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Proper date for assessing double patenting is the priority date of the earlier patent – Federal Court

On January 7, 2015, Justice De Montigny released the public Judgment and Reasons in a prohibition application under the Patented Medicines (Notice of Compliance) Regulations between Eli Lilly and Mylan in respect of Mylan’s proposed tadalafil tablets. Justice de Montigny concluded that the Eli Lilly had demonstrated that none of Mylan’s allegations of invalidity were justified and prohibited the Minster of Health from approving Mylan’s tadalafil product until the expiry of Canadian Patent No. 2,226,784.

784 Patent

The 784 Patent is generally directed to the use of tadalafil (or methyltadalafil) for the treatment of erectile dysfunction in a male animal, including in humans. The 784 Patent discloses that tadalafil was a potent inhibitor of the PDE V enzyme in vitro and in rat aortic smooth muscle cells but does not disclose the results of any in vivo testing.

Mylan had alleged that the 784 Patent was invalid on the basis of lack of utility and double patenting.

Promise of the Patent

The issue of utility largely turned on the Court’s construction of the promise of the patent. Whereas Lilly proposed that patent promises the effectiveness of compounds to treat erectile dysfunction, Mylan argued for a more exacting promise, specifically that the compounds must be effective on oral administration and must not have severe side effects. Justice de Montigny preferred Lilly’s construction noting that oral administration was the “preferred” but not sole route of administration contemplated by the 784 Patent and that none of the experts went so far to opine that the promise requires efficacy without undue side effects.  Mylan’s proposed promise was clearly a case where the promise was expanded in order to argue that it was not met.

 Sound prediction

As there was no evidence that any of the claimed compounds had been tested in vivo prior to the filing of the 784 Patent, the utility of the claims must have been based on a sound prediction. Justice de Montigny concluded that the utility of the claims could not have been soundly predicted based on preliminary experiments on tadalafil and methyltadalafil performed at Glaxo because none of these results were disclosed to the public before the patent filing date. However, relying a published study showing sildenafil, another selective PDE-V inhibitor, was effective in orally treating erectile dysfunction, Justice de Montigny held that the the promised utility of the 784 Patent, whether construed as including or excluding oral administration, was soundly predicted.

Double Patenting

Mylan argued that if the promise does not include oral administration, the 784 Patent was invalid for obviousness-type double patenting in light of Canadian Patent No. 2,181,377, disclosing that tadalafil is a potent and selective inhibitor of the enzyme PDE-V.  Justice de Montigny rejected Lilly’s argument that since the claims of the 377 Patent do not include PDE-V inhibition there was no nexus to the invention claimed in the 784 Patent. Rather, Justice de Montigny construed the claims of the 377 Patent, in light of the specification as a whole, as directed to tadalafil as a PDE-V inhibitor.

Double Patenting – Relevant Date

The proper date for determining double patenting was an issue between the parties. Justice de Montigny rejected Mylan’s submission that the proper date is the priority date of the second patent, noting that this would morph the analysis into a pure obviousness analysis unfettered by the timing requirements for citable prior art. Rather, the relevant date was the priority date of the earlier patent and that the Court must ascertain whether the invention claimed in the later patent could or should have been included in the earlier one. Applying this date, the Court held that it would not have been obvious to use tadalafil for the treatment of erectile dysfunction.

A copy of Justice de Montigny’s Judgment and Reasons may be found here.