PTAB Designates Stakeholder-Nominated Ruling on Flexible Markush Analysis as Informative

Yesterday, the U.S. Patent and Trademark Office (USPTO) announced that the agency had designated as informative a Patent Trial and Appeal Board (PTAB) decision in an ex parte appeal reversing an examiner’s rejection of patent claims directed to the isolation and detection of microRNA (miRNA) to determine a patient’s risk of radiation exposure for improper Markush groupings. Drawing primarily upon case law from the predecessor to the U.S. Court of Appeals to the Federal Circuit, the informative designation is notable for its alignment with recent Federal Circuit case law encouraging flexibility in Markush grouping analyses.

Markush Grouping Not Improper if Members Substitutable to Achieve Claimed Result

Issued this February, the PTAB in Ex parte Chowdhury reversed an examiner’s rejection of patent claims for methods of treating radiation-induced damage in a human subject. According to the patent application’s specification, specific changes in the serum levels of specific miRNAs are radiation dose-dependent and correlate with the risk of developing radiation disease and related damage. These claims were rejected by the patent examiner because the list of miRNAs recited in the claims because the miRNAs each have a different chemical structure, whereas Manual of Patent Examining Procedure (MPEP) § 2117 requires that members of the Markush grouping “share a single structural similarity and a common use.”

In Chowdhury, the PTAB panel of administrative patent judges (APJs) recognized In re Harnisch, a 1980 ruling by the U.S. Court of Customs and Patent Appeals (CCPA), as the seminal case on claims reciting Markush groupings. In Harnisch, the CCPA found a “unity of invention” among a group claimed as compounds useful as dyes or intermediate dyes because the subgenus defined by the appellant was “not repugnant to scientific classification.” Further, in In re Jones, a CCPA ruling from 1947, the appellate court reversed the rejection of patent claims after finding that the Markush grouping of plant growth stimulants had a common function.

What those two cases make clear in view of the Federal Circuit’s 2016 holding in Multilayer Stretch Cling Film Holdings v. Berry Plastics, which affirmed the validity of claims reciting Markush groupings when the members of the group are substitutable with the expectation that the same result would be achieved, was that the inclusion of members useful for the invention’s function within a Markush group is not improper, the PTAB reasoned in Chowdhury. The PTAB found this conclusion further supported by the relevant MPEP section on Markush claiming, which notes that art-recognized classes exist when the prior art “establish[es] that it was well known that each member could be substituted for each other with the expectation that the intended result… would occur.” Chowdhury further highlights that the MPEP’s diaper claim example itself shows differences in structure among members of the same group, including a buckle and a hook-and-loop structure.

PTAB Aligns with Recent CAFC Rulings Encouraging Flexible Markush Analyses

In reviewing the examiner’s rejection, the PTAB noted that the examiner acknowledged that the miRNAs disclosed by Chowdhury’s claims are correlated with radiation exposure within the specification. Although the examiner’s position was that the claimed miRNAs must perform their biological functions in the same way related to the claimed invention, “[i]ndividual miRNA functionality is not contemplated in the context of the claimed invention,” the PTAB concluded.

Here, the claimed miRNA species are representative of a patient’s exposure to radiation and are thus quantifiable to achieve the claimed method of the invention. Within the context of the invention, those miRNA species do not need to function in the same way or to the same end for the claimed invention to work, the PTAB ruled. Far from being disputed, the examiner appeared to concede the similar function among the miRNAs within the context of identifying patient radiation damage, the PTAB acknowledged in a footnote. That the miRNA species are structurally different does not change that “they all reportedly function as quantitatively representative of patient radiation exposure and, so, they are substitutable for this purpose and are common members of an art recognized class,” the PTAB ruled.

Finding that the recited miRNAs are interchangeable within the context of the claimed invention, the PTAB reversed the examiner’s rejection for improper Markush grouping. In the press release announcing Chowdhury’s informative designation, the USPTO acknowledged that the case was nominated by an agency stakeholder. The Office allows stakeholders to anonymously nominate  “any routine decision of the Board for designation as precedential or informative, or to nominate for de-designation any Board decision that is currently designated as precedential or informative.”

The PTAB’s ruling in Chowdhury aligns with the increasingly flexible approach that the Federal Circuit has employed in recent years over Markush grouping analyses, starting with 2020’s Amgen v. Amneal Pharmaceuticals in which the CAFC found that the recited Markush group was not closed to unrecited members due to the presence of “comprising” transitional claim language. Then in Maxell v. Amperex Technology (2024), the Federal Circuit overturned an indefiniteness ruling after finding that the listing of transition metal oxides including cobalt within a Markush group, making cobalt optional to the claimed limitation, did not contradict a subsequent limitation requiring a certain amount of cobalt be present in the total composition.

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Author: burakowski
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