CHIRAL SWITCH- AN EMERGING STRATEGY IN THERAPEUTICS

Abstract

During the last decade, drug chirality, more specifically the use of single enantiomers versus racemic mixtures has been in the forefront of discussions in scientific forums.This is because the left and right handed twins of a molecule behave quite differently from each other in a biological environment. This can frequently lead to an improvement in pharmacological and therapeutic profile of the molecule/drug. This understanding of the significance of stereo-chemistry coupled with advances in chemical technologies and further nudged by regulatory requirements has helped the increase in the development of individual isomers at the expense of racemic mixtures.Apart from the development of novel stereo-selective compounds, a number of racemates have been re-evaluated as potential single enantiomer agents with  the possibility of an improved pharmacological/therapeutic profile. These have been termed as Chiral Switches and have resulted in the re-birth of a number of agents as single enantiomers and have provided significant improvements over the racemic drug. Economic considerations are also playing a part with pharmaceutical companies increasingly using chiral switching as a marketing strategy to increase the patent longevity and profitability period of a drug. However, not all these switches have resulted in therapeutic superiority and in many instances, unpredicted adverse reactions have resulted. Before a switch to clinical use of single enantiomers is made, physicians should satisfy themselves from evidence based on well-conducted clinical trials that the chiral switch is cost-effective and improves the outcomes for patients.  KEY WORDS: Chirality, Chiral Switch, Enantiomers