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TerminatedNCT05081388Updated Oct 28, 2025Results posted

COVID-19 Study to Evaluate Safety, Tolerability, and Efficacy of REGN14256+Imdevimab for the Treatment of COVID-19 Adult and Adolescent Patients Without Risk Factors for Progression to Severe Disease

A Phase 1/2 interventional study of REGN14256 and imdevimab in SARS-CoV-2, sponsored by Regeneron Pharmaceuticals. Terminated at 28 sites in United States. Open to participants aged 12 Years to 65 Years. Per ClinicalTrials.gov, last updated 2025-10-28.

Sponsored by Regeneron Pharmaceuticals · Phase 1/2, Interventional, and Treatment

Why this study was terminated
Sponsor Decision
Phase
Phase 1/2
Study type
Interventional
Enrollment
25
Allocation
Randomized
Ages
12 Years to 65 Years
Sex
All
01

Study summary

Primary Objectives Phase 1 (Safety and Tolerability)

  • Evaluate the safety and tolerability of REGN14256+imdevimab and REGN14256 monotherapy, as measured by treatment-emergent adverse events (TEAEs), injection-site reactions (ISRs), and hypersensitivity reactions

Phase 1/2 (Virologic Efficacy) • Evaluate the virologic efficacy of REGN14256+imdevimab and REGN14256 monotherapy compared to placebo, as measured by time-weighted average (TWA) change from baseline in viral load through day 7

Phase 1/2/3 (Clinical Efficacy)

  • Evaluate the clinical efficacy of REGN14256+imdevimab compared to placebo, as measured by COVID-19 symptoms resolution

Secondary Objectives Phase 1 (Safety and Tolerability) • Evaluate the safety and tolerability of REGN14256+imdevimab and REGN14256 monotherapy, as measured by treatment-emergent serious adverse events (SAEs)

Phase 2 and Phase 3 (Safety and Tolerability)

  • Evaluate the safety and tolerability of REGN14256+imdevimab and REGN14256 monotherapy, as measured by TEAEs, ISRs, hypersensitivity reactions, and SAEs

Phase 1, Phase 2, and Phase 3 (Virologic Efficacy, Drug Concentration, and Immunogenicity)

  • Evaluate additional indicators of virologic efficacy of REGN14256+imdevimab and REGN14256 monotherapy
  • Characterize the concentration-time profile of REGN14256 administered in combination with imdevimab or alone as a monotherapy
  • Assess the immunogenicity of REGN14256 administered in combination with imdevimab or alone as a monotherapy
02

Conditions studied

  • SARS-CoV-2

Keywords

  • COVID-19
  • Non-hospitalized
  • Low-risk
  • Symptomatic
  • Coronavirus disease 2019 (COVID-19)
  • Severe acute respiratory syndrome coronavirus 2 (SARS-COV-2)
  • coronavirus
03

In context

COVID-19

7,640 studies on the registry are indexed under COVID-19; 488 are open to participants now.

This study's enrollment of 25 is below the median of 100 across 4,099 interventional studies indexed under COVID-19.

Browse COVID-19 studies →

Lead sponsor

Regeneron Pharmaceuticals is the lead sponsor of 400 studies on the registry; 91 are open to participants now.

Of its 120 completed or terminated interventional studies of FDA-regulated products, 77 (64%) have results posted.

Counted across the registry records on this site, refreshed daily.

04

Who can participate

Ages eligible
12 Years to 65 Years
Sexes eligible
All
Accepts healthy volunteers
No

Eligibility criteria

Phase 1 will enroll adult patients (≥18 years of age), Phase 2 will enroll adult patients, Phase 3 will enroll adult patients and an additional adolescent cohort of patients (≥12 and \<18 years of age)

Key Inclusion Criteria:

  1. For the adolescent cohort in Phase 3 only: Weighs ≥40 kg at randomization
  2. Has SARS-CoV-2-positive antigen or molecular diagnostic test (by validated SARSCoV-2 antigen, RT-PCR, or other molecular diagnostic assay, using an appropriate sample such as nasopharyngeal [NP], nasal, oropharyngeal [OP], or saliva) ≤72 hours prior to randomization. A historical record of a positive result is acceptable as long as the sample was collected ≤72 hours prior to randomization
  3. Has symptoms consistent with COVID-19 (as determined by the investigator) with onset ≤7 days before randomization, and doesn't have a medical condition or other factors associated with high risk for progression to severe COVID-19 as outlined in the exclusion criteria
  4. Maintains O2 saturation ≥93% on room air

Key Exclusion Criteria:

  1. Has a medical condition or other factors associated with high risk for progression to severe COVID-19:

    1. Cancer
    2. Cardiovascular disease (such as heart failure, coronary artery disease, cardiomyopathies, congenital heart disease or hypertension)
    3. Chronic lung disease including chronic obstructive pulmonary disease, asthma (moderate to severe), interstitial lung disease, cystic fibrosis, and pulmonary hypertension
    4. Chronic kidney disease at any stage
    5. Chronic liver disease (such as alcohol-related, nonalcoholic fatty liver disease, cirrhosis)
    6. Dementia or other chronic neurological condition
    7. Diabetes mellitus (type 1 or type 2)
    8. Immunodeficiency disease or taking immunosuppressive treatment
    9. Medical-related technological dependence [for example, tracheostomy, gastrostomy, or positive pressure ventilation (not related to COVID-19)]
    10. Neurodevelopmental disorder (for example, cerebral palsy) or other condition that confers medical complexity (for example, genetic or metabolic syndromes and severe congenital anomalies)
    11. Overweight (defined as BMI >25 kg/m2) or obesity (defined as BMI ≥30 kg/m2)
    12. Poorly controlled HIV infection or AIDS
    13. Pregnancy
    14. Sickle cell disease or thalassemia
    15. Stroke or cerebrovascular disease
  2. Prior, current (at randomization) or planned use (within time period given per CDC guidance [90 days]) of any authorized or approved vaccine for COVID-19
  3. Was admitted to a hospital for COVID-19 prior to randomization, or is hospitalized (inpatient) for any reason at randomization
  4. Has a known prior SARS-CoV-2 infection or positive SARS-CoV-2 serologic test
  5. Has a positive SARS-CoV-2 antigen or molecular diagnostic test from a sample collected >72 hours prior to randomization
  6. Has participated, or is participating, in a clinical research study evaluating COVID-19 convalescent plasma, mAbs against SARS-CoV-2, or intravenous immunoglobulin (IVIG) within 3 months or within 5 half-lives of the investigational product (whichever is longer) prior to the screening visit
  7. Prior, current, or any of the following treatments: COVID-19 convalescent plasma, mAbs against SARS-CoV-2, IVIG (any indication), systemic corticosteroids (any indication), or COVID-19 treatments (authorized, approved, or investigational)
  8. Has known active infection with influenza or other non-SARS-CoV-2 respiratory pathogen, confirmed by a diagnostic test
  9. Has been discharged, or is planned to be discharged, to a quarantine center
  10. Has participated, is participating, or plans to participate in a clinical research study evaluating any authorized, approved, or investigational vaccine for COVID-19
  11. For Phase 1only: Women of childbearing potential (WOCBP) who are unwilling to practice highly effective contraception prior to the initial dose/start of the first treatment and for at least 6 months after study drug administration as described in the protocol

Note: Other protocol-defined inclusion/ exclusion criteria apply

05

Study design

Phase
Phase 1 / Phase 2
Primary purpose
Treatment
Allocation
Randomized
Intervention model
Parallel assignment
Masking
Quadruple (Participant, Care provider, Investigator, Outcomes assessor)
Enrollment
25 participants (actual)

Study arms

  • Experimental
    REGN14256 + imdevimab

    Phase 1, Phase 2: Randomized 1:1:1:1:1 Phase 3: (≥18 Years): Randomized 1:1:1 Phase 3: (Open label) (≥12 and \<18 Years)

    Drug: REGN14256 · Drug: imdevimab

  • Experimental
    REGN14256

    Phase 1, Phase 2: Randomized 1:1:1:1:1

    Drug: REGN14256

  • Experimental
    Imdevimab

    Phase 1, Phase 2: Randomized 1:1:1:1:1

    Drug: imdevimab

  • Experimental
    casirivimab + imdevimab

    Phase 1, Phase 2: Randomized 1:1:1:1:1 Phase 3: (≥18 Years): Randomized 1:1:1

    Drug: imdevimab · Drug: casirivimab + imdevimab

  • Experimental
    Placebo

    Phase 1, Phase 2: Randomized 1:1:1:1:1 Phase 3: (≥18 Years): Randomized 1:1:1

    Drug: Placebo

Interventions

  • DrugREGN14256

    Sub-cutaneous (SC) single dose

  • Drugimdevimab

    SC single dose

    Also known as: REGN10987

  • Drugcasirivimab + imdevimab

    SC single dose

    Also known as: REGN10933 + REGN10987, REGN-COV2, REGEN-COV™, Ronapreve™

  • DrugPlacebo

    SC single dose

06

What researchers measure

Primary outcomes

  1. Treatment Emergent Adverse Events (TEAEs)

    Phase 1

    Time frame: Through Day 29

  2. Severity of TEAEs

    Severity was based on Grading. Grade 1 was less severe. Grade 5 was more severe. 1. \- Mild; Asymptomatic or mild symptoms; clinical or diagnostic observations only; intervention not indicated 2. \- Moderate; Minimal, local, or noninvasive intervention indicated; limiting age appropriate instrumental activities of daily living (ADL) 3. \- Severe; Severe or medically significant but not immediately life threatening; hospitalization or prolongation of hospitalization indicated; disabling; ADL2 limiting self-care 4. \- Life-threatening; Life threatening consequences; urgent intervention indicated 5. \- Death; Death related to adverse events

    Time frame: Through Day 29

  3. Percentage of Participants With Injection-site Reactions (ISRs)

    Phase 1 only

    Time frame: Through Day 169

  4. Severity of ISRs (Injection Site Reactions)

    Severity was based on Grading. Grade 1 was less severe. Grade 5 was more severe. Grade 1 - Tenderness with or without associated symptoms (eg, warmth, erythema, itching) Grade 2 - Pain; lipodystrophy; edema; phlebitis Grade 3 - Ulceration or necrosis; severe tissue damage; operative intervention indicated Grade 4 - Life-threatening consequences; urgent intervention indicated Grade 5 - Death

    Time frame: Through Day 29

  5. Percentage of Participants With Hypersensitivity Reactions

    Phase 1

    Time frame: Through Day 169

  6. Severity of Hypersensitivity Reactions Over Time

    Grade 1 - Systemic intervention not indicated. Grade 2 - Oral intervention indicated Grade 3 - Bronchospasm; hospitalization indicated for clinical sequelae; intravenous intervention indicated Grade 4 - Life-threatening consequences; urgent intervention indicated Grade 5 - Death

    Time frame: Through Day 169

  7. Time-weighted Average (TWA) Daily Change From Baseline in Viral Load (log10 Copies/mL)

    Phase 1 Measured by SARS-CoV-2 quantitative reverse transcription polymerase chain reaction (RT-qPCR) in nasopharyngeal (NP) swab samples

    Time frame: Day 1 to day 7

Secondary outcomes

  1. Percentage of Participants With Treatment-emergent Serious Adverse Events (SAEs)

    Phase 1

    Time frame: Through Day 169

  2. TEAEs (Treatment-Emergent Adverse Events)

    Phase 2 and Phase 3

    Time frame: Through Day 29

  3. Severity of TEAEs (Treatment-Emergent Adverse Event)

    Phase 2 and Phase 3

    Time frame: Through Day 29

  4. Percentage of Participants With ISRs (Injection-Site Reactions)

    Phase 2 and Phase 3

    Time frame: Through Day 169

  5. Severity of ISRs (Injection-Site Reactions)

    Phase 2 and Phase 3

    Time frame: Through Day 169

  6. Percentage of Participants With Hypersensitivity Reactions

    Phase 2 and Phase 3

    Time frame: Through Day 169

  7. Severity of Hypersensitivity Reactions Over Time

    Phase 2 and Phase 3

    Time frame: Through Day 169

  8. Percentage of Participants With Treatment-emergent SAEs (Serious Adverse Events)

    Phase 2 and Phase 3

    Time frame: Through Day 169

  9. Time-weighted Average Change From Baseline in Viral Load

    Phase 2 and Phase 3 Time-weighted average (TWA) daily change from baseline in viral load (log10 copies/mL) as measured by SARS-CoV-2 quantitative reverse transcription polymerase chain reaction (RT-qPCR) in nasopharyngeal (NP) swab samples.

    Time frame: Through Day 169

  10. Change From Baseline in Viral Load (Phase 1)

    Phase 1 Change from baseline in viral load (log10 copies/mL) as measured by SARS-CoV-2 quantitative reverse transcription polymerase chain reaction (RT-qPCR) in nasopharyngeal (NP) swab samples.

    Time frame: Through Day 7

  11. Change From Baseline in Viral Load

    Phase 2, and Phase 3 As measured by RT-qPCR in NP samples

    Time frame: Through Day 7

  12. Percentage of Participants With Viral Loads Below the Limit of Detection

    Phase 1, Phase 2, and Phase 3

    Time frame: Through Day 169

  13. Concentrations of REGN14256 in Serum Over Time (Phase 1)

    Phase 1

    Time frame: Through Day 169

  14. Concentrations of REGN14256 in Serum Over Time

    Phase 2 and Phase 3

    Time frame: Through Day 169

  15. Concentrations of Imdevimab in Serum Over Time (Phase 1)

    Phase 1

    Time frame: Through Day 169

  16. Concentrations of Imdevimab in Serum Over Time

    Phase 2 and Phase 3

    Time frame: Through Day 169

  17. Incidence and Titer of Anti-drug Antibodies (ADA) to REGN14256 Over Time

    Phase 1, Phase 2, and Phase 3

    Time frame: Through Day 169

  18. Incidence and Titer of ADA to Imdevimab Over Time

    Phase 1, Phase 2, and Phase 3

    Time frame: Through Day 169

07

Results

Posted Apr 26, 2024
Limitations and caveats
Due to the reduced activity of REGN14256+Imdevimab against the emerging Omicron variant and not due to any safety concerns, study enrollment was paused and later terminated in the phase 1 portion of the study. Phase 2 and phase 3 portions of the study were never opened. As a result, and due to small sample size, not all of the original objectives and endpoints were analyzed as planned

Participant flow

The study was initiated in November 2021, however, due to the reduced activity of REGN14256+imdevimab against the emerging Omicron variant and not due to any safety concerns, study enrollment was paused and later terminated. As a result, only 25 participants were randomized into the phase 1 portion of the study and the phase 2 and phase 3 portions of the study were never opened.

Participant flow — Overall Study
MilestonePlaceboImdevimab (600 mg SC)REGN14256 (600 mg SC)Casirivimab + Imdevimab (1200 mg SC)REGN14256 + Imdevimab (1200 mg SC)
Started45664
Completed34654
Not completed11010
Withdrew: Adverse event10000
Withdrew: Lost to follow-up01000
Withdrew: Subject decision00010

Outcome measures

PrimaryTreatment Emergent Adverse Events (TEAEs)

Phase 1

Time frame:
Through Day 29
Reported as:
Number · Events
Treatment Emergent Adverse Events (TEAEs)
EventsPlaceboImdevimab (600 mg SC)REGN14256 (600 mg SC)Casirivimab + Imdevimab (1200 mg SC)REGN14256 + Imdevimab (1200 mg SC)
Treatment Emergent Adverse Events (TEAEs)13112
PrimarySeverity of TEAEs

Severity was based on Grading. Grade 1 was less severe. Grade 5 was more severe. 1. \- Mild; Asymptomatic or mild symptoms; clinical or diagnostic observations only; intervention not indicated 2. \- Moderate; Minimal, local, or noninvasive intervention indicated; limiting age appropriate instrumental activities of daily living (ADL) 3. \- Severe; Severe or medically significant but not immediately life threatening; hospitalization or prolongation of hospitalization indicated; disabling; ADL2 limiting self-care 4. \- Life-threatening; Life threatening consequences; urgent intervention indicated 5. \- Death; Death related to adverse events

Time frame:
Through Day 29
Reported as:
Number · Participants
Severity of TEAEs
ParticipantsPlaceboImdevimab (600 mg SC)REGN14256 (600 mg SC)Casirivimab + Imdevimab (1200 mg SC)REGN14256 + Imdevimab (1200 mg SC)
With at least one Grade 1 TEAE02112
With at least one Grade 2 TEAE10000
With at least one Grade 3 TEAE01000
With at least one Grade 4 TEAE00000
With at least one Grade 5 TEAE00000
PrimaryPercentage of Participants With Injection-site Reactions (ISRs)

Phase 1 only

Time frame:
Through Day 169
Reported as:
Number · Percentage of Participants
Percentage of Participants With Injection-site Reactions (ISRs)
Percentage of ParticipantsPlaceboImdevimab (600 mg SC)REGN14256 (600 mg SC)Casirivimab + Imdevimab (1200 mg SC)REGN14256 + Imdevimab (1200 mg SC)
Percentage of Participants With Injection-site Reactions (ISRs)000025.0
PrimarySeverity of ISRs (Injection Site Reactions)

Severity was based on Grading. Grade 1 was less severe. Grade 5 was more severe. Grade 1 - Tenderness with or without associated symptoms (eg, warmth, erythema, itching) Grade 2 - Pain; lipodystrophy; edema; phlebitis Grade 3 - Ulceration or necrosis; severe tissue damage; operative intervention indicated Grade 4 - Life-threatening consequences; urgent intervention indicated Grade 5 - Death

Time frame:
Through Day 29
Reported as:
Number · Events
Severity of ISRs (Injection Site Reactions)
EventsPlaceboImdevimab (600 mg SC)REGN14256 (600 mg SC)Casirivimab + Imdevimab (1200 mg SC)REGN14256 + Imdevimab (1200 mg SC)
With at least one Grade 1 ISR00001
With at least one Grade 2 ISR00000
With at least one Grade 3 ISR00000
With at least one Grade 4 ISR00000
With at least one Grade 5 ISR00000
PrimaryPercentage of Participants With Hypersensitivity Reactions

Phase 1

Time frame:
Through Day 169
Reported as:
Number · Percentage of Participants
Percentage of Participants With Hypersensitivity Reactions
Percentage of ParticipantsPlaceboImdevimab (600 mg SC)REGN14256 (600 mg SC)Casirivimab + Imdevimab (1200 mg SC)REGN14256 + Imdevimab (1200 mg SC)
Percentage of Participants With Hypersensitivity Reactions00000
PrimarySeverity of Hypersensitivity Reactions Over Time

Grade 1 - Systemic intervention not indicated. Grade 2 - Oral intervention indicated Grade 3 - Bronchospasm; hospitalization indicated for clinical sequelae; intravenous intervention indicated Grade 4 - Life-threatening consequences; urgent intervention indicated Grade 5 - Death

Time frame:
Through Day 169
Reported as:
Number · Events
Severity of Hypersensitivity Reactions Over Time
EventsPlaceboImdevimab (600 mg SC)REGN14256 (600 mg SC)Casirivimab + Imdevimab (1200 mg SC)REGN14256 + Imdevimab (1200 mg SC)
With at least one Grade 100000
With at least one Grade 200000
With at least one Grade 300000
With at least one Grade 400000
With at least one Grade 500000
PrimaryTime-weighted Average (TWA) Daily Change From Baseline in Viral Load (log10 Copies/mL)

Phase 1 Measured by SARS-CoV-2 quantitative reverse transcription polymerase chain reaction (RT-qPCR) in nasopharyngeal (NP) swab samples

Time frame:
Day 1 to day 7
Reported as:
Mean · log10 copies/mL
Time-weighted Average (TWA) Daily Change From Baseline in Viral Load (log10 Copies/mL)
log10 copies/mLPlaceboImdevimab (600 mg SC)REGN14256 (600 mg SC)Casirivimab + Imdevimab (1200 mg SC)REGN14256 + Imdevimab (1200 mg SC)
Time-weighted Average (TWA) Daily Change From Baseline in Viral Load (log10 Copies/mL)-4.02 ± 1.461-2.28 ± 0.286-2.30 ± 0.964-2.72 ± 1.517-1.76 ± 0.003
SecondaryPercentage of Participants With Treatment-emergent Serious Adverse Events (SAEs)

Phase 1

Time frame:
Through Day 169
Reported as:
Number · Percentage
Percentage of Participants With Treatment-emergent Serious Adverse Events (SAEs)
PercentagePlaceboImdevimab (600 mg SC)REGN14256 (600 mg SC)Casirivimab + Imdevimab (1200 mg SC)REGN14256 + Imdevimab (1200 mg SC)
Percentage of Participants With Treatment-emergent Serious Adverse Events (SAEs)33.320.0000
SecondaryTEAEs (Treatment-Emergent Adverse Events)

Phase 2 and Phase 3

Time frame:
Through Day 29

No measurements were reported for this outcome.

SecondarySeverity of TEAEs (Treatment-Emergent Adverse Event)

Phase 2 and Phase 3

Time frame:
Through Day 29

No measurements were reported for this outcome.

SecondaryPercentage of Participants With ISRs (Injection-Site Reactions)

Phase 2 and Phase 3

Time frame:
Through Day 169

No measurements were reported for this outcome.

SecondarySeverity of ISRs (Injection-Site Reactions)

Phase 2 and Phase 3

Time frame:
Through Day 169

No measurements were reported for this outcome.

SecondaryPercentage of Participants With Hypersensitivity Reactions

Phase 2 and Phase 3

Time frame:
Through Day 169

No measurements were reported for this outcome.

SecondarySeverity of Hypersensitivity Reactions Over Time

Phase 2 and Phase 3

Time frame:
Through Day 169

No measurements were reported for this outcome.

SecondaryPercentage of Participants With Treatment-emergent SAEs (Serious Adverse Events)

Phase 2 and Phase 3

Time frame:
Through Day 169

No measurements were reported for this outcome.

SecondaryTime-weighted Average Change From Baseline in Viral Load

Phase 2 and Phase 3 Time-weighted average (TWA) daily change from baseline in viral load (log10 copies/mL) as measured by SARS-CoV-2 quantitative reverse transcription polymerase chain reaction (RT-qPCR) in nasopharyngeal (NP) swab samples.

Time frame:
Through Day 169

No measurements were reported for this outcome.

SecondaryChange From Baseline in Viral Load (Phase 1)

Phase 1 Change from baseline in viral load (log10 copies/mL) as measured by SARS-CoV-2 quantitative reverse transcription polymerase chain reaction (RT-qPCR) in nasopharyngeal (NP) swab samples.

Time frame:
Through Day 7
Reported as:
Mean · log10 copies/mL
Change From Baseline in Viral Load (Phase 1)
log10 copies/mLPlaceboImdevimab (600 mg SC)REGN14256 (600 mg SC)Casirivimab + Imdevimab (1200 mg SC)REGN14256 + Imdevimab (1200 mg SC)
Change from Baseline to Day 3-3.93 ± 2.691-2.14 ± 0.251-1.60 ± 1.598-2.27 ± 1.0970.23 ± NA
Change from Baseline to Day 5-5.25 ± 1.400-3.74 ± 1.585-3.28 ± 1.085-3.73 ± 2.677-1.88 ± NA
Change from Baseline to Day 7-5.76 ± 2.220-3.02 ± 1.115-4.01 ± 2.000-4.31 ± 2.121-5.37 ± 2.617
SecondaryChange From Baseline in Viral Load

Phase 2, and Phase 3 As measured by RT-qPCR in NP samples

Time frame:
Through Day 7

No measurements were reported for this outcome.

SecondaryPercentage of Participants With Viral Loads Below the Limit of Detection

Phase 1, Phase 2, and Phase 3

Time frame:
Through Day 169

No measurements were reported for this outcome.

SecondaryConcentrations of REGN14256 in Serum Over Time (Phase 1)

Phase 1

Time frame:
Through Day 169
Reported as:
Mean · mg/L
Concentrations of REGN14256 in Serum Over Time (Phase 1)
mg/LREGN14256 600 mg SCREGN14256+Imdevimab (1200 mg SC)
Pre-dose0 ± 00 ± 0
Post-dose3.45 ± 4.369.66 ± 10.6
Day 121.5 ± 16.652.4 ± 43.3
Day 237.5 ± 25.458.5 ± 38.3
Day 653.2 ± 29.963.6 ± 26.2
Day 2830.7 ± 15.739.9 ± 14.6
Day 5913.5 ± 7.5719.6 ± 5.78
Day 897.30 ± 4.469.03 ± 3.43
Day 1193.44 ± 2.424.23 ± 1.73
SecondaryConcentrations of REGN14256 in Serum Over Time

Phase 2 and Phase 3

Time frame:
Through Day 169

No measurements were reported for this outcome.

SecondaryConcentrations of Imdevimab in Serum Over Time (Phase 1)

Phase 1

Time frame:
Through Day 169
Reported as:
Mean · mg/L
Concentrations of Imdevimab in Serum Over Time (Phase 1)
mg/LImdevimab 600 mg SCCasirivimab+Imdevimab (1200 mg SC)REGN14256+Imdevimab (1200 mg SC)
Pre-dose2.46 ± 3.590.398 ± 0.9760.360 ± 0.720
Post-dose3.43 ± 3.133.06 ± 2.369.03 ± 6.47
Day 119.7 ± 9.7431.2 ± 10.527.9 ± 21.0
Day 228.4 ± 6.0840.7 ± 11.831.9 ± 19.2
Day 642.7 ± 16.852.2 ± 16.338.8 ± 7.59
Day 2818.9 ± 9.9427.9 ± 8.3420.8 ± 12.2
Day 597.66 ± 3.6810.3 ± 4.407.18 ± 3.75
Day 893.26 ± 1.804.37 ± 2.123.73 ± 2.46
Day 1191.72 ± 1.062.60 ± 1.522.68 ± 0.910
SecondaryConcentrations of Imdevimab in Serum Over Time

Phase 2 and Phase 3

Time frame:
Through Day 169

No measurements were reported for this outcome.

SecondaryIncidence and Titer of Anti-drug Antibodies (ADA) to REGN14256 Over Time

Phase 1, Phase 2, and Phase 3

Time frame:
Through Day 169

No measurements were reported for this outcome.

SecondaryIncidence and Titer of ADA to Imdevimab Over Time

Phase 1, Phase 2, and Phase 3

Time frame:
Through Day 169

No measurements were reported for this outcome.

Adverse events

Collected over From first dose to end of study (Up to 169 days). Non-serious events are listed at a 5% frequency threshold.

Adverse event summary by group
GroupDeathsSeriousOther
Placebo0/3 (0%)1/3 (33.3%)1/3 (33.3%)
Imdevimab 600 mg SC0/5 (0%)1/5 (20%)2/5 (40%)
REGN14256 600 mg SC0/6 (0%)0/6 (0%)1/6 (16.7%)
REGN14256+Imdevimab 1200 mg SC0/4 (0%)0/4 (0%)2/4 (50%)
Casirivimab+Imdevimab 1200 mg SC0/6 (0%)0/6 (0%)1/6 (16.7%)
Most frequent serious events
Most frequent serious events
EventPlaceboImdevimab 600 mg SCREGN14256 600 mg SCREGN14256+Imdevimab 1200 mg SCCasirivimab+Imdevimab 1200 mg SC
Arthritis bacterialInfections and infestations1/30/50/60/40/6
HypoxiaRespiratory, thoracic and mediastinal disorders0/31/50/60/40/6
Most frequent other events
Showing 10 of 13
Most frequent other events
EventPlaceboImdevimab 600 mg SCREGN14256 600 mg SCREGN14256+Imdevimab 1200 mg SCCasirivimab+Imdevimab 1200 mg SC
HeadacheNervous system disorders0/32/50/60/41/6
Wound infectionInfections and infestations1/30/50/60/40/6
ConstipationGastrointestinal disorders1/30/50/60/40/6
Skin lacerationInjury, poisoning and procedural complications1/30/50/60/40/6
Blood creatine phosphokinase increasedInvestigations1/30/50/60/40/6
Injection site reactionGeneral disorders0/30/50/61/40/6
PyrexiaGeneral disorders0/30/50/61/40/6
Back painMusculoskeletal and connective tissue disorders0/30/50/61/40/6
TonsillitisInfections and infestations0/31/50/60/40/6
RashSkin and subcutaneous tissue disorders0/31/50/60/40/6

Baseline characteristics

Age, Continuous
Age, Continuous(Years)PlaceboImdevimab (600 mg SC)REGN14256 (600 mg SC)Casirivimab + Imdevimab (1200 mg SC)REGN14256 + Imdevimab (1200 mg SC)Total
Mean25.8 ± 1.5050.4 ± 14.0538.2 ± 19.8130.3 ± 7.8742.0 ± 9.9037.4 ± 14.63
Sex: Female, Male
Sex: Female, Male(Participants)PlaceboImdevimab (600 mg SC)REGN14256 (600 mg SC)Casirivimab + Imdevimab (1200 mg SC)REGN14256 + Imdevimab (1200 mg SC)Total
Female2223211
Male2343214
Ethnicity (NIH/OMB)
Ethnicity (NIH/OMB)(Participants)PlaceboImdevimab (600 mg SC)REGN14256 (600 mg SC)Casirivimab + Imdevimab (1200 mg SC)REGN14256 + Imdevimab (1200 mg SC)Total
Hispanic or Latino3436319
Not Hispanic or Latino113016
Unknown or Not Reported000000
Race (NIH/OMB)
Race (NIH/OMB)(Participants)PlaceboImdevimab (600 mg SC)REGN14256 (600 mg SC)Casirivimab + Imdevimab (1200 mg SC)REGN14256 + Imdevimab (1200 mg SC)Total
American Indian or Alaska Native000000
Asian000000
Native Hawaiian or Other Pacific Islander000000
Black or African American101103
White3555422
More than one race000000
Unknown or Not Reported000000
08

Study locations

28 sites
  • Regeneron Research Site
    La Mesa, California 91941, United States
  • Ark Clinical Research
    Long Beach, California 90806, United States
  • PNS Clinical Research, LLC
    Mission Viejo, California 92691, United States
  • Regeneron Research Site
    Ft. Pierce, Florida 34982, United States
  • AGA Clinical Trials
    Hialeah, Florida 33012, United States
  • Regeneron Research Site
    Loxahatchee Groves, Florida 33470, United States
  • Project 4 Research, Inc.
    Miami, Florida 33125, United States
  • Universal Medical and Research Center, LLC
    Miami, Florida 33126, United States
  • Global Medical Trials
    Miami, Florida 33174, United States
  • Bio-Medical Research LLC
    Miami, Florida 33184, United States
  • Charisma Research and Medical Center
    Miami Lakes, Florida 33014, United States
  • Triple O Research Institute, P.A.
    West Palm Beach, Florida 33407, United States
  • Regeneron Research Site
    Winter Park, Florida 32789, United States
  • IACT Health
    Columbus, Georgia 31904, United States
  • Chicago Clinical Research Institute
    Chicago, Illinois 60607, United States
  • Regeneron Research Site
    Ames, Iowa 50010, United States
  • Regeneron Research Site
    Marrero, Louisiana 70072, United States
  • Olive Branch Family Medical Center
    Olive Branch, Mississippi 38654, United States
  • Forte Family Practice
    Las Vegas, Nevada 89103, United States
  • New York Health and Hospitals / Lincoln
    The Bronx, New York 10451, United States
  • NYC H+H / Jacobi Medical Center
    The Bronx, New York 10461, United States
  • Regeneron Research Site
    Wilmington, North Carolina 28401, United States
  • Regeneron Research Site
    Dayton, Ohio 45409, United States
  • Carolina Medical Research
    Clinton, South Carolina 29325, United States
  • PharmaTex Research, LLC
    Amarillo, Texas 79109, United States
  • Advanced Diagnostics Clinic, River Oaks Hospital and Clinics
    Houston, Texas 77027, United States
  • Regeneron Research Site
    Houston, Texas 77030, United States
  • Regeneron Research Site
    Houston, Texas 77093, United States
09

References and documents

Study documents

  • Study protocol · Oct 6, 2021
  • Statistical analysis plan · Jul 6, 2022

Documents are hosted by the registry — open the source record to download them.

Individual participant data

Plan to share: Yes — All Individual Patient Data (IPD) that underlie publicly available results will be considered for sharing

Supporting information: Study protocol, Sap, Icf, Csr, Analytic code

10

Updates

Tracking since Sep 25, 2026
No changes since tracking began. The registry record was last updated on Oct 28, 2025, before this site started recording changes on Sep 25, 2026. Its history is on ClinicalTrials.gov ↗
11

Registry details

Key details

Study ID
NCT05081388
Lead sponsor
Regeneron Pharmaceuticals
Responsible party
Sponsor
First posted
Oct 18, 2021
Start date
Nov 8, 2021
Primary completion
Jun 30, 2022
Completion
Jun 30, 2022
Results posted
Apr 26, 2024
Last update
Oct 28, 2025

Study contacts

Clinical Trial Management
study director · Regeneron Pharmaceuticals

Oversight

Data monitoring committee
Yes
FDA-regulated drug
Yes
FDA-regulated device
No
View the source record on ClinicalTrials.gov ↗

Not currently enrolling

This study is terminated, as verified in Oct 2025. You cannot join it, but the record below documents what was studied.

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Discussion

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