Cohort 1 (Part 1 and Part 2): 1. Hospitalized COVID-19 patients ≥18 years without hypoxemia who are either not receiving any oxygen therapy OR are receiving supplemental oxygen via mask or nasal prongs (namely, clinical status score 4 or 5 on an 8-point ordinal scale) 2. Hospitalized COVID-19 patients age ≥65 years AND type 2 diabetes or hypertension, OR 3. Hospitalized COVID-19 patients ≥18 years AND abnormal blood tests with CRP >50 mg/L PLUS at least 1 of the following biomarkers: 1. D-dimer >1,000 ng/mL 2. Ferritin >500 µg/L 3. High sensitivity cardiac troponin >2 × ULN 4. LDH >245 U/L Cohort 2 (Part 1 and Part 2): 4. Hospitalized COVID-19 patients with hypoxemia who are either receiving NIPPV OR high-flow oxygen (namely, clinical status score 3 on an 8-point ordinal scale). 5. Bilateral opacities on a chest x-ray OR chest CT scan. Cohort 1 and Cohort 2 (Parts 1 and 2) 6. Male and non-pregnant, non-lactating female patients with SARS-CoV-2 infection that is documented by a Food and Drug Administration (FDA)-authorized diagnostic reverse transcription polymerase chain reaction test at/or within 4 days of Screening 7. ≥18 years of age 8. Body weight ≥40 kg at Screening 9. History of COVID-19 within the last 2 weeks prior to study enrollment 10. The patient OR a legally authorized representative has provided written informed consent 11. Females of childbearing potential must have a negative beta human chorionic gonadotropin pregnancy test at Screening 12. Females of childbearing potential must agree to be abstinent or else use a medically acceptable form of contraception from the Screening period through Day 28. Medically acceptable forms of contraception including implants, injectables, combined oral contraceptives, some intrauterine devices, sexual abstinence or vasectomy, and double-barrier method [condom and occlusive cap (diaphragm or cervical/vault caps)] with spermicidal foam/gel/film/suppository

Cohort 1 1. Receiving high-flow oxygen OR NIPPV. Cohort 1 and Cohort 2 2. ARDS by Berlin definition (Appendix 16.2) 3. On extracorporeal membrane oxygenation 4. Uncontrolled hypertension (systolic blood pressure [BP] >150 mmHg and/or diastolic BP >100 mmHg), unstable angina, congestive heart failure of New York Heart Association Classification Class III or IV (i.e., Class III: marked limitation in activity due to symptoms, even during less-than-ordinary activity, e.g., walking short distances [20 100 m], comfortable only at rest; Class IV: severe limitations, experiences symptoms even while at rest, mostly bedbound patients), serious cardiac arrhythmia requiring treatment (exceptions: atrial fibrillation, paroxysmal supraventricular tachycardia), history of myocardial infarction within 12 months prior to enrollment 5. Subjects with a history of congenital long QT syndrome or of Torsades de pointes; subjects with bradycardia (<60 bpm), heart block (excluding 1st degree block, being PR interval prolongation only); subjects with any of the following findings on electrocardiogram (ECG): QTc interval >470 msec in women OR >450 msec in men; subjects requiring any drugs known to prolong the QTc interval, including antiarrhythmic medications 6. Shock or hypotension requiring vasoactive peptides, such as dopamine, norepinephrine, epinephrine, or dobutamine 7. Renal function impairment with creatinine ≥2 mg/dL 8. Liver function impairment with total bilirubin ≥2 mg/dL 9. Platelet count <50,000/µL 10. Multi-organ failure 11. History of an allergic reaction or hypersensitivity to the study drug or any component of the study drug formulation 12. Use of systemic corticosteroids, nonsteroidal anti-inflammatory drugs, antibiotics, and antiviral drugs that are not part of the standard of care 13. Presence of any uncontrolled concomitant illness (e.g., bacterial sepsis or invasive fungal infection), or other serious illness and medical conditions, or other medical history, including laboratory results, which, in the Investigator's opinion, would be likely to interfere with their participation in the study 14. Pregnancy or breast-feeding (for women)