As discussed in our previous article, entitled “Obviousness double patenting in Canada not so obvious”, the Federal Court of Appeal in Mylan Pharmaceuticals ULC v. Eli Lilly Canada Inc. et al., 2016 FCA 119 (“Mylan”), confronted the difficult doctrine of obviousness-type double patenting in Canada. Unfortunately, the Court also advanced a worrisome proposition in their discussion of the interrelated issue of claim construction.

The patent at issue in Mylan 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. Mylan appealed a previous decision of the Federal Court, 2015 FC 17, which granted an order prohibiting a Notice of Compliance from being issued to Mylan, thus preventing Mylan from marketing a generic version of tadalafil until the expiry of the ‘784 Patent. During the appeal, Mylan alleged that the ‘784 Patent was invalid on the basis of obviousness-type double patenting, inter alia.

It is well established under Canadian patent law that an obviousness-type double patenting analysis involves a comparison of the claims of a second patent against the claims of a first patent (Whirlpool Corp. v. Camco Inc., 2000 SCC 67 (“Whirlpool”)). This analysis necessarily requires the claims of both patents to be construed.

While construing the claims in Mylan, the Federal Court of Appeal stated “[t]he rules of patent construction preclude reference to the specification when the claims are clear” and “as there was no ambiguity in the claims here, there could be no recourse to the specification” [Emphasis added]. Although Canadian jurisprudence dating as far back as 1982 recognizes that recourse to the remainder of the specification is “unnecessary where the words of the claim are plain and unambiguous” (Beecham Canada Ltd. et al. v. Procter & Gamble Co., [1982] F.C.J. No. 10 (F.C.A.)), the statements of the Federal Court of Appeal in Mylan take this established proposition to a troubling extreme.

In the seminal case of Whirlpool, the Supreme Court of Canada reiterated a caution that “[t]erms must be read in context, and it is therefore unsafe in many instances to conclude that a term is plain and unambiguous without a careful review of the specification” and went on to find that it was “perfectly permissible” for the trial judge to look at the specification, including drawings, to determine what was meant by a particular word in the claims. This caution is well founded.

Precluding reference to the specification based on an assertion that the claims are plain and unambiguous is a precarious practice that is prone to inconsistencies. Such inconsistencies are exemplified in Mylan, where the Federal Court of Appeal found the claims to be “clear” and unambiguous but then came to a different construction for the claims than that of the trial judge, who relied on reference to the specification.