Hit to Lead also Known as Closed Loop

Potency against primary project biology target 

Toxicity screen (e.g., HERG or equivalent especially for CNS approaches) 

Some type of input on systemic drug levels 

Some types of screens used in hit to lead are controversial and are used in some organizations but not in others. Examples of these are  

The challenge for the drug discovery organization is how to handle the resource issues for multiple screening data feedback. Often a combination of experimental screens and computational prediction approaches will be used. Rapid data feedback to the medicinal chemist is essential, whether the data is experimental or computational. Data delayed is data with greatly reduced value. 

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