Screening and Designing

SCREENING AND DESIGNING

The process of finding a new drug against a desired target for a particular disease usually involves highthroughput screening (HTS), wherein large libraries of compounds are tested for their ability to modify the target. For example, if the target is a novel GPCR, compounds will be screened for their ability to inhibit or stimulate that receptor. If the target is a protein kinase, the chemicals will be tested for their ability to inhibit that kinase.

Another important function of HTS is to show the selectivity of compounds for the desired target. The idea is to find a molecule that will interfere with only the chosen target, but not the other related targets. For this, other screening runs will be performed to see whether the ‘hits’ against the chosen target will interfere with other related targets. This process is called cross-screening. More unrelated targets a compound hits, the more likely it is that off-target toxicity will occur with that compound, hence crossscreening is important.

Although HTS is a commonly used method for novel drug discovery. It is often possible to start from a molecule, which already has some of the desired properties. Such a molecule might be extracted from a natural product or even be a drug on the market, which could be improved upon (called ‘me too’ drugs). Other methods, such as virtual HTS, where screening is done using the computer-generated models and attempting to ‘dock’ virtual libraries to a target, are also often used.

Another important method for drug discovery is drug designing, whereby the biological and physical properties of the target are studied, and a prediction is made about the sort of chemicals that might fit into an active site. From these exercises, novel pharmacophores can emerge very rapidly.

Once a lead-compound series has been established with sufficient target potency, selectivity, and favourable drug-like properties one or two compounds will then be proposed for drug development. The best of these is generally called the lead compound, while the other will be designated as the ‘backup’.