Enanta Pharmaceuticals, Inc. V. Pfizer Inc. (D. Mass. 22-cv-10967; Fed. Cir. 25-1427).

Enanta appealed Judge Casper’s grant of summary judgment of invalidity of Enanta’s U.S. Patent No. 11,358,953 covering compounds that inhibit enzymes used by the COVID-19 virus to reproduce. Judge Casper found that the ‘953 Patent was not entitled to the provisional priority date because the ‘953 Patent impermissibly broadened the definition of the claimed “substituted” alkyls from “C₂-C₁₂ alkyls” to “C₁-C₁₂ alkyls”, and that the accused product contained a C₁ alkyl. Because Pfizer publicly disclosed the claimed compound in the time after the filing of the provisional but before the filing of the utility application that became the ‘953 Patent, Judge Casper found the patent to be invalid as anticipated. Enanta subsequently appealed.

The Federal Circuit affirmed Judge Casper’s decision. First the Court determined that this case hinged on a specific written description question – whether recitation of “C₂-C₁₂ alkyls” provided sufficient description support for the subsequent claim that covered C₁ alkyls – rather than a genus-species determination. Enanta argued that whether the reference to “C₂ alkyls” would have been recognized by one of skill in the art to have been a typographical error was a material issue of fact that precluded summary judgment. The Court found, however, that the range claimed in the provisional excluded the C₁ alkyl of the accused product. Further, while the provisional initially provided a definition of “alkyl” as “saturated straight- or branched-chain hydrocarbon radicals” having from one to four, one to six, one to eight, or one to twelve carbon atoms, this language was found only in the general definition of alkyl and not in the specific disclosure of NHC(O)-C₂ – C₁₂-alkyl” referred to in the provisional’s definition of “substituted.” Accordingly, one of skill in the art would not understand the “substituted” definition to provide written support for a C₁ alkyl.