Pfizer Fails to Delay Approval of Generic Sildenafil Drug in Canada

In Pfizer Canada Inc v Ratiopharm Inc (2010 FC 612), Justice Kelen of the Federal Court (Court) denied an application by Pfizer Canada Inc (Pfizer) to prohibit the issuance of a Notice of Compliance for a generic version of REVATIO, produced by Ratiopharm Inc (Ratiopharm). REVATIO is a drug for use in treating pulmonary hypertension having sildenafil citrate as its active ingredient, the same active ingredient used in Viagra. Pfizer’s patent, which is listed against REVATIO in the Patent Register, claims the use of sildenafil in the treatment of pulmonary hypertension. Ratiopharm’s Notice of Allegation alleged that the patent was invalid for lack of sound prediction of utility, obviousness and anticipation. Ratiopharm also argued that the priority claim for the patent was invalid. Pfizer was unable to demonstrate to the Court that the allegations of lack of sound prediction and obviousness were unjustified. As a result, there was no need to consider the allegation of anticipation, Pfizer’s application was dismissed, and a Notice of Compliance was issued to Ratiopharm on the same day. Although Justice Kelen appeared to accept the argument that the British patent to which priority was claimed would have been invalid under Canadian law for a lack of sound prediction, he found that the priority claim was not invalid. Based on the wording in the Canadian Patent Act, the British patent application only needed to disclose the subject matter of the Canadian claims, whereas the validity of the British patent under Canadian law is irrelevant. Justice Kelen found that Pfizer had done insufficient testing as of the filing date of the Canadian application to soundly predict the efficacy of using sildenafil in treating all types of pulmonary hypertension, as claimed,. (Pfizer had been in the process of conducting more extensive trials at the filing date, but had not waited for the results before filing). For the full text of the decision, see: http://decisions.fct-cf.gc.ca/en/2010/2010fc612/2010fc612.html Summary by: Tom Feather