Norvasc Patent Invalid Despite “Contrary” Federal Court of Appeal Decision

Following a Federal Court trial, ratiopharm inc (ratiopharm) has won a declaration that a patent held by Pfizer Limited on the active ingredient of the cardiovascular medication Norvasc is invalid. Justice Hughes, in a lengthy decision, found that the subject patent was invalid on five different grounds: obviousness, invalid selection patent, inutility, insufficiency of the disclosure, and misleading disclosure. The patent claimed the besylate salt of amlodipine, which was asserted to have special advantages over free base amlodipine, a known substance, and other salts of amlodipine. Of the most significant issues, Justice Hughes found that the purported invention was no more than the result of a routine salt screen for the purpose of avoiding known problems with the free base, and so it was obvious, and thus invalid. For essentially the same reasons, he then ruled that the patent was not a valid selection patent. On the issue of insufficiency, Justice Hughes found that the patent did not correctly describe the invention as contemplated by the inventors. Justice Hughes compared what the inventors testified they had contemplated with what appeared in the patent, and found there were many serious errors, omissions, insertions from elsewhere and departures in the patent. The Federal Court of Appeal had earlier found that the same patent was a valid selection patent (See “Selection Patent Valid Says Pfizer Canada Inc v Ratiopharm,” E-TIPS®, Vol 5, No 16, February 14, 2007), but in the context of a prohibition application made in NOC proceedings. The Norvasc case is a reminder that, despite NOC proceedings that purport to find a patent to be valid, they are not a final determination of validity. For the full reasons for judgment in ratiopharm inc v Pfizer Limited [2009] FC 711, see: http://decisions.fct-cf.gc.ca/en/2009/2009fc711/2009fc711.html Summary by: Tom Feather