Inclusion Criteria:

• At least 18 years of age at Screening.
• Confirmed SARS-CoV-2 viral infection by polymerase chain reaction (PCR) at Screening and Day 0.
• Has advanced COVID-19 with a score of 4 or 5 on the NIAID 8-point ordinal scale at Screening and Day 0.
• Off antiviral medications for at least 24 hours prior to first dose of study drug (active or placebo).
• Fever > 38.0ºC but < 39.2ºC.
• Able to sign the informed consent form (ICF).
• Women of childbearing potential (WCBP) must have a negative serum pregnancy test at Screening and a negative urine pregnancy test at baseline (Day 0).
• WCBP must agree to abstain from sex or use an adequate method of contraception* from the time of informed consent through the final Day 37 evaluations.
• Males must abstain from sex with WCBP or use an adequate method of contraception* from the time of informed consent through the final Day 37 evaluations.

*Adequate contraceptive methods include those with a low failure rate; i.e., less than 1% per year, when used consistently and correctly, such as abstinence from sexual intercourse, and some double barrier methods (condom with spermicide) in conjunction with use by the partner of an intrauterine device, diaphragm with spermicide, oral contraceptives, birth control patch or vaginal ring, or injectable or implanted contraceptives. Abstinence is acceptable only as true abstinence: when this is in line with the preferred and usual lifestyle of the subject. Periodic abstinence (e.g., calendar, ovulation, symptothermal, post-ovulation methods) and withdrawal are not acceptable methods of contraception.

A woman that is postmenopausal (≥ 2 years since last menstrual period) or permanently sterilized (e.g., tubal occlusion, hysterectomy, bilateral salpingectomy) is not considered a WCBP.

Exclusion Criteria:

• In critical condition or has acute respiratory distress syndrome (ARDS).
• On invasive mechanical ventilation or extracorporeal membrane oxygenation (ECMO).
• Bacterial or fungal infection, except for mild cutaneous infection or sinus infection. Asymptomatic bacteriuria or airway colonization of bacteria is not excluded.
• Pregnant or lactating.
• Any condition which, in the opinion of the Investigator, places the subject at unacceptable risk if he/she were to participate in the study.
• Clinically relevant serious co-morbid medical conditions including, but not limited to, unstable angina, symptomatic congestive heart failure, uncontrolled hypertension, uncontrolled cardiac arrhythmias, clinical exacerbations of chronic obstructive pulmonary disease (COPD), active central nervous system (CNS) disease uncontrolled by standard of care, known positive status for human immunodeficiency virus (HIV), active hepatitis B or C, cirrhosis, or psychiatric illness/social situations that would limit compliance with study requirements.
• Treatment with another investigational drug within 30 days or 5 half-lives of drug prior to Screening, whichever is longer.
• Known hypersensitivity to the inactive ingredients of the study drug (active or placebo).