POS0823 UPTAKE OF INFLIXIMAB BIOSIMILARS AMONG U.S. RHEUMATOLOGY PRACTICES THROUGH 2022

Abstract

BackgroundThe first infliximab biosimilar (infliximab-dybb) entered the U.S. market in 2016 and two additional products are now available (infliximab-axxq and infliximab-abda). Biosimilars have significant potential to slow drug spending; however, biosimilar uptake in the U.S. has lagged. Little is known about the impact of additional infliximab biosimilar approvals on market penetration or about patterns of use among rheumatologists.ObjectivesWe used the national RISE registry 1) to examine uptake of infliximab biosimilars between 2016 and 2022 and 2) to study physician prescribing of these drugs. For the latter, we analyzed patterns of biosimilar drug use across a national sample of practices and analyzed characteristics of patients who were prescribed biosimilars vs. bio-originator infliximab.MethodsData from RISE, a national registry that includes electronic health records from one-third of U.S. rheumatology practices, was used. All bio-originator or biosimilar infliximab administrations (of any dose) between April 2016 and March 2022 were analyzed. We included patients 18 years or older who had at least one visit with a rheumatologist; all infliximab bio-originator or biosimilar users, regardless of diagnosis, were included. To assess the uptake of biosimilar infliximab, we examined the proportion of patients using each formulation (infliximab, infliximab-dybb, infliximab-abda and infliximab-axxq) in 2-month intervals during the study period. Patients were included in multiple time windows if they received different products during the study period. Next, we examined practice-level uptake of biosimilars among practices with ≥ 20 new infliximab users after 2019. Finally, we examined the characteristics of patients who were prescribed biosimilars. For this analysis, we calculated standardized mean differences (SMDs) to permit comparisons of the characteristics of users of bio-originator infliximab and each biosimilar. In cases where more than one infliximab product was prescribed, patients were classified based on their most recent infliximab prescription.ResultsDuring the study period, 32,916 individuals used bio-originator infliximab, 3,999 used infliximab-dybb, 1,369 used infliximab-abda, and 1,099 used infliximab-axxq.Figure 1demonstrates that uptake of biosimilar infliximab formulations remained below 20% and rose only minimally with the introduction of new biosimilar formulations in 2017 and 2020. Among 102 rheumatology practices with ≥ 20 new infliximab users, we observed significant variability in biosimilar use. 16.6% of practices had no patients on biosimilars, 27.4% had between one and ten percent of patients on biosimilars; only 15.6% had more than half of patients on biosimilars. SMDs for age, sex, race and ethnicity, insurance, region, and rheumatic disease diagnosis were all ≤0.5, indicating only small differences in patient characteristics across different formulation groups when comparing bio-originator infliximab to biosimilar versions.ConclusionUptake of biosimilar infliximab drugs has been slow and minimally impacted by the introduction of additional biosimilar formulations in the U.S over the last six years. Only a small percentage of rheumatology practices use biosimilars for most patients, and a substantial proportion do not use biosimilars at all. We noted only small differences in patient characteristics between bio-originator and biosimilar infliximab users, suggesting that patient demographic characteristics, geographical region, diagnosis and insurance are not major drivers of prescribing differences. These findings suggest that in the absence of mandatory switching policies or other incentives, the U.S. has largely failed to achieve a robust biosimilars market, stymieing efforts to increase competition and reduce cost.Figure 1.Proportion of patients in the RISE registry using infliximab bio-originator or biosimilars between 2016 and 2022.AcknowledgementsThis data was supported by the ACR’s RISE Registry. However, the views expressed represent those of the authors, not necessarily those of the ACR.Disclosure of InterestsJinoos Yazdany Consultant of: Aurinia, Astra Zeneca, Pfizer, Grant/research support from: Gilead, Genentech, Aurinia, Astra Zeneca, Jing Li: None declared, Eric Roberts: None declared, Rachael Stovall: None declared, Gabriela Schmajuk: None declared.