PO:02:022 | Bimekizumab Maintained Stringent Clinical Responses over 2 Years in Patients with Axial Spondyloarthritis: Results from Two Phase 3 Studies

Fabian Proft¹, Désirée Van Der Heijde², Sergio Schwartzman^3|4|5, Joerg Ermann⁶, Alexander Marten⁷, Ute Massow⁷, George Stojan⁸, Vanessa Taieb⁹, Diana Voiniciuc¹⁰, Astrid Van Tubergen¹¹, Victoria Navarro-Compán¹², Simone Angioni¹³, Xenofon Baraliakos¹⁴ | ¹Charité-Universitätsmedizin Berlin; Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany; ²Department of Rheumatology, Leiden University Medical Center Leiden, The Netherlands; ³Weill Cornell Medical Center New York, USA; ⁴New York Presbyterian Hospital New York, USA; ⁵Hospital for Special Surgery New York, USA; ⁶Division of Rheumatology, Inflammation and Immunity, Brigham and Women's Hospital and Harvard Medical School Boston, USA; ⁷UCB Monheim am Rhein Germany; ⁸UCB Atlanta, USA; ⁹UCB Colombes, France; ¹⁰UCB Slough, United Kingdom; ¹¹Department of Medicine, Division of Rheumatology, Maastricht University Medical Center Maastricht, The Netherlands; ¹²Department of Rheumatology, La Paz University Hospital, IdiPaz Madrid, Spain; ¹³UCB Milan, Italy; ¹⁴Rheumazentrum Ruhrgebiet Herne, Ruhr-University Bochum, Germany

Purpose of the Work. Bimekizumab (BKZ) is a monoclonal IgG1 antibody that selectively inhibits IL-17F and IL-17A. BKZ demonstrated sustained clinical efficacy to Week (Wk) 52 in patients (pts) across the full disease spectrum of axial spondyloarthritis (axSpA) in the phase 3 studies BE MOBILE 1 and 2.[1] This analysis assessed the maintenance of response to BKZ over 2 years in the open-label extension (OLE) of those studies.

Materials and Methods. BE MOBILE 1 (NCT03928704) and 2 (NCT03928743) comprised a 16-wk double-blind period followed by a 36-wk maintenance period in pts with non-radiographic and radiographic axSpA, respectively.[1] Pts were randomised to receive subcutaneous BKZ 160 mg every 4wks (Q4W) or placebo (PBO); from Wk16, all received BKZ. At Wk52, eligible pts could enter BE MOVING (OLE; NCT04436640). Proportions of pts achieving Assessment of SpondyloArthritis international Society >=40% (ASAS40) improvement, ASAS partial remission (PR), axSpA Disease Activity Score (ASDAS) low disease activity (LDA) and ASDAS inactive disease (ID) to Wk104 were assessed among BKZ-randomised pts who achieved each respective outcome at Wk16, pooled across studies. Presented data use non-responder imputation (NRI), multiple imputation (MI) and worst category imputation (WCI; ASDAS only). Observed case (OC) data also reported. Treatment-emergent adverse events (TEAEs) to Wk104 are reported for pts who received >=1 BKZ dose, including pts who switched from PBO to BKZ at Wk16.

Results. Overall, 128 and 221 pts were randomised to BKZ in BE MOBILE 1 and 2, respectively (N=349). High proportions of Wk16 responders maintained their responses at Wk104 (Figure). At Wk16, 160 (45.8%) pts achieved ASAS40; increasing to 180 (51.6%) pts at Wk104 (NRI). Of pts who achieved ASAS40 at Wk16, 85.7% maintained this response at Wk104 (MI). At Wk16, ASAS PR was achieved by 86 (24.6%) pts; this increased to 100 (28.7%) pts at Wk104 (NRI). Of pts who achieved ASAS PR at Wk16, 76.8% also achieved this outcome at Wk104 (MI; Figure). ASDAS LDA was achieved by 152 (43.6%) pts at Wk16; this increased to 172 (49.3%) at Wk104 (NRI). Of pts who achieved ASDAS LDA at Wk16, 89.3% also achieved this outcome at Wk104 (MI). ASDAS ID was achieved by 58 (16.6%) pts at Wk16; this increased to 88 (25.2%) at Wk104 (NRI). Of pts who achieved ASDAS ID at Wk16, 76.0% achieved this outcome at Wk104 (MI; Figure). Through Wk104, 514/574 (89.5%; exposure-adjusted incidence rate per 100 pt-years [EAIR/100 PY]: 141.9) pts had >=1 TEAE whilst receiving BKZ; 72 (12.5%; EAIR/100 PY: 5.4) had serious TEAEs. 39 (6.8%; EAIR/100 PY: 2.8) pts discontinued BKZ due to TEAEs.

Conclusions. Using the most critical statistical methodology (NRI or WCI; MI), BKZ maintained stringent clinical responses from Wk16 to Wk104 in axSpA. No new safety signals were observed.