FRI0103 One-year follow-up of a nationwide cohort of patients with inflammatory arthritis, who switched from originator to biosimilar etanercept, focusing on patients who switched back to originator. an observational danbio study

Background In Denmark, patients (pts) treated with originator etanercept (ETA) 50 mg SC conducted a mandatory non-medical switch to biosimilar SB4 in April 2016 ( switchers). Pts treated with 25 mg ETA or 50 mg powder-solution were not mandated to switch ( non-switchers). Some switchers resumed ETA during follow-up ( back-switchers) . Objectives To investigate the frequency of back-switching after the non-medical switch from ETA to SB4, and in back-switchers to study , 1) baseline characteristics at the time of initial switch (ETA->SB4), 2) reasons for SB4 withdrawal, 3) changes in disease activity during treatment with SB4 and after back-switching. Methods Patient data were retrieved from the DANBIO registry (censored August 2017). For back-switchers, disease activity at the start of SB4 (=baseline) and at the time of back-switching to ETA were compared, and changes in disease activity between the two time points were calculated (=delta values), stratified by indication (RA/PsA/AxSpA). Baseline characteristics of back-switchers were compared to the rest of the switch population (Chi-sq, Mann-Whitney U-test). Abbreviations are shown in table 1. Results 1641 pts switched from ETA to SB4. Of these, 299 (18%) withdrew SB4 therapy during 1 year follow-up and either switched back to ETA (n=120, 7%), started another bDMARD (n=104), died (n=9), were lost to follow-up (n=1) or did not re-start bDMARDs (n=65). Among the 120 back-switchers, SB4 was withdrawn due to LOE (52%), AE (39%), or other/unknown reasons (9%). The reasons for withdrawal of SB4 in back-switchers are listed in table 1. No major safety events occurred. The median time on SB4 before back-switching was 120 (IQR 73–193) days, and the time between stop of SB4 and re-start of ETA was 1 1–1 days. Baseline characteristics of back-switchers vs the rest of the switch population were similar (all p>0.05). Among back-switchers who stopped SB4 due to LOE, PGA increased during SB4 treatment, whereas CRP and SJC were largely unchanged (table 1). At the date of censoring, 104/120 back-switchers (87%) were still treated with originator ETA (median treatment duration 236 (155–302) days). Conclusions In a nationwide cohort of 1621 arthritis patients that were switched from ETA to SB4, 7% switched back to ETA. Back-switchers had no distinct clinical or disease characteristics upon start of SB4. AEs prior to back-switching were largely unspecific. In pts who withdrew SB4 due to LOE, PGA had increased. Reasons for back-switching appeared to be predominantly subjective rather than objective (nocebo effect). Originator drug was still available (25 mg or 50 mg powder-solution), which may have encouraged back-switching. References [1] Glintborg, et al. Arthritis Rheum2017;69(suppl 10). [2] Glintborg, et al. Abstract, EULAR2018. Acknowledgements Partly sponsored by Biogen Disclosure of Interest B. Glintborg Grant/research support from: Abbvie, Biogen, Pfizer, I. Sorensen: None declared, E. Omerovic: None declared, F. Mehnert: None declared, N. Manilo: None declared, K. Danebod: None declared, D. Jensen: None declared, H. Nordin: None declared, A. G. Loft Grant/research support from: AbbVie, MSD, Novartis, Pfizer, Roche, UCB, O. Hendricks Grant/research support from: Abbvie, Roche, Novartis, S. Chrysidis: None declared, B. Andersen: None declared, J. Raun: None declared, H. Lindegaard: None declared, J. Espesen: None declared, S. Jakobsen: None declared, I. M. Hansen Grant/research support from: Roche, E. Dalsgaard: None declared, D. Pedersen: None declared, S. Kristensen: None declared, A. Linauskas: None declared, L. Andersen: None declared, J. Grydehoj: None declared, N. Krogh: None declared, M. Hetland Grant/research support from: Abbvie, Biogen, BMS, CellTrion, MSD, Novartis, Orion, Pfizer, Samsung, UCB