Impact of Dual Interleukin‐17A and Interleukin‐17F Inhibition with Bimekizumab on Inflammatory and Structural Lesions in Axial Spondyloarthritis: MRI and Radiographic Outcomes from the Phase 3 BE MOBILE 1 and 2 Studies and their Open‐Label Extension

OBJECTIVES: To evaluate the impact of bimekizumab, a dual IL-17A and IL-17F inhibitor, on sacroiliac joint (SIJ) and spine inflammation/structural damage in axSpA using MRIs/radiographs from the phase 3 studies BE MOBILE 1 (nr-axSpA) and 2 (r-axSpA) and their open-label extension (OLE). METHODS: BE MOBILE 1 and 2 comprised 16-week double-blind placebo-controlled and 36-week maintenance periods. From Week 16, all received subcutaneous bimekizumab 160mg every 4 weeks. At Week 52, patients could enter the OLE to continue bimekizumab. MRIs were evaluated by treatment arm at baseline and Weeks 16/52 in BE MOBILE 1 and 2 MRI sub-studies using SPARCC SIJ and Berlin spine inflammation scores, and SPARCC SIJ Structural Score (SSS; erosion, backfill, fat lesions, ankylosis). In patients with baseline and Week 104 radiographs, structural damage was assessed in the SIJ (mNY; nr-axSpA) and spine (mSASSS; r-axSpA). Observed case data are reported. RESULTS: At Week 52, bimekizumab-randomised patients had substantially reduced inflammation (mean change from baseline [CfB]: SPARCC SIJ, nr-axSpA: -7.6; r-axSpA: -5.1; Berlin spine, nr-axSpA: -0.5; r-axSpA: -2.5), decreased erosion scores (nr-axSpA; -1.8; r-axSpA: -1.8), increased backfill (nr-axSpA: 0.9; r-axSpA: 0.6) and fat lesion scores (nr-axSpA: 0.7; r-axSpA: 0.5), and minimal changes in ankylosis (nr-axSpA: 0.0; r-axSpA: 0.2). With bimekizumab treatment to Week 104, radiographs showed mean CfB: 0.03 in mNY (nr-axSpA) and mSASSS: 0.3 (r-axSpA). CONCLUSIONS: Dual inhibition of IL-17A and IL-17F with bimekizumab led to substantial reductions in MRI SIJ/spine inflammation, gradual decreases in SIJ erosion, and minimal radiographic progression in the SIJ/spine in patients with axSpA.