Background: Behçet's disease is a multi-systemic chronic relapsing inflammatory disease, classified among the vasculitides. The heterogeneity of clinical manifestations challenges the disease management.

Objectives: To assess efficacy and safety of adalimumab in patients with active persistent Behçet's arthritis who did not respond to disease-modifying anti-rheumatic drugs and to assess the impact of treatment on the cytokine milieu.

Methods: Our cohort comprised 10 patients with active arthritis who received adalimumab in a 24-week investigator-initiated prospective open-label study. Patients who relapsed within 12 weeks following adalimumab discontinuation could enter a 3-year extension study. The patients underwent a comprehensive assessment including questionnaires and measurement of inflammatory cytokines, adalimumab serum levels, and anti-drug antibodies.

Results: A significant improvement was observed in arthritis, disease activity visual analogue scales, Behçet's disease current activity form, and interleukin-6 (IL-6) levels, but not in health assessment questionnaire and functional assessment of chronic illness therapy fatigue scale questionnaire. Resolution of oral and urogenital ulcers was achieved in all patients. Significant reduction of pain was reported by 40% of patients. The disease relapsed in 9 of 10 patients, within 2–6 weeks following adalimumab discontinuation. Of the 7 patients who continued the study, arthritis was resolved in 5. Two patients with high neutralizing antidrug antibodies titer relapsed.

Conclusions: Adalimumab treatment achieved a significant improvement in arthritis, mucocutaneous manifestations, and IL-6 levels in all study patients but only 40% reported significant pain reduction. The arthritis relapsed in 90% of patients following adalimumab discontinuation and long-term treatment was required.