This clinical trial is focused on studying the effects of a medication called filgotinib in adults with a condition known as axial spondyloarthritis. Axial spondyloarthritis is a type of arthritis that primarily affects the spine and the joints connecting the spine to the pelvis, causing inflammation and pain. The study will use Jyseleca tablets, which contain the active ingredient filgotinib, in doses of 100 mg and 200 mg. Some participants will receive a placebo, which looks like the filgotinib tablets but does not contain the active ingredient, to help compare the effects of the actual medication.

The purpose of the study is to evaluate how well filgotinib works in reducing the signs and symptoms of axial spondyloarthritis. Participants will be randomly assigned to receive either the filgotinib tablets or the placebo. The study will be conducted in a double-blind manner, meaning neither the participants nor the researchers will know who is receiving the actual medication or the placebo. This helps ensure that the results are not influenced by expectations about the treatment. The study will last for a period of time, during which participants will take the tablets orally and attend regular check-ups to monitor their condition and any changes in their symptoms.

Throughout the study, the effectiveness of filgotinib will be assessed by looking at various measures of disease activity and quality of life. These assessments will include changes in pain levels, physical function, and overall well-being. The study aims to provide valuable information about the potential benefits and safety of filgotinib for people living with axial spondyloarthritis. Participants will be closely monitored for any side effects or adverse reactions to ensure their safety during the trial.