Long-term use of bimekizumab is well tolerated and does not raise new safety concerns in patients with axial spondyloarthritis (axSpA), according to two phase III studies.
Furthermore, patients show lasting clinical efficacy and inflammation control across the full disease spectrum of axSpA over 3 years.
“These results support bimekizumab as a durable long-term treatment option for patients with nonradiographic and radiographic axSpA, with a positive benefit-risk profile,” the researchers said.
Patients who completed week 52 of the phase III BE MOBILE 1 and BE MOBILE 2 studies were eligible to enter the open-label extension (OLE) and continue treatment with subcutaneous bimekizumab 160 mg every 4 weeks. The research team assessed safety outcomes for those who received ≥1 dose of the study drug and efficacy outcomes for all participants over 3 years (164 weeks; 112-week OLE).
Of the 574 patients with axSpA, 519 (90.4 percent) experienced at least one treatment-emergent adverse event (TEAE) during the overall safety period. [J Rheumatol 2026;53:1071-1082]
Safety outcomes
The exposure-adjusted incidence rate (EAIR) for fungal infection was 9.4 per 100 patient-years (PY), with Candida infection comprising the majority (5.3 per 100 PY). Most infections were mild or moderate in severity, and none were serious or systemic. The EAIRs for inflammatory bowel disease and uveitis were 0.5 and 1.5 per 100 PY, respectively.
Major adverse cardiovascular events (MACE) or deaths did not occur. Notably, the third year saw the lowest EAIRs, including those for Candida infections.
“No new safety signals were observed over 3 years of bimekizumab treatment, consistent with previous observations of the long-term safety profile of bimekizumab from the phase IIb BE AGILE study and its OLE, as well as other phase III studies in psoriatic arthritis, psoriasis, and hidradenitis suppurativa,” the researchers said. [RMD Open 2025;11:e005081; J Am Acad Dermatol 2025;93:644-53]
“EAIRs of TEAEs in year 3 generally remained stable or were numerically lower than those reported in year 2 and were typically lowest in the third year of the study, including for safety events of interest,” they added.
These results suggest no new safety concerns for patients after 3 years of bimekizumab use. Moreover, MACE or active tuberculosis were not observed throughout the BE MOBILE studies or their OLE. The rates of neutropenia and malignancies were also low.
“Although two adjudicated events of suicidal ideation and behaviour were reported in the BE MOBILE studies, none were reported during the OLE,” the researchers said. [Ann Rheum Dis 2024;83:199-213]
Efficacy outcomes
The observed 2-year efficacy of bimekizumab in the two trials persisted through week 164, during which 57.0 percent of patients achieved an Axial Spondyloarthritis Disease Activity Score (ASDAS) of <2.1, indicating low disease activity, including 28.7 percent who achieved ASDAS <1.3 (inactive disease).
Bimekizumab use also resulted in sustained improvements in Bath Ankylosing Spondylitis Functional Index (BASFI) and health-related quality of life scores, as well as sustained control of MRI inflammation, through week 164. Of the patients, 59.4 percent achieved Spondyloarthritis Research Consortium of Canada (SPARCC) sacroiliac joint scores <2, and 77.8 percent achieved Berlin spine scores ≤2.