Inside the isomers: the tale of chiral switches

Abstract

Chiral drugs are made up of molecules with the same chemical structure, but different three-dimensional arrangements. Modern manufacturing has enabled the development of products containing a single molecular arrangement. The development of these single enantiomers from chiral drugs is known as chiral switching. Enantiomers of the same drug can have different pharmacodynamic and pharmacokinetic properties. This may translate into potential health benefits, such as an improved safety margin, if one of the enantiomers has more favourable therapeutic and pharmacokinetic characteristics. However, some chiral switching has resulted in unpredicted toxicity and the withdrawal of the enantiomer from the market or a halt in its development. Drug companies are increasingly using chiral switching as a marketing strategy, but before prescribers switch to single enantiomer drugs they should look for evidence from well-conducted clinical trials that shows the chiral switch is cost-effective and improves the outcomes for patients rather than patents.