OTTAWA — The Supreme Court of Canada has invalidated the Viagra patent held by pharmaceutical giant Pfizer, opening the marketplace to cheaper versions of the popular erectile dysfunction drug.In a 7-0 decision, the high court sided with Teva Canada’s challenge of the legitimacy of the patent. It annulled Pfizer’s patent, saying it tried to “game” the system.The decision has big implications for users of erectile dysfunction drugs and the pharmaceutical industry because it allows companies to create generic versions that are usually cheaper for consumers.The Teva victory means the company can begin selling its own version of the drug.The ruling wipes out Pfizer’s market dominance with Viagra. Its patent was to have expired in 2014.The case also has broad commercial implications for patent law.The Patent Act gives a company a 16-year monopoly on a product if it can prove it is a new invention.In return, the patent-holding company must show publicly in its application how it created its product, so others can copy it later.“Pfizer gained a benefit from the act — exclusive monopoly rights — while withholding disclosure in spite of its disclosure obligations under the act,” Justice Louis LeBel wrote on behalf of the court. “As a matter of policy and sound statutory interpretation, patentees cannot be allowed to ’game’ the system in this way. This, in my view, is the key issue in this appeal.“Pfizer had the information needed to disclose the useful compound and chose not to release it.”This case turned on whether Pfizer deliberately thwarted Teva’s ability to copy the key chemical compound of the drug.Teva challenged the validity of the Pfizer patent, claiming it did not meet the law’s disclosure requirements.In its original patent application, Pfizer listed a massive number of chemical compounds, but didn’t specify which was the one that actually worked.Pfizer obtained the patent in 1998 after applying four years earlier. It was first challenged by the generic drug maker in 2007.Teva originally questioned Pfizer’s patent in Federal Court and the Federal Court of Appeal, but lost at both levels.