The Supreme Court of Canada issued its long-awaited decision in an appeal challenging the “promise of the patent” doctrine (the “promise doctrine”). In recent years, the Federal Court had relied on the promise doctrine to invalidate a number of pharmaceutical patents. On June 30, 2017, the Supreme Court finally rejected the promise doctrine in AstraZeneca Canada Inc. v. Apotex Inc. (2017 SCC 36).

At issue was Canadian Patent No. 2,139,653 pertaining to esomeprazole, a compound used in reducing gastric acid. The ‘653 patent claimed, for example, omeprazole (claim 8), and use of omeprazole for gastric inhibition (claim 26). As of the filing date, the patentee had performed internal studies, but the drug had not yet been clinically proven in humans. The drug was very successful commercially. In an action for impeachment, the Federal Court held that the ‘653 patent was novel, non-obvious, and useful for certain purposes (a proton pump inhibitor to reduce production of gastric acid).

Nevertheless, the Federal Court held that the ’653 patent was invalid for lack of utility, on the basis that it failed to deliver on a promise. The invalidity turned on a statement on page 1 of the patent regarding improved therapy in patients. The Federal Court interpreted the statement as a promise of utility, which had not been met at filing, and invalidated the entire patent as a result. The patentee appealed to the Federal Court of Appeal, arguing that its patent was improperly invalidated on the basis of the promise doctrine. When the Federal Court of Appeal dismissed the appeal, the patentee appealed further to the Supreme Court of Canada.

The promise doctrine

Normally, no particular level of utility is required; a “mere scintilla” of utility will suffice. However, the promise doctrine held that, where the specification sets out an explicit “promise”, utility will be measured against that promise.[1]

The Supreme Court unanimously rejected the promise doctrine, as the correct approach to determining utility. The promise doctrine was unsound, incongruent with both the words and the scheme of the Patent Act, and excessively onerous in two ways. First, the promise doctrine determined the standard of utility that is required of a patent by reference to the promises expressed in the patent. Second, where there are multiple expressed promises of utility, the promise doctrine required that all be fulfilled for a patent to be valid.[2]

The correct approach to utility

The Supreme Court clarified the correct approach to utility. To determine whether a patent discloses an invention with sufficient utility, courts should undertake the following analysis. First, courts must identify the subject-matter of the invention as claimed in the patent. Second, courts must ask whether that subject-matter is useful — is it capable of a practical purpose (i.e. an actual result)?[3]

The Patent Act does not prescribe the degree of usefulness required; a scintilla of utility will do. A single use related to the nature of the subject-matter is sufficient, and the utility must be established by either demonstration or sound prediction as of the filing date. The purpose of utility is to prevent the patenting of fanciful, speculative or inoperable inventions. Even though utility of the subject-matter defined by a claim is a requirement for validity, a patentee is not required to disclose the utility of the invention to fulfill the utility requirement.[4]

Applying the correct approach to utility, the Supreme Court noted that the subject-matter at issue that had to be useful was the optically pure salts of the enantiomer of omeprazole. As the trial judge had accepted that it was soundly predicted by the relevant date that the optically pure salts of the enantiomer of omeprazole would be useful as a proton pump inhibitor to reduce production of gastric acid, there was utility, the ‘653 patent was valid, and the appeal was allowed.[5]


Patentees will welcome the decision of the Supreme Court. It rejects a doctrine of the Federal Court that was unworkable and severe. While cautioning that overpromising in patent applications is to be avoided, the Supreme Court recognized that invalidating a patent on the basis of an unintentional overstatement would discourage full disclosure. Finally, the decision clarifies that the correct approach to utility is grounded in the subject matter defined by a claim.