Case: AstraZeneca Canada Inc. et .al.  v. Mylan Pharmaceuticals ULC

Drug: Anastrozole  (ARIMIDEX®)

Nature of case: Section 6 prohibition - Patented Medicines (Notice of Compliance) Regulations

Successful party: AstraZeneca Canada Inc.

Date of decision: August 29, 2011


On August 29, 2011 the Federal Court allowed an application by AstraZeneca Canada Inc. and AstraZeneca UK Limited (collectively “AstraZeneca”) 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 Mylan Pharmaceuticals ULC (“Mylan”) in respect of its generic version of the drug anastrozole until after the expiry of Canadian Patent No. 1,337,420 (the “’420 Patent”).

Mylan asserted in its Notice of Allegation that the relevant claims of the ‘420 Patent were invalid for lack of utility and obviousness.


The Court held that the patent promised utility as an aromatase inhibitor and nothing more. It found that in contrast to other cases, the patent at issue contained no clear and specific language amounting to a promise of therapeutic utility. While the patent at issue disclosed that aromatase inhibition can be used in the treatment of breast cancer, the Court refused to read an explicit promise of therapeutic utility into such statements.

The Court re-iterated many canons of claim construction including that the promise “must ultimately be grounded in the language of the patent specification” and “where a reasonable reading of the patent specification can be read to protect a good invention, the Court should give effect to that construction.”

The Court interpreted the references in the patent to reduced side effects as expressing a goal or “object” of the inventors and held that “the inventors’ objective or goals cannot elevate the promise of the patent where the language of the patent does not support that promise.” In this regard the Court also held that “not all statements of advantage in a patent rise to the level of a promise.” 

On considering the test results presented by AstraZeneca as evidence of utility, the Court held that “no skilled person reviewing the test results would have doubts that anastrozole had utility…” and that “it is sufficient that the test results are ‘strongly suggestive’ of utility, and that no other logical explanation for the test results is likely.” The Court did not accept Mylan’s arguments that utility had not been demonstrated because the test results did not rise to the level of scientific certainty.

The Court confirmed that where utility is demonstrated, there is no need for the supporting evidence to be found in the patent itself.


The Court rejected Mylan’s alternative argument that it would have been obvious for a person skilled in the art  to arrive at the patented compound by making particular modifications to a specific starting compound disclosed in a prior art patent. The Court noted that: i) there were a number of potential starting points, none of which were preferred in the prior art; ii) the starting point suggested by Mylan was not one of the preferred compounds in the prior art patent it relied on; iii) a number of skilled groups were working in the same field and failed to arrive at the invention; iv) Lilly, the patentee of the prior art patent relied on by Mylan, was working with a different starting point and failed to arrive at the invention even after a number of years; and v) AstraZeneca made and tested over 1000 compounds before arriving at the patented invention.

On this basis, the Court found that Mylan’s allegation of obviousness was not justified. 

Link to decision:

AstraZeneca v Mylan Pharmaceuticals