Desvenlafaxine Polymorph Patent Not Obvious – Federal Court

The Federal Court simultaneously issued a pair of prohibition orders against Teva and Apotex in relation to the drug desmethyl-venlafaxine succinate, which Pfizer sells under the brand name PRISTIQ. In separate proceedings, Teva and Apotex each alleged that Pfizer’s Canadian Patent No. 2,436,668 was invalid for obviousness and lack of utility. Apotex additionally asserted non-infringement, anticipation, overpromising in relation to section 27(3) of the Patent Act, and double-patenting. The Court held that Teva and Apotex’s allegations were not justified and issued a prohibition order in each case.

Desvenlafaxine is used in the treatment of depression. The prior art disclosed that venlafaxine and its metabolite, desvenlafaxine, were useful to treat depression. Pfizer asserted that there was no solid-state form of desvenlafaxine itself that could be safely stored, formulated into a drug and administered to patients. Pfizer’s patent claimed a solid crystalline form of desvenlafaxine that appeared stable, soluble and bioavailable.


Justice Brown held that the allegations of obviousness were not justified. The inventive concept of claims 8 and 9 was the novel crystalline form of desvenlafaxine (also known as “ODV”) succinate referred to as Form I. The gap between the state of the art and this inventive concept was the invention of the new composition of matter. The Court held that the skilled person would not have come directly and without difficulty to this novel crystalline form, in part because Form I was not previously disclosed in the art:

In my respectful view, and as the experts agree, it would not have been possible at the relevant time for a Skilled Person to predict whether ODV succinate salt would form as a solid, whether that solid would be crystalline, or what the properties of any hypothetical crystalline solid would be. This is the case regardless of the fact that salt screens were generally known as were, also in general terms, crystallization and polymorph screens. In fact, neither ODV succinate nor any of its crystalline forms, let alone Form I, were specifically previously disclosed in the art.

An “obvious to try” analysis may be appropriate “in areas of endeavour where advances are often won by experimentation.”  The Court thus assessed the three obvious to try factors set out by the Supreme Court in Sanofi. First, the Court held it was not self-evident that what was being tested ought to work. The evidence established that there were possibilities of identifying the claimed compound, but mere possibilities are not sufficient. Second, the crystallization and polymorph screening performed by SSCI was seen as difficult and prolonged, not merely routine.  Third, there was a lack of specific motivation in the prior art to find the novel crystalline Form I desvenlafaxine claimed. The Court noted the need for “specific motivation” rather than a general motive. These factors pointed away from finding that it was “obvious to try”.


The Court held that the allegations of inutility were not justified. Justice Brown noted that the Supreme Court changed the law in AstraZeneca and applied the two-step test set out in that case: “to identify the subject-matter of the invention as claimed in the patent” and then determine “whether that subject-matter is useful – is it capable of a practical purpose (i.e. an actual result).” The utility must be either demonstrated or soundly predicted. Only a scintilla of utility is required. The subject-matter of the independent claims was the Form I desvenlafaxine succinate. By the relevant date, it had been established that Form I desvenlafaxine succinate was useful as a stable, solid-state form of desvenlafaxine succinate. The claims thus did not lack utility.

Apotex asserted that the patent “overpromised” in violation of section 27(3) of the Patent Act. Justice Brown noted that AstraZeneca declared overpromising to be “a mischief” but held that the Supreme Court had not moved the promise doctrine from the utility analysis into the specification analysis: “If that was the case, a major underlying problem identified by the Supreme Court itself would remain, namely that ‘a patentee will be dissuaded from stating the invention can be used for things that are not sufficiently established at the time of filing if doing so would risk invalidating the entire patent.’”

A copy of the Teva decision can be found here. A copy of the Apotex decision can be found here.

Teva and Apotex have each appealed (A-283-17 and A-288-17, respectively).

Teva was represented by Aitken Klee LLP.