A “Markush” claim recites a group of elements in the very specific form “...wherein R is selected from the group consisting of A, B, C and D.” Although Markush claims originated in the United States, their use is permitted in Canadian patent practice.
At paragraph 11.11, the Manual of Patent Office Practice (“MOPOP”) states the following about Markush claims, concisely describing their origin, form, and substantive requirements:
In chemical cases, a claim directed to a genus expressed as a group consisting of certain specified materials is allowable (Ex parte Markush 1925, 340 U.S.O.G. 839) provided it is clear from the known nature of the alternative materials or from the prior art that the materials in the group possess at least one property in common which is mainly responsible for their function in the claimed relationship. Therefore, a Markush claim will generally be construed with a generic expression covering a group of two or more different materials (elements, radicals, compounds) as illustrated in the following examples:
A solvent selected from the group consisting of alcohol, ether and acetone...
A strip of a conductive metal selected from the group consisting of copper, silver and aluminium...
Occasionally, the Markush format may be used in claims directed to subject matter in the mechanical or electrical fields in a manner such as that illustrated in the example below:
A means for attaching a wall panel to a framework wherein the attaching means is selected from the group consisting of nails, rivets and screws... (emphasis in original)
It is thought that the Markush doctrine was developed by the USPTO as an exception to the prohibition against the use of alternative language in claims. Thus, an Applicant could not use the expression “glass or plastic” but could use a generic expression such as “impervious transparent material”. The Markush expression permits the subgenus to be defined without inclusion of the offending term “or”.
The USPTO no longer objects to alternative expressions using “or” and permits expression such as “wherein R is A, B, C or D” (U.S. Manual of Patent Examining Procedure section 2173.05(h)). The practice of the Canadian Patent Office is not entirely consistent; some Examiners object to “or” and others do not. Specific guidance is not provided in the MOPOP. However, without the insistence of an Examiner, there seems to be no circumstance in which an Applicant would be obliged to use a Markush claim. A recent decision of the Federal Court of Canada, discussed below, suggests that the Markush claim form may in fact be undesirable and may foreclose certain beneficial aspects of the interpretation of a claim under the Canadian Patent Act.
Section 27(5) of the Patent Act provides:
For greater certainty, where a claim defines 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.
Section 27(5) was enacted on October 1, 1996 and has no counterpart in previous versions of the Patent Act. Sections 2, 28.1 to 28.3 and 78.3 of the Act, which are referred to in section 27(5), concern issues of substantive patentability including, among other things, eligible subject matter, utility, novelty and unobviousness.
In the recent case of Abbott Laboratories and Abbott Laboratories Limited v. The Minister of Health and Ratiopharm, a Division of Ratiopharm Inc. (2005 FC 1095), the Federal Court of Canada had an opportunity to consider section 27(5) of the Patent Act in the context of a Markush claim.
In Abbott, at issue was the validity of claim 15 of Canadian Patent No. 2,261,732. This was a claim directed to a method for preparing Clarithromycin Form II and involved the treatment of an intermediate product with a solvent. The claim recited a Markush group of 17 solvents.
The Respondents alleged that five of the specified solvents could not be used in the claimed method to produce Clarithromycin Form II. Abbott, wishing to rely on claim 15 only in respect of a single solvent, argued that section 27(5) of the Patent Act allowed it to assert claims in the alternative, such that the elements of claim 15 should be interpreted as being separate claims, each specifying one of the 17 solvents. After reviewing various sources and authorities, including the MOPOP, the Federal Court concluded that section 27(5) did not apply to claim 15, stating as follows:
The key to a Markush claim is that it defines a homemade genus, all the members of which can be used interchangeably. By stating in claim 15 “a method according to Claim 2 wherein the solvent is selected from the group consisting of: acetone (...), and methanol-ethanol”, one can only conclude that any one of these solvents can be used to obtain the desired result. It is a claim to this group of solvents, it is not a claim to each of the solvents in the alternative.
I cannot accept that these listed solvents were meant as alternatives and that section 27(5) of the Patent Act applies. Section 27(5) of the Patent Act is of no help as it only applies “where a claim defines the subject matter of an invention in the alternative”. That is not the case here. By using the specific language suggested by the Commissioner and by using the word “or” instead of “and” [NB: there is clearly an error in the judgment here, with “or” and “and” being reversed] as the penultimate word of the claim, the drafter clearly made a Markush claim and asserted that the use of all of the specified solvents would produce the desired result.
Hence, claim 15 could not be read as a plurality of separate claims, but instead encompassed the solvents shown to lack utility. It cannot be known with certainty how section 27(5) would have been applied had claim 15 used the term “or” rather than Markush terminology. It is possible that the use of alternative claim language might have saved claim 15 by invoking the application of section 27(5).
Accordingly, to the extent that use of Markush terminology is not required in the Canadian Patent Office, the Abbott case suggests that it may be advantageous to avoid it with a view to benefiting from section 27(5) of the Patent Act. The Abbott decision has been appealed to the Federal Court of Appeal. It is not presently known whether the appeal will touch on issues surrounding section 27(5).
Canadian patent law and practice provide great flexibility in the presentation of patent claims. There are no excess claim fees or strict limits to the number of claims that may be presented, whether in independent or dependent form. As noted above, multiple dependent claims are permitted, and a multiple dependent claim may be dependent on another multiple dependent claim. After the claim is granted, in certain circumstances a disclaimer may be filed which refutes only part of a claim. The enactment of section 27(5) of the Patent Act would seem to expand the opportunity for comprehensive claiming even further.
It remains to be seen whether Markush claims will ultimately be regarded as claiming alternatives or a unitary group.