6.1.4.4 Markush Practice

Also in this Chapter:

• 6.1.4.1 Unity of Invention Background

• 6.1.4.2 Determining Lack of Unity

• 6.1.4.3 Combinations of Different Categories of Claims

• 6.1.4.5 Intermediate and Final Products in Chemical Applications

• 6.1.4.6 Biotechnological Inventions

• 6.1.4.7 Single General Inventive Concept

• 6.1.4.8 A Priori and A Posteriori Lack of Unity

• 6.1.4.9 Issuing the Invitation to Pay Additional Search Fees

• 6.1.4.10 Unsupported, Unclear, Long and/or Complex Claim Sets

• 6.1.4.11 Payment of Additional Search Fees Under Protest

• 6.1.4.12 Completing the Search Report

• 6.1.4.13 Time for Completing the Search Report

• 6.1.4.14 Reported Decisions on Unity

• 6.1.4.15 Other Decisions on Unity from the EPO

Key Legislation:​​​​​​​

Regulations under the PCT:

• Rule 13 Unity of Invention

PCT ISPE Guidelines:

• Chapter 10 Unity of Invention​​​​​​​

  • Paragraph 10.17

  • ​​​​​​​​​​​​​​Paragraphs 10.28 – 10.33

  • Paragraphs 10.45 – 10.49

  • Paragraphs 10.52 – 10.54

On this page

• Definitions

• Requirements for unity

• Consideration of unity for Markush claims

  • Common activity or property

  • Significant structural element or property

  • Recognised classes of chemical compounds

  • Examples

• Mixtures of chemical compounds

Definitions

A Markush claim is a claim that defines alternatives. Markush claims can be either chemical or non-chemical, provided they amount to a claim to alternatives (see PCT/GL/ISPE/12 at paragraph 10.17). It follows that a claim to a list of compounds identified by name or a generic formula are equally regarded as Markush claims.

Requirements for unity

For Markush claims, the requirement of a technical interrelationship and the same or corresponding special technical features, as defined in Rule 13.2, are to be considered to be met when the alternatives are of a ‘similar nature.’ Compounds are regarded as being of a ‘similar nature’ where the following criteria are fulfilled (see PCT/GL/ISPE/12 at paragraph 10.17):

1. All alternatives have a common property or activity.

2. One of the following applies:

   1. A common structure is present, i.e., a significant structural element is shared by all of the alternatives.

   2. All alternatives belong to a recognized class of chemical compounds in the art to which the invention pertains.

Consideration of unity for Markush claims

Common activity or property

To establish unity, Markush claims must have a common activity or property. To be considered a ‘common activity or property,’ the activity or property must be present in all alternatives falling within the scope of the Markush claim.

Significant structural element or property

In addition, it is only necessary for there to be a ‘significant structural element shared by all of the alternatives.’ It is not necessary for this ‘significant structural element’ to be novel.

The words ‘significant structural element is shared by all of the alternatives’ refer to cases where the compounds meet one of the following criteria:

1. Share a common chemical structure which occupies a large portion of their structures

2. If the compounds only have a small portion of their structures in common, both:

   1. The commonly shared structure constitutes a structurally distinctive portion in view of existing prior art

   2. The common structure is essential to the common property or activity

The structural element may be a single component, or a combination of individual components linked together.

Recognised classes of chemical compounds

When determining whether a group of chemical substances belong to a recognised class, the class must be one in which there is a reasonable expectation that the members will behave in the same way, in the context of the invention. However, the nature of the class should be consistent with scientific logic, and not merely a restatement of the common property. For instance, a group of enzymes that were isolated from a single organism would not be properly regarded as a class based on the organism of origin. However, if all of the enzymes also had a common or related activity, that could be the basis of a class.

Examples

Paragraphs 10.28 to 10.33, 10.45 to 10.49, and 10.52 to 10.54 of the PCT International Search and Preliminary Examination Guidelines considers unity of invention and Markush claims and the practice described is illustrated in examples 8 to 13, 25 to 29, and 32 to 34.

Examples 8 to 13, 25 to 29, 32 to 34 in paragraphs 10.28 to 10.33, 10.45 to 10.49, and 10.52 to 10.54 of the PCT International Search and Preliminary Examination Guidelines provide some assistance in determining if a common ‘significant structural element’ exists for a chemical structure containing alternatives.

Mixtures of chemical compounds

The Markush concept can also be applied to a claim involving mixtures of chemicals where the components of these mixtures are selected from particular groups. In example 33 (PCT International Search and Preliminary Examination Guidelines), the mixtures of herbicidal agents A and B failed this ‘recognised class of chemical compounds’ test because the ‘B’ group herbicides represented a plurality of classes of compounds.