The Supply of Investigational Medicinal Product and Management of Study Materials for Decentralized Participants—Insights from the Trials@Home <scp>RADIAL</scp> Proof‐of‐Concept Trial

Decentralized clinical trials (DCTs), which move trial activities to participants' homes or direct surroundings, offer potential advantages over conventional site-based trials through reduced participant burden and improved accessibility. The direct-to-participant (DtP) delivery of investigational medicinal products (IMPs) and other study materials and collection of biological samples requires careful planning and execution to ensure participant safety and data integrity. Here, we report operational experiences from the RADIAL proof-of-concept trial, a three-arm parallel-group study conducted across six European countries comparing conventional, hybrid, and fully decentralized approaches in type 2 diabetes patients. The study implemented two DtP IMP models: clinical trial site-to-participant and central pharmacy-to-participant delivery, with comprehensive logistics tracking and temperature monitoring. In RADIAL, 68 DtP IMP shipments were executed with a 94% successful delivery rate. Four shipments (6%) failed due to participant unavailability, temperature excursions, defective monitoring equipment, or courier loss. The central pharmacy model demonstrated inventory savings compared with conventional site-based distribution. Biological sample collection for HbA1c assessment was done through drop-off, which proved more challenging in the remote arm. Key challenges related to DCT logistics as experienced in RADIAL included unclear importer/exporter responsibilities, regulatory divergence across countries, participant material management, and sample drop-off reliability. DtP IMP delivery and biological sample collection are feasible in European DCTs but require enhanced planning, clear vendor responsibilities, and robust contingency procedures. Success depends on appropriate participant training, reliable courier services, temperature control systems, and accessible biological sample collection methods.