1. active uncontrolled infection with a non-covid-19 agent. 2. diagnosis of ards that is not considered to be high-risk, as defined by pao2-to-fio2 ratio of ≥ 150 mm hg. 3. any irreversible disease or condition for which 6-month mortality is estimated to be greater than 50%. 4. end-stage liver disease with ascites unrelated to covid-19 (childs pugh score \> 12). 5. uncontrolled or significant cardiovascular disease, including but not limited to: (a) myocardial infarction, stroke, or transient ischemic attack within the past 30 days; (b) uncontrolled angina within the past 30 days; (c) any history of clinically significant arrhythmias such as ventricular tachycardia, ventricular fibrillation, or torsades de pointes; and (d) history of other clinically significant or uncontrolled heart disease, including: cardiomyopathy, congestive heart failure with new york heart association functional classification iii or iv, myocarditis, pericarditis, or significant pericardial effusion. 6. known chronic kidney disease of stage 4 or 5 severity or requiring hemodialysis. 7. covid-19-associated acute kidney injury requiring dialysis. 8. hiv, hepatitis b, or hepatitis c seropositive. 9. patients with baseline qtc interval prolongation, as defined by repeated demonstration of a qtc interval \>500 milliseconds. 10. patients on hydroxychloroquine (must discontinue at least 2-days before study entry). 11. pregnant or breastfeeding participants. 12. patients of childbearing age, or males who have a partner of childbearing potential, who are unwilling to practice contraception. effective forms of birth control, which must be continued through the entire on-study 6-month interval, include: abstinence; intrauterine device (iud); hormonal (birth control pills, injections, or implants); tubal ligation; or vasectomy. 13. participants with malignancy requiring active therapy (not including non-melanoma skin cancer). 14. recipients of allogeneic hematopoietic cell transplant or solid organ transplant. 15. history of who class iii or iv pulmonary hypertension. 16. severe thromboembolic disease, as defined by: administration of thrombolytic agents, insertion of vena cava filter, or pulmonary thrombectomy within one-week interval prior to screening. 17. participants may be excluded at the discretion of the pi or if it is deemed that allowing participation would represent an unacceptable medical or psychiatric risk.

1. active uncontrolled infection with a non-covid-19 agent. 2. diagnosis of ards that is not considered to be high-risk, as defined by pao2-to-fio2 ratio of ≥ 150 mm hg. 3. any irreversible disease or condition for which 6-month mortality is estimated to be greater than 50%. 4. end-stage liver disease with ascites unrelated to covid-19 (childs pugh score \> 12). 5. uncontrolled or significant cardiovascular disease, including but not limited to: (a) myocardial infarction, stroke, or transient ischemic attack within the past 30 days; (b) uncontrolled angina within the past 30 days; (c) any history of clinically significant arrhythmias such as ventricular tachycardia, ventricular fibrillation, or torsades de pointes; and (d) history of other clinically significant or uncontrolled heart disease, including: cardiomyopathy, congestive heart failure with new york heart association functional classification iii or iv, myocarditis, pericarditis, or significant pericardial effusion. 6. known chronic kidney disease of stage 4 or 5 severity or requiring hemodialysis. 7. covid-19-associated acute kidney injury requiring dialysis. 8. hiv, hepatitis b, or hepatitis c seropositive. 9. patients with baseline qtc interval prolongation, as defined by repeated demonstration of a qtc interval \>500 milliseconds. 10. patients on hydroxychloroquine (must discontinue at least 2-days before study entry). 11. pregnant or breastfeeding participants. 12. patients of childbearing age, or males who have a partner of childbearing potential, who are unwilling to practice contraception. effective forms of birth control, which must be continued through the entire on-study 6-month interval, include: abstinence; intrauterine device (iud); hormonal (birth control pills, injections, or implants); tubal ligation; or vasectomy. 13. participants with malignancy requiring active therapy (not including non-melanoma skin cancer). 14. recipients of allogeneic hematopoietic cell transplant or solid organ transplant. 15. history of who class iii or iv pulmonary hypertension. 16. severe thromboembolic disease, as defined by: administration of thrombolytic agents, insertion of vena cava filter, or pulmonary thrombectomy within one-week interval prior to screening. 17. participants may be excluded at the discretion of the pi or if it is deemed that allowing participation would represent an unacceptable medical or psychiatric risk.

active uncontrolled infection with a non-covid-19 agent. diagnosis of ards that is not considered to be high-risk, as defined by pao2-to-fio2 ratio of ≥ 150 mm hg. any irreversible disease or condition for which 6-month mortality is estimated to be greater than 50%. end-stage liver disease with ascites unrelated to covid-19 (childs pugh score > 12). uncontrolled or significant cardiovascular disease, including but not limited to: (a) myocardial infarction, stroke, or transient ischemic attack within the past 30 days; (b) uncontrolled angina within the past 30 days; (c) any history of clinically significant arrhythmias such as ventricular tachycardia, ventricular fibrillation, or torsades de pointes; and (d) history of other clinically significant or uncontrolled heart disease, including: cardiomyopathy, congestive heart failure with new york heart association functional classification iii or iv, myocarditis, pericarditis, or significant pericardial effusion. known chronic kidney disease of stage 4 or 5 severity or requiring hemodialysis. covid-19-associated acute kidney injury requiring dialysis. hiv, hepatitis b, or hepatitis c seropositive. patients with baseline qtc interval prolongation, as defined by repeated demonstration of a qtc interval >500 milliseconds. patients on hydroxychloroquine (must discontinue at least 2-days before study entry). pregnant or breastfeeding participants. patients of childbearing age, or males who have a partner of childbearing potential, who are unwilling to practice contraception. effective forms of birth control, which must be continued through the entire on-study 6-month interval, include: abstinence; intrauterine device (iud); hormonal (birth control pills, injections, or implants); tubal ligation; or vasectomy. participants with malignancy requiring active therapy (not including non-melanoma skin cancer). recipients of allogeneic hematopoietic cell transplant or solid organ transplant. history of who class iii or iv pulmonary hypertension. severe thromboembolic disease, as defined by: administration of thrombolytic agents, insertion of vena cava filter, or pulmonary thrombectomy within one-week interval prior to screening. participants may be excluded at the discretion of the pi or if it is deemed that allowing participation would represent an unacceptable medical or psychiatric risk.

active uncontrolled infection with a non-covid-19 agent. diagnosis of ards that is not considered to be high-risk, as defined by pao2-to-fio2 ratio of ≥ 150 mm hg. any irreversible disease or condition for which 6-month mortality is estimated to be greater than 50%. end-stage liver disease with ascites unrelated to covid-19 (childs pugh score > 12). uncontrolled or significant cardiovascular disease, including but not limited to: (a) myocardial infarction, stroke, or transient ischemic attack within the past 30 days; (b) uncontrolled angina within the past 30 days; (c) any history of clinically significant arrhythmias such as ventricular tachycardia, ventricular fibrillation, or torsades de pointes; and (d) history of other clinically significant or uncontrolled heart disease, including: cardiomyopathy, congestive heart failure with new york heart association functional classification iii or iv, myocarditis, pericarditis, or significant pericardial effusion. known chronic kidney disease of stage 4 or 5 severity or requiring hemodialysis. covid-19-associated acute kidney injury requiring dialysis. hiv, hepatitis b, or hepatitis c seropositive. patients with baseline qtc interval prolongation, as defined by repeated demonstration of a qtc interval >500 milliseconds. patients on hydroxychloroquine (must discontinue at least 2-days before study entry). pregnant or breastfeeding participants. patients of childbearing age, or males who have a partner of childbearing potential, who are unwilling to practice contraception. effective forms of birth control, which must be continued through the entire on-study 6-month interval, include: abstinence; intrauterine device (iud); hormonal (birth control pills, injections, or implants); tubal ligation; or vasectomy. participants with malignancy requiring active therapy (not including non-melanoma skin cancer). recipients of allogeneic hematopoietic cell transplant or solid organ transplant. history of who class iii or iv pulmonary hypertension. severe thromboembolic disease, as defined by: administration of thrombolytic agents, insertion of vena cava filter, or pulmonary thrombectomy within one-week interval prior to screening. participants may be excluded at the discretion of the pi or if it is deemed that allowing participation would represent an unacceptable medical or psychiatric risk.

1. active uncontrolled infection with a non-covid-19 agent. 2. diagnosis of ards that is not considered to be high-risk, as defined by pao2-to-fio2 ratio of ≥ 150 mm hg. 3. any irreversible disease or condition for which 6-month mortality is estimated to be greater than 50%. 4. end-stage liver disease with ascites unrelated to covid-19 (childs pugh score > 12). 5. uncontrolled or significant cardiovascular disease, including but not limited to: (a) myocardial infarction, stroke, or transient ischemic attack within the past 30 days; (b) uncontrolled angina within the past 30 days; (c) any history of clinically significant arrhythmias such as ventricular tachycardia, ventricular fibrillation, or torsades de pointes; and (d) history of other clinically significant or uncontrolled heart disease, including: cardiomyopathy, congestive heart failure with new york heart association functional classification iii or iv, myocarditis, pericarditis, or significant pericardial effusion. 6. known chronic kidney disease of stage 4 or 5 severity or requiring hemodialysis. 7. covid-19-associated acute kidney injury requiring dialysis. 8. hiv, hepatitis b, or hepatitis c seropositive. 9. patients with baseline qtc interval prolongation, as defined by repeated demonstration of a qtc interval >500 milliseconds. 10. patients on hydroxychloroquine (must discontinue at least 2-days before study entry). 11. pregnant or breastfeeding participants. 12. patients of childbearing age, or males who have a partner of childbearing potential, who are unwilling to practice contraception. effective forms of birth control, which must be continued through the entire on-study 6-month interval, include: abstinence; intrauterine device (iud); hormonal (birth control pills, injections, or implants); tubal ligation; or vasectomy. 13. participants with malignancy requiring active therapy (not including non-melanoma skin cancer). 14. recipients of allogeneic hematopoietic cell transplant or solid organ transplant. 15. history of who class iii or iv pulmonary hypertension. 16. severe thromboembolic disease, as defined by: administration of thrombolytic agents, insertion of vena cava filter, or pulmonary thrombectomy within one-week interval prior to screening. 17. participants may be excluded at the discretion of the pi or if it is deemed that allowing participation would represent an unacceptable medical or psychiatric risk.

1. active uncontrolled infection with a non-covid-19 agent. 2. diagnosis of ards that is not considered to be high-risk, as defined by pao2-to-fio2 ratio of ≥ 150 mm hg. 3. any irreversible disease or condition for which 6-month mortality is estimated to be greater than 50%. 4. end-stage liver disease with ascites unrelated to covid-19 (childs pugh score > 12). 5. uncontrolled or significant cardiovascular disease, including but not limited to: (a) myocardial infarction, stroke, or transient ischemic attack within the past 30 days; (b) uncontrolled angina within the past 30 days; (c) any history of clinically significant arrhythmias such as ventricular tachycardia, ventricular fibrillation, or torsades de pointes; and (d) history of other clinically significant or uncontrolled heart disease, including: cardiomyopathy, congestive heart failure with new york heart association functional classification iii or iv, myocarditis, pericarditis, or significant pericardial effusion. 6. known chronic kidney disease of stage 4 or 5 severity or requiring hemodialysis. 7. covid-19-associated acute kidney injury requiring dialysis. 8. hiv, hepatitis b, or hepatitis c seropositive. 9. patients with baseline qtc interval prolongation, as defined by repeated demonstration of a qtc interval >500 milliseconds. 10. patients on hydroxychloroquine (must discontinue at least 2-days before study entry). 11. pregnant or breastfeeding participants. 12. patients of childbearing age, or males who have a partner of childbearing potential, who are unwilling to practice contraception. effective forms of birth control, which must be continued through the entire on-study 6-month interval, include: abstinence; intrauterine device (iud); hormonal (birth control pills, injections, or implants); tubal ligation; or vasectomy. 13. participants with malignancy requiring active therapy (not including non-melanoma skin cancer). 14. recipients of allogeneic hematopoietic cell transplant or solid organ transplant. 15. history of who class iii or iv pulmonary hypertension. 16. severe thromboembolic disease, as defined by: administration of thrombolytic agents, insertion of vena cava filter, or pulmonary thrombectomy within one-week interval prior to screening. 17. participants may be excluded at the discretion of the pi or if it is deemed that allowing participation would represent an unacceptable medical or psychiatric risk.

1. active uncontrolled infection with a non-covid-19 agent. 2. participants with severe ards (riviello et al., 2016), as determined by institutional icu staff and as defined by berlin criteria [pao2/fio2 ratio <100 mmhg not eligible] or modified-berlin criteria (using spo2/fio2 ratio). 3. any irreversible disease or condition for which 6-month mortality is estimated to be greater than 50%. 4. end-stage liver disease with ascites unrelated to covid-19 (childs pugh score > 12). 5. uncontrolled or significant cardiovascular disease, including but not limited to: (a) myocardial infarction, stroke, or transient ischemic attack within the past 30 days; (b) uncontrolled angina within the past 30 days; (c) any history of clinically significant arrhythmias such as ventricular tachycardia, ventricular fibrillation, or torsades de pointes; and (d) history of other clinically significant or uncontrolled heart disease, including: cardiomyopathy, congestive heart failure with new york heart association functional classification iii or iv, myocarditis, pericarditis, or significant pericardial effusion. 6. known chronic kidney disease of stage 4 or 5 severity or requiring hemodialysis. 7. covid-19-associated acute kidney injury requiring dialysis. 8. hiv, hepatitis b, or hepatitis c seropositive. 9. patients with baseline qt interval prolongation, as defined by repeated demonstration of a qtc interval >450 milliseconds. 10. patients on hydroxychloroquine (must discontinue at least 2-days before study entry). 11. pregnant or breastfeeding participants. 12. patients of childbearing age, or males who have a partner of childbearing potential, who are unwilling to practice contraception. effective forms of birth control, which must be continued through the entire on-study 6-month interval, include: abstinence; intrauterine device (iud); hormonal (birth control pills, injections, or implants); tubal ligation; or vasectomy. 13. participants with malignancy requiring active therapy (not including non-melanoma skin cancer). 14. recipients of allogeneic hematopoietic cell transplant or solid organ transplant. 15. history of who class iii or iv pulmonary hypertension. 16. severe thromboembolic disease, as defined by: administration of thrombolytic agents, insertion of vena cava filter, or pulmonary thrombectomy within one-week interval prior to screening. 17. participants may be excluded at the discretion of the pi or if it is deemed that allowing participation would represent an unacceptable medical or psychiatric risk.

1. active uncontrolled infection with a non-covid-19 agent. 2. participants with severe ards (riviello et al., 2016), as determined by institutional icu staff and as defined by berlin criteria [pao2/fio2 ratio <100 mmhg not eligible] or modified-berlin criteria (using spo2/fio2 ratio). 3. any irreversible disease or condition for which 6-month mortality is estimated to be greater than 50%. 4. end-stage liver disease with ascites unrelated to covid-19 (childs pugh score > 12). 5. uncontrolled or significant cardiovascular disease, including but not limited to: (a) myocardial infarction, stroke, or transient ischemic attack within the past 30 days; (b) uncontrolled angina within the past 30 days; (c) any history of clinically significant arrhythmias such as ventricular tachycardia, ventricular fibrillation, or torsades de pointes; and (d) history of other clinically significant or uncontrolled heart disease, including: cardiomyopathy, congestive heart failure with new york heart association functional classification iii or iv, myocarditis, pericarditis, or significant pericardial effusion. 6. known chronic kidney disease of stage 4 or 5 severity or requiring hemodialysis. 7. covid-19-associated acute kidney injury requiring dialysis. 8. hiv, hepatitis b, or hepatitis c seropositive. 9. patients with baseline qt interval prolongation, as defined by repeated demonstration of a qtc interval >450 milliseconds. 10. patients on hydroxychloroquine (must discontinue at least 2-days before study entry). 11. pregnant or breastfeeding participants. 12. patients of childbearing age, or males who have a partner of childbearing potential, who are unwilling to practice contraception. effective forms of birth control, which must be continued through the entire on-study 6-month interval, include: abstinence; intrauterine device (iud); hormonal (birth control pills, injections, or implants); tubal ligation; or vasectomy. 13. participants with malignancy requiring active therapy (not including non-melanoma skin cancer). 14. recipients of allogeneic hematopoietic cell transplant or solid organ transplant. 15. history of who class iii or iv pulmonary hypertension. 16. severe thromboembolic disease, as defined by: administration of thrombolytic agents, insertion of vena cava filter, or pulmonary thrombectomy within one-week interval prior to screening. 17. participants may be excluded at the discretion of the pi or if it is deemed that allowing participation would represent an unacceptable medical or psychiatric risk.

1. active uncontrolled infection with a non-covid-19 agent. 2. participants with severe ards (riviello et al., 2016), as determined by institutional icu staff and as defined by berlin criteria [pao2/fio2 ratio <100 mmhg not eligible] or modified-berlin criteria (using spo2/fio2 ratio). 3. any irreversible disease or condition for which 6-month mortality is estimated to be greater than 50%. 4. end-stage liver disease with ascites unrelated to covid-19 (childs pugh score > 12). 5. uncontrolled or significant cardiovascular disease, including but not limited to: (a) myocardial infarction, stroke, or transient ischemic attack within the past 30 days; (b) uncontrolled angina within the past 30 days; (c) any history of clinically significant arrhythmias such as ventricular tachycardia, ventricular fibrillation, or torsades de pointes; and (d) history of other clinically significant or uncontrolled heart disease, including: cardiomyopathy, congestive heart failure with new york heart association functional classification iii or iv, myocarditis, pericarditis, or significant pericardial effusion. 6. known chronic kidney disease of stage 4 or 5 severity or requiring hemodialysis. 7. covid-19-associated acute kidney injury requiring dialysis. 8. hiv, hepatitis b, or hepatitis c seropositive. 9. patients with baseline qt interval prolongation, as defined by repeated demonstration of a qtc interval >450 milliseconds. 10. patients on hydroxychloroquine (must discontinue at least 2-days before study entry). 11. pregnant or breastfeeding participants. 12. patients of childbearing age, or males who have a partner of childbearing potential, who are unwilling to practice contraception. effective forms of birth control, which must be continued through the entire on-study 6-month interval, include: abstinence; intrauterine device (iud); hormonal (birth control pills, injections, or implants); tubal ligation; or vasectomy. 13. participants with malignancy requiring active therapy (not including non-melanoma skin cancer). 14. recipients of allogeneic hematopoietic cell transplant or solid organ transplant. 15. history of who class iii or iv pulmonary hypertension. 16. documented deep vein thrombosis or pulmonary embolism within past 3 months. 17. participants may be excluded at the discretion of the pi or if it is deemed that allowing participation would represent an unacceptable medical or psychiatric risk.

1. active uncontrolled infection with a non-covid-19 agent. 2. participants with severe ards (riviello et al., 2016), as determined by institutional icu staff and as defined by berlin criteria [pao2/fio2 ratio <100 mmhg not eligible] or modified-berlin criteria (using spo2/fio2 ratio). 3. any irreversible disease or condition for which 6-month mortality is estimated to be greater than 50%. 4. end-stage liver disease with ascites unrelated to covid-19 (childs pugh score > 12). 5. uncontrolled or significant cardiovascular disease, including but not limited to: (a) myocardial infarction, stroke, or transient ischemic attack within the past 30 days; (b) uncontrolled angina within the past 30 days; (c) any history of clinically significant arrhythmias such as ventricular tachycardia, ventricular fibrillation, or torsades de pointes; and (d) history of other clinically significant or uncontrolled heart disease, including: cardiomyopathy, congestive heart failure with new york heart association functional classification iii or iv, myocarditis, pericarditis, or significant pericardial effusion. 6. known chronic kidney disease of stage 4 or 5 severity or requiring hemodialysis. 7. covid-19-associated acute kidney injury requiring dialysis. 8. hiv, hepatitis b, or hepatitis c seropositive. 9. patients with baseline qt interval prolongation, as defined by repeated demonstration of a qtc interval >450 milliseconds. 10. patients on hydroxychloroquine (must discontinue at least 2-days before study entry). 11. pregnant or breastfeeding participants. 12. patients of childbearing age, or males who have a partner of childbearing potential, who are unwilling to practice contraception. effective forms of birth control, which must be continued through the entire on-study 6-month interval, include: abstinence; intrauterine device (iud); hormonal (birth control pills, injections, or implants); tubal ligation; or vasectomy. 13. participants with malignancy requiring active therapy (not including non-melanoma skin cancer). 14. recipients of allogeneic hematopoietic cell transplant or solid organ transplant. 15. history of who class iii or iv pulmonary hypertension. 16. documented deep vein thrombosis or pulmonary embolism within past 3 months. 17. participants may be excluded at the discretion of the pi or if it is deemed that allowing participation would represent an unacceptable medical or psychiatric risk.