Key Takeaways:

• Federal Circuit Reopens CRISPR-Cas9 Priority Fight. The CAFC vacated the PTAB’s earlier ruling that UC lacked prior conception of CRISPR-Cas9 in eukaryotic cells, remanding the interference for reconsideration without reliance on the researchers’ subjective doubts.  The court affirmed that UC’s earliest provisional filings do not satisfy the §112 written description requirement for a functional eukaryotic CRISPR system. 
• New CRISPR-Cas9 Legal Developments Highlight Best Practices for Innovators and Patent Drafters. Innovators are encouraged to maintain contemporaneous, corroborated conception and diligence documentation, while patent drafters should seek to include pertinent disclosures - such as experimental designs, functional rationales and, ideally, proof-of-concept data - to help withstand written description challenges.
• CRISPR Gene Editing Advances Clinically as Next-Gen Editors Emerge. Alongside ongoing patent disputes, base and prime editing achieved significant clinical milestones, demonstrating the transformative potential of precision gene-editing therapies. Meanwhile, new genome engineering tools like evoCAST and bridge recombinases are pushing technological boundaries and broadening both the competitive and IP landscape beyond Cas9.

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The past week was a truly remarkable week for the CRISPR gene editing field.  New developments have reshaped both the legal and scientific landscapes for CRISPR and next-generation gene-editing technologies. A pivotal Federal Circuit ruling reopened the foundational UC–Broad CRISPR/Cas9 priority contest, while base- and prime-editing platforms clinched clinical milestones at unprecedented speed. Additionally, newer generations of gene editing technologies (evoCAST and bridge recombinases) came on the stage. We summarize below these significant developments and the practical implications for the gene-editing space.

1. Federal Circuit Revives the UC–Broad Interference²

• Conception Reconsidered. In a May 2025 opinion, the Court of Appeals for the Federal Circuit (CAFC) vacated the Patent Trial and Appeal Board’s (PTAB) prior determination that the University of California lacked conception of CRISPR-Cas9 editing in eukaryotic cells before the Broad Institute. The court held that the PTAB placed undue weight on cautionary language by UC scientists and under-credited corroborating evidence that the UC scientists had formed a definite and permanent idea. As a result, the interference has been remanded for a fresh evaluation of which party first conceived the invention.

The CAFC reiterated that conception is a legal determination based on whether the inventor formed a definite and permanent idea of the invention. Moreover, an inventor need not know that his invention will work for conception to be complete. According to the court, the key question was whether UC scientists had formed the idea of the invention’s use for its intended purpose in sufficiently final form that only the exercise of ordinary skill remained to reduce it to practice without extensive research or experimentation. The court went further to clarify that inventor doubts or general scientific uncertainty does not automatically negate conception, as long as the surrounding evidence — including experimental plans, communications and third-party corroboration — supports a complete idea.

• Written Description Deficiency Affirmed. Although UC won a reprieve on conception, the CAFC simultaneously affirmed that UC’s earliest two provisional applications do not provide written description support for the claims on appeal because they did not establish that the inventors possessed a functioning eukaryotic CRISPR-Cas9 system. Those provisional filings therefore cannot supply an early constructive reduction to practice, placing heightened importance on actual laboratory success and diligence records in the remanded proceeding. 

The court sided with the PTAB, holding that UC’s earliest provisional applications still fall short of the written description requirement. It clarified that the PTAB did not force UC to “convince” a person of ordinary skill in the art that its system would work; rather, it correctly evaluated the record under settled written description law. Although a patent need not always include working examples or an actual reduction to practice, greater detail may be required when the science is both complex and unpredictable—as was true for a eukaryotic CRISPR-Cas9 system at that time. In 2012 a skilled researcher would have understood the complexities and the unpredictable nature of adapting prokaryotic systems to eukaryotic cells, yet UC’s filings offered no specific conditions for achieving CRISPR activity in eukaryotes, nor any indication that special conditions were unnecessary. Consequently, a person of ordinary skill would not have believed the UC scientists actually possessed a functional eukaryotic system.

• What to Watch Next at the Patent Office? With the CAFC vacating the PTAB’s prior finding on conception, the interference proceeding is now poised for a renewed phase — and potentially a pivotal shift in the priority contest.  Both Broad and UC may request panel and/or en banc rehearing. If and once the PTAB regains jurisdiction over the interference, here are some key areas to track. 

• Reevaluation of Conception Based on the Full Evidentiary Record. The PTAB will need to reassess whether UC had a complete conception of CRISPR-Cas9 in eukaryotes before Broad — this time without relying on the inventors’ subjective doubts or caution. 
• Diligence Inquiry May Become Central Again. If the PTAB ultimately finds that UC conceived of the invention before Broad but reduced it to practice later, then the question becomes whether UC exercised reasonable diligence in reducing the invention to practice.
• Impact of the Written Description Affirmation. Because the CAFC affirmed that UC’s earliest provisional filings fail to provide written description support, those applications cannot serve as UC’s constructive reduction to practice. This makes actual lab success — and its timing — even more pivotal.
• PTA Implication from Interference and the Cellect Trap. Unless the parties settle, the conception remand may extend the interference for years, generating potential patent term adjustment (PTA) for the eventual winner party (especially for UC’s pending applications). However, this potential PTA windfall can also simultaneously increase obviousness-type double-patenting (ODP) exposure under In re Cellect (Fed. Cir. 2023). It will be interesting to see how the parties balance their potential PTAs and terminal disclaimers, as extra PTA will not in each instance durably enhance long-term patent exclusivity. 

2. Practice and Strategy Pointers

• Fortify Objective Conception Records. Even though AIA patent cases are no longer subject to interference proceedings, determining conception remains relevant in inventorship assessment, especially during research collaborations. To establish conception, inventors’ best practice can include articulating in real time working hypotheses and documenting experimental planning and development timelines. Cautionary language alone will not defeat conception.

• Draft for Written Description, Not Merely Enablement. The mere filing of a provisional application does not constitute constructive reduction to practice unless such application satisfies Section 112, i.e., meeting both enablement and written description requirements. For unpredictable art such as biotech, including detailed experimental designs, functional rationales, and preferably proof-of-concept data can help demonstrate possession of the claimed subject matter. Generic statements of potential utility, without more, may not suffice. 

• (Re-)Assess Licensing Strategies and Leverage Alternatives. The latest twist in the CRISPR/Cas9 interference may shift the CRISPR licensing landscape. It is logical that certain existing or potential Cas9 licensees will take into account this latest development and any legal uncertainty therefrom. The renewed Cas9 patent uncertainty and licensing complexity may also give non-Cas9 nuclease developers an opportunity to position themselves as alternatives with IP simplicity.

3. Clinical and Technology Breakthroughs Driving the Next Wave of Gene Editing

• Fastest In-Human Base Editing in Baby KJ. Published last week, clinicians treated an eight-month-old patient (“Baby KJ”) using a bespoke in vivo adenine base editor designed, manufactured and dosed in under eight months. The episode demonstrates the maturing translational pipeline for precision editors and underscores how rapidly personalized therapies can now be deployed.
 
• Prime Editing Enters the Clinic. Initially reported last week, and officially announced this week, was the initial clinical administration of a prime-editing therapy to a chronic granulomatous disease (CGD) patient. By inserting two missing DNA bases without creating double-strand breaks, prime editing offers expanded edit scope with potentially improved safety. 

• EvoCAST and Bridge Recombinases. Besides the clinical milestones, researchers also reported last week (i) a laboratory-evolved CRISPR-associated transposase (evoCAST) achieving greater than 200-fold increases in targeted gene-length insertions and (ii) engineered bridge recombinases³ capable of megabase-scale genomic rearrangements. These tools signal a widening IP horizon beyond Cas9, implicating fresh filing races over delivery vectors, editing architectures and combinatorial approaches. 

4. Looking Ahead
The UC–Broad contest now turns on a more coordinated evidentiary review of conception and diligence, while multiple clinical successes are propelling newer editors toward wider patient access and their own potential IP skirmishes down the road. Taken together, these events confirm that gene-editing IP is entering a more complex, multi-platform phase. Innovators need to document innovations with rigor, draft patents with granularity, and license IP with flexibility to maintain secure positions in this rapidly evolving field. 

Please contact us to discuss how these developments may affect your ongoing research programs, patent strategy or transaction planning. 
 

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¹The contributors also appreciate assistance from Vince Nunez on this advisory.
²The interference has two opposing sides: the University of California/Berkeley, the University of Vienna, and Emmanuelle Charpentier (collectively “CVC” before the PTAB, here, “UC”); and the Broad Institute, Harvard University, and MIT (collectively, “Broad”).
³Mechanistically, bridge recombinases differ from, and do not depend on, CRISPR.