Effectiveness of First-Line Treatment With Recombinant Interleukin-1 Receptor Antagonist in Steroid-Naive Patients With New-Onset Systemic Juvenile Idiopathic Arthritis Results of a Prospective Cohort Study

Objective. To conduct a prospective cohort study using anakinra, a recombinant IL-1 receptor antagonist (IL-1Ra), as first-line therapy in patients with new-onset systemic juvenile idiopathic arthritis (JIA). Methods. Therapy with recombinant IL-1Ra (2 mg/kg) was initiated in 20 patients who fulfilled the International League of Associations for Rheumatology criteria for systemic JIA, before systemic steroid treatment was administered. Patients were monitored clinically and immunologically. The protocol contained a stop strategy for patients who met at least the adapted American College of Rheumatology 90% criteria for improvement in JIA (ACR Pediatric 90 [ACR Pedi 90]) after 3 months. Results. We included consecutive patients with new-onset systemic JIA. The mean followup period was 32 months (range 12-54 months). At the 3-month time point, 85% of the patients showed an adapted ACR Pedi 90 response or had inactive disease; 75% of the patients achieved this response while receiving recombinant IL-1Ra alone. After 1 year, 17 of the 20 patients met the criteria for clinically inactive disease, and 13 of these patients met these criteria while receiving monotherapy with recombinant IL-1Ra. However, because of persistent disease activity, 7 of the 20 patients required additional therapy besides recombinant IL-1Ra. According to our stop strategy, 73% of patients with at least an adapted ACR Pedi 90 response at 3 months could stop recombinant IL-1Ra treatment within 1 year. After 2 years, 12 (86%) of 14 patients met the criteria for disease remission, either while receiving (n = 4) or not receiving (n = 8) medication. After 3 years, 10 (91%) of 11 patients met the criteria for disease remission, either while receiving (n = 2) or not receiving (n = 8) medication. Conclusion. This is the first prospective study in which recombinant IL-1Ra was used as first-line therapy in patients with systemic JIA. We observed excellent responses in nearly all patients within 3 months. In the majority of responding patients, treatment with recombinant IL-1Ra could be stopped within 1 year, with remission being preserved during followup. In approximately one-third of patients, concomitant therapy was required for maintenance of clinical response.