broad term), RT-PCR-confirmed SARS-CoV-2 infection cases during the Efficacy Assessment Period (EAP)
The EAP was defined as the day from first dose of study drug to day 169 +/- 7 days

Secondary Outcome Measures

Secondary Outcome Measures

In a clinical study's protocol, a planned outcome measure that is not as important as the primary outcome measure for evaluating the effect of an intervention but is still of interest. Most clinical studies have more than one secondary outcome measure.
Outcome Measure
Time Frame
Number of Participants With Grade ≥3 Treatment-emergent Adverse Events (TEAEs) During the EAP
Time Frame: The EAP was defined as the day from first dose of study drug to day 169 +/- 7 days
The EAP was defined as the day from first dose of study drug to day 169 +/- 7 days
Number of Participants With Grade ≥3 Treatment-emergent Adverse Events (TEAEs) During the Follow-Up Period
Time Frame: End of EAP to the end of the Follow-Up Period (Day 169 to 205, approximately ~1 months)
End of EAP to the end of the Follow-Up Period (Day 169 to 205, approximately ~1 months)
Number of Participants With TEAEs Leading to Study Drug Discontinuation During the EAP
Time Frame: The EAP was defined as the day from first dose of study drug to day 169 +/- 7 days
The EAP was defined as the day from first dose of study drug to day 169 +/- 7 days
Number of Participants With TEAEs Leading to Study Drug Discontinuation During the Follow-Up Period
Time Frame: End of EAP to the end of the Follow-Up Period (Day 169 to 205, approximately ~1 months)
End of EAP to the end of the Follow-Up Period (Day 169 to 205, approximately ~1 months)
Number of Participants With Treatment-emergent Serious Adverse Events (SAEs) During the EAP
Time Frame: The EAP was defined as the day from first dose of study drug to day 169 +/- 7 days
The EAP was defined as the day from first dose of study drug to day 169 +/- 7 days
Proportion of Participants With Treatment-emergent Serious Adverse Events (SAEs) During the Follow-Up Period
Time Frame: End of EAP to the end of the Follow-Up Period (Day 169 to 205, approximately ~1 months)
End of EAP to the end of the Follow-Up Period (Day 169 to 205, approximately ~1 months)
Incidence of Adverse Events of Special Interest (AESIs) During the EAP
Time Frame: The EAP was defined as the day from first dose of study drug to day 169 +/- 7 days
The EAP was defined as the day from first dose of study drug to day 169 +/- 7 days
Concentration of Casirivimab Over Time
Time Frame: Up to 28 days postdose for the Q4W groups and 84 days postdose for the Q12 group
Up to 28 days postdose for the Q4W groups and 84 days postdose for the Q12 group
Concentration of Imdevimab Over Time
Time Frame: Up to 28 days postdose for the Q4W groups and 84 days postdose for the Q12 group
Up to 28 days postdose for the Q4W groups and 84 days postdose for the Q12 group
Incidence of Anti-drug Antibodies (ADA) Over Time
Time Frame: Up to 28 days postdose for the Q4W groups and 84 days postdose for the Q12 group
Up to 28 days postdose for the Q4W groups and 84 days postdose for the Q12 group
Incidence of Neutralizing Antibodies (NAb) to Each mAb Over Time
Time Frame: Up to 28 days postdose for the Q4W groups and 84 days postdose for the Q12 group
Up to 28 days postdose for the Q4W groups and 84 days postdose for the Q12 group

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Sponsor

The organization or person who initiates the study and who has authority and control over the study.
Regeneron Pharmaceuticals

Investigators

Investigators

A researcher involved in a clinical study. Related terms include site principal investigator, site sub-investigator, study chair, study director, and study principal investigator.
  • Study Director: Clinical Trial Management, Regeneron Pharmaceuticals

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

Study Start

The actual date on which the first participant was enrolled in a clinical study. The "anticipated" study start date is the date that the researchers think will be the study start date.
October 25, 2021

Primary Completion (Actual)

Primary Completion

The date on which the last participant in a clinical study was examined or received an intervention to collect final data for the primary outcome measure. Whether the clinical study ended according to the protocol or was terminated does not affect this date. For clinical studies with more than one primary outcome measure with different completion dates, this term refers to the date on which data collection is completed for all the primary outcome measures. The "anticipated" primary completion date is the date that the researchers think will be the primary completion date for the study.
May 18, 2022

Study Completion (Actual)

Study Completion

The date on which the last participant in a clinical study was examined or received an intervention/treatment to collect final data for the primary outcome measures, secondary outcome measures, and adverse events (that is, the last participant's last visit). The "anticipated" study completion date is the date that the researchers think will be the study completion date.
May 18, 2022

Study Registration Dates

First Submitted

First Submitted

The date on which the study sponsor or investigator first submitted a study record to ClinicalTrials.gov. There is typically a delay of a few days between the first submitted date and the record's availability on ClinicalTrials.gov (the first posted date).
October 8, 2021

First Submitted That Met QC Criteria

First Submitted That Met QC Criteria

The date on which the study sponsor or investigator first submits a study record that is consistent with National Library of Medicine (NLM) quality control (QC) review criteria. The sponsor or investigator may need to revise and submit a study record one or more times before NLM's QC review criteria are met. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
October 8, 2021

First Posted (Actual)

First Posted

The date on which the study record was first available on ClinicalTrials.gov after National Library of Medicine (NLM) quality control (QC) review has concluded. There is typically a delay of a few days between the date the study sponsor or investigator submitted the study record and the first posted date.
October 12, 2021

Study Record Updates

Last Update Posted (Actual)

Last Update Posted

The most recent date on which changes to a study record were made available on ClinicalTrials.gov. There may be a delay between when the changes were submitted to ClinicalTrials.gov by the study's sponsor or investigator (the last update submitted date) and the last update posted date.
October 20, 2025

Last Update Submitted That Met QC Criteria

Last Update Submitted That Met QC Criteria

The most recent date on which the study sponsor or investigator submitted changes to a study record that are consistent with National Library of Medicine (NLM) quality control (QC) review criteria. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
October 9, 2025

Last Verified

Last Verified

The most recent date on which the study sponsor or investigator confirmed the information about a clinical study on ClinicalTrials.gov as accurate and current. If a study with a recruitment status of recruiting; not yet recruiting; or active, not recruiting has not been confirmed within the past 2 years, the study's recruitment status is shown as unknown.
October 1, 2025

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

Other Study ID Numbers

Identifiers or ID numbers other than the NCT number that are assigned to a clinical study by the study's sponsor, funders, or others. These numbers may include unique identifiers from other trial registries and National Institutes of Health grant numbers.
  • R10933-10987-COV-2176
  • 2021-005222-14 (EudraCT Number)

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

YES

IPD Plan Description

All Individual Patient Data (IPD) that underlie publicly available results will be considered for sharing

IPD Sharing Time Frame

When Regeneron has received marketing authorization from major health authorities (e.g., FDA, European Medicines Agency (EMA), Pharmaceuticals and Medical Devices Agency (PMDA), etc.) for the product and indication, has made the study results publicly available (e.g., scientific publication, scientific conference, clinical trial registry), has the legal authority to share the data, and has ensured the ability to protect participant privacy.

IPD Sharing Access Criteria

Qualified researchers can submit a proposal for access to individual patient or aggregate level data from a Regeneron-sponsored clinical trial through Vivli. Regeneron's Independent Research Request Evaluation Criteria can be found at: https://www.regeneron.com/sites/default/files/Regeneron-External-Data-Sharing-Policy-and-Independent-Research-Request-Evaluation-Criteria.pdf

IPD Sharing Supporting Information Type

  • STUDY_PROTOCOL
  • SAP
  • ICF
  • ANALYTIC_CODE
  • CSR

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

Yes

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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