Canada: Pharma In brief - Canada: Patent For Esomeprazole Tablets Found Not To Be Obvious

Case: AstraZeneca Canada Inc. and AstraZeneca AB v. Ranbaxy Pharmaceuticals Canada Inc. and the Minister of Health

Drug: Esomeprazole (NEXIUM®)

Nature of case: Prohibition proceeding pursuant to PM(NOC) Regulations

Successful party: AstraZeneca Canada Inc. and AstraZeneca AB

Date of decision: March 5, 2013


AstraZeneca Canada Inc. and AstraZeneca AB ("AstraZeneca") brought an application pursuant to section 6 of the Patented Medicines (Notice of Compliance) Regulations for an order prohibiting the Minister of Health from issuing a Notice of Compliance to Ranbaxy Pharmaceuticals Canada Inc. ("Ranbaxy") for enteric coated pellets of esomeprazole in 20 mg and 40 mg strengths until the expiry of Canadian Patent No. 2,170,647 (the "'647 Patent").

The only issue before the Court was whether Ranbaxy's allegation of invalidity based on obviousness was justified. AstraZeneca argued that the '647 Patent made possible for the first time a multiple unit tablet dosage formulation of an acid sensitive drug, esomeprazole, and that there was nothing in the prior art indicating that such a creation was obvious.  The Court agreed with AstraZeneca and held that Ranbaxy's allegation that the '647 Patent was invalid for obviousness was not justified.  Accordingly, the Court granted AstraZeneca's application for a prohibition order.

The '647 Patent

The '647 patent application was filed on June 7, 1995, and claims priority from an application filed in Sweden on July 8, 1994. The '647 patent was published on January 25, 1998 and expires on June 7, 2015. It is entitled "Multiple Unit Tableted Dosage Form I" and includes 40 claims. All of the claims impugned by Ranbaxy in the proceeding relate to tableted dosage forms of omeprazole, S-omeprazole, or alkaline salts thereof.


The Court applied the four-step guide for assessing obviousness as laid out by the Supreme Court of Canada in Apotex Inc. v. Sanofi-Synthelabo Canada Inc [Sanofi].

(i) The State of the Art and Common General Knowledge

The parties were in general agreement regarding the state of the art and common general knowledge of the skilled person. The parties agreed that the notional person skilled in the art was "a pharmaceutical formulator, with a Bachelor's degree in pharmaceutics or a related science and at least two or three years of experience in formulation development, including some exposure to delayed and controlled release formulations and the associated general knowledge."  

(ii) The Inventive Concept

The parties were also in general agreement on the construction of the claims of the '647 Patent.  The Court determined that the inventive concept of the '647 patent, as understood by the skilled person, was the formulation of a tablet of enteric coated pellets of esomeprazole, which can retain their acid resistance after tablet compression.

(iii) Difference between the Prior Art and Inventive Concept

Ranbaxy argued that the only difference between the state of the art and the inventive concept in the '647 Patent was the actual making of the multiple unit tableted enteric coated dosage form of esomeprazole.  AstraZeneca argued that this very difference was the inventive step.  The Court held that the parties were making a distinction that was best addressed in the context of the fourth factor of the Sanofi test.

(iv) Obvious to Try

The Court held that at the fourth stage it was necessary to consider the "obvious to try" test since "experimentation was required" to determine the appropriate composition of enteric coating.  The Court noted that "'[o]bvious to try' does not mean 'worth a try', but obvious in the sense of 'very plain' or 'more or less self-evident'".

More or less self evident – The Court found that the solutions arrived at in the '647 Patent would not have been self-evident to a person skilled in the art at the relevant time.  The Court agreed with AstraZeneca that producing an enteric coating presented complex and unique challenges from a manufacturing perspective.  While the need for such a solution was evident from the state of the art, the Court held that the prior art taught away from the solution the patent addressed or alternatively that the prior art taught that such a solution was complex and technically difficult to produce.

Extent, nature and effort required to achieve the invention – Regarding the extent, nature and effort required to achieve the invention, the Court preferred the testimony of AstraZeneca's expert to that of Ranbaxy's expert.  The evidence showed that the process for developing suitable enteric coating for pellets was highly complex and time consuming. The Court noted that only a small number of tablets had reached market with such a coating formulation.

Motivation – The Court agreed with Ranbaxy's position that there was a motive provided in the prior art to find the solution the patent addresses.  However, the Court held that strong motivation to produce a comparable or better product is a positive factor in considering the "obvious to try" test: "If other parties were motivated to find the solution and yet were unable or unwilling to do so prior to the patent being obtained, this factor would point to a solution that was not 'obvious to try'."  In this case, while the prior art did in fact provide motivation to find the solution in the '647 Patent, the Court held that there remained a "lion in the path" significant enough to dissuade the person skilled in the art from pursuing the solution addressed.


For the reasons above, the Court held that Ranbaxy's allegation of invalidity was not justified.  As such, the Court granted AstraZeneca's application for an order prohibiting the Minister of Health from issuing a notice of compliance for the Ranbaxy tablets in 20 mg and 40 mg strengths until the expiry of the '647 patent.

Link to decision:

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