Only a true invention can be patented; a patent claim to an invention is not valid if the invention was obvious. Assessing obviousness can be thought of as bridging the gap between two cliffs: on one side is the existing state of the art and on the other, the “inventive concept”. If a skilled person would have found bridging the gap obvious, or obvious to try, then there was no invention. Litigants have debated the rigidity and rigour of the "obvious to try" approach to assess inventiveness. Although often automatically applied in “unpredictable arts” such as biotech and pharma, there is no strict rule that the "obvious to try" approach must be used, or that when it is used it must follow a particular test. The Federal Court of Appeal has now articulated the inventive concept as the solution the patent teaches. Accordingly, the way the gap is bridged—the obviousness assessment—is flexible. But defining the inventive concept—the cliff at the other side of the gap—is not. And its precise margins often determine the result.


Bristol-Myers Squibb Canada Co. v. Teva Canada Limited, 2017 FCA 76 - 2017-04-11

IP Type

Patents (pharma)


Atazanavir is a drug used to treat HIV and AIDS. Bristol-Meyers Squibb (BMS) obtained a patent claiming a particular salt form of atazanavir (atazanavir bisulfate) that was particularly well absorbed by the body. Teva challenged the validity of that claim.

The Federal Court was convinced by Teva's allegation that the patent was invalid because the invention was not inventive; it was obvious. The Court defined the inventive concept to include the special properties of atazanavir bisulfate, including improved bioavailability, a particular crystal structure, and improved stability.

The Court applied the "obvious to try" test articulated by the Supreme Court, one prong of which asks "[i]s it more or less self-evident that what is being tried ought to work?" The Federal Court limited the role of unpredictability in the assessment, finding in the law no “proposition that in every case where a skilled person cannot predict the properties of a compound in advance of making it, it will not be obvious to try to obtain that compound."

The Court found that in the development process, BMS’ personnel arrived at atazanavir bisulfate quickly and easily and the improved bioavailability was obvious. By contrast, the other parts of the inventive concept, the particular crystalline form and the stability of the compound, were not predictable without first making and testing the compound. Nevertheless, invention was obvious.

BMS appealed, arguing that the Federal Court had erred in applying the "obvious to try test" by finding the claimed compound obvious despite uncontradicted evidence that two elements of the invention—crystallinity and stability—were not predictable.

The Federal Court of Appeal dismissed the appeal, remaining convinced by the obviousness allegation, but for different reasons. In so doing, the Court:

  • noted the “obvious to try” test did not apply automatically and had not displaced all other inquiries into obviousness;

  • rejected a categorical approach to obviousness, including any hard and fast rule that obviousness cannot be shown unless all the elements can be predicted with a high degree of certainty; and

  • identified the inventive concept as being the solution the patent teaches.

In the end, the first-instance error did not reside in the application of the obvious to try test, but rather in the identification of the inventive concept. The correct inventive concept was the solution taught by the patent: simply "atazanavir bisulfate, a salt of atazanavir which is pharmaceutically acceptable because it has equal or better bioavailability than the atazanavir free base" but without regard to its crystalline and stability properties.

With the proper inventive concept defined, there was no inventive step separating the solution taught in the prior art from the claimed invention, regardless of whether the “obvious to try” test had been applied.