Safety and effectiveness of rituximab biosimilar (Rituximab-GP2013) versus originator in rheumatoid arthritis:...

To compare the effectiveness, safety, and retention of rituximab biosimilar (RTX-GP2013) and RTX-originator in RTX-naive Rheumatoid Arthritis (RA) patients in a real-world setting.

This single-center, longitudinal, observational study included 107 RA patients who initiated RTX therapy between January/2010 and September/2023 (40 RTX-GP2013 and 67 RTX-originator). A convenience sample of consecutive eligible RTX-naïve patients was analyzed. Disease activity, treatment retention, and infusion-related reactions were assessed over six months (6M). Multivariate logistic regression identified predictors of low disease activity (CDAI ≤ 10) at 6M.

RTX-GP2013 patients were older (58.3 [53.1-66.4] vs. 54.9 [45.6-60.8], p = 0.029), had longer disease duration (18.4 ± 9.5 vs. 14.7 ± 8.9, p = 0.045), and a greater number of prior biologic therapies (3 [1-5] vs. 1 [0-2], p < 0.001). At 6M, frequency of low disease activity (30.0% vs. 47.8%, p = 0.103), retention rates for a second RTX cycle (77.5% vs. 85.1%, p = 0.433) and mild/moderate infusion-related reactions (17.5% vs. 9.0%, p = 0.231), were comparable between RTX-GP2013 and RTX-originator groups, respectively. Multivariate analysis identified lower baseline disease activity (per 1-point increase in CDAI: OR = 0.93, 95% CI 0.88-0.97, p = 0.003) and fewer prior advanced therapies (OR = 0.56, 95% CI 0.38-0.82, p = 0.003) as predictors of low disease activity at 6M, whereas RTX-GP2013 was not associated with poorer clinical response (OR = 1.85, 95% CI 0.63-5.45, p = 0.265).

In this real-world study, RTX-GP2013 and RTX-originator demonstrated comparable effectiveness, safety, and treatment retention in RTX-naive RA patients. Baseline disease activity and fewer prior therapies were predictors of clinical response. These findings reinforce the role of biosimilars in expanding access to effective therapies while maintaining clinical outcomes.