September 11, 2025

Patent News

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. The IP High Court overturned the Tokyo District Court's ruling that there had been no patent infringement 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”. Torii Pharmaceutical Co., Ltd. (“Torii”), which obtained a license from the Plaintiff, was selling “REMITCH® OD Tablets 2.5 μg”.
The filing date of the Patent is November 21, 1997, and the title of the invention is "anti-pruritic agent". 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, and began manufacturing and sales after the Defendant Drugs were included in the National Health Insurance drug listing on June 15, 2018.
On December 13, 2018, the Plaintiff filed a patent infringement lawsuit against the Defendants at the Tokyo District Court. On March 30, 2021, the Tokyo District Court dismissed the Plaintiff's claims, ruling that the Defendant Drugs did not fall within the scope of the Patent and that no equivalent infringement was recognised.

The chorological order is summarized below.
November 21, 1997: The Patent application was filed
(20 years have passed from the application date)
June 15, 2018: The Defendants started manufacturing and selling the Defendant Drugs
December 13, 2018: The Plaintiff filed an infringement lawsuit against the Defendants in the Tokyo District Court.
March 30, 2021: The Tokyo District Court dismissed the Plaintiff's claims, and the Plaintiff appealed.
November 21, 2022: The PTE registration period expired.
May 27, 2025: The IP High Court ordered the Defendants to pay damages.

Patent and Defendant Drugs
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.
A. Antipruritic drug comprising,
B. the active ingredient which is an opioid κ receptor agonist compound (“Compound”) represented by the general formula (I).

The Defendant Drugs are as follows:
a. Antipruritic drug containing,
b. nalfurafine hydrochloride

Nalfurafine (free form) falls under the Compound (Element B).

Both the Plaintiff Drug and the Defendant Drugs contain nalfurafine hydrochloride in the tablet. When 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”) that forms the basis of a formulation when additives are added. In the Patented Invention, the active ingredient is “nalfurafine (free base)”, whereas the “active ingredient” in the Defendant Drugs is the acid salt of nalfurafine (free base), namely “nalfurafine hydrochloride”. Therefore, the District Court concluded that the Defendant Drugs do not satisfy Element B. Furthermore, the Tokyo District Court ruled that since the Plaintiff intentionally excluded a configuration in which “pharmacologically acceptable acid addition salt” is used as the active ingredient from the scope of the Patented Invention, no equivalent infringement is recognised. The Tokyo District Court dismissed the Plaintiff’s claims.


IP High Court Decision
The IP High Court ruled on the following issues and found that the Defendants had infringed the Patent, ordering the Defendants to pay the Plaintiff a total of 21.7 billion yen in damages.
Issue 1: The Defendant Drugs fall within the scope of the Patented Invention.
Issue 2: The PTE registration extends to the manufacture and sale of the Defendant Drugs.
Issue 3: The PTE registration should not be invalidated.
Issue 4: The duration of the PTE registrations is not excessive.
Issue 5: The Defendants' prior use rights are not recognised.
Issue 6: As the exclusive ordinary licensee of the Patent, Torii has an independent right to claim damages. The Plaintiff, who was assigned the right to claim damages from Torii Pharmaceutical, may claim compensation equivalent to lost profits under Article 102(1) of the Patent Act.
Issue 7: With respect to the Defendant Drugs manufactured during the term of the patent but not yet sold, damages equivalent to the royalty amount are recognised.

The reasons for Issues 1, 2, and 4 are as follows.

(1) Issue 1 (Literal Infringement)
The IP High Court established the following facts and concluded that, based on the scope of the Patented Invention, the description in the Patent specification, the history of the Patent application, and common technical knowledge, the Patented Invention refers to an anti-pruritic agent that exhibits pharmacological effects as an “active ingredient” based on its opioid κ receptor agonist activity, regardless of whether it is in the form of an acid addition salt, provided that the compound represented by General Formula (I) (nalfurafine) dissolves and is absorbed in the body.

1. The objective of the Patented Invention is to provide an opioid κ receptor agonist with extremely rapid and strong anti-pruritic activity and an anti-pruritic agent containing the same.
2. In the field of pharmaceutical formulations, the term “active ingredient” refers to a substance that dissolves and exerts its effect in the body (blood), and at the time of the Patent application, it was recognised as common technical knowledge that acid addition salts were used to improve the solubility and stability of drugs.
3. A person skilled in the art, upon reviewing the Patent specification, would have easily understood that the chemical substance capable of exerting the anti-pruritic effect, which is the objective of the Patented Invention, is “an opioid κ receptor agonist compound”, and that the form of a “pharmacologically acceptable acid addition salt” is merely a form intended to improve the solubility or stability of the drug, not to alter the anti-pruritic effect itself.
4. Even when considering the filing history, it cannot be said that an anti-pruritic agent containing a pharmacologically acceptable acid addition salt as an active ingredient was intentionally excluded from Patented Invention.

The IP High Court ruled that the Defendant Drugs are drugs containing nalfurafine, which exhibits analgesic effects based on its property of acting as an opioid κ receptor agonist by dissolving and being absorbed in the body, in the form of its acid addition salt, nalfurafine hydrochloride. The IP High Court therefore determined that the Defendant Drugs satisfy the requirements of the Patented Invention and fall within its scope.

(2) Issue 2 (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 the marketing approval that served as the basis for the PTE registration but also to drugs that are deemed to be “substantially identical” in terms of “ingredients, quantity, administration, dosage, and indication”.
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 it is found that the Defendant Drugs only add or incorporate different ingredients in part with regard to ingredients that are not active ingredients, based on the well-known or commonly used art, or 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 Defendant Drugs have been modified through initial approval, addition of indications, and formulation changes, resulting in different additives being used. For example, the additives in the formulation at the time of initial approval were entirely different from those in the Plaintiff Drug.
The IP High Court noted the following regarding the differences in additives:

1. The Patented Invention relates to the use of an anti-pruritic agent, and does not specify any particular additives;
2. The Defendant Drugs have been confirmed to be bioequivalent to the Plaintiff Drug;
3. The Defendant Drugs and the Plaintiff Drug differ only in terms of additives;
4. There is a common technical knowledge that additives are generally added to formulations in amounts that do not exhibit pharmacological effects, are harmless, and do not interfere with the therapeutic effects of the active ingredients;
5. Even considering the description in the Patent specification and the development history of the Defendant Drugs, the additives in each formulation do not have any technical significance different from those described above; and,
6. (vi) Even if the Defendant Drugs use a group of additives independently developed by the Defendants and subject to patent applications, the fact that these additives do not have pharmacological effects and do not impair the therapeutic effects of nalfurafine remains unchanged.

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.

(3) Issue 4 (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, after conducting clinical trials for soft capsule tablets, trials to confirm the bioequivalence between soft capsule tablets and OD tablets (oral disintegrating tablets) were conducted, 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 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, not only bioequivalence data but also review reports and other documents related to the already approved capsule formulation were submitted, reviewed, and approved. The IP High Court found 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 considered the highest ever in a patent infringement lawsuit.
Regarding the effect of the PTE, the previous IP High Court Grand Bench Decision (Oxaliplatinum Case) set out the criteria for such determinations. However, the outcome of that decision was based on the grounds that the defendant products did not fall within the technical scope of the claims and the issue of the effect of the PTE was not truly relevant. Therefore, how the Courts will apply such a criteria in cases where the effect of the PTE registration was at issue was closely watched. In this case, the Patented Invention was for a pharmaceutical use, and the additives differed between the original 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 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.
The Defendants have announced that they have filed an appeal and a request for acceptance of the appeal against the IP High Court Decision. It is anticipated whether the Supreme Court will take up this case and, if so, what judgment it will render.

Written by: Ms. Kiyoko Nakaoka (Attorney at Law, Patent Attorney)