# When a dosage clarification changes a patent claim: Korea’s Supreme Court on correction Decision 2023Hu11487 examines whether adding a mass-basis explanation to pharmaceutical claims qualifies as an admissible correction. Source: https://www.iplexlaw.co.kr/en/blog/brunch-case-1781 HOME / NEWS & INSIGHTS NEWS & INSIGHTS When a dosage clarification changes a patent claim: Korea’s Supreme Court on correction Decision 2023Hu11487 examines whether adding a mass-basis explanation to pharmaceutical claims qualifies as an admissible correction. Patents 2026.10.01 published IPLEX 6 min read A short addition with a potentially different technical meaning Yongduck Kim of IPLEX reviews the Korean Supreme Court’s decision of 26 June 2025, 2023Hu11487. The case concerns correction of claims for an antihypertensive pharmaceutical composition. A claim defines the technical subject matter for which protection is sought. Here, unchanged dosage numbers did not necessarily mean an unchanged invention. What the proprietor sought to add Claim 1 referred to 30 mg of fimasartan potassium salt or its hydrate and 5 mg of amlodipine besylate. During invalidation proceedings, the proprietor sought to add, respectively, “30 mg as fimasartan potassium salt” and “5 mg as amlodipine”. A hydrate incorporates water molecules; the salt, hydrate and underlying active moiety are distinct chemical forms. Five milligrams of amlodipine besylate is not necessarily the same quantity as a formulation containing the equivalent of five milligrams of amlodipine. The numerical value can remain the same while the substance used as the mass reference changes. The correction test starts with the original claim Under the Korean Patent Act, a correction must fall within a permitted purpose, such as narrowing the claims, correcting an error or clarifying an ambiguity, and must not substantially broaden or change the claims. Calling an addition an explanation does not satisfy those requirements. The original technical meaning must first be established. The description and drawings inform an objective reading of the claim’s technical terms. They do not permit the protection stated in the claim to be rewritten, expanded or restricted. In this case, the description itself distinguished the compounds, and the working and preparation examples expressed quantities by reference to fimasartan potassium trihydrate and amlodipine besylate. Why the Supreme Court rejected the premise adopted below The Patent Court, in decision 2023Heo10613 of 30 November 2023, had accepted the correction and assessed claims 1, 4 and 12–14 as corrected, finding no invalidity for the disclosure requirements or inventive step. The Supreme Court concluded that the correction requirements were not met because the original dosage basis was already clear in its technical context. The original language was read as 30 mg of fimasartan potassium salt or 30 mg of its hydrate, together with 5 mg of amlodipine besylate. It was not already a statement of the converted amounts later placed in parentheses. The Court also identified the possibility that changing the amounts of the antihypertensive components could change the invention’s effect and thus substantially change the claims. That observation of a possibility should be distinguished from its conclusion that the requested correction was inadmissible. Reversal and remand, not immediate invalidation of the entire patent The Supreme Court reversed and remanded the case to the Patent Court. Invalidity of claims 1, 4 and 12–14 must be reconsidered using the uncorrected wording; the other claims at issue depend on claim 1 or share its other features apart from the medical use. The decision does not itself declare the entire patent invalid. It removes the corrected wording as the premise for the earlier assessment. Points to check when drafting or seeking correction State the reference basis for every quantity precisely: the compound’s own mass and an amount expressed as an active moiety can differ. Align the claims, description and examples. When comparing proposed corrections, examine the technical content and effects as well as the changed characters. In an invalidity dispute, prepare the analysis both for acceptance and for rejection of the requested correction. Which wording survives that threshold issue determines the claims against which the invalidity grounds must be assessed. The practical lesson is to ask what each number measures, not merely whether the number has changed. Original figure labels and forms are preserved; the surrounding text explains their meaning. Read the Korean source This article reflects the information available when it was published. Contact us to discuss your circumstances. 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