inclusion criteria * hospitalized with covid-19 pneumonia confirmed per a positive polymerase chain reaction (pcr) of any specimen (e.g., respiratory, blood, urine, stool, other bodily fluid) and evidenced by chest x-ray or ct scan * requiring more than 6 l/min supplemental oxygen to maintain spo2 \> 93% * agrees to not participate in another clinical trial for the treatment of covid-19 while participating in this study exclusion criteria * known severe allergic reactions to tocilizumab or other monoclonal antibodies * known hypersensitivity to remdesivir, the metabolites, or formulation excipients * 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 * treatment with immunosuppressive or immunomodulatory therapy (including tocilizumab) within the past 3 months * concurrent treatment with other agents with actual or possible direct-acting antiviral activity against sars-cov-2 within 24 hours prior to study drug dosing. in addition, participants with prior or current treatment with \> 2 doses of remdesivir for covid-19 are excluded * participating in other drug clinical trials * estimated glomerular filtration rate (egfr) \< 30 ml/min (including patients receiving hemodialysis or hemofiltration) * alanine aminotransferase (alt) or aspartate aminotransferase (ast) \> 5 x upper limit of normal (uln) detected within 24 hours of screening (according to local laboratory reference ranges) * absolute neutrophil count (anc) \< 1000/ul at screening * platelet count \< 50,000/ul at screening * body weight \< 40 kg * treatment with an investigational drug within 5 half-lives or 30 days (whichever is longer) of randomization

inclusion criteria * hospitalized with covid-19 pneumonia confirmed per a positive polymerase chain reaction (pcr) of any specimen (e.g., respiratory, blood, urine, stool, other bodily fluid) and evidenced by chest x-ray or ct scan * requiring more than 6 l/min supplemental oxygen to maintain spo2 \> 93% * agrees to not participate in another clinical trial for the treatment of covid-19 while participating in this study exclusion criteria * known severe allergic reactions to tocilizumab or other monoclonal antibodies * known hypersensitivity to remdesivir, the metabolites, or formulation excipients * 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 * treatment with immunosuppressive or immunomodulatory therapy (including tocilizumab) within the past 3 months * concurrent treatment with other agents with actual or possible direct-acting antiviral activity against sars-cov-2 within 24 hours prior to study drug dosing. in addition, participants with prior or current treatment with \> 2 doses of remdesivir for covid-19 are excluded * participating in other drug clinical trials * estimated glomerular filtration rate (egfr) \< 30 ml/min (including patients receiving hemodialysis or hemofiltration) * alanine aminotransferase (alt) or aspartate aminotransferase (ast) \> 5 x upper limit of normal (uln) detected within 24 hours of screening (according to local laboratory reference ranges) * absolute neutrophil count (anc) \< 1000/ul at screening * platelet count \< 50,000/ul at screening * body weight \< 40 kg * treatment with an investigational drug within 5 half-lives or 30 days (whichever is longer) of randomization

inclusion criteria - hospitalized with covid-19 pneumonia confirmed per a positive polymerase chain reaction (pcr) of any specimen (e.g., respiratory, blood, urine, stool, other bodily fluid) and evidenced by chest x-ray or ct scan - requiring more than 6 l/min supplemental oxygen to maintain spo2 > 93% - agrees to not participate in another clinical trial for the treatment of covid-19 while participating in this study exclusion criteria - known severe allergic reactions to tocilizumab or other monoclonal antibodies - known hypersensitivity to remdesivir, the metabolites, or formulation excipients - 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 - treatment with immunosuppressive or immunomodulatory therapy (including tocilizumab) within the past 3 months - concurrent treatment with other agents with actual or possible direct-acting antiviral activity against sars-cov-2 within 24 hours prior to study drug dosing. in addition, participants with prior or current treatment with > 2 doses of remdesivir for covid-19 are excluded - participating in other drug clinical trials - estimated glomerular filtration rate (egfr) < 30 ml/min (including patients receiving hemodialysis or hemofiltration) - alanine aminotransferase (alt) or aspartate aminotransferase (ast) > 5 x upper limit of normal (uln) detected within 24 hours of screening (according to local laboratory reference ranges) - absolute neutrophil count (anc) < 1000/ul at screening - platelet count < 50,000/ul at screening - body weight < 40 kg - treatment with an investigational drug within 5 half-lives or 30 days (whichever is longer) of randomization

inclusion criteria - hospitalized with covid-19 pneumonia confirmed per a positive polymerase chain reaction (pcr) of any specimen (e.g., respiratory, blood, urine, stool, other bodily fluid) and evidenced by chest x-ray or ct scan - requiring more than 6 l/min supplemental oxygen to maintain spo2 > 93% - agrees to not participate in another clinical trial for the treatment of covid-19 while participating in this study exclusion criteria - known severe allergic reactions to tocilizumab or other monoclonal antibodies - known hypersensitivity to remdesivir, the metabolites, or formulation excipients - 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 - treatment with immunosuppressive or immunomodulatory therapy (including tocilizumab) within the past 3 months - concurrent treatment with other agents with actual or possible direct-acting antiviral activity against sars-cov-2 within 24 hours prior to study drug dosing. in addition, participants with prior or current treatment with > 2 doses of remdesivir for covid-19 are excluded - participating in other drug clinical trials - estimated glomerular filtration rate (egfr) < 30 ml/min (including patients receiving hemodialysis or hemofiltration) - alanine aminotransferase (alt) or aspartate aminotransferase (ast) > 5 x upper limit of normal (uln) detected within 24 hours of screening (according to local laboratory reference ranges) - absolute neutrophil count (anc) < 1000/ul at screening - platelet count < 50,000/ul at screening - body weight < 40 kg - treatment with an investigational drug within 5 half-lives or 30 days (whichever is longer) of randomization

inclusion criteria - hospitalized with covid-19 pneumonia confirmed per a positive polymerase chain reaction (pcr) of any specimen (e.g., respiratory, blood, urine, stool, other bodily fluid) and evidenced by chest x-ray or ct scan - requiring more than 6 l/min supplemental oxygen to maintain spo2 > 93% - agrees to not participate in another clinical trial for the treatment of covid-19 while participating in this study exclusion criteria - known severe allergic reactions to tocilizumab or other monoclonal antibodies - known hypersensitivity to remdesivir, the metabolites, or formulation excipients - 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 - treatment with immunosuppressive or immunomodulatory therapy (including tocilizumab) within the past 3 months - concurrent treatment with other agents with actual or possible direct-acting antiviral activity against sars-cov-2 within 24 hours prior to study drug dosing - participating in other drug clinical trials - estimated glomerular filtration rate (egfr) < 30 ml/min (including patients receiving hemodialysis or hemofiltration) - alanine aminotransferase (alt) or aspartate aminotransferase (ast) > 5 x upper limit of normal (uln) detected within 24 hours of screening (according to local laboratory reference ranges) - absolute neutrophil count (anc) < 1000/ul at screening - platelet count < 50,000/ul at screening - body weight < 40 kg - treatment with an investigational drug within 5 half-lives or 30 days (whichever is longer) of randomization

inclusion criteria - hospitalized with covid-19 pneumonia confirmed per a positive polymerase chain reaction (pcr) of any specimen (e.g., respiratory, blood, urine, stool, other bodily fluid) and evidenced by chest x-ray or ct scan - requiring more than 6 l/min supplemental oxygen to maintain spo2 > 93% - agrees to not participate in another clinical trial for the treatment of covid-19 while participating in this study exclusion criteria - known severe allergic reactions to tocilizumab or other monoclonal antibodies - known hypersensitivity to remdesivir, the metabolites, or formulation excipients - 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 - treatment with immunosuppressive or immunomodulatory therapy (including tocilizumab) within the past 3 months - concurrent treatment with other agents with actual or possible direct-acting antiviral activity against sars-cov-2 within 24 hours prior to study drug dosing - participating in other drug clinical trials - estimated glomerular filtration rate (egfr) < 30 ml/min (including patients receiving hemodialysis or hemofiltration) - alanine aminotransferase (alt) or aspartate aminotransferase (ast) > 5 x upper limit of normal (uln) detected within 24 hours of screening (according to local laboratory reference ranges) - absolute neutrophil count (anc) < 1000/ul at screening - platelet count < 50,000/ul at screening - body weight < 40 kg - treatment with an investigational drug within 5 half-lives or 30 days (whichever is longer) of randomization