Inclusion Criteria:

1. Willing and able to provide informed consent themselves or through their legally authorized representative. 2. Male or female patients, of any race or ethnicity, 18 to 80 years of age, inclusive, on the day of informed consent. Racial and ethnic minorities should be included in the study population to the greatest extent possible. 3. Laboratory-confirmed SARS-CoV-2 infection as determined within 14 days of randomization by real time RT-PCR or other commercial or public health assay authorized by FDA or other applicable health authority . 4. Onset of COVID-19 symptoms within 14 days prior to randomization. 5. Have at least one of the following symptoms at screening: fever, cough, shortness of breath, myalgia, ageusia, anosmia, fatigue, or weakness. 6. Hospitalized with COVID-19 disease (WHO COVID-19 Clinical Improvement Ordinal Scale score of 3 [hospitalized, no oxygen therapy], 4 [hospitalized, oxygen by mask or nasal prongs], or 5 [high-flow oxygen or non-invasive mechanical ventilation]) 7. Patient is aware of the investigational nature of this study and willing to comply with protocol treatments, blood tests, and other evaluations listed in the informed consent form.

Exclusion Criteria:

1. Females who are pregnant (negative pregnancy test required for all women of childbearing potential at screening) or breastfeeding. 2. Male patients and women of childbearing potential (women who are not surgically sterile or postmenopausal defined as postmenopausal for >12 months) who are not using at least one protocol specified method of contraception. 3. COVID-19 disease as defined by the WHO COVID-19 Clinical Improvement Ordinal Scale, scores of 6 (intubation and mechanical ventilation) or 7 (ventilation + additional organ support

• - pressors, renal replacement therapy, extracorporeal membrane oxygenation).

4. Expected survival less than 72 hours. 5. Treatment with other drugs thought to possibly have activity against SARS CoV 2 infection within 7 days or within 5 half-lives, whichever is longer, prior to enrollment or concurrently. Drugs that have received FDA emergency use authorization or COVID-19 approval are allowed. 6. Treatment with immunosuppressants, combination of 2 or more RAS blockers, UGT inhibitors and inducers, herbal/natural supplements, potassium-sparing diuretic, and radiographic contrast agent prior to enrollment or concurrently. 7. History of abuse of drugs or alcohol that could interfere with adherence to study requirements as judged by the investigator. 8. Use of any other concurrent investigational drugs while participating in the present study. 9. Patient requires frequent or prolonged use of systemic corticosteroids (≥20 mg of prednisone/day or equivalent for >4 weeks) or other immunosuppressive drugs (eg, for organ transplantation or autoimmune conditions). 10. Known renal disease with an estimated glomerular filtration rate <30 mL/min. 11. Patients with clinically apparent liver disease (eg, jaundice, cholestasis, hepatic synthetic impairment, or active hepatitis) or moderate or severe hepatic impairment as determined by Child-Pugh score Class B or C. 12. Alanine aminotransaminase (ALT) or aspartate aminotransaminase (AST) >3 × upper limit of normal (ULN) AND total bilirubin levels >2 × ULN OR ALT or AST >5 × ULN. 13. Total bilirubin >1.5 × ULN, unless the patient has known Gilbert's syndrome. 14. Hemoglobin <9 g/dL for females or <11 g/dL for males. 15. Absolute neutrophil count <1500/mm3. 16. Thrombocytopenia (platelets count <100 × 109/L). 17. Inability to swallow oral medications or a gastrointestinal disorder with diarrhea (eg, Crohn's disease) or malabsorption at screening. 18. Any other clinically significant medical condition or laboratory abnormality that, in the opinion of the investigator, would jeopardize the safety of the patient or potentially impact patient compliance or the safety/efficacy observations in the study. 19. History of an allergic reaction or hypersensitivity to the study drug or any component of the study drug formulation.

APX-115 is a potent small molecule inhibitor of NADPH-oxidase (Nox) isozymes being developed by Aptabio Therapeutics Inc. The Nox enzymes represent a family of 7 membrane enzymes (Nox1, Nox2, Nox3, Nox4, Nox5, Duox1, and Duox2) which catalyze NADPH-dependent generation of superoxide and secondary reactive oxygen species (ROS). ROS are often generated during virus infection, thus promoting apoptosis, lung injury, and inflammation/allergy.

Arms

Experimental: APX-115

Oral administration of APX-115 100mg, daily for 14 days

Placebo Comparator: Placebo

Oral administration of Placebo, daily for 14 days

Interventions

Drug: - APX-115

Oral administration of APX-115 100 mg capsule once daily for 14 days

Drug: - Placebo

Oral administration of placebo capsule once daily for 14 days