Target-based drug discovery begins with identifying the function of a possible therapeutic target- normally a gene and its respective gene product- and its role in disease. Currently, all existing therapies together hit only about 400 different drug targets (Drews 2000), but according to latest calculations there are at least 10 times as many potential drug targets that could be exploited for future drug therapy.
Targets for therapeutic intervention can be broadly classified into four groups:
Proteins and enzymes
RNA and ribosomal targets
The “drugability” of a given target is defined either by how well a therapeutic, such as small molecule drugs or antibodies, can access the target, or by the efficacy a therapeutic can actually achieve.
Several parameters influences drugability of a given target, including cellular location, development of resistance, transport mechanisms such as export pumps, side effects, toxicity, and others.
Drews, J. Drug discovery: a historical perspective. Science 287, 1960-1964 (2000).