OBJECTIVES: Despite clinically similar safety and efficacy compared to original biologics, biosimilars are not widely utilized. Real world evidence on patient characteristics and utilization trend of biologics versus biosimilars among rheumatoid arthritis (RA) patients is limited.

METHODS: This retrospective cohort study was conducted using Optum Research Database (ORD) during 01JAN2016-30JUN2022. Adults 18 years and older diagnosed with RA and continuously enrolled (CE) for at least 6 months pre and post RA diagnosis date (index date) were included. Patients were followed until initiation of infliximab-, rituximab-, etanercept-, or adalimumab-based biologics or approved biosimilars, CE end or study end. Treatment initiation rates were calculated per 10,000 person-years (PY) at risk.

RESULTS: Among the 228,251 newly diagnosed RA patients, 6.9% (n=15,884) initiated biologics (n=14,233, 89.6%) or biosimilars (n=1,651, 10.39%). Compared to patients initiating biologics, those initiating biosimilars were older (mean ±SD: 56.74 ± 14.74 vs 52.83 ± 13.97; p<0.001), were more likely to have Medicare Advantage Part D (MAPD) insurance (41.31% vs. 25.70%), and higher Charlson Comorbidity Index scores (0.93 (± 1.36) vs. 0.59 (± 1.12), p<0.001). Non-steroidal anti-inflammatory drugs (61.96% vs 64.80%; p=0.02) or Disease-modifying antirheumatic drugs (68.02% vs 70.52%; p=0.04) were prevalent in both groups. Among patients initiating biosimilars, 793 (48.03%) switched from biologics. Among the new RA patients, the biosimilar initiation increased approximately five-fold, from 13.96/10,000 PY in 2016 to 76.77 in 2021, while the rate of biologics initiation increased by 50%, from 242.27 to 373.27 in the same time period (incidence rate ratio (IRR)=3.57).

CONCLUSIONS: The study findings highlight increased initiation of biosimilars than biologics and also increased adoption of biosimilars among RA patients. The study provides insights into real-world clinical practice of biologics and biosimilars administration and utilization in the United States, and future research is needed to understand overall biosimilar vs biologic uptake and switching patterns.