REGENXBIO INC. v. SAREPTA THERAPEUTICS, INC.

Authored by: Jeremy J. Gustrowsky

The Federal Circuit reversed a district court decision that had invalidated claims of U.S. Patent No. 10,526,617 as patent-ineligible under 35 U.S.C. § 101. The patent, owned by REGENXBIO Inc. and the Trustees of the University of Pennsylvania, covers cultured host cells containing a recombinant nucleic acid molecule — a molecule created by splicing together genetic material from two different species. The case centered on whether these engineered cells were merely products of nature or something genuinely new and human-made.

Gene therapy works by using modified virus “vectors” to deliver a replacement gene into a patient’s cells, potentially treating or curing genetic disorders like cystic fibrosis or muscular dystrophy. The patent’s claims require a cultured host cell containing a recombinant nucleic acid molecule that encodes both a specific viral capsid protein (AAVrh.10) and a “heterologous” sequence — meaning a sequence from an entirely different species. REGENXBIO accused Sarepta Therapeutics of infringing these claims through Sarepta’s production of a gene therapy product for Duchenne muscular dystrophy.

The district court had sided with Sarepta, comparing the claimed host cells to the ineligible mixture of naturally occurring bacteria in the Supreme Court’s Funk Brothers decision, reasoning that combining natural sequences in a host cell was like mixing bacteria strains together. The Federal Circuit flatly rejected this analogy. The court explained that genetically engineering nucleic acid sequences from separate species into a single molecule and then transforming a host cell to incorporate that new molecule is “materially different” from simply growing naturally occurring bacteria together unchanged.

Instead, the Federal Circuit found the claims more like those upheld in Diamond v. Chakrabarty, where a genetically engineered bacterium capable of breaking down crude oil was deemed patent-eligible as a “nonnaturally occurring manufacture” with “markedly different characteristics” from anything in nature. The court emphasized that the recombinant nucleic acid molecule required by the claims — assembled from at least two different species through human intervention — cannot and does not exist in nature. The court also rejected Sarepta’s attempt to reframe the claims as merely directed to isolating a naturally occurring viral sequence, noting the claims plainly require much more, including a cultured host cell and heterologous sequences.

The Federal Circuit also declined Sarepta’s invitation to strip away “conventional” claim limitations and focus only on what was allegedly new, citing the Supreme Court’s longstanding instruction not to dissect claims into old and new elements during the eligibility analysis. While the court noted that other validity challenges like novelty or obviousness might still apply, those are separate inquiries from patent eligibility. The case was remanded to the district court for further proceedings.