Understand Your Rights. Solve Your Legal Problems
REGENXBIO Inc. and the Trustees of the University of Pennsylvania have won a key appellate reversal in their dispute with Sarepta Therapeutics. On February 20, 2026, the U.S. Court of Appeals for the Federal Circuit held that the asserted claims of U.S. Patent No. 10,526,617 are not directed to a natural phenomenon under 35 U.S.C. § 101.
The decision overturns a District of Delaware ruling that had granted Sarepta summary judgment on eligibility and sends the matter back for further proceedings. For life sciences companies litigating biologics and gene-therapy related patents, the opinion underscores the importance of claim language that ties the invention to human-made recombinant constructs, not merely natural sequences.
REGENXBIO and the University of Pennsylvania sued Sarepta Therapeutics, Inc. and Sarepta Therapeutics Three, LLC in the District of Delaware, alleging infringement of claims 1–9, 12, 15, and 18–25 of U.S. Patent No. 10,526,617.
The Federal Circuit describes the ’617 patent as directed to genetically engineered host cells containing adeno-associated virus (AAV) rh.10 sequences. A representative claim recites a cultured host cell containing a recombinant nucleic acid molecule encoding an AAV vp1 capsid protein sequence (AAVrh.10 or a sequence at least 95% identical), where the recombinant nucleic acid molecule further comprises a heterologous non-AAV sequence.
According to the opinion, REGENXBIO accused Sarepta based on Sarepta’s use of an AAV variant (rh.74) in cultured host cells to make a gene therapy product referred to as SRP-9001, described as treating Duchenne muscular dystrophy.
Both sides sought summary judgment on whether the asserted claims were patent-eligible under § 101.
The Federal Circuit reversed the district court’s judgment that the asserted claims are ineligible under § 101 and remanded for further proceedings.
The panel held the claims are not directed to a natural phenomenon, emphasizing that the claims require a recombinant nucleic acid molecule that “does not and cannot exist in nature” and is spliced together through human intervention from at least two different species and inserted into a host cell.
Because the panel concluded the claims are not directed to ineligible subject matter at step one, it did not proceed to step two of the Alice/Mayo framework.
The district court had treated the claims as disclosing natural products and concluded that “combining” natural products in a host cell was not enough, analogizing the claims to Funk Brothers, where mixing naturally occurring bacteria strains was held ineligible.
The Federal Circuit rejected that analogy as inconsistent with the claim requirements and the record described in the opinion. The panel distinguished between (1) simply packaging or mixing natural materials and (2) creating a new, human-made construct that cannot exist in nature on its own.
Central to the court’s reasoning was the claim language requiring:
“recombinant” nucleic acid (created by splicing sequences from different sources), and
a “heterologous” non-AAV sequence (from a different species).
The panel likened the asserted claims to eligibility outcomes where laboratory intervention produces something new, and it criticised the lower court for focusing narrowly on whether the individual natural components were themselves altered, rather than assessing the claimed composition as a whole.
The court also rejected Sarepta’s attempt to characterise the claims as effectively directed only to isolating the AAV rh.10 sequence. The claim language, the panel said, requires a cultured host cell and a recombinant nucleic acid molecule coding for both the capsid sequence and the heterologous non-AAV sequence.
Finally, the Federal Circuit declined to “read out” allegedly conventional limitations for purposes of the § 101 analysis, noting that eligibility should not be collapsed into novelty/obviousness concepts.
Drafting matters: Claim terms like “recombinant” and “heterologous” can be outcome-determinative in § 101 disputes because they anchor the invention to a human-made construct.
§ 101 is not everything: Even where eligibility is revived, defendants can still press other validity theories and noninfringement on remand.
Don’t over-rely on Funk Brothers analogies: Courts may resist product-of-nature framing where the claim requires engineered combinations that cannot arise naturally.
Life sciences portfolios: Patents tied to engineered vectors and host-cell systems may be more defensible on eligibility where the claims clearly require non-natural recombinant structures.
Litigation posture: Expect early § 101 motions, but this decision suggests plaintiffs have a strong response when claims are built around non-natural recombinant constructs.
The Federal Circuit returned the case to the District of Delaware for proceedings consistent with its opinion. The decision resolves the eligibility ruling under § 101 but does not decide infringement, remedies, or other potential validity challenges.
Court: U.S. Court of Appeals for the Federal Circuit
Date: February 20, 2026
Case name: Regenxbio Inc. v. Sarepta Therapeutics, Inc.
Docket number: 24-1408
Area of law: Patent infringement / patent eligibility (35 U.S.C. § 101)
Result: Reversed and remanded (summary judgment of ineligibility reversed)
1) What did the Federal Circuit decide in Regenxbio v. Sarepta?
The court reversed a Delaware district court’s summary judgment that the asserted claims were ineligible under § 101. It held the claims were not directed to a natural phenomenon and remanded.
2) Why did the district court rule against REGENXBIO under § 101?
The district court concluded the claims disclosed natural products and that combining them in a host cell did not make the invention patentable, relying in part on a Funk Brothers analogy.
3) Why did the Federal Circuit reject the Funk Brothers comparison?
The panel said the claims require a recombinant nucleic acid molecule and a heterologous sequence—human-made constructs that cannot exist in nature on their own—unlike simply mixing natural strains.
4) What role did “recombinant” and “heterologous” play in the decision?
The court treated those terms as key structural limitations showing the claimed nucleic acid is created by human intervention using sequences from different sources and species.
5) Does the remand mean REGENXBIO has won the case?
No. The ruling addresses eligibility under § 101 and returns the case to the district court; other disputes such as infringement and other validity issues remain open.
