Introduction

Numerous generics have filed challenges to the validity of patent term extensions (PTEs) in South Korea in the past few years, raising various issues of first impression in an area of law that was little litigated prior to the implementation of the pharmaceutical patent-product approval linkage system in the country (a system analogous to the Hatch-Waxman regulatory framework in the United States).

In November 2017, the Supreme Court rejected two of the major validity issues raised by the generics (regarding the calculation of patentee delay to be subtracted from PTE, and the definition of the procedural requirement that a non-patentee marketing approval holder must be registered as a licensee at the Korean Intellectual Property Office (KIPO)), and as a result upheld the validity of numerous PTEs.

Since the Supreme Court's decisions in Autumn 2017, several Patent Court and Intellectual Property Trial and Appeal Board (IPTAB) decisions have addressed various other legal issues that were not decided by the Supreme Court. This update summarises and discusses the implications of these subsequent Patent Court decisions.

Claim construction and PTE eligibility issues

A generic sought to argue that the patent term of a patent claiming "compounds of formula… or salts thereof" could not be extended based on the approval of a solvate form of the claimed compound formula, since the solvate form was not expressly claimed or disclosed in the patent. The Patent Court rejected this argument on the basis that making a solvate form of the approved drug would necessarily practice the compound patent at issue, so the approval was necessary in order to practice the patent for PTE purposes.

Both genus and species patents on approved product can be extended

Unlike the United States and Europe, Japan and South Korea allow multiple patents to be extended based on a single product approval as long as all of the patents cover the product. However, one recent Patent Court case involved a generic disputing whether it was proper to allow a PTE for a genus compound patent in relation to an approved drug if there was also an existing species patent covering the same drug.

The generic had previously unsuccessfully challenged the validity of the species patent, which was confirmed to be novel and inventive over the genus patent. The generic then creatively argued in a separate case that because the species patent was effectively determined not to have been readily conceivable from the genus patent, the genus patent should not be interpreted to cover the species compound for purposes of PTE eligibility, rendering the PTE invalid.(1) Alternatively, the generic argued that the genus patent should be invalid as double patenting the approved compound together with the species patent.

The Patent Court rejected the double patenting argument since any double patenting issue would have arisen after the genus patent had already issued, so only the species patent would be subject to invalidation on this basis. The Patent Court also rejected the genus/species argument as improperly conflating the requirements for PTE validity versus patent validity and confirmed that as long as the approved product was within the scope of the genus patent, the genus patent was eligible for PTE regardless of the existence of a subsequent species patent on the approved compound.

Patent eligible for PTE as long as one claim covers the approved product

Another PTE invalidation argument was raised by a generic at the IPTAB, on the basis that because not all of the claims in the extended patent covered the approved product, the PTE for the patent was invalid. The IPTAB rejected the argument in view of Article 134(1)(i) of the Patent Act, which simply states that a PTE may be invalidated if the PTE application does not cite any basis regarding why the patent required a regulatory approval to practice. The IPTAB understood this to mean that as long as the PTE application cites patent claims that cover an approved product (and thus could not be practiced prior to approval), a PTE granted in response to the application is valid even if other claims may not cover the product.

The IPTAB additionally pointed out that the scope of the patent right during the extended term is limited to covering only the approved drug in any case. Thus, to invalidate the PTE on the basis of claims that are wholly irrelevant to the enforceable scope of the patent during the PTE would be contrary to the basic aim of the PTE system to compensate the patentee for the loss of enforceable term due to regulatory delays.

This IPTAB decision was not appealed, so has become final and conclusive.

PTE eligibility not limited by pharmaceutical regulatory definitions and terminology

Another disputed issue arose in the context of an appeal to the Patent Court of a final rejection of a PTE application based on a geometric isomer drug which was in turn based on an earlier approved drug. The issue involved the requirement in South Korea that a PTE may be granted only for the first Korean approval of a 'new substance' under Article 7 of the Enforcement Decree of the Patent Act (similar to the United States, where a PTE is granted only for the first commercial marketing of a 'drug product').

However, the KIPO has taken a much more restrictive interpretation of eligible new substances compared to the United States and Europe by limiting PTEs to only new drug approvals under the Pharmaceutical Affairs Act. In particular, South Korea has been treating new isomer forms of existing drugs as incrementally modified drugs (IMDs) for regulatory purposes which are not considered new drugs under the Pharmaceutical Affairs Act, contrary to the United States and Europe, where even optical isomers are treated as new chemical entities compared to their racemic mixtures, in addition to geometric isomers. Thus, despite the fact that the geometric isomer drug in question had a completely different structure and drug efficacy compared to the earlier approved drug, the KIPO rejected the PTE because the subject drug was approved as an IMD, not a new drug.

However, the Patent Court ruled that there was no reasonable basis to limit 'new substances' under Article 7 to 'new drugs' under the Pharmaceutical Affairs Act, given the different purposes of the two statutory schemes. Moreover, the Patent Court looked to the plain language of Article 7, which indicates that as long as a substance was not previously approved, the substance should be considered a new substance and its approval a proper basis for a PTE.

The KIPO did not appeal the Patent Court's ruling, so it appears that the KIPO will change its practice going forward to allow PTEs simply as long as the approved active ingredient is different from earlier approved ingredients, without reference to pharmaceutical regulatory definitions concerning new drugs. However, because this case specifically dealt with geometric isomers, further clarification may be needed as to whether other isomer types or derivatives/metabolites will be considered by the KIPO to support new PTEs, even in view of the Patent Court's ruling.

For further information on this topic please contact Mee Sung Shim, Tae Min Kim or Inchan Andrew Kwon at Kim & Chang by telephone (+82 2 3703 1114) or email (msshim@kimchang.com, tmkim@kimchang.com or ickwon@kimchang.com). The Kim & Chang website can be accessed at www.kimchang.com.

Endnotes

(1) This issue was significant because the species patent issued too late to be eligible for any PTE, so the genus patent was due to expire later than the species patent.

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