As patent law in Canada continues to evolve in signifi cant ways, it is important to remind ourselves of cases from the past few years that continue to impact patent drafting today and to infl uence the validity of patents, especially pharmaceutical patents in Canada. The decision in the Federal Court by Justice von Finckenstein in Abbott Laboratories et al. v. Minister of Health et al. in 2005 is one of these cases that is important to revisit.

At issue was Canadian patent 2,261,732 and specifi cally claim 20, which was a claim to clarithromycin Form II when prepared by the process defi ned in claim 15. The issue surrounded claim 15, a “Markush-type” claim to a process for preparing clarithromycin Form II including using a solvent selected from a group consisting of 17 specifi ed solvents wherein three of the specifi ed solvents had later shown to lack the desired utility.  

The Court considered whether each of the 17 specifi ed solvents required utility in the preparation of clarithromycin Form II to determine whether claim 15 had validity. If it was determined one of the 17 specifi ed solvents of the Markush group lacked utility, claim 15 may be invalid for lacking utility.

Section 27(5) of the Canadian Patent Act states the following:

27(1) The Commissioner shall grant a patent for an invention to the inventor or the inventor’s legal representative if an application for the patent in Canada is fi led in accordance with the Act and all other requirements for the issuance of a patent under this Act are met.  

(5) For greater certainty, where a claim defi nes the subject-matter of an invention in the alternative, each alternative is a separate claim for the purposes of section 2, 28.1 to 28.3 and 78.3.  

In view of section 27(5) of the Patent Act, if the specifi ed solvents of the Markush group are treated as alternative options, then the inutility of one solvent would simply invalidate that particular solvent and would have no bearing on the remaining solvents, as each is considered a separate claim. It must, therefore, be determined whether a Markush-type claim should be considered an alternative claim, or if the entire group must be considered as requiring utility.

A Markush claim was defi ned in the Manual of Patent Offi ce Practice at chapter 14, section 14.03.02 as a claim covering selected members of a genus as contrasted to all the members of a genus, so as to exclude inoperative members of the group. It also states:  

Markush groupings will be considered to be directed to one invention when all of the members of the group have a common basic structure and/or a common property or activity is present. In those cases where a common property or activity is present, all of the members are expected to behave in the same way in the context of the claimed invention.

Justice von Finckenstein reviewed the language of claim 15 and noted the exact words “selected from the group consisting of,” as well as the word “and” instead of “or” before enumerating the last solvent are used in claim 15 as required for a Markush claim. The resolution is laid out in Justice von Finckenstein’s decision and specifi cally paragraphs [26] and [27].

It is clear from the fi ndings that by employing Markush language in a claim, it was the drafter’s intent that all members of the Markush group be treated together and not in the alternative, and further, that all members of the group must have the desired utility for the group to withstand an attack of validity. Although not indicated in the fi ndings, it must be considered that had the drafter used more appropriate alternative language, such as using the term “or” before the last alternative and avoiding the identifi cation of a group when defi ning a genus, the solvents of claim 15 may have been found to have been claimed in the alternative and allowed the benefi t of section 27(5) of the Patent Act.  

In view of this fi nding, a clear drafting practice should be implemented to avoid Markush language when possible and to use alternative claim language when drafting patent specifi cations. It may be possible to amend claims after the application is fi led to replace Markush language with alternative language. However, such an amendment can introduce the risk of a rejection for introducing new subject matter or, even more severe, invalidate an issued patent for introducing new subject matter during prosecution.