Efficacy outcomes at week 16 (primary and ranked secondary endpoints) and week 24
| Week 16 | Week 24 | |||||
| PBO | BKZ 160 mg Q4W | P value* | BKZ vs PBO difference,† mean or % (95% CI) | PBO→BKZ 160 mg Q4W | BKZ 160 mg Q4W | |
| nr-axSpA (BE MOBILE 1) | n=126 | n=128 | n=126 | n=128 | ||
| r-axSpA (BE MOBILE 2) | n=111 | n=221 | n=111 | n=221 | ||
| Primary endpoint | ||||||
| ASAS40 (NRI), n (%) | ||||||
| nr-axSpA | 27 (21.4) | 61 (47.7) | <0.001 | 27.0 (15.6 to 38.4) | 59 (46.8) | 67 (52.3) |
| r-axSpA | 25 (22.5) | 99 (44.8) | <0.001 | 21.8 (11.4 to 32.1) | 63 (56.8) | 119 (53.8) |
| Ranked secondary endpoints‡ | ||||||
| ASAS40 in TNFi-naïve patients (NRI),§ n (%) | ||||||
| r-axSpA | 22 (23.4)¶ | 84 (45.7)** | <0.001 | 22.2 (10.6 to 33.9) | 56 (59.6)¶ | 100 (54.3)** |
| BASDAI CfB (RBMI/MI), mean (SE) | ||||||
| nr-axSpA | –1.5 (0.2) | –3.1 (0.2) | <0.001 | −1.5 (−2.0 to −1.0) | –3.2 (0.2) | –3.4 (0.2) |
| r-axSpA | –1.9 (0.2) | –2.9 (0.1) | <0.001 | −1.0 (−1.5 to −0.6) | –3.3 (0.2) | –3.3 (0.1) |
| ASAS20 (NRI), n (%) | ||||||
| nr-axSpA | 48 (38.1) | 88 (68.8) | <0.001 | 31.4 (19.5 to 43.2) | 87 (69.0) | 96 (75.0) |
| r-axSpA | 48 (43.2) | 146 (66.1) | <0.001 | 24.0 (12.8 to 35.2) | 85 (76.6) | 159 (71.9) |
| ASAS partial remission (NRI), n (%) | ||||||
| nr-axSpA | 9 (7.1) | 33 (25.8) | <0.001 | 19.4 (10.1 to 28.7) | 35 (27.8) | 37 (28.9) |
| r-axSpA | 8 (7.2) | 53 (24.0) | <0.001 | 14.7 (7.3 to 22.1) | 28 (25.2) | 56 (25.3) |
| ASDAS-MI (NRI), n (%) | ||||||
| nr-axSpA | 9 (7.1) | 35 (27.3) | <0.001 | 19.0 (10.7 to 27.2) | 37 (29.4) | 41 (32.0) |
| r-axSpA | 6 (5.4) | 57 (25.8) | <0.001 | 18.6 (10.9 to 26.3) | 43 (38.7) | 67 (30.3) |
| ASAS 5/6 (NRI), n (%) | ||||||
| nr-axSpA | 26 (20.6) | 58 (45.3) | <0.001 | 25.7 (14.1 to 37.3) | 60 (47.6) | 69 (53.9) |
| r-axSpA | 21 (18.9) | 109 (49.3) | <0.001 | 29.3 (19.2 to 39.3) | 63 (56.8) | 122 (55.2) |
| BASFI CfB (RBMI/MI), mean (SE) | ||||||
| nr-axSpA | –1.0 (0.2) | –2.5 (0.2) | <0.001 | −1.5 (−2.0 to −1.0) | –2.3 (0.2) | –2.8 (0.2) |
| r-axSpA | –1.1 (0.2) | –2.2 (0.1) | <0.001 | −1.1 (−1.5 to −0.6) | –2.2 (0.2) | –2.4 (0.2) |
| Nocturnal spinal pain CfB (RBMI/MI), mean (SE) | ||||||
| nr-axSpA | –1.7 (0.2) | –3.6 (0.3) | <0.001 | −1.8 (−2.4 to −1.2) | –3.5 (0.2) | –4.0 (0.3) |
| r-axSpA | –1.9 (0.2) | –3.3 (0.2) | <0.001 | −1.5 (−2.0 to −1.0) | –3.7 (0.3) | –3.8 (0.2) |
| ASQoL CfB (RBMI/MI), mean (SE) | ||||||
| nr-axSpA | –2.5 (0.4) | –5.2 (0.4) | <0.001 | −2.6 (−3.7 to −1.6) | –4.8 (0.4) | –5.7 (0.4) |
| r-axSpA | –3.2 (0.3) | –4.9 (0.3) | <0.001 | −1.5 (−2.4 to −0.7) | –4.9 (0.4) | –5.4 (0.3) |
| SF-36 PCS CfB (RBMI/MI), mean (SE) | ||||||
| nr-axSpA | 5.5 (0.7) | 9.5 (0.7) | <0.001 | 4.0 (2.1 to 5.8) | 10.1 (0.8) | 10.6 (0.8) |
| r-axSpA | 5.9 (0.8) | 9.3 (0.6) | <0.001 | 3.4 (1.7 to 5.1) | 10.6 (0.8) | 10.8 (0.6) |
| BASMI CfB (RBMI/MI),§ mean (SE) | ||||||
| r-axSpA | –0.2 (0.1) | –0.5 (0.1) | 0.006 | −0.3 (−0.5 to −0.1) | –0.5 (0.1) | –0.6 (0.1) |
Randomised set. Missing data were imputed using NRI for binary endpoints, RBMI for continuous endpoints at week 16 and MI for continuous endpoints at week 24.
*All tests were performed at a two-sided alpha level of 0.05. For binary endpoints, p values were calculated by logistic regression with treatment, MRI/CRP classification and region (BE MOBILE 1) or treatment, prior TNFi exposure and region (BE MOBILE 2) as factors. For continuous endpoints, p values were obtained by ANCOVA with treatment, MRI/CRP classification and region (BE MOBILE 1) or treatment, prior TNFi exposure and region (BE MOBILE 2) as fixed effects and baseline values as covariates.
†All between-group differences are adjusted risk differences (percentages) from the logistic regression model for binary endpoints or mean differences vs placebo from the ANCOVA model for continuous endpoints.
‡The statistical testing hierarchies are presented in online supplemental figure S2.
§Ranked secondary endpoint in BE MOBILE 2, data from BE MOBILE 1 are not presented as the endpoint was not in the statistical testing hierarchy for BE MOBILE 1.
¶n=94.
**n=184.
ANCOVA, analysis of covariance; ASAS20/40, Assessment of Spondyloarthritis international Society 20%/40% response; ASDAS-MI, Ankylosing Spondylitis Disease Activity Score major improvement; ASQoL, Ankylosing Spondylitis Quality of Life; BASDAI, Bath Ankylosing Spondylitis Disease Activity Index; BASFI, Bath Ankylosing Spondylitis Functional Index; BASMI, Bath Ankylosing Spondylitis Metrology Index; BKZ, bimekizumab; CfB, change from baseline; CRP, C-reactive protein; MI, multiple imputation; nr-axSpA, non-radiographic axial spondyloarthritis; NRI, non-responder imputation; PBO, placebo; Q4W, every 4 weeks; r-axSpA, radiographic axial spondyloarthritis; RBMI, reference-based multiple imputation; SF-36 PCS, Short-Form 36-item Health Survey Physical Component Summary; TNFi, tumour necrosis factor inhibitor.