Polyarticular-course juvenile idiopathic arthritis (pcJIA) is a chronic condition that manifests before the age of 16 years, with pathology similar to that of adult rheumatoid arthritis (RA). Sarilumab is an interleukin-6 receptor inhibitor approved for RA and pcJIA. To obtain the approval for pcJIA, a single-arm, multiple-dose phase 2 study was conducted to determine the sarilumab dose for pcJIA. The population pharmacokinetics analysis of the phase 2 dose-finding portion data showed comparable pharmacokinetics; exposure–response analyses demonstrated similar or greater efficacy (JIA-ACR30/50/70), and consistent safety (reduction in absolute neutrophil count) in patients with pcJIA compared with adult patients with RA at similar sarilumab exposure. Based on the adult-to-pediatric extrapolation concept and justifications using modeling and simulation, the phase 2 sample size was increased to generate sufficient efficacy and safety data and evidence at selected doses and the requirement for a randomized controlled study in patients with pcJIA was waived. This novel approach enabled the pcJIA dose proposal by aligning with adult RA exposures, streamlined clinical development by removing the control arm requirement and minimized children participation while ensuring robustness of sarilumab efficacy and safety evidence for approval.
Xu et al. (Tue,) studied this question.