The primary purpose of this study is to evaluate the effects of Fluticasone Furoate (FF)/ Umeclidinium (UMEC)/ Vilanterol (VI) on lung function compared with FF/VI after 24 weeks of treatment.

Inclusion Criteria:

• Participant must be 12 to 17 years of age (inclusive), at the time of signing the informed consent/assent.
• Participants who have a diagnosis of asthma as defined by the National Institutes of Health [NIH, 2020] at least 1 year prior to Visit 0.
• Participants who have required daily Inhaled corticosteroids (ICS)/ Long-Acting Beta2-Agonist (LABA) treatment for at least 12 weeks prior to Visit 0 with no changes to maintenance asthma medications during the 6 weeks immediately prior to Visit 0 (including no changes to a stable total ICS dose of >250 to <=500 microgram (mcg)/day fluticasone propionate, or equivalent).
• In the 1 year prior to Visit 1: A documented healthcare contact for acute asthma symptoms; OR A documented temporary change in asthma therapy for acute asthma symptoms, according to a prespecified asthma action plan (or equivalent).
• Participants with inadequately controlled asthma (ACQ-6 score ≥1.5) at Visit 1, despite ICS/LABA maintenance therapy.
• A best pre-bronchodilator FEV1 >40% to <=90% of the predicted normal value and a ≥12% increase in FEV1 with albuterol/salbutamol at Visit 1. Predicted values will be based on the European Respiratory Society (ERS) Global Lung Function Initiative.

Exclusion Criteria:

• Chest X-ray documented pneumonia in the 6 weeks prior to Visit 1.
• Any asthma exacerbation requiring a change in maintenance asthma therapy and/or the use of systemic corticosteroids for at least 3 days in the 6 weeks prior to Visit 1. (Participants requiring a temporary change in asthma therapy (e.g., oral corticosteroids or increased dose of ICS) to treat an exacerbation in the 6 weeks prior to Visit 1 are not explicitly excluded at Visit 1 provided that, at the Investigator's discretion, the participant's condition is stable after they have resumed their pre-exacerbation maintenance asthma therapy (without modification), returned to their baseline asthma status and they are considered appropriate for enrollment into this study of up to 6 months duration)
• History of Life-threatening Asthma
• Participants with current evidence of active pulmonary diseases or abnormalities other than asthma (e.g., pneumonia, active tuberculosis, significant bronchiectasis, etc.).
• Current smokers and users of other inhaled products for recreation with or without nicotine (defined as participants who use cigarettes, e-cigarettes, other/vaping-related devices, cigars or pipe tobacco]) within 12 months prior to Visit 1.

Qualified researchers may request access to anonymized individual patient-level data (IPD) and related study documents of the eligible studies via the Data Sharing Portal. Details on GSK's data sharing criteria can be found at: https://www.gsk.com/en-gb/innovation/trials/data-transparency/

Anonymized IPD will be made available within 6 months of publication of primary, key secondary and safety results for studies in product with approved indication(s) or terminated asset(s) across all indications.

Anonymized IPD is shared with researchers whose proposals are approved by an Independent Review Panel and after a Data Sharing Agreement is in place. Access is provided for an initial period of 12 months but an extension may be granted, when justified, for up to 6 months.