Safety, Tolerability, and Efficacy of Anti-Spike (S) SARS-CoV-2 Monoclonal Antibodies for Hospitalized Adult Patients With COVID-19

Phase 1

Completed

Conditions: COVID-19

Interventions: Drug: REGN10933+REGN10987 combination therapy
Drug: Placebo

Registration Number: NCT04426695

Lead Sponsor: Regeneron Pharmaceuticals

Brief Summary: The primary objectives are:

Pooled Phase 3 (Cohort 1) and Phase 2 (Cohort 1A)

* To evaluate the virologic efficacy of REGN10933+REGN10987 compared to placebo in reducing viral load of SARS-CoV-2

* To evaluate the clinical efficacy of REGN10933+REGN10987 compared to placebo, as measured by death or mechanical ventilation

Phase 1/2 (Cohort 1)

* To exclude futility of REGN10933+REGN10987 compared to placebo, as measured by death or mechanical ventilation

* To evaluate the safety and tolerability of REGN10933+REGN10987 compared to placebo

Detailed Description: Not available

Recruitment & Eligibility

Status: COMPLETED

Sex: All

Target Recruitment: 2252

Inclusion Criteria

Has SARS-CoV-2-positive antigen or molecular diagnostic test (by validated SARS-CoV-2 antigen, RT-PCR, or other molecular diagnostic assay, using an appropriate sample such as NP, nasal, oropharyngeal [OP], or saliva) ≤72 hours prior to randomization and no alternative explanation for current clinical condition. A historical record of positive result from test conducted ≤72 hours prior to randomization is acceptable.
Has symptoms consistent with COVID-19, as determined by investigator, with onset ≤10 days before randomization
Hospitalized for ≤72 hours with at least 1 of the following at randomization; patients meeting more than one criterion will be categorized in the most severely affected category:
1. Cohort 1A: With COVID-19 symptoms but not requiring supplemental oxygen
2. Cohort 1: Maintains O2 saturation >93% on low-flow oxygen as defined in the protocol
3. Cohort 2: High-intensity oxygen therapy without mechanical ventilation as defined in the protocol
4. Cohort 3: On mechanical ventilation

Key

Exclusion Criteria

Phase 1 Only: Patients maintaining O2 saturation >94% on room air
In the opinion of the investigator, unlikely to survive for >48 hours from screening
Receiving extracorporeal membrane oxygenation (ECMO)
Has new-onset stroke or seizure disorder during hospitalization
Initiated on renal replacement therapy due to COVID-19

NOTE: Other protocol defined inclusion / exclusion criteria apply

Study & Design

Study Type: INTERVENTIONAL

Study Design: PARALLEL

Arm && Interventions

Group	Intervention	Description
On Low-Flow Oxygen	REGN10933+REGN10987 combination therapy	Cohort 1 (C1): O2 saturation \>93% on low-flow oxygen via nasal cannula, simple face mask, or other similar device
On Low-Flow Oxygen	Placebo	Cohort 1 (C1): O2 saturation \>93% on low-flow oxygen via nasal cannula, simple face mask, or other similar device
With COVID-19 symptoms but not requiring supplemental O2	REGN10933+REGN10987 combination therapy	Cohort 1A (C1A): With COVID-19 symptoms but not requiring supplemental oxygen
With COVID-19 symptoms but not requiring supplemental O2	Placebo	Cohort 1A (C1A): With COVID-19 symptoms but not requiring supplemental oxygen
High O2 No Mechanical Ventilation	Placebo	Cohort 2 (C2): On high-intensity oxygen (O2) therapy but not on mechanical ventilation
On Mechanical Ventilation	Placebo	Cohort 3 (C3): On mechanical ventilation
High O2 No Mechanical Ventilation	REGN10933+REGN10987 combination therapy	Cohort 2 (C2): On high-intensity oxygen (O2) therapy but not on mechanical ventilation
On Mechanical Ventilation	REGN10933+REGN10987 combination therapy	Cohort 3 (C3): On mechanical ventilation

Primary Outcome Measures

Name	Time	Method
Pooled Analysis (Phase 3 [Cohort 1] and Phase 2 [Cohort 1A]): Percentage of Participants Who Died or Went on Mechanical Ventilation From Day 1 Through Day 29 Based on Seronegative mFAS	Day 1 to Day 29	Percentage of participants who died or went on mechanical ventilation from Day 1 through Day 29 based on seronegative mFAS were reported.
Pooled Analysis (Phase 1 [Cohort 1] and Phase 2 [Cohort 1]): Number of Participants With Grade >=2 Hypersensitivity Reactions Up to Day 29	Up to Day 29	Hypersensitivity reactions are defined as any relevant adverse event that occurs during the infusion or up to study day 29. The severity of adverse events (including test findings classified as adverse events) were graded according to NCI-CTCAE.
Pooled Analysis (Phase 3 [Cohort 1] and Phase 2 [Cohort 1A]): Percentage of Participants Who Died or Went on Mechanical Ventilation From Day 6 Through Day 29 Based on Seronegative mFAS	Day 6 to Day 29	Percentage of participants who died or went on mechanical ventilation from Day 6 through Day 29 based on seronegative mFAS were reported.
Pooled Analysis (Phase 3 [Cohort 1] and Phase 2 [Cohort 1A]): Percentage of Participants Who Died or Went on Mechanical Ventilation From Day 1 Through Day 29 Based on High Viral Load mFAS	Day 1 to Day 29	Percentage of participants who died or went on mechanical ventilation from Day 1 through Day 29 based on high viral load mFAS were reported.
Pooled Analysis (Phase 1 [Cohort 1] and Phase 2 [Cohort 1]): Number of Participants With Grade >=2 Infusion Related Reactions up to Day 4	Up to Day 4	Infusion-related reactions are defined as any relevant adverse event that occurs during the infusion or up to day 4. The severity of adverse events (including test findings classified as adverse events) were graded according to the National Cancer Institute Common Terminology Criteria for Adverse Events (NCI-CTCAE).
Pooled Analysis (Phase 3 [Cohort 1] and Phase 2 [Cohort 1A]): Percentage of Participants Who Died or Went on Mechanical Ventilation From Day 1 Through Day 29 Based on Overall mFAS	Day 1 to Day 29	Percentage of participants who died or went on mechanical ventilation from Day 1 through Day 29 based on overall mFAS were reported.
Pooled Analysis (Phase 1 [Cohort 1] and Phase 2 [Cohort 1]): Cumulative Incidence of Death or Mechanical Ventilation Based on Seronegative mFAS	Up to Day 29	Cumulative incidence percentage was estimated using Kaplan-Meier method.
Pooled Analysis (Phase 1 [Cohort 1] and Phase 2 [Cohort 1]): Cumulative Incidence of Death or Mechanical Ventilation Based on High Viral Load mFAS	Up to Day 29	Cumulative incidence percentage was estimated using Kaplan-Meier method.
Pooled Analysis (Phase 3 [Cohort 1] and Phase 2 [Cohort 1A]): Time-weighted Average (TWA) Change in Viral Load in Nasopharyngeal (NP) Samples Based on Seronegative mFAS	Day 1 to Day 7	Time-weighted average daily change from Day 1 to Day 7 in viral load (log10 copies/mL), as measured by reverse transcription quantitative polymerase chain reaction (RT-qPCR) in nasopharyngeal (NP) swab samples.
Pooled Analysis (Phase 3 [Cohort 1] and Phase 2 [Cohort 1A]): Percentage of Participants Who Died or Went on Mechanical Ventilation From Day 6 Through Day 29 Based on Overall mFAS	Day 6 to Day 29	Percentage of participants who died or went on mechanical ventilation from Day 6 through Day 29 based on overall FAS were reported.
Pooled Analysis (Phase 3 [Cohort 1] and Phase 2 [Cohort 1A]): Percentage of Participants Who Died or Went on Mechanical Ventilation From Day 6 Through Day 29 Based on High Viral Load mFAS	Day 6 to Day 29	Percentage of participants who died or went on mechanical ventilation from Day 6 through Day 29 based on high viral load mFAS were reported.
Pooled Analysis (Phase 1 [Cohort 1] and Phase 2 [Cohort 1]): Number of Participants With Treatment-Emergent Serious Adverse Events	Up to Day 169	Treatment-emergent adverse events are defined as those that are not present at baseline or represent the exacerbation of a pre-existing condition during the observation period.

Secondary Outcome Measures

Name	Time	Method
Pooled Analysis Phase 3 (Cohort 1) and Phase 2 (Cohort 1A): Percentage of Participants Who Were Discharged by Day 29 Based on Seronegative mFAS	by Day 29	Percentage of participants who were discharged by Day 29 based on seronegative mFAS in Phase 3 (Cohort 1) and Phase 2 (Cohort 1A) were reported.
Pooled Analysis Phase 3 (Cohort 1) and Phase 2 (Cohort 1A): Percentage of Participants Who Died or Were Readmitted to Hospital by Day 29 Based on Seronegative mFAS	by Day 29	Percentage of participants who died or were readmitted to hospital at Day 29 based on seronegative mFAS in phase 3 (Cohort 1) and phase 2 (Cohort 1A) were reported. Readmission to hospital was based on investigator report.
Pooled Analysis Phase 3 (Cohort 1) and Phase 2 (Cohort 1A): Cumulative Incidence of Mechanical Ventilation by Day 29 Based on High Viral Load mFAS	by Day 29	Number of participants with cumulative incidence of mechanical ventilation by Day 29 based on High Viral Load mFAS in Phase 3 (Cohort 1) and Phase 2 (Cohort 1A) were reported. Cumulative incidence percentage was estimated using Kaplan-Meier method.
Pooled Analysis Phase 3 (Cohort 1) and Phase 2 (Cohort 1A): Percentage of Participants Who Went on Mechanical Ventilation by Day 29 Based on High Viral Load mFAS	by Day 29	Percentage of participants who went on mechanical ventilation by Day 29 based on High Viral Load mFAS in pooled analysis phase 3 (Cohort 1) and phase 2 (Cohort 1A) was reported.
Pooled Analysis Phase 3 (Cohort 1) and Phase 2 (Cohort 1A): Percentage of Participants Who Went on Mechanical Ventilation by Day 29 Based on Seronegative mFAS	by Day 29	Percentage of participants who went on mechanical ventilation at Day 29 based on Seronegative mFAS in pooled analysis phase 3 (Cohort 1) and phase 2 (Cohort 1A) was reported.
Pooled Analysis Phase 3 (Cohort 1) and Phase 2 (Cohort 1A): Percentage of Participants Who Died From Day 6 Through Day 29 Based on High Viral Load mFAS	Day 6 to Day 29	Percentage of participants who died from Day 6 through Day 29 based on high viral load mFAS were reported.
Pooled Analysis Phase 3 (Cohort 1) and Phase 2 (Cohort 1A): Percentage of Participants Who Died From Day 1 Through Day 29 Based on High Viral Load mFAS	Day 1 to Day 29	Percentage of participants who died from Day 1 through Day 29 based on High Viral Load mFAS in pooled analysis phase 3 (Cohort 1) and phase 2 (Cohort 1A) were reported.
Pooled Analysis Phase 3 (Cohort 1) and Phase 2 (Cohort 1A): Cumulative Incidence of Mechanical Ventilation by Day 29 Based on Seronegative mFAS	by Day 29	Percentage of participants with cumulative incidence of mechanical ventilation by Day 29 based on seronegative mFAS in phase 3 (Cohort 1) and phase 2 (Cohort 1A) were reported. Cumulative incidence percentage was estimated using Kaplan-Meier method.
Pooled Analysis Phase 3 (Cohort 1) and Phase 2 (Cohort 1A): Percentage of Participants Who Died From Day 6 Through Day 29 Based on Seronegative mFAS	Day 6 to Day 29	Percentage of participants who died from Day 6 through Day 29 Based on seronegative mFAS in pooled analysis phase 3 (cohort 1) and phase 2 (cohort 1A) were reported.
Pooled Analysis Phase 3 (Cohort 1) and Phase 2 (Cohort 1A): Percentage of Participants Who Died From Day 1 Through Day 29 Based on Seronegative mFAS	Day 1 to Day 29	Percentage of participants who died from Day 1 through Day 29 based on seronegative mFAS in pooled analysis phase 3 (Cohort 1) and phase 2 (Cohort 1A) were reported.
Pooled Analysis Phase 3 (Cohort 1) and Phase 2 (Cohort 1A): Percentage of Participants Who Were Discharged by Day 29 Based on High Viral Load mFAS	by Day 29	Percentage of participants who were discharged by Day 29 based on High Viral Load mFAS in Phase 3 (Cohort 1) and Phase 2 (Cohort 1A) were reported.
Phase 3 (Cohort 1) and Phase 2 (Cohort 1A): Percentage of Participants Who Died From Day 6 Through Day 29 Based on Seronegative mFAS	Day 6 to Day 29	Percentage of participants who died from Day 6 through Day 29 in phase 3 (cohort 1) and phase 2 (cohort 1A) were reported.
Phase 3 (Cohort 1) and Phase 2 (Cohort 1A): Percentage of Participants Who Died From Day 1 Through Day 29 Based on Seronegative mFAS	Day 1 to Day 29	Percentage of participants who died from Day 1 through Day 29 in phase 3 (Cohort 1) and phase 2 (Cohort 1A) were reported.
Phase 3 (Cohort 1) and Phase 2 (Cohort 1A): Percentage of Participants Who Were Discharged by Day 29 Based on Seronegative mFAS	by Day 29	Percentage of participants who were discharged in Phase 3 (Cohort 1) and Phase 2 (Cohort 1A) by Day 29 were reported.
Phase 3 (Cohort 1) and Phase 2 (Cohort 1A): Percentage of Participants Who Died or Were Readmitted to Hospital by Day 29 Based on Seronegative mFAS	Up to Day 29	Percentage of participants who died or were readmitted to hospital in phase 3 (Cohort 1) and phase 2 (Cohort 1A) by Day 29 were reported. Readmission to hospital was based on investigator report.
Phase 3 (Cohort 1) and Phase 2 (Cohort 1A): Cumulative Incidence of Death up to Day 29 Based on Seronegative mFAS	Up to Day 29	Percentage of participants with cumulative incidence of death in Phase 3 (Cohort 1) and Phase 2 (Cohort 1A) up to Day 29 from randomization were reported. Cumulative incidence percentage was estimated using Kaplan-Meier method.
Phase 3 (Cohort 1) and Phase 2 (Cohort 1A): Cumulative Incidence of Mechanical Ventilation by Day 29 Based on Seronegative mFAS	by Day 29	Percentage of participants with cumulative incidence of mechanical ventilation in Phase 3 (Cohort 1) and Phase 2 (Cohort 1A) by Day 29 were reported. Cumulative incidence percentage was estimated using Kaplan-Meier method.
Phase 3 (Cohort 1) and Phase 2 (Cohort 1A): Cumulative Incidence of Death or Mechanical Ventilation by Day 29 Based on Seronegative mFAS	by Day 29	Percentage of participants with cumulative incidence of death or mechanical ventilation in Phase 3 (Cohort 1) and Phase 2 (Cohort 1A) by Day 29 were reported. Cumulative incidence percentage was estimated using Kaplan-Meier method.
Pooled Analysis Phase 3 (Cohort 1) and Phase 2 (Cohort 1A): Percentage of Participants Who Died or Were Readmitted to Hospital Over Time Based on High Viral Load mFAS	Up to Day 29	Percentage of participants who died or were readmitted to hospital over time based on High Viral Load mFAS in Phase 3 (Cohort 1) and Phase 2 (Cohort 1A)were reported. Readmission to hospital was based on investigator report.
Pooled Analysis Phase 3 (Cohort 1) and Phase 2 (Cohort 1A): Cumulative Incidence of Death (ie, Overall Survival) by Day 29 Based on High Viral Load mFAS	by Day 29	Overall Survival was defined as time interval from randomization to death. Percentage of participants with cumulative incidence of death (ie, overall survival) at Day 29 from randomization based on High Viral Load mFAS in Phase 3 (Cohort 1) and Phase 2 (Cohort 1A) were reported. Cumulative incidence percentage was estimated using Kaplan-Meier method.
Pooled Analysis Phase 3 (Cohort 1) and Phase 2 (Cohort 1A): Cumulative Incidence of Death (ie, Overall Survival) by Day 29 Based on Seronegative mFAS	by Day 29	Overall Survival was defined as time interval from randomization to death. Percentage of participants with cumulative incidence of death (ie, overall survival) at Day 29 from randomization based on seronegative mFAS in phase 3 (Cohort 1) and phase 2 (Cohort 1A)were reported. Cumulative incidence percentage was estimated using Kaplan-Meier method.
Pooled Analysis (Phases 1/2/3 [Cohort 1] and Phase 2 [Cohorts 1A/2/3]): Number of Participants With Grade >=2 Infusion Related Reactions up to Day 4	Up to Day 4
Pooled Analysis (Phases 1/2/3 [Cohort 1] and Phase 2 [Cohorts 1A/2/3]): Number of Participants With Grade >=2 Hypersensitivity Reactions Up to Day 29	Up to Day 29
Phase 3 (Cohort 1) and Phase 2 (Cohort 1A): Percentage of Participants Who Went on Mechanical Ventilation by Day 29 Based on Seronegative mFAS	by Day 29	Percentage of participants who went on mechanical ventilation in phase 3 (Cohort 1) and phase 2 (Cohort 1A) was reported.
Pooled Analysis Phase 3 (Cohort 1) and Phase 2 (Cohort 1A): Cumulative Incidence of Death or Mechanical Ventilation by Day 29 Based on High Viral Load mFAS	by Day 29	Percentage of participants with cumulative incidence of death or mechanical ventilation by Day 29 based on High Viral Load mFAS in Phase 3 (Cohort 1) and Phase 2 (Cohort 1A) were reported. Cumulative incidence percentage was estimated using Kaplan-Meier method.
Pooled Analysis (Phases 1/2/3 [Cohort 1] and Phase 2 [Cohorts 1A/2/3]): Number of Participants With Treatment-Emergent Serious Adverse Events	Up to Day 169
Pooled Analysis Phase 3 (Cohort 1) and Phase 2 (Cohort 1A): Cumulative Incidence of Death or Mechanical Ventilation by Day 29 Based on Seronegative mFAS	by Day 29	Percentage of participants with cumulative incidence of death or mechanical ventilation by Day 29 based on seronegative mFAS in phase 3 (Cohort 1) and phase 2 (Cohort 1A) were reported. Cumulative incidence percentage was estimated using Kaplan-Meier method.
Pooled Analysis Phase 3 (Cohort 1) and Phase 2 (Cohort 1A): Time to Discharge From Hospital Based on High Viral Load mFAS	Up to Day 56	Time to discharge from hospital based on High Viral Load mFAS in Phase 3 (Cohort 1) and Phase 2 (Cohort 1A) was reported.
Pooled Analysis Phase 3 (Cohort 1) and Phase 2 (Cohort 1A): Time to Discharge From Hospital Based on Seronegative mFAS	Up to Day 56	Time to discharge from hospital based on Seronegative mFAS in Phase 3 (Cohort 1) and Phase 2 (Cohort 1A) was reported.
Phase 3 (Cohort 1) and Phase 2 (Cohort 1A): Time to Discharge From Hospital Based on Seronegative mFAS	Up to Day 56	Time to discharge from hospital up to Day 56 was reported.
Phase 3 [Cohort 1] and Phase 2 [Cohort 1A]: TWA Change From Baseline Viral Load (Seronegative mFAS) in NP Samples up to Day 11 Based on Seronegative mFAS	Day 1 to Day 11	TWA change from baseline in viral load up to Day 11 was calculated for each participant using the trapezoidal rule as the area under the curve for change from baseline at each time point divided by the time interval for the observation period. TWA change from baseline viral load in NP samples through Day 11, was measured by RT-qPCR in NP swab samples was reported. Baseline was defined as the last non-missing value measured prior to dosing. Negative changes indicate improvement in viral load.
Phase 3 [Cohort 1] and Phase 2 [Cohort 1A]: TWA Change From Baseline Viral Load (Seronegative mFAS) in NP Samples up to Day 29	Day 1 to Day 29	TWA change from baseline in viral load up to Day 29 was calculated for each participant using the trapezoidal rule as the area under the curve for change from baseline at each time point divided by the time interval for the observation period. TWA change from baseline viral load in NP samples through Day 29, was measured by quantitative RT-qPCR in NP swab samples was reported. Baseline was defined as the last non-missing value measured prior to dosing. Negative changes indicate improvement in viral load.
Phase 3 [Cohort 1] and Phase 2 [Cohort 1A]: Change From Baseline in Viral Load (Seronegative mFAS) as Measured by RT-qPCR in NP Swabs Over Time	Days 3, 5, 7, 9, 11, 13, 15, 22 and 29	Change from baseline in viral load as measured by RT-qPCR in NP swabs over time was reported. Baseline was defined as the last non-missing value measured prior to dosing. Negative changes indicates improvement in viral load.
Phase 3 [Cohort 1] and Phase 2 [Cohort 1A]: Percent Change From Baseline in Viral Load (Seronegative mFAS) as Measured by RT-qPCR in NP Swabs Over Time	Days 3, 5, 7, 9, 11, 13, 15, 22 and 29	Percent change from baseline in viral load as measured by RT-qPCR in NP swabs over time was reported. Baseline was defined as the last non-missing value measured prior to dosing. Negative changes indicates improvement in viral load.
Phase 3 (Cohort 1) and Phase 2 (Cohort 1A): Percentage of Participants Who Went on Mechanical Ventilation by Day 29 Based on High Viral Load mFAS	by Day 29	Percentage of participants who went on mechanical ventilation in phase 3 (Cohort 1) and phase 2 (Cohort 1A) was reported.
Phase 3 (Cohort 1) and Phase 2 (Cohort 1A): Percentage of Participants Who Died From Day 6 to Day 29 Based on High Viral Load mFAS	Day 6 to Day 29	Percentage of participants who died in phase 3 (Cohort 1) and phase 2 (Cohort 1A) was reported.
Phase 3 (Cohort 1) and Phase 2 (Cohort 1A): Percentage of Participants Who Died From Day 1 to Day 29 Based on High Viral Load mFAS	Day 1 to Day 29	Percentage of participants who died in phase 3 (Cohort 1) and phase 2 (Cohort 1A) was reported.
Phase 3 (Cohort 1) and Phase 2 (Cohort 1A): Percentage of Participants Who Were Discharged by Day 29 Based on High Viral Load mFAS	by Day 29	Percentage of participants who were discharged in phase 3 (Cohort 1) and phase 2 (Cohort 1A) was reported.
Phase 3 (Cohort 1) and Phase 2 (Cohort 1A): Percentage of Participants Who Died or Were Readmitted to Hospital Over Time Based on High Viral Load mFAS	Up to Day 29	Percentage of participants who died or were readmitted to hospital in phase 3 (Cohort 1) and phase 2 (Cohort 1A) over time were reported. Readmission to hospital was based on investigator report.
Phase 3 (Cohort 1) and Phase 2 (Cohort 1A): Cumulative Incidence of Death Over Time Based on High Viral Load mFAS	Up to Day 29	Cumulative Incidence of Death Over Time in phase 3 (Cohort 1) and phase 2 (Cohort 1A) were reported. Cumulative incidence percentage was estimated using Kaplan-Meier method.
Phase 3 (Cohort 1) and Phase 2 (Cohort 1A): Cumulative Incidence of Mechanical Ventilation Over Time Based on High Viral Load mFAS	Up to Day 29	Cumulative Incidence of Mechanical Ventilation Over Time in phase 3 (Cohort 1) and phase 2 (Cohort 1A) were reported. Cumulative incidence percentage was estimated using Kaplan-Meier method.
Phase 3 (Cohort 1) and Phase 2 (Cohort 1A): Cumulative Incidence of Death or Mechanical Ventilation Over Time Based on High Viral Load mFAS	Up to Day 29	Cumulative Incidence of Death or Mechanical Ventilation Over Time in phase 3 (Cohort 1) and phase 2 (Cohort 1A) were reported. Cumulative incidence percentage was estimated using Kaplan-Meier method.
Phase 3 (Cohort 1) and Phase 2 (Cohort 1A): Time to Discharge Based on High Viral Load mFAS	Up to Day 56	Time to Discharge in phase 3 (Cohort 1) and phase 2 (Cohort 1A) were reported.
Phase 1 [Cohort 1] and Phase 2 [Cohort 1]): Change From Baseline as Measured by RT-qPCR in NP Swabs Over Time Based on Seronegative mFAS	Days 3, 5, 7, 9, 11, 13, 15, 22 and 29	Change from baseline in viral load as measured by RT-qPCR in NP swabs over time was reported. Baseline was defined as the last non-missing value measured prior to dosing. Negative changes indicates improvement in viral load.
Phase 1 [Cohort 1] and Phase 2 [Cohort 1]: Percentage of Participants Who Died or Went On Mechanical Ventilation by Day 29 Based on High Viral Load mFAS	Through Day 29
Immunogenicity as Measured by Neutralizing Antibody Status (NAb) to REGN10933	Through Day 57
Immunogenicity as Measured by Neutralizing Antibody Status (NAb) to REGN10987	Through Day 57
Phase 1 [Cohort 1] and Phase 2 [Cohort 1]): Time-weighted Average (TWA) Change in Viral Load in Nasopharyngeal (NP) Samples Over Time Based on Seronegative mFAS	Up to Day 29	Time-weighted average daily change over time up to Day 29 in viral load (log10 copies/mL), as measured by reverse transcription quantitative polymerase chain reaction (RT-qPCR) in nasopharyngeal (NP) swab samples.
Phase 1 [Cohort 1] and Phase 2 [Cohort 1]: Percentage of Participants Who Died or Went On Mechanical Ventilation by Day 29 Based on Seronegative mFAS	Through Day 29
Phase 1 [Cohort 1]: Area Under the Concentration-Time Curve From Time 0 to 28 Days Post-dose (AUC0-28)	Up to Day 28
Concentration at Day 28 (C28)	Day 28
Immunogenicity as Measured by Anti-drug Antibodies (ADAs) to REGN10933	Through Day 169
Concentration at the End of Infusion (Ceoi)	Day 1
Immunogenicity as Measured by Anti-drug Antibodies (ADAs) to REGN10987	Through Day 169