Lee International

The Korean Patent Act provides patent term extension for pharmaceutical patents to compensate for the period during which the patented invention could not be commercially exploited due to the time required to obtain marketing approval from the Ministry of Food and Drug Safety (MFDS).  Eligibility for such an extension is strictly limited to patents covering a new substance, defined as a substance whose active moiety has a novel chemical structure responsible for its pharmacological effect.  Patent term extension may be granted only once, based on the initial marketing approval, and only for a single patent, with the extension period capped at five years.  In addition, under Article 95 of the Patent Act, the scope of an extended patent right is limited to acts of practicing the patented invention in connection with the approved product or, where applicable, the specific approved use of that product.  Set forth below are recent court decisions addressing the scope of pharmaceutical inventions that qualify as “new substances” for patent term extension and the extent of protection afforded by extended patent rights.

Supreme Court Holds that Pegylated Compounds Are Not 'New Substances' for Patent Term Extension 

In the Avonex case, the patentee obtained marketing approval for a pharmaceutical product containing peginterferon beta-1a (interferon beta-1a conjugated with polyethylene glycol (PEG)) as its active ingredient and subsequently applied for a patent term extension (PTE).  The Ministry of Intellectual Property (MOIP), however, rejected the application on the ground that a previously approved drug containing interferon beta-1a as its active ingredient had already been approved for the same indication.  The MOIP reasoned that peginterferon beta-1a and interferon beta-1a share the same active moiety responsible for the therapeutic effect and that the PEG component does not constitute a new active substance. 

The Supreme Court upheld this position. The Court held that even if a component influences the efficacy or duration of action of a drug when combined with an active moiety, such component cannot be regarded as an active ingredient producing a pharmacological effect. The Court therefore found that the active ingredient responsible for the pharmacological effect of the patentee’s product was interferon beta-1a, rather than peginterferon beta-1a as a whole. Because interferon beta-1a was chemically identical to the active moiety contained in the previously approved drug, the Court concluded that the patentee’s product did not constitute a “new substance” under the Patent Act. Accordingly, the Supreme Court held that the patent was not eligible for patent term extension. (Supreme Court Decision 2021 Hu 11070, July 25, 2024).

Extended Patent Rights May Extend to Certain Salt, Prodrug, and Solvate Variants

Korean courts have taken a broad view of the scope of protection afforded by extended pharmaceutical patent rights.  In the Vesicare and Forxiga cases, generic manufacturers sought to avoid infringement by modifying the salt form of the original drug or developing a prodrug ester compound of the active ingredient.  The Supreme Court held that where such modifications could have been readily selected by a person having ordinary skill in the art, and the active ingredient, therapeutic effect, and intended use remain substantially identical to those of the original drug, the extended patent right extends to the salt-modified or prodrug versions as well (Supreme Court Decision 2017 Da 245798, January 17, 2019; Supreme Court Decision 2022 Hu 10210, February 2, 2023).

The same principle was applied in the Lixiana case. There, a generic manufacturer replaced the original “tosylate monohydrate” with a “propylene glycol solvate” in an effort to avoid infringement of the extended patent right. The Patent Court held that the propylene glycol solvate modification could have been readily adopted by a person having ordinary skill in the art and that the modified product exhibited substantially the same therapeutic effect, and intended use as the original drug. Accordingly, the court concluded that the scope of the extended patent right extends to the propylene glycol solvate as well (Patent Court Decision 2023 Heo 13438, October 23, 2024).

Extended Patent Rights May Extend Beyond the Initially Approved Indications 

In the recent K-CAB case, the patentee obtained marketing approval for the first indication (erosive gastroesophageal reflux disease) and the second indication (non-erosive gastroesophageal reflux disease), and based on those approvals, obtained a patent term extension.   Subsequently, the patentee secured additional marketing approvals for the same product with respect to a third indication (gastric ulcer) and a fourth indication (antibiotic combination therapy for Helicobacter pylori infection).  Seeking to avoid infringement of the extended patent right, a generic manufacturer obtained marketing approval only for the fourth indication and launched its product on the basis that the extended patent right should be limited to the indications underlying the original patent term extensions, namely the first and second indications.  

The Patent Court rejected the generic manufacturer's argument.  The court held that the scope of the extended patent right is not limited to the initially approved indications, on which the extension was based.  It reasoned that both the original indications and the subsequently approved indications fell within the scope of “acid-related diseases” and shared the same therapeutic mechanism, “gastric acid secretion inhibition achieved using a potassium-competitive acid blocker (P-CAB) with a mechanism that inhibits proton pumps.” Accordingly, the court found that the indications were identical in terms of use and concluded that the patent right, as extended based on the original approvals, also covered the generic product approved for the later indication (Patent Court Decision 2024 Heo 13541, January 23, 2025).  The Patent Court’s decision has since become final following the Supreme Court’s dismissal of the generic manufacturer’s appeal.  

In principle, the scope of an extended patent right is limited to acts of practicing the patented invention in relation to the product covered by the relevant marketing approval (or, where applicable, the specific approved use of that product).  However, Korean courts have interpreted this scope broadly, holding that the protection afforded by an extended patent right is not limited to compounds that are literally identical to the approved pharmaceutical product or to the specific indications underlying the approval.  Rather, the scope of protection may extend to pharmaceutical products that have substantially the same active ingredient, therapeutic effect, and intended use.  These decisions demonstrate the courts’ commitment to ensuring effective protection of pharmaceutical patents during the extended term and preventing circumvention through minor modifications to the approved products or indications.