Background/Purpose:   To evaluate the pharmacokinetics (PK) of body surface area (BSA)-adjusted dosing of SC golimumab 30 mg/m² every 4 weeks (q4w) + methotrexate (MTX) in pediatric patients with juvenile idiopathic arthritis (JIA) and to determine the similarity in golimumab exposure between these patients and adult rheumatoid arthritis (RA) patients following SC administration of 30 mg/m² or 50 mg fixed dose q4w, respectively.  

Methods: A dosing regimen of SC golimumab 30 mg/m² (maximum 50 mg) q4w + MTX in pediatric patients with JIA was predicted to be equivalent to SC golimumab 50 mg q4w + MTX in adult RA patients .  GO-KIDS is a randomized-withdrawal, double-blind, placebo-controlled, parallel-group, multicenter Phase 3 trial of SC golimumab 30 mg/m² (maximum 50 mg) q4w + MTX in pediatric patients aged 2 to < 18 years old with active JIA despite current MTX therapy. PK, safety, and efficacy evaluations were performed every 4 weeks.  Serum golimumab trough concentrations for 119 patients were determined via a validated, specific and sensitive immunoassay at weeks 0, 4, 8, 12 and 16 and were summarized by age.

Results: Treatment with SC golimumab 30 mg/m² q4w resulted in median trough serum golimumab concentrations of 1.05 to 1.28 µg/mL at steady state in three different age groups of JIA patients (Table). The steady-state trough concentrations in patients with JIA  were similar to that seen in adult RA patients (median: 0.93 µg/mL; mean [SD]: 1.17 [0.99] µg/mL) who received golimumab 50 mg + MTX.

Conclusion:   The study results confirmed that serum golimumab exposure in pediatric patients with JIA following administration of 30 mg/m² q4w was similar to that observed with 50 mg q4w in the adult RA population and was consistent across the various age groups studied.