The Supreme Court of Canada has issued a decision finding that Pfizer’s Canadian patent No. 2,163,446 (the ‘446 patent) for Viagra™ is invalid, following an appeal by generic drug manufacturer Teva Canada Limited challenging the patent’s validity in a notice of compliance proceeding. This decision paves the way for Teva and others to obtain regulatory approval to sell a generic version of sildenafil (the generic name for Viagra™) in Canada prior to the 13 May 2014 expiration date of the ’446 patent.

The Supreme Court of Canada found the ’446 patent to be invalid for insufficient disclosure. Specifically, Pfizer stated in the application that “one of the especially preferred compounds” worked to treat erectile dysfunction (based on a study that had been conducted). However, the application did not disclose the identity of the compound that worked. The claims of the ’446 patent covered many compounds, and specifically claimed two compounds. One of these compounds was sildenafil, but the other was a compound that is not useful to treat erectile dysfunction. Because a skilled person would need to conduct further testing to determine which of the two specifically claimed compounds would work to treat erectile dysfunction, the Court concluded that the disclosure requirements of the Patent Act had not been met.

In deciding that the ’446 patent is invalid, the Court emphasized that the grant of a patent is a bargain: society grants the patent holder a time-limited monopoly in exchange for being provided with proper disclosure of the invention and how it works.

This case will require careful consideration by those involved in the preparation of patent applications.  In particular, the lower courts had considered the validity of the ‘446 patent on the basis that each claim is a separate invention, and therefore had evaluated the disclosure requirements with respect to each claim, rather than with respect to the disclosure as a whole.  The Supreme Court of Canada held that this approach was not correct, and found that the sufficiency of the disclosure must be evaluated with respect to the invention as a whole.  Typically, a patent will disclose a single invention, although the Court acknowledged there could be circumstances in which each claim in a patent discloses a separate invention.  Thus, patent drafters will need to ensure they have fully and clearly described those embodiments of the invention that provide the promised utility.  In the case of the ‘446 patent, for example, inclusion of a working example identifying sildenafil or a clear identification of the compound that had been found to be useful might have saved the patent.

This decision is not quite final, as Pfizer is asking the Supreme Court of Canada to reconsider the remedy in this case.  Because the proceeding is a summary proceeding under the Patented Medicines (Notice of Compliance Regulations), the appropriate remedy would typically be limited to allowing the Minister of Health to issue a notice of compliance to Teva. Pfizer argues that the Court had no jurisdiction to also declare the ‘446 patent to be invalid.  The Supreme Court of Canada’s invalidity declaration has already caused some problems for Pfizer in an impeachment action brought by Apotex Inc. against the ‘446 patent:  the Federal Court granted summary judgment to Apotex because, in view of the Supreme Court of Canada’s ruling, no result would have been possible after a full trial other than a finding that the ‘446 patent is invalid.

A complete copy of the judgment of the Supreme Court of Canada is available from the Court’s website at http://scc.lexum.org/decisia-scc-csc/scc-csc/scc-csc/en/item/12679/index.do.