A Canadian Federal Court of Appeal decision earlier this year confirmed the presence of the “promise of a patent” doctrine in Canada, meaning that if a patent application sets out an explicit promise of an invention’s utility and the invention is found not to fulfill this promise, the patent could be found invalid.
In the case, Sanofi-Aventis v Apotex, the Federal Court of Appeal set aside a 2011 judgment by the Federal Court, which had found Sanofi-Aventis’s Plavix patent invalid. It found the patent to be valid, consistent with a 2008 Supreme Court of Canada decision.
The patent at issue was a selection patent which claimed only one configuration of a substance having an identical molecular formula as the racemic mixture, which comprises two mirror image configurations, claimed in the genus patent. While the selection – at least in one aspect – fell within the scope of the genus patent, it provided special advantages not disclosed in the genus patent. The Supreme Court explained that in this case it must be acceptable to read the specification in the patent to determine the inventive concept of the claims.
Reference to the specification enabled the Federal Court judge to conclude that inferences over the drug’s utility amounted to a “promise” which was found not to be fulfilled, meaning the patent was invalid. The Federal Court of Appeal found the patent to be valid and, at the same time, confirmed the “promise of a patent” doctrine with the qualification that only in cases where the specification sets out an explicit "promise" will utility be measured against that promise.
Where exactly the line of “explicitness” will be drawn is difficult to predict for any given patent. Guidance for the future may be found in earlier Supreme Court decisions which have always accepted that the true interpretation of a patent can be reached by considering what a competent workman, reading the specification at its date, would have understood it to have disclosed and claimed.