* evidence of critical covid-19 based on: 1. respiratory failure (defined by endotracheal intubation and mechanical ventilation, oxygen delivered by high-flow nasal cannula, noninvasive positive pressure ventilation, or clinical diagnosis of respiratory failure in setting of resource limitations) 2. septic shock (defined by sbp \< 90 mm hg, or diastolic bp \< 60 mm hg) 3. multiple organ dysfunction/failure * in the opinion of the investigator, unlikely to survive for at least 48 hours from screening or anticipate mechanical ventilation within 48 hours * concurrent anti-viral and/or anti-inflammatory agents (e.g., biologics, hydroxychloroquine) are not permitted. * inadequate hematologic parameters as indicated by the following labs: 1. patients with severe neutropenia (anc \<1,000 x 10\^9/liter \[l\]) or 2. thrombocytopenia (e.g., platelets \<100,000 per microliter of blood) * inadequate renal function as indicated by creatinine clearance (crcl) \<20 milliliter per minute (ml/min) using the formula of cockcroft and gault. * inadequate hepatic function defined as ast or alt \> 5x the upper limit of normal or serum direct bilirubin \> 2.5x the upper limit of normal. * hyponatremia defined as sodium \< 135 milliequivalents per liter (meq/l). * in the opinion of the investigator, patients who are below their ideal body weight and would be unduly impacted by changes in their weight. * unable to take oral medication when informed consent is obtained. * patients with a legal guardian or who are incarcerated. * pregnant and breastfeeding women.

* evidence of critical covid-19 based on: 1. respiratory failure (defined by endotracheal intubation and mechanical ventilation, oxygen delivered by high-flow nasal cannula, noninvasive positive pressure ventilation, or clinical diagnosis of respiratory failure in setting of resource limitations) 2. septic shock (defined by sbp \< 90 mm hg, or diastolic bp \< 60 mm hg) 3. multiple organ dysfunction/failure * in the opinion of the investigator, unlikely to survive for at least 48 hours from screening or anticipate mechanical ventilation within 48 hours * concurrent anti-viral and/or anti-inflammatory agents (e.g., biologics, hydroxychloroquine) are not permitted. * inadequate hematologic parameters as indicated by the following labs: 1. patients with severe neutropenia (anc \<1,000 x 10\^9/liter \[l\]) or 2. thrombocytopenia (e.g., platelets \<100,000 per microliter of blood) * inadequate renal function as indicated by creatinine clearance (crcl) \<20 milliliter per minute (ml/min) using the formula of cockcroft and gault. * inadequate hepatic function defined as ast or alt \> 5x the upper limit of normal or serum direct bilirubin \> 2.5x the upper limit of normal. * hyponatremia defined as sodium \< 135 milliequivalents per liter (meq/l). * in the opinion of the investigator, patients who are below their ideal body weight and would be unduly impacted by changes in their weight. * unable to take oral medication when informed consent is obtained. * patients with a legal guardian or who are incarcerated. * pregnant and breastfeeding women.

evidence of critical covid-19 based on: respiratory failure (defined by endotracheal intubation and mechanical ventilation, oxygen delivered by high-flow nasal cannula, noninvasive positive pressure ventilation, or clinical diagnosis of respiratory failure in setting of resource limitations) septic shock (defined by sbp < 90 mm hg, or diastolic bp < 60 mm hg) multiple organ dysfunction/failure in the opinion of the investigator, unlikely to survive for at least 48 hours from screening or anticipate mechanical ventilation within 48 hours concurrent anti-viral and/or anti-inflammatory agents (e.g., biologics, hydroxychloroquine) are not permitted. inadequate hematologic parameters as indicated by the following labs: patients with severe neutropenia (anc <1,000 x 10^9/liter [l]) or thrombocytopenia (e.g., platelets <100,000 per microliter of blood) inadequate renal function as indicated by creatinine clearance (crcl) <20 milliliter per minute (ml/min) using the formula of cockcroft and gault. inadequate hepatic function defined as ast or alt > 5x the upper limit of normal or serum direct bilirubin > 2.5x the upper limit of normal. hyponatremia defined as sodium < 135 milliequivalents per liter (meq/l). in the opinion of the investigator, patients who are below their ideal body weight and would be unduly impacted by changes in their weight. unable to take oral medication when informed consent is obtained. patients with a legal guardian or who are incarcerated. pregnant and breastfeeding women.

evidence of critical covid-19 based on: respiratory failure (defined by endotracheal intubation and mechanical ventilation, oxygen delivered by high-flow nasal cannula, noninvasive positive pressure ventilation, or clinical diagnosis of respiratory failure in setting of resource limitations) septic shock (defined by sbp < 90 mm hg, or diastolic bp < 60 mm hg) multiple organ dysfunction/failure in the opinion of the investigator, unlikely to survive for at least 48 hours from screening or anticipate mechanical ventilation within 48 hours concurrent anti-viral and/or anti-inflammatory agents (e.g., biologics, hydroxychloroquine) are not permitted. inadequate hematologic parameters as indicated by the following labs: patients with severe neutropenia (anc <1,000 x 10^9/liter [l]) or thrombocytopenia (e.g., platelets <100,000 per microliter of blood) inadequate renal function as indicated by creatinine clearance (crcl) <20 milliliter per minute (ml/min) using the formula of cockcroft and gault. inadequate hepatic function defined as ast or alt > 5x the upper limit of normal or serum direct bilirubin > 2.5x the upper limit of normal. hyponatremia defined as sodium < 135 milliequivalents per liter (meq/l). in the opinion of the investigator, patients who are below their ideal body weight and would be unduly impacted by changes in their weight. unable to take oral medication when informed consent is obtained. patients with a legal guardian or who are incarcerated. pregnant and breastfeeding women.

- evidence of critical covid-19 based on: 1. respiratory failure (defined by endotracheal intubation and mechanical ventilation, oxygen delivered by high-flow nasal cannula, noninvasive positive pressure ventilation, or clinical diagnosis of respiratory failure in setting of resource limitations) 2. septic shock (defined by sbp < 90 mm hg, or diastolic bp < 60 mm hg) 3. multiple organ dysfunction/failure - in the opinion of the investigator, unlikely to survive for at least 48 hours from screening or anticipate mechanical ventilation within 48 hours - concurrent anti-viral and/or anti-inflammatory agents (e.g., biologics, hydroxychloroquine) are not permitted. - inadequate hematologic parameters as indicated by the following labs: 1. patients with severe neutropenia (anc <1,000 x 10^9/liter [l]) or 2. thrombocytopenia (e.g., platelets <100,000 per microliter of blood) - inadequate renal function as indicated by creatinine clearance (crcl) <20 milliliter per minute (ml/min) using the formula of cockcroft and gault. - inadequate hepatic function defined as ast or alt > 5x the upper limit of normal or serum direct bilirubin > 2.5x the upper limit of normal. - hyponatremia defined as sodium < 135 milliequivalents per liter (meq/l). - in the opinion of the investigator, patients who are below their ideal body weight and would be unduly impacted by changes in their weight. - unable to take oral medication when informed consent is obtained. - patients with a legal guardian or who are incarcerated. - pregnant and breastfeeding women.

- evidence of critical covid-19 based on: 1. respiratory failure (defined by endotracheal intubation and mechanical ventilation, oxygen delivered by high-flow nasal cannula, noninvasive positive pressure ventilation, or clinical diagnosis of respiratory failure in setting of resource limitations) 2. septic shock (defined by sbp < 90 mm hg, or diastolic bp < 60 mm hg) 3. multiple organ dysfunction/failure - in the opinion of the investigator, unlikely to survive for at least 48 hours from screening or anticipate mechanical ventilation within 48 hours - concurrent anti-viral and/or anti-inflammatory agents (e.g., biologics, hydroxychloroquine) are not permitted. - inadequate hematologic parameters as indicated by the following labs: 1. patients with severe neutropenia (anc <1,000 x 10^9/liter [l]) or 2. thrombocytopenia (e.g., platelets <100,000 per microliter of blood) - inadequate renal function as indicated by creatinine clearance (crcl) <20 milliliter per minute (ml/min) using the formula of cockcroft and gault. - inadequate hepatic function defined as ast or alt > 5x the upper limit of normal or serum direct bilirubin > 2.5x the upper limit of normal. - hyponatremia defined as sodium < 135 milliequivalents per liter (meq/l). - in the opinion of the investigator, patients who are below their ideal body weight and would be unduly impacted by changes in their weight. - unable to take oral medication when informed consent is obtained. - patients with a legal guardian or who are incarcerated. - pregnant and breastfeeding women.