To investigate effectiveness of systematic switching treatment from innovator infliximab to biosimilar infliximab, and its associated factors.
In this prospective observational study, all adult patients receiving maintenance therapy with innovator infliximab in Cochin University Hospital were systematically switched to biosimilar infliximab. Effectiveness was assessed by the retention rate of biosimilar infliximab at the time of the third infusion. Sensitivity analyses for effectiveness included changes of disease activity parameters and infliximab trough levels between baseline and the last visit as well as the occurrence of adverse events leading to drug discontinuation. Factors associated with biosimilar infliximab discontinuation at the last visit were explored.
A total of 260 patients fulfilled the inclusion criteria, including 31 rheumatoid arthritis (RA), 131 axial spondyloarthritis (axSpA) and 64 inflammatory bowel diseases. The retention rate was 85% (221/260 patients) at the time of the third biosimilar infusion. Between baseline and the last visit (mean follow-up of 34 weeks), 59 patients (23%) discontinued biosimilar infliximab, mainly due to experienced inefficacy (n = 47, 80%). No clinical or biological factors were associated with biosimilar discontinuation. No serious adverse events occurred. No change in objective disease activity parameters or infliximab trough levels was detected. However, a significant increase of BASDAI (2.94 ± 2.20 vs. 3.18 ± 2.21, P = 0.046, before vs. after switch, respectively) was observed in patients with axSpA. Innovator infliximab was re-established in 47/59 patients (80%).
No changes in drug trough levels or objective parameters were observed after the systematic switch to biosimilar infliximab in a real clinical practice setting. Only changes in patient-reported outcomes were observed, suggesting attribution effects rather than pharmacological differences.