On February 20, 2026, the Federal Circuit held that patent claims directed to a cultured host cell are patent-eligible under 35 U.S.C. § 101—reversing a district court’s January 2024 decision granting summary judgment of patent ineligibility. The Federal Circuit decision makes clear that recombinant, human‑engineered host cells are patent‑eligible, even if their constituent sequences have natural origins.
The patent at issue (U.S. Patent No. 10,526,617) relates to genetically engineered host cells that contain adeno-associated virus (AAV) rh.10 sequences. Claim 1 of the ’617 patent is representative:
- A cultured host cell containing a recombinant nucleic acid molecule encoding an AAV vp1 capsid protein having a sequence comprising amino acids 1 to 738 of SEQ ID NO: 81 (AAVrh.10) or a sequence at least 95% identical to the full length of amino acids 1 to 738 of SEQ ID NO: 81, wherein the recombinant nucleic acid molecule further comprises a heterologous non-AAV sequence.
REGENXBIO Inc. and The Trustees of the University of Pennsylvania filed suit in the U.S. District Court for the District of Delaware against Sarepta Therapeutics, Inc. and Sarepta Therapeutics Three, LLC for 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 a gene therapy product referred to as SRP-9001, which treats Duchenne muscular dystrophy.
The district court granted Sarepta’s summary judgment motion and held all asserted claims of the ’617 patent ineligible under § 101. The district court had determined that “the ’617 patent’s claims disclose natural products, including the rh.10 sequence and a heterologous non-AAV sequence.” REGENXBIO Inc. v. Sarepta Therapeutics, Inc., No. CV 20-1226-RGA, 2024 WL 68278, at *4 (D. Del. Jan. 5, 2024), rev’d and remanded, No. 2024-1408, 2026 WL 479224 (Fed. Cir. Feb. 20, 2026). According to the district court, none of the individual naturally occurring components of the claims had been changed and “combining natural products and putting them in a host cell does not make the invention patentable under § 101.” Id. at *5. The district court found that the claims were like the ineligible claims at issue in Funk Brothers Seed Co. v. Kalo Inoculant Co., 333 U.S. 127 (1948), relating to a mixed culture of different species of bacteria, because “taking two sequences from two different organisms and putting them together is no different than taking two strains of bacteria and mixing them together.” Id. (cleaned up).
The Federal Circuit disagreed.
According to the Federal Circuit, the Supreme Court’s Chakrabarty case defines the inquiry, not Funk Brothers. In Chakrabarty, the Court held patent-eligible claims directed to a genetically engineered bacterium that was capable of breaking down components of crude oil. Applying Chakrabarty, the Federal Circuit asked whether the claimed host cells have “markedly different characteristics” and have “the potential for significant utility” from that which is naturally occurring. Diamond v. Chakrabarty, 447 U.S. 303, 310 (1980). The Federal Circuit emphasized that it was uncontested that the claimed host cells include a recombinant nucleic acid molecule that does not and cannot exist in nature. Specifically, the claims require (1) recombinant nucleic acid, meaning segments of nucleic acid from one source are artificially manipulated or inserted into the nucleic acid of another source through gene splicing; and (2) a nucleic acid molecule capable of encoding a sequence at least 95% identical to an AAV rh.10 sequence and a “heterologous” non-AAV sequence, where “heterologous” means from a different species. The court likened the claimed nucleic acid molecules here to the man-made plasmid combining four naturally occurring bacteria in Chakrabarty—although both contain naturally occurring segments of DNA, neither are “nature’s handiwork” nor “a hitherto unknown natural phenomenon, but [rather] a non-naturally occurring manufacture or composition of matter.” Chakrabarty, 447 U.S. at 309–10. And like the cDNA claims in Ass’n for Molecular Pathology v. Myriad Genetics, Inc., 569 U.S. 576 (2013), “the lab technician unquestionably creates something new” when she splices together the claimed recombinant nucleic acid molecule that encodes an AAV vp1 capsid protein and a heterologous non-AAV sequence and inserts said molecule into a host cell. Myriad, 569 U.S. at 595.
The Federal Circuit also rejected the district court’s analogy to the claims in Funk Brothers. The court explained that the claims 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 Federal Circuit also faulted the district court for focusing on the individual components of the claims rather than the claims as a whole, finding that the district court’s analysis took 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.’” REGENXBIO, 2026 WL 479224, at *7 (quoting Myriad, 569 U.S. at 594). The court pointed out that in Chakrabarty, the Supreme Court still held the claimed bacterium eligible even though the individual plasmids transferred into the host bacterium were naturally occurring.
The Federal Circuit noted that, although not required by Myriad, the claimed composition here—unlike the claims in Funk Brothers—has “the potential for significant utility,” as various embodiments of the claimed compositions “are beneficial for gene delivery to selected host cells and gene therapy patients,” in contrast to the claims in Funk Brothers, which recited a composition that functioned no differently whether packaging the individual components together or separately. Id. at *7.
Finally, the Federal Circuit sidestepped the well-known two-step Alice/Mayo framework, stating that because the claimed host cells are markedly different from anything occurring in nature, the patent-eligibility inquiry ends there. Nevertheless, the court further stated that “if resort to the Alice/Mayo framework is necessary, then at step one we conclude the asserted claims are not directed to a product of nature.” Id. at *9. Because the claims are not directed to ineligible naturally occurring subject matter at step one, the court declined to consider step two of the Alice/Mayo framework.