In the Federal Court, Pfizer’s patent for amlodipine besylate was held invalid on numerous grounds, including obviousness. Pfizer appealed and the Federal Court of Appeal (“FCA”) dismissed the appeal. Pfizer had previously developed a maleate salt of amlodipine but it discovered this salt demonstrated processing disadvantages. Pfizer then made and analysed - via a salt screening process - a number of other salts of amlodipine and decided to proceed with and patent the besylate salt. This salt form was eventually sold under the brand name NORVASC.

The trial judge held that a salt screen selection process was routine work for the person skilled in the art at the time and held that the result of the salt screening was predictable or obvious to try. Furthermore, the judge held that the skilled person would be motivated to test the besylate salt as this had already been shown to offer advantages over other salts in terms of stability.

In dismissing the appeal, the FCA held that the trial judge had provided detailed, cogent and articulate reasons to support his judgment and that Pfizer had failed to demonstrate any palpable or overriding errors.

The full text of the decision can be found at:

http://decisions.fca-caf.gc.ca/en/2010/2010fca204/2010fca204.html