Markush groups define claimed subject matter in a form such as “the group consisting of A, B and C”, whereas alternatives may be recited in a form such as “A, B or C”.  In Eli Lilly Canada Inc v Mylan Pharmaceuticals ULC(“Eli Lilly v Mylan”), 2015 FC 17, the Federal Court, in upholding the patent at issue, considered the validity of claims that recite Markush groups compared to claims to alternatives.

Patent Act

The Canadian Patent Act does not explicitly address Markush groups, but does explicitly address claimed alternatives, as follows:

27. (5) 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 sections 2, 28.1 to 28.3 and 78.3. [emphasis added]

Sections 2, 28.1 to 28.3 and 78.3 of the Patent Act relate to substantive requirements for patentability, such as utility, novelty and non-obviousness.

Abbott decisions

In Abbott Laboratories v Canada (Minister of Health) (“Abbott I”), 2005 FC 1095, the Federal Court distinguished Markush groups from alternatives and defined a Markush claim as a claim to the entire group. InAbbott I, the Federal Court concluded that an entire Markush claim was invalid because some (but not all) of the solvents in the Markush group lacked utility.

Section 27(5) of the Patent Act could be interpreted to mean that if the solvents in the Abbott I decision had been defined as alternatives instead of as a Markush group, then each solvent would be a separate claim, and the claims to solvents that had utility could still be valid. If that interpretation of section 27(5) were correct, then alternatives might be stronger than Markush claims in Canada.

However, in Abbott Laboratories v Canada (Minister of Health) (“Abbott II”), 2005 FC 1332, the Federal Court considered the same Markush claim that was at issue in Abbott I, and stated that even if the claim had recited an alternative as contemplated by section 27(5), then the whole claim would still fail if any of the alternatives were not patentable. The Court reached that conclusion by characterizing section 27(5) as “principally an administrative provision for purposes of a patent application”.

The Abbott I and Abbott II decisions together seem to suggest that both Markush claims and claims to alternatives will fail entirely in Canada if they include any invalid embodiments.

Eli Lilly v Mylan

The more recent Eli Lilly v Mylan decision, on the other hand, suggests that Markush terminology may be the better choice. In that decision, the Federal Court considered claim 2 in Canadian patent no. 2,226,784, which recites the following:

  1. A pharmaceutical composition for the curative or prophylactic treatment of erectile dysfunction in a male animal, comprising a compound selected from the group consisting of:

[tadalafil] or a physiologically acceptable salt or solvate thereof; and

[3-methyl tadalafil] or a physiologically acceptable salt or solvate thereof,

together with a pharmaceutically acceptable diluent or carrier.

The issued claim includes chemical formulas, which for simplicity have been replaced by “[tadalafil]” and “[3-methyl tadalafil]” in the excerpt above.

Mylan argued that 3-methyl tadalafil lacked utility, so the Court considered whether a lack of utility of 3-methyl tadalafil would affect the validity of claim 2. Because claim 2 defines a “group consisting of” different compounds that are joined with “and”, the Court characterized the claim as a Markush claim, rather than as a claim directed to alternatives that would be subject to section 27(5) of the Patent Act.

The Court reaffirmed its previous interpretation of section 27(5) in Abbott II, namely that if a claim defines alternatives, then the entire claim fails if one of the alternatives is invalid. Because claim 2 was a Markushclaim, rather than a claim to alternatives, the Court concluded that section 27(5) did not apply and that claim 2 would not be invalid for lack of utility, even if 3-methyl tadalafil did lack utility. Therefore, the Court did not actually decide whether 3-methyl tadalafil lacked utility. The Court’s approach in Eli Lilly v Mylan appears to be contrary to Abbott I, in which the Federal Court rejected a Markush claim that included both valid and invalid embodiments.

The Eli Lilly v Mylan decision has been appealed to the Federal Court of Appeal, which may clarify the significance of claims to Markush groups and the impact of section 27(5).

Claim drafting considerations

In some cases, Markush groups are important forms for defining claimed genera. In other cases, and particularly in jurisdictions where excess claims fees are charged, patent applicants may define Markush groups or alternatives to try to reduce or avoid excess claims fees. However, Canadian patent applications do not incur excess claims fees, so where practical, reciting separate elements in separate claims may be prudent to avoid the ongoing uncertainty regarding Markush groups and alternatives.