A snapshot of subcutaneous infliximab uses in inflammatory rheumatic diseases: a multicentric Italian study

Background: The recent availability of infliximab subcutaneous biosimilar in Europe represents a significant advancement in therapeutic delivery. Real-world data regarding the new formulation are still limited. Objectives: To describe subcutaneous infliximab (scIFX) use in immune-mediated inflammatory diseases (IMIDs), evaluating clinical effectiveness, treatment persistence, and factors influencing drug retention rates (DRRs). Methods: Adult patients with IMIDs treated with scIFX either de novo or after switching from intravenous infliximab (ivIFX) were included. Disease activity was assessed using standard indices, and persistence was evaluated through 18-month DRRs. Results: In total, 201 patients were included (66.7% women): 68 with psoriatic arthritis (33.8%), 66 axial spondyloarthritis (32.8%), 18 rheumatoid arthritis (9.0%), 18 Behçet’s disease (9.0%), 16 juvenile idiopathic arthritis (8.0%), 10 Takayasu arteritis (5.0%), and 5 other IMIDs (2.5%). Median treatment duration was 14 months (interquartile range 13.0). Ninety-five patients (47.3%) switched from ivIFX, while 106 initiated scIFX de novo, of whom 74 (78.3%) received induction. Median disease activity grades improved from baseline through 24 months (p < 0.001). Fifty-five subjects (27.4%) discontinued scIFX. DRRs were 88.5%, 76.9%, and 68.3% at 6, 12, and 18 months, respectively. DRRs were higher in switchers versus de novo initiators (p = 0.038), also controlling for baseline activity and loading protocol (hazard ratio = 0.25 [95% confidence interval: 0.075–0.848], p = 0.026). De novo patients without induction had lower DRRs (p = 0.033) than those receiving induction, whereas line of biologic therapy (p = 0.066) and body mass index (BMI; p = 0.445) had no effect on scIFX DRRs. Adverse events occurred in 21 patients (10.4%). Conclusion: ScIFX appears effective across IMIDs, with sustained retention over time. Prior ivIFX exposure and use of induction protocols are associated with improved persistence, while treatment line and BMI appear not to influence outcomes.