Ordinal Scale 2-Point improvement was defined as percentage of participants with at least a 2-points improvement (increase from baseline) by Day 14. Baseline score was defined as the last score measured before first dosing. The 8-point ordinal scale ranges from 1 to 8: where 1= death, 2= hospitalized, on invasive mechanical ventilation or extracorporeal membrane oxygenation (ECMO); 3= hospitalized, on non-invasive ventilation or high flow oxygen devices; 4= hospitalized, requiring supplemental oxygen; 5= hospitalized, not requiring supplemental oxygen - requiring ongoing medical care (coronavirus disease 2019 [COVID-19] related or otherwise); 6= hospitalized, not requiring supplemental oxygen - no longer requires ongoing medical care; 7= not hospitalized, limitation on activities and/or requiring home oxygen; 8= not hospitalized, no limitations on activities.

The intent-to-treat (ITT) population included all participants who were randomized in the study with confirmed severe acute respiratory syndrome coronavirus (SARS-CoV2) infection under protocol version (PV) 6.0 and above, regardless of whether or not they receive study treatment.

Ordinal Scale 2-points improvement was defined as percentage of participants with at least a 2-points improvement (increase from baseline) by Day 7. Baseline score was defined as the last score measured before first dosing. The 8-point ordinal scale ranges from 1 to 8: where, 1= death, 2= hospitalized, on invasive mechanical ventilation or ECMO; 3= hospitalized, on non-invasive ventilation or high flow oxygen devices; 4= hospitalized, requiring supplemental oxygen; 5= hospitalized, not requiring supplemental oxygen - requiring ongoing medical care (COVID-19 related or otherwise); 6= hospitalized, not requiring supplemental oxygen - no longer requires ongoing medical care; 7= not hospitalized, limitation on activities and/or requiring home oxygen; 8= not hospitalized, no limitations on activities.

PV 1-6 population included participants randomized into the study under protocol versions 1-6.

Ordinal Scale 1-point improvement was defined as percentage of participants with at least 1-point improvement (increase from baseline) by Day 7 and 14. Baseline score was defined as the last score measured before first dosing. The 8-point ordinal scale ranges from 1 to 8: where 1= death, 2= hospitalized, on invasive mechanical ventilation or ECMO; 3= hospitalized, on non-invasive ventilation or high flow oxygen devices; 4= hospitalized, requiring supplemental oxygen; 5= hospitalized, not requiring supplemental oxygen - requiring ongoing medical care (COVID-19 related or otherwise); 6= hospitalized, not requiring supplemental oxygen - no longer requires ongoing medical care; 7= not hospitalized, limitation on activities and/or requiring home oxygen; 8= not hospitalized, no limitations on activities.

PV 1-6 population included participants randomized into the study under protocol versions 1-6.

TTCI-2 was defined as the time from randomization to an improvement of 2-points using 8-points Ordinal Scale. The 8-point ordinal scale ranges from 1 to 8: where 1= death, 2= hospitalized, on invasive mechanical ventilation or extracorporeal membrane oxygenation (ECMO); 3= hospitalized, on non-invasive ventilation or high flow oxygen devices; 4= hospitalized, requiring supplemental oxygen; 5= hospitalized, not requiring supplemental oxygen - requiring ongoing medical care (coronavirus disease 2019 [COVID-19] related or otherwise); 6= hospitalized, not requiring supplemental oxygen - no longer requires ongoing medical care; 7= not hospitalized, limitation on activities and/or requiring home oxygen; 8= not hospitalized, no limitations on activities.

ITT Population included all participants who were randomized in the study with confirmed SARS-CoV2 infection under protocol version 6.0 and above, regardless of whether or not they receive study treatment.

Overall death rate was defined as the percentage of participants who died on or before Day 28.

ITT population included all participants who were randomized in the study with confirmed SARS-CoV2 infection under protocol version 6.0 and above, regardless of whether or not they receive study treatment.

The rate of RMV was defined as the percentage of participants who ever used invasive mechanical ventilation or ECMO during the hospital stay.

ITT population included all participants who were randomized in the study with confirmed SARS-CoV2 infection under protocol version 6.0 and above, regardless of whether or not they receive study treatment.

The rate of ICU admission was defined as the percentage of participants with ICU admissions.

ITT population included all participants who were randomized in the study with confirmed SARS-CoV2 infection under protocol version 6.0 and above, regardless of whether or not they receive study treatment.

Length of hospitalization (days) was defined as (first hospital discharge date - date of randomization + 1).

ITT population included all participants who were randomized in the study with confirmed SARS-CoV2 infection under protocol version 6.0 and above, regardless of whether or not they receive study treatment.

The anti-inflammatory and immune effects of selinexor were assessed by CRP levels. Baseline was defined as the most recent non-missing measurement prior to the first administration of study treatment. Change from Baseline at the indicated time points was calculated as the value at the indicated time points minus the value at Baseline.

PV 1-6 population included participants randomized into the study under protocol versions 1-6. Here, "Number Analyzed" signified those participants who were evaluable for this outcome measure at a specified time-point.

The anti-inflammatory and immune effects of selinexor were assessed by ferritin levels. Baseline was defined as the most recent non-missing measurement prior to the first administration of study treatment. Change from Baseline at the indicated time points was calculated as the value at the indicated time points minus the value at Baseline.

PV 1-6 population included participants randomized into the study under protocol versions 1-6. Here, "Number Analyzed" signified those participants who were evaluable for this outcome measure at a specified timepoint.

The anti-inflammatory and immune effects of selinexor were assessed by LDH levels. Baseline was defined as the most recent non-missing measurement prior to the first administration of study treatment. Change from Baseline at the indicated time points was calculated as the value at the indicated time points minus the value at Baseline.

PV 1-6 population included participants randomized into the study under protocol versions 1-6. Here, "Number Analyzed" signified those participants who were evaluable for this outcome measure at a specified time-point.

The anti-inflammatory and immune effects of selinexor were assessed by blood plasma cytokines like IL-6. Baseline was defined as the most recent non-missing measurement prior to the first administration of study treatment. Change from Baseline at the indicated time points was calculated as the value at the indicated time points minus the value at Baseline.

PV 1-6 population included participants randomized into the study under protocol versions 1-6. Here, Overall Number of participants analyzed included all participants with baseline data and "Number Analyzed" signified those participants who were evaluable for this outcome measure at a specified time-point.

Adverse events are defined as any untoward medical occurrence in a participant or clinical investigation participant administered a pharmaceutical product and which does not necessarily have to have a causal relationship with this treatment. An AE can therefore be any unfavorable and unintended sign (including an abnormal laboratory finding, for example), symptom, or disease temporally associated with the use of study treatment, whether or not considered related to the study treatment. Serious adverse event (SAE) was an AE that resulted in any of the following outcomes: death; life threatening; persistent/significant disability/incapacity; initial or prolonged inpatient hospitalization; congenital anomaly/birth defect or was otherwise considered medically important. TEAEs are defined as those AEs that develop or worsen after the first dose of study drug. TEAEs included both Serious and non-serious TEAEs.

All-treat population consisted of the subset of ITT participants who took at least one dose of study treatment on this study.