Supreme Court of Canada Strikes Down Patent on Viagra

Teva Canada Ltd. v. Pfizer Canada Inc., 2012 SCC 60, is the first decision of the Supreme Court of Canada, since 1981, to comprehensively address the statutory requirement of a patentee to correctly and fully disclose the invention as set out in s. 27(3) of the Patent Act.

In a unanimous decision, which reversed the judgments of both the Federal Court of Canada and the Federal Court of Appeal, the Supreme Court of Canada held that Pfizer's patent covering Viagra failed to fully and correctly disclose the invention since it did not identify the only chemical compound which had been found by Pfizer to work in the treatment of erectile dysfunction (ED). The decision of the Supreme Court allowed Teva to immediately bring a lower cost generic version of Viagra to market in Canada and to seek damages for being kept off the market.

The active ingredient in Viagra, a molecule known as sildenafil, was originally developed by Pfizer for use in treating angina and hypertension. At that time Pfizer obtained a patent covering sildenafil and also claimed its use in treating angina and hypertension. While Pfizer was conducting clinical testing of sildenafil in angina patients, Pfizer's clinical physicians observed that some patients experienced a curious side-effect: spontaneous erections. Pfizer consequently carried out a clinical study to test the effect of sildenafil on patients with ED, generated some promising results, and applied for a second patent (Canadian Patent No. 2,163,446, the “446 Patent”), to cover the use of sildenafil in the treatment of ED. At the time of the application for the 446 Patent, only sildenafil had been tested in patients with ED.

The 446 Patent stated that an enormous class of compounds (containing at least 260 quintillion compounds) would work to treat ED. Claim 1 of the 446 Patent claimed all of those compounds for the treatment of ED, while Claims 6 and 7 each claimed a single compound for the treatment of ED. Claim 7 was for the use of sildenafil in the treatment of ED. Claim 6 was for the use of the back-up compound in the treatment of ED. Although the 446 Patent stated that “one of the especially preferred compounds induces penile erection in impotent males,” the patent did not disclose that the compound that was found to work in impotent males was sildenafil, that the compound is found in Claim 7, or that the remaining compounds had not been tested or found to be effective in treating ED.

As a precondition to receiving regulatory approval from the Minister of Health to produce a generic version of Viagra, Teva Canada Limited (formerly Novopharm Limited), was required to serve Pfizer with a notice of allegation (“NOA”) as Teva alleged in its NOA that Pfizer's 446 Patent was invalid on numerous grounds, including insufficient disclosure. Pfizer responded in 2007 by commencing an application in the Federal Court for an order prohibiting the Minister of Health from granting regulatory approval to Teva until the expiry of the 446 Patent.

Pfizer's application was heard and decided by Justice Michael Kelen in 2009. Although Justice Kelen noted that the experts of both Teva and Pfizer agreed that a person reading the whole of the 446 Patent would not know that sildenafil was the tested compound, how a limited subset of 9 “especially preferred” compounds were selected, or how to choose from the extremely large number of compounds in Claim 1 to find a compound that worked to treat ED, he held that the 446 Patent correctly and fully disclosed the invention because Claim 7 clearly claimed sildenafil to treat ED. Justice Kelen felt bound by a line of jurisprudence, starting with C. H. Boehringer Sohn v. BellCraig Ltd., [1962] Ex. C.R. 201, aff'd [1963] S.C.R. 410, which suggested that each claim in a patent is to be treated as a separate invention. Justice Kelen consequently granted Pfizer's application and issued an order prohibiting the Minister of Health from granting regulatory approval to Teva.

The Federal Court of Appeal upheld Justice Kelen's decision on the basis that the invention, namely the use of sildenafil for treating ED, was clearly described in Claim 7. The Court of Appeal held that the judge below was not required to find that the 446 Patent as a whole was clear. The Court went on to note that even if the 446 Patent was taken as a whole, a skilled reader would be able to narrow the range of compounds down to the two “especially preferred compounds” identified separately in Claims 6 and 7 and would then be able to conduct tests on those two compounds and determine which of them worked.

The Supreme Court of Canada, after a review of Boehringer and the jurisprudence which followed, rejected the notion that each claim in a patent must be considered as a separate invention. Justice Louis LeBel, writing for a unanimous Supreme Court, held that the Patent Act requires the Court to consider the patent as a whole, and not just the claims, to determine whether the disclosure requirements are satisfied.

In failing to disclose the identity of sildenafil as the effective compound, the 446 Patent failed to fully and correctly disclose the invention because it did not enable a person skilled in the art to make the same successful use of the invention as the inventor could have at the time of the application for the patent. The 446 Patent imposed upon the reader a research project. Even if a reader could have narrowed the search for 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. The “public's right to proper disclosure was denied” because the patent obscured the true invention.

The Supreme Court held that “Pfizer gained a benefit from the Act — exclusive monopoly rights — while withholding disclosure in spite of its disclosure obligations under the Act” and concluded that as “a matter of policy and sound statutory interpretation, patentees cannot be allowed to ‘game' the system in this way.”

David Aitken and Marcus Klee, of Osler, Hoskin & Harcourt LLP, and Ildiko Mehes, Vice President & General Counsel of Teva Canada Ltd., represented Teva Canada Limited.

Andrew Shaughnessy, Andrew Bernstein and Yael Bienenstock of Torys LLP represented Pfizer Canada Inc., Pfizer Inc., Pfizer Ireland Pharmaceuticals, and Pfizer Research and Development Company N.V./S.A.

Jonathan Stainsby and Andrew Skodyn of Heenan Blaikie LLP represented Canadian Generic Pharmaceutical Association.

Patrick Smith and Jane Clark and Henry Brown, QC, of Gowling Lafleur Henderson LLP represented Canada's Research-Based Pharmaceutical Companies.