1. Adult patients with RT-PCR proven COVID-19 with moderate to severe pneumonia with fewer than 14 days of symptom onset that warranted hospitalization and currently receiving standard medication for COVID-19 at appropriate doses which would include, among others, antivirals, corticosteroids, or anti-IL-6 tocilizumab. <br/ >and <br/ >2. moderate to severe dyspnoea, respiratory frequency equal to or greater than 30/min, oxygen saturation without supplemental O2 supply SpO2 94% or less, PaO2/FiO2 ratio or PaFiO2 ratio between 200 to 300 or SpO2/FiO2 ratio 315 or less if PaO2 is not available <br/ >and/or <br/ >3. laboratory abnormalities such as C-reactive protein >100 mg/L or D-dimer >1000 ng/ml or IL-6 >50 IU or suspected cytokine release syndrome <br/ > <br/ >(Criteria 1 and 2 are mandatory and 3 is optional)

1. Adult patients with RT-PCR proven COVID-19 with moderate to severe pneumonia with fewer than 14 days of symptom onset that warranted hospitalization and currently receiving standard medication for COVID-19 at appropriate doses which would include, among others, antivirals, corticosteroids, or anti-IL-6 tocilizumab. <br/ >and <br/ >2. moderate to severe dyspnoea, respiratory frequency equal to or greater than 30/min, oxygen saturation without supplemental O2 supply SpO2 94% or less, PaO2/FiO2 ratio or PaFiO2 ratio between 200 to 300 or SpO2/FiO2 ratio 315 or less if PaO2 is not available <br/ >and/or <br/ >3. laboratory abnormalities such as C-reactive protein >100 mg/L or D-dimer >1000 ng/ml or IL-6 >50 IU or suspected cytokine release syndrome <br/ > <br/ >(Criteria 1 and 2 are mandatory and 3 is optional)

1. Adult patients with RT-PCR proven COVID-19 with moderate to severe pneumonia with fewer than 14 days of symptom onset that warranted hospitalization and currently receiving standard medication for COVID-19 at appropriate doses which would include, among others, antivirals, corticosteroids, or anti-IL-6 tocilizumab. <br/ >and <br/ >2. moderate to severe dyspnoea, respiratory frequency equal to or greater than 30/min, oxygen saturation without supplemental O2 supply SpO2 94% or less, PaO2/FiO2 ratio or PaFiO2 ratio between 200 to 300 or SpO2/FiO2 ratio 315 or less if PaO2 is not available <br/ >and/or <br/ >3. laboratory abnormalities such as C-reactive protein >100 mg/L or D-dimer >1000 ng/ml or IL-6 >50 IU or suspected cytokine release syndrome <br/ > <br/ >(Criteria 1 and 2 are mandatory and 3 is optional)

1. Adult patients with RT-PCR proven COVID-19 with moderate to severe pneumonia with fewer than 14 days of symptom onset that warranted hospitalization and currently receiving standard medication for COVID-19 at appropriate doses which would include, among others, antivirals, corticosteroids, or anti-IL-6 tocilizumab. <br/ >and <br/ >2. moderate to severe dyspnoea, respiratory frequency equal to or greater than 30/min, oxygen saturation without supplemental O2 supply SpO2 94% or less, PaO2/FiO2 ratio or PaFiO2 ratio between 200 to 300 or SpO2/FiO2 ratio 315 or less if PaO2 is not available <br/ >and/or <br/ >3. laboratory abnormalities such as C-reactive protein >100 mg/L or D-dimer >1000 ng/ml or IL-6 >50 IU or suspected cytokine release syndrome <br/ > <br/ >(Criteria 1 and 2 are mandatory and 3 is optional)