In Azurity Pharmaceuticals, Inc. v. Alkem Laboratories Ltd., No. 23-1977 (Fed. Cir. Apr. 8, 2025), the Federal Circuit affirmed the District of Delaware’s ruling that Alkem’s Abbreviated New Drug Application (ANDA) product did not infringe Azurity’s U.S. Patent No. 10,959,948 (“’948 patent”) due to a clear and unmistakable prosecution disclaimer of propylene glycol.
Background
Azurity’s ’948 patent claims drinkable, non-sterile liquid formulations of vancomycin, tailored to pediatric and geriatric patients. The asserted claims used a “consisting of” transition, listing specific ingredients but omitting propylene glycol. During prosecution, Azurity’s predecessor application had been repeatedly rejected over Palepu (U.S. Pat. App. Pub. No. 2016/0101147), which disclosed vancomycin formulations including propylene glycol.
To overcome these rejections, Azurity amended its claims to include the “consisting of” transition and repeatedly emphasized the absence of propylene glycol. The examiner’s notice of allowance explicitly cited this absence as the basis for allowance. Although a later sibling application (not in the same line of priority) included a statement purporting to reserve the right to claim propylene glycol, the Federal Circuit found this late-stage statement irrelevant and ineffective to undo the earlier disclaimer.
Key Legal Holdings
- Clear Prosecution Disclaimer
The court held that Azurity “clearly and unmistakably” disclaimed propylene glycol to distinguish its claims from Palepu, citing Data Engine Techs. LLC v. Google LLC, 10 F.4th 1375 (Fed. Cir. 2021), and TriVascular, Inc. v. Samuels, 812 F.3d 1056 (Fed. Cir. 2016). The disclaimer applied broadly across all claim limitations due to Azurity’s sweeping and repeated statements. - Effect of “Consisting Of” Language
Use of the closed “consisting of” transition further limited the claims to exclude unlisted components like propylene glycol. Citing Norian Corp. v. Stryker Corp., 363 F.3d 1321 (Fed. Cir. 2004), and AFG Indus., Inc. v. Cardinal IG Co., 239 F.3d 1239 (Fed. Cir. 2001), the court emphasized that such transitions typically exclude any additional components. - Ineffectiveness of Later Statement in Related Prosecution
A disclaimer made in a parent application binds later continuations (Elkay Mfg. Co. v. Ebco Mfg. Co., 192 F.3d 973 (Fed. Cir. 1999)), but a later, unilateral attempt to retract that disclaimer in a grand-nephew application (filed in parallel) did not negate the clear disclaimer made during the original prosecution. - Interpretation of Pretrial Stipulation
Azurity’s reliance on a discovery stipulation—that flavoring agents may contain or omit propylene glycol—did not undo the prosecution disclaimer. The court, citing Akamai Techs., Inc. v. Limelight Networks, Inc., 805 F.3d 1368 (Fed. Cir. 2015), found the stipulation did not equate to a concession on infringement or override the prosecution record. - Non-Infringement Finding Supported by ANDA Content
Since Alkem’s ANDA product contains propylene glycol, and the patented formulation disclaimed that compound, the Federal Circuit affirmed the finding of non-infringement. The case underscores the principle, restated from Ferring B.V. v. Watson Labs., Inc.-Fla., 764 F.3d 1401 (Fed. Cir. 2014), that an ANDA’s defined composition controls the infringement analysis under Hatch-Waxman.
Takeaways
This decision reinforces the enduring power of prosecution disclaimer, especially when paired with the “consisting of” claim transition. Practitioners should be mindful that:
- Statements made to overcome prior art will likely limit claim scope—even if arguably broader than necessary.
- Subsequent clarifying or contradictory statements in sibling applications cannot override earlier disclaimers.
- Closed claim language (“consisting of”) combined with clear disclaimer can preclude infringement where additional components are present.
Careful claim drafting and prosecution strategy remain essential tools in preserving enforceable patent scope.
By Charles Gideon Korrell