Canada’s False Promises

In the recent case of AstraZeneca Canada v Apotex, the Supreme Court of Canada has unanimously rejected the controversial “promise doctrine” in relation to the utility requirement under Canadian patent law.

What is the “Promise doctrine”?

In brief, the “promise doctrine” provided that where a patent specification is found to promise that it can be used for a certain purpose, it must be specifically demonstrated or soundly predicted as of the patent’s filing date that it can achieve that purpose.

For example, a patent specification discloses for the first time new drug X and also discloses that drug X treats specific disease Y.  However, it is not explicitly shown in the specification how it treats disease Y, and it was not reasonably predictable, at the filing date of the patent, that drug X in fact treats disease Y.  It is therefore possible that the patent may have been held invalid in Canada, as the patent “promised” a specific utility for drug X but failed to reasonably demonstrate how that utility was achieved.

This is rather at odds with the utility requirement of other jurisdictions, such as the US or the European Patent Office, wherein generally it is only necessary to show that an invention can be made or used in any kind of industry (i.e. it has at least some form of industrial application).

Why was the “Promise doctrine” an issue?

The “promise doctrine” was primarily an issue for pharmaceutical and biosimilar inventions, wherein a medical use was specified but not exemplified in the patent specification.

In the case of AstraZeneca Canada v Apotex, AstraZeneca had a Canadian patent (CA 2,139,653) that claimed the optically pure salts of esomeprazole (the (S)-(−)-enantiomer of omeprazole).  Esomeprazole is part of a class of drugs known as proton pump inhibitors, which inhibit the production of gastric acid.

At first instance, the claims were considered to be novel and inventive.  However, the claims were considered to be lacking utility because, although the patent proved to be useful for some purposes, “it promised more than it could provide” (i.e. the patent disclosed medical use indications for the optically pure salts of esomeprazole that were neither exemplified nor reasonably predictable at the date of filing).

The patent was therefore held invalid.

Unsound Doctrine?

Upon appeal, the Supreme Court of Canada analysed the origins of the “promise doctrine” (the origins of which trace back to archaic English law) and concluded that “this doctrine…is unsound” on the ground that the doctrine conflated utility and sufficiency requirements (which ought to have been considered separately).

The Court noted that conflating those requirements could result in a scenario wherein an Applicant may be deprived from obtaining patent protection for his invention where not every promised use was sufficiently demonstrated.  This could give rise to a situation where an Applicant would not necessarily fully disclose his invention for fear of being penalised under the “promise doctrine”.  The Court therefore considered the “promise doctrine” to be an unacceptable application of the law, as the patent system is supposed to encourage inventors to fully disclose their inventions, not suppress full disclosure of those inventions.

The Court, setting aside the “promise doctrine” as unsound law, set out a new two-step test to determine whether a patent discloses an invention with sufficient utility:

1. Courts must identify the subject-matter of the invention as claimed in the patent

2. Courts must ask whether that subject-matter is useful i.e., is it capable of a practical purpose

Applying that test to the case under appeal, the Court found that:

1. The subject matter of the invention was optically pure salts of the enantiomer of omeprazole, i.e. esomeprazole.

2. At the filing date of the patent in question, the optically pure salts of the enantiomer of omeprazole would be useful as a proton pump inhibitor to reduce the production of gastric acid.  Use as a proton pump inhibitor is related to the subject matter of the patent, thereby making it useful within the meaning of section 2 of the Canadian Patent Act.

The Court therefore allowed the appeal, finding that the AstraZeneca patent was not invalid for lack of utility.

This test is more in line with the utility/industrial applicability requirements of other jurisdictions around the world, and will be a welcome decision for pharmaceutical and biosimilar companies as it should (in theory) make the utility requirement in Canada more predictable and less of a somewhat unnecessary hurdle.