The US Court of Appeals for the Federal Circuit affirmed a district court’s claim construction, finding that plain claim language will not be narrowed unless the patentee clearly and explicitly disclaims broader claim scope. Sumitomo Dainippon Pharma Co. v. Emcure Pharm. Ltd., Case Nos. 17-1798; -1799; -1800 (Fed. Cir., Apr. 16, 2018) (Stoll, J).

Sumitomo owns a patent directed to “novel imide compounds and their acid addition salts” that are useful as antipsychotic agents. The patent discloses and claims more than one billion compounds, some of which have stereo and optical isomers. Stereoisomers are molecules with the same chemical formula and structure but different three-dimensional configurations. After several generic drug manufacturers filed abbreviated new drug applications with the US Food and Drug Administration seeking approval to market generic versions of Sumitomo’s drug LATUDA®, Sumitomo filed a lawsuit.

The claim construction issue in the district court focused on what combination of enantiomers the asserted claim encompassed. The generic drug manufacturers sought to limit the asserted claim to “a racemic mixture of two enantiomers of which the structural formula is representative.” The district court rejected the generic drug manufacturers’ narrow construction because it excluded the specific enantiomer depicted in the asserted claim. Instead, the court adopted Sumitomo’s proposal, which construed the asserted claim to cover “lurasidone, lurasidone’s enantiomer, as well as mixtures of these enantiomers.” Following the district court’s claim construction, the generic drug manufacturers stipulated to infringement and appealed.

The Federal Circuit found that the plain language of the claim covered the depicted enantiomer. The Court also noted that the specification described the enantiomer depicted in the claim as a preferred embodiment and provided physical data on the enantiomer, and found that the specification did not disclaim the specific enantiomer. Finally, the Court found that the generic drug manufacturers’ reference to extrinsic evidence was unavailing because the intrinsic evidence demonstrates that the claim covers the depicted enantiomer. The Court thus affirmed the district court’s claim construction.