The disclosure bargain


J. Sheldon Hamilton considers patent disclosure requirements in Canada in light of the sildenafil decision.

In November 2012, the Supreme Court of Canada ruled that Pfizer’s patent for the use of sildenafil (the active ingredient in VIAGRA) for the treatment of erectile dysfunction failed to meet the statutory requirement for disclosure of an invention: Teva Canada Limited v Pfizer Canada Inc, 2012 SCC 60 (Teva). While the patent specifically disclosed and claimed the use of sildenafil, the presence of other, allegedly non-useful embodiments meant that a skilled person could not identify the invention without testing. As a result, the patent did not meet the statutory requirement to “correctly and fully describe the invention and its operation or use as contemplated by the inventor”. If Canadian Courts apply the Teva decision broadly, the decision may be a potential watershed in Canadian patent law and may cast doubt over the validity of similar patents.

Background: The ’446 patent

The patent at issue (Canadian Patent No. 2,163,446 (’446)) discloses and claims the use of compounds for the treatment of erectile dysfunction (ED). In particular, the patent describes four classes of compounds:

• a general class,
• “preferred,”
• “more preferred”, and
• “particularly preferred”.

The patent also identifies nine specific compounds, including sildenafil, as especially preferred. The patent includes claims for the new use for various classes of compounds and for the nine especially preferred compounds (as a group). The patent also individually claims the use of two compounds in claims 6 and 7, including sildenafil (claim 7).

Two findings formed the underpinning for the decision. First, while the patent asserts that one especially preferred compound “induces penile erection in impotent males,” the patent does not identify the compound tested. Second, on the facts before the Court, sildenafil was the only compound that had been shown to have utility.

As a result, Teva argued that Pfizer knew the identity of the active compound (sildenafil), but failed to disclose that particular compound, obscuring its identity by disclosing other, presumably non-useful, compounds. Statutory provision: Section 27 of the Patent Act is the statutory provision governing disclosure of inventions. The provision requires, in part, that a patent must “correctly and fully describe the invention and its operation or use as contemplated by the inventor”. Canadian Courts have historically taken the view that such disclosure is an essential element of the patent bargain: in return for disclosure of the invention, the inventor receives a monopoly.

Judicial history

The Teva decision arose from an application brought under the Patented Medicines (Notice of Compliance) Regulations (PMNOC Regulations). Such proceedings link regulatory approval for generic pharmaceuticals (and subsequent entry biologics) to issues of patent infringement and validity.

Teva had alleged that the ’446 patent was invalid, including for insufficiency of disclosure. Pfizer sued under the PMNOC Regulations, seeking an order prohibiting the Minister of Health from issuing marketing approval to Teva for sildenafil. Justice Kelen of the Federal Court rejected Teva’s allegation and granted the order of prohibition. The Federal Court of Appeal affirmed his decision. Trial: 2009 FC 638: Justice Kelen ruled that sufficiency of disclosure must be considered for the specific claim in issue. Hence, the Court needed to consider whether the invention of claim 7 (the use of sildenafil in the treatment of ED) was sufficiently disclosed. Focusing on the claimed invention, Justice Kelen found that (i) sildenafil was the only compound in the patent found to induce erections, and (ii) the skilled person would not have known from the specification that the tested compound was sildenafil. However, he ruled that the skilled person could conduct tests on the two individual compounds claimed and determine which compound worked.

While Justice Kelen rejected the insufficiency allegation, he expressed significant concerns in obiter about the patentee’s failure to identify the tested compound:

“[136] By withholding from the public the identity of the only compound tested and found to work, sildenafil, the patent did not fully describe the invention. Obviously Pfizer made a conscious choice not to disclose the identity of the only compound found to work, and left the skilled reader guessing. This is contrary to the statutory requirement to fully disclose the invention.” [emphasis added]

Federal Court of Appeal (2010 FCA 242): The Federal Court of Appeal affirmed the decision of Justice Kelen, agreeing that sufficiency of disclosure should be assessed through the prism of claim 7. The patent was sufficient since it answered the questions “What is your invention?” and “How does it work?”

Supreme Court ruling

Supreme Court of Canada (2012 SCC 60): Teva sought and was granted leave to appeal to the Supreme Court. In addressing the disclosure issue, the Supreme Court stated that “the first step is to define the nature of the invention” in the patent. The Court rejected the claim-based approach used, looking instead to the entire specification to identify the invention disclosed. (The Court left open the possibility that different claims may disclose separate inventions, but this must be determined on a case-by-case basis.)

In the case of the ’446 patent, the Court found only one inventive concept: the use of sildenafil and other compounds in the treatment of ED. The Court did not accept that the use of sildenafil was a distinct invention. In concluding that the patent only related to one invention the Court emphasized the following ….click here to subscribe and read the whole article


J. Sheldon Hamilton, Smart & Biggar/Fetherstonhaugh

Sheldon is a Partner in the Toronto office and has advised and acted for clients in all aspects of litigation, particularly in the area of pharmaceuticals, for over 15 years. His client activities include assisting sophisticated multinational clients with multi-jurisdiction patent litigation and he has appeared as counsel before both the Ontario and Federal Courts, including the Federal Court of Appeal.

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