On February 20, 2026, in Case No. 24-1408, the CAFC reversed and remanded the district court’s summary judgment decision (Case No. 1:20-cv-01226 (D. Del.)) finding the claims of REGENXBIO’s U.S. Patent No. 10,526,617 (“the ’617 patent”) invalid under 35 U.S.C. § 101 as directed toward patent ineligible subject matter. The CAFC instead found the claims were not directed to a natural phenomenon and remanded for further proceedings in the infringement lawsuit. The opinion provided further guidance on what may be considered patent eligible subject matter under § 101, an area of the law that has been complicated to navigate for biologic inventions.
The ’617 patent is directed to genetically engineered host cells that contain adeno-associated virus (AAV) rh.10 sequences. The Background of the Invention notes that “[w]hat are desirable are AAV-based constructs for gene delivery.” In Case No. 1:20-cv-01226 (D. Del.)), REGENXBIO accused Sarepta’s gene therapy Elevidys® (delandistrogene moxeparvovec-rokl) of infringing claims 1 9, 12, 15, and 18–25 of the ’617 patent based on Sarepta’s use of the AAV variant rh.74 in cultured host cells to make Elevidys®.
District Court Decision
The district court considered the patent eligibility of the asserted claims under the “markedly different characteristics” framework from Diamond v. Chakrabarty, 447 U.S. 303 (1980), first noting that the asserted claims disclose natural products, including the rh.10 sequence and a heterologous non-AAV sequence. The district court then found that none of the naturally occurring components in the claims had been changed, similar to the patent ineligible claims in Funk Brothers Seed Co. v. Kalo Inoculant Co., 333 U.S. 127 (1948) that mixed two strains of bacteria together. “[C]ombin[ing] natural products and put[ting] them in a host cell does not make the invention patentable under § 101.”
The district court did not find that the claimed human-made genetically engineered host cell possessed utility for gene therapy because nothing in the claims disclosed use of the recombinant nucleic acid for a particular purpose.
Under Alice Step 2, the district court determined the claims lacked an inventive concept and the claimed invention was made using well-understood, routine, and conventional steps.
Federal Circuit Decision
The CAFC analyzed the claims under Chakrabarty, asking whether the claimed host cells have “markedly different characteristics” and have “the potential for significant utility” from that which is naturally occurring. They found the claims at issue were closer to the patent eligible claims in previous Supreme Court and Federal Circuit decisions (Chakrabarty and Myriad) than ineligible claims (Funk Brothers, Myriad, and ChromaDex) because “the claimed host cells include a recombinant nucleic acid molecule that does not and cannot exist in nature” as “the recombinant nucleic acid molecule must be spliced together via human intervention from at least two different species to meet the claim limitations.”
In distinguishing the claims from those at issue in Funk Brothers, the CAFC noted that “the claims here are not merely directed to repackaging products of nature. Genetically engineering two nucleic acid sequences from separate species into a single molecule and then transforming a host cell in order to incorporate that new molecule into it—thus fundamentally creating a cell containing a molecule that could not form in nature on its own—is materially different from growing more than one naturally occurring bacteria strain in a culture where none of the bacteria undergo any change from their natural state.”
The CAFC noted that the district court had taken “too narrow a view of the asserted claims by focusing on whether the individual components of the claim were markedly different from what is naturally occurring and failing to consider whether the claimed composition as a whole was ‘not naturally occurring.’”
The CAFC also disagreed with the district court’s determination that there was no utility, finding instead that the patent had various embodiments that were beneficial for gene delivery and gene therapy, a utility which the isolated sequences on their own did not have. The Court confirmed that in a Chakrabarty analysis, “the court may consider whether the claimed composition has ‘the potential for significant utility’ even if that utility is only implicit.”
While the CAFC did not specifically analyze the claims under Alice / Mayo because they found the claims patent eligible under the “markedly different” test, they noted that if they had analyzed them under Alice / Mayo¸ they would have found the claims were not directed to a product of nature in Step 1.
Sarepta reported $898.7 million in net revenue from Elevidys® in 2025.
For more information on this and other gene therapy and biologic drug patent disputes, please visit BiologicsHQ.com.
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The author would like to thank April Breyer Menon for her contributions to this article.
