Legal Alert: SCC Invalidates Viagra Patent in Canada

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Legal Alert: SCC Invalidates Viagra Patent in Canada

: November 9, 2012

On November 8, 2012, the Supreme Court of Canada invalidated Canadian Patent 2,163,446 (the “‘446 Patent”) for “pyrazolopyrimidinones for the treatment of impotence” (Teva Canada Ltd. v. Pfizer Canada Inc., 2012 SCC 60), which purported to cover sildenafil cirtrate, marketed as Viagra. In allowing Teva Canada’s appeal, the Supreme Court of Canada has provided further guidance on the what constitutes sufficient disclosure in a Canadian patent specification. Disclosure sufficient to permit future users to practice the invention to the same level of understanding as the inventor is the quid pro quo to obtaining any patent monopoly. A failure of the patent specification to fully disclose the invention goes to the patent filing as a whole, and should not be considered on a claim by claim basis.

The primary issue on appeal was whether or not the ‘446 Patent fulfilled the requirements in Section 27(3) of the Patent Act that, among other things, the specification must “correctly and fully describe the invention and its operation or use”. Intertwined with this issue was whether the Section 27(3) requirements are to be considered in respect of all claims individually, or to the specification as a whole.

The decision highlights the importance of providing a sufficient and clear disclosure which justifies and supports the entire invention and which is free from red herrings which might cause obscurity or ambiguity. The decision should strongly discourage the habit of patentees who claim unsubstantiated classes or variants and then fail to disclose precisely which solutions have really been shown to work. There may also be some concern that the Court is imposing a best mode requirement on patentees generally, which extends beyond the limited requirements on disclosures for machines set forth in Section 27(3)(c) of the Patent Act.

BACKGROUND

At issue in this case was Pfizer’s ‘446 Patent for sildenafil and salts thereof for the treatment of erectile disfunction, having a Patent Cooperation Treaty filing date of May 13, 1994, and claiming priority to a British application file June 9, 1993. While the corresponding British patent was declared invalid in England in 2002, the patent has survived various challenges in Canada until this case.

The patent application claims broad classes of possible pyrazolopyrimidinones (up to 260 quintillion compounds in the broadest class, down to nine most preferred compounds in the narrowest class) which might have been candidates to treat ED. Claims 6 and 7 each specified one particular compound. Nowhere in the specification does it state that sildenafil, shown only in claim 7, is the only known working active ingredient from those claimed.

In 2007, in advance of the pending expiry of the ‘446 Patent, generic drug maker Novopharm (now Teva Canada) sought a notice of compliance to create a generic version of the drug early on the grounds that the ‘446 Patent was invalid for obviousness, lack of utility and insufficiency of disclosure.

Decision of the Federal Court of Canada

In the initial application, Kelen J. prohibited the notice of compliance, by finding that the ‘446 Patent was useful, non-obvious and did not lack sufficient disclosure (Pfizer Canada Inc. v. Novopharm Limited, 2009 FC 638).

However, Kelen J. expressed strong discomfort with the drafting style of cascading claims for groups of compounds (most of which do not work) to create a disclosure which “plays games with the reader”, and with some of the jurisprudence, particularly C.H. Boehringer Sohn v. Bell-Craig Ltd., [1962] Ex.C.R. 201, 39 C.P.R. 201, aff’d [1963] S.C.R. 410, which appeared to require him to consider each claim as an independent invention for the purposes of determining sufficiency of disclosure. He went so far so to invite the Court to reconsider his decision on appeal if he misapplied the Boehringer case.

Decision at the Federal Court of Appeal

On appeal to the Federal Court of Appeal (Novopharm Limited v. Pfizer Canada Inc., 2010 FCA 242), Nadon J.A. affirmed the trial court, finding that utility and disclosure should be determined separately in respect of each claim as required by the Boehringer line of cases. Nadon J.A. also agreed that irrespective of whether or not the disclosure as a whole (specification and all claims) was clear, the description in isolation to claim 7 was both a clear description and sufficient disclosure of sildenafil. Further, Nadon J.A. affirmed the trial could finding that a person of skill in the art would have understood narrowing the classes of compounds down to the 2 listed, and that a choice between those two options was open to a finding of sufficiency of disclosure.

DECISION AT SUPREME COURT OF CANADA

LeBel J. wrote the unanimous decision of the Court, declaring the ‘446 Patent invalid on the basis that the insufficient disclosure did not fulfil the requirements of the Patent Act. The patentee cannot leave any room for testing or experimentation by the skilled reader in order to permit them to practice the invention at the end of the patent period, as to do so fails to meet the fundamental bargain which supports the patent monopoly.

The Court quickly determined that this case was not related to sound predication, and focused on the issue of sufficiency of disclosure.

The rule as to whether or not a sufficient disclosure has been made arises from first principles. The bargain at the foundations of patent law, that the purpose for the patent disclosure, the basis on which the monopoly is granted, “is to enable, not anybody, but a reasonably well informed artisan dealing with a subject-matter with which he is familiar, to make the thing, so as to make it available for the public at the end of the protected period” (Lord Halsbury, Tubes Ltd. v Perfecta Seamless Steel Tube Company, Ld. (1902), 20 RPC 77, pp 96, quoted this case at para 33).

In order for a patent to be valid, it must answer two questions: What is the invention? How does it work? (Consolboard Inc. v. MacMillan Bloedel (Saskatchewan Ltd.), [1981] 1 SCR 504). Further, for the disclosure to meet the requirements of the Patent Act, the answers to those questions must be sufficient to permit a skilled user, having only the specification, to make as successful a use of the invention as the inventor (Minerals Separation North American Corp. v. Noranda Mines Ltd. [1947] Ex. C.R. 106, 12 C.P.R. 99).

In response to the invitation from the trial court, the Supreme Court of Canada has ruled that the Boehringer case only applies after first considering sufficiency of disclosure in light of the specification as a whole.

Pfizer knew at the time of filing that sildenafil was the only working compound of the classes claimed, and failure to disclose this key fact was fatal to its patent. Merely stating that one of the nine especially preferred compounds has been shown to work was insufficient. Even if a skilled reader could have identified that the invention was either of the two compounds listed in claims 6 and 7, the fact that some experimentation would be needed to determine which, proves that the disclosure was insufficient for the purposes of the Patent Act.

As a result of the determination that the patent lacked sufficient disclosure, the entire patent was declared void.

As a side note, the Court impressed the fact that there is no disclosure requirement in respect of utility within the patent document itself where sound prediction does not apply. As to whether or not there is any higher disclosure requirement when the doctrine of sound prediction does apply, the Court refused to comment, thereby avoiding the issue of whether Canadian Patent Law conflicts with international obligations under the Patent Cooperation Treaty.

CONCLUSIONS

The Supreme Court of Canada has clarified that the issue of sufficiency of disclosure is to be considered with respect to the specification as a whole, and not on a claim by claim basis. The applicant must answer two questions in the application: 1. what is the invention; and 2. how is the invention made or put to use. In answering these questions, the disclosure must be sufficient to enable a skilled user to make as a good a use of the invention as the inventor.

Patent applicants should consider whether their applications meet these disclosure requirement, and how to draft patents to meet these expanded best mode disclosure standards in Canada.

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