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

Key Who May Qualify: - 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): 1. Short-acting β2 agonist (SABA) used as rescue/reliever medication (as needed) only. 2. Low- or medium-dose inhaled corticosteroids (ICS). 3. Leukotriene receptor antagonist (LTRA). 4. Low-dose ICS/long-acting β2-agonist (LABA). 5. Medium-dose ICS/LABA. - Female participants who experience menarche must have a negative urine pregnancy test at screening. Key Who Should NOT Join This Trial: - 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). Always talk to your doctor about whether this trial is right for you.