Canada - Scope of Patent Claim

In Canada, the owner of a patent covering a pharmaceutical product for which a request for authorization for marketing in Canada has been filed or granted may place that patent on the Patent Register maintained by the Ministry of National Health and Welfare. If a generic drug company wishes to obtain marketing authorization for a product that is on the Patent Register and to base its own application for marketing approval on a showing of bioequivalence with the patented pharmaceutical, it must either provide a statement that it will not market its generic product until after the patent expires or make certain allegations about the patent situation. If such allegations are made, the patent right holder can institute an action before the court to order the Ministry not to grant marketing authorization until the patent rights have expired. Possible allegations triggering this procedure include allegations that the patent rights have expired, the patent rights are invalid or that no claim of the patent would be infringed if the generic product were allowed to be marketed.

In Biovail Corp. v Canada (Minister of Health), a generic manufacturer had sought permission to market a generic long-acting version of diltiazem. At the time of the request there was no patent protection on the drug itself, but there was protection for an extended release formulation. The relevant claim reads as follows:

An extended-release galenical composition of ... (beads of a form of diltiazem) ... and an effective amount of a wetting agent to maintain solubility of the diltiazem in each bead, ensuring that the solubility of diltiazem is unaffected by the pH of the gastrointestinal tract or other adverse conditions which the composition will meet therein, said beads being coated with a microporous membrane ... and wherein the wetting agent is selected from ... (a defined group of compounds including sugars).

The generic manufacturer alleged that its product would not fall within this claim because, although it contained the specified beads containing diltiazem and a specified sugar, it asserted that the sugar did not act as a wetting agent to achieve the required result. It was claimed that the sugar in the generic product acted as a solid core within the beads which was surrounded by the active ingredient within the microporous membrane surrounding the bead. Adopting a purposive construction of the claim, and regarding the solubility-imparting language as defining an essential feature of the claim, the court held that for there to be infringement, the sugar present in the generic product had to act as a wetting agent satisfying the solubility-imparting requirements of the claim. The court therefore agreed with the generic manufacturer that its proposed product would not infringe the claim.

The case is of interest in pointing out how the recitation of a function for a specified element of a claim can have the effect of limiting the scope of the claim.