Moving from GtoPdb to ChEMBL provides a step-change up to 1.9 million compounds and 12K targets extracted from 72K papers (see 'ChEMBL: towards direct deposition of bioassay data', 2019, PMID 30398643 and Fig. ). However, this is accompanied by a concomitant increase in navigational complexity (as can be perceived from this useful schema diagram). A key difference between GtoPdb and ChEMBL is that the former typically extracts just the lead compound from selected papers whereas the latter extracts an average of ~15 via contract curation with broad journal coverage. It should be noted that ChEMBL also imports about 0.5 million compounds from confirmatory PubChem BioAssays. While this extends the bioactivity coverage it also adds confounding circularity (see 'Redundancy in two major compound databases . Users should also note that the long release cycles result in ~2 year lag in literature extraction. Notwithstanding these minor disadvantages, ChEMBL offers a comprehensive and navigable resource for drug discovery and chemical biology. It is particularly good for discerning target "popularity". For example BACE1, as an Alzheimer's target, has no less than 8,741compounds in CHEMBL4822 with assay results against this enzyme. In contrast, GtoPdb target ID 2330 provides a selected core SAR set of 24 leads and (failed) drugs from which users can move out to the much larger SAR envelope in ChEMBL. Searching the latter thus has a high probability that ADEV compounds and targets will have at least similarity relationship matches.