subjects who meet any of the following criteria will be excluded from participation in the study: * respiratory failure defined based on resource utilization requiring at least one of the following: endotracheal intubation and mechanical ventilation, oxygen delivered by high flow nasal cannula (\>40 liters per minute with fraction of delivered oxygen \>0.5), noninvasive positive pressure ventilation, extracorporeal membrane oxygenation (ecmo), or clinical diagnosis of respiratory failure (ie, clinical need for one of the preceding therapies, but preceding therapies unavailable due to resource limitation). * septic shock defined by systolic blood pressure \< 90 mm hg, or diastolic blood pressure \< 60 mm hg, or requiring vasopressor use. * multi-organ dysfunction or failure based on investigator's determination including sequential organ failure assessment (sofa) score. * unlikely to survive beyond 2 days at the discretion of investigator. * has received high-dose corticosteroids (dexamethasone \>12 mg/day or equivalent) for longer than 2 days within 72 hours prior to screening. however, corticosteroids at doses used as standard-of-care treatment for covid-19 per individual institution standard will be allowed. * chronic obstructive pulmonary disease or bronchial asthma requiring treatment within 3 months prior to screening. * clinical evidence of active or unstable cardiovascular diseases (i.e. heart failure or acute myocardial infarction) as determined by investigator assessment. * active liver disease or hepatic insufficiency or alanine aminotransferase or aspartate aminotransferase level \>5 times the upper limit of normal range at screening. * severe renal insufficiency requiring dialysis at screening. * any of the following abnormal laboratory values: absolute neutrophil count (anc) \< 1,000 per mm3, or platelets count \<50,000 per mm3 detected within 48 hours at screening per local lab. * a history of an invasive malignancy within the past 5 years except for the following circumstances: malignant tumors cured with no recurrence in the past 5 years, completely resected basal cell or squamous cell carcinoma of the skin, and/or completely resected carcinoma in situ of any type. * active tuberculosis (tb) or uncontrolled tb, or severe infection caused by bacteria or fungi within 4 weeks prior to screening * history of human immunodeficiency virus (hiv) infection or hepatitis b or hepatitis c. * has received any other investigational therapeutic products within 8 weeks or 5 half-lives, whichever is longer, prior to screening. * a known serious allergic reaction or hypersensitivity to components of f-652.

subjects who meet any of the following criteria will be excluded from participation in the study: * respiratory failure defined based on resource utilization requiring at least one of the following: endotracheal intubation and mechanical ventilation, oxygen delivered by high flow nasal cannula (\>40 liters per minute with fraction of delivered oxygen \>0.5), noninvasive positive pressure ventilation, extracorporeal membrane oxygenation (ecmo), or clinical diagnosis of respiratory failure (ie, clinical need for one of the preceding therapies, but preceding therapies unavailable due to resource limitation). * septic shock defined by systolic blood pressure \< 90 mm hg, or diastolic blood pressure \< 60 mm hg, or requiring vasopressor use. * multi-organ dysfunction or failure based on investigator's determination including sequential organ failure assessment (sofa) score. * unlikely to survive beyond 2 days at the discretion of investigator. * has received high-dose corticosteroids (dexamethasone \>12 mg/day or equivalent) for longer than 2 days within 72 hours prior to screening. however, corticosteroids at doses used as standard-of-care treatment for covid-19 per individual institution standard will be allowed. * chronic obstructive pulmonary disease or bronchial asthma requiring treatment within 3 months prior to screening. * clinical evidence of active or unstable cardiovascular diseases (i.e. heart failure or acute myocardial infarction) as determined by investigator assessment. * active liver disease or hepatic insufficiency or alanine aminotransferase or aspartate aminotransferase level \>5 times the upper limit of normal range at screening. * severe renal insufficiency requiring dialysis at screening. * any of the following abnormal laboratory values: absolute neutrophil count (anc) \< 1,000 per mm3, or platelets count \<50,000 per mm3 detected within 48 hours at screening per local lab. * a history of an invasive malignancy within the past 5 years except for the following circumstances: malignant tumors cured with no recurrence in the past 5 years, completely resected basal cell or squamous cell carcinoma of the skin, and/or completely resected carcinoma in situ of any type. * active tuberculosis (tb) or uncontrolled tb, or severe infection caused by bacteria or fungi within 4 weeks prior to screening * history of human immunodeficiency virus (hiv) infection or hepatitis b or hepatitis c. * has received any other investigational therapeutic products within 8 weeks or 5 half-lives, whichever is longer, prior to screening. * a known serious allergic reaction or hypersensitivity to components of f-652.

subjects who meet any of the following criteria will be excluded from participation in the study: respiratory failure defined based on resource utilization requiring at least one of the following: endotracheal intubation and mechanical ventilation, oxygen delivered by high flow nasal cannula (>40 liters per minute with fraction of delivered oxygen >0.5), noninvasive positive pressure ventilation, extracorporeal membrane oxygenation (ecmo), or clinical diagnosis of respiratory failure (ie, clinical need for one of the preceding therapies, but preceding therapies unavailable due to resource limitation). septic shock defined by systolic blood pressure < 90 mm hg, or diastolic blood pressure < 60 mm hg, or requiring vasopressor use. multi-organ dysfunction or failure based on investigator's determination including sequential organ failure assessment (sofa) score. unlikely to survive beyond 2 days at the discretion of investigator. has received high-dose corticosteroids (dexamethasone >12 mg/day or equivalent) for longer than 2 days within 72 hours prior to screening. however, corticosteroids at doses used as standard-of-care treatment for covid-19 per individual institution standard will be allowed. chronic obstructive pulmonary disease or bronchial asthma requiring treatment within 3 months prior to screening. clinical evidence of active or unstable cardiovascular diseases (i.e. heart failure or acute myocardial infarction) as determined by investigator assessment. active liver disease or hepatic insufficiency or alanine aminotransferase or aspartate aminotransferase level >5 times the upper limit of normal range at screening. severe renal insufficiency requiring dialysis at screening. any of the following abnormal laboratory values: absolute neutrophil count (anc) < 1,000 per mm3, or platelets count <50,000 per mm3 detected within 48 hours at screening per local lab. a history of an invasive malignancy within the past 5 years except for the following circumstances: malignant tumors cured with no recurrence in the past 5 years, completely resected basal cell or squamous cell carcinoma of the skin, and/or completely resected carcinoma in situ of any type. active tuberculosis (tb) or uncontrolled tb, or severe infection caused by bacteria or fungi within 4 weeks prior to screening history of human immunodeficiency virus (hiv) infection or hepatitis b or hepatitis c. has received any other investigational therapeutic products within 8 weeks or 5 half-lives, whichever is longer, prior to screening. a known serious allergic reaction or hypersensitivity to components of f-652.

subjects who meet any of the following criteria will be excluded from participation in the study: respiratory failure defined based on resource utilization requiring at least one of the following: endotracheal intubation and mechanical ventilation, oxygen delivered by high flow nasal cannula (>40 liters per minute with fraction of delivered oxygen >0.5), noninvasive positive pressure ventilation, extracorporeal membrane oxygenation (ecmo), or clinical diagnosis of respiratory failure (ie, clinical need for one of the preceding therapies, but preceding therapies unavailable due to resource limitation). septic shock defined by systolic blood pressure < 90 mm hg, or diastolic blood pressure < 60 mm hg, or requiring vasopressor use. multi-organ dysfunction or failure based on investigator's determination including sequential organ failure assessment (sofa) score. unlikely to survive beyond 2 days at the discretion of investigator. has received high-dose corticosteroids (dexamethasone >12 mg/day or equivalent) for longer than 2 days within 72 hours prior to screening. however, corticosteroids at doses used as standard-of-care treatment for covid-19 per individual institution standard will be allowed. chronic obstructive pulmonary disease or bronchial asthma requiring treatment within 3 months prior to screening. clinical evidence of active or unstable cardiovascular diseases (i.e. heart failure or acute myocardial infarction) as determined by investigator assessment. active liver disease or hepatic insufficiency or alanine aminotransferase or aspartate aminotransferase level >5 times the upper limit of normal range at screening. severe renal insufficiency requiring dialysis at screening. any of the following abnormal laboratory values: absolute neutrophil count (anc) < 1,000 per mm3, or platelets count <50,000 per mm3 detected within 48 hours at screening per local lab. a history of an invasive malignancy within the past 5 years except for the following circumstances: malignant tumors cured with no recurrence in the past 5 years, completely resected basal cell or squamous cell carcinoma of the skin, and/or completely resected carcinoma in situ of any type. active tuberculosis (tb) or uncontrolled tb, or severe infection caused by bacteria or fungi within 4 weeks prior to screening history of human immunodeficiency virus (hiv) infection or hepatitis b or hepatitis c. has received any other investigational therapeutic products within 8 weeks or 5 half-lives, whichever is longer, prior to screening. a known serious allergic reaction or hypersensitivity to components of f-652.