This study is looking at how well a combination of three medicines, Fluticasone Furoate (FF), Umeclidinium (UMEC), and Vilanterol (VI), works for asthma compared to just two of them, FF and VI, in kids aged 12-17. It lasts for 24 weeks, or about 6 months. To join, participants must be between 12 and 17 years old and have had asthma diagnosed at least a year before starting the study. They should be using certain asthma treatments every day for at least 12 weeks before they join, without changing their medication recently. The study checks if their asthma is not well controlled even with these medicines. Some things that would stop you from joining include having pneumonia recently or other lung diseases, or if you smoke.

• The study lasts 24 weeks (about 6 months).
• Participants must have been on steady asthma medication for at least 12 weeks.
• Smoking or recent severe asthma issues may exclude you.