균등론의 제3, 5요건 - 전구약물(prodrug)의 변경의 용이성, 의식적 제외의 문제 - - 대상판결 : 대법원 2023. 2. 2. 선고 2022후10210 판결 -

The case in question (Supreme Court, February 2, 2023, Decision 2022hu10210) dealt with the issue of whether a prodrug is equally infringing. Considering the length and cost of developing a new drug and the approval process required to market a drug, products that imitate a patent in the same way as a prodrug design should not be allowed. The ruling in this case considered the chemical and pharmacological characteristics of the prodrug and the extent of its utilization in the pharmaceutical industry, and determined that it falls within the scope of patent rights only if it can be easily modified by a person of ordinary skill in the art. This can be evaluated as a faithful reflection of the purpose of the doctrine of equivalents, which is to exclude imitators who do not contribute to technological progress while preventing unjustified expansion of patent rights. Of the five requirements of DOE(Doctrine of equivalents), ease of modification (the third requirement) and conscious exclusion (the fifth requirement) were the main issues in the case. The subject judgment clarified that the time for determining the ease of modification is “at the time of infringement” in infringement cases and “at the time of judgment” in scope determination cases, and thus, for the first time, it was clarified that materials published after filing can be taken into account in determining the ease of modification. It is preferable to judge the ease of modification based on 'at the time of infringement' because it is accurate to determine the ease of modification based on the time when the modification is actually made or possible, and it is necessary to prevent the evasion of patent infringement by using technology that has been developed after filing, as well as in line with the purpose of the equitable theory of substantial protection of patent rights and prevention of excessive expansion of the scope of rights. However, even if it is based on 'at the time of infringement', it is not easy to specify when actual infringement has occurred, and as technology advances, it is likely to be judged as easy to make changes over time, which may lead to excessive expansion of the scope of patent rights beyond what has contributed to technological progress, and the issue of whether there is equitable infringement for the same patent remains depending on the time of filing a lawsuit, etc. In addition, with regard to conscious exclusion, the subject judgment determined that despite the reduction of the claim scope, it was not consciously excluded in consideration of various circumstances that appeared in the litigation records, including the patent practice at the time of filing, which is significant in that it actively applied the principle of 'flexible estoppel' in the Supreme Court's 2014 Hu638 judgment.