Federal Circuit clarifies patent-eligibility under 35 U.S.C. § 101 for claims covering recombinant DNA molecules
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On February 20, 2026, in REGENXBIO Inc. et al. v. Sarepta Therapeutics Inc., et al., No. 2024-1408, the Federal Circuit reversed a district court decision which held that claims covering a cultured host cell containing a recombinant nucleic acid molecule were patent ineligible under 35 U.S.C. § 101. The Federal Circuit held that the claimed host cells are “markedly different from anything occurring in nature” and therefore not directed to patent-ineligible natural phenomena. The Court relied on the fact that the claimed host cells are man-made compositions produced by combining nucleic acid sequences from different biological sources and introducing the recombinant molecule into a cell. The Court thus focused on the claimed composition as a whole rather than the individual, naturally occurring components of the claim. The decision provides an important reference point for satisfying the patent eligibility threshold under Section 101, particularly for biotechnology patents involving recombinant DNA technology.
Background
REGENXBIO Inc. and the Trustees of the University of Pennsylvania (collectively, “REGENXBIO”) filed a patent infringement suit against Sarepta Therapeutics, Inc. (“Sarepta”) in the U.S. District Court for the District of Delaware alleging infringement of U.S. Patent No. 10,526,617. The claims of the ‘617 patent are directed to genetically engineered host cells that contain adeno-associated virus (AAV) capsid protein sequences. REGENXBIO alleged that Sarepta’s gene therapy product for treating Duchene muscular dystrophy was made using an AAV variant that infringed upon the patent claims.
Claim 1 of the patent specifically recites: “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.”
On summary judgement, the District Court (Judge Andrews) held that the asserted patent claims are invalid under 35 U.S.C. § 101. The court concluded that “the mere fact that the ‘617 patent’s inventors combined natural products and put them in a host cell does not make the invention patentable under § 101.” REGENXBIO Inc. v. Sarepta Therapeutics, Inc., No. 20-cv-1226-RGA (D. Del. Jan. 5, 2024). Sarepta subsequently appealed the district court’s decision to the Federal Circuit.
Federal Circuit Rejects District Court’s § 101 Analysis and Reverses
On appeal, the Federal Circuit considered whether the claimed host cells have “markedly different characteristics” from that which is naturally occurring, following the Supreme Court’s analysis in Diamond v. Chakrabarty, 447 U.S. 303 (1980). The Court noted that “it is uncontested that the claimed host cells include a recombinant nucleic acid molecule that does not and cannot exist in nature.” The Court further explained that the claims require “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.” Accordingly, the Court concluded that the claimed host cells are patent eligible man-made compositions produced by combining naturally occurring sequences and transforming the host cell to create something that does not exist in nature.
In reaching its conclusion, the Court considered several prior decisions concerning patent eligibility for claims involving DNA technology. In particular, the Court examined the claims in Diamond v. Chakrabarty (directed to genetically engineered bacteria containing naturally occurring plasmids) and Funk Brothers Seed Co. v. Kalo Inoculant Co., 333 U.S. 127 (1948) (directed to a mixed culture of Rhizobia bacteria that could be used in growing leguminous plants) and concluded that the claims of the ‘617 patent are more analogous to the patent-eligible claims in Chakrabarty than the ineligible claims in Funk Brothers. The Court explained that “[l]ike the man-made plasmid combining four naturally occurring bacteria in Chakrabarty, the claimed nucleic acid molecules here, although containing naturally occurring segments of DNA, are ‘not nature’s handiwork’ and ‘not . . . a hitherto unknown natural phenomenon, but . . . a nonnaturally occurring manufacture or composition of matter’” (citing Chakrabarty, 447 U.S. at 309–10).
The Federal Circuit criticized the district court’s decision as focusing too narrowly on whether the individual components of the claim were naturally occurring and failing to consider whether the claimed composition as a whole was not naturally occurring. The Court concluded that splicing together naturally occurring sequences and inserting the resulting recombinant nucleic acid molecule into a host cell “unquestionably results in something new” (citing Association for Molecular Pathology v. Myriad Genetics, Inc., 569 U.S. 576, 595 (2013)).
The Federal Circuit similarly rejected Sarepta’s argument that the Court should focus on the AAV nucleic acid sequence alone because the other claim limitations are conventional and would not themselves be patentable. The Court declined to adopt Sarepta’s reasoning, explaining that controlling precedent does not direct the Court to “read out or ignore limitations in a claim merely because they may be found in the prior art or within the knowledge of a skilled artisan.”
Finally, the Court noted that to the extent the Alice/Mayo framework must be applied, the inquiry in this case ends at step one because the claims are not directed to a product of nature, and therefore the Court does not need to consider step two (i.e. whether there is an “inventive concept” that is sufficient to ensure that the patent amounts to more than the ineligible concept itself).
Takeaways
The Federal Circuit’s decision reaffirms that claims reciting biological compositions that are the result of human intervention and not simply directed to naturally occurring phenomena are likely to survive a patent eligibility challenge under 35 U.S.C. § 101. As REGENXBIO argued in this case, neither the claimed host cells nor the recombinant nucleic acid molecules incorporated into the host cells previously existed in nature. As a result, the Court found the claims were not patent ineligible, providing important guidance on the patent eligibility standard for biotechnology patents.
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