The primary objective of this study was to assess the effect of multiple doses of the HFA-152a propellant and the HFA-134a propellant on mucociliary clearance (MCC).

This clinical trial was a Phase I, single-centre, multiple-dose, randomised, open-label, controlled, 2-way cross-over study to assess the effect on MCC of the new HFA-152a propellant (5 inhalations BID for 8 days) versus the marketed HFA-134a propellant (5 inhalations BID for 8 days) in adult healthy volunteers by measuring the clearance from the lungs of inhaled radioaerosol.

A total of 20 subjects were randomised into the study.

Standard safety assessments was conducted during the Study, including safety blood and urine laboratory tests, vital signs, physical examinations, ECGs, spirometry, and observations of any adverse events (AE).

Inclusion Criteria:

1. Subject's written informed consent obtained prior to any study-related procedure;
2. Healthy male and female subjects aged 18-55 years (inclusive);
3. Ability to understand the study procedures, the risks involved and ability to be trained to use the inhalers correctly;
4. Body Mass Index (BMI) between 18 and 30 kg/m2 (extremes inclusive);
5. Non-smokers or ex-smokers who smoked < 5 pack-years and stopped smoking > 5 years prior to screening;
6. Good physical and mental status at screening and before randomisation;
7. Vital signs within normal limits at screening; body temperature < 37.5°C;
8. 12-lead digitised electrocardiogram (ECG) in triplicate considered as normal at screening;
9. Lung function measurements within normal limits at screening;
10. Female subjects fulfilling one of the following criteria: Women of non-childbearing potential (WONCBP). Women of childbearing potential (WOCBP) with fertile male partners: they and/or their partner must be willing to use a highly effective birth control method preferably with low user dependency, from the signature of the informed consent form (ICF) and until the follow-up call.
11. Male subjects fulfilling one of the following criteria: Fertile male subjects with a pregnant or non-pregnant WOCBP partner: they must be willing to use male condom, from the signature of the ICF until the follow-up call.

Exclusion Criteria:

1. Participation in another clinical study with an investigational drug in the 3 months or five half-lives of that investigational drug (whichever is longer) preceding the administration of the study treatment;
2. Clinically relevant and uncontrolled respiratory, cardiac, hepatic, gastrointestinal, renal, endocrine, metabolic, neurologic, or psychiatric disorders ;
3. Clinically relevant abnormal laboratory values at screening;
4. Subjects with history of breathing problems (i.e. history of asthma including childhood asthma);
5. Positive serology test for human immunodeficiency virus (HIV) 1 or HIV2 serology at screening;
6. Positive results from the hepatitis serology, indicating acute or chronic hepatitis B or hepatitis C at screening;
7. Blood donation or blood loss (≥ 450 mL) during the 2 months prior to screening or randomisation;
8. Positive urine test for cotinine at screening or prior to randomisation;
9. Documented history of alcohol abuse within 12 months prior to screening, an average weekly alcohol intake of greater than 14 units, or a positive alcohol breath test at screening or prior to randomisation;
10. Documented history of drug abuse within 12 months prior to screening or a positive urine drug screen evaluated at screening or prior to randomisation;
11. Intake of non-permitted concomitant medications in the predefined period prior to screening or prior to randomisation;
12. Presence of any current infection, or previous infection that resolved less than 1 week prior to screening or to randomisation;
13. Known intolerance and/or hypersensitivity to any of the excipients contained in the formulation used in the study;
14. Documented coronavirus disease 2019 (COVID-19) diagnosis within the last 2 weeks, or associated complications/symptoms which have not resolved within 2 weeks prior to screening or prior to randomisation;
15. Heavy caffeine drinker;
16. For females only: pregnant or lactating women;
17. The use of any kind of smoking electronic devices (e.g. e-cigarettes), within 6 months before screening or prior to randomisation;
18. Subjects for whom participation in this study will exceed a total radiation exposure of 5 mSv in the last 12-month period or 10 mSv in the last 5-year period;
19. Subjects with a total dosimetry value (including history of exposure through occupation) which contraindicates their participation in the study.

The recording of adverse events (AEs) was the period starting from the time of the Informed Consent signature (Visit 1, Day 2 to 21 before Treatment period 1 (Day-1)) and until the subject's study participation ended at either an Early termination visit or a Follow-up visit or call ( 7-10 days after last intake of study treatment).

A follow-up call (or visit) had to be performed in case of early termination as well, if the early termination visit was performed less than 7 days after the intake of the last dose of the study treatment.

Safety set was used for the evaluation of AEs. Safety set included all subjects who were randomised and received at least one dose of study drug (HFA-152a or HFA-134a).