Federal Circuit Affirms PTAB Ruling That Pioneer's Herbicide-Degrading Enzyme Claims Are Not Enabled.

In a nonprecedential opinion issued October 2, 2026, the Federal Circuit affirmed a Patent Trial and Appeal Board decision in post-grant review PGR2023-00022 that claims 1 through 33 of Pioneer Hi-Bred International's U.S. Patent 11,371,055 are unpatentable for lack of enablement. The court held that the Board could rely on Pioneer's own test data generated after the priority date. Inari Agriculture brought the challenge.

The claims

The '055 patent, titled Herbicide Resistance Genes, describes enzymes that the parties say have a dual herbicide-degrading function: they make crops resistant to two classes of herbicides, pyridyloxyacetate auxins such as triclopyr and fluroxypyr, and phenoxy auxins such as 2,4-D. As the opinion describes it, representative claim 1 defines the claimed genus by function and structure. Its preamble recites activity that enzymatically degrades a phenoxy auxin herbicide and a pyridyloxy auxin herbicide, and its body requires at least 85% sequence identity with SEQ ID NO: 2 and an AAD-12 motif.

The record

Inari argued that the claimed genus was "unfathomably large." The opinion describes a genus of more than 10 to the 106th power species, which Inari said exceeds the number of atoms in the universe, and says that even with the guidance in the patent's Figure 2 the genus would still include about 1.23 times 10 to the 66th power species. Pioneer did not dispute those numbers. The specification gives two example species. With its patent owner response, Pioneer submitted experiments, performed more than a decade after the priority date, testing eight enzymes that met the claimed structural limitations. Only two showed the dual function, and the opinion says they did so "weakly at that," with 1% and 2% triclopyr activity.

The holding

On appeal, Pioneer argued that enablement must be judged as of the priority date, so the Board erred by relying on post-priority data. The panel of Judges Dyk, Prost, and Cunningham, in an opinion by Judge Prost, said the argument appeared forfeited because Pioneer did not raise it before the Board, and rejected it anyway. Relying on Amgen Inc. v. Sanofi, 872 F.3d 1367 (Fed. Cir. 2017), the court distinguished In re Hogan and In re Entresto, which rejected reliance on later-developed technology, because "all tested variants of the claimed genus could have been created at the time of the priority date, although they were tested by Pioneer afterward."

The court also found no abuse of discretion in the Board's reliance on Inari's expert, and held that substantial evidence supports the Board's finding that the specification and working examples "fail to provide guideposts that would have illuminated a path toward embodiments at the 85% sequence identity level." It noted that two tested variants differing by only six amino acids, none in positions Figure 2 marked as presumptively important, split on the claimed function. The Board's analysis, the court said, was rooted in the Supreme Court's statement in Amgen Inc. v. Sanofi (2023) that "[t]he more one claims, the more one must enable."

Context

Pioneer is one of the plaintiffs in Corteva Agriscience LLC v. Inari Agriculture, Inc., No. 1:23-cv-01059 (D. Del.), the seed patent case that settled during trial and was dismissed with prejudice on September 28, 2026. The '055 patent was not among the patents asserted in that case. This decision is nonprecedential.

What to watch next

Watch for any petition for rehearing and for the mandate. If the decision stands, 35 U.S.C. 328(b) directs the Director to issue a certificate canceling the claims found unpatentable once any appeal has terminated.

Cite this page: https://patentlitigator.com/analysis/pioneer-v-inari-pgr-enablement/