A multinational pharmaceutical company S, which owned the improvement patent of isomer and salt for basic substance patent filed an injunction action for patent infringement and damage action against C Pharmaceutical company and 4 other pharmaceutical companies, which manufacture and sell thrombus treatment. Due to S’ lawsuits, they suffered difficulties in business, and they would be subject to a several billion won damage award if the court decided that they infringed S’ patent. AIP represented the patent infringement case and the Supreme Court case. AIP successfully draw out a court decision to invalidate the patent and finding of noninfringement by closely studying the legal principal of determining patentability for selective invention and patentability of invention on isomer of chemical substances.