A minor claim construction issue that arose in AstraZeneca Canada Inc. v. Apotex Inc., 2010 FC 714 highlights the need for clarity in claim drafting. While the specific example here is unlikely to often apply, the general principle does. Ensure consistent language between your claims and your specification.
The claim at issue was for a salt of the (-) enantiomer of omeprazole at 99.8% optical purity. A question arose during construction of whether this percentage meant
- enantiomeric excess (ee), the percentage of (-) enantiomer relative to the % of (+) enantiomer; or
- absolute purity, the percentage of the (-) enantiomer with respect to the entire sample.
AstraZeneca argued that ee was used in specification, therefore one skilled in art would interpret range in claims as also being expressed as ee. Apotex argued that as ee was used in the specification, but was not used in the claim, there was a clear choice to claim in terms of absolute purity and not ee.
J. Hughes held in AstraZeneca’s favour. 99.8% in claim language was interpreted to be a measure of enantiomeric excess.
By James Wagner