The MDR harvests metadata on data objects from a variety of sources within clinical research (e.g. trial registries, data repositories) and brings that together in a single searchable portal. The metadata is concerned with discoverability, access and provenance of the data objects (which because the data may be sensitive will often be available under a controlled access regime). At the moment (01/2021) the MDR obtains study data from: Clinical Trials.gov (CTG), The European Clinical Trials Registry (EUCTR), ISRCTN, The WHO ICTRP