Fig. 3.

Target identification of hits. Once a “hit” has been validated, the extent of understanding of the target determines the development of a drug candidate. If a molecule with a known target is identified and the target is verified (branch 1), a new robust HTS assay for the target is developed to yield drug-like compounds that modulate the target of interest. If the target is not confirmed, these compounds are considered as unknown target molecules (dashed arrow). If the target of a hit is unknown (branch 2), the target needs to be identified first by biological and biochemical experimentation, before a drug lead can be developed either directly or through a new assay specific for that newly discovered target