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Explore the latest in patent, trademark, and copyright cases on the Merchant & Gould LLP blog. Stay informed with expert insights on intellectual property law updates.

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Last week, the U.S. Court of Appeals for the Federal Circuit issued an opinion in <a href="https://www.cafc.uscourts.gov/opinions-orders/24-1408.OPINION.2-20-2026_2650255.pdf">REGENXBIO, Inc. v. Sarepta Therapeutics, Inc., No. 2024-1408 (Feb. 20, 2026)</a>, reversing summary judgment of patent ineligibility entered by the U.S. District Court for the District of Delaware.

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REGENXBIO sued Sarepta, alleging infringement of U.S. Patent No. 10,526,617, which is directed towards genetically engineered host cells containing a recombinant plasmid with a heterologous gene sequence. A recombinant gene is created by splicing together the genetic material. A “heterologous” sequence is spliced material that comes from a different species.

In district court, the parties cross-moved for summary judgment regarding patent eligibility. The district court held that the claims are patent ineligible because they are directed to a naturally occurring phenomenon. Specifically, the district court found that the claims of the ’617 Patent were analogous to the claims held ineligible in Funk Brothers Seed Co. v. Kalo Inoculant Co., 333 U.S. 127 (1948), which involved a mixed culture of naturally occurring species of bacteria, because both cases involve mixing two organisms together. REGENXBIO appealed.

The Federal Circuit applied the “markedly different characteristics” test from Diamond v. Chakrabarty, 447 U.S. 303 (1980), in which the Court determines if the subject matter has “markedly different characteristics” and has “potential for significant utility” from that which is naturally occurring.

The Court found that the recombinant DNA had markedly different characteristics. Sarepta did not contest that the claimed recombinant DNA “does not and cannot exist in nature.” The Court distinguished the claims of the ’617 Patent from Funk Brothers, because the markedly different characteristics test evaluates whether the composition as a whole is naturally occurring rather than whether the individual components of the composition are naturally occurring. The Court held that unlike mixing cultures of bacteria, gene splicing creates a fundamentally new molecule that could not form in nature on its own. The Court also found that the recombinant DNA has the potential for significant utility because the recombinant DNA provides a benefit to gene therapy that none of the individual components provide. The Court held that the functional utility of the composition may be considered even if it is not expressly claimed.

Federal Circuit Reverses Summary Judgment of Patent Non-Eligibility for Recombinant DNA

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