In addition to the new data from the aforementioned sources, TCRD has been continuously updated when newer versions of source databases (e.g. ChEMBL (21), DrugCentral (22), JensenLab PubMed scores (23) are released. As the amount of data available for each target changed with each release of TCRD, the target development levels (TDLs) for respective targets were recalculated when the target criteria changed. This was done using automated scripts. Very briefly, the TDL is one of four potential values: Tclin, Tchem, Tbio or Tdark. Tclin are protein drug targets via which approved drugs act (24–26), which currently includes 659 human proteins; Tchem are proteins that are not Tclin, but are known to bind small molecules with high potency (currently N = 1607); Tbio includes proteins that have Gene Ontology (27) ‘leaf’ (lowest level) term annotations based on experimental evidence; or meet two of the following three conditions: A fractional publication count (28) above 5, three or more Gene RIF, ‘Reference Into Function’ annotations (https://www.ncbi.nlm.nih.gov/gene/about-generif), or 50 or more commercial antibodies, as counted in the Antibodypedia portal (29). The fourth category, Tdark,
