Pharma in brief - Canada: Federal Court of Appeal upholds compound claim based on a promise of enzymatic inhibition [ARIMIDEX® (anastrozole)]
May 2012

Case: Mylan Pharmaceuticals ULC v. AstraZeneca Canada Inc.

Drug: Anastrozole

Nature of case: Appeal from an order of prohibition under s. 6 of the PM(NOC) Regulations

Successful party: AstraZeneca Canada Inc.

Date of decision: April 11, 2012

Summary

On April 11, 2012, the Federal Court of Appeal (“Court of Appeal”) dismissed an appeal by Mylan Pharmaceuticals ULC (“Mylan”) from a decision of Justice Rennie granting to AstraZeneca Canada Inc. and AstraZeneca UK Limited (“AstraZeneca”) an Order of Prohibition under section 6 of the Patented Medicines (Notice of Compliance) Regulations in respect of the medicine anastrozole and Canadian Patent No. 1,337,420 (the “’420 patent”).

The ‘420 Patent

Anastrozole is used for the treatment of forms of breast cancer that depend on estrogen for their growth. The ‘420 Patent specification states that the “invention relates to (substituted-aralkyl) – heterocyclic compounds, and in particular relates to compounds which are useful as inhibitors of the enzyme aromatase.”

In its Notice of Allegation, Mylan alleged that its sale of a generic version of anastrozole would not infringe the ‘420 Patent because the patent was invalid for lack of utility and obviousness. The main issue in dispute related to the promised utility of the patented invention and the construction of a particular statement in the specification:

A variety of compounds possessing aromatase inhibitory activity is known, of which the most important clinically is aminogluthethimide [AG]. [AG], however, has the drawback that it affects other aspects of steroid metabolism, with the consequence that its use is often associated with undesirable side-effects. It is a particular object of the present invention to provide aromatase inhibitory compounds with fewer undesirable side effects than [AG].

Mylan argued that the underlined sentence (the “Object Statement”) constitutes a promise that anastrozole has fewer undesirable side effects than AG, the first aromatase inhibitor to be used in the treatment of breast cancer. AstraZeneca argued, on the other hand, that the Object Statement was merely a forward-looking or aspirational aim of the invention and that the promise of the patent was enzyme inhibition.

Federal Court Decision

Justice Rennie agreed with AstraZeneca’s construction and held that the promise of the patent was enzyme inhibition.  The Object Statement was simply a forward-looking or aspirational aim of the invention. It was not a promise that anastrozole had achieved this goal by the date of filing.  Justice Rennie also rejected Mylan’s arguments regarding obviousness.  A summary of the Federal Court judgment is provided in a previously issued Pharma in Brief.

Federal Court of Appeal Decision

Mylan appealed Justice Rennie’s findings regarding promise and utility.  The Court of Appeal reviewed the construction of the patent on a standard of correctness and held that Justice Rennie did not err in his assessment of the promise and utility.  In dismissing Mylan’s appeal, the Court of Appeal made the following findings:

1. Patents are not required to contain a clause describing the object of the invention.  However, if they do contain such a clause, the meaning of that clause (i.e. whether it is a ‘promise’) depends on the specific factual context, including the wording of the clause itself and its relationship with the rest of the patent.
2. An examination of the patent in its entirety supported the conclusion that, unlike the express claims of the ‘420 Patent, the Object Statement was no more than a forward-looking aim of the invention. The fact that side-effects were not mentioned elsewhere in the ‘420 Patent was telling.
3. The state of scientific knowledge at the Canadian filing date is an important aspect of the context in which a patent must be construed.  It is possible to read an object clause as stating that its aim to is to solve a problem known in the pharmaceutical industry without promising success.
4. The subjective intention of the inventor counts for relatively little in construing the provisions of a patent. It was open to the Judge to base his findings regarding the meaning of the Object Statement on particular expert testimony.
5. Justice Rennie did not err in inferring from the absence in the patent of any description of clinical trials that the patent could not be promising something only demonstrable through clinical trials.  

Link to decisions:

Federal Court of Appeal: Mylan Pharmaceuticals ULC v. AstraZeneca Canada Inc., 2012 FCA 109

Federal Court: AstraZeneca Canada Inc. v. Mylan Pharmaceuticals ULC, 2011 FC 1023

Also written by Arjeta Mereri, Lawyer in the Toronto Intellectual Property Group

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