Cialis Canadian Patent Knocks Out Double Patenting Challenge

Eli Lilly's Canadian patent on treatment of erectile dysfunction with Cialis continues to defy all challengers. A recent appeal case originated from a Notice of Compliance proceeding brought by the generic drug manufacturer, Apotex¹, marked the fourth time that the Federal Courts² have rebuffed allegations of invalidity. This patent (no. 2,226,784) claims an improvement invention which is the use of tadalafil in the treatment of erectile dysfunction. The latest cases considered whether this use patent contains "patentably distinct" claims relative to an earlier Eli Lilly Canadian patent covering the tadalafil compound (no. 2,181,377). The basis of the challenge was that if the use patent claims were not novel and inventive over the compound patent claims, then the use claims would be invalid under Canada's strict double patenting laws.