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Federal Court of Appeal issues another decision dealing with “promise of the patent” [ARIMIDEX/anastrozole]

On April 11, 2012, the Federal Court of Appeal dismissed Mylan’s appeal of a decision of Justice Rennie (2011 FC 1023) which granted AstraZeneca a prohibition order in respect of its drug ARIMIDEX.

The singular issue at play on appeal was the proper construction of the “promise of the patent”. The two claims of Canadian Patent No. 1,337,420 at issue were claims 14 (pharmaceutical composition) and 15 (use of anastrozole as an inhibitor of the aromatase enzyme).  The construction of these claims was not in dispute.  Rather the inquiry hinged on whether the following sentence in the description was a “promise” or merely an “object” of the invention:

It is a particular object of the present invention to provide aromatase inhibitory compounds with fewer undesirable side effects than aminogluthethimide.

Mylan argued that this sentence promised fewer side effects and that this was neither demonstrated nor soundly predicted.  AstraZeneca argued that this was a “forward-looking or aspirational aim” of the invention and not a promise (AstraZeneca also argued in the alternative that if this statement amounted to a promise, that it had been demonstrated as of the relevant date).

In support of its argument, Mylan alleged several errors on the part of the hearing judge, all of which were rejected.  The Federal Court of Appeal held that the judge had not placed undue reliance on the dictionary definition of “object”, properly construed the phrase in the context of the entire patent and committed no palpable and overriding error in assessing the expert evidence.

A copy of the decision can be found here.