Patient demographics and baseline characteristics
| Pooled phase 3 | Pooled phase 2b/3 | ||
| PBO (n=237) | BKZ 160 mg Q4W (n=349) | BKZ 160 mg Q4W (N=848) | |
| Age, years, mean (SD) | 38.8 (12.1) | 40.0 (11.8) | 40.3 (11.9) |
| Male, n (%) | 145 (61.2) | 233 (66.8) | 606 (71.5) |
| r-axSpA, n (%) | 111 (46.8) | 221 (63.3) | 604 (71.2) |
| BMI, kg/m2, mean (SD) | 27.4 (5.7) | 26.9 (5.9) | 27.0 (5.5) |
| HLA-B27 positive, n (%) | 187 (78.9) | 294 (84.2) | 717 (84.6)* |
| Current tobacco use at baseline, n (%) | 56 (23.6)† | 87 (24.9) | n/a |
| Geographical region, n (%) | |||
| Asia | 34 (14.3) | 55 (15.8) | 88 (10.4) |
| Eastern Europe | 126 (53.2) | 181 (51.9) | 543 (64.0) |
| North America | 12 (5.1) | 15 (4.3) | 37 (4.4) |
| Western Europe | 65 (27.4) | 98 (28.1) | 180 (21.2) |
| Time since first axSpA symptoms, years, mean (SD) | 10.3 (8.9) | 12.4 (10.5) | 12.4 (9.9) |
| ASDAS, mean (SD) | 3.7 (0.7) | 3.7 (0.8)‡ | 3.8 (0.8)§ |
| BASDAI, mean (SD) | 6.6 (1.3) | 6.6 (1.3) | 6.6 (1.3) |
| hs-CRP, mg/L, geometric mean (geometric CV, %) | 5.7 (216.6) | 5.8 (286.5) | 7.1 (238.1)§ |
| A history of uveitis, n (%) | 45 (19.0) | 52 (14.9) | 130 (15.3) |
| Prior TNFi exposure, n (%) | 34 (14.3) | 47 (13.5) | 108 (12.7) |
| Concomitant medication use at baseline, n (%) | |||
| csDMARDs | 51 (21.5) | 77 (22.1) | 197 (23.2) |
| Methotrexate | 14 (5.9) | 19 (5.4) | 51 (6.0) |
| Sulfasalazine | 33 (13.9) | 53 (15.2) | 130 (15.3) |
| Hydroxychloroquine | 1 (0.4) | 1 (0.3) | 3 (0.4) |
| Leflunomide | 2 (0.8) | 0 | 2 (0.2) |
| More than one | 1 (0.4) | 4 (1.1) | 11 (1.3) |
| NSAIDs | 178 (75.1) | 277 (79.4) | 689 (81.3) |
| Corticosteroids | 22 (9.3) | 22 (6.3) | 70 (8.3) |
*Six patients had missing HLA-B27 status at baseline.
†One patient had missing tobacco use status at baseline.
‡n=348.
§n=847.
ASDAS, Axial Spondyloarthritis Disease Activity Score; axSpA, axial spondyloarthritis; BASDAI, Bath Ankylosing Spondylitis Disease Activity Index; BKZ, bimekizumab; BMI, body mass index; csDMARD, conventional synthetic disease-modifying antirheumatic drug; CV, coefficient of variation; HLA-B27, human leucocyte antigen-B27; hs-CRP, high-sensitivity C-reactive protein; NSAID, non-steroidal anti-inflammatory drug; PBO, placebo; Q4W, every 4 weeks; r-axSpA, radiographic axial spondyloarthritis; TNFi, tumour necrosis factor inhibitor.