Invalidity Allegations with Respect to Controlled Release Oxycodone Compositions Patent Found Not Justified
Purdue Pharma v. Pharmascience Inc. 2009 FC 726 (Harrington, J.)

July 16, 2009

Anthony Creber, James Mills and Chantal Saunders for the Applicant, Purdue Pharma (“Purdue”)
Carol Hitchman and Paula Bremner for the Respondent, Pharmascience Inc. (“Pharmascience”)

On this application, Purdue sought a prohibition order against Pharmascience with respect to Canadian Patent No. 2,098,738, which claims a novel 12-hour controlled release formulation of oxycodone having a specific pharmacokinetic profile. Pharmascience raised a number of invalidity challenges.

With respect to anticipation, Justice Harrington dismissed the prior use alleged as being within a confidential in vivo test and therefore not a public disclosure. With respect to written prior disclosures, he applied the test for anticipation from the Supreme Court's 2008 Plavix decision, Apotex Inc. v. Sanofi-Synthelabo Canada Inc., and noted that none of the prior documents set out all the information needed to produce the claimed invention.

Justice Harrington also applied the test for obviousness set out in the Plavix decision, finding that the inventive concept was controlled release oxycodone staying within the boundaries of a particular dissolution and pharmakinetic profile from 10 to 14 hours. He added, in commenting on how this differed from the state of the art, that the inventive concept was not the idea, but rather getting it to work. In examining whether the formulation was “obvious to try”, Justice Harrington noted the several parameters a formulator would have to consider, and the years of work carried out by one of the inventors with so many trials and so many errors, to conclude that it was not self-evident that what was being tried ought to work. Further, he found there was a considerable amount of work required to achieve the invention and that the trials were not routine. With respect to the motive factor in the "obvious to try" test, Justice Harrington noted there was not much motive within the pharmaceutical industry at large for this development.

The application also included an issue of sound prediction as the dosages tested in vivo were only 4 mg to 30 mg while compositions containing from about 10 mg to about 160 mg of oxycodone were claimed. Justice Harrington found the factual basis and sound line of reasoning from which the desired result could be inferred to be grounded in the immediate release oxycodone tablets already on the market which were useful pain killers and which possessed a particular pharmacokinetic profile. He noted the characteristics of larger dosages could be predicted by "partition coefficient" and concluded the reasoning for the claimed formulation had been articulated.

Overbreadth and lack of disclosure was also alleged, as Purdue had claimed matrixes which could lead to several hundreds of different formulations but only disclosed variants of the previously patented AcroContin system. Justice Harrington noted the presumption that non-essential variants fall within the scope of a claim and remarked that no bargain is struck for disclosing the invention if it can be worked around by using a non-essential variant in a matrix. He also noted that Purdue did not claim all routes to the desired result as Pharmascience was not prevented from using other methods to control the release of oxycodone or to use a different in vitro profile or a different in vivo profile.

As every invalidity challenge was dismissed, Justice Harrington granted the prohibition order.

By: Christopher Heer, Bennett Jones LLP