The PTAB recently rejected a request for rehearing by Bayer CropScience LP (“Bayer”). Bayer Cropscience LP, v. Syngenta Limited, IPR2017-01332, Paper 15 (P.T.A.B. Apr. 2, 2018).[1] The PTAB stated that when the prior art does not identify the chemical structure of a compound that is only known by an experimental code name, post-filing evidence cannot be used to identify the compound and fill in any gaps in the prior art.

Bayer filed a petition requesting institution of inter partes review of U.S. Patent No. 8,404,618 (“the ’618 patent”), which is owned by Syngenta Limited (“Syngenta”). The ’618 patent is directed to a herbicidal composition for treating weeds, where the composition contains a herbicide and a safener that protects useful plants against the action of the herbicide.

Representative claims 1 and 9 are shown below:

1. A herbicidal composition comprises a mixture of

a) a herbicidally active amount of a compound [of a general formula that includes the compound pyroxasulfone] . . .


b) a herbicide-antagonistically active amount of a safener selected from [a genus of compounds].

9. The composition according to claim 1, wherein the compound of the formula I is 3-(5-difluoromethoxy-1-methyl-3-trifluoromethyl-1H-pyrazol-4-ylmethylsulf- onyl)-5,5-dimethyl-4,5-dihydroisoxazole.

The herbicide in claim 9 is also referred to as “pyroxasulfone.”

Bayer proposed 13 grounds for unpatentability, each of which applied the “Polge” and “Owen” references. Polge and Owen used an herbicide called “KIH-485” to control weeds. Relying upon an undated yet apparently post-filing date document to identify the structure of KIH-485, Bayer alleged that a skilled artisan would have recognized that KIH-485 was pyroxasulfone.

The PTAB disagreed with Bayer. Bayer Cropscience LP, v. Syngenta Limited, IPR2017-01332, Paper 10 (P.T.A.B. Apr. 2, 2018) (Decision Denying Institution). It found that while Polge and Owen used the nomenclature “KIH-485” to refer to a particular herbicide and applied that herbicide to control weeds, neither reference identified the chemical structure of formula of KIH-485. The PTAB called attention to a reference of record published around the time of the priority application, which stated “[t]he chemistry, fate and action, and biological information [of KIH-485] has not been released at this time” and to a declaration from Patent Owner noting that the experimental code name “KIH-485” “does not provide any information whatsoever about the chemical structure, chemical family, chemical common name, or mechanism of action of the experimental herbicide”. The PTAB agreed with Syngenta that a skilled artisan would not have understood or recognized that KIH-485 is the claimed pyroxasulfone herbicide before the priority date.

Bayer requested reconsideration, arguing that the PTAB’s decision was in conflict with established law on inherency. It argued that the PTAB “erroneously applied settled law regarding use of post-filing evidence to establish a fact or characteristic about a product in the prior art to support anticipation and nonobviousness” since “[t]here is no requirement that the chemical structure of a known prior art compound must be recognized to anticipate or render obvious later claims to the structure.”

The PTAB again disagreed with Bayer’s position and denied the rehearing request. In contrast to the cases cited by Bayer, the ’618 patent does not claim inherent properties or characteristics of a compound that was known or generally available to the public. It found that since the experimental code name did not provide information about the structure of formula of the compound, and since the code name could be applied to any chemical structure which could change over time, the disclosure of the code name “KIH-485” in Polge and Owen does not anticipate or render obvious the ’618 patent claims.