From magic bullets to designed multiple ligands.

Increasingly, it is being recognised that a balanced modulation of several targets can provide a superior therapeutic effect and side effect profile compared to the action of a selective ligand. Rational approaches in which structural features from selective ligands are combined have produced designed multiple ligands that span a wide variety of targets and target classes. A key challenge in the design of multiple ligands is attaining a balanced activity at each target of interest while simultaneously achieving a wider selectivity and a suitable pharmacokinetic profile. An analysis of literature examples reveals trends and insights that might help medicinal chemists discover the next generation of these types of compounds.