A Study to Assess and Compare Safety and Tolerability of 3 Months Treatment With Salbutamol Administered Via MDI Containing Propellant HFA-152a or HFA-134a in Participants ≥ 18 Years of Age With Asthma

Prior treatment

• Asthma Exacerbation: Any severe asthma exacerbation within 6 months prior to screening.
• Current or chronic history of liver disease or known hepatic or biliary abnormalities (with the exception of Gilbert's syndrome or asymptomatic gallstones) Biologic/immunosuppressive therapies used for the treatment of respiratory diseases during the 6 months, or 5 half-lives-whichever is longer-prior to start of the study.

Other illness

• A history of life-threatening asthma or asthma that is unstable in the opinion of the investigator.
• Other significant pulmonary diseases to include (but not limited to): pneumothorax, pulmonary fibrotic disease, bronchopulmonary dysplasia, chronic bronchitis, emphysema, chronic obstructive pulmonary disease, tuberculosis or other respiratory abnormalities other than asthma.
• Respiratory Infection: Culture-documented or suspected bacterial or viral infection of the upper or lower respiratory tract, sinus or middle ear that is not resolved within 4 weeks of screening that led to a change in asthma management, OR in the opinion of the Investigator, is expected to affect the participant's asthma status, OR the participant's ability to participate in the study.

• Participant of ≥18 years of age at the time of signing the informed consent or written informed consent is obtained from each study participant's legal guardian.
• Asthma for ≥ 6 months, defined as:
  • Documented history of asthma, as defined by Global Initiative for Asthma (GINA) (GINA, 2023\]
  • Receiving one of the following asthma treatments, at a stable dose (applicable to daily Inhaled corticosteroid (ICS), ICS/Long-acting bronchodilator (LABA), and ICS/LABA/Long-acting muscarinic antagonist \[LAMA\]), for at least 12 weeks prior to the screening visit, with treatment that is anticipated to remain stable for the duration of the study:
  • Short-Acting Beta-2-Adrenoreceptor Agonists (SABA) used as needed for asthma symptoms
  • Daily maintenance low to medium dose Inhaled corticosteroid (ICS) (low to medium dose ICS defined as 100-500 μg/day fluticasone propionate or equivalent as defined in the 2023 GINA guidelines \[GINA, 2023\], plus Short-Acting Beta-2-Adrenoreceptor Agonists (SABA), which is anticipated to remain stable for the duration of the study.
  • Daily maintenance low to medium dose ICS/ Long-acting bronchodilator (LABA) (low to medium dose ICS defined as 100-500 μg/day fluticasone propionate or equivalent as defined in the GINA guidelines \[GINA, 2023\] plus SABA, which is anticipated to remain stable for the duration of the study.
  • Daily maintenance ICS/LABA/LAMA (low to medium dose ICS defined as 100-500 µg/day fluticasone propionate or equivalent as defined in the GINA guidelines \[GINA, 2023\] plus SABA, which is anticipated to remain stable for the duration of the study.
  • Participants who utilize combination budesonide/formoterol as reliever therapy, whether or not this is in addition to a SABA - are not eligible for screening.
  • Participants who utilize ICS/SABA combination therapy as reliever therapy, in addition to low to medium dose ICS or ICS/LABA as maintenance, are only eligible if they agree to discontinue their ICS/SABA inhaler for the duration of the study (screening through follow-up).
• Severity of disease assessed by the investigator by baseline pre-bronchodilator Forced expiratory volume in 1 second (FEV1)
• Asthma Control Status
  • Asthma Control Questionnaire (ACQ) 6 score \<1.5 at screening
  • Asthma that has remained stable with no severe exacerbations in the last 6 months. Severe exacerbation defined as:
  • Deterioration of asthma-requiring the use of systemic corticosteroids (tablets, suspension or injection), for at least 3 days, OR
  • An inpatient hospitalization or Emergency Department (ED) visit because of asthma, requiring systemic corticosteroids.
• Evidence of reversibility of disease: Airway reversibility is defined as ≥12 percent (%) and ≥200 milliliter (mL) increase in FEV1 within 20 to 60 minutes following up to 4 inhalations of albuterol/salbutamol aerosol.
• Participants on as-needed SABA only, or daily maintenance ICS (plus as needed SABA):
  • With a documented history of reversibility (as defined above) within 2 years will meet this inclusion criterion. Pre- and post-bronchodilator measurements will still be collected at screening to characterize the degree of reversibility.
  • Who do not have a documented history of reversibility within the past 2 years will need to demonstrate reversibility during the screening period.
  • SABA should be withheld for ≥6 hours
  • Participants on daily maintenance ICS/LABA or ICS/LABA/LAMA:
• Participants on daily maintenance ICS/LABA or ICS/LABA/LAMA:
  • Do not need to demonstrate reversibility in accordance with the above definition during the screening period. A reversibility maneuver will be performed to characterize the degree of post-bronchodilator change.
  • SABA should be withheld for ≥6 hours
  • LABA- and LAMA-containing medications should be withheld for \>=24 hours for the characterization of post-bronchodilator change.
  • Participants should be able to withhold SABA for ≥6 hours and LABA-/ LAMA containing medications for ≥24 hours for the purposes of performing screening spirometry.