OA14a Outcomes after switching from etanercept originator to its biosimilar (SB4) for the treatment of rheumatoid arthritis

Abstract Background/Aims Following the etanercept biosimilar SB4 (ETN-B) launch in the UK in 2016, nationwide guidelines encourage patients switch from the biologic originator (ETN-O) to ETN-B, known as non-medical switching (NMS). However, the long-term implications of NMS have not yet been analysed nationally among patients with rheumatoid arthritis (RA). This analysis aims to evaluate treatment outcomes and drug retention after patients with RA are switched from ETN-O to ETN-B in routine clinical practice in the UK. Methods The British Society for Rheumatology Biologics Register for RA (BSRBR-RA) is a prospective observational cohort study. This analysis included all patients who switched from ETN-O to ETN-B since 2016. Disease activity was assessed at the time of switch and after six months. Key outcomes included change in disease activity (DAS28), DAS28 remission and EULAR treatment response. Drug retention was analysed using Kaplan-Meier and treatment withdrawal reasons were explored for all patients who switched to ETN-B, as well as (1) patients who switched-back to ETN-O, (2) patients who changed to a non-ETN biologic, (3) patients discontinuing all biologic therapy. Multiple imputation was used to account for missing data. Results 1160 patients with RA switched from ETN-O to ETN-B. Of the 919 (79%) with available DAS28 data, there was no change in six-month DAS28 score following switch (median: 0, IQR: -0.8, 0.7). After a median follow-up of 1.8 years (IQR: 1.0, 2.3), most patients remained on ETN-B (N = 844, 73%) with the main treatment withdrawal reason being ineffectiveness (N = 139, 44%). Among those who discontinued ETN-B, 133 (11%) patients switched-back to ETN-O and 98 (8%) patients changed to a non-ETN biologic; both primarily due to ineffectiveness (Table). Lastly, 85 (7%) patients discontinued all biologic therapy mainly due to adverse events (N = 50, 59%). Conclusion This analysis has demonstrated sustained effectiveness after switching from ETN-O to ETN-B using real-world nationwide data. Among the sub-cohorts of patients who discontinued ETN-B, differences were observed regarding the frequency and reasons for treatment withdrawal. These results will support UK rheumatologists and patients with treatment decisions, assist quality improvement projects to reduce drug withdrawals and refine biologic treatment delivery in the UK. Disclosure A. Rokad: None. L. Kearsley-Fleet: None. K. Watson: None. M. Lunt: None. K.L. Hyrich: Honoraria; Abbvie. Grants/research support; Pfizer, BMS.