A Limit on the Windsurfing / Pozzoli Obviousness Framework in Pharmaceutical Cases

Astrazeneca Canada Inc. v. Mylan Pharmaceuticals ULC / anastrozole (NOC) 2011 FC 1023 Rennie J

The four-step Windsurfing/ Pozzoli approach to the obviousness determination, endorsed by the Supreme Court in Sanofi 2008 SCC 61 at [67], is now routinely used, but it is no more than a framework that need not, and should not, be used when it is not helpful: Sanofi [61], [63]; Weatherford 2011 FCA 228 [67]. Astrazeneca / anastrozole (NOC) illustrates one context in which the limits of the Pozzoli framework are reached. As is common, the claimed compound, anastrozole, was developed by modifying a lead compound in an attempt to improve its properties. Rennie J held that there was no obvious lead compound, and that was sufficient reason to find that the invention was not obvious, whether or not the subsequent modifications were obvious [214]. If indeed the selection of the lead compound is not obvious, the non-obviousness of the claimed invention follows, whether or not the lead compound is part of the prior art. (Note that the non-obviousness conclusion was supported by compelling secondary evidence [221]-[227]).

Accepting that the choice of the lead compound may itself constitute the inventive step necessary to support the patent, consider the difficulty in applying the Pozzoli framework, which requires an inquiry as to whether the differences between the state of the art and the claimed invention are obvious. The differences between a prior art lead compound and the claimed invention may be obvious, if the modifications are routine, and yet the claimed invention may be non-obvious if the selection of the lead compound is itself non-obvious. By focussing on differences between the state of the art and the claimed invention, the Pozzoli framework begs the question of whether the selection of the lead compound supplies the inventive step. Taking the selection of the lead compound as given, simply because it is part of the prior art, would constitute impermissible hindsight. Accordingly, while Rennie J cited the Pozzoli framework at [193], he did not apply it in coming to his conclusion on obviousness. While failure to apply the Pozzoli framework is never in itself an error of law, in the circumstances of the anastrozole decision, avoiding the Pozzoli framework actually facilitated a correct analysis of the obviousness question. To be sure, it might be possible to apply the Pozzoli framework even in this context, for example by defining the state of the art as encompassing only those compounds which are promising lead candidates, but this is artificial, as it pushes the key obviousness inquiry into the third stage identification of the state of the art, where the Pozzoli framework contemplates that this inquiry is undertaken in the fourth stage. It is therefore preferable simply to recognize the limitations of the Pozzoli framework.