1. Japan’s Patent Term Extension (PTE) System

In Japan, the term of patents relating to pharmaceuticals and similar products may be extended for up to five years to compensate for the period during which the patented invention could not be practiced due to the regulatory approval process. Patents eligible for PTE include compound patents, formulation patents, medical-use patents, manufacturing-process patents, and others. One distinctive feature of the Japanese system is that when multiple patents relate to an approved product, each patent may independently receive a patent term extension. The patentee is not required to select only one patent for extension. In addition, where multiple approvals are obtained for the same compound, such as a first approval as a pain medication followed by a second approval as an anticancer drug, each approval may independently serve as the basis for a separate PTE.

Partially because multiple patents may be extended on the basis of multiple approvals, disputes frequently arise regarding the scope of protection afforded by an extended patent. In this regard, in IP High Court Case No. Heisei 28 (Ne) 10046 (“Oxaliplatin case”), the court held that the effect of a patent during the extended term covers not only pharmaceuticals that are identical to the approved product specified by its ingredients, quantity, administration method, dosage, indications, and effects, but also pharmaceuticals that are substantially identical thereto.

 The IP High Court decision discussed below held whether or not a patent extended based on approval of an originator drug could be enforced against a generic product that differed in the type of excipients used.

 2. Overview of IP High Court Case Reiwa 3 (Ne) No. 10037

The Plaintiff-Appellant owned Patent No. 3531170 directed to an antipruritic agent containing as an active ingredient an opioid κ-receptor agonist compound represented by General Formula (I). The Plaintiff-Appellant obtained approval for an antipruritic agent containing nalfurafine hydrochloride and thereby extended the patent term beyond its original expiration in 2017. The Defendant-Appellee began marketing a product containing nalfurafine hydrochloride in 2018. The Plaintiff-Appellant subsequently filed an infringement action.

 2-1. Issue 1

Claim 1 covered an antipruritic agent containing as an active ingredient an opioid κ-receptor agonist compound represented by General Formula (I). Although General Formula (I) encompassed nalfurafine, it did not expressly encompass nalfurafine hydrochloride. Furthermore, an original claim directed to acid addition salts, including nalfurafine hydrochloride, had been deleted during prosecution. Accordingly, the parties disputed whether the Defendant-Appellee’s product fell within the scope of the claim.

 2-2. Issue 2

The Defendant-Appellee’s product used different excipients from the Plaintiff-Appellant’s product. The issue was whether the extended patent right could be enforced against such a product.

 3. Judgment of the Tokyo District Court (Court of First Instance)

At first instance, the Tokyo District Court held that the claim covered nalfurafine but not nalfurafine hydrochloride. Consequently, the Defendant’s product did not fall within the scope of the patent, and no infringement was found.

 4. Judgment of the IP High Court (Appellate Court)

4-1. With respect to Issue 1

On appeal, the IP High Court found that the Defendant-Appellee’s product fell within the scope of claim 1. The Court reasoned that the term “active ingredient” in light of the specification and common technical knowledge should be interpreted as the chemical substance that exerts the relevant pharmacological effect in vivo; therefore, the claim is directed to an antipruritic agent in which the compound represented by General Formula (I), regardless of whether administered as an acid addition salt, exerts pharmacological activity as the active ingredient in the body. The court further noted that although the Plaintiff-Appellant deleted original claims 1 and 2 during prosecution and amended Claim 3 into new claim 1 without including the language relating to acid addition salts (which had appeared in original claim 2), claim 3 had not been the subject of the rejection. Moreover, the written arguments submitted during prosecution contained no particular statement indicating an intention to exclude acid addition salts. Accordingly, it could not be found that the Plaintiff-Appellant had intentionally excluded the term “acid addition salt” from amended claim 1.

For these reasons, the court concluded that the Defendant-Appellee’s product fell within the scope of claim 1.

 4-2. With respect to Issue 2

The court reiterated that the effect of a patent during the extended term covers not only pharmaceuticals identical to those specified by the originator drug’s “ingredients, quantity, administration, dosage, indications, and effects,” but also pharmaceuticals that are substantially identical thereto. The Defendant-Appellee’s formulation differed from the Plaintiff-Appellant’s formulation only with respect to “ingredients,” and solely in terms of excipients other than the active ingredient; such excipients do not exert pharmacological activity and are added so as not to interfere with the therapeutic effect of the active ingredient. Accordingly, the court concluded that both formulations have identical technical features and effects in that they are antipruritic agents with nalfurafine as the active ingredient and the difference in excipient between the two formulations was merely minor or formal differences; therefore, the Defendant-Appellee’s formulation was substantially identical to the Plaintiff-Appellant’s formulation and the patent right during the extended term was enforceable against the manufacture and sale of the Defendant-Appellee’s product.

 5. Conclusion

In this decision, the court interpreted the claim term “active ingredient” to refer to the chemical substance that exerts the relevant pharmacological effect in the body. The court also concluded that, because the excipients neither exert pharmacological activity nor interfere with the therapeutic effect of the active ingredient, the effect of the patent during the extended term extends to generic products that differ from the originator product in their excipients. As a result, the court ordered the Defendant-Appellee to pay a total of more than JPY 20 billion (over USD 130 million) in damages.