Markush's claim is the first inventor of Eugene Makush who successfully used this claim in 1920 U.S. patent and named it after Eugene Makush.
The Review Guide stipulates that when Markush elements are compounds, they shall be deemed to have similar properties and Markush's claim is single if the following criteria are met:
(1) All optional compounds have the same performance or function;
(2) All optional compounds have * * * isomorphic structure, which can be a characteristic different from the prior art and is essential for the * * * isomorphic property or function of the compound of the general formula; Or in the case that they cannot have the same structure, all optional elements should belong to the same compound class recognized in the field to which the present invention belongs.
If an application defines multiple parallel optional elements in a claim, it constitutes a "Markush" claim. Markush's claim should also comply with the provisions of Article 31, paragraph 1, of the Patent Law and Article 35 of the Detailed Rules for the Implementation of the Patent Law on oneness. If the optional elements in a Markush claim have similar properties, it should be considered that these optional elements are technically interrelated and have the same or corresponding specific technical characteristics, and the claim can be considered to meet the requirements of oneness. This optional factor is called Markush factor.