The Supreme Court's decision in AstraZeneca Canada Inc v Apotex Inc (2017 SCC 36) has significantly curtailed the ability to challenge a patent monopoly on the basis of an unsubstantiated promise in the patent application that the claimed subject matter of the patent will provide a particular utility (ie, the optically pure substance will have an improved therapeutic profile). This type of challenge became known as the ‘promise doctrine’, which called for an analysis of the specification and its claims independent of the purposive construction of the claims for the purposes of determining novelty and obviousness. The Supreme Court now holds that the promise doctrine is an incorrect approach for determining whether a patent is invalid for want of utility.
In AstraZeneca, Justice Rennie held that as the “improved therapeutic profile” was not essential to the claims to the “optically pure” substance, it was an error to invalidate the claims on the basis that the improved profile promised in the patent application had not been demonstrated or soundly predicted. Going forward, it appears that the claims as purposively construed will be the sole basis on which the utility (as well as the novelty and obviousness) of an invention will be judged.
In his construction of the claims for the purposes of obviousness, Rennie held that the improved properties of the patented optically pure substance were not part of the inventive concept of the claims (2014 FC 638 at 264-275). The claims were specific enough regarding the level of optical purity to consider the inventiveness of the claims on that basis alone. Recourse to the specification and its mention of ‘therapeutic effect’ was unnecessary to understand the meaning of the claims. Rennie held that it would not have been obvious for a skilled person to separate the claimed 99.8% optically pure substance (esomeprazole) from the known substance (omeprazole) based on his or her common general knowledge and the prior art.
Arguably, if Rennie had found the improved therapeutic profile of the optically pure substance to be an essential element of the invention as claimed, the result may have been different.
The promise doctrine was most often applied in pharmaceutical cases, where patents for improved versions of existing drugs are filed soon after initially testing in vitro or in animals but before testing in humans. However, it had begun to make its way in the analysis of patents for mechanical inventions, where skilled persons are much more likely to be able to understand the utility of the invention based on the description of a machine or device that embodies the invention, without any need for an explicit statement as to the utility of the invention (see Eurocopter v Bell Helicopter Textron Canada (2013 FCA 219 at 146 and 155)).
The Supreme Court’s decision in AstraZeneca clarifies once again that the utility of an invention must be judged on the invention as claimed, by construing the wording of the claims as they would be understood by the skilled person in light of the whole specification (see Whirlpool v Camco (2000 2 SCR 1067 at 49; Consolboard Inc v MacMillan Bloedel (Sask) Ltd (1981 1 SCR 504 at 521); and Canada (Attorney General) v Amazon.com, Inc (2011 FCA 328 at 37–47)) and not on ‘stray phrases’ in the patent specification describing promised advantages of the invention. Nevertheless, patentees are wise to be cautious about saying more than is necessary in their patent application about what their patented machines will be capable of doing, lest the patent claims are later held to be invalid – either because, by overpromising, the claims as worded become broader than the invention disclosed in the application (see Farbewerke Hoechst A/G v Canada Commissioner of Patents (1966 Ex CR 91 affirmed by 1966 SCR 604 at 20) or because the patent application is held to include statements made for the purpose of misleading (see Section 53(1) of the Patent Act).
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