1 Participation in any other clinical trial of an experimental treatment for COVID-19 (remdesivir <br/ > use is permitted). <br/ > 2 Significant pre existing organ dysfunction prior to randomization <br/ > -Lung: Receiving supplemental home oxygen therapy at baseline for pre-existing medical condition (other than COVID-19), as documented in medical record. <br/ > -Heart: Pre-existing congestive heart failure defined as an ejection fraction <20% as documented in the medical record. clinically significant ventricular arrhythmias (ventricular tachycardia, ventricular fibrillation), unstable angina, myocardial infarction (past 3 months), heart and coronary vessel surgery (past 3 months), significant valvular heart disease, uncontrolled arterial hypertension with systolic blood pressure >180 mm Hg and diastolic blood pressure >110 mm Hg. <br/ > -Renal: End-stage renal disease requiring renal replacement therapy or eGFR <30 mL/min <br/ > -Liver: Severe chronic liver disease defined as Child Pugh Class C <br/ > -Hematologic: Baseline platelet count <50,000/mm3 <br/ > 3 Concurrent treatment or prior use of drugs with actual or possible direct acting immunomodulatory activity against ARDS in COVID-19 is prohibited including JAK1/JAK2 inhibitor ruxolitinib, baricitinib and tofacitinib. However, IL-6 inhibitors such as tocilizumab, sarilumab are allowed if given >72 hours prior to first study dose. Corticosteroids are permitted throughout the study. <br/ > 4 History of splenectomy or splenomegaly (spleen weighing >750 g) <br/ > 5 Body mass index of >45 kg/m2 at screening <br/ > 6 Underlying malignancy, or other condition, with estimated life expectancy of less than two months <br/ > 7 Known family history of long QT syndrome (Torsades de Pointes) or currently taking medication that prolongs QT interval <br/ > 8 Currently taking immunomodulating biologics (e.g., interferons, interleukin). <br/ > 9 Extracorporeal membrane oxygenation (ECMO) <br/ > 10 Use of two or more vasopressors <br/ > 11 Female subjects who are pregnant or breastfeeding or planning to breastfeed at any time through 90 days after last dose of IP. <br/ > 12 Received a live attenuated vaccine within 30 days prior to enrollment. <br/ > 13 Positive test for Hepatitis B surface antigen (HBsAg), Hepatitis C antibody, human immunodeficiency virus (HIV) antibody or Active tuberculosis or a history of inadequately treated tuberculosis. <br/ > 14 Ongoing immunosuppression: solid organ transplant recipients <br/ > 15 Has used an investigational drug within 30 days prior to Screening. <br/ > 16 History of hypersensitivity to MRG-001 (plerixafor [AMD3100, 24 mg/mL]) and tacrolimus [FK506, 0.5 mg/mL]) or any of the excipients or to medicinal products with similar chemical structure <br/ > 17 Current treatment with an anti-viral medication for COVID-19 (e.g. hydroxychloroquine, lopinavir/ritonavir), other than remdesivir <br/ > 18 Unable to understand the protocol requirements, instructions and study related restrictions, the nature, scope and possible consequences of the clinical study <br/ > 19 Unlikely to comply with the protocol requirements, instructions and study related restrictions, e.g., uncooperative attitude, inability to return for follow-up visits and improbability of completing the clinical study. <br/ > 20 Previously been enrolled in this clinical study. <br/ > 21 Vulnerable subjects defined as individuals whose willingness to volunteer in a cl

1 Participation in any other clinical trial of an experimental treatment for COVID-19 (remdesivir <br/ > use is permitted). <br/ > 2 Significant pre existing organ dysfunction prior to randomization <br/ > -Lung: Receiving supplemental home oxygen therapy at baseline for pre-existing medical condition (other than COVID-19), as documented in medical record. <br/ > -Heart: Pre-existing congestive heart failure defined as an ejection fraction <20% as documented in the medical record. clinically significant ventricular arrhythmias (ventricular tachycardia, ventricular fibrillation), unstable angina, myocardial infarction (past 3 months), heart and coronary vessel surgery (past 3 months), significant valvular heart disease, uncontrolled arterial hypertension with systolic blood pressure >180 mm Hg and diastolic blood pressure >110 mm Hg. <br/ > -Renal: End-stage renal disease requiring renal replacement therapy or eGFR <30 mL/min <br/ > -Liver: Severe chronic liver disease defined as Child Pugh Class C <br/ > -Hematologic: Baseline platelet count <50,000/mm3 <br/ > 3 Concurrent treatment or prior use of drugs with actual or possible direct acting immunomodulatory activity against ARDS in COVID-19 is prohibited including JAK1/JAK2 inhibitor ruxolitinib, baricitinib and tofacitinib. However, IL-6 inhibitors such as tocilizumab, sarilumab are allowed if given >72 hours prior to first study dose. Corticosteroids are permitted throughout the study. <br/ > 4 History of splenectomy or splenomegaly (spleen weighing >750 g) <br/ > 5 Body mass index of >45 kg/m2 at screening <br/ > 6 Underlying malignancy, or other condition, with estimated life expectancy of less than two months <br/ > 7 Known family history of long QT syndrome (Torsades de Pointes) or currently taking medication that prolongs QT interval <br/ > 8 Currently taking immunomodulating biologics (e.g., interferons, interleukin). <br/ > 9 Extracorporeal membrane oxygenation (ECMO) <br/ > 10 Use of two or more vasopressors <br/ > 11 Female subjects who are pregnant or breastfeeding or planning to breastfeed at any time through 90 days after last dose of IP. <br/ > 12 Received a live attenuated vaccine within 30 days prior to enrollment. <br/ > 13 Positive test for Hepatitis B surface antigen (HBsAg), Hepatitis C antibody, human immunodeficiency virus (HIV) antibody or Active tuberculosis or a history of inadequately treated tuberculosis. <br/ > 14 Ongoing immunosuppression: solid organ transplant recipients <br/ > 15 Has used an investigational drug within 30 days prior to Screening. <br/ > 16 History of hypersensitivity to MRG-001 (plerixafor [AMD3100, 24 mg/mL]) and tacrolimus [FK506, 0.5 mg/mL]) or any of the excipients or to medicinal products with similar chemical structure <br/ > 17 Current treatment with an anti-viral medication for COVID-19 (e.g. hydroxychloroquine, lopinavir/ritonavir), other than remdesivir <br/ > 18 Unable to understand the protocol requirements, instructions and study related restrictions, the nature, scope and possible consequences of the clinical study <br/ > 19 Unlikely to comply with the protocol requirements, instructions and study related restrictions, e.g., uncooperative attitude, inability to return for follow-up visits and improbability of completing the clinical study. <br/ > 20 Previously been enrolled in this clinical study. <br/ > 21 Vulnerable subjects defined as individuals whose willingness to volunteer in a cl