TOPICS

“Composition for Treating Drug-Induced Constipation Comprising 15-Keto-Prostaglandin Compound”

 Overview:

This case is an instance where the Intellectual Property High Court upheld a Japan Patent Office (JPO) trial decision in an invalidation trial determining that an invention involved an inventive step.

▶Summary of Judgement and Link to Full Text (Japanese)

Main Issue:

Whether a person skilled in the art could have easily arrived at Difference 1 below based on the invention disclosed in Plaintiff’s Exhibit 3 (primary cited reference).

Difference 1

The “13,14-dihydro-15-keto-16-mono- or di-halogen-prostaglandin E compound” that is the active ingredient of the “composition for treating drug-induced constipation” according to Corrected Invention 4 (the broadest claim) is “13,14-dihydro-15-keto-16,16-difluoro-prostaglandin E₁” (PGE₁ compound) in Corrected Invention 4, whereas it is “13,14-dihydro-15-keto-16,16-difluoro-PGE₂ methyl ester” (PGE₂ compound) in the invention of Plaintiff’s Exhibit 3 (primary cited reference).

Summary:

(2) Concerning Difference 1

3. c) According to the disclosures of Plaintiff’s Exhibit 3 discussed above, the invention of Plaintiff’s Exhibit 3 is a laxative containing, as an active ingredient, Test Drug 8 (the PGE₂ compound of Plaintiff’s Exhibit 3), which exhibited the most superior enteropooling activity and minimal intestinal contractile activity of all the 19 prostaglandin compounds tested in the examples described in Plaintiff’s Exhibit 3. Furthermore, Test Drug 8, i.e., the PGE₂ compound of Plaintiff’s Exhibit 3, possesses all the aspects described as preferred in Plaintiff’s Exhibit 3: “the carbon bonds at positions 5-6 is a double bond”, “the number of carbon atoms is 20 to 22”, and “having a ketone at position 9 and a hydroxyl group at position 11 on the five-membered ring”.

Accordingly, even considering the disclosures in Plaintiff’s Exhibit 3 and Common General Knowledge A to E in combination, it should be held that no motivation can be found to convert the carbon bonds at positions 5-6 from a double bond to a single bond in the PGE₂ compound of Plaintiff’s Exhibit 3, which is the most superior in terms of enteropooling activity and intestinal contractile activity of all the test drugs described in Plaintiff’s Exhibit 3 and satisfies all preferred aspects, and further methyl-esterify the carboxyl group at position 1, to arrive at the PGE₁ compound of this case.

Comments:

The court judged that there is no motivation to deliberately convert the compound recognized in the primary cited reference (Plaintiff’s Exhibit 3) as “the PGE₂ compound of Plaintiff’s Exhibit 3, which is the most superior in effect and possesses all preferred aspects”, into a different compound (the subject PGE₁ compound).

Public Solicitation of Third-Party Observations at the IP High Court

With this judgment upholding the subject patent (Patent No. 4332353), and with the IP High Court judgments of April 9, 2026 (2025 (Gyo-Ke) No. 10059 and No. 10064) dismissing the trial for invalidation of the registration of extension of the patent term, the IP High Court solicited third-party observations (until September 30, 2026) regarding the appeal case (2026 (Ne) No. 10041) of the Osaka District Court judgment of March 3, 2026 (2025 (Wa) No. 10786 and No. 10790: the Amitiza case), an infringement lawsuit relating to this patent, on issues such as “how the scope of products covered by the effect of an extended patent right should be construed”.

https://www.courts.go.jp/ip/vc-files/ip/20260629%E5%8B%9F%E9%9B%86%E8%A6%81%E9%A0%85.pdf

In the upcoming IP High Court judgment taking into account the results of the solicited third-party observations, it is expected that the scope of effect of an extended patent right, which was held to extend to “substantially identical products” in the Grand Panel judgment of the IP High Court on January 20, 2017 (2016 (Ne) No. 10046: the Oxaliplatin case), will become clearer.

https://www.courts.go.jp/ip/vc-files/ip/file/yosi_28ne10046.pdf

Akiteru TAMURA