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Northern Exposure: Pfizer Canada’s Viagra® Patent Invalidated

Written by: France Côté
BENOÎT & CÔTÉ
Posted: Dec 16, 2012 @ 10:30 am

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Northern Exposure is a new series of articles that will focus on Canada and Canadian intellectual property laws, cases and procedures. From time to time we will also publish a Canadian perspective on important issues relating to US and Global intellectual property. For more articles please visit Northern Exposure – Canadian IP.

The Supreme Court of Canada rendered a decision on November 8, 2012 effectively canceling Viagra® Canadian patent a year and a half before its natural expiration date. This ends Pfizer’s exclusivity on the blockbuster erectile disfunction drug and opens the market up to generics. While certainly a press- worthy event, this decision does not change the Canadian patent landscape – but rather reinforces it.

The story begins when Teva Canada Limited, a generic company, filed for a “notice of compliance”, arguing that vague claims in the Pfizer patent would allow it to essentially produce a generic version of Viagra® through the backdoor. Normally, in a case where the “notice of compliance” is allowed, Teva Canada Limited would have been given the sole right to begin producing generics. The patent, however, would not be considered void. The Federal Court rejected the notice, so Teva appealed the decision to the Federal Court of Appeal and finally to the Supreme Court of Canada. The climb up the ladder essentially brought the case against the patent to a new level of scrutiny and interpretation.

Justice J. LeBel concluded not that Teva Canada Limited be granted the “notice of compliance”, but that Patent 2, 163, 446, popularly known as the Viagra® patent, be voided, allowing not only Teva Canada Limited, but any generics manufacturer to begin producing Viagra® clones. The reason: in none of the seven claims does the patent point to the exact compound that “induces penile erection in impotent males”. This exact compound, sildenafil, is mentioned alongside many others that do not cause the desired side effect.

By not disclosing the specific compound, the patent does not in a “full, clear, concise and exact” manner adequately describe the technology.

Furthermore, Justice LeBel clarified that the patent system is a “bargain”. Companies that develop innovative technologies are allowed exclusive rights for a limited time as long as they disclose the “how-to’s” for the public good. By not disclosing the specific compound that resulted in the technology’s stated innovation, Pfizer Canada was not sharing this “know-how” and broke their side of the bargain. As is so eloquently stated in the Supreme Court of Canada’s published decision: “If there is no quid — proper disclosure — then there can be no quo — exclusive monopoly rights.”

More than anything, this last line can perhaps describe an element of the Canadian patent system that is often forgotten. In the rush to capitalize and monopolize, it is easy to forget that patents are not only a boon to the patent holders but to society. They are published for a reason, and that reason is to disseminate new innovations for the benefit of society. Time-sensitive exclusivity is simply a pat on the back for all the hard work and a job well done. Teva Canada Limited v. Pfizer Canada Inc. is also a warning to all that clarity and sufficient disclosure is essential in the redaction of patent applications to result in valid patents. The Viagra® patent is a potent example of a failure in clarity and lack of disclosure. The case is an exception that should not affect well-written patents.

Update: Only days after the decision was issued, Pfizer Canada has now asked the Supreme Court to overturn their decision, claiming the Court overstepped its bounds. It would be fairly unprecedented for the Supreme Court to reconsider a ruling, so it can safely be assumed that it will stand.

About the Author

France Côté is a registered patent agent in Canada (since 1992) and in the United States (since 1992). France’s expertise allows her to represent a wide range of clients. She works with start-up and multi-national biotechnology companies, as well as domestic and international universities and research institutes. Although France’s background is biochemistry, her expertise is varied and includes inventions in the following fields: simple mechanics, chemistry, biochemistry, pharmaceuticals and business methods. France joined Swabey Ogilvy Renault in 1992 and became a partner in 1998. After the merger with Ogilvy Renault she was the chair of the Montreal IP group from 2003 to 2005. France was a co-founding partner of the Montreal Office of Bereskin & Parr in 2005. She co-founded BENOÎT & CÔTÉ with Marc in 2009.

BENOÎT & CÔTÉ is located in Montreal, Canada.


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  1. This is arguably one of the most important and instructive decisions to have been handed down in the chemical/pharma field in recent years and has implications way beyond Canada.

    The main claim of the patent in issue was directed to a Markush group with, according to the opinion, 260 quintillion possible compounds. There was evidence that one of them, sildenafil, was effective for that purpose. The opinion records that none of the other compounds had been shown to be effective. Although test data was available to Pfizer and the specification indicated that tests had been carried out, the tests were not reported in the specification and sildenafil was not identified as the most promising compound.

    As the opinion explains, sildenafil could not be considered in isolation from the other inactive compounds because the specification provided no basis for doing so:

    “[66] In this case, if we consider the specification as a whole, there is nothing to support the view that the use of sildenafil for the treatment of ED is a separate invention from the use of any of the other claimed compounds for that same purpose. No specific attributes or characteristics are ascribed to sildenafil that would set it apart from the other compounds. Even if we take into consideration the fact that sildenafil is an “especially preferred compound”, there is still nothing that distinguishes it from the other eight “especially preferred compounds”. The use of sildenafil and the other compounds for the treatment of ED comprises one inventive concept.”

    At para [76] the opinion explains:

    Pfizer had the information needed to disclose the useful compound and chose not to release it. Even though Pfizer knew that the effective compound was sildenafil at the time it filed the application, it limited its description to the following statement:

    “In man, certain especially preferred compounds have been tested orally in both single dose and multiple dose volunteer studies. Moreover, patient studies conducted thus far have confirmed that one of the especially preferred compounds induces penile erection in impotent males.”

    It chose a method of drafting that failed to clearly set out what the invention was. Even now, in its factum to this Court, Pfizer offers no explanation as to why — knowing that Claim 7 contained the tested and thus, the useful, compound — it elected to withhold that information.

    An inventor has a choice to disclose the invention or to keep it a trade secret, but if the disclosure route is followed then it is not possible simultaneously to disclose and conceal, as was established in a line of authorities form R. v Arkwright onwards. For that reason, in this instance, the patent did not stand up in court.