- Hospitalized with laboratory-confirmed (RT-PCR+) or highly suspected (compatible with at least bilobar lung involvement without another plausible diagnosis) COVID-19 - Age ≥18 years - Weight ≤100 kg - Within 24 hours of reaching a WHO severity score of 4-6 either: - At admission - While already hospitalized. Informed consent obtained from subject/next of kin/legal proxy Primary admitting diagnosis of pneumonia supported by a compatible clinical presentation with a documented infiltrate consistent with pneumonia on CXR or CT, as assessed by the admitting emergency department (ED), clinic, or ward physician or equivalent caregiver Recommended (not mandatory) guidance/discretionary criteria defining patients with pneumonia satisfying all 4 categories below: - At least 2 symptoms: difficulty breathing, cough, production of purulent sputum, or chest pain - At least 2 vital sign abnormalities: fever, tachycardia, or tachypnea (thresholds -- fever: oral or core temperature >100.4°F [38°C], heart rate >100 beats/min, respiratory rate >24/min) - At least one finding of other clinical signs and laboratory abnormalities: hypoxemia (O2 saturation <90%), clinical evidence of pulmonary consolidation, or leukocytosis ≥1.5x104 or leukopenia <4x103 - Chest imaging, or CT chest showing at least bilobar pulmonary infiltrates Principal Investigator (PI) to note radiologic findings in the electronic case report form (eCRF) Radiology report to be placed in the eCRF A copy of the radiograph attached to be saved for review A hyperinflammatory status (defined by increased ferritin ≥500 µg/L, D-dimer ≥1000 ng/mL, or CRP ≥75 mg/L) During the course of the study starting at screening and for at least 6 months after their final study treatment: - Female subjects of childbearing potential must agree to use 2 medically accepted birth control methods - Male subjects with a partner who might become pregnant must agree to use reliable forms of contraception (i.e., vasectomy, abstinence), or an acceptable method of birth control must be used by the partner - All subjects must agree not to donate sperm or eggs (ovocytes)

- Hospitalized with laboratory-confirmed (RT-PCR+) or highly suspected (compatible with at least bilobar lung involvement without another plausible diagnosis) COVID-19 - Age ≥18 years - Weight ≤100 kg - Within 24 hours of reaching a WHO severity score of 4-6 either: - At admission - While already hospitalized. Informed consent obtained from subject/next of kin/legal proxy Primary admitting diagnosis of pneumonia supported by a compatible clinical presentation with a documented infiltrate consistent with pneumonia on CXR or CT, as assessed by the admitting emergency department (ED), clinic, or ward physician or equivalent caregiver Recommended (not mandatory) guidance/discretionary criteria defining patients with pneumonia satisfying all 4 categories below: - At least 2 symptoms: difficulty breathing, cough, production of purulent sputum, or chest pain - At least 2 vital sign abnormalities: fever, tachycardia, or tachypnea (thresholds -- fever: oral or core temperature >100.4°F [38°C], heart rate >100 beats/min, respiratory rate >24/min) - At least one finding of other clinical signs and laboratory abnormalities: hypoxemia (O2 saturation <90%), clinical evidence of pulmonary consolidation, or leukocytosis ≥1.5x104 or leukopenia <4x103 - Chest imaging, or CT chest showing at least bilobar pulmonary infiltrates Principal Investigator (PI) to note radiologic findings in the electronic case report form (eCRF) Radiology report to be placed in the eCRF A copy of the radiograph attached to be saved for review A hyperinflammatory status (defined by increased ferritin ≥500 µg/L, D-dimer ≥1000 ng/mL, or CRP ≥75 mg/L) During the course of the study starting at screening and for at least 6 months after their final study treatment: - Female subjects of childbearing potential must agree to use 2 medically accepted birth control methods - Male subjects with a partner who might become pregnant must agree to use reliable forms of contraception (i.e., vasectomy, abstinence), or an acceptable method of birth control must be used by the partner - All subjects must agree not to donate sperm or eggs (ovocytes)