PO:01:011 | Achievement of Remission Defined by Absence of Objective Signs of Inflammation Versus ASDAS ID in Patients with Active Axial Spondyloarthritis Treated with Bimekizumab: 52-Week Results from Two Phase 3 Studies

Lianne S Gensler¹, Helena Marzo-Ortega², Vanessa Taieb³, Diana Voiniciuc⁴, Alexander Marten⁵, George Stojan⁶, Mindy Kim⁶, Paolo Marsico⁷, Martin Rudwaleit⁸ | ¹Department of Medicine/Rheumatology, University of California San Francisco, USA; ²NIHR Leeds Biomedical Research Centre, University of Leeds Leeds, United Kingdom; ³UCB Colombes, France; ⁴UCB Slough, United Kingdom; ⁵UCB Monheim am Rhein Germany; ⁶UCB Atlanta, USA; ⁷UCB Milan, Italy; ⁸University of Bielefeld, Klinikum Bielefeld Bielefeld Germany

Purpose of the Work. Bimekizumab (BKZ), a monoclonal antibody that selectively inhibits interleukin (IL)-17F in addition to IL-17A, has shown sustained efficacy and safety to Week (Wk)104 in patients (pts) across the full spectrum of axial spondyloarthritis (axSpA) in the phase 3 studies BE MOBILE 1 (non-radiographic [nr-]axSpA) and 2 (radiographic [r-]axSpA), and their open-label extension.[1] Achievement of remission is a treatment goal and may guide clinical decisions.[2] We report achievement of remission defined using objective signs of inflammation (OSI) in axSpA pts versus an established measure of remission, Axial Spondyloarthritis Disease Activity Score <1.3 (ASDAS Inactive Disease [ID]).

Materials and Methods. BE MOBILE 1 (nr-axSpA; NCT03928704) and 2 (r-axSpA; NCT03928743) comprised a 16-wk double-blind, placebo (PBO) controlled period followed by 36-wk maintenance period. Pts were randomised to subcutaneous BKZ 160mg every 4 wks (Q4W) or PBO, all pts received BKZ from Wk16. Remission of OSI comprised MRI remission of the sacroiliac joints (SIJ) and spine (MRI Spondyloarthritis Research Consortium of Canada [SPARCC] SIJ score <2 and Berlin MRI spine <=2), C-reactive protein (CRP) <=5 mg/L and a swollen joint count (SJC) of 0. The proportion of pts from BE MOBILE 1 and 2 MRI sub-studies achieving these criteria was compared with those achieving ASDAS ID using observed case (OC) data.

Results. 152 and 139 pts from the MRI sub-studies of BE MOBILE 1 and 2, respectively, were included. Levels of OSI at baseline were similar across treatment arms in pts with nr-axSpA and r-axSpA (Table). In pts with nr-axSpA, 32/74 (43.2%) BKZ-randomised and 11/59 (18.6%) %) PBO-randomised pts achieved Wk16 OSI remission, versus 16/74 (21.6%) and 5/59 (8.5%) achieving ASDAS ID, respectively. 32/63 (50.8%) BKZ-randomised pts and 19/54 (35.2%) PBO-randomised PBO-BKZ switchers achieved Wk52 OSI remission, versus 22/63 (34.9%) and 21/54 (38.9%) achieving ASDAS ID, respectively (Figure 1). In pts with r-axSpA, 32/79 (40.5%) BKZ-randomised and 8/44 (18.2%) PBO-randomised pts achieved Wk16 OSI remission, versus 12/79 (15.2%) and 1/44 (2.3%) achieving ASDAS ID, respectively. 38/76 (50.0%) BKZ-randomised pts and 20/39 (51.3%) PBO-to-BKZ switchers achieved Wk52 OSI remission, versus 18/76 (23.7%) and 18/39 (46.2%) achieving ASDAS ID, respectively (Figure 2).

Conclusions. Generally, a higher proportion of pts treated with BKZ achieved remission defined by the absence of OSI compared to ASDAS ID. These findings suggest that ASDAS ID could underestimate the anti-inflammatory effects of BKZ, while also highlighting a potential need for optimised endpoints to guide clinical treatment management of axSpA.