The Duty to Disclose 'The Invention': The Wrong Tool for the Job

Abstract

In its Sildenafil decision, the Supreme Court of Canada held Pfizer’s Viagra patent to be invalid for failure to disclose “the invention,” though it provided no explicit definition of that term. I argue that on the best reading of the decision, “the invention” means the new, useful, non-obvious contribution to knowledge which is disclosed in the patent. While this is initially attractive, I argue that on this definition, a duty to disclose the invention is unsound as a matter of law and policy, because it implies that if any important claim in a patent is invalid, all the claims will be invalid. This eviscerates Section 58 of the Patent Act, which provides that claims stand or fall independently. I argue that the Court’s reasoning was motivated by a mistaken belief that at the time of the application Pfizer had tested the other claimed compounds and knew them to be ineffective in treating ED, and that it claimed those compounds primarily to conceal the true invention. I argue that even if the Court’s understanding of the facts was correct, a duty to disclose the invention is not the appropriate tool to address the issue. The case properly raises questions relating to the duty of good faith disclosure, not a duty to disclose the invention.