The US Court of Appeals for the Federal Circuit affirmed a district court’s noninfringement determination, finding that the presence of a disclaimed compound in the accused product precluded infringement. Azurity Pharm., Inc. v. Alkem Lab’ys Ltd., Case No. 23-1977 (Fed. Cir. Apr. 8, 2025) (Moore, Chen, Murphy, JJ.)
Azurity owns a patent directed to a nonsterile, stable liquid formulation of vancomycin hydrochloride, specifically designed for oral administration to treat Clostridium difficile infections. Following Alkem’s submission of an Abbreviated New Drug Application (ANDA), Azurity brought a Hatch-Waxman Act claim against Alkem for infringement of certain claims of the patent. The district court found that Azurity had disclaimed the presence of propylene glycol in the claimed formulation during the prosecution. Since Alkem’s ANDA product contained propylene glycol, the district court held that it did not infringe. Azurity appealed.
The Federal Circuit affirmed, focusing on the patent’s prosecution history and noting that Azurity used the lack of propylene glycol to distinguish its claimed invention from the prior art. The Court noted that this distinction was made during prosecution multiple times in response to the examiner’s rejections, and that Azurity had added negative claim limitations that specifically omitted propylene glycol from the scope of the claims.
The Federal Circuit also noted that Azurity used a “consisting of” transitional phrase to narrow the claims and relied on the closed transition to overcome the prior art. The Court explained that “consisting of” is a closed transition that limits the claim scope to only the recited components. By using this transition and not including propylene glycol as one of the claim components, Azurity effectively disclaimed propylene glycol from the invention. Therefore, the Court found that omission of propylene glycol during patent prosecution was “clean, unambiguous, and complete.”
Azurity argued that a pretrial stipulation between the parties, which stated that “[s]uitable flavoring agents for use in the asserted claims include flavoring agents with or without propylene glycol,” should preclude the application of the disclaimer. The Federal Circuit did not find this argument persuasive, concluding that the stipulation did not alter the clear and unambiguous disclaimer made during prosecution, nor did it affect the noninfringement finding. Since Alkem’s ANDA product contained propylene glycol and Azurity disclaimed inclusion of propylene glycol, there was no infringement.
