Inclusion Criteria:

1. Male or non-pregnant female age ≥18 years, inclusive

2. Subject (or legally authorized representative) is able and willing to provide written
informed consent, which includes compliance with study requirements and restrictions
listed in the consent form

3. Has laboratory-confirmed SARS-CoV-2 infection as determined by PCR or other approved
clinical testing prior to randomization

4. Radiographic evidence of bilateral infiltrates

5. Subject requires high-flow oxygen or meets clinical classification for ARDS

6. Elevated serum CRP or ferritin

7. Subjects who have been treated with convalescent plasma (CP) prior to enrollment are
eligible if the subject continues to meet all inclusion criteria at screening

8. The use of investigational anti-viral treatment (e.g., remdesivir) is allowed if the
subject continues to meet all inclusion criteria at screening

Additional inclusion criteria are detailed in the protocol

Exclusion Criteria:

1. Evidence of life-threatening dysrhythmia or cardiac arrest on presentation

2. Intubated >72 hours

3. Absolute neutrophil count < 1,000 per mm3

4. Platelet count < 50,000 per mm3

5. AST or ALT > 5X upper limit of normal

6. eGFR <30 mL/min/1.73m2 or requiring hemofiltration or dialysis

7. History of known anti-GM-CSF autoantibodies or pulmonary alveolar proteinosis

8. Severe chronic respiratory disease (e.g., COPD, PAH, IPF, ILD) requiring supplemental
oxygen therapy or mechanical ventilation pre-hospitalization (e.g., prior to COVID-19
diagnosis)

9. Use of any immunomodulatory biologic, cell therapy, or small molecule JAK inhibitor
within past 7 days or 5 half lives or planned use of any of these agents unless
approved by medical monitor

10. Chronic (>4 weeks) use of corticosteroids >10mg/day of prednisone or equivalent

11. Known or suspected active and untreated TB, HIV, hepatitis B or C infection

Additional exclusion criteria are detailed in the protocol.