IP High Court Upholds Patent on Drug-Induced Constipation Treatment: No Motivation to Modify the Optimal Compound

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The Intellectual Property High Court of Japan ruled on June 23, 2026, in Case No. 10055 (Gyo-Ke) of 2025, upholding the inventive step of a constipation treatment patent. The court found that since the prior art (Exhibit 3) already identified the 'PGE2 compound' as the optimal formulation, there was no motivation for a person skilled in the art to modify it into the patented 'PGE1 compound.' This decision provides a critical defense strategy for biotech and chemical companies: when a prior art represents the 'best solution,' it cannot easily be used to challenge the inventive step of a subsequent modified patent.