eutomer

In stereochemistry, the eutomer is the enantiomer of a chiral molecule that produces the desired pharmacological effect or therapeutic activity. The opposite enantiomer is called the distomer. Enantiomers are non-superimposable mirror images and can interact differently with biological targets such as receptors, enzymes, or transport proteins, leading to distinct biological outcomes.

The difference in activity between the eutomer and distomer is described by the eudismic ratio, defined as the relative potency or effect of the eutomer compared with the distomer. A ratio greater than one indicates that the eutomer is more active or effective. These differences can be measured in vitro or in vivo and often depend on the specific target and assay used.

In drug development, identifying and isolating the eutomer can improve therapeutic efficacy and safety. This has led to the development of single-enantiomer drugs or chiral switches that replace a racemate with its more active enantiomer. However, the distomer may also contribute to other pharmacological effects, including adverse effects or, in some cases, beneficial activity, so the overall profile of each enantiomer must be carefully evaluated.

Historically, cases like thalidomide demonstrated that enantiomers can have markedly different biological effects, highlighting the importance of stereochemistry in medicinal chemistry and pharmacology. The concept of eutomer remains central to understanding enantioselectivity and guiding the design and use of chiral medicines.