Holding: Statements made during prosecution of a patent application are not relevant to the interpretation of the claims of a related patent that was issued before the later-filed patent application.
Azurity sued Alkem for patent infringement of US Patent No. 10,959,948 after Alkem submitted an Abbreviated New Drug Application (“ANDA”) for a drinkable liquid formulation containing the antibiotic vancomycin for treatment of Clostridium difficile infection. The ‘948 Patent claims a stable liquid formulation for oral administration, consisting of a buffering agent, water, a sweetener, a preservative, vancomycin hydrochloride, and a flavoring agent.
During prosecution, the ‘948 Patent was approved without rejection. However, the ‘948 Patent was a continuation of US Patent Application No. 15/126,059, which had been rejected over US Patent Publication No. 2016/0101147 to Palepu, which discloses an intravenously administered liquid formulation containing vancomycin with a polar solvent including propylene glycol.
To overcome the Palepu reference in the prosecution of the ‘059 Application, Azurity amended the claims of the ‘059 Application to use the closed transition “consisting of” instead of the open-ended transition “comprising” to the closed transition “consisting of” to exclude the addition of propylene glycol and to overcome the rejection based on Palepu. Azurity argued that the absence of propylene glycol in the claimed invention distinguished the claimed invention from Palepu. The application that led to the ‘948 Patent was filed as a continuation of the ‘059 Application after the ‘059 Application was allowed.
After Azurity filed the current case against Alkem, Azurity filed US Patent Application No. 16/892,421, which claimed priority to the ‘059 Application. In response to an office action in the ‘421 Application, Azurity stated that: “For the record, Applicant did not disclaim propylene glycol when submitting the arguments in U.S. 15/126059, and reserves the right to claim propylene glycol in the instant and future cases in this patent family.” The Examiner allowed the ‘421 Application, but did not address Azurity’s statement regarding disclaimer of propylene glycol.
The district court found that Alkem did not infringe, as Azurity’s statements during the prosecution of the ‘059 Application clearly and unmistakably disclaimed propylene glycol from the invention claimed in the ‘948 Patent, and the Alkem formulation included propylene glycol. The Federal Circuit upheld this decision. Prosecution history disclaimer permits claim scope to be surrendered by clear and unmistakable disavowal in the patent prosecution history. Any explanation, elaboration, or qualification made by the inventor during examination is relevant to determine the scope of the actual invention disclosed. Disavowal of claim scope is binding, even if the patentee says more than necessary to overcome a prior art rejection.
Azurity argued that the statement made in the prosecution of the later filed ‘421 Application, alleging that it did not disclaim the addition of propylene glycol, should be considered in determining the scope of the claims of the ‘948 Patent. Statements made in applications descending from a common ancestor may be relevant for interpreting claims in related patents. However, typically these statements are relevant only for later issued patents. In this case, Azurity’s statement in the prosecution of the ‘421 Application was made after the ‘948 Patent had already been allowed. These later statements are not be considered when determining the scope of the claims of an earlier issued patent.
The Federal Circuit found that the prosecution history of the ‘948 Patent clearly showed disavowal of propylene glycol in the claimed formulation, since Azurity specifically used the “consisting of” language to exclude propylene glycol and overcome the Palepu reference. The amendments and arguments made in the prosecution of the ‘059 Application apply directly to the ‘948 Patent because the ‘948 Patent was a continuation of the ‘059 Application.
Azurity also argued that one of the pretrial stipulations for this case precluded the application of the disclaimer of propylene glycol. The agreed upon stipulation stated: “Suitable flavoring agents for use in the Asserted Claims include flavoring agents with or without propylene glycol.” The Federal Circuit found that this stipulation should be read to mean that a flavoring agent does not need to include propylene glycol. Reading this stipulation broadly to preclude disclaimer of propylene glycol, as suggested by Azurity, would be inconsistent with Alkem’s noninfringement arguments.
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