Safety, Tolerability and Pharmacokinetics of Inhaled Nanoparticle Formulation of Remdesivir (GS-5734) and NA-831

INCLUSION CRITERIA: 1. Healthy adult volunteers, aged 21 to 50 years old, men or women. 2. Subjects negative for human immunodeficiency virus (HIV antibody screen), Hepatitis B virus surface Antigen (HBsAg) and Hepatitis C virus (HCV antibody screen). 3. Subjects who are willing to comply with the requirements of the study protocol, attend scheduled visits and make themselves available for the duration of the study with access to a consistent means of telephone contact. 4. Subjects who give written informed consent approved by the Internal Review Board governing the site. 5. Satisfactory baseline medical assessment as assessed by physical examination and a stable health status. Normal laboratory values must be within normal range of the assessing site or show minor variations that are deemed not clinically significant as judged by the Investigator and acceptable for study entry. 6. Accessible vein in the forearm for blood collection. 7. Female subjects of childbearing potential may be enrolled in the study if they have negative urine pregnancy tests on the day of screening and day of admission. 8. Female subjects of non-childbearing potential due to surgical sterilization (hysterectomy or bilateral oophorectomy or tubal ligation) or menopause. 9. Both male (if he has a partner of childbearing potential) and female subjects (of childbearing potential) must agree to use adequate and reliable contraceptive measures (e.g. spermicides, condoms, contraceptive pills, etc.) or practice abstinence throughout the duration of the study (up to 30 days post-dosing). EXCLUSION CRITERIA: 1. Subject previously diagnosed with COVID-19 or had been issued with a quarantine order by the Center of Disease Control (CDC). 2. Presence of acute infection in the preceding 14 days, or presence of a temperature ≥ 100.0 ˚F (oral or tympanic temperature assessment), or acute symptoms of any severity on the scheduled date of admission. 3. History of severe drug and / or food allergies and / or known allergies to the trial product or its components. 4. Female subject who is pregnant or breast-feeding. 5. History or presence of cardiovascular, respiratory, hepatic, renal, gastrointestinal, , or immunosuppressive disorders. 6. Any neurological disease or history of significant neurological disorder (e.g. meningitis, seizures, multiple sclerosis, vasculitis, migraines, Guillain-Barré syndrome \[genetic/congenital or acquired\]). 7. Evidence of clinically significant anemia (HB \< 10 g/dL) or any other significant active hematological disease, or having donated \> 450 mL of blood within the past three (3) months. 8. Participation or planned participation in a study involving the administration of an investigational compound within the past four (4) months or during this study period. 9. Receipt of immunoglobulins and/or any blood products within nine (9) months of study enrolment or planned administration of any of these products during the study period. 10. Evidence of Hepatitis B or C or HIV by laboratory testing. 11. A positive test result for drugs of abuse (except a positive test result associated with prescription medication that has been reviewed and approved by the investigator) or alcohol at screening. 12. Administration of any licensed vaccine within 30 days before the first study vaccine dose. 13. Both male (if he has a partner of childbearing potential) and female subjects (of childbearing potential) who are unwilling to use adequate contraception or practice abstinence throughout the duration of the study (up to 84 days post-dosing). 14. Any condition that, in the opinion of the Investigator, would complicate or compromise the study or well-being of the subject. \-