-Recent (≥6 days of flu-like symptoms or malaise yet ≤16 days of flu-like symptoms or malaise prior to randomization) infection with COVID-19.Confident COVID-19 diagnosis confirmed by antigen detection test and/or PCR and/or positive serology, or any emerging and validated diagnostic laboratory test for COVID-19 within this period. -In some patients, it may be impossible to get a confident laboratory confirmation of COVID-19 diagnosis after 24h of hospital admission because viral load is low and/or problems with diagnostic sensitivity. In those cases, in absence of an alternative diagnosis, and with highly suspect bilateral ground glass opacities on recent (<24h) chest-CT scan (confirmed by a radiologist and pulmonary physician as probable COVID-19), and a typical clinical and chemical diagnosis with signs of cytokine release syndrome, a patient can be enrolled as probable COVID-19 infected. In all cases, this needs confirmation by later seroconversion. -Presence of hypoxia defined as PaO2/FiO2 below 350 while breathing room air in upright position or PaO2/FiO2 below 280 on supplemental oxygen and immediately requiring high flow oxygen device or mechanical ventilation. -signs of cytokine release syndrome defined as ANY of the following -serum ferritin concentration >1000 mcg/L and rising since last 24h -single ferritin above 2000 mcg/L in patients requiring immediate high flow oxygen device or mechanical ventilation -lymphopenia defined as <800 lymphocytes/microliter and two of the following extra criteria Ferritin > 700 mcg/L and rising since last 24h -increased LDH (above 300 IU/L) and rising since last 24h -D-Dimers > 1000 ng/mL and rising since last 24h -CRP above 70 mg/L and rising since last 24h and absence of bacterial infection -if three of the above are present at admission, no need to document 24h rise -Chest X-ray and/or CT scan showing bilateral infiltrates within last 2 days -Admitted to specialized COVID-19 ward or an ICU ward taking care of COVID-19 patients -Age ≥ 18 years -Male or Female - Women of childbearing potential must have a negative serum pregnancy test pre-dose on day 1. Women of childbearing potential must consistently and correctly use (during the entire treatment period and 3 months after last reatment) 1 highly effective method for contraception. -Willing and able to provide informed consent or legal representative willing to provide informed consent

-Recent (≥6 days of flu-like symptoms or malaise yet ≤16 days of flu-like symptoms or malaise prior to randomization) infection with COVID-19.Confident COVID-19 diagnosis confirmed by antigen detection test and/or PCR and/or positive serology, or any emerging and validated diagnostic laboratory test for COVID-19 within this period. -In some patients, it may be impossible to get a confident laboratory confirmation of COVID-19 diagnosis after 24h of hospital admission because viral load is low and/or problems with diagnostic sensitivity. In those cases, in absence of an alternative diagnosis, and with highly suspect bilateral ground glass opacities on recent (<24h) chest-CT scan (confirmed by a radiologist and pulmonary physician as probable COVID-19), and a typical clinical and chemical diagnosis with signs of cytokine release syndrome, a patient can be enrolled as probable COVID-19 infected. In all cases, this needs confirmation by later seroconversion. -Presence of hypoxia defined as PaO2/FiO2 below 350 while breathing room air in upright position or PaO2/FiO2 below 280 on supplemental oxygen and immediately requiring high flow oxygen device or mechanical ventilation. -signs of cytokine release syndrome defined as ANY of the following -serum ferritin concentration >1000 mcg/L and rising since last 24h -single ferritin above 2000 mcg/L in patients requiring immediate high flow oxygen device or mechanical ventilation -lymphopenia defined as <800 lymphocytes/microliter and two of the following extra criteria Ferritin > 700 mcg/L and rising since last 24h -increased LDH (above 300 IU/L) and rising since last 24h -D-Dimers > 1000 ng/mL and rising since last 24h -CRP above 70 mg/L and rising since last 24h and absence of bacterial infection -if three of the above are present at admission, no need to document 24h rise -Chest X-ray and/or CT scan showing bilateral infiltrates within last 2 days -Admitted to specialized COVID-19 ward or an ICU ward taking care of COVID-19 patients -Age ≥ 18 years -Male or Female - Women of childbearing potential must have a negative serum pregnancy test pre-dose on day 1. Women of childbearing potential must consistently and correctly use (during the entire treatment period and 3 months after last reatment) 1 highly effective method for contraception. -Willing and able to provide informed consent or legal representative willing to provide informed consent