This is a Phase 1 (healthy adult volunteers), 2-part, double-blind, randomized, placebo controlled trial to evaluate the safety and pharmacokinetic (PK) profiles of escalating single doses of Niclosamide Inhalation Powder versus placebo (SAD part) and escalating multiple doses of Niclosamide Inhalation Powder versus placebo (MAD part). SAD part will be initiated first and includes a sentinel design. MAD part will not utilize a sentinel design unless the data monitoring committee requests the addition of sentinels. The MAD part will be initiated once the lowest doses from SAD part are deemed safe.

This is a Phase 1, randomized, 2 part double-blind, placebo-controlled trial to evaluate the safety and PK profiles of Niclosamide Inhalation Powder in a SAD/MAD study design.

Part A is a double-blinded, placebo-controlled, randomized, dose- ranging single dose study evaluating four different dose levels.

On Day 1 of each group, two selected subjects (sentinel subjects) will receive either Niclosamide Inhalation Powder or a matching placebo. Blood samples and safety measurements including Adverse Events (AEs) will be collected over 24 hour period following the drug administration. The safety results to be evaluated include AEs, concomitant medications, out of specification clinical laboratory results, vital signs, Electrocardiograms (ECGs), visual examinations, pulmonary function tests, pulse oximetry results and any new findings on physical examinations. If the administration is safe as deemed by Principal Investigator & Medical Monitor, the remaining six subjects will be dosed (5 dosed with Niclosamide Inhalation Powder and 1 dosed with matching placebo), with identical safety and PK procedures performed after minimum of 2 days interval. A minimum of 3 days will separate each dose escalation, with the remaining dose groups dosed in a sentinel fashion.

Part B is a double-blinded, placebo-controlled, randomized, dose- ranging multi-dose study evaluating two different dose levels. Dose level 1 of Part B can begin once the data monitoring committee reviews the safety data and indicates safety is present. Niclosamide Inhalation Powder will be administered twice daily (BID) × 9 doses. Blood samples for safety and PK will be collected throughout confinement, which is 7 days.

Inclusion Criteria:

1. Agree to use acceptable contraception or is not able to bear children.
2. Body mass index (BMI) within ≥ 18.0 kg/m2 and ≤ 30.0 kg/m2 at Screening (body weight of at least 50.0 kg and no more than120 kg at Screening).
3. Non-smoker or ex-smoker (stopped using nicotine products for at least 12 months prior to the first study drug administration and throughout the study).
4. Have no clinically significant diseases, including asthma, captured in the medical history or on the physical examination, visual examination, clinical laboratory assessments, and/or ECG.
5. A forced expiratory volume during the first second (FEV1) ≥ 80% at Screening and Check-in.

Exclusion Criteria

1. Female who is lactating, is pregnant or planning to become pregnant according to the pregnancy test at Screening or prior to the first study drug administration.

2. Is mentally or legally incapacitated or unable to provide informed consent.

3. History or presence of alcoholism or drug abuse within the past 2 years prior to the first study drug administration.

4. History or presence of hypersensitivity or idiosyncratic reaction to niclosamide or any portion of the placebo.

5. Has had surgery or any medical condition within 6 months prior to first study drug administration which may affect the absorption, distribution, metabolism, or elimination of the study drug, in the opinion of the PI or designee.

6. Use of albuterol or a similar bronchodilator.

7. Immunization with a COVID-19 vaccine in the 14 days prior to the first study drug administration.

8. Scheduled immunization with a COVID-19 vaccine (first or second dose) during the study that, in the opinion of an investigator, could potentially interfere with subject participation, subject safety, study results, or any other reason.

9. History or allergy of rare hereditary problems of galactose and/or lactose intolerance, lactase deficiency or glucose-galactose malabsorption.

10. Unable to refrain from or anticipates the use of:

    1. Any drug, including prescription and non-prescription medications, herbal remedies, or vitamin supplements beginning 14 days prior to the first dosing and throughout the study.
    2. Seasonal use of albuterol or other similar inhalers throughout study participation, beginning 14 days prior to the first dosing or 5 half-lives, whichever is longer.

11. Use of St. John's wort in the 28 days prior to the first study drug administration.

12. Positive Screening results for tuberculosis, HIV Ag/Ab combo, hepatitis B surface antigen or hepatitis C virus tests, or a positive test for alcohol, cotinine, and/or drugs of abuse.

13. Participation in another clinical study within 30 days prior to the first study drug administration. The 30-day window will be derived from the date of the last study drug administration.

14. Had a treatment with another investigational drug within 5 times the elimination half-life, if known (eg, a marketed product) or within 30 days (if the elimination half-life is unknown) prior to the first study drug administration.

15. Donation of plasma in the 14 days prior to the first study drug administration.

16. Donation or loss of 500 mL or more of blood in the 56 days prior to the first study drug administration.

17. Demonstrates an inability to operate the inhalation device after training.

18. History or presence of any drug or food allergies.

The investigators, study coordinators, study subjects and the Sponsor will be blinded to treatment assignment.