Annex AA - Markush Claims

Date Published

Markush claims were named after Dr Eugene A Markush, the first inventor to use this style of claiming successfully in a US patent.  In 1923, Dr Markush filed a patent application claiming a method of preparing a generic group of pyrazalone dyes for wool or silk:

1. The process for the manufacture of dyes which comprises coupling with a halogen-substituted pyrazalone, a diazotized unsulphonated material selected from the group consisting of aniline, homologues of aniline and halogen substitution products of aniline.

The claim was challenged as being too unspecific.  On appeal, the US commissioner of Patents ruled on the propriety of such claims. The patent was granted in 1924 as US 1506316.

A group of chemical entities that are considered equivalent for the purposes of the invention are referred to as a “Markush group”. If a compound being patented includes several Markush groups, the number of possible compounds it covers could be vast.

A typical example of a Markush structure would be:

Each of R1, R2, R3, X, Y and Z are Markush groups. The total number of compounds defined by the structure is the numbers of the members of each group all multiplied together.

Extremely broad Markush claims may cover millions of compounds with a single generic structure.  Some structures stretch over many pages and contain so many variable moieties that it becomes impossible to visualize what the applicant is seeking to protect.