Background: SB5, a biosimilar to reference adalimumab (ADL), received EU marketing authorisation in August 2017, based on the totality of evidence from pre-clinical and clinical Phase I and III studies that demonstrated bioequivalence, similar efficacy, and comparable safety and immunogenicity to the reference. This real-world study provides data on outcomes of the transition from reference to biosimilar ADL outside the controlled, randomised, clinical trial setting.

Objectives: To evaluate candidate predictors of persistence on SB5 in EU patients (pts) across multiple indications.

Methods: This ongoing observational study enrolled 1000 pts with rheumatoid arthritis (RA), axial spondyloarthritis (axSpA), psoriatic arthritis (PsA), ulcerative colitis, or Crohn’s disease who initiated SB5 as part of routine clinical practice following a minimum of 16 weeks’ treatment with reference ADL, at clinics in Belgium, Germany, Ireland, Italy, Spain, and the UK. Data are captured from clinic records retrospectively for the 24 weeks prior to transition, and prospectively and/or retrospectively for 48 weeks following transition. Primary outcome measures include baseline clinical characteristics, disease activity scores and clinical management over time; data on COVID-19 infection has recently been captured. This interim analysis (IA) provides an overview of baseline characteristics, disease scores and dose regimen up to 48 weeks post-initiation of SB5, and COVID-19 infection reported to date, in subjects with RA, axSpA, or PsA enrolled at 35 specialist sites and followed up to the data extract date of 18^th December 2020.

Results: Of the 504 pts included in this IA, 201 have RA, 169 have PsA, and 134 axSpA. At time of data extract, 216 pts had completed 48 weeks on SB5, 73 pts had discontinued SB5, and 8 had discontinued the study.

Conclusion: This IA provides a first insight into clinical management of pts over 48 weeks, in a contemporary cohort of EU pts with established RA, axSpA and PsA, switched from reference to biosimilar ADL SB5 in clinical practice. The majority of pts showed no meaningful difference in disease score or dose regimen of SB5 by Week 48 post-transition. As of data extract date, the proportion of pts with a known positive COVID-19 test was low (1.3%) and a small minority (1.3%) had SB5 treatment changed or interrupted as a result of the COVID-19 pandemic. With follow-up of pts ongoing to Q4 2021, the study will continue to provide pertinent information about clinical outcomes of transition from reference to biosimilar ADL in real-world practice and in indications not investigated in controlled studies.

Acknowledgements: Statistical services gave been provided by FGK Clinical Research GmbH, Munich, Germany. Data management services were provided by Worldwide Clinical trial, Research Triangle Park, NC, USA; funding was provided by Biogen International GmbH.

Disclosure of Interests: Ulf Müller-Ladner Consultant of: Biogen, Grant/research support from: Biogen, Karl Gaffney Consultant of: AbbVie, Celgene, Gilead, Lilly, MSD, Novartis, Pfizer, and UCB, Grant/research support from: AbbVie, Celgene, Gilead, Lilly, MSD, Novartis, Pfizer, and UCB, Deepak Jadon Consultant of: AbbVie, Celgene, Eli Lilly, Gilead, Janssen, MSD, Novartis, Oxford University Press, Pfizer, Roche, Sandoz, UCB, Grant/research support from: AbbVie, Celgene, Eli Lilly, Gilead, Janssen, MSD, Novartis, Oxford University Press, Pfizer, Roche, Sandoz, UCB, Ulrich Freudensprung Shareholder of: Biogen, Employee of: Biogen, Janet Addison Shareholder of: Biogen, Employee of: Biogen