Dark chemical matter in public screening assays and derivation of target hypotheses

Compounds that are consistently inactive in many screening assays, so-called dark chemical matter (DCM), have recently experienced increasing attention. One of the reasons is that many DCM compounds may not be fully inert biologically, but may provide interesting leads for obtaining compounds that are highly selective or active against unusual targets. In this study, we have systematically identified DCM among extensively assayed screening compounds and searched for analogs of these compounds that have known bioactivities. Analog series containing DCM and known bioactive compounds were generated on a large scale, making it possible to derive target hypotheses for more than 8000 extensively assayed DCM molecules.