Maintained Clinical Remission in Ankylosing Spondylitis Patients Switched from Reference Infliximab to Its Biosimilar: An 18-Month Comparative Open-Label Study

Background: Switching from reference infliximab (RI) to biosimilar infliximab (BI) had no detrimental effects on efficacy and safety. However, long-term follow-up data is missing. Objective: To evaluate patients with Ankylosing Spondylitis (AS) in clinical remission who were switching from RI to BI, in terms of the safety and efficacy of this, in a long-term fashion. Methods: One hundred and nine consecutive unselected AS patients were investigated. All were naïve to other biologics and were followed-up at predefined times receiving RI. Patients in clinical remission were asked to switch from RI to BI. Those who switched to BI were compared with a matched control-group receiving continuous RI. During follow-up, several parameters were recorded for at least 18 months. Disease activity was measured using the Bath Ankylosing Spondylitis disease activity index (BASDAI), and the Ankylosing Spondylitis disease activity score (ASDAS), using the C-reactive protein. Remission was defined as BASDAI < 4 and ASDAS < 1.3. Results: Eighty-eight patients were evaluated (21 excluded for different reasons). From those, 45 switched to BI, while 43 continued receiving RI. No differences between groups regarding demographic, clinical and laboratory parameters were observed. All patients were in clinical remission. During follow-up, five patients from the BI-group and three from the maintenance-group discontinued the study (4 patients nocebo effect, 1 loss of efficacy). After 18 months of treatment, all patients in both groups remained in clinical remission. No significant adverse events were noted between groups. Conclusion: BI is equivalent to RI in maintaining AS in clinical remission for at least 18 months.