Long-term safety and efficacy of bimekizumab in axial spondyloarthritis: 2-year results from two phase 3 studies

Objectives Bimekizumab, a monoclonal IgG1 antibody that selectively inhibits IL-17F in addition to IL-17A, previously demonstrated efficacy and was well tolerated to 1 year in patients with non-radiographic (nr-) and radiographic (r-) axial spondyloarthritis (axSpA). Here, we report bimekizumab safety and efficacy to 2 years. Methods Patients completing week 52 in the phase 3 studies BE MOBILE 1 (nr-axSpA; NCT03928704) and 2 (r-axSpA; NCT03928743) were eligible for an ongoing open-label extension (OLE; NCT04436640). All OLE patients received subcutaneous bimekizumab 160 mg every 4 weeks. Safety outcomes for patients who received >= 1 bimekizumab dose, and efficacy outcomes for all randomized patients, are reported to week 104. Results In the OLE (weeks 52 - 104), 70.8% (367/518) of patients reported >= 1 treatment-emergent adverse event (TEAE). Most frequent TEAEs [exposure-adjusted incidence rate per 100 patient-years (EAIR/100PY)] were SARS-CoV-2 (COVID-19) infection (25.2), nasopharyngitis (11.0) and oral candidiasis (5.4). Fungal infection EAIR/100PY was 11.8 (majority Candida infections: 6.8; most mild/moderate, none serious/systemic). Inflammatory bowel disease and uveitis rates were low; no major adverse cardiovascular events or deaths occurred. TEAE incidence rate was generally similar across weeks 0 - 52 and 52 - 104. At week 104, >50% of randomized patients (N = 586) achieved Assessment of SpondyloArthritis international Society 40% response (ASAS40); similar to 60% achieved Axial Spondyloarthritis Disease Activity Score (ASDAS) low disease activity (<2.1) and >30% achieved ASDAS inactive disease (<1.3). Bimekizumab demonstrated sustained suppression of MRI inflammation at week 104, with >57% of patients achieving MRI remission. Results In the OLE (weeks 52 - 104), 70.8% (367/518) of patients reported >= 1 treatment-emergent adverse event (TEAE). Most frequent TEAEs [exposure-adjusted incidence rate per 100 patient-years (EAIR/100PY)] were SARS-CoV-2 (COVID-19) infection (25.2), nasopharyngitis (11.0) and oral candidiasis (5.4). Fungal infection EAIR/100PY was 11.8 (majority Candida infections: 6.8; most mild/moderate, none serious/systemic). Inflammatory bowel disease and uveitis rates were low; no major adverse cardiovascular events or deaths occurred. TEAE incidence rate was generally similar across weeks 0 - 52 and 52 - 104. At week 104, >50% of randomized patients (N = 586) achieved Assessment of SpondyloArthritis international Society 40% response (ASAS40); similar to 60% achieved Axial Spondyloarthritis Disease Activity Score (ASDAS) low disease activity (<2.1) and >30% achieved ASDAS inactive disease (<1.3). Bimekizumab demonstrated sustained suppression of MRI inflammation at week 104, with >57% of patients achieving MRI remission. Conclusions The safety profile of bimekizumab remained consistent with prior reports, with no new safety signals identified. 1-year efficacy was sustained to 2 years across patients with nr-axSpA and r-axSpA.