The IP High Court overturned the ruling of the district court that denied patent infringement by the generic version of REMITCH® OD tablets and ordered the generic manufacturers to pay 21.7 billion yen in damages

Toray Industries, Inc. (“Plaintiff”), the owner of Japanese Patent No. 3531170 (“Patent”), sued Sawai Pharmaceutical Co., Ltd. and Fuso Pharmaceutical Industries Ltd. (collectively, “Defendants”), for damages. The Plaintiff claimed that the Defendants’ manufacture and sale of generic version drugs (“Defendant Drugs”) of the “REMITCH^® OD Tablets 2.5 μg” (“Plaintiff Drug”) infringed the extended Patent. Although the Tokyo District Court judged that there had been no patent infringement, the IP High Court overturned the Tokyo District Court’s ruling  and ordered the Defendants to pay damages of 21.7 billion yen (IP High Court decision on May 27, 2025 (Case No. 2021(ne)10037)).

Summary of the case

The Plaintiff owns the Patent and obtained marketing approval in 2017 for an anti-pruritic agent sold under the trade name “REMITCH^® OD Tablets 2.5 μg”. Based on the marketing approval for the Plaintiff Drug, the Patent was granted patent term extension (“PTE”) registrations for a maximum of five years, extending its term until November 21, 2022.

The Defendants obtained marketing approval for their generic version of “REMITCH^® OD Tablets 2.5 μg” on February 15, 2018, 20 years after the filing date of the Patent (expiration of the original patent term), and began manufacturing and sales after the Defendant Drugs were included in the National Health Insurance drug listing on June 15, 2018.

Claim 1 (“Patented Invention”) of the Patent is divided into the following elements (general formula is omitted). The Patented Invention is a pharmaceutical use invention characterised by the use of the compound in element B for the purpose of an anti-pruritic agent.

1. Antipruritic drug comprising,
2. the active ingredient which is an opioid κ receptor agonist compound (“Compound”) represented by the general formula (I) (Note: the formula (I) shows the free form of nalfurafine only, and salts are not included.) .

The Defendant Drugs are as follows:

1. Antipruritic drug containing,
2. nalfurafine hydrochloride

In this regard, nalfurafine (free form) falls under the Compound (Element B).

The Plaintiff’s Drug (the originator’s drug) also contains nalfurafine hydrochloride, rather than nalfurafine (free form).

When nalfurafine hydrochloride  is administered to humans, nalfurafine (free form) is released from nalfurafine hydrochloride and absorbed by the living body to exert an antipruritic effect.

The Tokyo District Court ruled that the term “active ingredient” in Element B refers to the active pharmaceutical ingredient (“API”) and concluded that the Defendant Drugs do not satisfy Element B since the API in the Defendant Drugs is “nalfurafine hydrochloride” and is not “nalfurafine (free base)”.

IP High Court Decision

The IP High Court held that the Patented Invention is understood to refer to an antipruritic agent in which nalfurafine is dissolved and absorbed in vivo to exert its pharmacological action as the “active ingredient” and that the Defendant Drugs fall into the technical scope of the Patented Invention, and ordered the Defendants to pay the Plaintiff a total of 21.7 billion yen in damages. Although this judgment covers various issues, this article focuses on issues of the “Effect of PTE” and “Period of PTE” as follows.

• Effect of PTE

The IP High Court stated that, under Article 68-2 of the Patent Act, the effect of PTE registration extends not only to the identical drug that was the subject of a  marketing approval ( Each PTE is registered on the basis of a marketing authorization) but also to drugs that are deemed to be “substantially identical” in terms of “ingredients, quantity, administration, dosage, and indication” (with the drug of the marketing authorization).

The IP High Court found that the Patented Invention provides a new pharmaceutical use as an anti-pruritic agent based on the unknown attribute of “κ-receptor agonistic activity of compounds represented by general formula (I)”, which constitutes the technical feature of the Patented Invention, The Court also found that the Plaintiff Drug and the Defendant Drugs are identical in terms of their technical features and effects, as both are antipruritic agents containing nalfurafine as the active ingredient, and they have the same specific form as drugs. The Court went on to say that, in such cases, when the differences between the Plaintiff Drug and the Defendant Drugs in terms of “ingredients” other than the active ingredients do not affect their “indications” as a drug, and the differences are found to be merely slight differences or nominal differences as a whole, then the Defendant Drugs are found to be substantially identical to the Plaintiff Drug approved by the marketing approval regardless of the difference in ingredients.

The additives in the Defendants Drugs differed from those in the Plaintiff Drug. The IP High Court held that the differences in additives between the Plaintiff Drug and the Defendant Drugs are found to be merely slight differences or nominal differences as a whole, and that the Defendant Drugs are substantially identical to the Plaintiff Drug as a drug.

The IP High Court concluded that the effect of the PTE registration should be recognised as extending to the manufacture and sale of the Defendant Drugs.

• Period of PTE

The period of PTE registration must not exceed the period during which the patented invention could not be implemented in order to obtain the marketing approval. In this case, the patentee conducted clinical trials for soft capsule formulation and obtained a marketing approval for soft capsule formulation.  Subsequently, the patentee conducted  additional trials to confirm the bioequivalence between soft capsules and OD tablets (oral disintegrating tablets), and OD tablets were approved. The Defendants argued that the period during which the Patented Invention could not be implemented was 1 year and 11 months, which was the period from the clinical trials for the bioequivalence of OD tablets with soft capsules to the end of the review, and that the maximum extension period of 5 years was excessive.

The IP High Court stated that, in the marketing approval application for the OD tablets, the patentee submitted not only bioequivalence data but also review reports and other documents related to the already approved capsule formulation, and the authority reviewed such documents and issued the marketing approval. The IP High Court found that the JPO’s decision had no error in determining that the period during which the Patented Invention could not be implemented included the clinical trials of the soft capsule tablets, and rejected the Defendants’ claim that the extension period was excessive.

Comments

The amount of damages awarded in this case is the highest ever in a patent infringement lawsuit among the Japanese patent infringement judgments.

The previous IP High Court Grand Bench Decision (Oxaliplatinum Case) set out the criteria for the scope of the paten of PTE. In the Oxaliplatinum Case, however, the IP High Court judged that the defendant products did not fall within the technical scope of the claims, and thus  the issue of the scope of the extend patent was not relevant to the conclusion  . Therefore, the patent community has been interested in how the Courts will apply such a criteria in each specific case. In this case, the Patented Invention was for a pharmaceutical use, and the additives differed between the originator’s drugs and generic drugs. Nevertheless, the IP High Court ruled that, in light of the technical significance of the Patented Invention and the technical common knowledge regarding additives, the original drug and the generic drugs were substantially identical with each other as a drug. This ruling is consistent with the purpose of the PTE registration system, which aims to restore the period during which the patented invention could not be implemented.