First Korean IP High Court Decision on Scope of Term-Extended Substance Patent Covering Solvated Form of Substance

In the Intellectual Property High Court (“IP High Court”) decision 2023Heo13438, rendered on October 23, 2024, the IP High Court found that the scope of a term-extended pharmaceutical patent for a certain substance (the “Substance Patent”) covers the solvated form of an active ingredient, even when the Substance Patent does not have a claim directed to a solvated compound of the active ingredient. Kim & Chang represented the patent holder in this case.

Under the Patent Act, the term of a pharmaceutical patent can be extended up to five years, taking into account the period required to obtain product approval, which is necessary to commercially practice the pharmaceutical patent invention in accordance with the Pharmaceutical Affairs Act. The scope of the term-extended pharmaceutical patent covers only the product subject to the product approval that was the basis for extension (Article 95 of the Patent Act). Daiichi Sankyo, the patent holder in this case, held a substance patent for edoxaban, an active ingredient of the oral anticoagulant Lixiana Tab. The term for this patent was extended due to the time required to obtain product approval for Lixiana Tab.

Company A, a Korean pharmaceutical company, filed a petition with the Intellectual Property Trial and Appeal Board (the “IPTAB”) for a passive scope confirmation trial, seeking a decision affirming that edoxaban propylene glycol (the “Subject Solvate”), a solvated form of Lixiana Tab’s active ingredient edoxaban, does not fall within the scope of the Substance Patent. The IPTAB ruled in favor of Company A, and Daiichi Sankyo subsequently filed a lawsuit seeking the cancellation of the above mentioned decision with the IP High Court.

Company A argued that the Subject Solvate does not fall within the scope of the Substance Patent based on the following arguments:

(i)	As Lixiana Tab is the subject material for which the Substance Patent’s term was extended, the Subject Solvate, which has the modified solid form of its active ingredient, does not fall within the scope of the term-extended Substance Patent.

(ii)	The Substance Patent does not have a claim directed to the Subject Solvate and the description “solvate” was revised to “hydrate” during the prosecution history of the Substance Patent. Therefore, the Subject Solvate was consciously excluded from the scope of the Substance Patent.

In response, Daiichi Sankyo argued that (i) the Subject Solvate is covered by the scope of the Substance Patent based on the legal principles established by a Supreme Court precedent on the scope of effect and conscious exclusion, and (ii) changing the solid form of edoxaban to the Subject Solvate can be readily conceived by an ordinary person skilled in the art. Supporting arguments were presented with extensive prior art references and expert opinions.

Ultimately, the IP High Court accepted all of our firm’s arguments and cancelled the IPTAB decision on the grounds that (i) the solvate form of the active compound is included in the scope of the extended Substance Patent even if there is no explicit description of “solvate” in the claims, and (ii) even if the description of “solvate” was amended to “hydrate” during the prosecution history of the Substance Patent based on the rejection that the meaning of solvate was unclear, such solvate form of the active compound cannot be deemed to have been consciously excluded by the applicant.

Subject Solvate Falls Within Scope of Extended Substance Patent

Specifically, the IP High Court’s ruling that the Subject Solvate falls within the scope of the Substance Patent was based on a Supreme Court precedent, which held that “even if there is a difference in pharmaceutically acceptable salts, etc., between a pharmaceutical product whose approval was the basis for a patent term extension and the infringing product, if the difference is to the degree that an ordinary person skilled in the art could easily choose the alternative, and if the treatment effect or utility manifested by the pharmacological action of an active ingredient absorbed into the human body is substantially the same, the scope of the term-extended patent should be deemed to cover the infringing product.” Moreover, it further stated the following:

A.	Since propylene glycol was reported as a pharmaceutical solvate in the late 1970s, its superior characteristics and safety were well known, and propylene glycol solvate was commercialized and available in the market;

B.	According to the Ministry of Food and Drug Safety’s regulations, the Subject Solvate can be easily approved relying on Lixiana Tab’s approval data. This indicates that the Subject Solvate has substantially the same efficacy, safety and therapeutic effect as Lixiana Tab; and

C.	In light of the overall description in the specification of the Substance Patent and technical knowledge in the pharmaceutical field, an ordinary person skilled in the art would have no particular difficulty in selecting the Subject Solvate as an alternative solid form of edoxaban.

Subject Solvate Was Not Consciously Excluded from Scope of Substance Patent

A preliminary rejection was issued against the Substance Patent during the prosecution prior to the extension of the patent term, stating that the expression “solvate” in the claim was unclear and not supported by the specification. As a result, the expression “solvate” was amended to “hydrate,” an example of solvate. Despite the above, the IP High Court ruled that the Subject Solvate was not deemed to have been consciously excluded from the scope of the Substance Patent. This ruling considered the following:

A.	It is practically difficult to describe all embodiments of salts or solvates that may be theoretically possible at the time of filing an application for a substance patent, and the pharmaceutical industry has frequently used functional expressions such as “certain solvated compounds;”

B.	The examiner’s view that the term “solvate” was unclear appears to have been due to there being no consistent examination guidelines for the description of “solvate” at the time of examining the Substance Patent application; and

C.	For patent applicants, it was unclear to what extent “solvate” should have been specified and the amendment was made solely to obtain a patent registration promptly. As such, the amendment did not mean that the applicant intended to exclude “solvate” from the scope of the Substance Patent.

This decision is meaningful because it (i) disallowed the circumvention of the scope of the term-extended Substance Patent through a change in embodiment alone, and therefore (ii) supported the effective protection of the Substance Patent during the extended term. Furthermore, in this decision, the IP High Court advanced further from the Supreme Court precedent that held that the scope of a term-extended substance patent covers a change in the “salt form,” and ruled that the effect of a substance patent also covers the “solvate form” of the substance. In addition, even if an amendment was made to delete certain embodiments such as “solvate” during prosecution of the Substance Patent, the IP High Court ruled that such deletion alone did not necessarily indicate that the solvate was consciously excluded from the scope of the Substance Patent, demonstrating a flexible application of the file wrapper estoppel.

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