Regulatory and Patenting Aspects of Chiral Drugs

Any chiral drug, when prepared using a chemical synthesis method, is usually obtained as a 50:50 racemic mixture of R and S enantiomers. Irrespective of whether the R or S enantiomer is the active pharmaceutical ingredient (API), a drug is more often marketed in its racemic form. Drug developers state a number of reasons for the racemate to be approved by regulatory agencies such as Investigational New Drug Application (INDA). The US Food and Drug Administration (FDA, which is the most prominent regulatory agency in the world) does not insist on a new drug being marketed as a racemic mixture or as a single enantiomer as long as its safety, efficacy and risk–benefit analyses have been thoroughly carried out by the manufacturer. In view of the huge costs involved in drug development, manufacturers use patent protection as a tool to recover the costs. In most cases, patent extension is also resorted to, but it is a serious issue involving techno-legal issues and competition from generic companies.