Azurity Pharms., Inc. v. Alkem Labs. Ltd

Authored by: Jeremy J. Gustrowsky

In a recent decision, the Federal Circuit affirmed that Azurity Pharmaceuticals, Inc. could not enforce its U.S. Patent No. 10,959,948 against Alkem Laboratories Ltd. because Azurity had clearly and unmistakably given up any claim to formulations containing propylene glycol during the patent’s prosecution. The case centered on a non-sterile, drinkable liquid formulation of the antibiotic vancomycin, which is especially useful for children and elderly patients who have trouble swallowing pills.

During the patent application process, Azurity faced a prior art reference (Palepu) that disclosed vancomycin formulations with propylene glycol. To overcome this, Azurity amended its claims to use the phrase “consisting of”—a term that limits the patent to only the ingredients listed—and repeatedly told the Patent Office that its invention did not include propylene glycol. The examiner agreed and allowed the patent on that basis. When Alkem later sought approval for a generic version that did contain propylene glycol, Azurity sued for infringement.

Azurity argued that a pre-trial stipulation about “suitable flavoring agents” should allow for some propylene glycol in the accused product, but both the district court and the Federal Circuit rejected this. The courts found that the stipulation only addressed the general meaning of “flavoring agent” and did not override the clear prosecution history disclaimer. Because Alkem’s product included propylene glycol, it was outside the scope of Azurity’s patent claims.

This case is a textbook example of how statements and amendments made during patent prosecution can have lasting consequences, particularly when including strong narrowing terms such as “consisting of” in the claim. By disavowing propylene glycol to get its patent allowed, Azurity could not later claim infringement against a product containing that very ingredient. The Federal Circuit’s decision underscores the importance of careful claim drafting, avoiding specific narrowing language, and overall prosecution strategy.