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THU0196 Do contextual factors influence survival ondrug of biosimilars in clinical practice?

Background The introduction of biosimilars has been linked to concerns regarding their effectiveness and safety compared to their originator products. Whilst randomized controlled trials may address their relative efficacy, the outcome of biosimilars in clinical practice may be influenced by contextual factors, such as the treating rheumatology unit’s experience with biosimilars and non-medical switching. Objectives To analyze whether contextual factors, such as department size and use of biosimilars, and calendar period of treatment start, influence time until treatment discontinuation (i.e. drugsurvival) of biosimilars as compared to corresponding originator products. Methods We used data from the Swedish Rheumatology Quality register to identify all patients with rheumatoidarthritis, ankylosing spondylitis, psoriatic arthritis, or other spondyloarthropathies who started infliximab between March 1st 2015 and Sept 30th 2017 or etanercept between April 1st 2016 and Sept 30th 2017, as their firstever biologic. Kaplan-Meier curves and Cox models were used to assess the association between drug survival and the size of the rheumatology unit, itsuse of biosimilars (extent of biosimilar use above/below national median a teach time point), and whether the treatment start occurred soon after biosimilar introduction (infliximab: first 12 months, etanercept: 6 months counting from first date of availability of the biosimilar in question). To avoid artefacts, patients were censored if switching from the originator to a biosimilar (or vice versa). Results During the study period, 368 and 738 patients started infliximab originator or biosimilar, and 125 and 2079 started etanercept originator or biosimilar, as first ever biological treatment. Overall, the hazard ratio (HR) of discontinuing treatment (comparing the biosimilar vs its originator) was 1.21 (95% CI: 0.96–1.51) for infliximab and 0.88 (95% CI: 0.57–1.35) for etanercept, adjusted for indication, age(quartiles), gender, region, and HAQ (quartiles), DAS28 (quartiles) and globalhealth (quartiles) at treatment start. Patients treated in large clinics (more than 1695 patients (75th percentile) at the end of the study period) were at a lower risk of drug discontinuation (table 1). We noted no association between overall biosimilar use in the rheumatology clinic in question and survival on drug (neither originator nor biosimilar). By contrast, those who started infliximab biosimilar later had a lower risk of discontinuing (HR: 0.65 (95% CI:0.50–0.85)) compared to those who started in the first year of availability. For etanercept biosimilar, no such association was noted. Abstract THU0196 – Table 1 Hazardratios among patients starting their first biologic treatment during the studyperiod according to contextual factors *Additionally adjusted for department size and use of biosimilar;§ Only 2 discontinuation in the later period of etanercept originator Conclusions Contextual factors, presumably related to expectations and differences in clinical monitoring, influence the observed survival on drug of biologics, including biosimilars, and must be considered when the comparative effectiveness of biosimilars is evaluated. Disclosure of Interest D. DiGiuseppe: None declared, T. Frisell: None declared, E. Lindqvist: None declared, L. Jacobsson Consultant for: received lecture and consulting fees from Pfizer, Abbvie and Novartis, C. Turesson Grant/research support from: Abbvie, Bristol Myers-Squibb, Roche, Consultant for: MSD, Bristol Myers-Squibb, Roche, Paidinstructor for: Abbvie, Bristol-Myers Squibb, Janssen, MSD, Pfizer, Roche and UCB, C. Sjöwall: None declared, J. Askling Grant/research support from: has orhas had research agreements with Abbvie, BMS, MSD, Pfizer, Roche, Astra-Zeneca, Eli Lilly, Samsung Bioepis, and UCB, mainly in the context of safety monitoring of biologics via ARTIS. Karolinska Institutet has received remuneration for JA participating in advisory boards arranged by Pfizer and Eli Lilly.