Draft:Markush doctrine

Markush doctrine

The Markush doctrine, in the context of U.S. patent law, refers to a set of legal rules and principles that permit a specialized form of patent claiming for certain inventions involving alternatively useable members.

The Markush doctrine is predominantly associated with patent claims for chemical inventions, however, the doctrine can be used to support patent claims for inventions in any technological field.

Although the rules governing patent prosecution and patent claim drafting are highly complex, the Markush doctrine relates to the patent “definiteness” requirement and can generally be understood as a legal exception to the USPTO policy against the use of alternative language in patent claiming. The Markush doctrine is subject to specific requirements and a number of rules regarding proper Markush claiming have been established by the USPTO and U.S. legal precedent. Improper claiming of Markush groups can result in rejection of claims during patent examination by the USPTO.

Overview

The Markush doctrine provides a mechanism for claiming alternatively useable members (“alternatives” or “alternative members”) in the form of a “Markush group” when there is no applicable, commonly accepted, generic expression that would clearly identify the group or subgroup in a given patent claim. The Markush doctrine is therefore particularly useful when claiming alternatively useable members in a chemical compound.

In a Markush claim, a patent applicant defines the scope of the invention by listing specific examples along with language that encompasses a broader class of compounds or elements. This allows the patentee to claim variations of the invention without explicitly enumerating every possible embodiment.

For example, a typical Markush claim might look like this:

"I claim a compound selected from the group consisting of A, B, C, or a combination thereof."

This claim covers not just the specifically mentioned compounds (A, B, C) but also any combination of those compounds. The Markush doctrine is particularly common in chemical and pharmaceutical patents where a broad range of structurally similar compounds may have similar utility.

Claiming Groups in Chemical Patents

The Markush doctrine is frequently employed by patent drafters when claiming inventions that involve chemicals and chemical compounds. However, the Markush doctrine is not limited to chemical patenting and may be utilized for inventions in any technological field. The name of this doctrine is taken from Eugene Markush; an inventor and the appellant in the case Ex parte Markush.

The chemical subjects of these claims are thus depicted in “Markush structures” included in patent applications and issued patents. These structures are used to represent four main types of structural variation within a chemical; substituent, positional, frequency, and homology, that are relevant to the claimed Markush group.

Markush Claim Examples

A hypothetical Markush claim for a chemical compound that claims an alternative group of alkali metals may generally be structured as follows:

What is claimed is, “an alkali metal selected from the group consisting of lithium, sodium, and potassium”.

In this example, the Markush group is defined as the group consisting of lithium, sodium, and potassium and is indicated by the closed transitional language “consisting of”. When employed properly, this language indicates that any of these elements in the Markush group may be substituted in the invention and still achieve the same intended result. Importantly, while the chemical group of alkali metals is well-defined and includes the six elements listed in Group 1(a) of the periodic table, the sub-group of alkali metals listed in this example have no proper nomenclature that can be used to identify such a sub-group. The Markush group therefore effectively permits such a group to be defined and claimed.

Origin of Doctrine

The original Markush claim (named for inventor Eugene Markush) is found in U.S. Patent No. 1,506,316. This patent claimed: “1. The process for the manufacture of dyes which comprises coupling with a halogen-substituted pyrazolone, a diazotized un-sulphonated 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 and effectively established the Markush doctrine.

General Requirements for Claiming Markush Groups

The general form of a Markush claim is generally written as “a member selected from a group consisting of A, B and C”. The language "consisting of" is employed to indicate that the listed members are a closed group. The main requirement with Markush claim drafting is that the claim recites a list of alternative useable elements in a manner that leaves no uncertainty about its scope. The group identified in the Markush claim presumably excludes mixtures, combinations or blends of the individually identified elements.

Single Structural Similarity and Common Use

Under current USPTO guidelines, proper Markush grouping generally requires that the members of a group share a single structural similarity and a common use. Members of a Markush group share a “single structural similarity” when they belong to the same recognized physical or chemical class or to the same art-recognized class. A recognized physical class, a recognized chemical class, or an art-recognized class is a class wherein there is an expectation from the knowledge in the art that members of the class will behave in the same way in the context of the claimed invention. In other words, each member could be substituted one for the other, with the expectation that the same intended result would be achieved.

If a Markush group is used to describe part of a combination or process, the members following “selected from the group consisting of” must be substitutable, one for the other, with the expectation that the same intended result would be achieved. If a Markush group is used to describe part of a chemical compound, regardless of whether the claim is limited to a compound per se or the compound is recited as part of a combination or process, the members following “selected from the group consisting of” do not necessarily need to share a community of properties themselves; the propriety of the grouping is determined by a consideration of the compound as a whole.

In general, a Markush group will generally be considered proper where all members of the group belong to a recognized class (whether physical, chemical, or art recognized) and are disclosed in the specification to possess at least one property in common which is mainly responsible for their function in the claimed invention, and it is clear from their very nature or from the prior art that all members possess this property. However, this is not an absolute requirement. Where a Markush group is used to describe alternative chemical compounds, either by words or chemical formulas, and the alternatives do not belong to a recognized class, the Markush group may still be considered to be proper where the alternatives share a substantial structural feature that is essential to a common use. However, it is important to note that the propriety of Markush groupings is decided on a case-by-case basis during patent examination by the USPTO.

Alternative Claiming and Rejections for Indefiniteness

In the United States, the definiteness requirement is set forth in the patent statute 35 U.S.C. § 112. The definiteness requirement is a legal standard in patent law that requires the claims of a patent to be clear, precise, and unambiguous in their language. In other words, a patent must clearly define the boundaries of the claimed invention, such that a person skilled in the relevant field can understand the scope of the invention with reasonable certainty. However, in the context of chemical patents, this requirement creates a challenge for drafting claims to chemicals wherein alternative chemical compounds may be interchanged to achieve the same desired result claimed in the invention. In certain circumstances, this problem may effectively be overcome through proper use of the Markush doctrine.