The purpose of this study is to compare the effect of budesonide/albuterol metered-dose inhaler (BDA MDI) with albuterol sulfate metered-dose inhaler (AS MDI), both administered as needed, on the annualized rate of severe asthma exacerbations in adolescents with a documented clinical diagnosis of asthma and at least one severe exacerbation in the prior year.

This is a randomized, double-blind, multicenter, parallel-group Phase IIIb study with a fixed treatment period of 52 weeks.

The study will consist of 3 periods:

1. Screening period (7 to 28 days)
2. Treatment period of 52 weeks
3. Safety follow-up period (7 to 14 days after the end of treatment [EOT] visit)

Participants who meet the eligibility criteria will be randomly assigned to BDA MDI 160/180 micrograms (μg) or AS MDI 180 μg treatment groups in a 1:1 ratio on top of their own usual maintenance therapy during treatment period.

This study will also include a pharmacokinetic (PK) sub-study with single visit scheduled after the safety follow-up visit in the main study. During PK sub-study, single dose of open-label BDA MDI 160/180 μg will be administered.

Inclusion Criteria:

• Confirmed clinical diagnosis of asthma at least 12 months.

• Receiving one of the following scheduled asthma maintenance therapies for at least 3 months with stable dosing for at least the last one month

  1. Low-to-high-dose Inhaled corticosteroid(s) (ICS)
  2. Low-to-high-dose ICS or ICS/long-acting β2-agonist (LABA) with or without one additional maintenance therapy from the following: leukotriene receptor antagonist (LTRA), long-acting muscarinic antagonist (LAMA), or theophylline

• Receiving inhaled short-acting β2-agonist (SABA) as needed.

• A documented history of at least one severe asthma exacerbation within 12 months.

• Use of Sponsor-provided albuterol sulfate inhalation aerosol medication.

• Demonstrate acceptable MDI administration technique as assessed by the investigator; use of spacers is prohibited.

• Able to perform acceptable and reproducible peak expiratory flow (PEF) measurements as assessed by the investigator.

• Participants must adhere to protocol specific contraception methods.

• Negative urine pregnancy test for participants of childbearing potential.

• Have a BMI < 40 kg/ m^2.

• Capable of giving assent (signing the assent form) to participate in the study which includes compliance with the requirements and restrictions. The caregiver of the patient must be capable of giving written informed consent for the patient's participation in the study. Consent and assent forms must be completed prior to any study-specific procedures.

Exclusion Criteria:

• Life-threatening asthma defined as any history of significant asthma episode(s) requiring intubation associated with hypercapnia, respiratory arrest, hypoxic seizures, or asthma-related syncopal episode(s).
• Experienced > 3 severe asthma exacerbations within 12 months before screening.
• Completed treatment for lower respiratory infection and severe asthma exacerbation with SCS within 4 weeks of screening.
• Upper respiratory infection involving antibiotic treatment not resolved.
• Current smokers, former smokers with > 10 pack-years history, or former smokers who stopped smoking < 6 months (including all forms of tobacco, e-cigarettes [vaping], and marijuana).
• Other significant lung disease, including regular or occasional use of oxygen.
• Historical or current evidence of a clinically significant disease including, but not limited to: cardiovascular, hepatic, renal, hematological, neuropsychological, endocrine, or gastrointestinal disorders.
• Cancer not in complete remission for at least 5 years.
• History or hospitalization for psychiatric disorder or attempted suicide within one year.
• Significant abuse of alcohol or drugs, in the opinion of the investigator.
• Oral corticosteroid(s) (OCS)/SCS use (any dose and any indication) within 4 weeks before Visit 1 or chronic use of OCS/SCS (≥ 3 weeks use in 3 months prior to Visit 1).
• Use of any oral SABAs within one month.
• Having a known or suspected hypersensitivity to albuterol/salbutamol, or budesonide and/or their excipients.

Qualified researchers can request access to anonymized individual patient-level data from AstraZeneca group of companies sponsored clinical trials via the request portal Vivli.org. All requests will be evaluated as per the AZ disclosure commitment: https://astrazenecagrouptrials.pharmacm.com/ST/Submission/Disclosure.

"Yes", indicates that AZ are accepting requests for IPD, but this does not mean all requests will be approved.

AstraZeneca will meet or exceed data availability as per the commitments made to the EFPIA/PhRMA Data-Sharing Principles. For details of our timelines, please refer to our disclosure commitment at https://astrazenecagrouptrials.pharmacm.com/ST/Submission/Disclosure.

When a request has been approved AstraZeneca will provide access to the anonymized individual patient-level data via secure research environment Vivli.org. A Signed Data Usage Agreement (non negotiable contract for data accessors) must be in place before accessing requested information.