What this article covers

In March 2021, I authored “When does a generic entry become possible? – patent protections and pharmaceutical regulations in Japan-“ (the “Previous Article”). This article provides an update on recent developments since publication of the Previous Article.

In the Previous Article, I explained that generic entry in Japan is primarily constrained by two key mechanisms: (i) the patent system and (ii) the re-examination period system. I also outlined Japan’s patent linkage system, which operates in practice to connect patent rights with regulatory approval and drug pricing/listing procedures.

While the overall framework remains unchanged, some important developments have taken place. Two particularly noteworthy developments are:

• Changes to the re-examination period system, including the possibility of extending exclusivity to up to 12 years through pediatric development; and
• Recent revisions to Japan’s patent linkage system, including the introduction of a trial expert panel system in patent linkage reviews.

 

Quick Recap

By way of background:
(A)    In Japan, market exclusivity for originator drugs is generally ensured by the combination of patent protection and the re-examination period. In principle, generic entry becomes possible only after both have expired.

(B)    A key feature of Japan’s patent term extension (PTE) system is that an extended patent right does not uniformly cover the entire claim scope; rather, its effect is limited to the scope corresponding to the approved product. In addition, it is possible for a single patent to have multiple PTE registrations, and for a single marketing approval to support PTE registrations for multiple patents, making the analysis complex in practice.

(C)    Japan’s patent linkage system is not established by statute but is implemented through administrative practice based on MHLW [*] notifications (see Section 4 below). It consists of two stages:

a.    Consideration of patents at the approval stage
If a patent covering the active ingredient of an originator drug is in force, approval for a generic drug will not be granted. Where patents cover only certain indications, dosages, or administration methods, approval may be granted limited to portions outside the patent scope.

b.    Adjustments at the drug price listing stage
When applying for reimbursement listing, generic companies must conduct prior consultation with patent holders where patent disputes may arise, confirming both the absence of patent concerns and the ability to ensure stable post-launch supply.

  “MHLW” = the Ministry of Health, Labour and Welfare

Updates on Re-Examination Period

(A)    Potential Extension of Re-examination Periods up to 12 Years Through Pediatric Development (effective May 1, 2026) 

The re-examination period system is implemented under the MHLW notice “Handling of Re-examination Periods.” A revision dated February 27, 2026 clarified that, in cases involving pediatric dosage development, the period may be extended beyond previous practice to a maximum of 12 years.

Previously, extensions could be granted in practice based on considerations for pediatric clinical trial plans, but the requirements were not clearly articulated in the notice. The revised notice now explicitly provides that:

“For pharmaceuticals for which it is clearly recognized that development for pediatric dosage and administration is necessary, if a development plan for such pediatric use is submitted by the completion of the review for adult approval, and development is conducted without delay in accordance with such plan, the investigation period may be extended by two years, up to a maximum of 12 years.”

This clarification confirms that re-examination periods may reach up to 12 years (e.g., 8 years + 2 years of extension for New API Drugs, or 10 years + 2 years of extension for new Orphan Drugs), and (ii) the requirements for such extension are explicitly stated.
It is necessary that a concrete pediatric development plan be submitted by the completion of the adult approval review, and that clinical development be initiated and carried out without delay in accordance with that plan.

The 2025 amendment to the PMD Act [*] introduced an obligation to make efforts to formulate pediatric development plans at the time of adult drug development (effective May 1, 2026). Together with that, this revision to the MHLW notice reflects an increasing policy emphasis on promoting pediatric drug development, where drug lag/loss has been a serious issue.

From an originator company perspective, this revision would create a clearer pathway to extending regulatory exclusivity through pediatric development planning in Japan.

*   “PMD Act” ＝ The Act on Securing Quality, Efficacy and Safety of Products Including Pharmaceuticals and Medical Devices

(B)    Re-examination periods under the latest MHLW Notification

The February 27, 2026 revision did not fundamentally change the overall structure of Japan’s re-examination period system. The most notable update is the clarification that, where specified requirements relating to pediatric development are satisfied, the re-examination period may be extended by an additional two years, resulting in a maximum period of 12 years.
For reference, a summary of the re-examination periods currently provided under the MHLW Notice “Handling of Re-examination Periods” (as revised on February 27, 2026) is included at the end of this article.

Revision of MHLW Notification Forming the Basis of Patent Linkage (October 8, 2025)

Unlike the U.S. Hatch-Waxman framework, Japan's patent linkage system is not established by statute and does not involve an Orange Book-type mechanism. The Japanese patent linkage system is operated in accordance with an MHLW notification [*], which was amended on October 8, 2025, including the following updates. 

*    Current title: “Handling of Pharmaceutical Patents in Relation to Approval Reviews and Drug Price Listing under the Pharmaceutical and Medical Devices Act Concerning Generic Drugs and Biosimilars for Medical Use”

(A)    Clarification of Biosimilars

Biosimilars, which had previously been treated similarly to generics in practice without explicit mention, are now clearly included within the scope of the notification.

(B)    Clarification on Patent Information Reporting System

The revision clarifies that patents relating to originator active ingredients (i.e. substance or use patents) that are not reported via the patent information reporting form will, in principle, not be considered during generic approval review.
If such patents are granted after expiry of the re-examination period, the originator company or patent holder must submit the relevant report within 30 days of publication if it wishes the patent to be considered in the review process.

 

Trial Introduction of the Expert Panel System (From November 2025)

Pursuant to the MHLW notification dated November 14, 2025, titled “Trial Introduction of an Expert Panel System for Confirming the Existence of Patent Infringement in the Approval Review of Generic Drugs and Biosimilars,” the MHLW has initiated, on a trial basis, a system under which it may, as necessary, seek opinions from patent experts.

While determinations of patent infringement fall within the jurisdiction of the courts, and the determination of patent validity lies with the Japan Patent Office (JPO), meaning that MHLW itself does not possess authority to make substantive legal judgments in this regard, in practice, under the patent linkage system, MHLW’s decisions on whether to grant approval can affect the practical exclusivity of patents covering originator drugs vis-à-vis generics. In light of this situation, the system has been introduced with the aim of improving the quality of MHLW’s assessments at the approval review stage, as well as enhancing the transparency and predictability of the overall process.

Here is a summary of how this new system works:

• Designation of cases by MHLW:
  MHLW retains discretion to determine in which specific cases expert opinions should be sought during the review process. Where such designation is made, both the originator manufacturer and the generic manufacturer will be notified.
• Submission of materials:
  Upon receiving notification, the originator and generic (or biosimilar) manufacturers may each submit, within 30 business days, any of the following materials to which they consent to be shared with the expert panel:

o    Approval application materials (e.g., CTD 1.4)
o    Drug patent information report forms
o    Documents summarizing the originator manufacturer’s (or patent holder’s) views on the existence of patent infringement
o    Expert opinions, case law, academic literature, and other reference materials concerning patent infringement
o    Results of JPO’s Hantei (advisory opinion system)

• Selection of experts and consultation process:
  Following conflict clearance and a selection process for panel members, MHLW will formally request the expert panel’s opinion on the existence of potential patent infringement.
• Preparation of expert opinion:
  The expert panel (in principle consisting of three members) will deliberate and prepare a written opinion, generally within approximately 30 business days after receiving (i) publicly available information concerning the relevant generic and originator drugs (such as patent publications and package inserts), and (ii) the shared materials described above.
  The panel may also request additional information during this process. Once the consultation procedure is completed, MHLW will notify both the originator and generic manufacturers of its completion.
• Disclosure of expert opinion:
  After the final decision regarding the approval of the generic product has been made public, a copy of the expert opinion will, upon request, be promptly disclosed to the interested generic and originator companies, with certain information redacted, such as the names and affiliations of the experts, personal information, and portions constituting confidential business information.

As the framework remains at a trial stage, important questions remain regarding its practical operation, including the scope of issues that may be considered by the expert panel and the extent to which the system will affect the overall operation of Japan's patent linkage framework.

Closing remark

The intersection of pharmaceutical regulation and patent law in Japan remains an evolving and highly significant field. We will continue to follow developments and updates in this area. These developments may affect both exclusivity planning for originator companies and launch strategies for generic and biosimilar manufacturers. Companies with products approaching approval, patent expiry, or lifecycle management milestones should continue to monitor these changes closely.

Appendix: Summary of Current Re-examination Periods (MHLW Notice “Handling of Re-examination Periods,” as revised on February 27, 2026)

	Category of New Drugs	Re-examination Period
(1)	Orphan drugs  (i) Initial approval for a new indication, or addition of a clearly different dosage defined by a specified patient population (e.g., pediatric use) (ii) Initial approval for the addition, for the same indication, of a clearly different route of administration or a clearly different dosage (e.g., pediatric dosage) (iii) Cases other than (i) and (ii)	(i) 10 years  (ii) More than 6 years but not exceeding 8 years  (iii) More than 6 years but not exceeding 8 years
(2)	New drugs for which it is clearly recognized as necessary to conduct post-marketing studies using pharmacoepidemiological methods to evaluate comprehensive therapeutic effects on patients, such as survival prolongation, improvement in quality of life (QOL), and prevention of complications, particularly with long-term use.	10 years
(3)	New drugs with active ingredients that are clearly different from those of already approved drugs (excluding (1) and (2))	8 years
(4)	New drugs that differ from already approved drugs only in indication (i) Pioneering Drugs (ii) Cases where such existing drugs have only indications designated as orphan drug indications (excluding (i)) (iii) Cases other than (i) and (ii)	(i) A period of more than 6 years and up to 8 years, as designated by the Minister of Health, Labour and Welfare (ii) 5 years and 10 months (iii) 4 years
(5)	New drugs that differ from already approved drugs only in dosage and administration (excluding route of administration) or dosage amount, where the active ingredient and route of administration are the same, or where the differences from previously approved drugs are otherwise considered minor (excluding (1) ~ (4))	4years
(6)	New drugs not falling under categories (1) through (5)	6 years

Extension	For already approved drugs, where, after approval, it comes to be recognized that it is necessary to conduct evaluations using pharmacoepidemiological methods, based on endpoints such as survival prolongation, improvement in quality of life (QOL), and prevention of complications associated with long-term use, reflecting overall therapeutic benefit to patients	Up to a maximum of 10 years
	Where development has been conducted in accordance with a development plan for pediatric dosage and administration. (see 3(A) of this blog article)	Extension of +2 years  (up to a maximum of 12 years)