The main focus surrounding the Drug Design stage (see diagram in Part 1) is to optimize the hit compound(s) and produce analogues that will increase the activity at the target site. Lead optimization is accomplished through minor modifications of the hit compound.
In Drug Design, medicinal chemists aim to build a diverse library of compounds using the hit compound(s) as a blue print for synthesis. On the flip side, an increase in the compound’s toxicity can have it rejected from the library. For this purpose, many pharmaceutical companies apply at this stage an early ADME/Tox (Absorption, Distribution, Metabolism, Elimination/Excretion and Toxicity) screening.