Federal Circuit: Conventional Techniques Do Not Bar Patent Eligibility

In REGENXBIO v. Sarepta Therapeutics, the Federal Circuit recently held that a cell containing a non-naturally occurring recombinant nucleic acid molecule is not a product of nature and is patent‑eligible under 35 U.S.C. § 101, even though the recombinant molecule combines naturally occurring sequences and is incorporated into a cell by conventional technology. While REGENXBIO specifically relates to engineered biological products, it should have broader implications for addressing patent eligibility across all technologies.

The claim at issue of REGENXBIO’s U.S. Patent No. 10,526,617 reads:

1. 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.

It is undisputed by either party, in both the district court and on appeal, that the recombinant nucleic acid molecule, created by joining nucleic acid fragments from two different organisms, does not exist in nature. Likewise both parties agreed that the claimed host cell containing the recombinant nucleic acid molecule does not exist in nature.

In granting summary judgement, the district court found the claims ineligible, reasoning that the claimed compositions merely combine natural products and place them in a host cell without changing any individual component. Analogizing to the ineligible mixed bacterial cultures of Funk Brothers, the court held that combining two sequences from two different organisms is no different than mixing two bacterial strains.

However, the Federal Circuit unanimously reversed, holding that the claims are not directed to a natural phenomenon. The panel emphasized that the claims recite a single recombinant nucleic acid molecule created by joining nucleic acid fragments from different species and introduced into a host cell, thereby “fundamentally creating a cell containing a molecule that could not form in nature on its own” and thus “the claims here are not merely directed to repackaging products of nature.” Having found that the claimed host cells contain molecules markedly different from anything naturally occurring, the court explained it “need not reach the question whether they are markedly different based on unclaimed functions.” Even if considered, Chakrabarty permits looking to “the potential for significant utility,” and the claimed compositions are beneficial for gene delivery in a way their isolated constituents are not. The court also rejected attempts to disregard “conventional” claim elements in the relevant § 101 analysis, and reiterated that the claims must be assessed as a whole rather than by dissected non-conventional components.

Because the claims satisfied step one as not directed to a product of nature, the court did not reach step two of the Alice/Mayo framework.*

* Alice step one – determine whether the claims are directed to a patent-ineligible concept;
Alice step two – determine whether the claim’s elements, considered both individually and as an ordered combination, transform the nature of the claims into a patent-eligible application.

The following table summarizes how the Supreme Court and Federal Circuit have evaluated composition claims under § 101 in representative cases as referenced in the REGENXBIO decision:

Drafting Recommendations

• Claim non-natural structures and concrete actions. Define the structural transformations (e.g., “recombinant” nucleic acids, “heterologous” sequences, cellular transformation) that distinguish the claimed composition from natural counterparts. Claiming the engineered cell, not just the contained sequences, anchors eligibility in a composition that does not exist in nature. 
  • More broadly: For laws of nature, claim applied methods tying correlations to concrete actions (e.g., dosing regimens, device control, process adjustments) rather than mere observation. For abstract ideas, claim specific technical solutions with defined architectures, data structures, and algorithmic steps rather than results-only language or mental steps.
• Bolster specification support. Describe structural transformations. Define claim terms relied on for structural distinctness. Beyond structural differences, robustly disclose the functional and therapeutic advantages of engineered compositions to support the “markedly different characteristics” analysis even when not recited as claim limitations. 
  • More broadly: For laws of nature, disclose validated thresholds, protocols, decision rules, and outcome data showing real-world benefit beyond the correlation itself. For abstract ideas, provide architectures, algorithm detail, and performance benchmarks demonstrating technical improvement over generic implementation.

Prosecution and Litigation Recommendations

• Insist on whole-claim analysis. Cite REGENEXBIO for the principle that the claims must be evaluated as a whole, not parsed into allegedly natural (or abstract idea) subparts. The question should be whether the claimed composition as a whole exists in nature; whether the method as a whole applies the correlation; or whether the combination constitutes a specific technical solution.
• Reject conventionality attacks at Alice step one. The court refused to ignore claim features such as “recombinant” and “heterologous” merely because components recited in the claim may be conventional or found in the prior art. Routine techniques used to arrive at the subject matter of the claims do not bar eligibility at Alice step one.

Conclusion

In REGENXBIO, the Federal Circuit clarified patent eligibility of biological products by rejecting the excision of conventional elements at step one of the Alice analysis and requiring a holistic claim analysis. That reasoning may not be limited to biological compositions and should extend to other judicial exceptions, including abstract ideas and laws of nature. In parallel, the USPTO has implemented new tools to address eligibility, including its August 4, 2025 guidance for examiners on evaluating subject matter eligibility of claims, the Director’s In re Desjardins decision on September 26, 2025, and introduction of the term Subject Matter Eligibility Declaration (SMED) in the December 4, 2025 memoranda, all reflecting a broader trend of promoting patent eligibility. Although the Patent Eligibility Restoration Act of 2025 was reintroduced in both chambers on May 1, 2025, its prospects remain uncertain. In the meantime, the USPTO’s evidentiary pathways and the Federal Circuit’s REGENXBIO framework provide concrete administrative and judicial routes to secure protection, especially where claims recite non-natural features or concrete technological improvements.