On Thursday, November 6, 2008, the Supreme Court of Canada released its much-anticipated decision in Sanofi-Synthelabo Canada Inc. v. Apotex Inc., 2008 SCC 61 (Sanofi). In this landmark decision, the Supreme Court gives considerable strength to pharmaceutical patents by rejecting Apotex’s generalized attack on selection patents as "evergreening" and holding that selection patents do not differ in nature from any other type of patent. The case is also significant because it adds important clarification to the test for anticipation and brings the law with respect to obviousness into closer alignment with that of the United States and United Kingdom.


The Sanofi case commenced as an application to the Federal Court of Canada brought pursuant to the Patented Medicines (Notice of Compliance) Regulations, in respect of the blockbuster drug PLAVIX (clopidogrel bisulfate). Sanofi is the holder of Canadian Patent No. 1,194,875. The '875 Patent contains "genus" claims that encompass about 250,000 compounds, including the racemate of clopidrogrel. A racemate is a substance containing equal amounts of two structurally different compounds called optical isomers. Although isomers share the same molecular formula, they can have very different properties. Significantly, the '875 Patent does not distinguish between the isomeric forms of clopidogrel — both are encompassed within the claims.

Sanofi subsequently discovered that a particular isomer of clopidogrel is less toxic and better tolerated than its other isomer. It is the beneficial isomer that was claimed in Canadian Patent No. 1,336,777.

Apotex challenged the validity of the '777 Patent on the grounds of anticipation, obviousness, and double patenting. Sanofi was successful at trial and on appeal. The Supreme Court also found in favour of Sanofi and dismissed Apotex’s appeal. As a result, the Minister of Health is prohibited from issuing regulatory approval to Apotex in respect of its clopidogrel product prior to the expiry of the '777 Patent.

The Decision

The Sanofi decision involves a so-called "old Act" patent. While the statutory law cited by the Court therefore comes from the Patent Act as it read pre-October 1989, the decision will undoubtedly have broad applicability even to so-called "new Act" patents.


Justice Rothstein (writing for the Court) relies heavily upon the House of Lords’ decision in Synthon BV v. Smithkline Beecham plc, [2005] UKHL 59, which articulates the two-step approach to the anticipation inquiry: "prior disclosure" and "enablement." This approach, which had already been applied in some cases in the lower courts, is now solidified in Canadian law.

For a claim of a selection patent to be anticipated, the first requirement is that the prior patent must disclose subject matter that, if performed, would necessarily result in the infringement of the subsequent patent. There is no room for trial and error or experimentation by the skilled person. If no such disclosure is apparent from reading the document, there is no anticipation. In the case of the '875 Patent, since it did not disclose the special advantages of the isomer claimed in the '777 Patent, the disclosure requirement was not met. It was not sufficient that the compound claimed in the selection patent was also encompassed within a claim in the '875 Patent.

If prior disclosure is found, the second requirement to prove anticipation is "enablement," which means that the skilled person would have been able to perform or work the invention of the new/selection patent as disclosed in the prior/genus patent in light of common general knowledge without "undue burden." For the enablement inquiry, the person skilled in the art may engage in some "routine" trial and error experiments in order to get the invention to work, but "prolonged and arduous trial and error experiments" are not permitted. The Court noted that the evidence in this case demonstrated that the identification of a particular isomer of clopidogrel and its advantageous properties required extensive investigation over a period of months, which suggested that such investigation would have constituted an undue burden for the skilled person (although a determination on this issue was not made, given the Court’s holding that the first part of the test was not met).


The key issue in Sanofi was whether the law of obviousness in Canada should be brought more in line with jurisprudence in the United States and United Kingdom, both of which accept that the "obvious to try" test can be relevant in an obviousness inquiry (most recently in KSR International Co. v. Teleflex Inc., 127 S.Ct. 1727). The Court agreed it was time to incorporate an "obvious to try" test into Canadian law. However, it said that such a test was only one factor to consider and, importantly, that it "will work only where it is very plain or … more or less self-evident that what is being tested ought to work." The mere possibility that "something might turn up" in the experiment is not sufficient to meet the obvious to try test.

Justice Rothstein sets out a four-step approach for assessing an allegation of obviousness:

  1. (a) Identify the notional "person skilled in the art." (b) Identify the relevant common general knowledge of that person.
  2. Identify the inventive concept of the claim in question or, if that cannot readily be done, construe it.
  3. Identify what, if any, differences exist between the matter cited as forming part of the "state of the art" and the inventive concept of the claim, or the claim as construed.
  4. Viewed without any knowledge of the alleged invention as claimed, do those differences constitute steps that would have been obvious to the person skilled in the art or do they require any degree of invention?

It is in the fourth step that the issue of obvious to try will arise (although it is only a factor to consider). In this respect, Justice Rothstein observed that the obvious to try test may only be appropriate in cases where advances are won by experimentation. In such cases, he held that the following factors should be considered:

  1. Is it more or less self-evident that what is being tried ought to work? Are there a finite number of identified predictable solutions known to persons skilled in the art?
  2. What is the extent, nature and amount of effort required to achieve the invention? Are routine trials carried out or is the experimentation prolonged and arduous, such that the trials would not be considered routine? On this issue, the Court suggested that evidence about the actual course of conduct in reaching the invention might be useful (was it relatively straightforward or costly and time-consuming?).
  3. Is there a motive provided in the prior art to find the solution the patent addresses?

The evidence in Sanofi was that there were just five methods that might be used to isolate the particular isomer of clopidogrel that was the subject of the '777 Patent, that all steps to test the isomers used to identify their benefits were known, and that there was a motivation to find compounds with the benefits disclosed in the '777 Patent. Importantly, Justice Rothstein held that just because there are known methods of separating the isomers, that "does not mean that a person skilled in the art would necessarily apply them." Justice Rothstein also held that nothing in the earlier patent or common general knowledge provided a specific motivation for the skilled person to pursue the invention of the selection patent. Although it was known that the properties of a racemate and its isomers may be different, it was not known what they would be or what these differences were. The possibility of finding the invention is not enough. The specific invention must be "self-evident" before the attempt is made. Justice Rothstein also observed that it took over a year for Sanofi to find the invention after spending millions of dollars developing the racemate without even exploring the possibility that a particular isomer would be superior. In light of these factors, the Court found that the invention claimed in the selection patent was not self-evident or obvious from the prior art and common general knowledge.

Double Patenting

Justice Rothstein reaffirmed the approach articulated by Justice Binnie in Whirlpool Corp. v. Camco Inc., [2000] 2 S.C.R. 1067 to the prohibition against double patenting, which will invalidate a second patent covering the same invention as the first. There are two types of double patenting: (1) coterminous double patenting, and (2) obviousness-type double patenting.

The justification for imposing the prohibition against double patenting is to prevent evergreening. However, Justice Rothstein stated that "a generalized concern about evergreening is not a justification for an attack on the doctrine of selection patents."

Justice Rothstein held that the invention claimed in the two patents was not the same, even though the same clopidogrel isomer claimed in the selection patent was also encompassed within the claims of the '875 Patent. The breadth of the invention claimed in the previous patent was larger than the breadth of the invention claimed in the selection patent, and the particular isomer claimed in the selection patent had beneficial and non-obvious properties over those compounds claimed in the prior patent.


This decision is an important victory for patentees in Canada. According to the evidence in the case, about eight out of every 10 pharmaceuticals currently on the market involve selection patents. It is important that financial incentives are available to drug researchers to continue searching for new and better drugs, and this decision decisively confirms that protection for such innovation is available in Canada. In dismissing Apotex’s appeal, the Court clearly held that selection patents in Canada are valid in principle.

Moreover, the Court articulated a clear test for anticipation and obviousness that should present serious obstacles for validity challenges in view of how those tests were considered and applied to the facts of this case.

Finally, this decision demonstrates the Court’s willingness to revamp Canadian patent law by taking into account foreign jurisprudence to a degree never before witnessed in other Supreme Court decisions involving patents. Notably, the "worth a try" test, previously discredited by lower courts as a consideration in the obviousness inquiry, was incorporated into Canadian law in part based on the confluence of the law in the United States and the United Kingdom. That approach points towards potential further harmonization of Canadian law as further issues of patent law come before the Court.