van der Heijde D, Gensler LS, Deodhar A, et al. - A phase IIb dose-ranging study was designed to evaluate the efficacy and safety in patients with active ankylosing spondylitis (AS). Researchers randomized AS adults(fulfilling modified New York criteria) in 1:1:1:1:1 ratio to bimekizumab 16 mg, 64 mg, 160 mg, 320 mg or placebo every 4 weeks for 12 weeks (double-blind period). At week 12, patients receiving bimekizumab 16 mg, 64 mg or placebo were re-randomised 1:1 to bimekizumab 160 mg or 320 mg every 4 weeks to week 48; other patients continued on their initial dose (dose-blind period). The primary outcome included Assessment of SpondyloArthritis international Society (ASAS) 40 response at week 12 (non-responder imputation (NRI) for missing data). Three-hundred three patients were assigned randomly to bimekizumab 16 mg (n=61), 64 mg (n=61), 160 mg (n=60), 320 mg (n=61) or placebo (n=60). Rapid and sustained improvements in key outcome measures were provided by bimekizumab in patients with active AS, with no unexpected safety findings versus previous studies.