This is a Phase 1, randomized, double-blinded, placebo controlled, dose escalation study of HH-120 in healthy adult volunteers. HH-120 is a novel inhalable biologic being developed for COVID-19 treatment. The study aims to evaluate the safety, tolerability and pharmacokinetic profile of HH-120 administered by aerosol inhalation after single and multiple ascending doses.

Approximately 48 participants will be sequentially enrolled into either 1 of 3 SAD cohorts (n=8 per cohort), or 1 of 3 MAD cohorts (n= 8 per cohort). An adaptive dose escalation schedule will be employed for both SAD and MAD parts of the study.

Inclusion Criteria:

1. Healthy male or female volunteers aged 18 to 65 years (both inclusive)
2. Participants must have a body mass index between ≥ 18.0 and ≤ 32 .0 kg/m2 and a bodyweight of at least 45 kg at Screening.
3. Participants must be a non-smoker and must not have used any tobacco products within 90 days prior to Screening.
4. Participants must be in good general health, with no significant medical history, have no clinically significant abnormalities on physical examination at screening and/or before administration of the initial dose of IP.
5. Participants must have clinical laboratory values within normal range.
6. Females must be non-pregnant and non-lactating, and must use an acceptable, highly effective double contraception from Screening until study completion, including the follow-up period.
7. Males must not donate sperm for at least 90 days after the last dose of IP.
8. Participants must have the ability and willingness to attend the necessary visits to the CRU.

Exclusion Criteria:

1. Pregnant or lactating at Screening or planning to become pregnant (self or partner) at any time during the study, including the follow-up period.
2. Prior or ongoing medical conditions, medical history, physical findings, or laboratory abnormality that, in the PI's (or delegate's) opinion, could adversely affect the safety of the participant or that might interfere with the conduct of the study.
3. Presence of any underlying physical or psychological medical condition
4. Pre-existing severe obstructive disease of the respiratory system such as chronic obstructive pulmonary disease or asthma , including resolved childhood asthma, which may impact inhalation as judged by the PI, delegate, or Sponsor.
5. History or evidence o f any anatomical airway defect, which in the opinion of the PI, may impact inhalation.
6. Abnormal spirometry findings at Screening that are considered by the PI to be clinically significant, including FEV1 < 80% or FVC < 80%.
7. Blood donation of > 500 mL or significant blood loss within 60 days prior to the first IP administration or plasma donation within 7 days prior to IP administration.
8. Systemic or respiratory infection within 2 weeks before the Screening visit or fever (tympanic temperature > 37.5°C) or symptomatic viral or bacterial infection at time of Screening.
9. Current infection with SARS-CoV-2, infection within the 2 weeks prior to Screening, or a history of SARS-CoV-2 infection plus symptoms of post-COVID syndrome.
10. History of anaphylaxis or other significant allergy in the opinion of the PI or known allergy or hypersensitivity to any of the components of the IP.
11. History of malignancy, except for non-melanoma skin cancer, excised more than 2 years ago and cervical intraepithelial neoplasia that has been successfully cured more than 5 years prior to Screening.
12. A personal history of unexplained blackouts or fainting or known risk factors for Torsade de Pointes (eg, hypokalemia, heart failure).
13. Abnormal 12-lead ECG findings at Screening that are considered by the PI to be clinically significant, including arrhythmias or marked QT interval abnormalities (QTcF < 300 msec or ≥ 450 msec at Screening).
14. Confirmed (eg, 2 consecutive triplicate measurements) average systolic blood pressure (SBP) > 140 or < 90 mmHg, and diastolic blood pressure (DBP) > 90 or < 45 mmHg at Screening.
15. Confirmed (eg, 2 consecutive triplicate measurements) average resting HR > 100 or < 45 beats per minute at Screening.
16. Vaccination with a live vaccine within the 4 weeks prior to Screening or that is planned within 4 weeks of dosing, and any non-live vaccination within the 2 weeks prior to Screening, or that is planned within 2 weeks of dosing or planned during study participation (including vaccines for COVID-19).
17. Positive test for hepatitis C antibody (HCV), hepatitis B surface antigen (HBsAg), or human immunodeficiency virus (HIV) antibody at Screening.
18. Participants with a positive toxicology screening panel (urine test including qualitative identification of barbiturates, tetrahydrocannabinol [THC], amphetamines, benzodiazepines, opiates, cocaine, and cotinine), or alcohol breath test at Screening or Day -1.
19. Participants with a history of substance abuse or dependency or history of recreational intravenous (IV) drug use over the last 6 months (by self-declaration).
20. Use of any IP or medical device within 30 days prior to screening.
21. Use of any prescription drugs for 14 days prior to dosing or over the counter medication, herbal remedies, supplements or vitamins 7 days prior to dosing.

Double blind (Participant, Investigator)