[Article / Patents] Examining the patentability of impurity claims (Toru Matsuoka, Patent, July 2024)
更新日：10月15日
Article information
Article type: Publication review
Display and classification checked: 2026-09-30
Categories: Patents
Topics: Inventive step / Support requirement / Numerical limitations and parameters
Published on this website: 2026-09-29
[Article / Patents] Examining the patentability of impurity claims (Toru Matsuoka, Patent, July 2024)
Under what conditions does a claim that numerically limits only the impurity content of a known substance satisfy “inventive step” and the “support requirement”?
1. Inventive step: The “limits” of conventional methods are key
Reducing impurities itself is often considered an “obvious problem.” Inventive step therefore depends on whether the value is achievable by extending conventional methods.
No inventive step: Where optimization or repetition of known purification methods (recrystallization, columns, etc.) has a high probability of reducing impurities to that level (e.g., Heisei 24 (Ne) 10057, “Pravastatin sodium”).
Inventive step: Where repetition of conventional methods cannot achieve it because of physical or other limits, and it was achieved only by finding a new manufacturing or purification method (e.g., Heisei 20 (Gyo-Ke) 10430, “Acarbose”).
2. Support requirement: Identification of the problem is key
Principle: Where “reducing impurities” is the problem, its solution depends on a specific “manufacturing method.” A “product claim” without a manufacturing-method limitation then risks being found to exceed the disclosed scope.
Exception (a route to patentability): Where reducing impurities produces a “qualitatively different effect (remarkable action)” unforeseeable from the conventional substance, making a technical contribution substantially equivalent to providing a “new substance,” a claim to the substance itself may satisfy the support requirement.
Originally posted on LinkedIn: https://www.linkedin.com/feed/update/urn:li:activity:7510494040828801024/
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This log starts on 30 September 2026. Display and classification checks are distinct from a review of the legal analysis.
2026-09-30 — Presentation update: added the article type, this change log and a link to consultation options. The existing article text was preserved.
2026-10-01 | Name notation: replaced verified Japanese-script personal names with Roman-letter forms in this English article and its navigation. Legal analysis and original publication date unchanged.
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