Treatment of active ankylosing spondylitis with abatacept: an open-label, 24-week pilot study

Objective To prospectively explore the short-term efficacy and safety of abatacept in patients with ankylosing spondylitis (AS). Methods In this prospective open-label pilot study, abatacept (10 mg/kg) was administered intravenously on days 1, 15, 29 and every 28 days thereafter up to week 24 in 15 tumour necrosis factor alpha (TNF alpha)-inhibitor naive patients (group 1) and 15 patients with inadequate response to TNF alpha inhibitors (group 2) with active AS. The primary end point was the proportion of patients with 40% improvement according to the Assessment of SpondyloArthritis international Society criteria (ASAS40) in both groups at week 24. Results At week 24, ASAS40 was reached by 13% of group 1 and 0% of group 2; 20% improvement (ASAS20) was reached by 27% and 20%, respectively. There was no significant change of Bath Ankylosing Spondylitis Disease Activity Index score, patient global assessment or C reactive protein. Overall, abatacept was well tolerated. Conclusions In this pilot open-label AS study a major response was not observed.