A Study to Compare the Relative Potency of Salbutamol Administered Via Metered Dose Inhalers (MDI) Containing Propellants HFA-152a to HFA-134a in Mild Asthmatics Aged 18 to 65 Inclusive

1. Male or female; females may be of childbearing potential, of nonchildbearing potential, or postmenopausal.

2. Participant must be 18 to 65 years of age inclusive, at the time of screening.

3. ≥50 kg, at the time of screening.

4. Body mass index (BMI) with 19.0-35.0 kg/m2 inclusive, at the time of screening.

4\. Documented history of asthma ≥ 6 months. 5. Receiving 1 of following asthma treatments, at a stable dose, for at least 12 weeks prior to the screening visit and is anticipated to remain stable for the duration of the study: i. Short-acting beta-agonist (SABA) only. ii. Daily maintenance low-dose inhaled corticosteroids (ICS) (defined as 100-250 μg/day fluticasone propionate or equivalent plus or minus SABA which is anticipated to remain stable for the duration of the study.

iii. Daily maintenance low-dose ICS + Long-acting beta-2 agonist (LABA) therapy (low-dose ICS defined as 100-250 μg/day fluticasone propionate or equivalent as defined by GINA \[GINA, 2023\]) plus or minus SABA, which is anticipated to remain stable for the duration of the study.

6\. No severe asthma exacerbations within 6 months prior to screening and ≤1 severe exacerbation during the 12 months prior to screening.

7\. Pre-bronchodilator FEV1 ≥80% of predicted, at screening. 8. PC20 to methacholine of ≤8 mg/mL, at screening. 9. Participants should be able to withhold SABA for ≥12 hours and LABA-containing medications for ≥48 hours for the purposes of performing the spirometry and methacholine challenge at screening and during the study visits (treatment periods).

10\. A female participant is eligible to participate if she is not pregnant or breastfeeding, and Is a woman of woman of nonchildbearing potential (WONCBP) OR ii. Is a woman of child bearing potential (WOCBP) and using a contraceptive method that is highly effective.

11\. Provide signed informed consent which includes compliance with the requirements and restrictions listed in the informed consent form and in this protocol.

12\. Non-smokers who have not used any tobacco containing-products within 12 months prior to study start, and with a total pack year history of ≤10 pack years.

What this study is about