Introduction

Patent term extension (PTE) is a key tool in pharmaceutical lifecycle management (LCM). It can extend patent protection up to five years to make up for time lost during regulatory review, and it often affects when generics or biosimilars can enter the market. On September 16, 2026, I spoke at the IP Forefront Pharma Forum (IFPF) 2026 in Shanghai on “Patent Term Extension (PTE) in Japan: From Basics to Recent Topics and Implications for Generic Entry.”

This post summarizes the presentation, focusing particularly on recent Japanese court decisions concerning the scope of extended patent rights. For simplicity, “generics” in this post also includes biosimilars.

 

The Two Pillars of Japan’s PTE System

Japan’s PTE system involves two separate questions. The first concerns the validity of PTEs, and the second concerns the scope of rights under PTE:

• Can a PTE be obtained? (Patent Act, Art. 67(4))
  An extension is available where the patented invention could not be worked because a regulatory disposition, such as a drug approval, had to be obtained first. This is often referred to as the “necessity test.”
• What does the extended right cover? (Patent Act, Art. 68-2)
  The extended patent right does not retain the full scope of the original patent claims. Its effect is limited to the working of the patented invention in respect of the product that is subject to the relevant approval and the particular use specified in that approval.

Other notable features of the Japanese PTE system include:

• Multiple extensions are possible: a single patent may receive several PTE registrations, while a single approval may support extensions of multiple patents.
• Eligible patents are not restricted by type: patents covering active pharmaceutical ingredients (API), formulations, medical uses, e.g., may all qualify, subject to the statutory requirements.
• The type of pharmaceutical approval is not itself a statutory limitation: an initial marketing approval or a subsequent approval, such as one for an additional indication or dosage regimen, may serve as the basis for a PTE, provided the applicable requirements are met.

Registration Requirements: The Necessity Test

Two landmark decisions concerning the necessity test are the Pacif® Capsule case (Supreme Court, April 28, 2011) and the Bevacizumab (Avastin®) case (IP High Court Grand Panel, May 30, 2014; Supreme Court, November 17, 2015). Both arose from challenges to JPO decisions on PTE registration. Without examining their details here, their principal significance can be summarized as follows:

• The Pacif® Capsule case established that even if there exists an earlier approval for the same API and indication, this does not automatically block a PTE registration based on a later approval for a product having the same API and indication, especially where the earlier product does not fall within the technical scope of the patented invention. Before this decision, generally, the JPO would have rejected such a PTE application.
• The Bevacizumab case clarified the necessity test by considering whether Approval 2, as the ground of the PTE application at issue, was necessary to work the patent depends on whether the manufacturing and selling of the product under the earlier Approval 1 encompass the manufacturing and selling of the product under Approval 2. The patent concerned an anti-VEGF antibody, and an earlier approval for the product had already supported PTE 1. The later approval added a dosage regimen enabling combination therapy. The court concluded that the earlier approval did not encompass the later approval and permitted registration of PTE 2.

Scope of Extended Rights: The Framework and Recent Cases

The scope of extended patent rights is currently a particularly closely watched issue in Japan, as illustrated by the litigation discussed below.

(1) The framework: Oxaliplatin Case (IP High Court Grand Panel, January 20, 2017)

Although Article 68-2 ties the effect of an extended patent right to the product and use specified in the underlying approval, the Oxaliplatin Grand Panel decision articulated the principle that the extended right may also cover products “substantially identical” to the approved product. This may apply where differences are only minor or merely formal.
The Oxaliplatin court further gave four typical (non-exhaustive) examples of such differences:

• For API patents, adding or substituting well-known or conventional excipients.
• For patents on the stability or dosage form of a known API, changing a non-active ingredient using well-known or conventional techniques, without changing the technical features or therapeutic effects.
• Insignificant differences in quantity, dosage or administration.
• Differences in quantity that do not matter once dosage and administration are taken into account.

The court also recognized an estoppel-type limitation for products intentionally excluded during the PTE registration process.

(2) Dasatinib (Sprycel®) (Tokyo District Court, May 15, 2025)

The Dasatinib case illustrates how the Oxaliplatin framework may apply to a generic product that differs from the approved originator product.

The relevant facts can be summarized as follows:

• The patent at issue was a substance patent covering dasatinib.
• Marketing approval for the originator product, Sprycel®, existed, whose API is dasatinib hydrate.
• The PTE was registered based on that approval.
• The generic product contains anhydrous dasatinib with different excipients, and was approved as bioequivalent.

The issue here was whether the extended patent right covered the generic.

Applying the Oxaliplatin framework, the Tokyo District Court found that the generic product was not substantially identical to the approved originator product. In particular, it had not been shown that the generic’s excipient changes were based on well-known or conventional techniques.

The decision illustrates that regulatory bioequivalence does not necessarily establish “substantial identity” for purposes of the extended patent right.

(3) Lubiprostone (Amitiza®) Case (Osaka District Court, March 3, 2026; now pending before the IP High Court)

The Lubiprostone litigation raises a different and potentially more far-reaching issue concerning multiple PTEs.

The relevant facts can be summarized as follows:

• The patents at issue concern the API.
• Approval 1 was for Amitiza® 24 μg capsules, supporting PTE 1.
• Approval 2 was for Amitiza® 12 μg capsules, supporting PTE 2.
• After PTE 1 expired, PTE 2 remained in force, and a generic 24 μg product containing the same API entered the market.

The central question was whether PTE 2, based on the later 12 μg approval, could nevertheless cover the 24 μg generic after PTE 1 had expired.

In its March 3, 2026 judgment, the Osaka District Court rejected the infringement claim.
The court applied the substantial-identity framework in principle and recognized that the scope of rights arising from different PTE registrations may overlap under the framework. Nevertheless, considering the PTE system as a whole and the relationship between the relevant approvals and extensions, it concluded that the extension based on the later 12 μg approval could not extend to the product covered by the earlier 24 μg approval. In substance, the court declined to allow the later PTE 2 to restore protection for the product associated with the earlier PTE 1 after that extension had expired.

The judgment is under appeal before the IP High Court (Case No. 2026 (Ne) 10041).

Why the Pending IP High Court Decision Matters

On June 29, 2026, the IP High Court initiated a procedure to solicit third-party opinions. The submission period closed on September 30, 2026.

Among the questions raised, the key PTE-related issues include:

• How should the scope of an extended patent right be interpreted in relation to the requirements for PTE registration?
• Can PTE 2, based on approval of a 12 μg product, cover a 24 μg generic, including one with different excipients?
• Does the answer change if PTE 1, based on the earlier 24 μg approval, has expired?
• Would the answer differ if no PTE 1 had been obtained for the 24 μg product?

These questions concern the relationship between two fundamental aspects of Japan’s PTE system: the approval-based requirements for obtaining an extension and the substantial-identity doctrine governing the scope of the extended right.

The outcome may have significant implications for pharmaceutical patent strategies involving multiple approvals and PTE registrations, as well as for generic manufacturers assessing potential market-entry dates.

Implications for Generic Entry

PTE can affect the timing of generic entry, but it is not the only relevant factor. A practical assessment must also consider the re-examination period, which functions as a form of de facto data exclusivity, and the patent-linkage practice of the Ministry of Health, Labour and Welfare (MHLW).
For background and recent developments in these areas, see our earlier publications:

• When Does a Generic Entry Become Possible? - patent protections and pharmaceutical regulations in Japan (TMI NEWSLETTER Issue 17)
• Updates to: When Does a Generic Entry Become Possible? (TMI Blog, June 2026)

Looking Ahead

Japanese courts have established that extended patent rights may reach beyond products literally identical to those approved. However, the precise boundaries of substantial identity, particularly where multiple PTEs are involved, remain unsettled. The pending Lubiprostone appeal offers an important opportunity for the IP High Court to clarify how these principles interact.
We will continue to monitor the proceedings and report on significant developments.

October 2026 | Sayaka Ueno