Korea has become one of the most closely watched venues for pharmaceutical and biotech patent disputes, and several recent decisions offer useful insight into how Korean courts are approaching innovator and generic competition.

Three decisions in particular — involving a 13-valent pneumococcal vaccine, a P-CAB gastrointestinal drug, and a DPP-4 inhibitor — highlight three themes in Korean pharmaceutical patent litigation: (i) a broad recognition of legitimate regulatory and research activities, (ii) meaningful protection for core compound patents and patent term extension (“PTE”), and (iii) close scrutiny of secondary patents that seek to extend exclusivity beyond the core patent term.

Although each case turned on its own facts, together they shed light on enforcement, patent lifecycle management, and the timing of generic or biosimilar entry in Korea.

1. K bioscience vs Pfizer: PCV13 vaccine and the scope of the Bolar exemption

In May 2025, the Korean Supreme Court affirmed a decision in favor of SK bioscience in Pfizer’s infringement action over 13-valent pneumococcal conjugate vaccine (PCV13) technology. Pfizer had alleged that SK bioscience’s supply to a Russian partner of both the individual conjugate bulk and finished PCV13 product infringed its Prevnar 13 composition patent. The first-instance tribunal sided with Pfizer, but the IP High Court reversed and the Supreme Court affirmed the reversal.

The case turned chiefly on the Bolar (research-and-testing) exemption. SK bioscience relied on it, and rather than disputing that the exemption applied in principle, Pfizer argued for a narrow reading of its scope under the Korean Patent Act. The IP High Court rejected Pfizer’s narrowing arguments on both strands of supply. As to the individual conjugates, Pfizer’s contention that supplying all of the conjugates that together make up the 13-valent product amounted to infringement was not accepted. As to the finished product, Pfizer argued that the supply went beyond genuine research and testing and that, because it was aimed at obtaining a marketing approval in Russia rather than in Korea, it should fall outside the exemption; the court rejected both points, holding that research and testing directed at securing a foreign marketing approval can come within the exemption.

The notable feature of the decision is that the exemption was interpreted more broadly than Pfizer had argued. The decision confirms that, depending on the facts, the exemption may extend not only to the party conducting the research itself, but also to upstream suppliers, and may cover activities directed toward obtaining foreign marketing approvals. At the same time, the courts emphasized that the analysis remains highly fact-specific, particularly with respect to manufacturing activities and territorial considerations.

2. K-CAB (tegoprazan): compound patent, PTE, and crystalline form

K-CAB (tegoprazan), HK inno.N’s P-CAB-class drug for gastroesophageal reflux disease, is protected by a compound patent (expiring August 2031, following a PTE from its original December 2026 term), a crystalline-form (polymorph) patent (March 2036), and non-listed use and formulation patents (2036). The two main litigation tracks have now largely resolved — in opposite directions.

The first track concerned the scope of the patentee’s enforceable rights during the extended term. Under Article 95 of the Korean Patent Act, a PTE confines the patentee to the approved product and its approved medicinal use. The IP High Court began from an important premise: the “medicinal use” that defines the extended scope under the Korean Patent Act is not the same as the regulatory “indication” under the Pharmaceutical Affairs Act, so the comparison is not indication-against-indication. The generic challengers had filed scope confirmation actions seeking declarations of non-infringement, relying on skinny-label products that excluded K-CAB’s first-approved indications (erosive and non-erosive gastroesophageal reflux disease). The court rejected that approach, and the patentee’s position was subsequently upheld by the Supreme Court. Its method was to derive the medicinal use of the patented invention from the first-approved indication — here, the compound’s acid-pump-inhibitory action — and then to ask whether the later, skinny-label indications fell within that use. Because indications such as gastric ulcers are likewise treated through the same acid-pump-inhibitory mechanism, they were held to lie within the extended scope. The practical reach of the extension therefore turns on the level of generality at which that underlying use is characterized, rather than on any identity between the specific indications themselves.

On the crystalline-form patent, however, the generics ultimately prevailed, with the Supreme Court dismissing HK inno.N’s appeal. As a result, generic manufacturers are generally expected to be able to enter the market upon expiry of the compound patent in 2031. Importantly, the decision did not establish any general hostility toward polymorph patents. Rather, it turned on the challengers’ ability to demonstrate that their products employed a distinct crystalline form identified through polymorph screening. Products using the patented form, or forms that readily convert into it, may still raise infringement issues.

3. Gemigliptin (Zemiglo): secondary use patent invalidated, earlier generic entry

Korean courts and tribunals have continued to scrutinize follow-on patents used to prolong exclusivity. In the litigation over LG Chem’s DPP-4 inhibitor gemigliptin (Zemiglo), generic challengers ran two tracks against the same later-expiring use patent (2039): a negative scope confirmation action and an invalidation action. The appellate results diverged — the IP High Court sided with LG Chem on scope confirmation but with the generics on invalidity (lack of inventive step). In 2026 the Supreme Court confirmed the invalidation, rendering the use patent retroactively void and mooting the scope confirmation result. Generic entry is now keyed to the compound patent’s expiry in January 2030, the salt/hydrate patent (2031) having already been designed around.

The case underscores two features of Korean practice: a secondary use patent must rest on a clear technical contribution and robust disclosure to survive a validity challenge; and running invalidation and scope confirmation actions in parallel remains an effective route for generic challengers. More broadly, the decision illustrates the level of scrutiny that Korean courts and tribunals may apply when assessing follow-on patents that seek to extend exclusivity beyond the life of the core compound patent.

Key Takeaways

Taken together, these decisions highlight three themes that are likely to remain important in Korean pharmaceutical patent litigation.

First, Korean courts appear willing to recognize a relatively broad range of legitimate research and regulatory activities when applying the Bolar exemption, while continuing to assess such activities on a detailed factual basis.

Second, core compound patents and valid PTEs continue to receive meaningful protection. The K-CAB litigation demonstrates that generic companies cannot necessarily avoid an extended patent simply by carving out particular approved indications if the underlying approved medicinal use remains the same.

Third, Korean courts and tribunals continue to scrutinize secondary patents carefully, particularly where such patents are relied upon to extend exclusivity beyond the life of the core compound patent. The invalidation of the gemigliptin use patent illustrates the importance of demonstrating a genuine technical contribution and a robust inventive-step position.

Overall, Korea remains a jurisdiction where strong core patent rights can be effectively enforced, while exclusivity strategies built on secondary patents are subject to meaningful validity scrutiny.

While these decisions arise from pharmaceutical patent disputes, the underlying judicial approaches may also be of broader interest to IP practitioners monitoring developments in Korean patent litigation.