BackgroundAccording to national guidelines issued in 2015, a non-medical switch from originator infliximab (IFX) (Remicade) to biosimilar Remsima was conducted in all Danish patients with inflammatory rheumatic diseases treated in routine care.ObjectivesTo investigate 3 months' clinical outcomes in Remicade-treated patients (pts) with rheumatoid arthritis (RA), psoriatic arthritis (PsA) and axial spondyloarthrits (SpA) who switched to Remsima and were monitored prospectively in the DANBIO registry.MethodsDisease activity at 3 mths before switch (pre-switch), at the switch and after 3 mths (70–120 days) (post-switch) and changes over time (Δpre-switch and Δpost-switch) were calculated. Disease flare was defined as ΔDAS28≥1.2 (RA/PsA) or ΔASDAS≥1.3 (SpA). Reasons for withdrawal (adverse events (AE), lack of effect (LOE) or other) were registered.Results647 of 693 switching pts (300 RA, 96 PsA, 219 SpA, 32 other) had available data (52% women, age (median (IQR) 56 (45–66) yrs)). Prior Remicade treatment duration was 6.7 (4.1–9.4) yrs and in 77% it was the first biological treatment. Remsima dose was in RA+PSA 3.3 (3.0–4.8) mg/kg every 7 (6–8) wks and in SpA 4.8 (3.6–5.1) mg/kg every 6 (6–9) wks. Concomitant MTX was given in 69% (RA+PsA)/25% (SpA). Median follow-up time was 139 (98–160) days.Disease activity remained largely unchanged 3 months prior to vs. after the switch (Table). The proportion of patients with disease flare pre-/post switch was 10%/10% (RA+PsA) (p=1.0) and 10%/0% (SpA) (p=1.0) (related samples McNemar test).Overall, 45 ptts (7%) stopped Remsima treatment during follow-up (AE 16 (allergic 3, infection 2, rash 2, unspecific 9), LOE 20, remission 3, cancer 2, other 4). Prior Remicade treatment duration in these patients was 5.9 (3.5–9.1) yrs.Table 1Disease activity, median (IQR)Delta-values, median (IQR)P*3 monthsSwitch3 monthsPre-switchPost-switchpre-switchpost-switchRA/PSA DAS282.3 (1.8–3.0)2.3 (1.8–3.2)2.3 (1.9–3.2)0.0 (−0.3–0.5)0.1 (−0.2–0.5)0.07 HAQ0.6 (0.1–1.1)0.6 (0.1–1.1)0.5 (0.3–1.1)0.0 (0.0–0.1)0.0 (−0.1–0.1)0.5 CRP, mg/l4 (2–7)4 (2–8)6 (3–9)0 (−2–1)0 (−1–3)0.03 VAS pt's global, mm26 (11–52)27 (11–56)26 (11–55)0 (−7–8)0 (−7–9)0.04SpA BASDAI, mm26 (12–47)23 (7–41)23 (7–41)0 (−4–5)0 (−3–3)0.5 CRP, mg/l4 (1–8)2 (1–5)5 (1–9)0 (−2–2)0 (−2–2)0.5 VAS pt's global, mm28 (15–57)31 (15–56)24 (10–52)1 (−4–8)−2 (−9–2)0.3 ASDAS2.0 (1.3–2.7)1.9 (0.7–3.2)1.8 (1.2–2.7)0.0 (−0.3–0.5)0.0 (−0.4–0.2)0.8*Delta values for disease activity pre-switch vs. post-switch, Wilcoxon matched-pair signed rank test.ConclusionsIn 647 patients with inflammatory rheumatic diseases treated with Remicade for >4 years, disease activity was largely unaffected in the majority of patients 3 months after non-medical switch to biosimilar Remsima and comparable to the fluctuations observed in the 3 months prior to the switch. However, several patients (∼6%) stopped treatment due to LOE or AE. This warrants further investigation before such a non-medical switch can be recommended.Disclosure of InterestNone declared