In order to keep track with evidence generation in medicine it is necessary not only to have access to results from clinical studies in publications but also to the individual participant data as well as all related study documents (e.g. study protocol , statistical analysis plan, case report form). Data and document sharing is more and more propagated, however, the researcher is faced with a bewildering mosaic of possible source locations and access modalities. There is an urgent need to develop a central resource that can catalogue all the diverse data and documents associated with a clinical study and make that information searchable by a central web portal. In the EU H2020-funded project eXtreme DataCloud (XDC; grant agreement 777367) such a portal has been developed under coordination of ECRIN-ERIC (European Clinical Research Infrastructure).

The metadata repository (MDR) portal is based upon the following components:
•	Importing metadata from existing registries and repositories
•	Mapping of imported metadata to the ECRIN metadata standard
•	Pumping of metadata via restful-API to OneData 
•	Providing functionality for discoverability studies and data objects by 
        INFN (Elastcsearch)
•	Developing portal by OneData
 
In the portal, metadata from 325931 clinical studies and 472938 data objects related to clinical trials have been integrated from 4 different sources (ClinicalTrials.goc, Pubmed, BioLINCC, YODA). It is planned to extend the portal with additional functionalities and to incorporate more data sources (registries, repositories). In addition, the MDR will be introduced as data resource into the European Open Science Cloud (EOSC). The MDR will provide a significant contribution to the findability (F in FAIR) of study documents/data sets and thus will support study planning and secondary analysis of clinical trial data.

Supporting FAIR* data discoverability in clinical research: building an object metadata repository of clinical trial objects