A broken promise – The Supreme Court of Canada reverses Canada's "promise of the patent" doctrine

Lab tests

Life Sciences Alert


The Supreme Court of Canada (or SCC) has dealt a significant blow to the “promise of the patent” doctrine—a controversial judge-made approach to the question of patent utility in Canada that has been heavily criticized over the past decade. Innovative drug companies have repeatedly attacked the legitimacy of the so-called “Promise Doctrine” due to the number of patents for blockbuster drugs that have been invalidated in Canada for failing to meet “promises” in patent specifications. At the end of the day, and to the delight of innovators, the SCC has finally decried the promise of the patent to be “not good law”.

The appeal concerned AstraZeneca’s Canadian Patent No. 2,139,653 (the ‘653 patent) for the drug esomeprazole (NEXIUM®), a proton pump inhibitor used to reduce gastric acid production in the treatment of a variety of gastrointestinal disorders.

At trial, the Federal Court held the ‘653 patent was invalid for lack of utility based on the “promise of the patent” doctrine, or “Promise Doctrine”. Applying the Promise Doctrine to the ‘653 patent, the Federal Court identified two promises in the specification: (1) the use of esomeprazole as a proton pump inhibitor, and (2) an improved therapeutic profile based on improved pharmacokinetic and metabolic properties. Although the first promise was satisfied by the subject-matter of all claims, the patent was held invalid for lack of utility as the second promise was found to have been neither demonstrated nor soundly predicted as of the filing date of the patent. As this “promise” of “improved therapeutic profile” extended to all of the claims, the entirety of the ‘653 patent was held invalid. The Federal Court of Appeal upheld these findings. 

The main issue before the SCC was whether the Promise Doctrine was “the correct standard of utility under the Patent Act” in Canada. Section 2 of the Patent Act requires the subject-matter of an invention to be useful; however, apart from this, the Act is silent on the standard of utility to be applied. The Canadian Federal Courts had determined whether a patent was invalid for lack of utility by considering whether statements in the patent specification “promise” a particular usefulness for the subject-matter of the patent. If there was no demonstrated or soundly predicted utility that met the so-called “promise” then the patent was held invalid.  The result of this approach was seen by the SCC to have been overly onerous for patentees in that: (1) there was a heightened standard of utility which was applied if there was a “promise” found in the patent specification, and (2) the approach required a patentee to meet all promises where there are multiple, expressed promises of utility.   

The SCC found the Promise Doctrine to be flawed as it conflated the utility requirement under section 2 of the Patent Act with the disclosure requirement under section 27(3).  Under section 27(3), the inventor must fully disclose the invention to enable the skilled person to use or construct the invention when the monopoly period has expired. Section 2, on the other hand, requires the subject-matter of the invention to be “useful”—the bounds of which are defined by the claims. As such, by considering statements outside the claims as part of the utility analysis, the Promise Doctrine “effectively imports s.27(3) into s. 2 inappropriately by requiring … any disclosure of use to be demonstrated or soundly predicted at the time of filing”. Further, the effect of the Promise Doctrine was to undermine the disclosure requirement by discouraging fulsome disclosure for risk of invalidity on the basis of “an unintentional overstatement of even a single use”.  

To clarify the utility analysis, the Court provided 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)?

The Court also went on to confirm that the utility of the claimed subject-matter must be established by either demonstration or sound prediction as of the filing date. The SCC confirmed that a mere scintilla of utility will do, as the Act does not prescribe any degree or quantum of usefulness to be required. A single use related to the nature of the subject-matter is sufficient.

Applying this approach to the facts of the case before the Court, the appeal was allowed and the ‘653 patent was held valid on the basis that it was sufficient for the patentee to have demonstrated the utility of esomeprazole as a proton pump inhibitor, despite whatever statements might have been made in the specification.  

The demise of the Promise Doctrine in Canada will likely be viewed as a big “win” for rights holders generally. The Court has now established a clear threshold for patent utility that is lower than the Federal Courts had applied under the Promise Doctrine. By restricting the assessment of utility to the claims, patentees can rest easy knowing that full, frank, and good faith disclosure in the specification will not jeopardize their patent rights, if challenged.