REGENXBIO, Inc. v. Sarepta Therapeutics: Recombinant DNA Molecule Patent-Eligibility Under 35 U.S.C. § 101

On February 20, 2026, the U.S. Court of Appeals for the Federal Circuit (CAFC) issued a decision regarding recombinant DNA subject-matter eligibility, reversing a decision by the United States District Court for the District of Delaware in REGENXBIO, Inc. v. Sarepta Therapeutics. The district court had previously ruled claims of U.S. Patent No. 10,526,617 (the ‘617 patent) covering a cultured host cell containing a recombinant nucleic acid molecule patent ineligible under 35 U.S.C. § 101 during a patent infringement suit in which both parties moved for summary judgment of patent eligibility under 35 U.S.C. § 101. The district court agreed with Sarepta and held the claims ineligible under § 101 as directed to a natural phenomenon. The CAFC held the claims as not being directed to a natural phenomenon and reversed the district court’s decision, remanding the case for further proceedings.

REGENXBIO Inc. and the Trustees of the University of Pennsylvania previously filed a patent infringement suit against Sarepta Therapeutics, Inc. in the U.S. District Court for the District of Delaware alleging infringement of the ‘617 patent. The patent claims cover genetically engineered host cells containing adeno-associated virus (AAV) sequences, a technology used to treat genetic disorders like Duchenne muscular dystrophy by delivering therapeutic genes to replace defective or missing genes. In the suit, REGENXBIO alleged that a Sarepta Therapeutics Duchene muscular dystrophy gene therapy product infringed on the ‘617 patent with an AAV variant. Claim 1 of the ‘617 patent 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.”

In the summary judgement, delivered in January 2024, the district court held that the claims are patent-ineligible under 35 U.S.C. § 101 and therefore invalid. The district court concluded that taking “two sequences from two different organisms and putting them together” is “no different than taking two strains of bacteria and mixing them together” citing the Supreme Court’s 1948 decision in Funk Brothers Seed Co. v. Kalo Inoculant Co, in which the Supreme Court held that a trivial implementation of a natural principle or phenomenon of nature is patent-ineligible. The district court reasoned that the individual naturally occurring components had not been “changed” sufficiently, and that combining natural products does not make an invention patentable.

The Federal Circuit unanimously reversed the district court’s decision, finding that “The cultured host cells required by the claims are undisputedly human made. They do not exist in nature.” The CAFC held that the claimed host cells are “markedly different from anything occurring in nature,” and are therefore patent-eligible. The Court determined that the claimed host cells are man-made, created by chemically splicing together nucleic acid sequences from two different organisms and introducing the recombinant molecule into a cell, focusing on the claimed composition as a whole rather than the individual naturally occurring components.

The Court explained that Chakrabarty defines the issue at hand: to be patentable, the claimed host cells must have “markedly different characteristics” and have “the potential for significant utility” from that which is naturally occurring. Through this lens, the CAFC determined that the ‘617 patent claims are analogous to the eligible claims in Chakrabarty. The CAFC concluded that the claimed nucleic acid molecules, while 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.”

The Federal Circuit’s decision provides useful context and practical lessons for determining patent eligibility thresholds under 35 U.S.C. § 101, particularly for recombinant DNA and related technologies. Courts should not only focus on individual compositional components, but also on the claimed composition as a whole, while analyzing patent eligibility of nature-based inventions. This decision reasserts that biological compositions requiring human intervention to produce are likely be determined patent eligible under 35 U.S.C. § 101.

This decision is available here.

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