How can innovative trials in juvenile idiopathic arthritis serve the unmet needs of patients?

Abstract Juvenile idiopathic arthritis (JIA) comprises a heterogeneous group of childhood-onset inflammatory arthritides that remain challenging to treat. An expanding range of biologic and targeted synthetic disease-modifying antirheumatic drugs has improved outcomes, yet major unmet needs persist including predicting treatment response and identifying optimal drug sequences. Traditional frequentist randomised controlled trials (RCTs) are often infeasible in JIA because of small sample sizes and ethical concerns about placebo use in children. Modified RCTs - including randomised withdrawal, placebo-phase, and escape designs - have reduced placebo exposure but have inherent limitations. Here we discuss how innovative trial methodologies may enhance our capacity to generate evidence that can improve outcomes for children and young people with JIA. Adaptive designs, Bayesian methods, sequential multiple assignment randomized trials, and two-stage stop–go designs offer greater flexibility within trials, allowing for study protocols to be adapted based on preliminary data. Insights from multiomic analysis of JIA synovial tissue mean that biologically defined endotypes may fundamentally reshape trial stratification and support biomarker-led precision medicine. Master protocols (basket, umbrella and platform trials) provide opportunities to streamline research by combining data into a single trial. The incorporation of external data can increase statistical power and circumvent challenges in recruiting paediatric controls. Integrating these methodological and biological innovations will be critical for delivering targeted, effective, and age-inclusive therapeutic strategies, ultimately improving outcomes for children and young people living with JIA.