Patenting Enantiomers - Court Decides There Is Nothing Sinister

Today, the majority of the world's top selling pharmaceutical products have a chiral molecule as their active pharmaceutical ingredient. Increasingly, this chiral molecule is a single enantiomeric form of that molecule. As the importance of enantiomeric compounds to the pharmaceutical industry has increased, so has the number of patents that relate to such compounds. This, in turn, has led to an increasing amount of litigation with respect to such patents as the patent holders assert those patents to protect their valuable intellectual property and the revenue stream that it generates and generic manufacturers challenge those patents in order to gain access to a piece of that revenue stream.

This article will discuss the first Australian court decision concerning the infringement and validity of an enantiomer patent, Ranbaxy Australia Pty Ltd v Warner-Lambert Company LLC (No 2) [2006] FCA 1787.

Chiral molecules and enantiomers

Chiral molecules are molecules that exist in distinct mirror image forms that cannot be superimposed on each other. These mirror image forms are called enantiomers.1Purified enantiomers exhibit identical physical and chemical properties to their mirror image, however, they often exhibit very different biological activity. For instance, one enantiomer can have most, if not all, the biological activity. Further, toxicity may be associated with only one enantiomer. This was most unfortunately...