In Canada, the subject matter of a claim in a patent must not have been obvious having regard to the citable prior art and the common general knowledge.

Over the years, the test for obviousness in Canada has evolved into a step-by-step inquiry that now requires consideration, in at least some instances, of whether an invention was “obvious to try” to a skilled person at the claim date.

Whether an invention  claimed in a patent would have been “obvious to try” is an issue that is increasingly considered by Canadian courts in conducting an obviousness analysis. By way of example, of the 12 decisions issued by the Federal Court in 2014 in which obviousness of an invention was at issue, “obvious to try” was considered in 11 of these decisions. This article will address the factors that Canadian courts look to in assessing the issue and consider in what circumstances an “obvious to try” analysis is most relevant.

The Sanofi test and “obvious to try” considerations

The Supreme Court of Canada in Apotex v Sanofi-Synthelabo (“Sanofi”), 2008 SCC 61, outlined the following four-part test which must be considered when assessing whether a claim was obvious:

  1. Identify the notional “person skilled in the art” and 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 which would have been obvious to the person skilled in the art or do they require any degree of invention?

In the context of the fourth factor, the Court in Sanofi accepted that it may be appropriate in some cases to consider an “obvious to try” analysis. For a finding that an invention was “obvious to try”, there must be evidence to establish on a balance of probabilities that it was more or less self-evident to try to obtain the invention. The mere possibility that something might turn up is not sufficient. 

The Court in Sanofi listed the following non-exhaustive factors to be considered in an “obvious to try” analysis:

  1. Is it more or less self-evident that what is being tried ought to work? Are there a finite number of identifiable 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?
  3. Is there a motive provided in the prior art to find the solution the patent addresses?

The Court also acknowledged a fourth factor in the “obvious to try” analysis, namely the actual course of conduct culminating in the making of the invention (i.e., the invention history), in so far as it relates to how the skilled person would have acted in light of the prior art. 

Subsequent cases have applied the “obvious to try” test and expanded upon the Court’s language in Sanofi.

Self-evident threshold

It must be “very plain”, or self-evident, from the prior art and common general knowledge that what is being tested “ought to work”. Hindsight is to be avoided. An invention may be “obvious to try” if there are a finite number of possible routes that could be used to solve the problem. An invention that can only be reached when a skilled person makes a series of correct decisions is likely not self-evident or “obvious to try”.

Level of effort required

The Court is to consider the extent, nature and amount of effort required to achieve the invention, which is related to the actual course of conduct in making the invention or invention history (the “fourth factor” referred to above).

The mere fact that the invention may be achieved through routine testing does not necessarily render an invention “obvious to try”. However, an invention may be “obvious to try” if it was obvious to a skilled person to use routine, known tests in a manner that would lead to the invention. 

Regarding the actual course of conduct in making the invention, an invention that is reached quickly, easily and relatively inexpensively in light of the prior art and common general knowledge may be “obvious to try”. However, if the efforts involved went beyond mere “bench work” and a lot of time, money and effort were required to reach the solution, the invention may not be “obvious to try”.


A skilled person may be highly motivated to solve problems in the art. However, Canadian courts have stated that the focus should be on whether there is a “specific motivation” to pursue the invention – i.e. the particular solution taught by the patent. While a high degree of motivation will likely compel a skilled person to pursue experimentation that they view as “predictable” or having a “fair expectation of success”, motivation cannot transform a non-obvious invention into an obvious invention. Therefore, courts consider whether a skilled person is motivated enough to view the success of a particular solution as more or less self-evident and a set of experiments to achieve that solution as “obvious to try”.  

“Obvious to try” is not the same as “worth a try”

It should be noted that the “obvious to try” test is different from the “worth a try” test that has been used from time to time in other jurisdictions, such as in the United Kingdom. Obvious to try appears to be a higher standard. In Canada, a claimed invention will generally not be held obvious merely because it was “worth a try”.

When is an “obvious to try” analysis warranted?

The prevalence of “obvious to try” as an issue in many recent Canadian patent decisions is explained in part because many of these decisions relate to pharmaceuticals, an area of inventive activity in which advances are often made by experimentation. In such fields, there are many interrelated variables with which to experiment. Skilled persons are confronted with multiple routes to explore, with little knowledge about the success of each route. Such development work is relevant to an “obvious to try” analysis, where it would be appropriate to consider, from the standpoint of a skilled person, whether a particular approach would have been self-evident.

The Supreme Court of Canada has specifically stated that pharmaceutical inventions may warrant an “obvious to try” analysis. However, the Federal Court of Appeal has noted that the “obvious to try” approach should not be restricted to pharmaceutical inventions; instead, the applicability of an “obvious to try” analysis is dependent on the facts and evidence in each case.


It is important to note that whether or not a particular experiment was “obvious to try” comprises only one factor to assist in the obviousness inquiry. The overarching question when assessing obviousness is whether the claimed invention is obvious in light of the prior art and common general knowledge.