Open-Label Phase II Study of Olokizumab in Adolescent Patients with Polyarticular Juvenile Idiopathic Arthritis: Results of the 24-Week Treatment Period

<b>Background/Objectives</b>: This study aimed to evaluate the pharmacokinetics (PK), effectiveness, and safety of the direct interleukin-6 (IL-6) inhibitor olokizumab (OKZ) in adolescent patients with active polyarticular juvenile idiopathic arthritis (pJIA) who had an inadequate response or intolerance to methotrexate (MTX). <b>Methods</b>: We analyzed results from an open-label, single-arm trial of OKZ therapy at a dose of 64 mg every 4 weeks for 24 weeks. We evaluated pharmacokinetic (PK) parameters, clinical effectiveness, serum C-reactive protein (CRP) dynamics, and adverse events (AEs). <b>Results</b>: Sixteen patients were included in the study, of whom 13 (81.2%) received OKZ through Week 24. The PK profile was consistent with observations in adults with rheumatoid arthritis (RA). By Week 16, 12 (80%) patients achieved an ACRpedi30 response, 11 (73.3%) achieved an ACRpedi50 response, and 2 (13.3%) reached inactive disease status. This response was sustained through Week 24, and no disease flares were observed. A trend toward a better response was noted among patients with baseline CRP > 10 mg/L, higher baseline IL-6, and those naïve to biologic DMARDs. Twelve patients (75.0%) experienced twenty-three mild or moderate AEs. Infections were the most frequent AEs (in 6 patients, 37.5%). No serious AEs or deaths occurred. <b>Conclusions</b>: OKZ treatment reduced pJIA disease activity and was well tolerated. The safety profile was consistent with that of other IL-6 inhibitors, and the PK profile matched that seen in adult RA patients.