Canakinumab dosing intervals in pediatric colchicine-resistant FMF: outcomes and predictors of successful extension in a real-world cohort.

OBJECTIVES

Canakinumab is widely used in colchicine-resistant familial Mediterranean fever (FMF), yet data on interval adjustment strategies and predictors of successful extension remain limited. This study evaluated clinical and inflammatory outcomes across dosing interval groups and identified factors associated with successful interval extension.

METHODS

This retrospective single-centre study included 60 pediatric patients with colchicine-resistant FMF treated with canakinumab. Patients were stratified into stable interval (group 1, n = 14), successful interval extension (group 2, n = 24) and unsuccessful interval extension (group 3, n = 22). Longitudinal C-reactive protein (CRP) trajectories were analysed using linear mixed-effects models. Clinical outcomes were compared across groups, and predictors of successful interval extension were assessed using multivariable logistic regression with Firth's penalized method as a sensitivity analysis.

RESULTS

Following canakinumab initiation, CRP levels declined rapidly and stabilized after month 3, while the median annual attack rate decreased from 7 (4-12) to 1.1 (0.5-2.1) attacks per patient-year. Inflammatory trajectories did not differ across groups. Despite similar CRP dynamics, complete remission rates differed significantly (57.1%, 45.8% and 27.3% in Groups 1-3, respectively; P = 0.005), and all patients in group 3 experienced attacks. Arthritis at disease onset was independently associated with successful interval extension (OR = 7.14, 95% CI 1.26-40.41, P = 0.026), with consistent direction in Firth analysis (OR = 5.51, 95% CI 1.08-28.23, P = 0.081).

CONCLUSION

Although canakinumab achieves sustained inflammatory suppression, biochemical improvement does not ensure comparable clinical control. Clinical phenotype, particularly arthritis at onset, may guide individualized interval adjustment.