IP Law Daily, PATENT NEWS—Canada’s Supreme Court Finds Pfizer’s Viagra Patent Invalid for Lack of Disclosure, (Nov 8, 2012)

By Peter Reap, J.D., LLM

Canada’s Supreme Court today struck down the patent for the erectile dysfunction drug Viagra held by Pfizer Canada Inc. and related entities (collectively, “Pfizer”) because the patent’s specification would not have enabled the public “to make the same successful use of the invention as the inventor could at the time of his application,” the court decided (Teva Canada Ltd. v. Pfizer Canada Inc., November 8, 2012, LeBel, L.).

Teva Canada Limited, a subsidiary of Teva Pharmaceutical Industries Ltd—the world’s largest generic drug manufacturer—challenged the patent (Patent 2,163,446, “Patent '446”) as invalid for concealment and obscurity. In Teva’s view, the patent’s cryptic description of sildenafil—the only active ingredient in Viagra—as “one of the especially preferred compounds” was undeniably obscure. The High Court agreed.

As required by s. 2 of the Patent Act, an invention must be novel, the court observed. In the instant case, the invention is not sildenafil, per se, because this compound was already known. The invention is therefore not sildenafil, but the use of sildenafil to treat ED.

Considering the specification as a whole, there was nothing to support the view that the use of sildenafil for the treatment of ED was a separate invention from the use of any of the other patents claimed compounds for that same purpose, the court held. No specific attributes or characteristics are ascribed to sildenafil that would set it apart from the other compounds. Even taking into consideration the fact that sildenafil was an “especially preferred compound,” there was still nothing that distinguished it from the other eight “especially preferred compounds”.

In fact, the patent itself suggested that the entire class of claimed compounds would be effective in treating ED. The first sentence of the specification stated: “This invention relates to the use of a series of [compounds] for the treatment of impotence.” The following also appeared on the second page of the specification: “Unexpectedly, it has now been found that these disclosed compounds are useful in the treatment of erectile dysfunction.”

In light of s. 27(3) of the Act, it was the specification and not just the claims that the court must consider to determine whether the patent in question meets the disclosure requirements. Section 27(4) provides that the claim or claims must define the subject-matter of the invention distinctly and explicitly.

Although Patent '446 included the statement that “one of the especially preferred compounds induces penile erection in impotent males,” the specification did not indicate that sildenafil was the effective compound, that Claim 7 contained the compound that worked, or that the remaining compounds in the patent had been found not to be effective in treating ED. The claims were structured as “cascading claims”, with Claim 1 involving over 260 quintillion compounds, Claims 2 to 5 concerning progressively smaller groups of compounds, and Claims 6 and 7 each relating to an individual compound.

The disclosure in the specification would not have enabled the public “to make the same successful use of the invention as the inventor could at the time of his application,” because even if a skilled reader could have narrowed the effective compound down to the ones in Claim 6 and Claim 7, further testing would have been required to determine which of those two compounds was actually effective in treating ED, according to the court. As the trial judge stated, “[a] skilled reader would then conduct tests on those two compounds and determine which of those compounds worked.” And as he also stated, “the skilled reader must undertake a minor research project to determine which claim is the true invention.”

The disclosure failed to state in clear terms what the invention was. Pfizer gained a benefit from the Act—exclusive monopoly rights—while withholding disclosure in spite of its disclosure obligations under the Act. As a matter of policy and sound statutory interpretation, patentees could not be allowed to “game” the system in this way, the court commented.

Although s. 27 did not specify a remedy for insufficient disclosure, the logical consequence of a failure to properly disclose the invention and how it works would be to deem the patent in question invalid. This flowed from the quid pro quo principle underpinning the Act. If there was no quid — proper disclosure — then there can be no quo — exclusive monopoly rights. Thus, the patent was void, the court held.

The case is Docket No. 33951.

David W. Aitken for Teva Canada Limited. Andrew Shaugnessy for Pfizer Canada Inc.

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