- requiring invasive mechanical ventilation or extracorporeal membrane oxygenation prior to randomization - confirmed diagnosis of bacterial pneumonia or other active/uncontrolled fungal or viral infections at screening/baseline - known active tuberculosis (tb), history of incompletely treated tb or suspected or known extrapulmonary tb - currently receiving treatment for hepatitis a, hepatitis b, hepatitis c or hiv infection - history of pulmonary alveolar proteinosis (pap) - women of childbearing potential who are pregnant or breastfeeding - known hypersensitivity to lenzilumab or any of its components - use of any fda authorized anti-il-6 (e.g., tocilizumab, sarilumab, sitlukimab), anti-il-1 (e.g., anakinra, canakinumab), kinase inhibitor (e.g., baracitinib, ibrutinib, acalabrutinib), or neutralizing monoclonal antibody (e.g. bamlanivimab or casirivimab/imdevimab) therapy to treat covid-19 within 8 weeks prior to randomization - use of gm-csf agents (e.g., sargramostim) within prior 2 months of randomization - expected survival < 48h in the opinion of the investigator - any condition that, in the opinion of the investigator, is likely to interfere with the safety and efficacy of the study treatment or puts the patient at unacceptably high risk from the study

- requiring invasive mechanical ventilation or extracorporeal membrane oxygenation prior to randomization - confirmed diagnosis of bacterial pneumonia or other active/uncontrolled fungal or viral infections at screening/baseline - known active tuberculosis (tb), history of incompletely treated tb or suspected or known extrapulmonary tb - currently receiving treatment for hepatitis a, hepatitis b, hepatitis c or hiv infection - history of pulmonary alveolar proteinosis (pap) - women of childbearing potential who are pregnant or breastfeeding - known hypersensitivity to lenzilumab or any of its components - use of any fda authorized anti-il-6 (e.g., tocilizumab, sarilumab, sitlukimab), anti-il-1 (e.g., anakinra, canakinumab), kinase inhibitor (e.g., baracitinib, ibrutinib, acalabrutinib), or neutralizing monoclonal antibody (e.g. bamlanivimab or casirivimab/imdevimab) therapy to treat covid-19 within 8 weeks prior to randomization - use of gm-csf agents (e.g., sargramostim) within prior 2 months of randomization - expected survival < 48h in the opinion of the investigator - any condition that, in the opinion of the investigator, is likely to interfere with the safety and efficacy of the study treatment or puts the patient at unacceptably high risk from the study

- requiring invasive mechanical ventilation or extracorporeal membrane oxygenation prior to randomization - confirmed diagnosis of bacterial pneumonia or other active/uncontrolled fungal or viral infections at screening/baseline - known active tuberculosis (tb), history of incompletely treated tb or suspected or known extrapulmonary tb - currently receiving treatment for hepatitis a, hepatitis b, hepatitis c or hiv infection - history of pulmonary alveolar proteinosis (pap) - women of childbearing potential who are pregnant or breastfeeding - known hypersensitivity to lenzilumab or any of its components - use of any fda approved anti-il-6 (e.g., tocilizumab, sarilumab, sitlukimab), anti-il-1 (e.g., anakinra, canakinumab) or kinase inhibitor (e.g., baracitinib, ibrutinib, acalabrutinib) therapy to treat covid-19 within 8 weeks prior to randomization - use of gm-csf agents (e.g., sargramostim) within prior 2 months of randomization - expected survival < 24h in the opinion of the investigator - any condition that, in the opinion of the investigator, is likely to interfere with the safety and efficacy of the study treatment or puts the patient at unacceptably high risk from the study

- requiring invasive mechanical ventilation or extracorporeal membrane oxygenation prior to randomization - confirmed diagnosis of bacterial pneumonia or other active/uncontrolled fungal or viral infections at screening/baseline - known active tuberculosis (tb), history of incompletely treated tb or suspected or known extrapulmonary tb - currently receiving treatment for hepatitis a, hepatitis b, hepatitis c or hiv infection - history of pulmonary alveolar proteinosis (pap) - women of childbearing potential who are pregnant or breastfeeding - known hypersensitivity to lenzilumab or any of its components - use of any fda approved anti-il-6 (e.g., tocilizumab, sarilumab, sitlukimab), anti-il-1 (e.g., anakinra, canakinumab) or kinase inhibitor (e.g., baracitinib, ibrutinib, acalabrutinib) therapy to treat covid-19 within 8 weeks prior to randomization - use of gm-csf agents (e.g., sargramostim) within prior 2 months of randomization - expected survival < 24h in the opinion of the investigator - any condition that, in the opinion of the investigator, is likely to interfere with the safety and efficacy of the study treatment or puts the patient at unacceptably high risk from the study