Background Limited data exist on the effect of biologics in slowing radiographic progression in patients (pts) with radiographic axial spondyloarthritis (r-axSpA). Two-year data from MEASURE 1 showed low radiographic progression with secukinumab (SEC).^[1]

Objectives To compare the effect of SEC vs adalimumab biosimilar (SDZ-ADL) on spinal radiographic progression from SURPASS,^[2,3] the first head-to-head study in r-axSpA.

Methods In this phase IIIb study, bio-naïve pts with active r-axSpA with a BASDAI ≥4, spinal pain score ≥4 (range 0–10), total back pain score ≥40 mm (range 0–100 mm), and with hs-CRP ≥5 mg/L or ≥1 syndesmophyte(s) on spinal radiograph were randomised (1:1:1) to SEC (150/300 mg; dose-blinded) or SDZ-ADL (40 mg; open label). Radiographs and MRIs were reviewed by 3 independent central readers (no adjudication performed) blinded to treatment and chronology of images. Primary endpoint was the proportion of pts with no radiographic progression (change from baseline [CFB] in modified Stoke AS Spinal Score [mSASSS] ≤0.5) on SEC vs SDZ-ADL at week (wk) 104 (superiority testing). Secondary endpoints included CFB-mSASSS at wk 104, proportion of pts with ≥1 syndesmophyte(s) at baseline (BSL) with no new syndesmophytes(s) at wk 104, CFB-MRI Berlin sacroiliac joint (SIJ) inflammation score, CFB-AS Spine MRI-activity (ASspiMRI-a) Berlin modification score, and safety.

Results Overall, 859 pts received SEC 150 mg (n=287), 300 mg (n=286), or SDZ-ADL (n=286). With 78.5% male, mean age 42.1 years, mSASSS 16.6, BASDAI 7.1, hsCRP 20.4 mg/L, and 73% with ≥1 syndesmophyte(s), this population had high risk of radiographic progression. At wk 104, cumulative distribution of CFB-mSASSS was similar across arms (Figure 1). Proportion of pts with no radiographic progression was 66.1%, 66.9%, and 65.6% (P=ns, both SEC doses) while mean CFB-mSASSS was 0.54, 0.55, and 0.72 with SEC 150 mg, 300 mg, and SDZ-ADL. Overall, 56.9%, 53.8%, and 53.3% of pts in SEC 150 mg, 300 mg, and SDZ-ADL arms, with a BSL ≥1 syndesmophyte(s) did not develop new syndesmophyte(s) by wk 104 (Table 1). In the MRI sub-set (N=418), mean SIJ scores at BSL and wk 16 were 2.54 and 0.98 (SEC 150 mg), 1.96 and 0.92 (SEC 300 mg), and 1.59 and 0.38 (SDZ-ADL); corresponding spine scores were 3.50 and 1.79, 2.56 and 1.25, and 3.00 and 0.71.

Conclusion Spinal radiographic progression over 2 years was low with no significant difference between SEC and SDZ-ADL arms. No new safety signals were identified.

References [1]Braun J et al. Ann Rheum Dis. 2017;76(6):1070-77

[2]Baraliakos X et al. Clin Drug Investig. 2020;40(3):269-78

[3]Baraliakos X et al. Arthritis Rheumatol. 2022;74 (suppl 9)

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Acknowledgements: NIL.

Disclosure of Interests Xenofon Baraliakos Speakers bureau: AbbVie, BMS, Celgene, Chugai, Merck, Novartis, Pfizer, UCB, Grant/research support from: AbbVie, BMS, Celgene, Chugai, Merck, Novartis, Pfizer, UCB, Consultant for: AbbVie, BMS, Celgene, Chugai, Galapagos, Merck, Novartis, Pfizer, UCB, Mikkel Østergaard Speakers bureau: Abbvie, BMS, Boehringer-Ingelheim, Celgene, Contocor, Eli-Lilly, Hospira, Janssen, Merck, Mundipharma, Novartis, Novo Nordisk, Orion, Pfizer, Regeneron, Roche, Schering-

Plough, Takeda, UCB and Wyeth, Consultant of: Abbvie, BMS, Boehringer-Ingelheim, Celgene, Contocor, Eli-Lilly, Hospira, Janssen, Merck, Mundipharma, Novartis, Novo Nordisk, Orion, Pfizer, Regeneron, Roche, Schering-

Plough, Takeda, UCB and Wyeth, Grant/research support from: Abbvie, BMS, Boehringer-Ingelheim, Celgene, Contocor, Eli-Lilly, Hospira, Janssen, Merck, Mundipharma, Novartis, Novo Nordisk, Orion, Pfizer, Regeneron, Roche, Schering-

Plough, Takeda, UCB and Wyeth, Denis Poddubnyy Speakers bureau: AbbVie, BMS, Lilly, MSD, Novartis, Pfizer, UCB, Consultant of: AbbVie, Biocad, BMS, Eli Lilly, Gilead, MSD, Novartis, Pfizer, Samsung Bioepis, UCB, Grant/research support from: AbbVie, Eli Lilly, MSD, Novartis, Pfizer, Désirée van der Heijde Consultant of: Personal fees from Novartis, AbbVie, Bayer, BMS, Cyxone, Eisai, Galapagos, Gilead, Glaxo-Smith-Kline, Janssen, Lilly, Pfizer, UCB Pharma, and Director of Imaging Rheumatology bv, Atul Deodhar Speakers bureau: AbbVie, Eli Lilly, Janssen, Novartis, Pfizer, and UCB, Consultant of: AbbVie, Amgen, Aurinia, Bristol-Myers Squibb, Celgene, Eli Lilly, GSK, Janssen, Moonlake, Novartis, Pfizer, and UCB, Grant/research support from: AbbVie, Bristol Myers Squibb, Celgene, Eli Lilly, GSK, Janssen, Novartis, Pfizer, and UCB, Pedro Machado Speakers bureau: Abbvie, BMS, Celgene, Eli Lilly, Galapagos, Janssen, MSD, Novartis, Orphazyme, Pfizer, Roche and UCB, Consultant of: Abbvie, BMS, Celgene, Eli Lilly, Galapagos, Janssen, MSD, Novartis, Orphazyme, Pfizer, Roche and UCB, Victoria Navarro-Compán Speakers bureau: Abbvie, BMS, Eli Lilly, Galapagos, Janssen, Moonlake, MSD, Novartis, Pfizer, Roche and UCB, Consultant of: Abbvie, BMS, Eli Lilly, Galapagos, Janssen, Moonlake, MSD, Novartis, Pfizer, Roche and UCB, Kay-Geert Hermann Consultant of: AbbVie, lecture fees from MSD, Novartis, Pfizer. Co-founder of BerlinFlame GmbH, Mitsumasa Kishimoto Consultant of: AbbVie, Amgen, Asahi-Kasei Pharma, Astellas, Ayumi Pharma, BMS, Celgene, Chugai, Daiichi-Sankyo, Eisai, Eli Lilly, Gilead, Janssen, Kyowa Kirin, Novartis, Ono Pharma, Pfizer, Tanabe-Mitsubishi, and UCB Pharma (consulting fees and/or honoraria), Eun Young Lee Consultant of: Immonoforge and IMbiologics, Lianne S. Gensler Consultant of: Gilead, Eli Lilly, Janssen, MoonLake, Novartis, Pfizer and UCB, Grant/research support from: Novartis, UCB, and Pfizer, Uta Kiltz Consultant of: AbbVie, Biocad, Biogen, Chugai, Eli Lilly, Fresenius, Grünenthal, GSK, Hexal, Janssen, MSD, Novartis, Pfizer, Roche and UCB, Grant/research support from: AbbVie, Biocad, Biogen, Chugai, Eli Lilly, Fresenius, GSK, Grünenthal, Hexal, Janssen, MSD, Novartis, Pfizer, Roche and UCB, Marco Eigenmann Shareholder of: Novartis, Employee of: Novartis, Patricia Pertel Shareholder of: Novartis, Employee of: Novartis, Aimee Readie Shareholder of: Novartis, Employee of: Novartis, Hanno Richards Shareholder of: Novartis, Employee of: Novartis, Brian Porter Shareholder of: Novartis, Employee of: Novartis, Juergen Braun Consultant of: Personal fees from: Abbvie, Amgen, Boehringer, Celltrion, MSD, Novartis, UCB, and Eli Lilly.