Toolgen’s Bid for Priority of Invention of CRISPR-Cas9 May Be Foiled by Prosecution History Statements

By Natalie Grace | October 4, 2022

In the ongoing battle for who originally invented the CRISPR-Cas9 genome editing technology, Toolgen’s prosecution history could potentially be its undoing for failing to constitute a reduction to practice.  During a recent Oral Hearing in Regents of the University of California v. Toolgen Inc., interference number 106,127, before the PTAB, counsel for the Junior Party CVC[i] argued prosecution admission and judicial estoppel based on statements made in characterizing the novelty of Toolgen’s claims in view of the cited art.  During prosecution of Toolgen’s U.S. Patent Application No. 14/685,510, Toolgen appealed the finding of obviousness by the examiner, explaining throughout the appeal, and in particular during oral hearing, that a “main distinction” of the claimed invention involves “both the nuclear localization signal and codon optimization.”[ii]


However, CVC counsel points to a lack of mention of codon optimization in the provisional having the earliest priority date from which the ‘510 application claims benefit, thus asserting that “because ToolGen’s application does not disclose the very thing it deemed critical for function, its application cannot serve as a constructive reduction to practice.”[iii]  Both parties concur that codon optimization, as a tool, was well known in the art during the time period relevant to the interference proceedings.


But, as ToolGen stressed in its appeal, the distinction lies in “whether one of ordinary skill in the art… would have had a reasonable expectation of success” in applying codon optimization in a eukaryotic/mammalian cell as claimed.[iv] Without going into the merits of CVC’s arguments or opining on their chance of success, this will be an interesting case to watch, especially having the CRISPR saga as a backdrop.


For now, CVC’s argument tactic stands as a stark reminder to patent prosecutors to carefully monitor priority document support in arguments presented in front of the USPTO and to consider, when drafting, the architecture or common processes supporting creation of the novel invention, such as well-known tools and procedures for preparing protein sequences.



[i] The Regents of the University of California, University of Vienna, and Emmanuelle Charpentier

[ii] Oral Hearing in Appeal 2019-001990 on March 2, 2022, p. 7 ll. 19-22.

[iii] Interference 106,127 CVC Motion 2 of May 20, 2021 at p. 2 ll. 6-14, citing in re Alonso, 545 F.3d 1015, 1021 (Fed. Cir. 2008).

[iv] ‘510 application Brief on Appeal of April 13, 2015 at p. 26.