Continuous treatment with the anti-tumor necrosis factor alpha monoclonal antibody infliximab is efficacious in ankylosing spondylitis (AS), whereas treatment discontinuation results in disease relapse, with variable delay. Objective of this study was to compare efficacy between a continuous treatment with infliximab, and a treatment adapted to symptoms recurrence. Addition of methotrexate (MTX)to infliximab was also tested.

Patients with active AS were randomly assigned to receive infliximab every 6 weeks (Q6), or only upon symptoms recurrence (on-demand), following a loading regimen of infusions at weeks 0, 2, and 6. Patients in the latter group were randomly assigned to receive MTX or not, starting 4 weeks prior to infliximab. Monitoring was performed over one year. The primary end point was the proportion of patients with a 20% improvement response according to the ASsessment in Ankylosing Spondylitis (ASAS) criteria, at week 54.

Inclusion Criteria:

• Adult patients (> 18 years old)
• With a diagnosis of AS
• With at least one of the following evidences for active inflammation, present within 3 months before inclusion: a serum C-reactive protein (CRP) level above twice the upper limit value of the normal range, a positive magnetic resonance imaging of the spine or sacro-iliac joints, a vascularized enthesitis by power-Doppler ultrasound technic.
• Presence of clinically active axial disease, as defined by 1) a Bath AS Disease Activity Index (BASDAI) (18) of ≥ 3/10, and 2) a score of ≥ 3/10 for axial pain (second item of BASDAI).
• Disease-modifying antirheumatic drugs (DMARDs), such as sulphasalazine, methotrexate, hydroxychloroquine, intra-muscular gold, thiol compound, cyclosporin, intravenous biphosphonate had to be discontinued for at least 4 weeks before inclusion.
• Dosages of NSAIDs and corticosteroid were required to remain stable for at least 4 weeks before inclusion.
• A negative pregnancy test result was required for non menopausal female patients, and contraception during the study period and for six months after the last infusion of infliximab was recommended to all patients of childbearing potential.

Exclusion Criteria:

• Pregnancy.
• Breastfeeding.
• Vaccination with a live organism during the last month.
• Present infection or any episode of serious infection within the last three months.
• Active malignancy within the previous five years.
• Alcohol or drug addiction.
• Severe chronic concomitant disease.
• Administration of an investigational drug within the last three months, or of any known TNF inhibitor therapy in the past (such as thalidomide, infliximab or etanercept).