Study to Evaluate the Efficacy and Safety of Filgotinib in Participants With Active Ankylosing Spondylitis Who Have an Inadequate Response to Biologic Disease-Modifying Antirheumatic Drug Therapy

The primary objective of this study is to evaluate the effect of filgotinib versus placebo on signs and symptoms of active ankylosing spondylitis (AS), evaluated by Assessment of SpondyloArthritis international Society 40% improvement (ASAS40) response at Week 16 in participants with active AS who have an inadequate response to biologic disease-modifying antirheumatic drug therapy.