Safety and Efficacy of Readministration of Infliximab After Longterm Continuous Therapy and Withdrawal in Patients with Ankylosing Spondylitis

OBJECTIVE: To analyze the safety and efficacy of the anti-tumor necrosis factor agent infliximab in patients with ankylosing spondylitis (AS) after discontinuation of longterm therapy over 1 year and readministration, using clinical and laboratory assessments including serum levels of antibodies to infliximab (ATI). METHODS: Altogether 42/43 patients with AS in a 3-year multicenter trial discontinued therapy after continuous treatment with infliximab (5 mg/kg/6 wks). Infliximab was only readministered in case of a clinical relapse [judged by Bath AS Disease Activity Index (BASDAI) and physician global assessment > 4]. ATI were measured at different timepoints. The primary outcome was safety, and efficacy outcomes were secondary. RESULTS: One patient dropped out after the eighth infusion after retreatment due to repeated local infections. ATI were detected in this patient only. No other relevant adverse events were observed. One patient remained in clinical remission without therapy for more than 1 year. The other 40 patients (97.6%) were reinfused because of clinical relapse. There was no correlation between ATI and clinical measures. BASDAI 50% responses were seen in 25 (63%) and partial remission in 12 (30%) patients. The mean (± SD) BASDAI score dropped from 6.0 ± 1.4 at the time of relapse to 2.6 ± 2.0, and the median C-reactive protein from 11.2 to 1.8 mg/l after 1 year (all p < 0.05). CONCLUSION: Readministration of infliximab after discontinuation of longterm treatment was generally safe and efficacious. Ongoing remission after discontinuation was rare. There was only one patient with relevant adverse events. ATI were detected only in this patient, but there was no correlation to clinical data. Formation of ATI seems to be rare after longterm infliximab therapy in AS.