Development of Stereoisomers (Chiral) Drugs: A Brief Review Of Scientific and Regulatory Considerations

Stereoisomers are molecules that are identical to one another in terms of atomic constitution and sequence ofcovalent bonds, but which differ in the three dimensional arrangement of atoms. There is a growing belief that enantioselectivity in the pharmacodynamic and pharmacokinetic properties of a drug is not a rare phenomenon, but occurs rather frequently. Because of differences in pharmacological activity between enantiomers, racemic mixtures can, in theory, be seen as combination products. Recognition of potential differences of pharmaceutical enantiomers has led to increasing attention by regulatory agencies to developments with such compounds. This paper will briefly review the scientific and regulatory guidance provided for the development and approval ofchiral drugs in Canada, and relate this to the requirements currently in place in the United States and Europe.