Structure-based druggability assessment — identifying suitable targets for small molecule therapeutics

A target is druggable if it can be modulated in vivo by a drug-like molecule. The general properties of oral drugs are summarized by the ‘rule of 5’ which specifies parameters related to size and lipophilicity. Structure-based target druggability assessment consists of predicting ligand-binding sites on the protein that are complementary to these drug-like properties. Automated identification of ligand-binding sites can use geometrical considerations alone or include specific physicochemical properties of the protein surface. Features of a pocket's size and shape, together with measures of its hydrophobicity, are most informative in identifying suitable drug-binding pockets. The recent availability of several validation sets of druggable versus undruggable targets has helped fuel the development of more elaborate methods.

► Most proteins are not suitable targets for orally bioavailable drugs.
► Known drugs generally exploit binding pockets for endogenous ligands.
► Many druggability methods rely on the shape and hydrophobicity of the binding pocket.
► Other methods perform docking of representative small molecules to assess druggability.
► Publicly available training sets have led to the creation of new methods.