Bimekizumab's reduction in spinal MRI inflammation held at two years

Design

Phase 3 RCT with open-label extension, MRI substudy

Population

102 patients with radiographic axial spondyloarthritis with MRI at four time points

Primary outcome

Change in CANDEN spinal inflammation and structural scores

Effect

Inflammation -7.3 at week 16 and -6.6 at week 104

An analysis of the BE MOBILE 2 trial and its open-label extension (Rheumatology, 5 October 2026) scored spinal MRIs with the Canada-Denmark system in 102 of 332 patients with radiographic axial spondyloarthritis who had scans at baseline and weeks 16, 52 and 104.

Total spinal inflammation fell by 7.3 points by week 16 and remained reduced at week 104 (-6.6), across anatomical regions including the posterolateral elements. Fat lesions increased early (1.6 by week 16) in patients who had inflammation at baseline, then changed little. Erosions and new bone formation changed minimally.

The sustained effect on inflammation is reassuring for a dual IL-17A and IL-17F inhibitor. Fat lesions are thought to follow resolved inflammation and may precede new bone, so the stability after week 16 is of interest, but two years is too short to judge structural progression.

• Expect MRI inflammation to fall early on bimekizumab and stay low on continued treatment
• Interpret new fat lesions on follow-up MRI as a likely sign of resolved inflammation
• Do not use two-year data to promise prevention of new bone formation
• Use MRI selectively when clinical response is unclear

Why it matters

It shows the imaging response persists rather than fading with longer treatment.

Don't overread it

Open-label, observed-case data in a subset - not evidence of structural disease modification.

The statistics, in plain English

These are observed-case mean changes in under a third of the trial population, with no comparator after week 16, so selection and regression to the mean may contribute.

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