1. Pregnant, or intend to become pregnant or breastfeed during the study. 2. Patients who are unable to swallow the capsule. 3. Require invasive mechanical ventilation, including extracorporeal membrane oxygenation (ECMO) at study entry. 4. Receiving cytotoxic or biologic treatments (such as tumor necrosis factor (TNF) inhibitors, anti-interleukin-1 (IL-1), anti-IL-6 (tocilizumab or sarilumab), T-cell or B-cell targeted therapies (rituximab), interferon, or Janus kinase (JAK) inhibitors for any indication at study entry. A washout period 4 weeks (or 5 half-lives, whichever is longer) is required prior to screening. 5. Ever received convalescent plasma or intravenous immunoglobulin (IVIg) for COVID-19. 6. Have received high dose corticosteroids at doses >20 mg per day (or prednisone equivalent) administered for ≥14 consecutive days in the month prior to study entry. 7. Have diagnosis of primary tuberculosis (TB) or, if known, latent TB treated for less than 4 weeks with appropriate anti-tuberculosis therapy per local guidelines (by history only, no screening tests required). 8. Suspected serious, active bacterial, fungal, viral, or other infection (besides COVID-19) that in the opinion of the investigator could constitute a risk when taking investigational product. 9. Have received any live vaccine within 4 weeks before screening, or intend to receive a live vaccine during the study. Use of non-live (inactivated) vaccinations is allowed 10. Current diagnosis of active malignancy that, in the opinion of the investigator, could constitute a risk when taking investigational product. 11. Have a history of venous thromboembolism (VTE) (deep vein thrombosis (DVT) and pulmonary embolism (PE) within 12 weeks prior to randomization or have a history of recurrent (>1) VTE (DVT/PE). 12. Anticipated discharge from the hospital, or transfer to another hospital (or another unit), which is not a study site within 72 hours after study entry. 13. Have neutropenia (absolute neutrophil count <1000 cells/mLμL). 14. Have lymphopenia (absolute lymphocyte count <200 cells/mLμL). 15. Have alanine aminotransferase (ALT) or aspartate aminotransferase (AST) >5x ULN. 16. Have total bilirubin > 1.5 x upper limit of normal. 17. Estimated glomerular filtration rate (eGFR) <30 milliliter/minute/1.73 m2. 18. Have a known hypersensitivity to rabeximod or any of its excipients. 19. Are currently enrolled in any other clinical study involving an investigation product or any other type of medical research judged not to be scientifically or medically compatible with this study. The participant should not be enrolled (start) in another clinical trial for the treatment of COVID-19 or SARS CoV-2 through Day 28. 20. Are using or will use extracorporeal blood purification (EBP) device to remove proinflammatory cytokines from the blood such as a cytokine absorption or filtering device, for example, CytoSorb®. 21. Are unlikely to survive for at least 48 hours after screening in the opinion of the investigator

1. Pregnant, or intend to become pregnant or breastfeed during the study. 2. Patients who are unable to swallow the capsule. 3. Require invasive mechanical ventilation, including extracorporeal membrane oxygenation (ECMO) at study entry. 4. Receiving cytotoxic or biologic treatments (such as tumor necrosis factor (TNF) inhibitors, anti-interleukin-1 (IL-1), anti-IL-6 (tocilizumab or sarilumab), T-cell or B-cell targeted therapies (rituximab), interferon, or Janus kinase (JAK) inhibitors for any indication at study entry. A washout period 4 weeks (or 5 half-lives, whichever is longer) is required prior to screening. 5. Ever received convalescent plasma or intravenous immunoglobulin (IVIg) for COVID-19. 6. Have received high dose corticosteroids at doses >20 mg per day (or prednisone equivalent) administered for ≥14 consecutive days in the month prior to study entry. 7. Have diagnosis of primary tuberculosis (TB) or, if known, latent TB treated for less than 4 weeks with appropriate anti-tuberculosis therapy per local guidelines (by history only, no screening tests required). 8. Suspected serious, active bacterial, fungal, viral, or other infection (besides COVID-19) that in the opinion of the investigator could constitute a risk when taking investigational product. 9. Have received any live vaccine within 4 weeks before screening, or intend to receive a live vaccine during the study. Use of non-live (inactivated) vaccinations is allowed 10. Current diagnosis of active malignancy that, in the opinion of the investigator, could constitute a risk when taking investigational product. 11. Have a history of venous thromboembolism (VTE) (deep vein thrombosis (DVT) and pulmonary embolism (PE) within 12 weeks prior to randomization or have a history of recurrent (>1) VTE (DVT/PE). 12. Anticipated discharge from the hospital, or transfer to another hospital (or another unit), which is not a study site within 72 hours after study entry. 13. Have neutropenia (absolute neutrophil count <1000 cells/mLμL). 14. Have lymphopenia (absolute lymphocyte count <200 cells/mLμL). 15. Have alanine aminotransferase (ALT) or aspartate aminotransferase (AST) >5x ULN. 16. Have total bilirubin > 1.5 x upper limit of normal. 17. Estimated glomerular filtration rate (eGFR) <30 milliliter/minute/1.73 m2. 18. Have a known hypersensitivity to rabeximod or any of its excipients. 19. Are currently enrolled in any other clinical study involving an investigation product or any other type of medical research judged not to be scientifically or medically compatible with this study. The participant should not be enrolled (start) in another clinical trial for the treatment of COVID-19 or SARS CoV-2 through Day 28. 20. Are using or will use extracorporeal blood purification (EBP) device to remove proinflammatory cytokines from the blood such as a cytokine absorption or filtering device, for example, CytoSorb®. 21. Are unlikely to survive for at least 48 hours after screening in the opinion of the investigator