The recent decision of the Federal Court of Appeal in Mylan Pharmaceuticals ULC v. Eli Lilly Canada Inc. et al.,2016 FCA 119 (“Mylan”), highlights the significant uncertainties surrounding the doctrine of obviousness-type double patenting in Canada and the reluctance of the appellate court to settle this difficult area of law.

The patent at issue in this case was Canadian Patent No. 2,226,784 (the “‘784 Patent”), which claims the compounds tadalafil and 3-methyl tadalafil. These compounds are used for the treatment of erectile dysfunction with Eli Lilly selling tadalafil under the brand name CIALIS. The Court’s decision in Mylan is an appeal from a decision of the Federal Court, 2015 FC 17, which granted an order prohibiting a Notice of Compliance from being issued to Mylan and thus preventing Mylan from marketing a generic version of tadalafil. Mylan appealed this decision alleging that the ‘784 Patent was invalid on the basis of obviousness-type double patenting and a lack of utility. In dismissing the appeal, the Federal Court of Appeal focussed on the allegation of obviousness-type double patenting.

It is well established under Canadian patent law that there are two branches to the prohibition against double patenting (Whirlpool Corp. v. Camco Inc., 2000 SCC 67 (“Whirlpool”)). The first branch, “same invention” double patenting, prohibits the issuance of a second patent with claims that are “identical or coterminous” to the claims of a first patent. The second branch, “obviousness” or “obviousness-type” double patenting, prohibits the issuance of a second patent having claims that are not “patentably distinct” from the claims of a first patent. This second branch is aimed at preventing evergreening, that is, extending the monopoly granted by a first patent through the filling of successive patents claiming obvious variants of the first patent’s monopoly.

The Federal Court of Appeal in Mylan astutely points out that invalidity on the basis of obviousness-type double patenting is not the same as invalidity on the basis of obviousness under section 28.3 of the Patent Act (referred to as “traditional obviousness” in this article to avoid confusion). Different policy objectives underlie traditional obviousness and obviousness-type double patenting. Traditional obviousness is directed to the question of whether an “invention” (in the legal sense) exists at all, while obviousness-type double patenting is directed to preventing evergreening of an existing patent.

It follows that an obviousness-type double patenting analysis involves a comparison of the claims of a second patent against the claims of a first patent, whereas a traditional obviousness analysis involves a comparison of the claims of a single patent against the entirety of the prior art. The question that naturally arises from this distinction is what, if any, role does prior art play in an obviousness-type double patenting analysis? The Court inMylan presumptively settles this question, stating that:

[29]       In an obviousness challenge, any piece of prior art, including a collection of works, can be cited as rendering the impugned patent obvious and therefore not patentable: [Apotex Inc. v. Sanofi-Synthelabo Canada Inc.2008 SCC 61] at paras. 67-71. By contrast, in an obviousness-type double-patenting challenge, only the earlier patent can be cited as rendering the impugned patent not patentably distinct; any other prior art is only relevant insofar as it contributes to the common general knowledge of the skilled person.

Despite the Federal Court of Appeal’s best efforts, even this statement on the role of prior art gives rise to uncertainty. While it is clear that an obviousness-type double patenting analysis focuses on a comparison of the claims of the patents, it is unclear to what extent the disclosure of the earlier patent informs the assessment of whether or not the claims of the second patent are patentably distinct from the claims of the first patent.

The Federal Court of Appeal’s characterization of the earlier patent as “prior art” in an obviousness-type double patenting challenge suggests that the entirety of the earlier patent’s disclosure is relevant and can be relied on when assessing if the claims of the second patent are patentably distinct, as would be the case when considering any piece of “prior art” in the more common context for this term, traditional obviousness. Despite this characterization, the remainder of the Court’s decision in Mylan seems to suggest that importation of teachings from the disclosure of the first patent is inappropriate when considering whether or not the claims of the second patent are invalid for obviousness-type double patenting, at least in cases where the claims of the first patent are clear and unambiguous.

The Court in Mylan also considered the issue of the relevant date at which an obviousness-type double patenting analysis is to be assessed. Three possible dates were advanced. In chronological order, they were: (1) the priority date of the first patent, (2) the priority date of the second patent and (3) the publication date of the second patent. The Court in Mylan concluded it would be inappropriate to use any date after the claim date of the second patent, eliminating the third option but leaving the remaining two. Unfortunately, the Court in Mylanabstained from deciding further, leaving this issue unsettled for the time being.