Comparable long-term outcomes with biosimilar and originator adalimumab in juvenile idiopathic arthritis: a multicenter cohort study.

BACKGROUND: Real-world evidence on biosimilar adalimumab in juvenile idiopathic arthritis (JIA) remains limited. We compared the effectiveness, treatment persistence, and safety of biosimilar and originator adalimumab. METHODS: This multicenter retrospective cohort study included children with JIA treated with biosimilar or originator adalimumab for ≥24 weeks. Disease activity was assessed using the Juvenile Arthritis Disease Activity Score-27 (JADAS-27) and, in enthesitis-related arthritis (ERA), the Juvenile Spondyloarthritis Disease Activity Index (JSpADA). Treatment persistence and adverse events were compared. RESULTS: 129 patients were analyzed (originator product [OP], n = 86; biosimilar product [BP], n = 43; ABP 501, n = 39; GP2017, n = 4). Prior biologic exposure was higher in OP (p = 0.007), and time to adalimumab initiation was longer in OP (p = 0.015). JADAS-27 scores were higher in BP at treatment initiation (T0) and month 3 (T3) (p = 0.029 and p = 0.027) but not thereafter. JSpADA scores were similar overall. Treatment persistence was similar between groups (p = 0.080). Remission ≥ 6 months was more frequent in OP (p = 0.039), whereas drug-free remission and adverse event rates were similar. CONCLUSIONS: Biosimilar adalimumab demonstrated comparable long-term outcomes to the originator, although baseline differences between groups should be considered.