Ab0192 Comparable Safety and Effectiveness After Transition to a Biosimilar Anti-TNF in Inflammatory Arthritis: Population-Based Evidence From a Policy Change

Background: British Columbia's (BC) health policies mandated that, for medication cost to be covered under the universal drug plan, all new biologics initiations after June 2017 use biosimilars when available, and in May-December 2019, that current users of etanercept and infliximab for inflammatory arthritis (IA) transition to the corresponding biosimilar, providing the context for a natural experiment. Objectives: Our study objective was to compare infections and healthcare resource utilization (HRU), as surrogate markers of safety and effectiveness, between biosimilar switchers versus originator etanercept or infliximab users for IA, after and before the health policy change. Methods: We identified etanercept and infliximab users for rheumatoid arthritis (RA), psoriasis or psoriatic arthritis (Pso/PsA), or ankylosing spondylitis and other spondyloarthritis (AS) in BC, using administrative health data. Biosimilar switchers were current biologic users who transitioned to the corresponding biosimilar during the period of May to December 2019. Historical controls were randomly selected from all new users of originator etanercept and infliximab before July 2017, matched to biosimilar switchers on age, sex, previous number of biologics used, and IA disease. Controls were assigned an index date (date of switching) such that duration on originator anti-tumor necrosis factor (anti-TNF) was the same at index date for switchers and matched controls. Outcomes included number of severe infections (hospitalization with infection diagnostic code in any position); mild infections (oral/IV antibiotics without hospitalization); hospitalizations (any cause), physician and emergency department visits; and hospital length of stay (LOS). We followed patients from switching/index date for up to 2 years or until discontinuation, moving out-of-province, or end of follow-up (04/30/2019 for originators and 12/31/2021 for switchers), whichever occurred first. Quasi-Poisson Models estimated the adjusted rate ratio (aRR) of each outcome, with propensity overlap weights to control for imbalanced potential confounders, namely, age, sex, socio-economic status, rural vs. urban residence, health authority, arthritis type, number of prior biologic agents, duration of anti-TNF use at switch/index date, comorbidities, and other IA drugs used (glucocorticosteroids, MTX and non-MTX csDMARDs), measured at switching/index date. To account for the potential impact of the COVID-19 pandemic on infection risk and HRU, we conducted a sensitivity analysis excluding study participants who transitioned to a biosimilar after October 1, 2019, and censoring follow-up time at March 31, 2020. Results: Our sample includes 1631 biosimilar switchers/controls (1402 etanercept; 229 infliximab): 556 (67.2%) RA, 178 (21.5%) AS, 93 (11.2%) Pso/PsA patients (Table 1). Higher risk of rheumatologist visits and lower risk of infections and HRU were observed in biosimilar users (Table 2). No significant differences were observed in the sensitivity analyses censored for COVID-19, except for higher rheumatologist visits in biosimilar infliximab users, and lower mild infections and hospital LOS in biosimilar etanercept users. Conclusion: Real-world population-based data from BC's health policy mandating transition from originator to biosimilar etanercept and infliximab for IA showed that biosimilar transition was not associated with higher rates of infections and HRU compared to continuing originator medications, suggesting comparable safety and effectiveness for use in IA and no unintended adverse consequences from the health policy. REFERENCES: NIL. Acknowledgements: This research was funded by a grant from the Canadian Rheumatology Association via CIORA (Canadian Initiative for Outcomes in Rheumatology Care). Dr. Lacaille is supported by the Mary Pack Chair in Arthritis Research from the University of British Columbia and The Arthritis Society of Canada. Dr. Antonio Avina Zubieta is a BC Lupus Society Research Scholar and a Walter & Marilyn Booth Research Scholar. Dr. Hui Xie is supported by the Milan Ilich/Merck Chair in Statistics for Arthritis and Musculoskeletal Diseases from Simon Fraser University. Disclosure of Interests: Diane Lacaille has received grant support for investigator initiated research from Biocon, Organon, Fresenius Kabi, Pfizer., Kasra Moolooghy has received grant support for investigator initiated research from Janssen., J. Antonio Aviña-Zubieta: None declared, Yufei Zheng: None declared, Na Lu: None declared, Hui Xie: None declared.