The Korean Patent Court recently rendered a decision that the doctrine of (prosecution history) estoppel is applicable to a case where the scope of a claim is narrowed in response to an Examiner’s rejection for failure to satisfy the claim description requirement, for the reason that those species elements which are not included in the (Markush) group of species newly introduced, by way of claim amendment, to narrow the scope of a generic expression recited in the original claim can be considered as the patentee’s intentional exclusion of those non-listed species (Patent Court Case No. 2019 Heo 3083 rendered on March 20, 2020; final and conclusive). 

▶Background of the Case 

A. Subject Invention and Prosecution History 

The claimed invention of the subject patent relates to a multilayer tablet containing a release controlled dosage form of sarpogrelate hydrochloride.  During the prosecution of the patent application, claim 1 was amended in response to the Examiner’s rejection for failure to satisfy the claim description requirement of clarity and support, the relevant elements involved being featured below. 

B. Scope Confirmation Trial 

Company A, one of the competitors of the patentee, lodged a patent claim scope confirmation trial, which is a declaratory action as to whether the accused party’s mode of practice falls within the scope of patent claims.

The issue of the case was whether the sustained release agents of Company A’s product were equivalent to those of the claimed invention. Specifically, the issue focused on whether the sustained release agents, which are not listed in amended claim 1, could be considered as the patentee’s intentional exclusion, ergo, those of the defendant’s product. 

The Trial Board decided that Company A’s mode of practice fell outside the scope of the claimed invention, under the reasoning that polyethylene oxide and hydroxyethyl cellulose of Company A’s product were intentionally excluded to overcome the Examiner’s rejection for failure to satisfy the claim description requirement during the prosecution of the patent application. Thereafter, the patentee filed an appeal before the Patent Court.

▶The Patent Court Decision 

The Patent Court, while upholding the Trial Board decision, ruled that Company A’s mode of practice is deemed to have been intentionally carved out from the scope of the claim in light of the following facts: 

(i) During the prosecution of the patent application, the claims were rejected for lack of clarity as well as lack of support, and the sustained release agents of the subject invention were limited based on the working examples of the subject patent to overcome the rejection. 

(ii) The patentee did not traverse the Examiner’s rejection or explicitly state in the remarks that the sustained release agents excluded by the amendments also achieved substantially the same effect. 

Further, the Patent Court held that if a patentee narrowed the scope of a claim in response to an Examiner’s rejection by way of changing a generic expression recited in the claim to specific species or a Markush group thereof, while choosing not to pursue the procedural right to file an appeal against the rejection, the patentee is estopped from claiming that the accused product comprising those species elements, which are not listed in the amended claim, falls within the scope of the protection of the claim.