Bimekizumab reduces MRI inflammation in axial spondyloarthritis studies

The analysis evaluated MRI and radiographic outcomes in patients with non-radiographic axial spondyloarthritis (nr-axSpA) in BE MOBILE 1 and radiographic axSpA (r-axSpA) in BE MOBILE 2. Both phase 3 trials included a 16-week placebo-controlled period followed by 36 weeks of maintenance; from week 16, all participants received bimekizumab 160 mg every four weeks. Eligible patients could continue treatment in an open-label extension (OLE). MRI inflammation and structural lesions were assessed through week 52, and radiographic structural damage through week 104. Results were based on observed cases.

At week 52, mean sacroiliac joint inflammation scores had decreased from baseline by 7.6 points in nr-axSpA and 5.1 points in r-axSpA. Spine inflammation scores decreased by 0.5 and 2.5 points, respectively. Erosion scores fell by 1.8 points in both groups, while backfill and fat-lesion scores increased; ankylosis scores changed little. At week 104, mean radiographic change was 0.03 on the modified New York scale in nr-axSpA and 0.3 on the mSASSS in r-axSpA.

The findings indicate reduced MRI inflammation and limited radiographic change during treatment, but do not establish comparative long-term structural benefit. After week 16 there was no continuing placebo group, and observed-case analyses may be affected by missing data. These imaging outcomes alone do not establish a reason to change treatment decisions.