Last year we wrote about a trilogy of Federal Court decisions relating to Eli Lilly’s erectile dysfunction (ED) drug CIALIS® (tadalafil). While Lilly was successful in obtaining a prohibition order in the first proceeding, its latter two applications were dismissed. Mylan appealed the first order, and the Federal Court of Appeal (FCA) recently released its decision in Mylan Pharmaceuticals ULC v. Eli Lilly Canada Inc., 2016 FCA 119 dismissing Mylan’s appeal.

The FCA’s decision affirms the view that obviousness and obviousness-type double patenting validity challenges require distinct analyses, and that a patent’s disclosure cannot be referenced to vary the scope or ambit of its claims where those claims are unambiguous.

In the hearing below, Mylan alleged that Lilly’s ‘784 Patent was invalid on the basis of, among other grounds, obviousness-type double patenting over Lilly’s earlier ‘377 Patent. The earlier patent claimed the compound tadalafil, while the later patent claimed tadalafil for the treatment of ED.

In the decision below, Justice de Montigny construed the claims of the earlier patent in light of the patent as a whole to conclude that it claimed tadalafil as a PDE V inhibitor, but did not claim or contemplate its use for the treatment of ED. He held that Mylan’s allegation of obviousness-type double patenting was unjustified, as Lilly’s ‘784 Patent was patentably distinct from the earlier patent:

Although both are claims for the same chemical compound, tadalafil, they are claims for different uses of this compound. The ‘377 Patent does not contemplate the use of tadalafil to treat ED; rather, this is precisely the monopoly claimed in the ‘784 Patent. As Lilly notes, when the ‘377 Patent expires, the public will be free to use tadalafil for the uses claimed in the ‘377 Patent. Therefore, the claims are patentably distinct.

On appeal, the FCA distinguished obviousness-type double patenting from obviousness. According to the FCA, obviousness asks whether a legal “invention” exists in light of all of the relevant prior art. By contrast, obviousness-type double patenting asks whether there is an inventive step from an earlier patent to a later one. The focus is whether the second patent contains an inventive element beyond that claimed in the first which makes it “patentably distinct”.

In the present case, the FCA held that Lilly’s earlier ‘377 Patent claimed tadalafil, but its status as a PDE V inhibitor was evidenced only by the disclosure of the patent, not by its claims. The FCA held that Justice de Montigny erred by interpreting the ‘377 Patent as claiming tadalafil as a PDE V inhibitor, because its status as such was only made clear in the disclosure of the patent, not its claims:

In my view, the judge erred in referring to the specification when construing the claims of the ‘377 patent. The rules of patent construction preclude reference to the specification when the claims are clear, and improper if reference varies the scope of the claims. […]

To conclude, as there was no ambiguity in the claims here, there could be no recourse to the specification.

However, the FCA acknowledge that the effect of the trial judge’s construction was to impose a higher burden on Lilly in terms of overcoming the obviousness-type double patenting allegation; by focusing on the functionality of the compound claimed in the earlier patent, the inventive “gap” between the two patents was effectively narrowed. As such, while the FCA held that Justice de Montigny erred in his construction, his conclusion that the ‘784 Patent was patentably distinct was correct.

The FCA’s decision calls into question the relevance of a patent’s disclosure when it comes to understanding a patent’s claims where those claims are not ambiguous. While it is well-established that a patent’s disclosure cannot be referenced to vary the scope or ambit of its claims, the Supreme Court of Canada has cautioned that claim terms must be read in context, and that it is unsafe to conclude that a term is plain and unambiguous without a careful review of the patent as a whole. In Whirlpool Corp. v. Camco Inc., 2000 SCC 67, Justice Binnie noted that “it was perfectly permissible for the trial judge to look at the rest of the specification, including the drawing, to understand what was meant […] in the claims, but not to enlarge or contract the scope of the claim as written and thus understood”.

It will be interesting to watch how this most recent pronouncement from the FCA on patent claims construction will be interpreted in future decisions.