The ClinicalTrialsAPI R package accesses the data in the NIH ClinicalTrials.gov site via the CTRP REST API.
The NCI Genomic Data Commons (GDC) is a reboot of the approach that NCI uses to manage and expose genomic and associated clinical and experimental metadata. I have been working on a Bioconductor package that interfaces with the GDC API to provide search and data retrieval from within R.
In the first of what will likely be a set of use cases for the GenomicDataCommons, I am going to address a question that came up on twitter from @sleight82
The GenomicDataCommons Bioconductor package accesses cancer genomics data from the NCI Genomic Data Commons.
The cRomwell R package runs Workflow Description Language (WDL) workflows on multiple platforms from with R.