A Purposive Interpretation of the Promise of the Patent

Astrazeneca Canada Inc v Mylan Pharmaceuticals ULC / anastrozole (NOC) 2012 FCA 109 Evans JA: Sharlow, Dawson JJA aff’g 2011 FC 1023 Rennie J

After the shocking decision in Pfizer v Apotex / latanoprost (NOC) 2011 FCA 236, blogged here, this brief decision of the FCA in Astrazeneca v Mylan / anastrozole (NOC), is the second FCA decision in a row to adopt a moderate approach to interpreting the promise of the patent, coming close on the heels of Mylan v Pfizer / donepezil (NOC) 2012 FCA 103 (blogged here). Whether this marks a trend, or a split in the Court, remains to be seen.

In the decision under appeal, blogged here, Rennie J developed a principled approach to construing the promise of the patent by considering text, context and purpose. While the FCA did not specifically hold that this approach was required, as Mylan did not contest Rennie J’s interpretive framework [21], the FCA decision considered much the same factors as did Rennie J, and in a similarly holistic fashion. This may be simply because Rennie J’s decision shaped the points argued on appeal, but nonetheless, in tenor the FCA decision provides an endorsement of Rennie J’s framework. The appeal turned primarily on the interpretation of a sentence stating that it is “a particular object of the present invention to provide” compounds with fewer undesirable side effects than a prior art compound, aminogluthethimide (AG) [8]. Mylan invited the Court to interpret this as being determinative of the promise. The Court rejected this “microscopic” approach to the promise as “misguided” [32]. This is in contrast to the latanoprost decision, 2011 FCA 236, in which a somewhat differently constituted panel (Sharlow JA was on both) focused microscopically on the fact that the claimed invention was intended to treat a chronic disease.

The FCA anastrozole decision also has some very interesting dicta that further suggests a principled shift in the approach to the promise of the patent. At the outset the Court noted that the invention met the minimum threshold required for utility, and was therefore patentable as of the filing date, unless the patent promised more than the required minimum [7]. The Court subsequently noted at [30] that

it is agreed that the 420 patent would be valid if it only claimed the compound anastrozole and its inhibitory effects on aromatase. It was thus unnecessary for the patent also to promise fewer side effects than AG. Even though tests, which AstraZeneca did not disclose, had been conducted showing that anastrozole was selective, a promise in the patent to this effect would be entirely gratuitous, and could only provide competitors with another basis for attacking its validity.

Similarly, at [37]

even if anastrozole would not be commercially or clinically useful if it produced no fewer side effects than AG, it is agreed that it was patentable as a novel and useful compound, and as an aromatase inhibitor. It would be rational to seek patent protection for anastrozole on this basis, in case it turned out to be selective. . .

This suggests, in effect, that if an inventor has in fact invented and disclosed a patentable invention, she should be presumed to want a valid patent for it. As I have argued elsewhere, this accords both with common sense, and with a purposive approach to patent interpretation. As the SCC has said, “the guiding principle” of purposive construction is that “where the language of the specification, upon a reasonable view of it, can be so read as to afford the inventor protection for that which he has actually in good faith invented, the court, as a rule, will endeavour to give effect to that construction." (Consolboard [1981] 1 SCR 504 at 521, quoting Western Electric v Baldwin Int’l Radio [1934] SCR 570 at 574). If taken to its logical conclusion, this implies that a patentee should never be presumed to promise more than the minimum scintilla of utility required to sustain a valid patent. If that presumption were determinative, the entire promise of the patent doctrine would collapse. However, that presumption of purpose is not determinative within the framework articulated by Rennie J, because text and context must also be considered. It is nonetheless a powerful point in favour of construing the promise of the patent minimally.