Supreme Court of Canada addresses sufficiency of patent disclosure

4 minute read
09 November 2012

By Marc Richard & Adrian J. Howard

The Supreme Court of Canada has unanimously overturned decisions of the Federal Court and Federal Court of Appeal, and held, in the context of proceedings under the Patented Medicines (Notice of Compliance) Regulations [PM(NOC) Regulations], that Pfizer’s Canadian Patent No. 2,163,446 for the use of VIAGRA (sildenafil) was void.

The judgment turned on whether the patent sufficiently disclosed the invention. The Supreme Court did not regard this to be a case of sound prediction and thus did not directly address the issue. In particular, the Court declined to address whether there is an “enhanced” disclosure requirement for sound prediction, which has sometimes been applied by lower courts.

Teva Canada Ltd., the appellant, had alleged that the patent did not meet the disclosure requirements under section 27(3) of the Patent Act. The Federal Court disagreed, stating that Pfizer had complied with that section and the patent disclosed a meritorious invention. In coming to this decision, the validity of each claim was determined separately pursuant to section 58 of the Patent Act. It was found that the patent sufficiently disclosed both the invention and how it worked; principally when one considered claim 7, a claim for the use of sildenafil alone. The patent described one of the compounds as “especially preferred,” and sildenafil was specifically claimed. Indeed, the claim to sildenafil was one of only two claims to the use of a single compound. Accordingly, the Federal Court prohibited the Minister of Health from issuing a notice of compliance (NOC) to Teva.

The Court of Appeal agreed with this reasoning and also upheld the finding that the allegation of invalidity was not justified.

In overturning the lower courts, Justice LeBel, writing for the Supreme Court, began by restating the role of patents and the quid pro quo of the patent bargain: disclosure of the invention in exchange for exclusive rights. In his view, the disclosure requirement is a part of this bargain and should not be reviewed on a claim-by-claim basis. 

Justice LeBel construed the patent to describe a class of compounds useful in the treatment of erectile dysfunction (ED). Although sildenafil was an especially preferred compound, nothing in the patent disclosure distinguished it from the other especially preferred compounds. To the Court, the use of sildenafil as well as the other compounds for the treatment of ED comprised a single inventive concept. However, the Court held that since the patent did not specifically disclose sildenafil as the compound Pfizer had tested and shown to work, the patent was void for insufficiency under section 27 of the Patent Act (although, given that this was a proceeding under the PM(NOC) Regulations, the patent could not be “voided” but rather the Court could find that Teva’s allegations of invalidity were justified and the order prohibiting the Minister from issuing an NOC be set aside).

Of particular interest were the Court’s comments regarding the role of the patent claims. The Court did not regard each claim as relating to a separate invention but that the invention must be construed on the basis of the whole specification. In this case, given that there were two claims to the use of a single compound but neither was indicated to be the especially preferred compound sildenafil, the Court held that a skilled reader could not make the same use of the invention as the inventor could at the time of his application. Thus, Pfizer’s disclosure obligation under the Patent Act was not fulfilled.

As a result of this judgment, Teva may now proceed with marketing and selling a generic version of Viagra.

The judgment can be found at:

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