Japan's Pharmaceutical Patent Linkage System: What the 2025 Reforms Mean for Innovators and Generic Manufacturers

Introduction: Patent linkage is essentially a form of regulation where a pharmaceutical regulator typically being a drug regulatory authority of a nation cannot issue a marketing authorization to the generic and biosimilar drug unless certain requirements concerning the status of patent of the concerned originator reference drug are fulfilled. This concept of patent linkage was firstly put forward by the United States of America through the Hatch-Waxman Act.

The establishment of the system of patent linkage is made obligatory under the CPTPP (earlier known as the TPP11). As a signatory to the CPTPP agreement, Japan is obliged to introduce the patent linkage system. It must be emphasized here that the patent linkage system of Japan is based on the measures taken through administration and not statutory, and that the questions regarding patents in the approval process of generic drugs are decided by the Ministry of Health, Labour and Welfare (MHLW), even in the absence of any statutory provision for such decision making. Being notified through the administrative process, not statutory, the system has been subject to academic criticism owing to its structural vagueness and failure to satisfy the rule of law requirements.

The Japanese style patent linkage system was put into operation back in 1994 and, at the beginning, it was only relevant for substance patents. The limited coverage of the system is believed to be associated with the nature of the MHLW being a health and safety regulator rather than a patent authority. In 2009, the scope of the system was widened to include use patents along with substance patents.

In spite of the long history of the system's operation, policy discussions regarding this system in Japan started recently. Nonetheless, there is a certain change. The recently adopted 2025 reform covers also the issue of biosimilars and, made the proposal of an Expert Committee pilot as provided for in the notifications of the MHLW issued in October and November 2025 respectively.

The 2009 Framework

Japan has had a patent linkage system using administrative notifications from the Ministry of Health, Labor and Welfare (MHLW) since 1994, with full implementation since the issuance of the 2009 notification, both of which have no legal standing.

The process consists of two parts. First, during the generic approval process, originator firms can voluntarily provide information on related patents by means of the “Drug Patent Information Report,” although the information is never made public. The MHLW looks for patents on either substance or use of the active ingredient. If such patents exist, it does not reject approval but merely suspends it until the expiration of the patent, even as it allows applications on non-patented indications to go forward.

Particularly, the 2009 Notification denies marketing approval to a generic drug in two scenarios: (1) where a patent covers the active ingredient itself, making independent manufacture impossible, approval shall not be granted; and (2) where a patent covers only certain indications, dosage, or administration ("indications, etc."), approval shall be permitted for non-patented uses, with approval withheld only for the patented indications.

Second, prior to the NHIP drug price listing process, generic producers are advised to resolve any outstanding concerns through consultations with the patent holder. The failure of such consultations will not prevent listing but might be followed by patent litigation in the future.

The regime is characterized by the absence of a patent register, pre-listing notification to the patent holder, and market exclusivity for generics, and was established separately from the U.S. Hatch-Waxman approach. Furthermore, its compliance with both the PMD Act and Japan's TPP11 obligations is disputed, as it introduces only one out of two possible approaches according to TPP11 Article 18.53.

However, the regime receives constant academic criticism because of its deviation from the rule-of-law principle. It includes the absence of legislative backing, lack of sufficient procedural safeguards, limited avenues of appeal, encouragement of litigation against generics, and ambiguous process, which is considered a "constructive ambiguity" that favors originators by prolonging administrative process.

The Foundation

There was no explicit statement in the 2009 Notification that biological products are covered by the patent linkage system, an uncertainty which continued till the October 8, 2025 Notification, which stated that the patent linkage system is applicable to biological products as well.

In the year prior to the above-mentioned amendment, the same uncertainty came into play during legal cases involving two different cases, called the Samsung Bioepis cases. In both these cases, Samsung Bioepis, a biosimilar producer, had sought permission from the MHLW for marketing its product. Both Regeneron and Bayer Healthcare had made the MHLW and PMDA aware of the fact that the biosimilars were going to infringe upon the patents of the reference biologics.

The case concerning Bayer Healthcare proceeded to the 40th Civil Division, where it was decided on October 28, 2024. The other case concerned Regeneron and was heard by the 29th Civil Division on December 16, 2024. The court rejected both cases but on different grounds.

In the Tokyo District Court's 40th Civil Division decision, the court held that a patentee's report to MHLW asserting patent conflict, even if later found to be false, does not constitute unfair competition unless special circumstances exist, namely, that the notification, despite its formal appearance as patent-linkage information, was in substance aimed at disadvantaging the applicant and securing a competitive advantage for the patentee, to a degree significantly inappropriate to the system's purpose. Applying this standard, the court found the notification was in fact false, but concluded that these special circumstances were absent, and accordingly denied the injunction.

In turn, the 29th Division considered that even the false notification could be excluded from responsibility if such notification was reasonable considering the aim of the patent linkage system. Here the court considered the knowledge of the patent holder about the absence of the infringement, whether the notification was intended as a cover-up of malicious allegations, and whether the content of the notification was within socially acceptable limits.

In another development, the MHLW was also working on an expert opinion process for handling patent disputes in the linkage process. The May 2025 letter by PhRMA objected to this development on grounds that MHLW lacked the necessary expertise to adjudicate on any infringement, and also because the non-binding opinion process would bring about market uncertainty. The main issue raised was that the process failed to solve the main problem, which was that the patent holder was not adequately notified about any competing applications. It recommended to MHLW that it require notice and withholding of NHI price listing for products in dispute.

While no direct causative relationship can be drawn from this to the October notification, the two cases involved the same unresolved issue of treatment of biosimilar products under patent linkage process.

The October 8, 2025 MHLW Notification

The Ministry of Health, Labour and Welfare announced Joint Notification No. Isei-San-Jo-Ki-Hatsu No. 1008-1 and Yaku-Yaku-Shin-Hatsu No. 1008-5 on October 8, 2025, replacing the previous 2009 Two Directors' Notification, which had operated Japan's patent linkage system for over fifteen years without any explicit legislative basis.

The most important substantive change of this notification is the inclusion of the biosimilar drugs under the scope of the patent linkage system. Before, biosimilar drugs were regulated only "in accordance with" the regulations of generic small molecule drugs. In the current regulation, the biosimilar drugs are now equally recognized as a follow-on product.

As for the approval examination, the notification keeps the basic structure of a two-tiered system. In other words, the approval for follow-on product will not be granted if an active ingredient of originator drug is substance patented; however, when the certain indications or dosage forms are use patented, the approval will be granted for other indications.

In terms of the process, the notification provides that patentees or originator companies are to provide a "Patent Information Reporting Form" on any relevant substance or use patents prior to the expiration of the re-examination term of the originator drug, or within 30 days after any new patent applications. It should be noted that any patent which has not been reported using the Patent Information Reporting Form will not be taken into account during the follow-on drug approval process in principle.

The Patent Information Reporting Form is not disclosed to the public.

In addition to this, the notification retains the existing regulation regarding the need to coordinate between the parties prior to the listing on the NHI price list of products subject to any patent disputes in order to ensure an ongoing supply of such products.

The November 14, 2025 MHLW Notification

On November 14, 2025, the Pharmaceutical Evaluation Division of the MHLW issued a notice (Yaku-Yaku-Shin-Hatsu No. 1114-1), launching, on a provisional trial basis, an Expert Committee system to help confirm patent conflicts as part of the examination of generic and biosimilar drugs. In this notice, the MHLW stated that it was necessary for the MHLW to listen to the opinions of neutral experts since there is a limited number of legal precedents in regard to the scope of pharmaceutical patents.

Under the definition adopted in the system, "generic drug" means a pharmaceutical product which consists of the identical active ingredient in the identical dosage form and is applied via the identical route as the originator drug but may differ in terms of crystal form and hydrate/anhydrate; "biosimilar drug" means a pharmaceutical product which is equivalent to or identical in quality to the originator biological medicine produced by another company.

According to the operational guidelines that follow, the procedure starts with the MHLW’s designation of a particular follow-on product undergoing evaluation to be discussed by the Expert Committee. The generic or biosimilar manufacturer and the innovator receive notification, and either can, within 30 business days, provide documents which it agrees to furnish the committee, such as CTD application documents, the Patent Information Reporting Form, position papers of the companies, expert reports or appraisals, and advice from the JPO. Any of the parties can also identify potential committee members with whom there is a conflict of interest.

The MHLW selects three members, in principle (five if deemed necessary), from a published roster of qualified lawyers, patent attorneys, and academics, screened against independence criteria covering financial ties (including a three-year lookback on financial benefits exceeding ¥500,000 per year from either party), current paid advisory relationships, and family or firm-colleague connections to either company. The committee reviews public information and submitted materials, may request further documents through the MHLW, and issues a joint written opinion within roughly 30 business days, stating a conclusion and reasons. The opinion carries no legal binding force and is not an appealable administrative disposition. The MHLW retains final approval authority, using the opinion only as reference. Committee identities stay confidential, and opinions are disclosed to the parties, redacted, only after the final approval decision is public.

Strategic Implications and looking Forward

The 2025 amendment presents risks for the companies involved in the linkage process both in a practical sense. Originator companies are forced to pay attention to patent reporting in the most comprehensive and timely manner, because unreported substance and use patents won't be considered in the future. At the same time, there are many opportunities for originator companies to point out the problem of possible infringements to the MHLW during the approval process and, thus, to use the resources on engagement with the agency (and now Expert Committee) without serious risks under unfair competition law.

From the perspective of generic and biosimilar companies, formal inclusion in the framework of the linkage mechanism makes them face the same patent issues as small-molecule generics did before. It becomes harder to prove that the rules of the game don't work for biologics. Judicial trends in recent years show that even small differences in formulations or additives are not a sufficient ground to avoid possible infringement anymore.

The "Double Track Problem" exists within the Expert Committee itself, as it offers opinions which are both non-binding and not subject to appeal. This means that a positive administrative decision cannot protect the company against any future judicial decision that contradicts this decision. Until this contradiction between the administrative and judicial processes is solved, through legislative reform, companies should view the Committee’s opinion as only one of the pieces of information they must consider.

Conclusion

The notification issued by Japan in October and November 2025 is undoubtedly the biggest transformation of its patent linkage regime since 2009. First of all, the introduction of the notion of biosimilar medicines to the regulatory framework is noteworthy, as well as the participation of experts to counterbalance the lack of patent knowledge in the MHLW. However, the reform is still implemented using the administrative regime and not legislative, as before and despite the criticism of the rule of law, which remains an open contradiction between the administrative and the judicial determination of the patents. In any case, the takeaway for the companies wishing to enter or work in the Japanese market is to regard the reform as making the game more serious than solving the problem of ambiguity in the system.

Author :- Annika Tony, in case of any query, contact us at Global Patent Filing or write back us via email at support@globalpatentfiling.com.

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