HealthyPhase 2NCT04852978

COVID-19 Study to Assess Immunogenicity, Safety, and Tolerability of Moderna mRNA-1273 Vaccine Administered With Casirivimab+Imdevimab in Healthy Adult Volunteers

A Phase 2 study testing casirivimab+imdevimab and Moderna mRNA-1273 vaccine in people with Healthy and Chronic Stable Illness, run by Regeneron Pharmaceuticals at 6 sites in United States.

Completed

Finished. The study has ended and is not enrolling. Results may be posted on the official record.

Official record

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Trial summary

The primary objectives of the study are: To evaluate the extent of effect, if any, of REGN10933+REGN10987 administration on vaccine-induced neutralizing antibody responses to SARS-CoV-2 by Moderna mRNA-1273 To evaluate the time interval required between REGN10933+REGN10987 administration and Moderna mRNA-1273… Read more about this study

Who is it for?: Ages 18 to 90 yearsHealthy volunteers can take part
Conditions the study is for: Healthy, Chronic Stable Illness
What is being tested?: casirivimab+imdevimab and Moderna mRNA-1273 vaccine
Type of treatment: Vaccines, Injection or infusion
Could I receive a placebo?: No, everyone receives an active treatment
How many people: 295 participants
Where: 6 sitesUnited States
Study dates: 29 Apr 2021to 21 Nov 2022
Phase: Phase 2
Are there results?: Yes, posted in the registrySummary in the doctors' view

Key requirements

Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.

Ages 18 to 90 years
All sexes
Healthy volunteers accepted
Adult, Older adult

Who may be able to join

Healthy or has chronic medical condition(s) that are stable and well-controlled in the opinion of the investigator and that are not likely to require significant medical intervention through the end of study
Willing and able to comply with study visits and study-related procedures, including compliance with site precautionary requirements related to SARS-CoV-2 infection and transmission

Who cannot join

Positive RT-PCR test result for SARS-CoV-2 infection at screening or baseline
Positive serology test result for anti-SARS-CoV-2 antibodies at screening or baseline
COVID-19 diagnosis, positive SARS-CoV-2 infection, or positive SARS-CoV-2 serology at any time prior to screening
Previously received an investigational, authorized, or approved coronavirus vaccine (eg, SARS-CoV-2 vaccine, MERS-CoV vaccine)
Currently enrolled in, or has plans to enroll in, any interventional study to prevent or treat COVID-19
Received investigational or approved passive antibodies for SARS-CoV-2 infection prophylaxis ad defined in the protocol

Show all 12Show fewer

Received intravenous immunoglobulin (IVIG) or blood products in the last 3 months
Any physical examination findings and/or history of any illness that, in the opinion of the study investigator, might confound the results of the study or pose an additional risk to the subject by study participation
History of clinically significant cardiovascular, respiratory, hepatic, renal, gastrointestinal, endocrine, hematological, psychiatric or neurological disease, as assessed by the investigator, that may confound the results of the study or pose an additional risk to the subject by study participation
Medically attended acute illness or hospitalization (ie, >24 hours) for any reason within 30 days prior to screening
Clinical history of myocarditis and/or pericarditis
Note: Other protocol-defined Inclusion/ Exclusion Criteria apply

Trial locations and contacts

6 sites in 1 country.

City, postcode or hospital

6 sites in 1 country

United States6 sites

Regeneron Research Site
Dayton, Ohio, 45417
Regeneron Research Site
Hialeah, Florida, 33012
Regeneron Research Site
Little Rock, Arkansas, 72211
Regeneron Research Site
Miami, Florida, 33186
Regeneron Research Site
Orlando, Florida, 32789
Regeneron Research Site
Rogers, Arkansas, 72758

Other trials in United States

About this study

Official title: A Phase 2 Randomized, Open-Label, Parallel Group Study to Assess the Immunogenicity, Safety, and Tolerability of Moderna mRNA-1273 Vaccine Administered With Casirivimab+Imdevimab in Healthy Adult Volunteers

The primary objectives of the study are:

To evaluate the extent of effect, if any, of REGN10933+REGN10987 administration on vaccine-induced neutralizing antibody responses to SARS-CoV-2 by Moderna mRNA-1273
To evaluate the time interval required between REGN10933+REGN10987 administration and Moderna mRNA-1273 vaccination, to ensure no meaningful impact on vaccine-induced neutralizing antibody responses to SARS-CoV-2

The secondary objectives of the study are:

To quantify the alteration of antigen specificity of vaccine-induced SARS-CoV-2 antibody responses when administered with different dose regimens of REGN10933+REGN10987
To evaluate the safety and tolerability of REGN10933+REGN10987 and Moderna mRNA-1273 vaccine when administered in close succession
To assess the concentrations of REGN10933 and REGN10987 in serum over time in participants who receive REGN10933+REGN10987 and Moderna mRNA-1273 vaccine
To evaluate the immunogenicity of REGN10933 and REGN10987 over time

Conditions: Healthy, Chronic Stable Illness
Being tested: casirivimab+imdevimab, Moderna mRNA-1273 vaccine

What participants receive

What participants receive. In a randomised study each person is assigned to one group by chance.

casirivimab+imdevimabDrug
Also called REGN10933, REGN10987, REGN-COV2, REGEN-COV™
Wave 1 Intravenous (IV) administration Wave 2 Subcutaneous administration
Moderna mRNA-1273 vaccineBiological
Single intramuscular (IM) injection

Study groups in NCT04852978
Study group	Role	What they receive
Wave 1 Dose 1	Experimental	Not described Receives: Drug: casirivimab+imdevimab; Biological: Moderna mRNA-1273 vaccine
Wave 1 Dose 2	Experimental	Not described Receives: Drug: casirivimab+imdevimab; Biological: Moderna mRNA-1273 vaccine
Wave 1 Dose 3	Experimental	Not described Receives: Drug: casirivimab+imdevimab; Biological: Moderna mRNA-1273 vaccine
Wave 1 Vaccine only	Experimental	Not described Receives: Biological: Moderna mRNA-1273 vaccine
Wave 2 Dose 1	Experimental	Not described Receives: Drug: casirivimab+imdevimab; Biological: Moderna mRNA-1273 vaccine
Wave 2 Dose 2	Experimental	Not described Receives: Drug: casirivimab+imdevimab; Biological: Moderna mRNA-1273 vaccine
Wave 2 Vaccine only	Experimental	Not described Receives: Biological: Moderna mRNA-1273 vaccine
Wave 3 Dose 1	Experimental	Not described Receives: Drug: casirivimab+imdevimab; Biological: Moderna mRNA-1273 vaccine
Wave 3 Dose 2	Experimental	Not described Receives: Drug: casirivimab+imdevimab; Biological: Moderna mRNA-1273 vaccine
Wave 3 Vaccine only	Experimental	Not described Receives: Biological: Moderna mRNA-1273 vaccine
Wave 4 Dose 1	Experimental	Not described Receives: Drug: casirivimab+imdevimab; Biological: Moderna mRNA-1273 vaccine
Wave 4 Vaccine only	Experimental	Not described Receives: Biological: Moderna mRNA-1273 vaccine

What is being measured

The primary outcome is the main question the study is designed to answer.

50% Inhibitory Dilution (ID50) Titers of Vaccine-induced Neutralizing Antibodies to the SARS-CoV-2 S Protein in Individuals Who Received High Dose REGN10933+REGN10987 (1200 mg)
High dose - (1200 mg arms)
Measured: 56 days after first dose of vaccine
50% Inhibitory Dilution (ID50) Titers of Vaccine-induced Neutralizing Antibodies to the SARS-CoV-2 S Protein in Individual Who Received Submaximal Dose Levels of REGN10933+REGN10987 (Less Than 1200 mg)
Submaximal dose - (150 mg, 300 mg, 600 mg, 48 mg, and 12 mg)
Measured: 56 days after first dose of vaccine

Secondary outcomes (31)

Absolute Values in Concentrations of Vaccine-induced Antibodies to SARS-CoV-2 Antigens Over Time (S1-RBD IgA)
Anti-S1-RBD protein
Measured: Up to 365 Days from 1st dose of Vaccination
Median Fold Change of Concentrations of Vaccine-induced Antibodies to SARS-CoV-2 Antigens Over Time (S1-RBD IgA)
Anti-S1-RBD protein. Fold Change based on medians = (median value in vaccine only arm / median value in the active arm)
Measured: Up to 365 Days from 1st dose of Vaccination
Relative Difference Expressed as a Percent in Vaccine-induced Antibodies to SARS-CoV-2 Antigens Over Time (S1-RBD IgA)
Anti-S1-RBD protein. Relative difference is calculated as: [(LS Geometric Mean Active Arm - LS Geometric Mean Vaccine Alone Arm) / LS Geometric Mean Vaccine Alone Arm] x 100%
Measured: Up to 365 Days from 1st dose of Vaccination
Absolute Values in Concentrations of Vaccine-induced Antibodies to SARS-CoV-2 Antigens Over Time (S-IgA)
- Anti-S protein (Spike protein)
Measured: Up to 365 Days from 1st dose of Vaccination
Fold Change of Concentrations of Vaccine-induced Antibodies to SARS-CoV-2 Antigens Over Time (S-IgA)
Anti-S protein Fold Change based on medians = (median value in vaccine only arm / median value in the active arm)
Measured: Up to 365 Days from 1st dose of vaccination
Relative Difference Expressed as a Percent in Vaccine-induced Antibodies to SARS-CoV-2 Antigens Over Time (S-IgA)
Anti-S protein Relative difference is calculated as: [(LS Geometric Mean Active Arm - LS Geometric Mean Vaccine Alone Arm) / LS Geometric Mean Vaccine Alone Arm] x 100%
Measured: Up to 365 Days from 1st dose of Vaccination
Absolute Values in Concentrations of Vaccine-induced Antibodies to SARS-CoV-2 Antigens Over Time (S-IgG)
Anti-S protein
Measured: Up to 365 Days from 1st dose of vaccination
Fold Change of Concentrations of Vaccine-induced Antibodies to SARS-CoV-2 Antigens Over Time (S-IgG)
Anti-S protein Fold Change based on medians = (median value in vaccine only arm / median value in the active arm)
Measured: Up to 365 Days from 1st dose of vaccination
Relative Difference Expressed as a Percent in Vaccine-induced Antibodies to SARS-CoV-2 Antigens Over Time (S-IgG)
Anti-S protein (Spike) Relative difference is calculated as: [(LS Geometric Mean Active Arm - LS Geometric Mean Vaccine Alone Arm) / LS Geometric Mean Vaccine Alone Arm] x 100%
Measured: Up to 365 Days from 1st dose of vaccination
Absolute Values in Concentrations of Vaccine-induced Antibodies to SARS-CoV-2 Antigens Over Time (S1-RBD IgG)
Anti-S1-RBD
Measured: Up to 365 Days from 1st dose of vaccination
Fold Change of Concentrations of Vaccine-induced Antibodies to SARS-CoV-2 Antigens Over Time (S1-RBD IgG)
Anti-S1-RBD protein Fold Change based on medians = (median value in vaccine only arm / median value in the active arm)
Measured: Up to 365 Days from 1st dose of vaccination
Relative Difference Expressed as a Percent in Vaccine-induced Antibodies to SARS-CoV-2 Antigens Over Time (S1-RBD IgG)
Anti-S1-RBD protein Relative difference is calculated as: [(LS Geometric Mean Active Arm - LS Geometric Mean Vaccine Alone Arm) / LS Geometric Mean Vaccine Alone Arm] x 100%
Measured: Up to 365 Days from 1st dose of vaccination
Absolute Values in Concentrations of Vaccine-induced Antibodies to SARS-CoV-2 Antigens Over Time (S1-RBD IgM)
Anti-S1-RBD
Measured: Up to 365 Days from 1st dose of vaccination
Relative Difference Expressed as a Percent in Vaccine-induced Antibodies to SARS-CoV-2 Antigens Over Time (S1-RBD IgM)
Anti-S1-RBD protein Relative difference is calculated as: [(LS Geometric Mean Active Arm - LS Geometric Mean Vaccine Alone Arm) / LS Geometric Mean Vaccine Alone Arm] x 100%
Measured: Up to 365 Days from 1st dose of vaccination
Fold Change of Concentrations of Vaccine-induced Antibodies to SARS-CoV-2 Antigens Over Time (S1-RBD IgM)
Anti-S1-RBD protein Fold Change based on medians = (median value in vaccine only arm / median value in the active arm)
Measured: Up to 365 Days from 1st dose of vaccination
Absolute Values in Concentrations of Vaccine-induced Antibodies to SARS-CoV-2 Antigens Over Time (S-IgM)
Anti-S protein (Spike protein)
Measured: Up to 365 Days from 1st dose of vaccination
Relative Difference Expressed as a Percent in Concentrations of Vaccine-induced Antibodies to SARS-CoV-2 Antigens Over Time (S-IgM)
Anti-S protein (Spike protein) Relative difference is calculated as: [(LS Geometric Mean Active Arm - LS Geometric Mean Vaccine Alone Arm) / LS Geometric Mean Vaccine Alone Arm] x 100%
Measured: Up to 365 Days from 1st dose of vaccination
Fold Change of Concentrations of Vaccine-induced Antibodies to SARS-CoV-2 Antigens Over Time (S-IgM)
Anti-S protein (Spike protein) Fold Change based on medians = (median value in vaccine only arm / median value in the active arm)
Measured: Up to 365 Days from 1st dose of vaccination
50% Inhibitory Dilution (ID50) Titers of Vaccine-induced Neutralizing Antibodies to SARS-CoV-2 S Protein Assessed Over Time After the First Dose of Moderna mRNA-1273 Vaccine
Measured: Up to 365 Days from 1st dose of vaccination
Number of Participants With Treatment-emergent Adverse Events (TEAEs) Throughout the Study
Measured: Up to 401 Days
Number of Participants With Treatment-emergent Serious Adverse Events (SAEs) Throughout the Study
Measured: Up to 401 Days
Number of Participants With Infusion-related Reactions (Grade ≥2) to REGN10933+REGN10987
Measured: Through Day 4 post-infusion
Number of Participants With Injection Site Reactions (Grade ≥3) to REGN10933+REGN10987
Measured: Through Day 4 post-infusion
Number of Participants With Injection Site Reactions (Grade ≥3) to Moderna mRNA-1273 Vaccine
Measured: Through Day 4 post-infusion
Number of Participants With Hypersensitivity Reactions (Grade ≥2) to REGN10933+REGN10987 or Each Dose of Moderna mRNA-1273 Vaccine
Grade 2 - characterized by an adverse local or general response from exposure and oral intervention indicated Grade 3 - hospitalization indicated and intravenous response required Grade 4 - Life Threatening consequence and urgent intervention indicated Grade 5 - Death
Measured: Through Day 29 post-infusion or post-injection
Concentrations of REGN10933 in Serum Over Time
Measured: Up to 182 Days
Concentrations of REGN10987 in Serum Over Time
Measured: Up to 182 Days
Immunogenicity, as Measured by Anti-drug Antibodies (ADA) to REGN10987
Measured: Up to Day 183
Immunogenicity, as Measured by Anti-drug Antibodies (ADA) to REGN10933
Measured: Up to Day 183
Immunogenicity, as Measured by Neutralizing Antibodies (NAb) to REGN10987
Measured: Up to Day 183
Immunogenicity, as Measured by Neutralizing Antibodies (NAb) to REGN10933
Measured: Up to Day 183

Timeline

From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.

29 Apr 202121 Nov 2022

First posted21 Apr 2021
Study start29 Apr 2021
Primary completion21 Nov 2022
Study completion21 Nov 2022

Resources

Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
Posted resultsParticipant flow, outcome measures and adverse events reported by the sponsor.
Publications (1)Papers the sponsor has linked to this study.
Other trials for HealthyStudies of the same condition, open and under way.
More trials run by Regeneron PharmaceuticalsThe sponsor's other registered studies.
What the trial phases meanHow a treatment moves from first tests in people to approval.

More details

For doctors and researchers: how the study is designed, who runs it, and its registry IDs.

Study design

Study type: Interventional
Phase: Phase 2
Primary purpose: Treatment
Allocation: Randomised
Intervention model: Parallel groups
Masking: None (open label)
Enrolment: 295 participants (actual)

IDs, dates and publications

ClinicalTrials.gov ID: NCT04852978
Sponsor's protocol ID: R10933-10987-COV-2118
Status last verified: Oct 2025
First submitted: 19 Apr 2021
Last updated: 20 Oct 2025
Results posted: Yes, on ClinicalTrials.gov
Data monitoring committee: No
FDA-regulated drug: Yes
FDA-regulated device: No
Individual data sharing: Yes: All Individual Patient Data (IPD) that underlie publicly available results will be considered for sharing

Publications

Isa F, Gonzalez Ortiz AM, Meyer J, Hamilton JD, Olenchock BA, Brackin T, Ganguly S, Forleo-Neto E, Faria L, Heirman I, Marovich M, Hutter J, Polakowski L, Irvin SC, Thakur M, Hooper AT, Baum A, Petro CD, Fakih FA, McElrath MJ, De Rosa SC, Cohen KW, Williams LD, Hellman CA, Odeh AJ, Patel AH, Tomaras GD, Geba GP, Kyratsous CA, Musser B, Yancopoulos GD, Herman GA; Trial Working Group. Effect of timing of casirivimab and imdevimab administration relative to mRNA-1273 COVID-19 vaccination on vaccine-induced SARS-CoV-2 neutralising antibody responses: a prospective, open-label, phase 2, randomised controlled trial. Lancet Infect Dis. 2025 Jan;25(1):52-67. doi: 10.1016/S1473-3099(24)00421-3. Epub 2024 Sep 2.
PubMed 39236733

Want to know more?

The sponsor has not listed a contact. The official record may have more details.

Talk to your doctor first and take this page with you. Only the study team can confirm whether you can join.

Questions to ask the study team

What is the study trying to find out?
What would I need to do, and how often would I visit?
Could I receive a placebo instead of the treatment?
What are the possible risks and benefits for me?
Will it cost me anything? Are travel or time paid for?
Can I keep seeing my own doctor during the study?
What happens when the study ends?

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Study at a glance

From the registry record, last updated by the sponsor on 20 Oct 2025. Recruitment status is as the sponsor reported it: confirm with the study team.

Official title: A Phase 2 Randomized, Open-Label, Parallel Group Study to Assess the Immunogenicity, Safety, and Tolerability of Moderna mRNA-1273 Vaccine Administered With Casirivimab+Imdevimab in Healthy Adult Volunteers
ClinicalTrials.gov ID: NCT04852978
Acronym / sponsor ID: R10933-10987-COV-2118
Conditions: Healthy, Chronic Stable Illness
Phase: Phase 2
Study type: Interventional
Recruitment status: Completed
Enrolment: 295 participants (actual)
Lead sponsor: Regeneron PharmaceuticalsIndustry (pharma, biotech, devices)
Study start: 29 Apr 2021 (actual)
Primary completion: 21 Nov 2022 (actual)
Study completion: 21 Nov 2022 (actual)
First posted: 21 Apr 2021 (actual)
Results: Posted 20 Aug 2024

Clinical summary

The research question as the sponsor registered it. This describes what the study plans to test, not what it found.

The primary objectives of the study are:

To evaluate the extent of effect, if any, of REGN10933+REGN10987 administration on vaccine-induced neutralizing antibody responses to SARS-CoV-2 by Moderna mRNA-1273
To evaluate the time interval required between REGN10933+REGN10987 administration and Moderna mRNA-1273 vaccination, to ensure no meaningful impact on vaccine-induced neutralizing antibody responses to SARS-CoV-2

The secondary objectives of the study are:

To quantify the alteration of antigen specificity of vaccine-induced SARS-CoV-2 antibody responses when administered with different dose regimens of REGN10933+REGN10987
To evaluate the safety and tolerability of REGN10933+REGN10987 and Moderna mRNA-1273 vaccine when administered in close succession
To assess the concentrations of REGN10933 and REGN10987 in serum over time in participants who receive REGN10933+REGN10987 and Moderna mRNA-1273 vaccine
To evaluate the immunogenicity of REGN10933 and REGN10987 over time

Study design

Primary purpose: Treatment
Allocation: Randomised
Intervention model: Parallel groups
Masking: None (open label)
Number of arms: 12

Arm	Type	Receives
Wave 1 Dose 1	Experimental	Drug: casirivimab+imdevimab, Biological: Moderna mRNA-1273 vaccine
Wave 1 Dose 2	Experimental	Drug: casirivimab+imdevimab, Biological: Moderna mRNA-1273 vaccine
Wave 1 Dose 3	Experimental	Drug: casirivimab+imdevimab, Biological: Moderna mRNA-1273 vaccine
Wave 1 Vaccine only	Experimental	Biological: Moderna mRNA-1273 vaccine
Wave 2 Dose 1	Experimental	Drug: casirivimab+imdevimab, Biological: Moderna mRNA-1273 vaccine
Wave 2 Dose 2	Experimental	Drug: casirivimab+imdevimab, Biological: Moderna mRNA-1273 vaccine
Wave 2 Vaccine only	Experimental	Biological: Moderna mRNA-1273 vaccine
Wave 3 Dose 1	Experimental	Drug: casirivimab+imdevimab, Biological: Moderna mRNA-1273 vaccine
Wave 3 Dose 2	Experimental	Drug: casirivimab+imdevimab, Biological: Moderna mRNA-1273 vaccine
Wave 3 Vaccine only	Experimental	Biological: Moderna mRNA-1273 vaccine
Wave 4 Dose 1	Experimental	Drug: casirivimab+imdevimab, Biological: Moderna mRNA-1273 vaccine
Wave 4 Vaccine only	Experimental	Biological: Moderna mRNA-1273 vaccine

Who may qualify

Ages: 18 to 90 years
Sex: All
Healthy volunteers: Accepted
Age groups: Adult, Older adult

Key inclusion criteria (2 listed)

Healthy or has chronic medical condition(s) that are stable and well-controlled in the opinion of the investigator and that are not likely to require significant medical intervention through the end of study
Willing and able to comply with study visits and study-related procedures, including compliance with site precautionary requirements related to SARS-CoV-2 infection and transmission

Key exclusion criteria (12 listed)

Positive RT-PCR test result for SARS-CoV-2 infection at screening or baseline
Positive serology test result for anti-SARS-CoV-2 antibodies at screening or baseline
COVID-19 diagnosis, positive SARS-CoV-2 infection, or positive SARS-CoV-2 serology at any time prior to screening
Previously received an investigational, authorized, or approved coronavirus vaccine (eg, SARS-CoV-2 vaccine, MERS-CoV vaccine)
Currently enrolled in, or has plans to enroll in, any interventional study to prevent or treat COVID-19

Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.

Interventions

Intervention	Type	Arms
casirivimab+imdevimabAlso: REGN10933, REGN10987, REGN-COV2, REGEN-COV™Wave 1 Intravenous (IV) administration Wave 2 Subcutaneous administration	Drug	Wave 1 Dose 1, Wave 1 Dose 2, Wave 1 Dose 3, Wave 2 Dose 1, Wave 2 Dose 2, Wave 3 Dose 1, Wave 3 Dose 2, Wave 4 Dose 1
Moderna mRNA-1273 vaccineSingle intramuscular (IM) injection	Biological	Wave 1 Dose 1, Wave 1 Dose 2, Wave 1 Dose 3, Wave 1 Vaccine only, Wave 2 Dose 1, Wave 2 Dose 2, Wave 2 Vaccine only, Wave 3 Dose 1, Wave 3 Dose 2, Wave 3 Vaccine only, Wave 4 Dose 1, Wave 4 Vaccine only

Primary outcome

50% Inhibitory Dilution (ID50) Titers of Vaccine-induced Neutralizing Antibodies to the SARS-CoV-2 S Protein in Individuals Who Received High Dose REGN10933+REGN10987 (1200 mg)
Time frame: 56 days after first dose of vaccine
High dose - (1200 mg arms)
50% Inhibitory Dilution (ID50) Titers of Vaccine-induced Neutralizing Antibodies to the SARS-CoV-2 S Protein in Individual Who Received Submaximal Dose Levels of REGN10933+REGN10987 (Less Than 1200 mg)
Time frame: 56 days after first dose of vaccine
Submaximal dose - (150 mg, 300 mg, 600 mg, 48 mg, and 12 mg)

31 secondary outcomes

Absolute Values in Concentrations of Vaccine-induced Antibodies to SARS-CoV-2 Antigens Over Time (S1-RBD IgA)
Time frame: Up to 365 Days from 1st dose of Vaccination
Median Fold Change of Concentrations of Vaccine-induced Antibodies to SARS-CoV-2 Antigens Over Time (S1-RBD IgA)
Time frame: Up to 365 Days from 1st dose of Vaccination
Relative Difference Expressed as a Percent in Vaccine-induced Antibodies to SARS-CoV-2 Antigens Over Time (S1-RBD IgA)
Time frame: Up to 365 Days from 1st dose of Vaccination
Absolute Values in Concentrations of Vaccine-induced Antibodies to SARS-CoV-2 Antigens Over Time (S-IgA)
Time frame: Up to 365 Days from 1st dose of Vaccination
Fold Change of Concentrations of Vaccine-induced Antibodies to SARS-CoV-2 Antigens Over Time (S-IgA)
Time frame: Up to 365 Days from 1st dose of vaccination
Relative Difference Expressed as a Percent in Vaccine-induced Antibodies to SARS-CoV-2 Antigens Over Time (S-IgA)
Time frame: Up to 365 Days from 1st dose of Vaccination
Absolute Values in Concentrations of Vaccine-induced Antibodies to SARS-CoV-2 Antigens Over Time (S-IgG)
Time frame: Up to 365 Days from 1st dose of vaccination
Fold Change of Concentrations of Vaccine-induced Antibodies to SARS-CoV-2 Antigens Over Time (S-IgG)
Time frame: Up to 365 Days from 1st dose of vaccination
Relative Difference Expressed as a Percent in Vaccine-induced Antibodies to SARS-CoV-2 Antigens Over Time (S-IgG)
Time frame: Up to 365 Days from 1st dose of vaccination
Absolute Values in Concentrations of Vaccine-induced Antibodies to SARS-CoV-2 Antigens Over Time (S1-RBD IgG)
Time frame: Up to 365 Days from 1st dose of vaccination
Fold Change of Concentrations of Vaccine-induced Antibodies to SARS-CoV-2 Antigens Over Time (S1-RBD IgG)
Time frame: Up to 365 Days from 1st dose of vaccination
Relative Difference Expressed as a Percent in Vaccine-induced Antibodies to SARS-CoV-2 Antigens Over Time (S1-RBD IgG)
Time frame: Up to 365 Days from 1st dose of vaccination
Absolute Values in Concentrations of Vaccine-induced Antibodies to SARS-CoV-2 Antigens Over Time (S1-RBD IgM)
Time frame: Up to 365 Days from 1st dose of vaccination
Relative Difference Expressed as a Percent in Vaccine-induced Antibodies to SARS-CoV-2 Antigens Over Time (S1-RBD IgM)
Time frame: Up to 365 Days from 1st dose of vaccination
Fold Change of Concentrations of Vaccine-induced Antibodies to SARS-CoV-2 Antigens Over Time (S1-RBD IgM)
Time frame: Up to 365 Days from 1st dose of vaccination
Absolute Values in Concentrations of Vaccine-induced Antibodies to SARS-CoV-2 Antigens Over Time (S-IgM)
Time frame: Up to 365 Days from 1st dose of vaccination
Relative Difference Expressed as a Percent in Concentrations of Vaccine-induced Antibodies to SARS-CoV-2 Antigens Over Time (S-IgM)
Time frame: Up to 365 Days from 1st dose of vaccination
Fold Change of Concentrations of Vaccine-induced Antibodies to SARS-CoV-2 Antigens Over Time (S-IgM)
Time frame: Up to 365 Days from 1st dose of vaccination
50% Inhibitory Dilution (ID50) Titers of Vaccine-induced Neutralizing Antibodies to SARS-CoV-2 S Protein Assessed Over Time After the First Dose of Moderna mRNA-1273 Vaccine
Time frame: Up to 365 Days from 1st dose of vaccination
Number of Participants With Treatment-emergent Adverse Events (TEAEs) Throughout the Study
Time frame: Up to 401 Days
Number of Participants With Treatment-emergent Serious Adverse Events (SAEs) Throughout the Study
Time frame: Up to 401 Days
Number of Participants With Infusion-related Reactions (Grade ≥2) to REGN10933+REGN10987
Time frame: Through Day 4 post-infusion
Number of Participants With Injection Site Reactions (Grade ≥3) to REGN10933+REGN10987
Time frame: Through Day 4 post-infusion
Number of Participants With Injection Site Reactions (Grade ≥3) to Moderna mRNA-1273 Vaccine
Time frame: Through Day 4 post-infusion
Number of Participants With Hypersensitivity Reactions (Grade ≥2) to REGN10933+REGN10987 or Each Dose of Moderna mRNA-1273 Vaccine
Time frame: Through Day 29 post-infusion or post-injection
Concentrations of REGN10933 in Serum Over Time
Time frame: Up to 182 Days
Concentrations of REGN10987 in Serum Over Time
Time frame: Up to 182 Days
Immunogenicity, as Measured by Anti-drug Antibodies (ADA) to REGN10987
Time frame: Up to Day 183
Immunogenicity, as Measured by Anti-drug Antibodies (ADA) to REGN10933
Time frame: Up to Day 183
Immunogenicity, as Measured by Neutralizing Antibodies (NAb) to REGN10987
Time frame: Up to Day 183
Immunogenicity, as Measured by Neutralizing Antibodies (NAb) to REGN10933
Time frame: Up to Day 183

Results and safety

Results posted to the registry on 20 Aug 2024, as reported by the sponsor. Figures are copied from the record, not re-analysed. Full results on ClinicalTrials.gov.

Participant flow

Group	Started	Completed
Vaccine Only	48	41
REGN10933+REGN10987 + Vaccine 1200 mg Day 1 IV	28	23
REGN10933+REGN10987 + Vaccine 300 mg Day 1 IV	29	24
REGN10933+REGN10987 + Vaccine 150 mg Day 1 IV	28	27
REGN10933+REGN10987 + Vaccine 48 mg Day 1 IV	33	26
REGN10933+REGN10987 + Vaccine 12 mg Day 1 IV	31	24
REGN10933+REGN10987 + Vaccine 1200 mg Day 7 IV	26	22
REGN10933+REGN10987 + Vaccine 1200 mg Day 1 SC	35	29
REGN10933+REGN10987 + Vaccine 600 mg Day 1 SC	35	32

Primary outcome: 50% Inhibitory Dilution (ID50) Titers of Vaccine-induced Neutralizing Antibodies to the SARS-CoV-2 S Protein in Individuals Who Received High Dose REGN10933+REGN10987 (1200 mg)

Time frame: 56 days after first dose of vaccine. Mean (Standard Deviation). Unit: Titer

Measure	Vaccine Only n = 41	REGN10933+REGN10987 + Vaccine 1200 mg Day 1 IV n = 24	REGN10933+REGN10987 + Vaccine 1200 mg Day 1 SC n = 32	REGN10933+REGN10987 + Vaccine 1200 mg Day 7 IV n = 22
Value	2594.9 (1981.5)	1818.6 (2365.8)	980.8 (1015.1)	2576.8 (2736.1)

Population analysed: Per protocol set (PPS) includes all randomized participants who have received both doses of vaccine and who do not meet the exclusion criteria. The PPS is the primary analysis set for assessing vaccine response related endpoints.

Primary outcome: 50% Inhibitory Dilution (ID50) Titers of Vaccine-induced Neutralizing Antibodies to the SARS-CoV-2 S Protein in Individual Who Received Submaximal Dose Levels of REGN10933+REGN10987 (Less Than 1200 mg)

Time frame: 56 days after first dose of vaccine. Mean (Standard Deviation). Unit: Titer

Measure	Vaccine Only n = 41	REGN10933+REGN10987 + Vaccine 300 mg Day 1 IV n = 26	REGN10933+REGN10987 + Vaccine 150 mg Day 1 IV n = 26	REGN10933+REGN10987 + Vaccine 48 mg Day 1 IV n = 28	REGN10933+REGN10987 + Vaccine 12 mg Day 1 IV n = 24	REGN10933+REGN10987 + Vaccine 600 mg Day 1 SC n = 31
Value	2594.9 (1981.5)	780.8 (771.1)	716.1 (664.9)	4922.8 (11157.3)	2422.2 (2882.7)	1549.5 (4334.1)

31 secondary outcomes are reported in the full results.

Adverse events

Time frame: Up to 401 Days. Other adverse events reported at 5% frequency or more

Group	Serious adverse events	Other adverse events	Deaths
Vaccine Only Total All	2 of 48 (4.2%)	11 of 48 (22.9%)	0 of 48
REGN10933+REGN10987 + Vaccine 1200 mg Day 1 IV	0 of 28 (0%)	13 of 28 (46.4%)	0 of 28
REGN10933+REGN10987 + Vaccine 300 mg Day 1 IV	0 of 29 (0%)	9 of 29 (31%)	0 of 29
REGN10933+REGN10987 + Vaccine 150 mg Day 1 IV	0 of 28 (0%)	14 of 28 (50%)	0 of 28
REGN10933+REGN10987 + Vaccine 1200 mg Day 1 SC	1 of 35 (2.9%)	15 of 35 (42.9%)	0 of 35
REGN10933+REGN10987 + Vaccine 600 mg Day 1 SC	0 of 35 (0%)	23 of 35 (65.7%)	0 of 35
REGN10933+REGN10987 + Vaccine 48 mg Day 1 IV	0 of 33 (0%)	12 of 33 (36.4%)	0 of 33
REGN10933+REGN10987 + Vaccine 12 mg Day 1 IV	0 of 31 (0%)	14 of 31 (45.2%)	0 of 31
REGN10933+REGN10987 + Vaccine 1200 mg Day 7 IV	2 of 26 (7.7%)	9 of 26 (34.6%)	1 of 26

Loading the posted results from ClinicalTrials.gov…

Research links

Official record on ClinicalTrials.govLast updated by the sponsor 20 Oct 2025.
Posted resultsParticipant flow, baseline, all outcome measures and adverse events.
Derived from this study: PubMed 39236733Isa F, Gonzalez Ortiz AM, Meyer J, Hamilton JD, Olenchock BA, Brackin T, Ganguly S, Forleo-Neto E, Faria L, Heirman I, Marovich M, Hutter J, Polakowski L, Irvin SC, Thakur M, Hooper AT, Baum A, Petro CD, Fakih FA, McElrath MJ, De Rosa SC, Cohen KW, Williams LD, Hellman CA, Odeh AJ, Patel AH, Tomaras GD, Geba GP, Kyratsous CA, Musser B, Yancopoulos GD, Herman GA; Trial Working Group. Effect of timing of casirivimab and imdevimab administration relative to mRNA-1273 COVID-19 vaccination on vaccine-induced SARS-CoV-2 neutralising antibody responses: a prospective, open-label, phase 2, randomised controlled trial. Lancet Infect Dis. 2025 Jan;25(1):52-67. doi: 10.1016/S1473-3099(24)00421-3. Epub 2024 Sep 2.
Individual participant dataSharing planned: Yes. All Individual Patient Data (IPD) that underlie publicly available results will be considered for sharing

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Referral and contact

AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part. This study is not recruiting at the moment.

Clinical Trial Management study director

Regeneron Pharmaceuticals

6 sites in 1 country: see every site and its status.

Questions about this trial

What is this clinical trial studying?

A Phase 2 study testing casirivimab+imdevimab and Moderna mRNA-1273 vaccine in people with Healthy and Chronic Stable Illness, run by Regeneron Pharmaceuticals at 6 sites in United States.

The full registered description is in the About this study section and the official record.

Who may be eligible to take part?

The sponsor lists 2 inclusion and 12 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.

Is this clinical trial currently recruiting?

The record says: finished, as of the sponsor's last update on 20 Oct 2025. Status can change between updates, so confirm with the study contact before making plans.

Where is the study taking place?

The record lists 6 sites in United States. Whether a site is taking part right now should be confirmed with that site. See every site.

What are the possible benefits and risks?

They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.

What does this phase mean?

Phase 2 studies give the treatment to a larger group to see whether it has the intended effect and to keep checking safety.

Not every study follows the same path, and some studies (observational studies, device studies) have no phase.

Are results available for this study?

Yes. Results are posted in the registry (first posted 20 Aug 2024). A summary is in the For doctors view, and the full results are on ClinicalTrials.gov.

How can a doctor refer a patient or contact the research team?

The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.

What does the primary outcome measure?

50% Inhibitory Dilution (ID50) Titers of Vaccine-induced Neutralizing Antibodies to the SARS-CoV-2 S Protein in Individuals Who Received High Dose REGN10933+REGN10987 (1200 mg) (time frame: 56 days after first dose of vaccine). The study lists 2 primary outcomes in all. It is what the study was designed to measure, not a finding.

Where can I read the original study information?

On the ClinicalTrials.gov record for NCT04852978, which also lists 1 linked publication.

Does a listing mean the treatment is approved or proven to work?

No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.

How often is this information updated?

AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 20 Oct 2025.