Japanese chemical giant Toray announced on December 19, 2018 that it is striking out at two competitors that it claims are violating its extended medical use patent for an anti-itch product, Remitch®. The Japanese business paper Nikkei Shimbun took up this matter more recently, on January 21, 2019 with commentary.

Toray's patent No. JP 3531170, a medical use patent, was set to expire in 2017, but it applied for an extension of 5 years, which is possible under the Japan Patent Office (JPO) intellectual property system. Toray stated in its own press release that it filed the infringement case with the Tokyo District Court on December 13, 2019 in order to stop production and sale, and win damages for, allegedly infringing generic products made by Sawai Pharmaceutical Co., Ltd. and FUSO Pharmaceutical Industries, Ltd. (both based in Osaka).

T. Shibuya of Nikkei Shimbun comments that in Japan a medical patent, when extended, is limited in scope to the specific uses that have been approved by regulators. This is illustrated by when the IP High Court declared noninfringement of Swiss Debiopharm's medical formulation patent in 2017, because the defendant had used different additives from those claimed to prepare its generics.

Toray's extended use patent is fairly narrow regarding additives, so if the Tokyo District Court were to apply the precedent suggested by the Debiopharm preparation patent case to this and other use patent cases, Toray would probably lose. Then, it protests, generic producers could merely adjust additives in their drugs while mimicking the actual patented use of the drugs. Toray seems to be contending that the court should avoid crippling use patents with non-use technicalities. 

Depending on how it proceeds, this case should help to clarify the limits of use-related and other extended medical patents, and better chart the realm where drug developers and generic producers duel for market shares.


Japan Generic Medicines Association, "医薬品の特許について [Medication patents]," accessed January 31, 2019. 

Nikkei Shimbun, "用途特許延⻑保護どこまで東レ、かゆみ改善薬巡り侵害訴え後発薬とのすみ分け影響 [How far for use patent extension protection? Toray sues for alleged infringement of itch alleviation medication; impact on relation with generics]," ed. Takahiro SHIBUYA, January 21, 2019.

Toray, "経口そう痒症改善剤「レミッチ®」用途特許に関する 特許権侵害訴訟提起について [Concerning oral antipruritus drug "Remitch® use patent infringement litigation initiation]," press release, January 19, 2019 (accessed January 31, 2019). 

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