Azurity Pharmaceuticals, Inc. v. Alkem Laboratories Ltd., No. 2023-1977 (Fed. Cir. (D. Del.) Apr. 8, 2025). Opinion by Murphy (sitting by designation), joined by Moore and Chen.
Azurity owns a patent directed to non-sterile drinkable liquid formulations and methods for using those formulations to treat a particular infection. After Alkem submitted an Abbreviated New Drug Application (ANDA) seeking approval of a generic formulation, Azurity filed an infringement lawsuit.
Following a bench trial, the district court ruled that Alkem’s ANDA did not infringe because the ANDA product contains propylene glycol, an ingredient Azurity had “clearly and unmistakably” disclaimed during prosecution of the patent’s parent application. Azurity appealed.
The Federal Circuit affirmed. The court ruled that during prosecution of the parent application, Azurity “at every opportunity … clearly and unmistakably distinguished its invention” from the prior art by asserting that the claimed formulations did not contain propylene glycol. As part of the prosecution, Azurity had adopted a “consisting of” transition in the claims, and the Federal Circuit ruled that “the prosecution history leaves no room to doubt” that Azurity did so to narrow the claims and overcome the cited prior art and its disclosure of propylene glycol. Thus, based on “the totality of the relevant prosecution history,” the court concluded that Azurity’s disclaimer of propylene glycol “was clear, unambiguous, and complete.”
Azurity next argued that the parties had entered into a pretrial stipulation that precluded application of the disclaimer. The stipulation indicated that “suitable flavoring agents for use in the Asserted Claims include flavoring agents with or without propylene glycol.” Azurity argued that the stipulation should be interpreted as an agreement that infringing flavoring agents in Alkem’s ANDA product could contain propylene glycol. The Federal Circuit disagreed for several reasons, ultimately concluding that “the district court correctly determined that ‘the stipulation says nothing about whether Alkem’s ANDA contains a flavoring agent with propylene glycol,’ a necessary link in its mix-and-match theory of infringement.”
Finally, the Federal Circuit affirmed the district court’s decision that the presence of propylene glycol in Alkem’s ANDA product established noninfringement. There was no dispute that Alkem’s proposed generic formulation contains propylene glycol.