FAIRification on Trial? A Provenance and Reproducible Metadata Build Pipeline for Clinical Research.

Clinical trial registries often focus on the human user and do not focus on machine-actionable structures and means to detect and manage provenance, thus hindering large scale reliable reuse and verification. This study presents a FAIRification pipeline for EU Clinical Trials Registry metadata, which preserves provenance and enables the reproduction of results. When the pipeline is run on the trials uploaded between 2022 and 2025, it was able to convert 94.84% of trial metadata into NFDI4Health metadata model. The process demonstrates almost complete population of the target model's mandatory properties. The process ensures that each transformation has W3C PROV-O lineage. As RO-Crates, outputs allow federated inclusion in catalogs and verifiably repeatable reuse. We demonstrate that trial metadata should be made available as reproducible digital objects rather than textual or permanent narratives. Same inputs should result in identical outputs, and transformations should be completely auditable.