* known severe allergic reactions to tcz or other monoclonal antibodies * active tuberculosis (tb) infection * suspected active bacterial, fungal, viral, or other infection (besides covid-19) * in the opinion of the investigator, progression to death is imminent and inevitable within the next 24 hours, irrespective of the provision of treatments * have received oral anti-rejection or immunomodulatory drugs (including tcz) with the past 3 months * participating in other drug clinical trials (participation in covid-19 anti-viral trials may be permitted if approved by medical monitor) * pregnant or breastfeeding, or positive pregnancy test in a pre-dose examination * treatment with an investigational drug within 5 half-lives or 30 days (whichever is longer) of randomization (investigational covid-19 antivirals may be permitted if approved by medial monitor) * any serious medical condition or abnormality of clinical laboratory tests that, in the investigator's judgment, precludes the patient's safe participation in and completion of the study * alanine aminotransferase (alt) or aspartate aminotransferase (ast) \> 10 x upper limit of normal (uln) detected within 24 hours at screening (per local lab) * absolute neutrophil count (anc) \< 1000/ml at screening (per local lab) * platelet count \< 50,000/ml at screening (per local lab)

* known severe allergic reactions to tcz or other monoclonal antibodies * active tuberculosis (tb) infection * suspected active bacterial, fungal, viral, or other infection (besides covid-19) * in the opinion of the investigator, progression to death is imminent and inevitable within the next 24 hours, irrespective of the provision of treatments * have received oral anti-rejection or immunomodulatory drugs (including tcz) with the past 3 months * participating in other drug clinical trials (participation in covid-19 anti-viral trials may be permitted if approved by medical monitor) * pregnant or breastfeeding, or positive pregnancy test in a pre-dose examination * treatment with an investigational drug within 5 half-lives or 30 days (whichever is longer) of randomization (investigational covid-19 antivirals may be permitted if approved by medial monitor) * any serious medical condition or abnormality of clinical laboratory tests that, in the investigator's judgment, precludes the patient's safe participation in and completion of the study * alanine aminotransferase (alt) or aspartate aminotransferase (ast) \> 10 x upper limit of normal (uln) detected within 24 hours at screening (per local lab) * absolute neutrophil count (anc) \< 1000/ml at screening (per local lab) * platelet count \< 50,000/ml at screening (per local lab)

- known severe allergic reactions to tcz or other monoclonal antibodies - active tuberculosis (tb) infection - suspected active bacterial, fungal, viral, or other infection (besides covid-19) - in the opinion of the investigator, progression to death is imminent and inevitable within the next 24 hours, irrespective of the provision of treatments - have received oral anti-rejection or immunomodulatory drugs (including tcz) with the past 3 months - participating in other drug clinical trials (participation in covid-19 anti-viral trials may be permitted if approved by medical monitor) - pregnant or breastfeeding, or positive pregnancy test in a pre-dose examination - treatment with an investigational drug within 5 half-lives or 30 days (whichever is longer) of randomization (investigational covid-19 antivirals may be permitted if approved by medial monitor) - any serious medical condition or abnormality of clinical laboratory tests that, in the investigator's judgment, precludes the patient's safe participation in and completion of the study - alanine aminotransferase (alt) or aspartate aminotransferase (ast) > 10 x upper limit of normal (uln) detected within 24 hours at screening (per local lab) - absolute neutrophil count (anc) < 1000/ml at screening (per local lab) - platelet count < 50,000/ml at screening (per local lab)

- known severe allergic reactions to tcz or other monoclonal antibodies - active tuberculosis (tb) infection - suspected active bacterial, fungal, viral, or other infection (besides covid-19) - in the opinion of the investigator, progression to death is imminent and inevitable within the next 24 hours, irrespective of the provision of treatments - have received oral anti-rejection or immunomodulatory drugs (including tcz) with the past 3 months - participating in other drug clinical trials (participation in covid-19 anti-viral trials may be permitted if approved by medical monitor) - pregnant or breastfeeding, or positive pregnancy test in a pre-dose examination - treatment with an investigational drug within 5 half-lives or 30 days (whichever is longer) of randomization (investigational covid-19 antivirals may be permitted if approved by medial monitor) - any serious medical condition or abnormality of clinical laboratory tests that, in the investigator's judgment, precludes the patient's safe participation in and completion of the study - alanine aminotransferase (alt) or aspartate aminotransferase (ast) > 10 x upper limit of normal (uln) detected within 24 hours at screening (per local lab) - absolute neutrophil count (anc) < 1000/ml at screening (per local lab) - platelet count < 50,000/ml at screening (per local lab)