What is drug discovery?

Target identification and validation

Discovery usually starts with a biological target — often a protein such as a receptor or enzyme — believed to play a causal role in a disease. Researchers use insights from genetics, cell biology and disease mechanisms to choose a target, then validate it by gathering evidence that altering its activity could produce a beneficial effect. Target validation is critical because the entire downstream programme rests on the assumption that engaging this target matters; a poorly validated target is a common reason candidates later fail in development.

Screening and hit identification

With a target in hand, researchers search for molecules that interact with it. High-throughput screening tests large compound libraries for activity, while structure-based and computational approaches design or prioritise molecules using knowledge of the target’s shape. Molecules that show the desired activity are called hits. Because raw activity is only a starting point, hits are then assessed for selectivity, drug-like properties and feasibility, narrowing many candidates down to a smaller set worth pursuing further.

Lead optimisation

The most promising hits become leads, which are then iteratively improved in a stage called lead optimisation. Medicinal chemists modify a lead’s structure to improve potency, selectivity, pharmacokinetic behaviour and safety, balancing many properties at once. Early ADME and toxicity testing guides these changes.

The output of drug discovery is a development candidate: a well-characterised compound considered good enough to enter the formal, regulated drug-development process, beginning with preclinical safety studies. Discovery is therefore the creative, exploratory front end of the pipeline.