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Shared function sufficient for a proper Markush group

In a recently designated informative decision, the Patent Trial & Appeal Board reversed an examiner’s rejection of claims reciting structurally distinct microRNAs (miRNAs) as an improper Markush group. The Board found the claimed alternatives sufficiently related because they performed similar functions in the context of the invention. Ex parte Chowdhury, Appeal No. 2025-002261 (PTAB Feb. 5, 2026) (Flax, Katz, Hardman, A.P.JJ.) (designated informative Aug. 25, 2026).

The patent application at issue concerns methods for assessing and treating radiation-induced damage using levels of particular miRNAs in a patient’s serum. The claims recited groups of different miRNAs whose measured levels could be used to assess radiation damage and inform treatment decisions.

The examiner rejected the claims as containing improper Markush groupings. The examiner found that the recited miRNAs did not share substantial structural similarity because each had a different nucleotide sequence. Their only structural similarity was that each comprised nucleotides. The examiner also found that the miRNAs did not belong to a recognized chemical class that would have been expected to behave similarly or to be interchangeable for achieving the same result.

The Board reversed. It explained that a proper Markush group generally requires the listed alternatives to belong to a recognized physical or chemical class or to be sufficiently related by a common property or function. In assessing that requirement, however, the relevant inquiry is whether the alternatives are interchangeable for the purposes of the claimed invention.

The Board found that the claimed miRNAs satisfied that standard. Although the individual miRNAs were structurally different and did not necessarily perform the same biological function, the claims did not depend on those biological functions. Instead, each miRNA served the same claimed purpose: its serum level could be quantified and used as an indicator relevant to radiation-induced damage and treatment.

As the Board explained, the listed miRNAs did not need to function biologically in the same manner or produce the same biological result. They needed only to be quantifiable and interchangeable as markers for the purposes of the claimed method. Because the specification described the recited miRNAs as performing that common function, the Board found that they constituted a proper Markush grouping.




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Result-oriented claims fail to pass § 101 muster; industry standards may prove individual claim limitations

The US Court of Appeals for the Federal Circuit concluded that claims broadly directed to optimizing signal constellations for a particular result were patent ineligible, but upheld claims directed to specific constellations. The Court also confirmed that industry standards may be used on a limitation-by-limitation basis to prove infringement. Constellation Designs LLC v. LG Electronics Inc., et al., Case No. 24-1822 (Fed. Cir. Aug. 31, 2026) (Stoll, Lourie, JJ.; Oetken, District J., sitting by designation).

Constellation Designs sued LG for infringement of four patents directed to digital communication systems using signal constellations to transmit and decode data. Constellation accused LG televisions compatible with the ATSC 3.0 over-the-air television broadcast standard, specifically its A/322 protocol. The asserted claims fell into two groups: claims reciting geometrically spaced symbol constellations optimized for capacity using parallel decode (PD) capacity (optimization claims) and claims reciting specific non-uniform constellations (constellation claims).

The district court granted Constellation summary judgment that all asserted claims were patent eligible under 35 USC § 101. Following trial, a jury found that LG willfully infringed the asserted claims and awarded Constellation about $1.68 million in damages. The district court denied LG’s post-trial motions challenging infringement and damages, and entered an ongoing royalty of $6.75 per television. LG appealed.

Addressing patent eligibility, the Federal Circuit distinguished between the optimization claims and the constellation claims. At step one of the Alice framework, the Court concluded that the optimization claims were directed to the abstract idea of optimizing a constellation for PD capacity. The claims recited a desired result (improved capacity at a reduced signal-to-noise ratio) but did not recite how to achieve that result. The Court analogized the claims to the result-oriented claims found ineligible in other cases, explaining that the claims broadly covered essentially all ways of optimizing a constellation for PD capacity.

Although the specification described techniques for performing the optimization, the claims did not recite those details. The Federal Circuit explained that the § 101 inquiry focuses on the claim language and that technical details disclosed only in the specification cannot be imported into the claims to establish eligibility. At Alice step two, the Court found no inventive concept because Constellation’s alleged inventive concept (optimizing non-uniform constellations based on PD capacity) was the abstract idea itself. The Court therefore vacated the district court’s summary judgment of eligibility as to the optimization claims.

The Federal Circuit reached a different conclusion as to the constellation claims. Those claims did not broadly claim optimization but instead recited specific constellations developed using techniques described in the patents. The Court found that this distinction “makes all the difference” because the constellation claims recited a concrete implementation of a technological improvement directed to overcoming limitations in constellation capacity. The Court therefore affirmed the district court’s finding that those claims were patent eligible.

The Federal Circuit also affirmed the denial of LG’s motion for judgment as a matter of law of noninfringement. At trial, Constellation relied on the ATSC 3.0/A/322 standard to establish that the accused device met [...]

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