A Study to Investigate How Budesonide and Formoterol Move Through the Body (Pharmacokinetics) When Delivered With Different Devices in Participants Aged 4 to Less Than 12 Years Old With Asthma

This is a phase I single-dose, 2-period cross-over, multicenter study in which the participants will be randomized 1:1 to one of two treatment sequences - AB or BA. In the first study period, participants will receive a single dose of either -

• Treatment A: Symbicort Aerosphere budesonide/formoterol fumarate × 2 puffs (test formulation)
• Treatment B: Symbicort pMDI budesonide/formoterol fumarate × 2 puffs (reference formulation)

After a washout period of at least 28 days and no longer than 42 days, participants who first received Treatment A will receive a single dose of Treatment B, and participants who first received Treatment B will receive a single dose of Treatment A in the study period 2.

Key Inclusion Criteria:

• Participants who have clinician-diagnosed asthma for at least 3 months.
• Body mass index ≤ 95 percentile for age and body weight of at least 15 kg or higher.
• Be on a stable dose of one of the following asthma treatments for at least 4 weeks prior to screening (Visit 1):

• Short-acting β2 agonist (SABA) used as rescue/reliever medication (as needed) only.
• Low- or medium-dose inhaled corticosteroids (ICS).
• Leukotriene receptor antagonist (LTRA).
• Low-dose ICS/long-acting β2-agonist (LABA).
• Medium-dose ICS/LABA.
• Female participants who experience menarche must have a negative urine pregnancy test at screening.

Key Exclusion Criteria:

• Current evidence of pneumonia, pneumothorax, atelectasis, pulmonary fibrotic disease, allergic bronchopulmonary aspergillosis, cystic fibrosis, bronchopulmonary dysplasia, or other severe respiratory abnormalities other than asthma.
• History of life-threatening asthma defined as any asthma episode associated with loss of consciousness, intubation or admission to an intensive care unit.
• History of severe asthma exacerbation within 8 weeks of Visit 1.
• Inability to change from any budesonide therapy to another suitable corticosteroid.
• Participants with a known hypersensitivity to budesonide and/or formoterol fumarate or any of the excipients of the product.
• Not be able to refrain from consuming alcohol and smoking (including electronic cigarettes, vaping, and marijuana) from the time of screening until after the safety follow-up visit.
• Unstable asthma.
• Received regular maintenance treatment with prohibited anti-inflammatory or long-acting bronchodilator asthma medication.
• Evidence of active liver disease.
• Prolonged QT interval corrected for heart rate using Fridericia's correction (QTcF).