Technical complexity a lion in the path of NEXIUM obviousness challenge

Om March 5, 2013, Justice O’Keefe of the Federal Court of Canada released Reasons for Judgment in a prohibition application involving Ranbaxy and Canadian Patent No. 2,170,647 listed against AstraZeneca’s esomeprazole product, NEXIUM.  In the proceeding, Ranbaxy had alleged that the relevant claims were invalid for obviousness.

The 647 Patent is generally directed to multiple unit tableted dosage formulations of esomeprazole and its racemate.  Unlike traditional enteric coated tablets, individually enteric coated pellets containing an acid sensitive drug, such as esomeprazole are compressed into tablet without significantly a affecting the properties of the enteric coating layer.


While there was no real dispute on the construction of the claims or what was disclosed in prior art disclosed that multiple unit dosage forms of omeprazole, the parties disputed whether the invention was attainable through the routine application of mechanical skill or would be surprising because of the various challenged in the process because of compression.

Justice O’Keefe, applying the obvious framework in Sanofi-Synthelabo concluded that the inventive concept of the claims was the formulation of a tablet of enteric coated pellets of omeprazole, whose pellets can retain their acid resistance after tablet compression. Justice O’Keefe held that experimentation was required to determine the appropriate composition of the enteric coating, including the amount of plasticizer, the quantity of coating agent, size of the sub unit, external additives, rate and magnitude of pressure applies during tableting to determined the most suitable composition.  Applying the “obvious to try” analysis from Sanofi-Synthelabo, Justice O’ Keefe held that given the unique manufacturing challenges in producing an enteric coating was not self evident  and,  relying in part on two articles published after the 1994 claim date, required a significant amount of effort:

[70] Mr. Justice Rothstein indicated that the invention must be self-evident from the prior art. In this case, the need for a solution is evident from the prior art; namely, an enteric coating suitable for dispersed omeprazole delivery, however, that solution is not provided for in the prior art. The prior art teaches away from the existence of such a solution or alternately indicates that such a solution is extremely complex and technically difficult to produce. Therefore, the enteric coating is not self-evident and so it is necessary to move on to the second stage of the “obvious to try” test.

[74] The nature of the effort required to achieve the invention was significant scientific research.  This is supported in both the applicants’ record (the 2011 article) as well as by Dr. Bodmeier’s affidavit. Presumably manufacturing and drug delivery technology have advanced between 1994 and 2011. It is therefore reasonable to presume that in 1994, development of such dosage forms remained at least an extremely complex process.

[75] It therefore follows that not only was the process extremely complex but it was also time consuming. The 1997 article by Dr. Bodmeier supports this position by identifying the numerous challenges that still needed to be overcome in producing tablets of coated pellets. The final paragraph of the article is most informative as it indicates that “…only [a] few studies have addressed the compaction of matrix-type pellets”.

 Justice O’Keefe concluded that while the prior art specifically provides a motivation to compress enteric coated pellets of omeprazole, the complex technological process of enteric coating pellets of omeprazole was a “lion in the path” significant enough to dissuade a person of skill in the art:

[86] Patentability is justified since the complexity and technical difficulty identified in the prior art would have dissuaded the hypothetical skilled person and, absent the work of the inventors, the development of an enteric coated pellet would have at least been delayed.

[87] Therefore, even if it was obvious to seek a solution for enteric coating for omeprazole, it was not an easy solution and would likely have dissuaded a person skilled in the art.

Concluding that Ranbaxy’s allegation of obviousness was not justified, Justice O’Keefe granted the prohibition Order preventing the Minister from approving Ranbaxy’s 20 and 40 mg esomeprazole tablets until the June 2105 expiry of the 647 Patent.

A copy of Justice O’Keefe’s Reasons for Judgment may be found here.