In a recent decision, the Trial Board of the Korean Intellectual Property Office applied the doctrine of (prosecution history) estoppel to a case where the patentee expressed a clear intention to surrender a feature shown, through the comparative data given in the patent specification, inferior to an element of a patent claim in the remarks submitted in response to the Examiner's rejection, even though no amendment was made to the claim element during the prosecution of the patent application (Trial Board Case No. 2020 Dang 428 rendered on September 22, 2020; appeal pending).

▶Background of the Case

A. Subject Invention and Prosecution History

The claimed invention of the subject patent related to a premixed formulation of dexmedetomidine that may be used in the perioperative care of a patient or for sedation. During the prosecution of the patent application, the Examiner rejected the claimed invention for lack of inventiveness over prior art references disclosing a dexmedetomidine formulation provided as a 100 µg/ml concentrate that must be diluted prior to administration to a patient. In the remarks, the applicant argued that the claimed invention was distinguished from the prior art, as the gist of the claimed invention resided in a premixed dexmedetomidine formulation that was pre-diluted to a use concentration (e.g., 4 µg/ml) capable of direct administration to a patient without dilution, and amended claim 1 as follows (amended part is underlined): 

Claim 1.  A ready to use liquid pharmaceutical composition for parenteral administration to a subject, comprising dexmedetomidine or a pharmaceutically acceptable salt thereof at a concentration of 0.005 to 50 µg/ml disposed within a sealed glass container wherein the composition is administered to the subject without dilution.

Although the prior art references were silent on the container of the dexmedetomidine formulation, the applicant also argued in the remarks that the premixed dexmedetomidine formulation stored in a glass container maintained greater dexmedetomidine potency as compared with those stored in a plastic container, a CR3 elastomer copolyester ether container or a PVC container after a five-month storage period, thereby highlighting the advantage of the glass container in terms of stability. 

The patent application was allowed after the amendment and remarks. 

B. Scope Confirmation Trial

Company A, a competitor of the patentee, lodged a scope confirmation trial, which is a declaratory action as to whether the accused party’s mode of practice falls within the scope of a patent claim. Company A's mode of practice differed from claim 1 of the subject patent only in that a liquid premixed composition of dexmedetomidine was disposed within a sealed polypropylene container, instead of a sealed glass container. 

The issue of the case was whether the polypropylene container in Company A's mode of practice was equivalent to the glass container of the claimed invention.  Specifically, the issue focused on whether the patentee intentionally excluded the polypropylene container from the scope of the claimed invention during the prosecution of the patent application. 

In this regard, the patentee argued that a polypropylene container was equivalent to a glass container because glass and polypropylene both were representative materials used for a container for injection; the "glass container" recited in the original claim 1 was never amended during the prosecution of the patent application and no intentional exclusion of the polypropylene container was made since the cited prior art references did not disclose a polypropylene container; and it was merely emphasized in the remarks that a glass container showed higher stability as compared with particular containers such as CR3 and PVC containers, without comparing a glass container with a plastic container in a broad sense or a polypropylene container in terms of stability. 

▶The Trial Board Decision

The Trial Board decided that Company A’s mode of practice fell outside the scope of the claimed invention, under the reasoning that the polypropylene container in Company A's mode of practice was intentionally excluded during the prosecution of the patent application. Specifically, the Trial Board found that the patentee's intention to exclude the polypropylene container was made clear in the remarks, even if no amendment was made in regards to the glass container recited in claim 1; and that such exclusionary intention could be further garnered from Example 1 given in the patent specification, as illustrated below:

(i)  In Example 1, a glass vial, a glass ampoule, a  PVC flexible container, a CR3 flexible container, a VisIV^TM plastic flexible container, and an Ansyr syringe^® were tested for suitability as packaging containers of the premixed dexmedetomidine composition. The VisIV plastic flexible container is made from polypropylene. 

(ii) According to Table 1 in Example 1, the potency of the premixed dexmedetomidine composition in glass containers remained over 98% after a storage period of five months, whereas that in the VisIV container made from polypropylene was found to be about 95% after two weeks and about 90% after five months. Further, Table 2 in Example 1 indicates that the premixed dexmedetomidine composition in the VisIV container had high impurity levels after two weeks. Therefore, a polypropylene container was found to be inferior to a glass container in terms of storage stability--evincing the patentee’s intentional choice of glass container to the exclusion of, e.g., polypropylene container.  

In view of the above, the Trial Board concluded that the competitor’s composition disposed in a polypropylene container fell outside the scope of claim 1.

The patentee’s appeal against the above decision is currently pending before the Patent Court.