CAFC Affirms Prosecution Disclaimer and Non-Infringement in ANDA Case
| April 23, 2025
Case Name: AZURITY PHARMACEUTICALS, INC. v. ALKEM LABORATORIES LTD.
Decided: April 8, 2025
Before: MOORE, Chief Judge, CHEN, Circuit Judge, and MURPHY, District Judge. Opinion by Murphy.
Summary
The CAFC affirmed prosecution disclaimer and non-infringement in ANDA litigation, where the patentee’s sweeping disclaimer in the patent’s parent application applies to the continuation patent claims, despite the patentee’s belated efforts to take back disclaimer statements in a later, related application and to revise the scope of disclaimer to exclude the ANDA product.
Details
Azurity sued Alkem in the district court for an ANDA-induced infringement of certain claims of Azurity’s U.S. Patent No. 10,959,948 (“the ’948 patent”), directed to liquid vancomycin formulations for oral administration. The asserted claims use a close-ended “consisting of” transition and do not list propylene glycol, whereas Alkem’s ANDA product contains propylene glycol both as a co-solvent and as a component of the grape flavoring agent.
The district court found non-infringement where Alkem’s ANDA product contained propylene glycol, and Azurity, through prosecution history, had disclaimed any presence of propylene glycol from the patented formulations, with the disclaimer not overcome by certain language in the parties’ pretrial stipulation. At issue in the appeal are: (1) whether there was a clear and unmistakable disclaimer, (2) whether the stipulation precluded such disclaimer, and (3) whether the district court erred in finding no infringement. The CAFC addressed the issues in turn.
- Prosecution disclaimer
The CAFC went through prosecution history of Azurity’s relevant patent family.
The ’948 patent issued from application No. 16/941,400 (“the ’400 application”), which is a continuation of application No. 15/126,059 (“the ’059 application”). The ’059 application had been repeatedly rejected over a prior art reference Palepu which disclosed “a polar solvent including propylene glycol.” Throughout the prosecution, Azurity had made repeated attempts, through amendments and remarks, to distinguish over Palepu based on the absence of propylene glycol in the claimed invention.
Specifically, Azurity initially sought distinction using a negative limitation in some claims such as “wherein the oral liquid solution does not comprise a propylene glycol,” or introducing the close-ended “consisting of” language in other claims, such as “[a] liquid solution comprising a carrier consisting of” certain ingredients excepting propylene glycol. Both approaches failed as the Examiner found the negative limitation as lacking written description and the “consisting of” limitation with the preceding “comprising” transition as being indefinite. The §112 issues eventually forced Azurity to adopt the close-ended transition “consisting of” excluding unrecited propylene glycol from the claimed formulation, an amendment which led to allowance of the ’059 application. The claim amendments were accompanied by applicant’s repeated arguments, including a Rule 132 declaration by Azurity’s officer, emphasizing the claims’ lack of propylene glycol as a key distinction over Palelu. The Examiner expressly allowed the claims based on this exclusion.
The “consisting of” transition omitting propylene glycol was inherited by the ’400 application, which was allowed without rejection and resulted in the ’948 patent claims. For example, representative claim 5 recites a liquid formulation “consisting of: a buffering agent [selected from a recited group of buffering agents], water, a sweetener, a preservative [selected from a recited group of preservatives], vancomycin hydrochloride, and flavoring agent” (emphasis added), along with certain properties of the formulation.
Aside from the ’059 application, Azurity’s patent family includes No. 16/892,421 (“the ’421 application”)—the ’400 application’s grand-nephew claiming priority from the ’059 application. In the ’421 application, Azurity—after Alkem’s submission of Paragraph IV notice letter—apparently attempted to retract the disclaimer by stating: “For the record, Applicant did not disclaim propylene glycol when submitting the arguments in [the ’059 application], and reserves the right to claim propylene glycol in the instant and future cases in this patent family.”
Based upon the prosecution history, the CAFC found that Azurity clearly and unmistakably disclaimed any presence of propylene glycol from the ’948 patent. The CAFC was unpersuaded by Azurity’s non-disclaimer arguments including: (a) its “for the record” remarks made in the ’421 application are also relevant to the disclaimer analysis; and (b) the disclaimer of propylene glycol applies only to “the carrier” and not to “the flavoring agent.”
As for the “for the record” argument, the CAFC distinguished over the precedents where statements in the prosecution histories of patents from a common ancestor application may be relevant for claim interpretation in the related, later-issued patents. Here, the ’421 application and the ’400 application were prosecuted in parallel; there is no direct lineage from the ’421 application to the ’400 application; and the remarks at issue post-dated allowance of the asserted patent. To be consistent with the public notice function of the prosecution history, Azurity is barred from recanting its earlier disclaimer by the later, unilateral statement in the related application.
As for the “carrier” distinction, the CAFC pointed to the ’059 prosecution history where Azurity abandoned the “solution comprising a carrier consisting of” limitation in favor of the “consisting of” transition. While the CAFC acknowledged Azurity’s current argument that Palepu disclosed propylene glycol “only as a carrier” as opposed to a flavoring agent, such a distinction was never made during prosecution. “Just as the echo matches the shout,” the CAFC noted that the disclaimer scope is defined by the arguments as made, not as later refined.
- Pretrial stipulation
Azurity contended that a joint pretrial stipulation—stating that “suitable flavoring agents for use in the Asserted Claims include flavoring agents with or without propylene glycol”—precluded the application of the disclaimer. To Azurity, the stipulation would define the scope of “infringing flavoring agents” so that Alkem—with its product containing propylene glycol as part of the flavoring agent—could not rely on the disclaimer of propylene glycol, whereas Alkem argued that the stipulation was to simply clarify the general scope of the relevant flavoring agents in the field.
The CAFC sided with Alkem for several reasons. First, Azurity’s interpretation conflicted with another part of the stipulation stating that “Alkem does not dispute infringement except that it ‘contends that it does not infringe the Asserted Claims due to [the] presence of propylene glycol in Alkem’s ANDA Products.” Second, the disputed stipulation is set forth in a manner different from the rest of the undisputed facts each of which refers to meeting a limitation of any claim. Third, the disputed stipulation originated from Azurity’s concession over claim construction, admitting “that the plain and ordinary meaning of the claim term ‘flavoring agent’ includes flavoring agents without propylene glycol.” Based on the circumstances, the CAFC concluded that the stipulation does not preclude the disclaimer.
- The district court’s finding of non-infringement
After affirming the prosecution disclaimer and the pretrial stipulation, the CAFC found no error in the district court’s finding of non-infringement. The CAFC indicated that the existence of the prosecution history was a decisive factor. Absent the comprehensive disclaimer of any propylene glycol—either as an individual ingredient or as a concomitant of flavoring agent—Azurity may have had a colorable argument that propylene glycol would affect the flavoring of the product, and that propylene glycol and grape flavoring—both included in Alkem’s ANDA product—collectively are a flavoring agent, so as to read on the claimed “flavoring agent” while concurrently meeting the exclusion of “propylene glycol.” But the disclaimer precluded such a position.
Takeaways
This case underscores the lasting impact of prosecution history on claim scope, from an ancestor application to its descendent patent. Applicant cannot walk back a disclaimer in later, related applications—particularly those not in direct lineage. Also, in distinguishing prior art, care must be taken to avoid a broad, sweeping argument which could unknowingly over-restrict the claim scope to assert infringement.
