The hit validation process involves the confirmation of hit activity using secondary assays and confirmation of on-target activity and selectivity using counter-screens and bioavailability, toxicity and metabolism assays. Lead compounds are selected from a collection of hits by refining the screening criteria to enable the selection of the most promising molecules and potentially lead to the development of a new drug to treat a disease.

Thousands of compounds are tested in the laboratory to find a lead (“leading”) compound that may act on specific genes or proteins involved in a disease.