POS0874 COMPARABLE SAFETY AND EFFECTIVENESS AMONG NEW USERS OF BIOSIMILAR VS ORIGINATOR ANTI-TNFS IN INFLAMMATORY ARTHRITIS: POPULATION-BASED EVIDENCE FROM A POLICY CHANGE
Authors: D. Lacaille, K. Moolooghy, J. A. Aviña-Zubieta, Y. Zheng, N. Lu, H. Xie
Journal: Annals of the Rheumatic Diseases (2024)

<h3>Background:</h3> British Columbia's (BC) health policy mandated that, for medication cost to be covered under the universal drug plan, all new biologics initiations after 06/2017 use biosimilars when available, providing the context for a natural experiment. <h3>Objectives:</h3> Our study objective was to compare infections, healthcare resource utilization (HRU) and use of other medications for inflammatory arthritis (IA), as surrogate markers of safety and effectiveness, after initiation of etanercept or infliximab for IA in new users of biosimilars versus originators, using historical controls pre-policy change. <h3>Methods:</h3> We identified all incident users of a new biologic (i.e., without prescriptions over the prior 6 months) for rheumatoid arthritis (RA), psoriasis or psoriatic arthritis (Pso/PsA), or ankylosing spondylitis (AS) in BC, using administrative health data. The biosimilar cohort included incident users starting etanercept or infliximab between 07/01/2017 and 12/31/2019, followed until 12/31/2020 (post-policy period). Historical controls included all incident users starting etanercept/infliximab originators between 01/01/2014 and 06/30/2016, followed until 06/30/2017 (pre-policy period). To control for temporal trends, we selected new users of adalimumab (no biosimilar available over those periods) as comparators. Outcomes included severe infections (hospitalization with infection diagnostic code in any position); mild infections (oral/IV antibiotics without hospitalization); number of hospitalizations (any cause), physician and emergency department visits; hospital length of stay; and use of IA medications (daily dose, cumulative dose, proportion of follow-up days on drug, and number (%) of baseline users who discontinued and baseline non-users who initiated methotrexate (MTX) and glucocorticoids (GC)). People were followed for up to 3 years from anti-tumor necrosis factor (anti-TNF) initiation until discontinuation, death, moving out-of-province, or follow-up end, whichever occurred first. Quasi Poisson models were used for estimating the adjusted rate ratio (aRR) of count outcomes (infections and HRU), logistic regression models for estimating adjusted odds ratios (aOR) of proportion of days on drugs, discontinuation and initiation outcomes, and linear regression models for estimating adjusted mean difference in daily and cumulative doses of IA drugs, with propensity overlap weights to control for imbalanced potential confounders. To control for temporal trends, we employed the difference-in-difference (DID) method, comparing the aRRs (or aORs or adjusted mean dose difference) for each outcome among new users of biosimilar versus originator etanercept/infliximab with those among new users of adalimumab post- versus pre-policy change, expressed as the ratio of the two aRRs (or aORs) or differences in the adjusted mean dose difference. <h3>Results:</h3> Our sample includes 827 biosimilar etanercept users (RA:576, AS:171, Pso/PsA:80) and 271 infliximab users (RA:150, AS:54, Pso/PsA:67); 1312 etanercept and 230 infliximab originator users; and 2213 adalimumab originator users post- and 1773 pre-policy change (Table 1). After adjusting for baseline covariates and accounting for temporal trends by comparing with adalimumab users over the same time periods (Table 2), there were no major differences in infections, HRU or pattern of other IA drug use. Small differences of unclear clinical significance were observed, with slightly lower rates of some outcomes observed in biosimilar users (mild infections with infliximab &amp; etanercept, hospitalization with etanercept; and family physician visits with infliximab) (Table 2) <h3>Conclusion:</h3> Real-world population-based data showed that incident users of biosimilar etanercept and infliximab did not have higher rates of infections, HRU and use of IA medications compared to originators, suggesting comparable safety and effectiveness for IA and no unintended adverse consequences from the health policy. <h3>Acknowledgements:</h3> 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 &amp; 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. <h3>Disclosure of Interests:</h3> Diane Lacaille Dr Lacaille has received grant support for investigator initiated research from Biocon, Organon, Fresenius Kabi, Pfizer., Kasra Moolooghy: None declared, J. Antonio Aviña-Zubieta has received grant support for investigator initiated research from Janssen., Yufei Zheng: None declared, Na Lu: None declared, Hui Xie: None declared