Federal Circuit Provides Guidance For Stereochemistry Claim Construction

On April 16, 2018 in a precedential opinion, the United States Court of Appeals for the Federal Circuit, Sumitomo Dainippon Pharma v. Emcure Pharms., Nos. 2017-1798, -1799, -1800, affirmed the United States District Court for the District of New Jersey by construing the claimed chemical structure diagram to encompass at least the specific enantiomer depicted, refusing to limit the claim to only cover a racemic mixture of the (+) and (–) enantiomers, absent clear indication that the depicted enantiomer should be excluded from the claim.

As a background on stereochemistry, enantiomers are different molecules with the same chemical formula and sequence of atoms but different three-dimensional configurations. Though they often have identical physical properties, enantiomers frequently have different pharmacological properties. Enantiomers may be characterized as (+) and (–) versions based on their ability to rotate polarized light in different directions. Racemates, or