Intellectual Property

Injunctions based on pharmaceutical patents with extended terms: responses by companies facing claims and by patent holders

Whether a company has been asked to stop manufacturing and selling a product on the basis of a patent whose term has been extended, or has learned of another company's planned product launch during the extended term, the first task is the same. It involves identifying which term extension registration is based on which regulatory approval decision, and comparing the details of that approval with the product in question in light of the patented invention.

The scope of a patent right during its extended term is linked to the details of the approval decision underlying the extension. This requires a separate analysis from that of the technical scope defined by the claims. Neither "a registered term extension allows all generic products to be stopped until the expiration date" nor "differences in excipients or dosage form alone place the product outside the scope of the patent right" is a conclusion that can be drawn across the board.

This article is intended for both companies facing a demand to stop and patent holders considering enforcement. It first sets out the matters that both sides need to check, then explains their respective responses.

Reviewed by Keishi Yoshikawa, Attorney at Law and Patent Attorney (Dai-Ichi Tokyo Bar Association)

Last updated: September 27, 2026

Matters to check when an issue arises involving a patent with an extended term

The number of the asserted patent, the claims, and the type of invention (substance, formulation, medical use, or process)
Details of the term extension registration—the underlying approval decision, the length of the extension, and the expiration date
If the same patent has multiple term extension registrations, all of them and their respective periods, including those that have already expired
The ingredients, quantities, dosage and administration, and indications and effects of the approved pharmaceutical product
The same particulars for the product in question, and the differences between the two products
The acts the claim seeks to stop (manufacture, transfer, offers for transfer, or importation) and their timing

How we can helpCross-checking the patent register, approval documents, and prosecution history, and mapping the relationship between term extension registrations and approval decisions / Separating the analysis of technical scope from the analysis of the scope of the patent right during the extended term / Identifying what needs to be checked about product differences and what tests and documents are needed / Considering grounds for invalidating patents and term extension registrations / Preparing response letters for companies facing claims and warning letters for patent holders / Considering terms for negotiations and settlement

Contact Form

Contents

1 Checking the demand for an injunction, the proceedings, and the planned acts
2 Identifying the term extension registrations and approval decisions underlying the claim
3 Distinguishing technical scope from the scope of the patent right during the extended term
4 Matters to check and evidence concerning product differences
5 Responses by companies facing claims
6 Responses by patent holders
How we can assist
Key legislation and official sources
Frequently asked questions

1 Checking the demand for an injunction, the proceedings, and the planned acts

The documents received and the planned acts

For a company facing a demand to stop, the first step is to distinguish whether the document received is a warning letter, an application for a provisional disposition (interim injunction), or an order that the court has already issued. Responses to the provisional disposition proceedings themselves are addressed in a separate article (Responding to a provisional disposition (interim injunction) to stop pharmaceutical sales immediately before launch).

On the patent holder's side, the opposing party's product and planned acts are identified. The acts to be covered by the claim differ depending on whether the product is at the stage of obtaining approval, listing on the National Health Insurance (NHI) drug price list, manufacture, shipment, or sale.

Organizing the deadlines

The response deadline, court dates, planned launch date, and NHI drug price listing schedule are set out together to identify what needs to be decided and in what order.

2 Identifying the term extension registrations and approval decisions underlying the claim

Cross-checking the patent register and approval documents

The details of the term extension registration are checked against the patent register. The details of the approval decision underlying the extension—ingredients, quantities, dosage and administration, and indications and effects—are then checked against the approval documents.

Looking only at the claims without carrying out this task leaves no basis for the subsequent comparison. Identifying the details of the approval decision is necessary before considering the scope of the patent right during its extended term.

Bringing five items together in one table

Organizing the information checked by matching the following five items makes omissions easier to identify.

Item	What to check	Where to check
Claims	The wording of the asserted claims and the type of invention (substance, formulation, medical use, or process)	Patent gazette publication and prosecution history
Term extension registrations	The number of term extension registrations, the length of each extension, and each expiration date	Patent register
Underlying approvals	The ingredients, quantities, dosage and administration, and indications and effects specified in the approval decision underlying each term extension registration	Approval documents
Product in question	The same particulars as those specified in the approval decision (ingredients, quantities, dosage and administration, and indications and effects), and the date approval was obtained	Approval documents and product labeling
Differences	Which particulars differ between the product in question and the product covered by each approval decision, and how they differ	The comparison above

Where there are multiple term extension registrations, a separate entry is needed under "Term extension registrations," "Underlying approvals," and "Differences" for each registration. Whether the patent right may extend to the product under each registration is then considered separately. A conclusion cannot be drawn by selecting only one registration.

Checks where there are multiple term extension registrations

The same patent may have multiple term extension registrations based on different approval decisions. In that situation, all the underlying approvals, extension periods, and expiration dates are set out together. The details of the underlying approvals are also checked for extensions whose periods have already expired.

Selecting only the latest expiration date does not provide a basis for a blanket conclusion about whether the product may be sold. Which approval-based extension may have effect against which product needs to be considered separately.

3 Distinguishing technical scope from the scope of the patent right during the extended term

How the two analyses relate

The first question is whether the product in question falls within the technical scope of the patented invention as defined by the claims. The second is whether the patent right during its extended term extends to that product. These are separate analyses. Falling within the technical scope is a prerequisite for considering the effect of the patent right during the extended term, but does not by itself establish that the patent right extends to the product.

The Patent Act provides that, where the patent term has been extended, the patent right does not extend to acts other than the working of the patented invention for the product covered by the approval decision underlying the term extension registration (where that decision specifies a particular use for the product, the product used for that use). Interpreting this provision raises the question of how far differences between the product covered by the approval decision and the product in question may go while remaining within the scope of the patent right.

Following the sequence of analysis

The analysis follows a set sequence, as outlined below.

First, consider whether the product in question falls within the technical scope defined by the claims. This includes both literal coverage and coverage under the doctrine of equivalents. If the conclusion at this stage is that the product falls outside the technical scope, there is no need to consider the scope of the patent right during the extended term.

Second, if the product falls within the technical scope, consider whether the patent right during its extended term extends to the particular act involving that product. This is where the differences between the product covered by the approval decision and the product in question are examined.

For example, suppose the asserted patent concerns a product invention directed to the active ingredient itself, and the product in question contains that active ingredient. In this situation, the first analysis can often be completed relatively briefly, while the second raises questions about differences in excipients or dosage form between the pharmaceutical product covered by the approval decision and the product in question. Conversely, where a claim specifies the composition of a formulation in detail, whether the claim elements are satisfied becomes an issue at the first stage.

Third, separately from these questions, consider whether there are grounds for invalidating the term extension registration itself. Technical scope, the scope of the patent right during the extended term, and the validity of the term extension registration each require a separate determination.

The documents to be collected differ depending on which of these issues forms the focus of the case. Combining the three analyses obscures which documents are needed.

Points to note when citing judgments

The Intellectual Property High Court has issued a Grand Panel judgment on the scope of patent rights during an extended term, and several subsequent judgments have also been issued. The following points require attention when applying these judgments to a company's own product.

For product inventions concerning pharmaceutical ingredients, the Grand Panel judgment identifies four categories in which products are found to be substantially identical, subject to a limitation on the circumstances covered. That limitation is that there are one or more differences concerning the "ingredients," quantitative differences in the "quantities," or quantitative differences in the "dosage and administration" specified in the approval decision, and no other differences.

The four categories can be outlined as follows. First, for a patented invention characterized solely by its active ingredient, non-active ingredients are added, substituted, or otherwise modified on the basis of well-known or commonly used technology at the time of the approval application. Second, for a patented invention concerning the stability, dosage form, or similar aspects of a pharmaceutical product with a publicly known active ingredient, ingredients are likewise added, substituted, or otherwise modified on the basis of well-known or commonly used technology, and the products are found to be identical in their technical features, functions, and effects. Third, the differences in quantities or dosage and administration are quantitatively insignificant. Fourth, although the quantities differ, the products are found to be identical when those quantities are considered together with dosage and administration.

The second category requires a finding of identity in technical features, functions, and effects, and is therefore treated differently from the other three.

Cases outside these limited circumstances are not all resolved under this framework. The judgment states that, where a difference in dosage form results in differences in dosage and administration that are not merely quantitative, consideration from multiple perspectives is necessary, and that, where indications and effects differ because the diseases targeted differ, consideration from a medical perspective, including the similarity of the diseases, is important. The judgment cannot be read as meaning that the patent right does not extend to a product simply because it falls outside the four categories.

The judgment also rejects the application, directly or by analogy, of the doctrine of equivalents to the determination of substantial identity. It is therefore inappropriate to explain that substantial identity is determined using the five requirements of the doctrine of equivalents. Conversely, it is also incorrect to say that infringement under the doctrine of equivalents cannot occur during the extended term. The judgment requires the product in question to fall within the technical scope, including equivalents, as a prerequisite for considering the scope of the patent right during the extended term. The analysis of technical scope and the analysis of the scope of the patent right should not be confused.

4 Matters to check and evidence concerning product differences

The technical significance of the differences

Where there are differences between the product in question and the pharmaceutical product covered by the approval decision, their significance is considered in relation to the technical features, functions, and effects of the patented invention.

Where there are differences in the form of the active pharmaceutical ingredient (such as a hydrate or an anhydrate), the types of excipients, dosage form, or ingredient content, the documents needed depend on which differences are in dispute. Examples of documents to examine according to the issues include stability or dissolution test results, documents explaining why particular excipients were selected, and literature supporting whether the technology can be described as well-known or commonly used. Not all of these are necessary in every case.

An argument is sometimes made that the differences do not matter simply because the product has been approved as a generic pharmaceutical product. However, there is a court judgment that did not accept the argument that all products approved as generics are substantially identical.

The limits of relying on independent development

Independent development of the product in question and the filing of a separate patent application are important facts in their own right, but do not alone establish that the product falls outside the scope of the patent right. Documents are needed to explain how the differences relate to the technical features of the invention, taking account of whether it is a substance invention, a medical use invention, or a formulation invention.

Distinguishing what can and cannot be confirmed

At this stage, matters that cannot be established from publicly available information alone usually remain. What has been confirmed and what has not are recorded separately, and the additional tests or investigations needed are identified.

The information missing differs depending on which side the company is on.

A company facing a claim knows the details of its own product, but may need to investigate the prosecution history of the opposing party's patent and the details of the approval decision underlying the term extension registration. It also needs to retrieve documents from its own development records explaining why particular excipients were selected and whether the technology can be described as well-known or commonly used.

A patent holder knows the details of its own patent and term extension registrations, but publicly available information provides only limited insight into the composition, manufacturing process, and development history of the opposing party's product. At an early stage, the patent holder determines what can be established through public information and product analysis, and which matters need to be left to procedures for obtaining evidence in litigation.

5 Responses by companies facing claims

The arguments that the product falls outside the technical scope, that the patent right during its extended term does not extend to the product, and that there are grounds for invalidating the patent or the term extension registration are considered separately.

The Patent Act provides that, in infringement litigation, if the court finds that the patent should be invalidated in patent invalidation proceedings before the Japan Patent Office (JPO), or that the term extension registration should be invalidated in proceedings before the JPO to invalidate that registration, the patent holder is not entitled to enforce the right against the opposing party. Grounds for invalidating the term extension registration itself are also covered by this provision. This means there is scope to argue within infringement litigation that the requirements for registering the term extension may not have been met.

Matters to check for grounds to invalidate the term extension registration

The Patent Act lists grounds for invalidating term extension registrations based on pharmaceutical approvals and similar regulatory decisions. The following three checks are central to the sequence of review.

Matter to check	Documents to examine
Whether obtaining the underlying approval or other regulatory decision was necessary to work the patented invention	The claims, the underlying approval, and relevant earlier approvals
Whether the extension exceeds the period during which the patented invention could not be worked	The start and end of testing, the dates of the approval application and approval, and the documents underlying the calculation of the period
Whether there are problems with the relationships among the approval holder, the applicant, and joint owners	The relationship between the approval holder and the patent holder, whether a license exists, and who held the rights at the time of the application

Two points require attention. First, even where the extension is too long, the entire extension is not automatically invalid. Invalidation may be limited to the excess period. Second, a court's acceptance of a defense restricting enforcement in infringement litigation is separate from invalidation of the term extension registration itself. The defense restricts enforcement against the opposing party; the judgment alone does not extinguish the registration.

The content and timing of the response letter are determined together with the manufacturing and sales plans. Whether to continue manufacturing and selling, change the timing, modify the specifications, or enter negotiations for a license is decided in light of the analyses above and the constraints of the business.

For procedural responses where an application for a provisional disposition has been filed against the company, see the separate article (Responding to a provisional disposition (interim injunction) to stop pharmaceutical sales immediately before launch).

6 Responses by patent holders

The patent holder identifies the acts and scope to be covered by the claim. Manufacture, transfer, offers for transfer, and importation are distinct acts, so the acts the opposing party is currently carrying out are distinguished from those it intends to carry out.

Information about the opposing party's product, the patent holder's own patent and term extension registrations, and the details of the approval decisions is organized as evidence supporting infringement or a risk of infringement. After identifying what information is missing, the patent holder decides whether to begin with a warning, negotiations, or legal proceedings.

Where there are multiple term extension registrations, it is necessary at this stage to decide which registration to rely on for enforcement. The registration with the latest expiration date does not necessarily have effect against the product in question. The details of the underlying approval decisions and the differences from the product in question are set out together to consider which registration provides an appropriate basis for the case.

The patent holder also anticipates the opposing party's possible responses. Identifying the documents available to address each argument—that the product falls outside the technical scope, that the differences go beyond substantial identity, or that there are grounds for invalidating the patent or term extension registration—makes it easier to assess the prospects for negotiations.

When sending notices to business counterparties alleging infringement, the recipients, content, and basis of the notices are considered carefully. The Unfair Competition Prevention Act defines communicating or circulating false statements of fact that harm a competitor's business reputation as unfair competition. Whether a notice falls within this category is assessed in light of whether a competitive relationship exists, whether the facts communicated are false, and whether they harm business reputation, taking account of the investigation and negotiations preceding the notice, its recipients, and its content and manner of communication.

How we can assist

We check the patent register, approval documents, and prosecution history against one another and map the relationship between each term extension registration and its underlying approval decision.
We consider technical scope and the scope of the patent right during the extended term in separate analyses.
We review product differences to identify what needs to be checked and what tests and documents are needed.
We consider the scope of investigation and how to structure arguments concerning grounds for invalidating the patent and term extension registrations.
We assist with preparing response letters for companies facing claims and warning letters for patent holders.
We consider terms for negotiations and settlement, including competition law issues.

Key legislation and official sources

English translations of legislation are provided for reference. The Japanese texts are authoritative.

Article topic	Legislation or official source	Source type and English version reviewed
Term extension registrations, underlying approvals, technical scope, and the scope of the patent right during the extended term	Patent Act— Japanese text on e-Gov	Legislation. English translation (earlier version). The translation's version labels differ (Act No. 48 of 2022 in the Japanese label; Act No. 48 of 2024 in the English label).
Substantial identity, the four categories and their limitations, and the distinction from the doctrine of equivalents	Intellectual Property High Court, Grand Panel judgment of January 20, 2017, 2016 (Ne) No. 10046	Court judgment.
Grounds for invalidating term extension registrations, treatment of an excessive extension period, and invalidity defenses in infringement litigation	Patent Act— Japanese text on e-Gov	Legislation. English translation (earlier version). Version labels as noted above.
Notices alleging infringement and false statements harming a competitor's business reputation	Unfair Competition Prevention Act— Japanese text on e-Gov	Legislation. English translation (earlier version). The translation identifies its last version as Act No. 51 of 2023.

Legal information reviewed: September 27, 2026

Frequently asked questions

Q1 Can a patent with a registered term extension be used to stop all generic products until its expiration date?

No. The patent right during its extended term does not extend to acts other than the working of the patented invention for the product covered by the approval decision underlying the term extension registration. The significance of differences from the product in question needs to be considered in light of the invention.

Q2 If the ingredients are the same, does the patent right necessarily extend to the product?

Having the same active ingredient is an important fact, but does not determine the conclusion by itself. Conversely, differences in excipients or dosage form alone do not establish that the patent right does not extend to the product. A difference in the active ingredient does not have the same significance as a difference in excipients or dosage form. It is therefore necessary to identify where the differences lie and consider their significance in relation to the invention's technical features, functions, and effects.

Q3 There are multiple term extension registrations for the same patent. Which should be checked?

All of them need to be checked. The underlying approval decision, extension period, and expiration date are organized for each registration. The details of the underlying approval are also checked for extensions whose periods have already expired. Which extension may have effect against which product needs to be considered separately.

Q4 Is it enough to argue that the formulation was independently developed?

No. Independent development and the filing of a separate patent application are meaningful facts in their own right, but do not alone establish that the product falls outside the scope of the patent right. Documents explaining how the differences relate to the invention's technical features are needed.

Q5 Our company believes there is a problem with the term extension registration itself. Can this be raised in infringement litigation?

Yes. The Patent Act provides that, in infringement litigation, if the court finds that the patent should be invalidated in patent invalidation proceedings before the JPO, or that the term extension registration should be invalidated in proceedings before the JPO to invalidate that registration, the patent holder is not entitled to enforce the right against the opposing party. Arguments that the requirements for registering the term extension were not met are also covered by this provision.

However, which requirements to challenge and which documents to rely on are considered after reviewing the prosecution history of the term extension application, the approval documents, and the documents concerning the calculation of the extension period. Acceptance of this defense is also separate from invalidation of the term extension registration itself.

Q6 What should a patent holder do if it does not know the details of the opposing party's product?

The patent holder identifies what can be established from publicly available approval information, product labeling, and analysis of products that can be obtained. It then considers whether procedures for obtaining evidence in litigation can be used to obtain the missing information. Where the manufacturing process is at issue, how far that process can be identified and which means of obtaining evidence to consider at each stage need to be addressed separately.

Contact

Making an inquiry

You may consult us about injunctions involving patents with extended terms, whether you are facing a claim or considering enforcement. If you bring documents showing the patent number, details of the term extension registration, and the approved particulars of the product in question, we can begin a concrete assessment at the initial consultation.