Primary Outcomes
Measure: Time to Recovery, Defined as the Time to a Score of 1 or 2 on the 7-Category Ordinal Scale (Whichever Occurs First) Time: Day 28
Secondary Outcomes
Measure: Time to Improvement of at Least 2 Categories Relative to Baseline on a 7-Category Ordinal Scale of Clinical Status Time: From Baseline up to 28 days
Measure: Time to Hospital Discharge or "Ready for Discharge" Time: Up to 28 days
Measure: Duration of Supplemental Oxygen Time: Up to 28 days
Measure: Percentage of Participants Alive and Free of Respiratory Failure Time: Day 28
Measure: Clinical Status, Assessed Using a 7-Category Ordinal Scale Time: Days 14 and 28
Measure: Incidence of Invasive Mechanical Ventilation or Extracorporeal Membrane Oxygenation (ECMO) Time: Up to 28 days
Measure: Ventilator-Free Days Time: Up to 28 days
Measure: Incidence of Intensive Care Unit (ICU) Stay Time: Up to 28 days
Measure: Duration of ICU Stay Time: Up to 28 days
Measure: Time to Clinical Failure, Defined as the Time to Death, Mechanical Ventilation, ICU Admission, or Withdrawal of Care (Whichever Occurs First) Time: Up to 28 days
Measure: Mortality Rate at Days 14 and 28 Time: Days 14 and 28
Measure: Time to Clinical Improvement, Defined as a National Early Warning Score 2 (NEWS2) of ≤2 Maintained for 24 hours Time: Up to 28 days
Measure: Incidence and Severity of Adverse Events, with Severity Determined According to National Cancer Institute Common Terminology Criteria for Adverse Events, Version 5.0 (NCI CTCAE v5.0) Time: Up to 60 days
Measure: Change from Baseline in Respiratory Rate Time: From Baseline up to 60 days
Measure: Change from Baseline in Pulse Rate Time: From Baseline up to 60 days
Measure: Change from Baseline in Systolic Blood Pressure Time: From Baseline up to 60 days
Measure: Change from Baseline in Diastolic Blood Pressure Time: From Baseline up to 60 days
Measure: Change from Baseline in Body Temperature Time: From Baseline up to 60 days
Measure: Change from Baseline in Oxygen Saturation Time: From Baseline up to 60 days
Measure: Change from Baseline in RR, QRS, PR, QT, and QTcF Intervals, as Measured by Electrocardiogram (ECG) Time: From Baseline up to 60 days
Measure: Change from Baseline in Heart Rate, as Measured by Electrocardiogram (ECG) Time: From Baseline up to 60 days
Measure: Number of Participants with Clinical Laboratory Test Abnormalities in Hematology Parameters Time: From Baseline up to 60 days
Measure: Number of Participants with Clinical Laboratory Test Abnormalities in Blood Chemistry Parameters Time: From Baseline up to 60 days
Measure: Serum Concentration of UTTR1147A at Specified Timepoints Time: At predefined timepoints from Baseline until Study Completion (up to 60 days)
Measure: Serum Concentration of MSTT1041A at Specified Timepoints Time: At predefined timepoints from Baseline until Study Completion (up to 60 days)
Measure: Prevalence of Anti-Drug Antibodies (ADAs) at Baseline and Incidence of ADAs During the Study Time: From Baseline up to 60 days
