Efficacy and Safety of Etanercept in Patients With the Enthesitis-Related Arthritis Category of Juvenile Idiopathic Arthritis: Results From a Phase III Randomized, Double-Blind Study

Objective To evaluate the efficacy and safety of etanercept in patients with enthesitis-related arthritis (ERA) in juvenile idiopathic arthritis (JIA). Methods This was a 2-phase study in JIA patients with active, refractory ERA. Phase I was an open-label, uncontrolled 24-week study period in which all patients were administered etanercept. Patients considered to be treatment responders at week 24 according to the American College of Rheumatology (ACR) Pediatric 30 (Pedi 30) criteria for improvement in juvenile arthritis entered the second phase, a 24-week randomized, double-blind, placebo-controlled withdrawal study, for an additional 24 weeks, for evaluation of the primary end point, occurrence of a disease flare from week 24 to week 48, based on the ACR preliminary definition of disease flare in juvenile arthritis. Results Forty-one patients were enrolled. At week 24, treatment with etanercept resulted in response rates of 93%, 93%, 80%, 56%, and 54% based on the ACR Pedi 30, Pedi 50, Pedi 70, Pedi 90, and Pedi 100 criteria, respectively. In addition, a marked decrease in all disease activity measures was observed. The mean number of tender joints, swollen joints, and joints with active arthritis decreased by 91%, 97%, and 94%, respectively. Physician's global assessment of disease activity, parent's assessment of patient's overall well-being, and the Childhood Health Assessment Questionnaire disability index improved by 91%, 80%, and 86%, respectively. The number of tender enthesis sites and total scores for back pain, nocturnal pain, Bath Ankylosing Spondylitis Disease Activity Index, Bath Ankylosing Spondylitis Functional Index, and Juvenile Arthritis Disease Activity Score based on 10-joint counts (JADAS10) decreased by 75%, 72%, 81%, 72%, 85%, and 87%, respectively. In phase II, 38 patients were randomly assigned to receive placebo (n=18) or to continue receiving etanercept (n=20). Up to week 48, 12 disease flares occurred, in 9 patients receiving placebo and 3 patients receiving etanercept (odds ratio 6.0, P=0.02). There were no serious infections, malignancies, or deaths. Conclusion In this study of patients with the ERA category of JIA, etanercept proved effective, as indicated by high ACR Pedi response rates and JADAS10 response rates at week 24. Patients who continued treatment with etanercept had significantly fewer flares than those who received placebo, although 50% of patients in the placebo group did not experience a flare. Treatment suspension may be a consideration for patients with the ERA category of JIA who achieve remission.