USPTO relaxes requirement on structural similarity for Markush group
On Aug. 25, USPTO designated a PTAB decision in Ex parte Chowdhury (Appeal No. 2025-002261) issued in February as informative. The decision concerns the Board’s reversal of an Examiner’s rejection of claims based on improper inclusion of structurally diverse microRNAs (miRNAs) in a Markush group. The patent application (U.S. Application No. 17/005,548) at issue is directed to methods for determining exposure to radiation from the level of radiation-responsive miRNAs. The rejection stemmed from a process claim for treating radiation-induced damage by determining the serum levels of a list of radiation-responsive miRNAs before and after treatment. The Examiner rejected the claim for containing improper Markush groupings for the lack of structural similarity between the listed miRNAs as each has a different nucleotide sequence except for the only structural similarity in that all comprise nucleotides. The Examiner further established that the recited miRNAs do not belong to a chemical or art-recognized class as they are not expected to behave in the same manner or be substitutable in achieving the same result. The applicant appealed in arguing that at least one common property which is mainly responsible for their related function is sufficient for a proper Markush group in a process or combination claim. The Board found the appellant’s argument persuasive and reversed the rejection. The listed miRNAs all share the common function as markers of radiation-induced damage as fluctuations in their serum levels could be related to radiation exposure and treatment. The Examiner did not dispute the correlation and acknowledged the specification that identifies the quantity of the claimed miRNAs as representative of a patient’s exposure to radiation and its increase or decrease as a response to treatment. Therefore, the asserted miRNAs are interchangeable in the context of the invention. The Board cited two prior cases In re Harnisch (structurally distinct compounds all useful as dyes) and In re Jones (structurally distinct compounds all useful as plant growth stimulants) in view of the Federal Circuit’s holding in Multilayer Stretch to support the conclusion that a Markush group is proper if it recites members of a subgenus that are described in the specification to perform similar functions useful for the invention. This guidance helps to clarify what biomarkers could be properly grouped together. According to Ex parte Chowdhury, patents concerning biomarkers should expressly establish in the specification that subgenus of structurally diverse compounds can perform the same function in the claimed invention for them to be substitutable and properly recited in a Markush group. This recently designated informative decision serves as another useful case law to be cited for overcoming improper Markush grouping rejections of structurally distinct biomarkers, and distinct nucleic acid and amino acid sequences if common function in the context of the invention is clearly disclosed in the specification.
[This post is for educational purposes only. It reflects my own analysis of publicly available information, does not constitute legal advice, and does not create an agent-client relationship. Views expressed are my own, not those of any employer or client.]
